Waec Chemistry 2020 Past Questions and Answers

Question 36:

• WAEC 2020

Which of the following statements about the solubility of a salt is correct?

A. A salt whose solubility increases with temperature would not crystallize easily on cooling
B. A salt whose solubility is independent of temperature would normally crystallize out on cooling
C. Crystallization would be efficient in separating out a salt whose solubility increases considerably with temperature
D. Solubility of a solid does not affect its crystallization

Question 37:

• WAEC 2020

How many moles of H\(_2\)SO4 are there in 50 cm\(^3\) of 0.108 mol dm\(^3\) solution of the acid?

A. 5.4x 105.4 x 10\(^-3\)
B. 5.4x 10\(^-1\)
C. 5.4 x 10\(^-2\)

Question 38:

• WAEC 2020

. If 20 cm\(^3\) of sodium hydroxide was neutralized by 20 cm\(^3\) of 0.01 mol dm3 tetraoxosulphate(VI) acid, what is the concentration of the solution?

A. 0.010
B. 0.020
C. 0.100
D. 0.150

Question 39:

• WAEC 2020

"Electrons always occupy the lowest empty energy level" is a statement of

A. Aufbau Principle
B. Hund's rule
C. Pauli Exclusion Principle
D. Periodic law

Question 40:

• WAEC 2020

Which of the following metals does not react with water to produce hydrogen?

A. Copper
B. Potassium
C. Sodium
D. Zinc