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CfE Higher Chemistry Unit 3 > Equilibria > Flashcards

Flashcards in Equilibria Deck (15)
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1

What does this symbol mean?

This means that it is a reversible reaction where the reactants form products, which react together to give the reactants back.

2

Why can equilibrium only be reached in a closed system?

None of the reactants or products are lost.

In an open system, products (or reactants) are lost, therefore equilibrium cannot be established.

3

Describe the concentrations of reactants and products at equilibrium.

At equilibrium, the concentration of reactant and products remain constant but NOT always equal.

4

Describe the rates of the forward and reverse reactions at equilibrium.

They take place at equal rates.

5

To maximise profits, chemists employ strategies to move the position of equilibrium to the left or the right?

To the right in favour of the products.

6

Name a reaction condition which will affect the position of equilibrium.

  1.  the addition or removal of reactants or products
  2. altering temperature
  3. altering pressure

7

What happens when a system at equilibrium is subjected to a change?

The system will adjust itself to counteract the applied change.

8

What way will the equilibrium lie in the following reaction if:

More Fe3+(aq) is added

 

Fe3+(aq) + CNS-(aq) ⇌ FeCNS2+(aq)

1. Equilibrium will shift to the right and make more products.

 

9

What way will the equilibrium lie in the following reaction if:

  1. More FeCNS2+(aq)

Fe3+(aq) + CNS-(aq) ⇌ FeCNS2+(aq)

1. Equilibrium will shift to the left and make more reactants.

10

In the Haber process the forward reaction is an exothermic reaction.

N2(g) + 3H2 ⇌ 2NH3(g)             ΔHforward is negative

Which way will the equilbrium shift if the temperature is increased?

If the temperature is increased, then the equilibrium will shift to the left (the endothermic direction), to remove the extra heat added. 

11

In the Haber process the forward reaction is an exothermic reaction.

N2(g) + 3H2 ⇌ 2NH3(g)             ΔHforward is negative

Which way will the equilbrium shift is the temperature is decreased?

If the temperature is decreased, then the equilibrium will shift to the right (the exothermic direction), to replace the heat removed. 

12

In the Haber process

N2(g) + 3H2(g) ⇌ 2NH3(g)

Explain the change in the position of equilibrium when the pressure is increased.

An increase in pressure would move the equilibrium to the right since there are a smaller number of moles of gas products than reactants.

13

In the Haber process

N2(g) + 3H2(g) ⇌ 2NH3(g)

Explain the change in the position of equilibrium when the pressure is decreased.

A decrease in pressure would move the equilibrium to the left since there are a larger number of moles of gas reactants than gas.

14

Why would changing pressure have no effect on the following reaction?

H2(g) + I2(g) ⇌​ 2HI(g)

Both sides of the reaction have two moles of gases, so changing the pressure does not favour either side of the equilibrium.

15

What effect would adding a catalyst to a reversible reaction have on the equilibrium?

Adding catalyst has no effect on the position of equilibrium.

Allows equilibrium to be reached more quickly, or established at a lower temperature