WAEC GCE Chemistry Questions 2021 Objective and Theory Update : Current School News

WAEC GCE Chemistry Questions 2021 Objective and Theory Update

Filed in Exam, WAEC News by on February 19, 2021

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WAEC GCE Chemistry Questions 2021 Objective and Theory Update.

WAEC GCE Chemistry Questions 2021: Chemistry WAEC GCE expo questions are out now on our website. In this article, I will be showing you past WAEC GCE Chemistry random repeated questions for free. You will also understand how the examination questions are set and many more examination details. Continue reading.

WAEC GCE Chemistry Questions 2021

The West African Examinations Council (WAEC) is an examination board that conducts the West African Senior School Certificate Examination (WASSCE), for University and Jamb entry examination in West Africa countries. In a year, over three million candidates registered for the exams coordinated by WAEC.

Common WAEC GCE Chemistry Questions and Answers

CHEMISTRY OBJ ANSWERS:

1-10. ADCAADAADA
11-20. DDDBBDDDCC
21-30. CBBACBADAD
31-40. CACCBDDADB
41-50. CDBCDBCCBA

Paper 2 [Essay] Questions:

Write your answers on the answer booklet provided.

1. (a) (i) What is the structure of the atom as proposed by Rutherford?

(ii) Distinguish between the atomic number and the mass number of an element.

(iii) Explain briefly why the relative atomic mass of chlorine is not a whole number.

(b) (i) What is meant by first ionization energy?

(ii) List three properties of electrovalent compounds

(iii) Consider the following pairs of elements:

9F and 17CL;

12Mg and 20Ca.

Explain briefly why the elements in each pair have similar chemical properties.

(c) Explain briefly the following terms using an appropriate example in each case

(i) homologous series;

(ii) heterolytic fission.

(d) State the indicator(s) which could be used to determine the end-point of the following titrations:

(i) dilute hydrochloric acid against sodium hydroxide solution;

(ii) dilute hydrochloric acid against ammonium hydroxide solution;

(iii) ethanoic acid against sodium hydroxide solution.

(e) A solid chloride E which sublimed on heating reacted with an alkali F to give a choking gas G. G turned moist red litmus paper blue.  Identify E,F and G.

ANS: (a) (i) The atom has small/ tiny positively charged centre /nucleus with electrons surrounding the space around  the centre.

(ii) Atomic number of an element is the number of protons/electrons in an atom of the element while mass number is the sum of the protons and neutrons in the atom of the element.

(iii) Chlorine atom is made up of a mixture of isotopes and the relative atomic mass of chlorine is the average of its isotopic masses.

(b) (i) Is the (minimum) energy required to remove one mole of an electron from one mole of gaseous atom (to form one mole gaseous charged ion

(ii) High melting /boiling point;

Ability to conduct electricity in the molten state or in solution;

Solid at room temperature;

Soluble in water or polar solvents /insoluble in non-polar solvents.

(iii) Atoms of the elements in each pair have the same number of electrons in their outer-most shell therefore similar chemical properties.

(c) (i) Is a family of organic compounds:

– where successive members differ by –CH2 of  molar mass of 14;

– with similar chemical properties;

– which conform to the same general formula;

– which show gradation of physical properties;

– which have the same general method of preparation. e.g  alkanes, alkenes , alkanols.

(ii) Is a process in which a (covalent) bond is broken in such a way that the electron pair is completely transferred to one of the atoms (resulting in the formation of ions)

H ÷ CI     →      H+ + Cl-/ HCl ® H+ + Cl-

(d)(i) Methyl orange/ methyl red/ phenolphthalein;

(ii) Methyl orange/ methyl red;

(iii) Phenolphthalein.

(e) E   –   NH4Cl

F  –  NaOH, KOH, or Ca (OH)2,  Li OH, CsOH, Ba(oH)2, Mg(OH)2

G  –   NH3.

2. (a) (i) Define saturated solution.

