CAIE A-Level Chemistry 7.1.9 Factors Affecting Equilibrium Constants

Practise distinguishing changes that shift equilibrium position from the temperature change that alters Kc or Kp.

Exam points

state that only temperature changes the value of Kc or Kp for a specified equilibrium reaction
state that pressure or concentration may shift composition but does not change K at constant temperature
state that a catalyst changes the rate of reaching equilibrium but not K or the equilibrium composition

[Maximum number: 1]

Hydrogen halides are compounds formed when halogens (Group 17 elements) react with hydrogen. The bond polarity of the hydrogen halides decreases from HF to HI.

Some relevant data are shown in the table.

Table for Question 7.1.9—Whether changes in temperature, concentration question 1 — CAIE A-Level Chemistry AS

Hydrogen chloride undergoes a reversible reaction with oxygen.

4 \mathrm{HCl}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{Cl}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{~g})

The reaction is carried out at $400^{\circ} \mathrm{C}$ in the presence of a copper(II) chloride catalyst.

The reaction is repeated without a catalyst.

State the effect of this on $K_{\mathrm{p}}$ .

$K_p$ would not change.

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7.1.9—Whether changes in temperature, concentration question 1