Free Printable IB chemistry topic 7 practice questions

1.

Which statement about chemical equilibria implies they are dynamic?

a)

The position of equilibrium constantly changes.

b)

The rates of forward and backward reactions change.

c)

The reactants and products continue to react.

d)

The concentrations of the reactants and products continue to change.

2.

The reaction below represents the Haber process for the industrial production of ammonia.
$N_{2\ }+\ 3\ H_{2\ }\Longleftrightarrow\ 2NH_3\ \ \ \ \ \Delta H=-92\ \frac{kJ}{mol}$
The optimum conditions of temperature and pressure are chosen as a compromise between those that favour a high yield of ammonia and those that favour a fast rate of production. Economic considerations are also important. Which statement is correct?

a)

A higher temperature would ensure a higher yield and a faster rate.

b)

A lower pressure would ensure a higher yield at a lower cost.

c)

A lower temperature would ensure a higher yield and a faster rate.

d)

A higher pressure would ensure a higher yield at a higher cost.

3.

$2H_{2\ }(g)+CO\ (g)\ \Longleftrightarrow CH_3OH\ (l)\ \ \ \ \Delta\ H=−128\ \frac{kJ}{mol}$

What is the effect of an increase of temperature on the yield and the equilibrium constant for the
following reaction?

a)

Yield: increases; K: increases

b)

Yield: increases; K: decreases

c)

Yield: decreases; K: increases

d)

Yield: decreases; K: decreases

4.

Consider the equilibrium between methanol, CH3OH(l), and methanol vapour, CH3OH(g).
$CH_3OH\ (l)\ \Longleftrightarrow\ CH_3OH\ (g)$
What happens to the position of equilibrium and the value of $K_c$ as the temperature decreases?

a)

Position of equilibrium shifts to the left, $K_c$ decreases.

b)

Position of equilibrium shifts to the left, $K_c$ increases.

c)

Position of equilibrium shifts to the right, $K_c$ decreases.

d)

Position of equilibrium shifts to the right, $K_c$ increases.

5.

$I_2\ (g)+Br_2\ (g)\ \Longleftrightarrow\ 2IBr\ (g)$

0.50 mol of I2(g) and 0.50 mol of Br2(g) are placed in a closed fl ask. The following equilibrium is
established.

The equilibrium mixture contains 0.80 mol of IBr(g). What is the value of $K_c$ ?

a)

0.64

b)

1.3

c)

2.6

d)

64

6.

$PCl_5\ (s)\ \Longleftrightarrow\ PCl_3\ (l)+Cl_2\ (g)$

An increase in temperature increases the amount of chlorine present in the following equilibrium.

What is the best explanation for this?

a)

The higher temperature increases the rate of the forward reaction only.

b)

The higher temperature increases the rate of the reverse reaction only.

c)

The higher temperature increases the rate of both reactions but the forward reaction isaffected more than the reverse.

d)

The higher temperature increases the rate of both reactions but the reverse reaction isaffected more than the forward.

7.

$Cr_2O_7^{2-}\ (aq)+H_2O\ (l)\ \Longleftrightarrow\ 2CrO_4^{2-}\ (aq)+2H^+\ (aq)$ What will happen to the position of equilibrium and the value of $K_c$ when more $H^+$ ions are added at constant temperature?

a)

Position of equilibrium shifts to the left; $K_c$ decreases.

b)

Position of equilibrium shifts to the right; $K_c$ increases.

c)

Position of equilibrium shifts to the right; $K_c$ does not change.

d)

Position of equilibrium shifts to the left; $K_c$ does not change.

8.

Consider this equilibrium reaction in a sealed container:
$H_2O\ (g)\ \Longleftrightarrow\ H_2O\ (l)$
What will be the effect on the equilibrium of increasing the temperature from 20 °C to 30 °C?

a)

More of the water will be in the gaseous state at equilibrium.

b)

More of the water will be in the liquid state at equilibrium.

c)

At equilibrium the rate of condensation will be greater than the rate of evaporation.

d)

At equilibrium the rate of evaporation will be greater than the rate of condensation.

9.

Which statement is correct for the equilibrium:

H_2O\ \left(l\right)\ \Longleftrightarrow\ H_2O\ \left(g\right)

in a closed system at 100 °C?

a)

All the H2O(l) molecules have been converted to H2O(g).

b)

The rate of the forward reaction is greater than the rate of the reverse reaction.

c)

The rate of the forward reaction is less than the rate of the reverse reaction.

d)

The pressure remains constant.

IB chemistry topic 7 practice questions

Total questions: 9

Worksheet time: 18mins

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