WAEC Chemistry Questions & Answers for 2020/2021 (Theory and Objectives)

WAEC Chemistry 2020 Answers for Objective & Theory Questions is Out. The WAEC chemistry questions and their answers for 2020 examination can be seen here now. The West African Examination Council (WAEC) Chemistry SSCE exam paper will be written on Wednesday, 2nd September 2020.

The Waec chemistry 2020 Essay paper will start by 2:00pm and will last for 2hrs while the WAEC chemistry Objective exam will commence 4:00pm and will last for 1hr.

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WAEC Chemistry Questions and Answers 2020

The questions below are the WAEC Chemistry Questions. Go through them and be ready to score high in your WAEC 2020 Chemistry Examination.

1. What condition favours the formation of the product for the endothermic reaction, N2O4(g) —><—– 2NO2(g)

  • A. Decrease in pressure
  • B. A decrease in volume
  • C. An increase in pressure
  • D. A constant volume

ANSWER: A ( Decrease in pressure)

2. How many alkoxy alkanes can be obtained from the molecular formula C4 H4O4

  • A. 1
  • B. 2
  • C. 3
  • D. 4

ANSWER: C (3)

3. Element Y has two isotopes Y and Y present in the ratio 1:3. The relative atomic mass of Y would be

  • A. 20.5
  • B. 21
  • C. 21.5
  • D. 22

ANSWER: C (21.5)

4. 100.0g of KClO3 was added to 40.0 cm^3 of water to give a saturated solution at 298K. If the solubility of the salt is 20.0 moldm^-3 at 298K, what percentage of the salt is left undissolved? {K= 39, Cl = 35.5, O = 16}

  • A. 80%
  • B. 60%
  • C. 5%
  • B. 2%

5. Elements X and Y have electronic configuration 1S22S22P4 and 1S22S22P63S23P1 respectively. When they combine the formula of the compound formed is

  • A. XY
  • B. Y2X3
  • C. Y2 X3
  • D. Y X2

ANSWER: B (Y2X3)

6. A solution of 0.20 mole of NaBr and 0.20 mole of MgBr2 in 2.0 dm3 of water is to be analysed. How many moles of Pb(NO)2 must be added to precipitate all the bromide as insoluble PbBr2

  • A. 0.30 mol
  • B. 0.10 mol
  • C. 0.20 mol
  • D. 0.40 mol

ANSWER: A (0.30 mol)

7. Na2CO3 + HCl —-> NaHCO3 + NaCl. The indicator most suitable for this reaction should have pH equal to.

  • A. 3
  • B. 5
  • C. 7
  • D. 9

ANSWER: D (9)

8. A satuarted solution of silver trioxocarbonate (IV), was found to have concentration of 1.30 x 10-5 moldm-3 . The solubility product of the trioxocarbonate (IV) is

  • A. 8.79 x 10-15
  • B. 1.69 x 10-10
  • C. 1.82 x 10-11
  • D. 9.84 x 10-10

ANSWER: A (8.79 x 10-15)

9. When platinum electodes are used during the electrolysis of copper (II) tetraoxosulphate (IV) solution, the solution gets progressive

  • A. Acidic
  • B. Basic
  • C. Neutral
  • D. Atmospheric

ANSWER: A (Acidic)

10. Tetraoxosulphate (VI) ions are final test using

  • A. acidified silver nitrate
  • B. acidic barium chloride
  • C. lime water
  • D. dilute hydrochloric acid

ANSWER: D (dilute hydrochloric acid)

WAEC 2020 Chemistry Theory Questions

PAPER 2 (ESSAY)

SECTION A

1. Identify the solid remaining when each of the following is heated.
(a) lithium trioxonitrate (V)
(b) potassium trioxonitrate (V)
(c) calcium trioxonitrate (V)

2. (a) When calcium oxide and coke are heated in an electric furnace, the products are carbon (ii) oxide and calcium carbide (CaC2), write the equation for this reaction.

(b) The addition of water to calcium carbide leads to the formation of calcium hydroxide and ethyne. Write the equation for the production of ethyne.

3. Calculate the percentage by mass of silicon tetrachloride. [2 marks]
4. Ammonia, NH3, and phosphine, Ph3, are the hydrides of the first two elements in group 5.
(a) Draw a dot and cross diagram for the ammonia molecule. [2 marks]
(b) Sketch and explain the shape of the ammonia molecule. [3 marks]

5. The first ionization energy of chlorine is +1260KJmol-1.
(a) Define the term first ionization energy.
(b) State and explain the general trend in the values of the first ionization energy for the elements across the period, sodium to argon in the periodic table.

6. Compound A consisting of carbon and hydrogen only. The compound was found to contain 80% carbon by mass.
(a) Calculate the empirical formula of compound A using the data above.
(b) The relative molecular mass of compound A was found to be 30.
Use this information to deduce the molecular formula of compound A.
[H = 1.00 C = 12.00]

7. State two factors other than a change in temperature or the use of a catalyst that influence the rate of a chemical reaction.

SECTION B

1. (a) Two elements represented by the letters Q and R have atomic numbers 9 and 12 respectively.
(i) Write the election configuration of R.
(ii) To what group does Q belong in the periodic table.
(iii) Write the formula of the compound formed when Q combines with R.
(iv) Explain briefly, why Q is a good oxidizing agent.
(v) State whether R would be expected to form acidic or basic oxide.
(b) (i) State two assumptions of the kinetic theory of gases.
(ii) When some solids are heated, they change directly into the gaseous state. What name is given to this phenomenon?
(iii) List two substances which exhibit the phenomenon mentioned in (ii).
(iv) Write an expression to show the mathematical relationship between the rate of diffusion of a gas and its vapour.

2. An aqueous solution has a pH of 4.0.
(a) (i) What is the hydrogen ion concentration of the solution?
(ii) What effect will it have on litmus paper?
(iii) Which of the following salt solutions would have the same effect on litmus? Give a reason for your answer. NH4Cl(aq); NaCl(aq) ; CH3OON(aq).
(b) (i) Differentiate between a fine chemical and a heavy chemical.
(ii) Name two sources of air pollution.
(iii) Suggest one way of reducing air pollution in cities

3. (a) (i) Explain briefly the fermentation process.
(ii) Write a balanced equation for the fermentation of glucose.
(iii) What substance must be added to glucose solution to ferment it?
(iv) Explain briefly why tightly corked glass filled to the brim with palm wine shatters on standing.
(b) State one industrial application of each of the following methods of separation:
(i) Crystallization;
(ii) Fractional distillation.
(c) Explain the following terms:
(i) Saponification;
(ii) Esterification.
(d) Write a balanced equation to illustrate each of the terms in (c).
(e) i) What is hydrocarbon compound?
(ii) Name two principal sources of hydrocarbons.

WAEC Chemistry Essay and Objective 2020 (EXPO)

The above questions are not exactly 2020 WAEC Chemistry questions and answers but likely WAEC Chemistry repeated questions and answers.

These questions are for practice. The 2020 WAEC Chemistry expo will be posted on this page 30 minutes before the WAEC Chemistry examination starts. Keep checking and refreshing this page for the answers.

Keep following, more questions and answers will be updated and added soon.

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