1. OXYGEN
QUESTIONS
1: Multiple choice.
Choose the most correct answer from the given alternatives.
(i) Which of the following compounds is not likely to contain Oxygen?
A: water
B: Copper oxide
C: ammonia
D: carbonate
(ii) Oxygen supports combustion and it is not used in ________
A: welding
B: respiration
C: incineration
D: extinguishing fire
(iii) Oxygen gas found in the atmosphere because
A: it is a gas
B: it is useful
C: it is denser
D: it is lighter
(iv) Oxygen gas forms water with_______ gas.
A: nitrogen
B: hydrogen
C: carbon dioxide
D: sulphur
(v) ________ is a removal of oxygen from the substance.
A: oxidation
B: reduction
C: redox
D: No answer
(vi) _________ observed when a wooden glowing splint placed in a tool in which hydrogen is contained.
A: yellow colour
B: green colour
C: explosion with pop sound
D: light
(vii) When it is mixed with oxygen a very hot flame is produced.
A: hydrogen gas
B: chlorine gas
C: neon
D: argon
(viii) Which of the following can not be used to prepare oxygen gas?
A: potassium chlorate
B: any compound rich in oxygen
C: electrolysis concentrated sulphuric acid
D: hydrogen peroxide
(ix) The following statement is not true about oxygen.
A: it is used to manufacture ammonia with nitrogen.
B: it burns fuels
C: it is colourless
D: it supports combustion.
(x) The common industrial method of preparing oxygen.
A: electrolysis of copper sulphate
B: electrolysis of bases
C: decomposition of hydrogen peroxide
D: fractional distillation of liquefied air.
- Matching items.
Match items in list A with responses in list B.
List A
(i) Percentage of oxygen in air we breath
(ii) chemical property of oxygen
(iii) physical property of oxygen
(iv) the property of oxygen to be less denser than air.
(v) Reason for hydrogen to be used in rocket.
List B
A: it oxidises fuel.
B: Tasteless
C: forming metallic oxides
D: it collected over water.
E: 79%
F: used in rockets.
G: 21%
- Write T for the correct statement and F for incorrect statement.
(i) Oxidation is the addition of oxygen to the substance.
(ii) reduction is removal of oxygen from the substance.
(iii) Oxygen forms basic oxides with non-metals
(iv) Oxygen form acidic oxides with metals
(v) Hydrochloric acid is used to prepare oxygen in the laboratory.
- List down uses of oxygen
- (a) State the substance which used to test oxygen.
(b) Explain how we can identify the presence of oxygen?
- State apparatus used in laboratory preparation of oxygen and their uses.
- Mention:-
(a) chemical properties of oxygen
(b) physical properties of oxygen
- Explain why hydrogen collected by downward displacement of water when preparing it in the laboratory?
- Describe
(a) industrial manufacture of oxygen.
(b) i) laboratory preparation of oxygen by using hydrogen peroxide.
- ii) State the function of the manganese IV oxide during preparation of oxygen by using hydrogen peroxide.
- Give the definitions of oxidation and reduction.
ANSWERS.
- (i) C vi) D
(ii) D vii) A
(iii) C viii) C
(iv) B ix) A
(v) B x) D
- (i) G (ii) C (iii) B (iv) D (v)A
- (i) T (ii) T (iii) F (iv) F (v) F
- Uses of oxygen.
-it used in respiration process
-it is used in pulp and paper making
-it is used in metal cutting
-it is used as fuel oxidiser in rockets
-it is used in hospital for people with breathing problem.
-it used in glass making
-it is used in treatment of sewage plants.
-it used to manufacture synthetic fuels
-it is used to manufacture chemicals. For example acids and oxides.
- (a) Chemical test for oxygen is a glowing wooden splint.
(b)oxygen identified is a glowing wooden splint relights when it is lowered into a gas jar of oxygen gas.
6.The following are apparatus used to set the system of preparing hydrogen in the laboratory.
(a) Thistle/dropping funnel
Is used to transfer acidic solution into the flat bottomed flask.
(b) Flat bottomed flask
Is used to mix acidic solution(hydrochloric acid) with zinc granules.
(c) Delivery tube
Is used to transfer hydrogen into beehive stand.
(d) Beehive stand
Is used to connect delivery tube with gas jar.
(e) Gas jar
Is used to collect hydrogen gas
(f) Trough
Is used to hold water.
- (a)Chemical Properties of Oxygen
(i) It supports burning.
(ii) It is an oxidising agent.
(iii) It reacts with metals to form basic oxides.
(iv) It reacts with non- Metal to form acidic oxides.
(a) Physical Properties of Oxygen
(i) Oxygen is colourless, tasteless and odourless.
(ii) It is slightly dissolves in cold water.
(iii) It is less denser than air.
(iv) It boils at -1830°C.
(v) It freezes at – 2180°C
- Hydrogen is collected by downward displacement of water because it is less denser than air.
- (a) Industrial preparation of oxygen is manufactured by fractional distillation of liquefied air after water and dust being removed. Where by different gases that forms air are separated.
-carbon dioxide liquefies at -79°C. At this point it removed from the mixture in which nitrogen and oxygen remained.
-nitrogen liquefies at -196°C and oxygen liquefies at -183°C. In order to obtain liquefied oxygen the mixture boiled then nitrogen boils and rise to the top where it is piped off. The liquid oxygen collected.
(b) (i) Oxygen is mostly prepared in the laboratory by using hydrogen peroxide in presence of manganese oxide.
Hydrogen peroxide decomposed to form water and oxygen then oxygen collected in the gas jar.
(ii) The function of manganese oxide is to speed up the rate of the reaction(decomposition of hydrogen peroxide) because it is used as a catalyst.
- •Oxidation refers to:-
-the process of adding oxygen to the substance.
-the process of removing hydrogen from the substance.
-the process of removing electron from the substance.
-the process of increasing oxidation number.
- Reduction refers to:-
-the process of adding hydrogen to the substance.
-the process of removing oxygen from the substance.
-the process of adding electron to the substance.
