WAEC Chemistry Past Questions & Answers - Page 126

626.

Which of the following gases are arranged in increasing order of diffusion rate? [H = 1 .0; C = 12; N = 14; O = 16; S = 32]

A.

SO 2 O2, NH3 H2

B.

H2S,NH2,O2,SO2

C.

72001934

D.

NH3,NO2,N2,CO2

Correct answer is A

No explanation has been provided for this answer.

627.

The pressure exerted by a gas is a function of the

A.

total volume of the gas

B.

speed of the gaseous molecules

C.

mass of each gaseous molecule

D.

frequency of collision between gaseous molecules

Correct answer is D

No explanation has been provided for this answer.

628.

Which of the following phenomenna lead to decrease in volume of a liquid in an open container?

A.

Brownian motion

B.

Diffusion

C.

Evaporation

D.

Sublimation

Correct answer is C

No explanation has been provided for this answer.

629.

The gas law which describes the relationship between volume and temperature is

A.

Boyle's law

B.

Charles' law

C.

Dalton's law

D.

Graham's law

Correct answer is B

No explanation has been provided for this answer.

630.

The percentage by mass of calcium in Ca(OCI)2 is [Ca = 40.0; CI = 35.5; O = 16.0]

A.

28.0%

B.

31.6%

C.

43.8%

D.

44.5%

Correct answer is A

Molar mass of \(Ca(OCl)_2\) = 40 + (16 + 35.5)x2 = 143

% by mass of calcium in the compound =\(\frac{mass  of  calcuim}{molar  mass  of  compound}\) x 100%

% calcium = \(\frac{40}{143} \times100\)

  = 27.98% = 28%