JAMB Chemistry Past Questions & Answers - Page 52

256.

Consider the reaction
A\(_{(s)}\) + 2B\(_{(g)}\) → 2C\(_{(aq)}\) + D\(_{(g)}\)
What will be the effect of a decrease in pressure on the reaction?

A.

the equilibrium will shift

B.

rate of forward reaction will increase

C.

rate of backward reaction will increase

D.

rates of forward and backward reaction are not affected

Correct answer is C

Given: The equation below
A\(_{(s)}\) + 2B\(_{(g)}\) → 2C\(_{(aq)}\) + D\(_{(g)}\)

According to Le Chatelier's Principle:

Pressure changes affects only the gaseous reactants and products
There must be different amount of gaseous particles on both sides.

Generally; a decrease in the pressure shifts the equilibrium position in favor of the side with larger volume of gases.

I.e  rates of backward reaction.

257.

Which of the following represents the kind of bonding present in ammonium chloride?

A.

ionic only

B.

covalent only

C.

ionic and covalent

D.

dative covalent

Correct answer is C

No explanation has been provided for this answer.

259.

By what amount must the temperature of 200cm\(^3\) of Nitrogen at 27°C be increased to double the pressure if the final volume is 150cm\(^3\) (Assume ideality)

A.

150°C

B.

177°C

C.

75°C

D.

120°C

Correct answer is A

Parameters given:

V\(_1\) = 200 cm\(^3\); T\(_1\) = 27 + 273 = 300K.

V\(_2\) = 150 cm\(^3\); T\(_2\) = ?

P\(_2\) = 2P\(_1\).

Using the Ideal Gas Equation:

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

\(\frac{P_1 \times 200}{300} = \frac{2P_1 \times 150}{T_2}\)

\(\frac{2}{3} = \frac{300}{T_2}\)

T\(_2\) = 450K.

= 450K - 273K

= 177°C

177 - 27 = 150

That is the amount by which T1 must be increased.