Waec Chemistry 1992 Past Questions and Answers

Question 36:

• WAEC 1992

What is the value of n in the following equation? XO-₄ +8H ⁺ + ne- → X^{2 +} + 4H₂O

A. 2
B. 3
C. 4
D. 5
E. 6

Question 37:

• WAEC 1992

A dye is suspected to have contaminated a lollipop. Which of the following is the best method by which the contaminant may be isolated?

A. Fractional distillational
B. Recrystallization
C. Filtration
D. Paper chromatography
E. Evaporation

Question 38:

• WAEC 1992

Which of the following accounts for the difference in the mode of conduction of electricity by metals and aqueous salt solutions?

A. Electrons are present in metals but not in salt solutions
B. Metals are conductors while salts are electrolytes
C. Electricity is carried by mobile elrctrons in metals but by ions is aqueous salt solution
D. Salts ionize in aqueous solutions while metals do not
E. Metals are reducing agents while salts are not

Question 39:

• WAEC 1992

(a) State the method of collecting gases which are denser than air.
(b) Name two gases that can be used to perform the fountain experiment in the laboratory. State the physical property which makes it suitable for the experiment.

Question 40:

• WAEC 1992

(a) State the main ore of tin.
(b) Write an equation for the reaction involved in the smelting of purified tin ore
(c) List two alloys of tin