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Flashcards in Chemical Equilibrium Deck (15)
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1

Higher recap

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

The system will adjust itself to counteract the applied change.

Le Chatelier's principle

2

The point when the rates of the forward and reverse reactions in a reversible reaction are equal is known as?

 Equilibrium 

3

What is meant by dynamic (or moving) equilibrium?

At equilibrium the forward and reverse reactions still continue, but at the same rate.

4

If [reactants]>[products], the position of equilibrium is said to lie to which side?

Left-hand side

5

If [products]>[reactants], the position equilibrium is said to lie to which side?

Right-hand side

6

The position of the equilibrium can be measured using K.

What is K?

K is the equilibrium constant

7

Consider the reaction represented by the equation

aA + bB ⇌ cC + dD

where A and B are reactants, C and D are products and a, b, c and d are the stoichiometric coefficients in a balanced reaction equation. 
In terms of concentration, the equilibrium constant can be expressed as?

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

8

What are the units for the equilibrium constant?

No units

9

Consider the ionisation of ethanoic acid

CH3COOH ⇌ H+ + CH3COO-

How would the equilibrium constant be expressed?

K =  [H+] [CH3COO-]​ / [​CH3COOH​]​

10

CH3COOH ⇌ H+ + CH3COO-

If sodium ethanoate solid was added, what would happen to

1) the position of equilibrium?

2) the pH?

1) Equilibrium would shift to the left

2) pH would increase

This is because of a reaction between H+(aq) and CH3COO-(aq) ions to make CH3COOH(aq)

11

The dissociation of ethanoic acid has an equilibrium constant of 1.7x10-5 

Does equilibrium lie to the left or the right?

 

Calculating the equilibrium constant is done by the products divided by the reactants. A constant less than 1 must means more reactants than product, therefore equilibrium to the left.

12

The conversion of ozone to oxygen has an equilibrium constant of 1x1055 

Does equilibrium lie to the left or the right?

 

Calculating the equilibrium constant is done by the products divided by the reactants. 

A number larger than 1 must mean more products than reactants, therefore, equilibrium to the right.

13

The decomposition of hydrofluoric acid has an equilibrium constant of 1x10-13 

Does equilibrium lie to the left or the right?

 

Calculating the equilibrium constant is done by the products divided by the reactants. A number smaller than 1 must mean more reactants than products, therefore, equilibrium to the left.

14

An equilibrium mixture of gaseous O2, NO and NO2 at 500 K contains 1.0 x 10-3 moll-1 O2, 1.9 x 10-3 moll-1 NO and 5.0 x 10-2 moll-1 NO2. Calculate the value of K.

O2 + 2NO ⇌ 2NO2

K = [NO2]2/[NO]2[O2]

K = (5.0x10-2)2 / (1.9x10-3)(1.0x10-3)

= 6.9x105

15