STUDENT SPACE · TOPIC 5

Changing equilibrium conditions

Predict and explain the effects of changed conditions.

The essentials

Adding a reactant favours its consumption and increases the equilibrium amount of product.
Increasing pressure by reducing volume favours the side with fewer moles of gas.
Increasing temperature favours the endothermic direction. Decreasing it favours the exothermic direction.

Try each question before opening its hint or answer. Use paper for calculations and diagrams.

Does adding a catalyst increase equilibrium yield? Explain.

Need a hint for Question 1?

Underline gaseous coefficients for pressure, and label the endothermic direction for temperature.

Check Question 1

No. Both directions speed up and the equilibrium position stays the same.

For H₂(g) + I₂(g) ⇌ 2HI(g), predict the effect of increased pressure on equilibrium position.

Need a hint for Question 2?

Count the gaseous coefficients on each side.

Check Question 2

No shift due to pressure: two moles of gas on each side.

For N₂(g) + 3H₂(g) ⇌ 2NH₃(g), what happens when ammonia is removed from an equilibrium mixture? Explain the shift.

Need a hint for Question 3?

The system responds by opposing removal of a product.

Check Question 3

Removal favours the forward reaction and allows more ammonia to form.

Use Lesson 5 in your worksheet for written practice. Your teacher will discuss those answers in class.