-the process of decreasing in oxidation number.
NB:
>Redox reaction:- is the reaction in which both reduction and oxidation are taking place.
>Oxidizing agent:- is a substance that influence or its presence makes oxidation to take place.
>Reducing agent:- is substance that influence or its presence makes reduction to take place.
2. HYDROGEN
QUESTIONS
1: Multiple choice.
Choose the most correct answer from the given alternatives.
(i) Which of the following compounds is not likely to contain hydrogen?
A: water
B: Copper oxide
C: ammonia
D: water gas
(ii) Hydrogen does not support combustion but it is used as ________
A: water gas fuel
B: respiratory gas
C: oxidant
D: fire extinguisher
(iii) Hydrogen gas is used to fill weather balloons because
A: it is a gas
B: it is heavier
C: it is abundant
D: it is lighter
(iv) Hydrogen gas forms ammonia with_______ gas.
A: nitrogen
B: Oxygen
C: carbon dioxide
D: sulphur
(v) ________ and _______ reacts slowly to produce water.
A: oxygen and helium
B: hydrogen and helium
C: hydrogen and oxygen
D: No answer
(vi) _________ observed when a wooden glowing splint placed in a tool in which hydrogen is contained.
A: yellow colour
B: green colour
C: explosion with pop sound
D: clacking sound.
(vii) When it is mixed with hydrogen a very hot flame is produced.
A: oxygen gas
B: chlorine gas
C: neon
D: argon
(viii) Which of the following can not be used to prepare hydrogen gas?
A: reaction of water with carbon at room temperature.
B: reaction of dilute acid with zinc
C: electrolysis of water
D: reaction of water with certain metals
(ix) The following statement is not true about hydrogen.
A: it is lighter than air
B: it burns with blue flame
C: it is colourless
D: it supports combustion.
(x) The common industrial method of preparing hydrogen.
A: electrolysis of copper sulphate
B: electrolysis of bases
C: decomposition of hydrogen peroxide
D: electrolysis of water.
- Matching items.
Match items in list A with responses in list B.
List A
(i) water gas fuel
(ii) chemical property of hydrogen
(iii) physical property of hydrogen
(iv) the property of hydrogen to have less denser than air
(v) Reason for hydrogen to be used in production of fuel
List B
A: is reason for it to be filled in weather balloons.
B: Tasteless
C: flammability
D: pop sound
E: reacting with other substances at high temperature.
F: used in rockets.
- Write T for the correct statement and F for incorrect statement.
(i) Oxidation is the addition of hydrogen to the substance.
(ii) reduction is removal of hydrogen from the substance.
(iii) Hydrogen reacts with chlorine to produce hydrochloric acid.
(iv) Hydrogen is most abundant gas on the earth.
(v) Hydrogen made under the process known as Haber process.
- List down uses of hydrogen
- (a) State the substance which used to test hydrogen.
(b) Explain how we can identify the presence of hydrogen?
- State apparatus used in laboratory preparation of hydrogen and their uses.
- Mention:-
(a) chemical properties of hydrogen
(b) physical properties of hydrogen
- Explain why hydrogen:-
(a) collected by downward displacement of water?
(b) is not found in the atmosphere?
- Describe two methods for industrial manufacture of hydrogen.
ANSWERS
- (i) B (vi) C
(ii) A (vii) A
(iii) D (viii) A
(iv) A (ix) D
(v) C (x) D
- (i) F (ii) E (iii) B (iv) A (v) C
- (i) F
(ii) F
(iii) T
(iv) F
(v) F
- Uses of hydrogen include the following.
(i) Hydrogen is used in the synthesis(production) of ammonia.
This is done on large scale through the
laboratory process.
(ii) Hydrogen is used in the Manufacture of margarine.
(iii) Hydrogen is used to produce oxy-hydrogen flame.
This flame can be used for welding and cutting metal.
(iv) it is used to make fuel since it is highly flammable.
- (a) The substance used to test hydrogen is wooden glowing splint.
(b) Hydrogen identified if explosion with a pop sound observed when the gas come into contact with a wooden glowing splint.
- The following are apparatus used to set the system of preparing hydrogen in the laboratory.
(a) Thistle funnel
Is used to transfer acidic solution into the flat bottomed flask.
(b) Flat bottomed flask
Is used to mix acidic solution(hydrochloric acid) with zinc granules.
(c) Delivery tube
Is used to transfer hydrogen into beehive stand.
(d) Beehive stand
Is used to connect delivery tube with gas jar.
(e) Gas jar
Is used to collect hydrogen gas
(f) Trough
Is used to hold water.
- (a) chemical properties of hydrogen include the following.
(i) It combine easily with other chemicals substance at high temperature.
(ii) It does not usually react with other element at room temperature.
(iii) It is highly flammable and burns with a blue of flame.
(iv) It reacts slowly with oxygen to produce water.
(v) It is neither acidic nor basic
(b) Physical Properties of Hydrogen
(i) It is tasteless, colourless and odourless.
(iii) It is lighter than air, Therefore it is in the atmosphere.
(iii) It is only slightly soluble in water.
(iv) It does not support combustion.
8.(a) hydrogen is collected by downward displacement of water because it is slightly soluble in water.
(b) hydrogen is not found in the atmosphere because it is lighter such that it found above the atmosphere.
- Industrial methods of manufacturing hydrogen include the following.
(i) Electrolysis of water
(ii) Electrolysis of dilute sulphuric acid.
Electrolysis of water.
Electricity used to decompose water into hydrogen and oxygen. In this process hydrogen collected as gas at the cathode.
Electrolysis of dilute sulphuric acid.
Electricity decomposes sulphuric acid into hydrogen and sulphate.
3. WATER.
QUESTIONS
- Multiple choice.
Choose the most correct answer from the given alternatives.
(i) The system where water is being recycled
A: water movement.
B: water system
C: hydro-logical cycle
D: water treatment.
(ii) Formation of liquid water from ice is under the process known as ______
A: melting
B: condensation
C: evaporation
D: precipitation
(iii) _________ water generate hydro electric power.
