Reversible reactions in a sealed container
2 marks · HardIn an experiment, solid ammonium chloride is heated in a sealed tube. Name the two gases that form, and state what happens when they meet in a cooler part of the tube.
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Also accept: NH3 and HCl; ammonia gas and hydrogen chloride gas
Common mistakes: Omitting second product (or naming only one); Saying gases 'disappear' rather than forming the solid
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Marking points
B1 · 1 mark · Correctly names both ammonia and hydrogen chloride as the gases formed.
B2 · 1 mark · States that the gases recombine in the cooler part to form a white solid/ammonium chloride.
Worked solution
The two gases are ammonia (NH3) and hydrogen chloride (HCl). When they meet in the cooler part of the tube, they react to form solid ammonium chloride (NH4Cl), which is a white solid.