WAEC Chemistry Past Questions & Answers - Page 181

901.

Consider the cell represented below: Zn/Zn2+(aq) // Cu2+(aq) / Cu(s). Which of the following statements is correct about the cell

A.

Zn is oxidized to Zn2+

B.

Cu is oxidized to Cu2+

C.

It is an electrolytic cell

D.

each single line represents a salt bridge

View answer & explanation

Correct answer is A

No explanation has been provided for this answer.

902.

If 60 cm3 of gas is heated from 27oC TO 50oC, what is the new volume of the gas at constant pressure?

A.

32.4cm 3

B.

55.7cm3

C.

64.6cm3

D.

111.1cm3

View answer & explanation

Correct answer is C

V1 = 60cm T1 = 273 +27 = 300K
T2 = 273 + 50 = 323KV2 = ?
V1/T1 = V2/T2 .: V2 = V1T 2/T1 = 60 x 323/300 = 19380/300 = 64.6cm3

903.

An orange drink concentrate is suspected to contain traces of poisonous green dye and a harmless dye having the same boiling point. Which of the following techniques is most suitable for isolating the dyes?

A.

Fractional distillation

B.

Paper chromatography

C.

Coagulation

D.

Recrystallization

View answer & explanation

Correct answer is B

No explanation has been provided for this answer.

904.

Which of the following factors that affect the rate of chemical reactions can be explained in terms of the collision theory? l. concentration ll. pressure lll. temperature lV catalyst

A.

l and ll only

B.

l, ll and lll only

C.

l and lll only

D.

l, II, lll and IV only

View answer & explanation

Correct answer is D

The factors that affect reaction rates are:

  • surface area of a solid reactant.
  • concentration or pressure of a reactant.
  • temperature.
  • nature of the reactants.
  • presence/absence of a catalyst

905.

WHICH OF THE FOLLOWING SALTS IS READILY SOLUBLE IN WATER?

A.

PbCI2

B.

Pb(NO 3) 2

C.

PbSO4

D.

PbCO 3

View answer & explanation

Correct answer is B

No explanation has been provided for this answer.


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