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NABTEB Chemistry Questions And Answers 2021
(ai). An experiment showed that 16.25g of iron chloride were obtained from the combination of 5.6g
of iron with chlorine. What is the formula of the iron chloride? (fe=56, CL=35.5).
(aii). Sulphur is soluble in ethanol but not in water while sodium chloride is soluble in water but not in
ethanol. Describe how you will separate sodium chloride from a mixture of sulphur and sodium chloride.
(b). Add water to the mixture in order to dissolve the sodium chloride. Filter to obtain the sodium
chloride as the filtrate.
Evaporate the filtrate and the sodium Chloride solid is left behind in the evaporation dish. Put the
sulphur residue in a filter paper and allow to dry.
(ai) Define heat of combustion of a compound.
(ii) When 4.6g of ethanol, CH3CH2OH were burned in a calorimeter containing 1.0kg of water, the
temperature rises from 291k to 316k. If the specific heat capacity of water is 4.18kj-1k and the water
equivalent of the calorimeter is 1.3kjk-1 and the relative molar mass of ethanol is 46. Calculate the
enthalpy of combustion of ethanol.
An atom has 14 neutrons in the nucleus and an atomic number of 13.
1. State the composition of the nucleus.
2. Describe the arrangement of the electrons
3. Name the element for which the atom is an isotope and
4. State its valency.
(bi) In what ways are a sodium ion and a neon atom alike?
(iii) How do they differ?
a. Define each of the following terms.
1. Electrolysis: – is the chemical decomposition of a compound due to the passage of electricity
through its solution or molten state.
2. Electrolytes: – are substances in solution or molten state that permit passage of electricity to
undergo chemical decomposition.
3. Electrodes: – are solid conducts (metals or semi metal) through which electricity passes into or
out of an electrolyte during electrolysis.
(b) Differentiate between true electrolytes and POTENTIAL electrolytes.
1. True Electrolytes are compounds which in solution or molten state will conduct electricity and
decompose during the process.
2. Potential Electrolytes are compounds which are not conductors unless they react with another
compound- (e.g. polar solvent), before conducting electricity and decomposing.
Explain the terms ENDOTHERMIC reaction and EXOTHERMIC reaction.
I. Endothermic reaction is a chemical reaction in which heat is absolved from the atom sphere or
Endothermic reaction is a chemical reaction that required heat from the atmosphere to take place.
ii. Exothermic reaction is a chemical reaction that produces heat to the atmosphere.
(a) Define and give an example each of the following:
i. Acid salt
Ii.Basicity of an acid
vi. Hydroscopic substance
Acid salt is a compound made up of a metallic cation and non metallic anion which dissolves in water to
produce a weak acid E.g. KHS04, Ca (HS04)2.
ii. The basicity of acid is the number of hydrogen ions, 1 molecule of it can produce in solution, or
e.g., Basicity of HN03 = 1, H2SO4=2, H3PO4=3 , HCL = 1.
iii. Deliquescent substance is that matter which absorbs water moisture, from the atmosphere to form a
solution at the end Examples includes
Sodium hydroxide pellets.
Iron (II) Chloride crystals
Calcium chloride (fused)
Phosphorous (v) oxide
(iv) Double salt is that which ionized to produce three different types of ions in solution
E.g. NaNH4SO4, Kmn04
(v) Efflorescent substance is that crystal that form one or more (some) molecules of water of
crystallization when exposed to the atmosphere. Examples include.
Na2C03. 10H2O, CUS04-5H20, Mgs04.7H20.
(Vi) Hydroscopic substance is the substances which absorbs moisture from the atmosphere but does not
dissolves in it.
1. (a) Give THREE differences between a physical and chemical change.
(b) What do you understand by the term eletrovalency?
(C) X is an element with relative molecular mass 24 and atomic number 12. It form a chloride whose
relative molecular mass is 95.
i. Give the equation of the reaction.
ii. When the element X reacts with water it forms a chloride which dissociate to give the ion,
explain the differences between X atom and X ion.
iii. State the type of valency in the chloride.
iv. Write a balanced equation for the reaction of X with water
1) 3 differences between a physical and chemical change
No new substances are formed
It is easily reversible not easily reversible
No change in mass of substance.
Accompanied by small heat
Component can be separated by physical reaction
Chemical change ___________________
entirely new substances are formed
Involves changes in mass of substances
change accompanied by great heat change.
component cannot be separated by physical (but chemical) reaction
(2a) State the law of constant composition.
(b) What is the (1) number of moles and (ii) mass of copper deposited when 96, 50.C coulombs of
electricity is passed through copper II Salt.
(C ). With the aid of a well labeled diagram, show how ethane can be prepared in the laboratory
(d). Give four chemical reactions of ethane (use equations only)
(e). Give four uses of ethane.
3a. What is an electrolyte?
b. Describe the production of chlorine from brine
c. Write a balanced chemical equation for the reaction of chlorine with
i. An aqueous solution of sulphur oxide.
ii. A metal
iii. Potassium iodide
4b.i) Give two condition that is required for iron to rust.
ii. State how the formation of rust can be prevented
4b.i) presence of air and water
ii. * Oiling
7) Electro planting
8) Cathodic protection
4c. Use equation to show what happens when the following compounds are exposed to the
1) Anhydrous calcium chloride
2) Calcium oxide
3) Solid sodium hydroxide.
4(e) Give two uses of sodium
(e) Uses of sodium
* Manufacture of compound e.g. sodium peroxide, sodium cyanide e.t.c
* In sodium vapors lamps (for lighting highway and airport)
* Liquid sodium is used as a coolant in nuclear reactors.
* Sodium and ethanol or sodium amalgam and water are very good reducing agents.
5a. List four factors that can alter the rate of chemical reaction.
FACTORS THAT CAN AFFECT REACTION RATE.
1) Nature of the reactants
2) Concentration/pressure ( for gases) of the reactant
3) Surface area of reactants.
4) Temperature of reaction mixture
5) Presence of light
6) Presence of a catalyst.
5b. With the aid of equation
1(a). What is an Atom?
An atom is the smallest unit/representative/particle of matter made up of electrons, protons
1(b) Explain briefly the following terms using an example to illustrate each.
i. Atomic mass number
ii. Nuclear charge
i. The atomic mass number is the sum of protons and neutrons in an atom e.g. chlorine which has
17 protons and 18 neutrons has mass 35.
ii. Nuclear charge is the sum of proton charges in the nucleus. Na has 11 protons; its nuclear
charge is (l).
iii. Valency is the combining power of an atom when it reacts with another to from a bond.
iv. Isotopy is the occurrence of two or more atoms of an element with different numbers of
neutrons or atomic mass number. e.g. carbon, oxygen, chlorine.e.t.c.
1(c) Describe the laboratory preparation of dry oxygen gas.
i. Name THREE uses of oxygen.
i. Respiration of plants and animal
ii. In welding of metals oxy-ethyne flame
iii. Drivers, mountain climbers, and miners use it.
iv. In the steel industry to remove carbon, sulphur and phosphorus.
bi State THREE differences between aliphatic and aromatic hydrocarbons
Give THREE uses of Benzene
ai State the second law thermodynamics
ii. Give THREE Conditions for a chemical change to occur spontaneously.
i) The second law of thermodynamics states that a spontaneous process
occurs only if there is an increase in entropy of the system and the
ii) Total entropy change must be positive i.e. S (total) >0 free energy of the
the system must be negative i.e. G< 0.
The transition Energy complex must be reached.
B. With the aid of a diagram state FOUR differences between exothermic and
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