(ii) The solubility of KN03 at 20°C was 3.00 mol dm-3 If 67.0g of KN03 was added to 250cm3 of water and stirred at 20°C, determine whether the solution formed was saturated or not at that temperature.

(b) (i) Distinguish between dative bond and covalent bond.

(ii) Explain why sugar and common salt do not conduct electricity in the solid state.

(iii) State the type of intermolecular forces present in

  1. hydrogen fluoride;
  2. argon.

(iv) Consider the compounds with the following structures:

S – H —-N and 0 – H —–N

In which of the compounds is the hydrogen bond stronger? Give reason for your answer.

(c) (i) State Dalton’s Law of Partial Pressure.

(ii) If 200cm3 of carbon(IV) oxide were collected over water at 18°C and 700 mmHg, determine the volume of the dry gas at s.t.p.[ standard vapour pressure of water at 18°C = 15 mmHg]

ANS: (a) (i) Is a solution which contains the maximum amount of solute it can dissolve at a given temperature (in the presence of undissolved solute).

(ii) Solubility of KN03 in in g dm-3 = 3.00 x 101 = 303

.. 1000cm3 of saturated solution = 303g

250cm3 of the solution = 303 x 250

1000

= 75.8 g

Since the quantity of KN03 added (67.0) to 250 cnr’ of water is less than maximum amount required to form a saturated solution, then the solution is unsaturated.

(b)(i) In dative bond, only one of the participating atoms/ species donated electrons to be shared by both atoms while in covalent bond both participating atoms/ species contribute equally the electrons being shared.

(ii) Sugar is covalent while common salt (NaCl) is electrovalent/ ionic. Electrical conductivity (in compounds) depends on presence of mobile ions.

(iii) The intermolecular forces present in hydrogen fluoride and argon were hydrogen bond and van der Waal’s forces respectively.

(iv) 0 – H —- N has a stronger hydrogen bond because oxygen is more electronegative and smaller in size than sulphur.

(c)(i) the total pressure exerted by a mixture of gases which do not react chemically is equal to the sum of the individual partial pressures of the gases in the mixture.

(ii) pressure of the dry gas (P 1) = 700 – 15 = 685 mmHg

VI = 200cm3, TI = 18°C = 273 + 18 = 291K, P2 = 760 mmHg,

T2 = 273

P1V1 = P2V2

T1         T2

V2 = P1V1T2   =

P2T1

= 685 x 200 x 273

760 x 291

= 169.1cm3

3. (a) (i) Define nuclear fission

(ii) A certain natural decay series starts with and ends with. Each step involves the loss of an alpha or a beta particle. Using the given information,  deduce how many alpha and beta particles were emitted.

(b) Consider the equilibrium reaction represented by the following equation: A2(g)  +  3B2(g)    2AB3(g);    H   =  +  kJmol-1

Explain briefly the effect of each of the following changes on the equilibrium composition;

(i)  increase in concentration of B;

(ii) decrease in pressure of the system;

(iii) addition of catalyst.

4. Copy and complete the following table:

Oxide of nitrogen            Oxidation state of nitrogen        Colour of gas     Solubility in water          Action on damp blue litmus paper

N2O       + 1                         Insoluble

NO                        Colourless

NO2

(i) Mention one compound that makes water

  1. temporarily hard;
  2. permanently hard.

(ii) State one method that could be used to remove

  1. only temporary hardness;
  2. permanent hardness.

(iii) Write an equation to show the removal of:

  1. temporary hardness;
  2. permanent hardness.

(c) (i) List three sources of water pollution.

(ii) Mention two ways by which water pollution can be controlled.

(d) state the function of each of the following substances in the purification of water for town supply:

  1. sodium aluminate (III) (NaAIO2);
  2. lime (calcium hydroxide);

DISCLAIMER! These are not real WAEC GCE Chemistry questions but likely repeated questions over the years to help candidate understand the nature of their examinations. Ensure to take note of every questions provided on this page.

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