At 700 ºC, the equilibrium constant, K_c, for the reaction is 1.075 × 10⁸.

2H₂ (g) + S₂ (g) \( \rightleftharpoons \) 2H₂S (g)

Which relationship is always correct for the equilibrium at this temperature?

A. [H₂S]² < [H₂]² [S₂]

B. [S₂] = 2[H₂S]

C. [H₂S] < [S₂]

D. [H₂S]² > [H₂]²[S₂]

D

1.0 mol of N₂(g), 1.0 mol of H₂(g) and 1.0 mol of NH₃(g) are placed in a 1.0 dm³ sealed flask and left to reach equilibrium. At equilibrium the concentration of N₂(g) is 0.8 mol dm⁻³.

N₂(g) + 3H₂(g) \( \rightleftharpoons \) 2NH₃(g)

What are the equilibrium concentration of H₂(g) and NH₃(g) in mol dm⁻³?

B

The equation for the reaction between two gases, A and B, is:

\[{\text{2A(g)}} + {\text{3B(g)}} \rightleftharpoons {\text{C(g)}} + {\text{3D(g)}}\]

When the reaction is at equilibrium at 600 K the concentrations of A, B, C and D are 2, 1, 3 and 2 \({\text{mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) respectively. What is the value of the equilibrium constant at 600 K?

A.     \(\frac{1}{6}\)

B.     \(\frac{9}{7}\)

C.     3

D.     6

D

Components X and Y are mixed together and allowed to reach equilibrium. The concentrations of X, Y, W and Z in the equilibrium mixture are 4, 1, 4 and \({\text{2 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) respectively.

X + 2Y \( \rightleftharpoons \) 2W + Z

What is the value of the equilibrium constant, K_c?

A.     \(\frac{1}{8}\)

B.     \(\frac{1}{2}\)

C.     2

D.     8

D

A mixture of 2.0 mol of \({{\text{H}}_{\text{2}}}\) and 2.0 mol of \({{\text{I}}_{\text{2}}}\) is allowed to reach equilibrium in the gaseous state at a certain temperature in a \({\text{1.0 d}}{{\text{m}}^{\text{3}}}\) flask. At equilibrium, 3.0 mol of HI are present. What is the value of \({K_{\text{c}}}\) for this reaction?

\[{{\text{H}}_{\text{2}}}{\text{(g)}} + {{\text{I}}_{\text{2}}}{\text{(g)}} \rightleftharpoons {\text{2HI(g)}}\]

A.     \({K_{\text{c}}} = \frac{{{{(3.0)}^2}}}{{{{(0.5)}^2}}}\)

B.     \({K_{\text{c}}} = \frac{{3.0}}{{{{(0.5)}^2}}}\)

C.     \({K_{\text{c}}} = \frac{{{{(3.0)}^2}}}{{{{(2.0)}^2}}}\)

D.     \({K_{\text{c}}} = \frac{{{{(0.5)}^2}}}{{{{(3.0)}^2}}}\)

A

What is the relationship between \({\text{p}}{K_{\text{a}}}\), \({\text{p}}{K_{\text{b}}}\) and \({\text{p}}{K_{\text{w}}}\) for a conjugate acid–base pair?

A.     \({\text{p}}{K_{\text{a}}} = {\text{p}}{K_{\text{w}}} + {\text{p}}{K_{\text{b}}}\)

B.     \({\text{p}}{K_{\text{a}}} = {\text{p}}{K_{\text{w}}} - {\text{p}}{K_{\text{b}}}\)

C.     \({\text{p}}{K_{\text{a}}} \times {\text{p}}{K_{\text{b}}} = {\text{p}}{K_{\text{w}}}\)

D.     \(\frac{{{\text{p}}{K_{\text{a}}}}}{{{\text{p}}{K_{\text{b}}}}} = {\text{p}}{K_{\text{w}}}\)

B

The indicator, HIn is used in a titration between an acid and base. Which statement about the dissociation of the indicator, HIn is correct?

\[{\text{HIn(aq)}} \rightleftharpoons {{\text{H}}^ + }{\text{(aq)}} + {\text{I}}{{\text{n}}^ - }{\text{(aq)}}\]

colour A                             colour B

A.     In a strongly alkaline solution, colour B would be observed.

B.     In a strongly acidic solution, colour B would be observed.

C.     \({\text{[I}}{{\text{n}}^ - }{\text{]}}\) is greater than [HIn] at the equivalence point.

D.     In a weakly acidic solution colour B would be observed.

A

When gaseous nitrosyl chloride, NOCl (g), decomposes, the following equilibrium is established:

\[{\text{2NOCl(g)}} \rightleftharpoons {\text{2NO(g)}} + {\text{C}}{{\text{l}}_2}{\text{(g)}}\]

2.0 mol of NOCl(g) were placed in a \({\text{1.0 d}}{{\text{m}}^{\text{3}}}\) container and allowed to reach equilibrium. At equilibrium 1.0 mol of NOCl(g) was present. What is the value of \({K_{\text{c}}}\)?

A.     0.50

B.     1.0

C.     1.5

D.     2.0

A

A mixture of 0.40 mol of CO (g) and 0.40 mol of H₂ (g) was placed in a 1.00 dm³ vessel. The following equilibrium was established.

CO (g) + 2H₂ (g)  CH₃OH (g)

At equilibrium, the mixture contained 0.25 mol of CO (g). How many moles of H₂ (g) and CH₃OH (g) were present at equilibrium?

D

C

The graph shows values of ΔG for a reaction at different temperatures.

Which statement is correct?

A.     The standard entropy change of the reaction is negative.

B.     The standard enthalpy change of the reaction is positive.

C.     At higher temperatures, the reaction becomes less spontaneous.

D.     The standard enthalpy change of the reaction is negative.

B