Sulfur dioxide and oxygen react to form sulfur trioxide according to 2 SO₂(g) + O₂(g)…

CHEMISTRY · Multi-part · A Level · Chemistry · Gaseous equilibria (Kp) · Gaseous equilibria (Kp)

Problem

Sulfur dioxide and oxygen react to form sulfur trioxide according to 2 SO₂(g) + O₂(g) ⇌ 2 SO₃(g) For this reaction at a particular temperature,

K_p = 1.5 \times 10^{4}

. A sealed container at the same temperature is found to have the following partial pressures:

P_{\text{SO}_2} = 0.20\,\text{atm}

P_{\text{O}_2} = 0.10\,\text{atm}

P_{\text{SO}_3} = 0.05\,\text{atm}

A second researcher elects to write the chemical equation with all stoichiometric coefficients divided by 2. (a) Using the partial pressures given, calculate

Q_p

for the reaction as originally written. Show your calculation explicitly. (b) Compare the

Q_p

obtained in part (a) with

K_p

and predict the direction in which the reaction mixture will spontaneously shift. Explain your reasoning. (c) Calculate the value of the reaction quotient,

Q_{p,\text{scaled}}

, that corresponds to the alternative chemical equation written with all coefficients divided by 2. Use the same measured partial pressures. (d) State the numerical relationship between

Q_{p,\text{scaled}}

and the

Q_p

from part (a). Explain how this relationship is consistent with the way the equilibrium constant must be transformed for the scaled equation.

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