Changing the pressure
4 marks · NormalCarbon monoxide and hydrogen react according to the following equation:
How many moles of gaseous molecules are there on each side of the equation?
If the pressure is increased, what happens to the position of equilibrium? Explain your answer.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Left: 1 (CO) + 2 (H2) = 3 moles; Right: 1 mole (CH3OH) · must show Counts of gaseous molecules
(b) Equilibrium shifts to the right (towards methanol). Increasing pressure favours the side with fewer gas molecules. The right side has 1, the left has 3. · must show Shift to right, Explains in terms of fewer gas molecules, Links to increased pressure
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Marking points
B1 (a) · 1 mark · Counts moles of gas on each side correctly.
M1 (b) · 1 mark · Explains increased pressure favours side with fewer molecules.
M2 (b) · 1 mark · Identifies correct side with fewer gaseous molecules (right, CH3OH).
A1 (b) · 1 mark · Correctly predicts shift to the right/towards product.
Worked solution
a) Left: 1 + 2 = 3 moles of gas; Right: 1 mole of gas.
b) Increasing pressure favours the side with fewer gas molecules, which is the right (CH3OH). So equilibrium shifts to right.