The gas-phase equilibrium 2 , SO _ 2 (g)+ 1 2 , O _ 2 (g) 2 , SO _ 3 (g) has (K_ p…

CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)

Problem

The gas-phase equilibrium

2\,\text{SO}_{2}(g)+\tfrac{1}{2}\,\text{O}_{2}(g)\rightleftharpoons 2\,\text{SO}_{3}(g)

has

K_{p}=3.4

at 1000 K. A 1.00-L rigid vessel at this temperature contains an equilibrium mixture with partial pressures P(SO

_{2}

) = 0.60 atm, P(O

_{2}

) = 0.20 atm, P(SO

_{3}

) = 0.80 atm. The volume of the vessel is then instantaneously reduced to 0.50 L while the temperature is held constant. (a) Calculate the value of the reaction quotient

Q_{p}

immediately after the compression. (b) Indicate the direction of the subsequent net reaction as the system re-establishes equilibrium. (c) Provide a chemical justification for your prediction in part (b) that cites both the calculated

Q_{p}

and the difference in the total number of moles of gas on each side of the balanced equation.

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