Reversible reactions in a sealed container
3 marks · NormalA sample of solid ammonium chloride, , is heated in a sealed tube. The decomposition reaction is:
Suppose you start with 0.80 mol of in the tube. After reaching equilibrium, 0.32 mol of remains.
Calculate the amount (in mol) of ammonia gas, , present at equilibrium.
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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0.48 mol (±0.01)
Also accept: 0.48
Common mistakes: Subtracting incorrectly, e.g., giving 0.32 as the answer instead of the difference.
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Marking points
M1 · 1 mark · States or uses the correct relation: amount decomposed = initial amount - equilibrium amount.
M2 · 1 mark · Recognizes that the amount of formed equals the amount of decomposed (1:1 ratio).
A1 · 1 mark · Gives the correct final value: 0.48 mol .
Worked solution
Amount of ammonium chloride decomposed:
The balanced equation shows that 1 mol produces 1 mol .
So, moles of at equilibrium = 0.48 mol.