A: cold B: moving C: hot D: atmospheric.
(iv) Usable water obtained after being _________
A: Purified
B: boiled
C: filtered
D:.treated
(v) One of the following is not physical properties of water.
A: it is colourless, odourless and tasteless
B: it is neither acidic nor basic.
C: it is a universal solvent
D: it freezes at 0°C and boils at 100°C
(vi) We get pure water after________
A: being boiled
B: removal of contaminants
C: being filtered
D: removing mud and dust.
(vii) Which of the following statement about water is not true?
A: is used in industries as coolant
B: is used as raw material to produce hydrogen to produce carbon
C: is used as solvent
D: is used as raw material to produce hydrogen gas
(viii) The simplest way to purify water at home.
A: cooling
B: boiling
C: filtering
D: condensing
(ix) During precipitation, water falls in form of.
A: rain and clouds
B: rain, snow and hail
C: water ice
D: vapour
(x) The process of removing contaminants from water is called_________
A: water purification
B: sedimentation
C: electrolysis
D: contamination
- Matching items.
Choose the correct response from list B that match with item in list A.
List A.
(i) liquid state of water
(ii) solid state of water
(iii) gaseous state of water
(iv) uses of water in agriculture
(v) combination of acidic gases and water vapour.
(vi) using untreated water
(vii) reaction of water and metals to form hydroxides and hydrogen gas.
(viii) Boiling
(ix) swimming
(x) cooling machine.
List B
A: chemical property of water.
B: simple domestic water treatment.
C: may cause eruption and spread of diseases
D: ice, snow and hail.
E: clouds, mist and steam.
F: dew and rain
G: use of water in recreation.
H: lead to occurrence of acidic rain.
I: irrigation.
J: industrial use of water.
- Why water is said to be a universal solvent?
- How can we test the presence of water in a substance?
- Define the following terms.
(i) water treatment
(ii) precipitation
(iii) evaporation
(iv) condensation
(v) water purification
(vi) solubility
(vii) melting
- (a) Explain the methods of domestic treatment of water
(b) Explain the process of urban treatment of water
- List down uses of water.
- Differentiate water treatment from water purification.
- (a)What are the importance of treating water?
(b) What are the importance using treated water?
- Analyse physical properties and chemical properties of water.
- (a) define water cycle
(b) explain processes involved in a water cycle.
ANSWERS.
- (i).C vi) B
(ii) A vii) B
(iii) B viii) B
(iv) D ix) B
(v) B x) A
- (i) F vi) C
(ii) D vii) A
(iii) E viii) B
(iv) I ix) G
(v) H x) J
- Water is said to be a universal solvent because many substances dissolved in it if compared to other solvents.
- We can identify presence of water by using the following specific tests.
- i) Blue Cobalt chloride vapour.
-Water or its vapour will turn cobalt chloride paper from blue to pink.
- ii) Anhydrous copper(II) sulphate
Water or its vapour turns
anhydrous copper(II) sulfatecrystals from white to blue.
- (i) Water treatment
is a process of making unusable water into usable.
(ii) Precipitation
Is a process in which water fall to the earth in forms of rain, hail or snow.
(iii) Evaporation
Is a process where by the water vapour or steam leaves the streams, rivers, lakes or oceans into the air.
(iv) Condensation
Is a process in which water vapour in air get cold and change into liquid that form clouds.
(v) Water purification
is a process of removing contaminants from treated water.
(vi) Solubility
Is a tendency of substances (solutes) to dissolve to form solutions.
(vii) Melting
Is a process of changing from solid substance into liquid substance.
- (a) methods of treating domestic water include the following
(i) Boiling.
Is a process of heating water and let it to boil at least five minutes before heating is stopped.
(ii) Use of purifiers.
Is a method of treating water where by chemical water purifiers are added in water.
Water purifiers are in forms of liquid or tablet.
(iii) Use of commercial filters.
Is a method of water treatment in which water pass through a charcoal or ceramic element that purifies water.
(b) the following summary explains Urban water treatment.
Tap water used in urban is usual obtained from sources such as rivers, stream and lakes
which are not treated. Processes for treatment of urban water are explained as follows
- Screening
- Reservoirs
iii. Primary filtration
- Secondary filtration
- Disinfection/chlorination
- Storage
- Screening
This process involves the removing of floats substance
- Reservoirs
This process involves the storing of water at high up so it flows through gravitation
- Primary filtration
This process involves
- Filtered water comes from reservoir
through coarse sand (filter medium) to remove particles
- Addition of aluminium sulphate to water comes from reservoir to remove smaller particles which was not filtered at coarse sand
- Secondary filtration
This process involves Filtered water comes from primary filtration through finer sand (filter medium) to remove smallest particles
- Disinfection/chlorination
This process involves put Disinfection to water comes from secondary filtration to kill harmful bacteria
- Storage
This process involves to store soft water (comes from Disinfection/chlorination) ready for use
- Uses of water.
-it used for drinking
-it used for cooling
-it used for cleaning.
For. Example environment
-it used for washing. Eg bodies
-it used to manufacture goods
For. Example food and chemicals
-it used for agriculture activities
For example irrigation.
-it used to generate hydro electric power.
-it used in construction. Eg. Roads
-it used as a solvent.
-it used in transportation.
- Water treatment is a process of making unusable water into usable.
While
Water purification is a process of removing contaminants from treated water.
There fore when treating water we get useful water but when purifying water we get pure water.
- The following are importance of water treatment.
(i) it helps to remove harmful bacterial and other parasites which may cause diseases.
(ii) it enables us to get efficient water for different uses. Eg cleaning
(iii) it helps to get suitable water for manufacturing products which are safe for consuption.
(iv) it helps us to get water which is best for laboratory uses and medical facilities.
(b) Importance of using treated water.
(i) it helps to avoid infections and spread of diseases.
(ii) it provides correct result when performing experiments in the laboratory
(iii) it provides safe products for human consuptio when it is used in manufacturing industries.
(iv) it simplifies cleaning and maintains the quality cleaned substance.
