WAEC Past Questions and Answers - Page 1304

6,516.

When air in a syringe is compressed such that there is no change in temperature, the

A.

air liquefies

B.

pressure increases

C.

intermolecular space increases

D.

density decreases

Correct answer is B

Since the temperature of air remain constant.So, it is a isothermal process.
PV=K
This eq. shows that on increasing pressure, the volume gets reduced and vice-versa.
Since the syringe is slowly compressed, volume is decreasing.
Therefore, the pressure inside the syringe will increases because the molecules now hit the syringe walls more frequently.

6,517.

Consider the following reaction equation
N\(_{2}\)(g) + 3H\(_{2(g)}\)  ⇌ 2NH3(g) ∆H = -92kJ

Increasing the temperature of the reaction would

A.

shift the equilibrium to the right

B.

increase the yield of ammonia

C.

decrease the amount of hydrogen

D.

decrease the yield of ammonia

Correct answer is D

In this case, an increase in in temperature will cause the equilibrium position to shift to the left thereby decreasing the yield of ammonia.

6,518.

Which of the following statements about an equilibrium system is correct?

A.

Forward and backward reactions occur at the same rate

B.

The concentrations of reactants must equal that of the products

C.

The concentrations of, reactants and products can be changed by adding a catalyst,

D.

The concentrations of reactants and products are not affected by a change in temperature

Correct answer is A

Equilibrium is a state of a system where there is no observable change in the properties of the system with respect to time

6,519.

Which of the following gases is alkaline?

A.

NO\(_{2}\)

B.

CO\(_{2}\)

C.

NH\(_{3}\)

D.

N\(_{2}\)O

Correct answer is C

Alkaline gases are any gaseous compounds that form an alkali (or basic) solution with a pH greater than 7 when dissolved in water. Ammonia is the most common alkaline gas

6,520.

Graphite is used as a dry lubricant due to the presence of

A.

mobile electrons

B.

free electrons

C.

octahedral structures

D.

layered structures

Correct answer is D

Graphite is an excellent dry lubricant. This is because its layered structure allows one layer to slide over another easily. It is non-volatile and not sticky.