Waec Chemistry 1990 Past Questions and Answers

Question 11:

• WAEC 1990

A catayst which increases the rate of a chemical reaction does so by

A. Increasing the reaction pathway
B. Increasing the surface area of the reactants
C. Increasing the pressure on the system
D. Decreasing the temperature at which the reaction occurs
E. Decreasing the activation energy of the reaction

Question 12:

• WAEC 1990

How many molecules are there in 14g of nitrogen gas at s.t.p? (n = 14, Avogadro Number = 6. 0 x 10₂₃ mol_-1)

A. 1.2 x 10 ²³
B. 3.0 x 10²³
C. 6.0 x10²³
D. 1.2 x 10²⁴
E. 30 x10²³

Question 13:

• WAEC 1990

Which of the following correctly explains entropy?

A. The natural tendency for a system to achieve a greater disorder
B. A balance of two driving forces between free energy and enthalpy changes
C. The cause of spontaneity of a reaction
D. A measure of the enthalpy of a reaction
E. A measure of the rate of attaining equilibrum in a reversible reaction

Question 14:

• WAEC 1990

The gas that is liberated when iron is heated with concentrated tetraoxosulphate (VI)acid is

A. H₂S
B. \(SO_{2}\)
C. HCI
D. SO₃
E. O₂

Question 15:

• WAEC 1990

Which of the following salts in aqueous solution will have a pH greater than 7?

A. NaCl
B. ACI₃
C. FeCI₃
D. Na ₂SO₄
E. K ₂CO₃