- Physical properties of water
- It is colourless, odourless and tasteless
- Occurs natural in all state of mater
iii. It is universal solvent
- Freezing point is 0 ℃
- Its boiling point is 100 ℃
- It has high surface tension
vii. It has high specific heat index
viii. It expands when freezes thus why ice float
over water
- It is miscible with many liquids
Chemical properties of water
- Pure water is neutral (neither acidic nor
basic)
- Cold water react with some metals to
form hydroxide and liberate hydrogen gas
iii. Some metals react with steam to give
respective metal oxide and hydrogen gas
11.
(b)Water Cycle stages
Water cycle is made up to four main stages which are
- Evaporation (include transpiration)
- Condensation
iii. Precipitation
iv.Collection
Evaporation (include transpiration)
Water from rivers, lakes, stream, sea, ponds etc evaporate to air.
Plants lose water in form of vapour by
transpiration while animal and human being lose water through respiration and
sweating
Condensation
Water vapour obtained by evaporation,
transpiration, perspiration and sweating in the air gets cold and changes back into liquid to form clouds
Precipitation
Rain start when air fails to hold condensed
water and final results rain
Collection
Takes place when rain water back to the
ground which may run over the soil and
collected in the rivers, lakes, stream, sea, ponds where cycle stars all over again.
4. FUELS AND ENERGY
QUESTIONS
- Choose the most correct answer from the alternative given.
(i) Energy that does not replaced within short period of time.
A: Solar energy B: Renewable energy C: Non-renewable energy D: Hydro electric power.
(ii) Is formed as a result of fermentation of dead organic matter
A: Hydro electric power.
B: Solar energy
C: Heat energy
D: Bio gas
(iii) Radiant energy from the star.
A: Wind energy
B: Solar energy
C: Light energy
D: Heat enegy
(iv) The ratio between energy produced to the mass of fuel used.
A: Energy efficient
B: Energy value
C: Fuel efficient
D: Fuel value
(v) An example of natural fuel.
A: Coal B: Kerosene C: Paper D: Plastic
(vi) Is a fuel that exists as solid subsance.
A: Coal B: Petrol C: Water gas D: Gas producer.
(vii) A good fuel must have _________ ignition point.
A: Low B: Rapid C: Average D: High
(viii) _______ is a fuel which made from woody materials.
A: Coal B: Charcoal C: Gas D: Petrol
(ix) The energy that possessed by the body due to its motion.
A: Kinetic energy
B: Potential energy
C: Mechanical energy
D: Chemical energy
(x) _________ is an example of potential energy.
A: Thermal energy
B: Electrical energy
C: Chemical energy
D: Sound energy
- Match items in list A with responses in list B
List A
(i) The temperature that reached to burn fuel.
(ii) Used for cooking, boiling and ironing
(iii) Used for running industrial plants, cars, planes and ships.
(iv) The source of all energy on the earth
(v) Artificial fuels
(vi) Natural fuels
(vii) Gaseous fuels
(viii) Convert solar energy into heat energy.
(ix) Energy transformation.
(x) Energy conservation.
List B
A: kerosene,petrol and diesel
B: solar energy and wind energy
C: nuclear energy, natural gas, kerosene and coal.
D: changing mechanical energy into electrical energy.
E: kerosene, charcoal and natural gas.
F: Ignition point
G: wood, charcoal and coal
F: Maintaining energy such that it is not lost.
H: Solar cooker
I: Sun
J: water gas and bio gas
K: Petrol and diesel
L: Wood, coal and natural gas
- Outline ways of harvesting solar energy.
- Mention three components of coal.
- What are the environmental effects of using firewood and charcoal as fuels?
- List down the qualities of good charcoal.
7.(i)Define the following terms.
(a) Fuel
(b) Energy
(c) Bio gas
(d) renewable energy
(e) non-renewable energy
(ii) Mention examples of renewable energy resources and non-renewable energy resources.
- (a) State the principle of conservation of energy.
(b) Explain the forms in which energy exists.
- Classify fuels according to:-
(a) physical state
(b) occurrence.
- Mention the factors that considered when choosing a good(efficient) fuel.
- What are the uses of fuels?
ANSWERS.
- (i) C vi) A
(ii) D vii) C
(iii) B viii) B
(iv) B ix) A
(v) A x) C
- (i) F vi) L
(ii) G vii) J
(iii) K viii) H
(iv) I ix) D
(v) A x) F
- Ways used to tap/harvest solar energy
- Using photovoltaic for generating electricity (photoelectric solar cells)
- Using concentrated
solar power for generating electricity
iii.Using parabolic
mirror that focus the suns to a central
position for heating and cooking.
- Using solar chimney for heating and cooling.
NB:
The energy from the sun is the sources of all energy on the earth
- Components of coal include.
-moisture
-volatile matter
– ash
-coke
- Environmental effects on using charcoal and
firewood
Uses of charcoal and firewood cause
- Deforestation (cutting down tree)
- Drought
iii. Floods
iv.Disease
Deforestation
Cutting down tree cause land unprotected
from soil erosion
Drought
Deforestation result disturb water cycle
which can cause drought and final famine
Floods
Increase in carbon dioxide tend to increase
global warming which results high
temperature than normal which can cause
rains or melts ice in ice lands and final floods
Disease
Flood always water may contaminate and
when people uses can affected and final
cause disease.
- The following are qualities of good charcoal.
-It should be porous
-It should be brittle
-It should retain the woody shape
- (i) (a) Fuel.
Is any combustible substance that when burn produces energy.
NB.
The energy produces is in forms of heat and light.
(b) Energy
Is the ability of the body or system to do work.
(c) Bio gas
is a gaseous fuel, especially
methane, produced by the fermentation of organic matter.
(d) Renewable energy
Is the energy which is continuously being replaced within short period of time.
(e) Non-renewable energy
Is the energy which is continuously cannot replaced within short period of time.
(ii) -Examples of renewable energy resources are
- solar energy
- wind energy
-Examples of non-renewable energy resources are
- wood
- kerosene
- gas
- petrol
- (a) Principle of conservation of energy states that “Energy can neither be created nor destroyed but it can be changed from one form to another”
(b) Forms in which energy exists.
