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WAEC Chemistry Past Questions & Answers - Page 73

361.

The vapour pressure of a liquid depends on:
I. Temperature II. rate of condensation III. Cohesive forces holding the particles together.

A.

I

B.

I and II

C.

I and III

D.

II and III

Correct answer is C

No explanation has been provided for this answer.

362.

The general gas equation was deprived from______?

A.

Boyle's and Gay Lussac's laws

B.

Boyle's and Graham's laws

C.

Boyle's and Charles' laws

D.

Dalton's atomic theory

Correct answer is C

No explanation has been provided for this answer.

363.

Consider the following reaction equation:
SO42-(aq) + 2H+(aq) + ye- SO42-(aq) + H2O(1).

The value of y in the equation is

A.

2

B.

3

C.

4

D.

6

Correct answer is A

From the reaction, the total charge on the left side = The total charge on the right side

-2 + 2 + y = -2 : y = -2 : y = 2

364.

The number of oxygen molecules present in 16.0g of the gas is ______?
[Avogadro's number = 6.02 x 1023]

A.

6.02 x 1022

B.

6.02 x 1023

C.

3.01 x 1023

D.

1.51 x 1023

Correct answer is C

1 mole = Molar mass of gas = Avogadros number
32g of O2 = 6.02 x 1023
16g of O2 = x
x = 16×6.02×102332 = 3.01 x 1023

365.

Consider the following reaction equation:
C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(g)

The volume of CO2(g) produced at s.t.p when 0.05 moles of C2H4(g) was burnt in O2(g) is
[Molar Volume of gas = 22.4dm3

A.

1.12dm3

B.

2.24dm3

C.

3.72dm3

D.

4.48dm3

Correct answer is B

volumemolar volume = 0.05

1 mole of ethane produces 2 moles of carbon(iv)oxide

∴ 0.05  mole of ethane will produce x moles of carbon(iv)oxide

= volume22.4 = 0.05 X 2 X 22.4 =  2.24dm3