Question 4
FAmmonium chloride is a white solid. When ammonium chloride is heated, it breaks down into two gases, ammonia and hydrogen chloride.
When the two gases are cooled, they react together to make ammonium chloride again.
A student heats some ammonium chloride at the bottom of a test tube. After a few minutes, a white solid forms on the cooler part of the tube, near the top.
The diagram shows the apparatus.
a.[2]
Complete the word equation for the reaction. Write the correct symbol in the first gap.
ammonium chloride ...... ammonia + ......
b.[1]
State how the conditions are changed to make the reaction go in the reverse direction.
c.[2]
Which two statements about a reaction at dynamic equilibrium are correct?
Statement 1: It can only happen in a closed system.
Statement 2: The forward and reverse reactions have both stopped.
Statement 3: The rate of the forward reaction is equal to the rate of the reverse reaction.
Statement 4: There are always equal amounts of reactants and products.
Statement 5: Only the forward reaction is happening.
Write the numbers of the two correct statements.
d.[2]
The student's test tube is open at the top.
Explain why the reaction in the open test tube cannot reach dynamic equilibrium.
e.[1]
Ammonia and hydrogen chloride are both harmful gases.
Suggest one safety precaution the student should take because of these gases.
5.3 Equilibria Questions
47 exam-style questions on OCR GCSE Chemistry 5.3 Equilibria, covering 5.3.1 Reversible reactions and dynamic equilibrium and 5.3.2 Changing the position of equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.