Energy exists in two forms which are.
(i)Potential energy.
This is the energy in matter due to its position. For example Chemical energy and elastic potential energy.
(ii) Kinetic energy.
This is the energy in matter due to its motion. For example sound energy, radiant energy and heat energy.
9.(a) Types of fuel according to theit physical state.
(i) Solid fuels.
These are fuels which exist as solid substances. For example wood and coal and charcoal.
(ii) Liquid fuels.
These are fuels which exist as liquid substances. For example kerosene, petrol and deasel.
(iii) Gaseous fuels.
These are fuels which exist as gaseous substances. For example Natural gas.
(b) Types of fuels according to their occurrence.
(i) Natural(primary) fuels.
Are fuels that exist naturally. For example natural gas, wood and coal.
(ii) Artificial(secondary) fuels
Are fuels which manufactured or derived from primary fuels.
- The following are some factors which considered when choosing a good fuel.(characteristics of a good fuel)
-Energy value.
A good fuel shoulf have high energy value.
-Verocity of combustion.
A good fuel should burn with a moderate rate.
-Ignition point.
A good fuel should have an average ignition point.
– Content of on-combustible materials.
A good fuel should have low content of non-combustible materials.
-Poisonous products.
A good fuel should not produce poisonous product during combustion.
-Availability
Good fuel should be available in large quantity.
-Affordability.
Good fuel should be affordable to most people.
-It must be easily transported
- The following are uses of fuels.
-Used to run outomobiles and industrial machines.
-Used for cooking, heating and boiling
-Used for ironing
5. ATOMIC STRUCTURE
QUESTIONS:
- choose the most correct answer from the alternatives given.
(i) It is a part of an atom that provides its mass
A: shell B: nucleus C: neutron
D: electron
(ii) Electrons that found closer to the nucleus are ________ than found far from the nucleus.
A: heavier B: lighter C: stronger
D: weaker
(iii) If an atom has 14 electrons and 14 protons it is said to be
A: neutral atom B: charged atom C: di atom D: isotope
(iv) Which of the following is NOT apart of Dalton’s atomic theory?
A: All elements are composed of atom
B: Atoms are always in motion.
C: Atoms of the same element are identical.
D: Atoms of different elements may combine to form compounds.
(v) All atoms are neutral because
A: They are contained with nucleus and shells.
B: They have both electrons and protons.
C: Electrons and protons contained equally in them.
D: They have equal number of protons and neutrons.
(vi) According to Rutherford, which statement is true about the model of an atom?
A: The nucleus is made up of electrons and protons
B: Electrons are distributed around the nucleus.
C: Sub-atomic particles are distributed throughout the atom.
D: Neutrons found in shells of an atom.
(vii) If an atom is neutral and it has 24 electrons. What is its atomic number?
A: 48 B: 12 C: 24 D: 6
(viii) Which particle of an atom represent the atomic number of an atom?
A: The total number of electrons.
B: The total number of neutrons
C: The total number of protons.
D: Mass number
(ix) One of the following is a characteristic of nucleus of an atom.
A: It is central part with low density.
B: It is neutral(not charged).
C: it contains only protons
D: it is central part with relative high density
(x) Subtracting number of neutrons from the mass number we get_____
A: Atomic weight B: number of electrons C: number of protons D: Density
- Match items in list A
with responses in list B
List A
(i) A negatively charged particle of an atom.
(ii) Protons and neutrons
(iii) Shell K
(iv)Electronic configulation of carbon atom.
(v) The part in atom where there is great probability of finding electrons.
(vi) Nuclide notation
(vii) Isotopes
(viii) Relative atomic number
(ix) Neutrons
List B.
A: Have equal atomic number but different number of neutrons.
B: Shows sub atomic particles which present in an atom.
C: Nucleons
D: Isotopy
E: Forms mass number with protons
F: Found in both shells and nucleus.
G: Have equal number of neutrons but different mass number.
H: Average mass of isotopes.
I: Carries maximum of 8 electrons
J: Carries maximum of 2 electrons
K: Electron
L: Shell
M: 2:4
N: 2:8:2
- Write T for the correct statement and F for incorrect statement.
(i) The mass of an atom is equal to the mass of its nucleus.
(ii) Isotopy are atoms of the same element having the same atomic number but different mass number.
(iii) If an atom has 3 shell, it has ability of carrying maximum of 24 electrons.
(iv) If an atom has 3 shell, it has ability of carrying minimum of 11 electrons.
(v) Sub atomic particles that found in the nucleus of an atom are not negatively charged.
- State Dalton’s atomic theory and its modification.
- It is said that, the mass of an atom is contributed only by nucleons and not electrons. Explain why?
- Explain(define) the following.
(a) Atom
(b) Electron
(c) neutron
(d) proton
(e) atomic number
(f) mass number
(g) nucleon
(h) isotopes
(i) isotopy
(j) nuclide notation
- State three characteristics of each sub atomic particle.
- (a) Differentiate
(i)electron from nucleons.
(ii) electron from proton
(iii) proton from neutron.
(b) Show the similarities between proton and neutron.
- Write the electronic configuration for the elements with the following electrons.
(a) 6 (b) 1 (c) 13 (d) 20
- P, M, N and G are isotopes if element Q, their abundances are 2%(204 mass number) 24%(206 mass number), 22%(207 mass number) and G%(A mass number) respectively. The relative atomic mass of element Q is 207.
Calculate (i) abundance G and
(ii) mass A
- Atom J has mass number 49 and atomic number 24 calculate its neutron number.
