WAEC Physics Past Questions & Answers - Page 169

841.

The temperature of 900cm3 of an ideal gas at a pressure of 114cm Hg is 27oC. Calculate its volume at 76cm Hg and 0oC

A.

50.0cm3

B.

546.0cm3

C.

659.3cm3

D.

1228.5cm3

Correct answer is D

\(V_2 = \frac{P_1V_1T_2}{T_1P_2} = \frac{114 \times 900 \times 273}{300 \times 76}\)

= 1228.5cm3

842.

On a basis of the kinetic theory, an increase in the temperature of a fixed volume of an ideal gas causes

A.

a incease in the number of gas molecules

B.

a decrease in the density of the gas

C.

an increase in the average speed of the gas molecules

D.

a decrease in pressure exerted by the gas

Correct answer is C

No explanation has been provided for this answer.

843.

A faulty barometer reads 72.6cm Hg when the atmospheric pressure is 75.0cm Hg. Calculate the atmospheric pressure when the barometer reads 72.0cm Hg

A.

79.4cm Hg

B.

74.38cm Hg

C.

74.2cm Hg

D.

69.4cm Hg

Correct answer is B

At 77cm Hg, A.P = \(\frac{75.0 \times 72.0}{72.6} = 74.38\)

844.

When a metal ball is heated through 30oC,its volume becomes 1.0018cm3. If the linear expansivity of the material of the ball is 2.0 x 10-5 K-1, calculate its original volume

A.

1.0000cm3

B.

1.0020cm3

C.

1.0036cm3

D.

1.0180cm3

Correct answer is A

\(V_1 = \frac{V_2}{3} = \frac{1.0018}{3 \times 2.0 \times 10^{-5} \times 30 + 1}\)

= 1cm3

845.

On a cold day, a concrete floor feels colder to the bare foot than a mat on the same floor because the

A.

is better conductor of heat than the foot

B.

mat loses heat to the bare foot at a faster rate

C.

mat is better conductor of heat than the floor

D.

concrete floor is a better conductor of heat than the mat

Correct answer is D

No explanation has been provided for this answer.