The effect of concentration
2 marks · HardFor the equilibrium reaction below:
Explain, in terms of concentration, what happens to the position of equilibrium if some B(g) is removed from the mixture.
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Show answer
The position of equilibrium shifts to the right (towards products). Removing B(g) reduces its concentration, so the system makes more B (and C) from A to replace it.
Also accept: Equilibrium shifts towards products to replace B(g)
Common mistakes: No change; Shifts left (wrong direction)
Show mark scheme and worked solution
Marking points
C1 · 1 mark · States equilibrium shifts to the right/produces more products.
C2 · 1 mark · Explains that removing B(g) lowers its concentration, so the system forms more B (and C) from A to replace it.
Worked solution
Removing B(g) decreases its concentration. The equilibrium shifts right, converting A(g) into more B(g) and C(g) to replace the B(g) that was removed.