- Neon has three isotopes. Neon with mass 20(90.5%), 21(0.3%) and 22(9.2%)
Calculate its R.A.M
ANSWERS:
- (i) B (ii) B (iii) A (iv) B (v) C (vi) B (vii) C (viii) C (ix) D (x) C
- (i) K (ii) C (iii) J (iv) M (v) L. (vi) B (vii) A (viii) H (ix) E
- (i) T (ii) F (iii) F (iv) T (T)
- Dalton’s Atomic theory
John Dalton developed his theory about the
atom with five main points as follows
- Matter is made up of tiny particles called
atom
- Atoms cannot be created or destroyed
iii. Atom of any one element are identical
and have the same chemical properties
and the same mass
iv.Atom of a given element are different
from those of any other element
- Atoms of one element can combine in
simple ratio with the atom of another
element to form a compound atoms or
molecules
Modification from Dalton’s Atomic theory
- Atom is made by sub atomic particle such
as electrons, protons and neutrons
- Atoms can be created or destroyed
iii. Atom of any one element can differ
example isotopes
iv.Atoms of one element can combine in
any ratio with the atom of another
element
- The mass of an atom is said to be contributed by neutrons and protons because the mass of electrons is very small such that it is neglected.
- (a) Atom:- is a smallest particle of an element which has all chemical properties of that element
(b) Electron:- is a negatively charged particle of an atom.
(c) Neutron :- is a sub-atomic particle of an atom which has no charge.
(d) Proton :- is a positively charged particle particle of an atom.
(e) Atomic number:-refers to the number of protons of an atom.
(f) Mass number:- refers to the total number of protons and neutrons.
(g) Nucleons:- Are sub-atomic particles which found in the nucleus of an atom.
(h) Isotopes:- Are atoms of the same element which have the same atomic number but different mass number.
(i) Isotopy:- Refers to existence of atoms of the same element having the same atomic number but different mass number.
(j) Nuclide notation:- is the way of representing sub-atomic particles of an atom.
- Sub-atomic particles:- are substances which form structure of an atom.
They include
-electrons
-protons
-neutrons
Characteristics of electrons.
-Are negatively charged
-They found outside the nucleus
-The relative mass of an electron is 1/1840
Characteristics of protons.
-They are positively charged
-They found in the nucleus of an atom.
-The relative atomic mass of atom is 1
Characteristics of neutrons.
-They are not charged
-They found in the nucleus of an atom
-The relative atomic mass of neutron is 1.
- (a) (i) Difference between electron and nucleons.
-Electron found outside the nucleus of an atom While nucleons found in the nucleus of an atom.
-Electron does not contribute the mass of an atom While nucleons form form the mass of an atom
(ii) Difference between electron and proton.
-Electron is positively charged While proton is positively charged.
-Electron found outside the nucleus While proton found in the nucleus of an atom.
-Electron has mass 1/1840 While proton has mass 1.
(iii) Difference between proton and neutron.
-Protons is positively charged While neutron has no charge.
-Protons affect atom to be either charged or neutral While neutron does not affect the charge of an atom.
(b) Similarities between proton and neutron.
-both proton and neutron found in the nucleus.
-both proton and neutron contribute the mass of an atom.
- When writing electronic configulation of an atom, electrons should first filled in first shell from the nucleus before the next shell and each shell must filled with correct number of electrons before the next shell.
(a) 2:1
(b) 1
(c) 2:8:3
(d) 2:8:8:2
- Solution.
Given data:
Atomic masses
P=204
M=206
N =207
G = A
Abundances:
P=2%
M=24%
N=22%
G=A
R.A.M = 207
Abundance G=needed
Atomic mass A= needed
(i) Abundance G
Abundance G=100 – total abundance P, M and N
=100 – 2 + 24 +22
= 52
Abundance G = 52%
(ii) mass A.
From
R.A.M=(mass x abundance) + (mass x abundance)/100
207=(204 x 2) + (206 x 22) + (A x 52)/100
207=(9906 + 52A)/100
52A = 20700-9906
52A = 17904
A= 17904/52
Mass A = 308
- Solution.
Given data.
Mass number(A) = 49
Atomic number(Z)=24
Number of neutron= needed
From
A=Z + n
n= A – Z
Where by A=mass number
Z=atomic number
n=neutron number
n=49 – 24
= 25
Neutron number of atom J is 25
12: Solution.
Given data:
Atomic masses= 20, 21 and 22
Abundances= 90.5%, 0.3% and 9.2% respectively.
R.A.M =Needed
R.A.M =(mass x abundance) +(mass x abundance)/100
=((20 x 90.5) + (21 x 0.3) + (22 x 9.2))
100
R.A.M =20.2
6. PERIODIC CLASSIFICATION
QUESTIONS
1.Multiple choice.
Choose the most correct answer.
(i) One of the following elements is not earth metal.
A: magnesium
B: calcium
C: aluminium
D : beryllium
(ii) Moving down the group ______ of metals decrease.
- Electronegativity
B: reactivity
C: ionization energy
D: melting points.
(iii) Re-occurrence of similar properties of elements in the periodic table is called _____
A: periodicity
B: atomicity
C: ionization
D: electropositivity
(iv) They display both metallic and non-metallic characteristics.
A: alkali metals
B: alkali earth metals
C: halogens
D: metalloids
(v) Odourless, colourless and stable elements.
A: halogens
B: alkali metals
C: metalloids
D: noble gases
(vi) Always it represent the number of period in which an element found.
A: number of shells
B: electron in outer most shell
C: valency
D: valency shell
(vii) Element Q with electronic configuration 2:8:2 belongs to the group _____ and period ______
A: 2 and 2
B: 3 and 2
C: 2 and 1
D: 6 and 2
(viii) Hydrogen is placed in group I elements because______
A: it is a metal
B: it reacts by losing electron to form compounds
C: it reacts by gaining electron to form compounds
D: it is inert gas
(ix) When compared to metals, non-metals are ___________
A: good conductors of electricity
B: more brittle than metals
C: more ductile than metals
D: good conductor of heat.
(x) Which of the following statements does not describe the alkaline earth metals?
A: they burn in oxygen to form a solid white oxide.
B: they become less reactive as they move down the group.
C: they are good conductors of heat and electricity
D: they react with water
- Matching items.
Match items in list A with responses in list B
List A
(i) Reactivity of metals in the periodic table.
(ii) Always it increases with increase of atomic number.
