JAMB Chemistry Past Questions & Answers - Page 198

987.

An increase in the pressure exerted on gas at a constant temperature results in

A.

a decrease in the number of effective collisions

B.

a decrease in volume

C.

an increase in the average intermolecular distance

D.

an increase in volume

Correct answer is B

No explanation has been provided for this answer.

988.

50 cm\(_3\) of gas was collected over water at 10ºC and 765 mm Hg. Calculate the volume of the gas at s.t.p. if the saturated vapour pressure of water at 10ºC is 5mm Hg

A.

49.19 cm 3

B.

48.87 cm 3

C.

48.55 cm 3

D.

48.23 cm 3

Correct answer is D

General Gas Equation:

\(\frac{P_1 V_1}{T_1}\) = \(\frac{P_2 V_2}{T_2}\)

where P\(_1\) = 765 - 5 = 760mmhg

\(V_2 = \frac{P_1 V_1 T_2}{P_2 T_1}\) 

\(V_2 = \frac{760 * 50 * 273}{ 760 * 283}\) → 48.23cm\(^3\)

989.

How many atoms are present in 6.0g of magnesium?
[Mg = 24, NA = 6.02 x 1023 mol-1]

A.

1.20 x 1022

B.

2.41 x 1022

C.

1.51 x 1023

D.

3.02 x 1023

Correct answer is C

No explanation has been provided for this answer.

990.

Which of the following methods can be used to obtain pure water from a mixture of sand, water and methanoic acid?

A.

netralization with NaOHfoolowed by filtration

B.

neutralization with NaOH followed by distillation

C.

fractional distillation

D.

filtration followed by distillation

Correct answer is D

No explanation has been provided for this answer.