Back to AI Flashcard MakerChemistry /OCR A-Level Chemistry: Chapter 19 - Equilibrium

OCR A-Level Chemistry: Chapter 19 - Equilibrium

Chemistry17 CardsCreated 2 months ago

This flashcard set explains how to determine units for the equilibrium constant Kc, distinguishes between homogeneous and heterogeneous equilibria, and outlines key gas-phase concepts like mole fraction and partial pressure used in equilibrium calculations.

How are the units of Kc worked out?

Substitute units into the expression

Cancel common units

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Key Terms

Term
Definition

How are the units of Kc worked out?

Substitute units into the expression

Cancel common units

What is a homogeneous equilibrium?

Equilibrium species all have the same state.


What is a heterogeneous equilibrium?

Equilibrium species that have different states.

In a heterogeneous equilibrium, what is discounted in the expression for Kc?

Any species that are not as a gas or in solution.

What is a mole fraction?

The proportion of the volume of a gas to the total volume of gases in the mixture.

What is the partial pressure?

The contribution that the gas makes towards the total pressure P.

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TermDefinition

How are the units of Kc worked out?

Substitute units into the expression

Cancel common units

What is a homogeneous equilibrium?

Equilibrium species all have the same state.


What is a heterogeneous equilibrium?

Equilibrium species that have different states.

In a heterogeneous equilibrium, what is discounted in the expression for Kc?

Any species that are not as a gas or in solution.

What is a mole fraction?

The proportion of the volume of a gas to the total volume of gases in the mixture.

What is the partial pressure?

The contribution that the gas makes towards the total pressure P.

How is a mole fraction calculated?

Mole fraction χ(A) = n(A)/n(total)

How is partial pressure calculated?

p(A) = mole fraction x total pressure P

p(A) = χ(A) x P

What is the way to check the partial pressures are correct?

Sum of the partial pressures equals the total pressure.

With the equilibrium H(2) + I(2) 2HI, what is the expression for Kp?

Kp = p(HI)^2 / p(H(2)) x p(I(2))

What does the magnitude of an equilibrium constant represent?

The extent of an equilibrium

What would K=1, K=100 and K=0.01 represent?

K=1: equilibrium halfway between reactants and products
K=100: equilibrium in favour of products
K=0.01: equilibrium in favour of reactants

What is the effect on K when the temperature is increased and the forward reaction is exothermic?

Equilibrium constant decreases

Equilibrium shifts to reactant side

What is the effect on K when the temperature is increased and the forward reaction is endothermic?

Equilibrium constant increases

Equilibrium shifts to product side

What effect does increasing pressure have on a reaction with fewer moles of gaseous products than reactants?

Products increase
Reactants decrease
Equilibrium shifts to right

What effect does increasing pressure have on a reaction with the same number of moles of gaseous products and reactants?

No change

Equilibrium stays the same

What is the effect of a catalyst on the equilibrium constant?

Catalysts affect the rate but not the equilibrium position.

Equilibrium is reached faster but position does not change.