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Flashcards in Equilibrium Deck (16):
1

Definition of equilibrium law

For the equilibrium aA + bB cC + dD

Kc = [C]c[D]d/[A]a[B]b

2

What are the units of Kc

Vary

3

What is inferred by Kc value greater than 1?

The reaction is product favoured, the products on the right predominate at equilibrium

4

What does Kc value lower than 1 mean?

Reaction is reactant-favoured, reactants on the left predominade at equilibrium

5

How does temp. change affect Kc?

When the forward reaction is exothermic, as temp. increases, Kc decreases.

When the forward reaction is endothermic, as temp. increases Kc also increases.

6

How does Kc change?

Only when temp. is altered

7

Characterisitcs of equation at equilibrium

Rates of forward and reverse reactions are equal

Closed system

Constant conc. of reactants and products

Reversible reaction

8

Equation for reaction between methane and steam to produce hydrogen 

CH3 + H2O --> 3H2 + CO

9

A process that may be used in future to obtain hydrogen gas for the haber process

Electrolysis of water

10

Haber process: fewer mole of gas on right. Pressure is increased, explain in terms of Kc why the equilibrium yield of ammonia increases

Kc value does not change, increased pressure increases concentration terms on bottom of Kc expression more than the top. System is now no longer in equilibrium. Top of Kc expression increases and bottom decreases until Kc is reached

11

Reaction between ammonia and oxygen to form nitrogen monoxide

4NH3 + 5O2 --> 4NO + 6H2O

12

How does addition of a catalyst affect equilibrium?

No effect as it affects both forward and backwards reaction equally

13

What is meant by dynamic equilibrium?

The equilibrium that exists in a closed system where the rate of the forward reaction is equal to the reverse reaction

14

When can you just use moles rather than conc. in a Kc expression?

When volume cancels out because same number of products and reactants

15

Why could equilibrium constant be different to data book value?

Equilibrium had not been reached yet

16