(iii) The distance from the centre of the atomic nucleus to the outer most shell.
(iv) Metallic characteristics
(v) Non-metallic characteristics
(vi) Elements with some metallic and non-metallic characteristics
(vii) Hallogens
(viii) Alkali metals
(ix) Alkaline earth metals
(x) Stable non-metallic elements.
List B
A: electropositivity
B: ionization energy
C: chlorine and fluorine
D: sodium and lithium
E: argon and neon
F: electronegativity
G: magnesium and calcium
H: boron and silicon
I : increase when you move down the group
J: atomic radius
K: atomic diameter
- Why argon can not react with calcium?
- Group the following elements into metals and non-metals.
-fluorine
-oxygen
-aluminium
-neon
-magnesium
-lithium
-nitrogen
-sodium
- Identify an element which is more reactive between the following and state the reason for the element to be more reactive.
(a) sodium and magnesium
(b)chlorine and fluorine
(c) nitrogen and chlorine
(d) sodium and potassium
- Define the following terms and state the general trends of elements along the periods and down the groups
(a) ionization energy
(b) electronegativity
(c) electropositivity
(d) atomic radius
(e) boiling point
(f) density
(g) melting point
ANSWERS:
1.(i) C vi) A
(ii) C vii) B
(iii) A viii) ,B
(iv) D ix) B
(v) D x) B
2.(i) I vi) H
(ii) B vii) C
(iii) J viii) D
(iv) A ix) G
(v) F x) E
- Argon can not react with calcium because it is stable element with eight electrons in its outer shell such that it can not form bond with other elements to make compounds.
- Metals Non- metals
-aluminium -fluorine
-magnesium -oxygen
-lithium -neon
-sodium -nitrogen
- (a) Sodium is more reactive than magnesium because reactivity of metals increase from right to left along the periods of the periodic table and sodium found more left side than magnesium.
(b) Fluorine is more reactive than chlorine because the reactivity if of non-metals decrease with decrease of electronegativity. Down the group electronegativity of elements decrease.
(c) chlorine is more reactive than nitrogen because reactivity of non-metals increase from left to right along the periods of the periodic table and chlorine is found at right side of nitrogen.
(d) potassium is more reactive than sodium because the reactivity of metals increase with increase of electropositivity and down the group electropositivity of elements increases.
- (a)Ionization energy
Is a minimum energy that required to remove bond forming electron(s) from an atom.
It increases from left to right along periods of the periodic table and decreases down the groups.
(b) electronegativity
Is a tendency of elements to attract electron(s) toward it self. It increases from left to right along periods and decreases down the groups.
(c) electropositivity
Is a tendency of electrons to lose electron(s). It increases when moving down the groups.
(d) atomic radius
Is a distance from the centre region of an atom to to its outer most shell. It remain constant in size at the period but increases down the group due to increase of number of shells.
(e) boiling point
Is a point of temperature at which the substance change into vapour. It increases when moving down the group due to increase of metallic characteristics(electropositivity)
(f) density of element
Is a ratio of mass of an element to its volume.
It increases down the group as metallic of element increases.
(g) melting point.
Is the point at which solid substance turns to liquid.
It increases down the group as metallic characteristics increase.
7. BONDING, FORMULA AND NOMENCLATURE
(i)The bond between sulphur and oxygen in sulphur dioxide.
A: ionic bond
B: covalent bond
C: electrovalent bond
D: sulphur bond
(ii) The oxidation state of nitrogen in ammonium ions(NH4+) is___
A: -3 B: 5 C: 2 D: 4
(iii) Positively or negatively charged elements are called ____
A: valency
B: molecules
C: ions
D: atoms
(iv) An element with 19 electrons, its valency is____
A: 2. B: 3. C: 1. D: 4
(v) The following atoms can not exist freely as a single atom, except
A: sodium
B: chlorine
C: argon
D: magnesium
(vi) Which of the following elements is divalent element?
A: Lithium
B: calcium
C: aluminium
D: carbon
(vii) One of the following substances is radicle.
A: chlorine ions
B: potassium ions
C: nitrate ions
D: neon
(viii) Valency of carbonate ions
A: 2 B: 4 C: 1 D: 3
(ix) Ions formed when _________electrons
A: metals gain and non metals
B: elements share
C: metals lose and non-metals gain
D: elements tranfer
(x) Holds two or more substances together
A: radical
B: valency
C: chemical formula
D: bond
- Matching items
Match items in list A with responses from list B
List A
(i) positively or negatively charged elements
(ii) covalent substances
(iii) electrovalent substances
(iv) formed when atoms lose electrons
(v)valency shell
(vi)react by either sharing or gaining electrons
(vii) the force of attraction between elements with opposite charges
(viii)monovalent elements
(ix) force of attraction that holds things together
(x) hydrogen ion
List B
A: inner most shell
B: bond
C: ionic bond
D: outermost shell
E: H+
F: H
G: H-
H: ionic bond
I: solid and crystalline subatances
K: liquid or gaseous substance
L: group i elements
M: group ii elements
N: non-metals
O: metals
P: ions
Q: cations
R: anions
S: chemical bond
- Define the following terms
(i) valency
(ii)oxidation state
(iii) radicals
(iv)empirical formula
(v) molecular formular
(vi) covalent bond
(vii) electrovalent bond
(viii) binary compounds
(ix) chemical formula
(x) chemical bond
- Why covalent compounds do not conduct electricity?
- Find the oxidation number of the underlined atoms in the following compounds
(i) FeCl3
(ii) KClO3
(iii) NO3 –
(iv) SO3 2- (sulphur)
- State the valence of each atom involved to form the compound below
(a) NaCl
(b) CO2
(c) K2O
- Classify the the ions below into cations and anions
(a) Cl-
(b) Zn2+
(c) SO4 2-
(d) NH4 +
(e) Li +
(f) I-
8.Name the following binary compounds.
(i)H2S
(ii) PCl5
(iii) CCl4
(iv) FeBr2
(v) H2Cl2
- Write the chemical formula of the following compounds.
