WAEC Chemistry Questions Objective and Theory For Free 2022/2023

WAEC Chemistry Past Questions 2022 PAPER 2 (ESSAY)

SECTION A

1. 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]

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. 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

A. Protons, neutrons, and electrons.
B. Protons and neutrons but a different number of electrons.
C. Protons and electrons but different number of neutrons.
D. Neutrons and electrons but a different number of protons.

2. Which type of chemical bond is formed by the transfer of electrons?
A. Covalent
B. Dative
C. Ionic
D. Metallic

3. The concentration of an aqueous solution is 5mg dm-3. Determine is the concentration in parts per million (ppm).
A. 500 ppm
B. 50 ppm
C. 10 ppm
D. 5 ppm

4. Consider the following species: H, H+, H-. What is the number of electrons in each of the species respectively?
A. 1, 0, 2
B. 0, 1, 2
C. 2, 1, 0
D. 1, 2, 0

5. Two electrons can occupy the same orbital if they have different
A. Angular momentum quantum numbers.
B. Magnetic quantum numbers.
C. Principal quantum numbers.
D. Spin quantum numbers.

6. What mass of NaOH is required to make 250 cm3 of 0.10mol/dm-3 solution? [Na = 23, O = 16, H = 1]
A. 1 g
B. 4 g
C. 8 g
D. 16 g

7. Which of the following substances is not a hydrocarbon?
A. Benzene
B. Butane
C. Ethyne
D. Ethanamide

8. A substance which ionizes completely into hydroxonium ions is a
A. Strong acid.
B. Strong base.
C. Weak acid.
D. Weak base.

9. Which of the following solutions is able to resist changes in pH when small amounts of an acid or a base is added?
A. Buffer solution
B. Neutral solution
C. Saturated solution
D. Supersaturated solution

10. Protein is a polymer formed from the linkage of
A. Amino acid molecules.
B. Fatty acid molecules.
C. Glucose units.
D. Monosaccharides.

13. An element $\text{X}$ forms the following oxides ${\text{X}}_2\text{O},\text{XO}$ and ${\text{XO}}_2.$ This phenomenon illustrates the law of ________