Waec Chemistry 2007 Past Questions and Answers

Question 21:

• WAEC 2007

What process is illustrated below? S_(s) ⇌^H₂O⇌ S _(aq)

A. Decomposition of a solid
B. Melting of a solid
C. Formation of saturated solution of a solid
D. Sublimation of a solid

Question 22:

• WAEC 2007

A solution of a salt X reacts with AgNO₃ solution to give white precipitate which dissolves in excess aqueous ammonia. X contains

A. CI^-
B. Pb ²⁺
C. SO ^2-
D. Zn²⁺

Question 23:

• WAEC 2007

Consider the reaction represented by the following equation: N_2(g) + 3H_2(g) ⇌ 2NH_3(g); ∆H = - 92kJmol¹. Finely divided iron is used as catalyst in the reaction in order to

A. Lower the value of ∆H
B. Increase the time for attainment of equilibrium
C. Shorten the time for attainment of equilibrium
D. Decrease the yield of ammonia

Question 24:

• WAEC 2007

Which of these cell notations is the correct representation of a Daniell cell?

A. Zn_(s) / Zn²⁺_{(aq) // Cu^2+(aq)/Cu[sub](s)}[/sub]
B. Cu_(s) / CU^{2+_(aq) // Zn[sup]2+}_(aq) / Zn_(s)[/sup]
C. Zn²⁺_(aq) / Zn_(s) // Cu²⁺_(aq) /Cu_(s)
D. Cu²⁺_(aq) / Cu_(s) // Zn_(s) / Zn²⁺_(aq)

Question 25:

• WAEC 2007

What is the oxidation number of chromium in K₂CrO₄?

A. +1
B. +2
C. +4
D. +6