(i) iron ii chloride
(ii) carbon monoxide
(iii) Zinc chloride
(iv) potassium iodide
- Calculate the empirical formula of hydrocarbon molecule made by 88.88% of carbon and 11.12% of hydrogen.
- Show the difference between covalent compound and electrovalent compounds (four points).
- A certain compound is made up of 69.58% of barium, 6.09% of carbon and 24.32% of oxygen. Calculate the empirical formula of the compound. R.A.M of barium is 137.3
- What is the molecular formular of the compound made by 15.8% carbon and 84.2% sulphur? The molecular mass of the compound is 76
- Calculate the molecular formula of an organic compound which consists 84.9% carbon and 15.1% hydrogen. Its molecular mass is 70
- Show difference between oxidation state and valency.
ANSWERS:
- (i) A (vi) B
(ii)A (vii) C
(iii)C (viii) A
(iv)C (ix) C
(v) C (x) D
- (i) P vi) N
(ii) K vii) C
(iii) I viii) L
(iv) Q ix) S
(v) D x) E
- (i) Valency:- is the combining power of an element.
This means ability of an element to combine with other elements depends on valency.
(ii) Oxidation state:- is a number of electron(s) that element can lose, gain or share when forming a compound.
(iii) Radical:- is a group of atoms with unpaired electrons and acts as a single atom.
(iv) Empirical formula:- is a simplest chemical formula which express its composition by mass.
(v) Molecular formula:- is a simplest chemical formula which shows the actual number of atoms present in the compound.
(vi) Covalent bond:- is a bond which formed by sharing electrons between non-metals.
(vii) Electrovalent bond:- is a bond which formed when electron(s) transfered from metal to non-metal.
(viii) Binary compound:- is a compound which made up of two two ions.
(ix) Chemical formula:- refers to representation of chemical compound by using symbols of elements in correct proportions.
(x) Chemical bond:-is a force of attraction that holds two or more elements together.
- Covalent compounds do not conduct electricity because they have no free ions which are necessary for carrying electric current in molten or solution form.
- (i) Solution.
Data:
Oxidation states
Fe=needed
Cl= -1
Fe + (-1×3)=0
Fe -3=0
Fe=0+3
Oxidation state of iron=3
(ii) Data:
Oxidation states
K=1
Cl=needed
O=-2
1 + Cl + (-2 x 3)=0
1 + Cl + (-6) =0
Cl – 5 =0
Cl=5
Oxidation state of Cl =5
(iii) Data:
Oxidation states.
N=needed
O=-2
N + (-2 x 3)= -1
N + (-6) =-1)
N= -1 + 6
N=5
Oxidation state of N = 5
(iv) Data:
Oxidation states.
S=needed
O=-2
S + (-2 x 3) = -2
S + (-6)=-2
S=-2 + 6
S=4
Oxidation state of sulphur = 4
- We write chemical formula by interchanging valences of reacting species.
In order to determine the valency of an atom in a chemical formula, firstry the valence of individual atom must be identified.
(i) NaCl
The falency of Na=1
Cl=1
(ii) CO2
The valency of C=4
O=2
During exchange of the valences, 4 placed at Oxygen(O4) and 2 placed at carbon (C2) then C2O4 obtaned and simplified by dividing by 2 to get CO2
(iii) K2O
The valency of K=1
O=2
- Cations. Anions.
b, d, e a, c, f
- (i) dihidrogen sulphide.
(ii) phosphorous pentachloride
(iii) carbon tetrachloride
(iv) iron(ii) bromide
(v) hydrogen chloride
- (i) FeCl2
(ii) CO
(iii)ZnCl2
(iv) KI
- Solution.
Data given.
Masses C=12g
H=1g
%composition C= 88.88
H=11.12
Elements symbols C H
Mass 12 1
%comp./mass 88.88/12 11.12/1
=7.407 =11.12
Divide by
Smallest no.
7.407/7.404 11.12/7.404
=1 1.5~2
C1. H2
Epirical formula is CH2
- (i) covalent compound are either liquids ir gaseous While electrovalent are solid crystalline.
(ii) covalent compounds do not conduct electricity in molten state While electrovalent compounds conduct electricity in molten state.
(iii) covalent compound are generally insoluble in water While electrovalent compounds are generally soluble in water.
(iv) covalent compounds have low melting points while electrovalent compounds have high melting points
(v)covalent compounds formed when non-metals react While electrovalent compounds formed when metals react with non-metals.
- Solution.
Data given.
Relative atomic massea (R.A.M )
Barium(Br)=137.3
Carbon=12
Oxygen=16
%composition Br=59.58
C=6.09
O=24.32
Elements symbols Br C O
%comp./R.AM =0.508 =0.508 =1.52
Divide by
Lowest number =1. =1. =3
Br1. C1. O3
Empirical formuls is BrCO3
- Solution.
Data given.
R.A.M C=12
S=32
%comp. C=15.8
S=84.2
Elements symbols. C S
%comp./R.A.M. 15.8/12 84.2/16
=1.32 =2.63
Divide by
Smallest No. 1.32/1.32 2.63/1.32
=1 =2
C1 S2
Empirical formula is CS2
Molecular formula= (Ef)n
(Empirical formula)n=76
(CS2)n = 76
(12 + (16×2))n=76
(44)n=76
n=76/44
n~1
Molecular formula= C1x1 S2x1
=CS2
- Solution.
Data given.
R.A.M C=12
H=1
%composition.
C= 84.9
H= 15.5
Elements symbols C H
%comp./R.A.M 84.9/12 15.1/1
=7.08 =15.1
Divide by
Smallest No. 7.08/7.08 15.1/7.08
=1 =2
C1 H2
Empirical formular is CH2
M.F = (E.F)n
M.F = (CH2)n
(CH2)n = 70
(12+(1×2))n=70
14n=70
n=70/14
=5
M.F=(CH2)5
=C5H10
Molecular formular is C5H10
- √Oxidation state is arbitrary value While Oxidation state is a fixed value
√Oxidation state is either negative or positive While valence has no charge.
