Equilibrium exam questions for HSC Chemistry

In this chemistry paper you will have to answer a series of equilibrium exam questions which relate to chemical equilibrium as covered in module 5 of the HSC chemical equilibrium module.

Equilibrium exam questions

All up these equilibrium exam questions are worth 26 marks and should be answered in 50 minutes. Make sure you mark you answers to get the most from your study time.


Question 1.

a)

Using collision theory, explain how temperature, catalysis and pressure affect equilibrium position in the Haber process [3 marks]

b)

Explain how you can use Le Chatelier’s principles to maximise how much ammonia you are able to produce [4 marks]


Question 2.

A student has a sealed gas container. They know that this originally contained pure nitrogen dioxide, however, they suspect there might be a contaminant since the sealed gas container has gone a dark brown colour.

Equilibrium exam questions equation of  nitrogen dioxide decomposition

NO2 gas is a dark brown colour

N2O4 gas is colourless

The student conducted an experiment dunking the sealed glass container into a bowl of boiling water and then into a bowl of ice cold water.

Observations made by the student:

  • Cooling the sealed reaction vessel made the gas turn transparent
  • Heating the sealed reaction vessel made the gas turn dark brown

a)

Develop a risk assessment for the above experiment [3 marks]

b)

Justify whether this experiment is endothermic or exothermic, using experimental evidence to support your answer [4 marks]

c)

Outline a suitable aim for this experiment [2 marks]

d)

Evaluate the reliability of this experiment [3 marks]

e)

What do you expect to happen when the student adds argon to the sealed reaction vessel, justify using collision theory and le Chatelier’s principles. [3 marks]

f)

Outline a conclusion from the experiment based on your aim and the results of the students experiment [2 marks]


Question 3.

At equilibrium, a 2.00 L vessel contains 0.0860 mol of H2, 0.1240 mol of I2, and 0.0716 mol of HI. The system can be represented with the following equilibrium equation

What is the Keq for this system? [2 marks]

Answers to equilibrium exam questions

Question 1.

Increasing the temperature will increase both the rate of the forward reaction and reverse reaction.

Since the reverse reaction is endothermic, it will increase this more. Additionally, increasing the pressure will increase the number of successful collisions leading to a reaction, hence pushing equilibrium to the right since there will be fewer ammonia molecules to collide and lead to a favourable reaction. Adding the iron catalyst will increase both the rate of forward and reverse reactions equally hence no effect on equilibrium position, just the time to reach equilibrium.

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