Y1 Chemical Equilibrium (P)

Question 1

Go to completion

Answer 1

Reactions that convert 100% of reactants in to products

Question 2

Reversible

Answer 2

Where both the forward and backward reactions occur at the same time, this means the reaction mixture contains both ‘Reactants’ and ‘Products’

Question 3

What is required for the equilibrium to be established?

Answer 3

A closed system- no matter gained or lost from the surroundings

Question 4

When dynamic equilibrium is reached the conc. of reactants and products…?

Answer 4

Remain the same +photo

Question 5

Dynamic Equilibrium

Answer 5

Substances transition between the reactants and products at equal rates, meaning there is no net change. Reactants and products are formed at such a rate that the concentration of neither changes. (Rates are the same -> and <-

Question 6

What effect does a catalyst have on the position of equilibrium?

Answer 6

No effect

Question 7

How does a catalyst affect an equil. reaction?

Answer 7

Reaction reaches equilibrium faster by providing a shorter reaction pathway leading to products being formed faster

Question 8

Equilibrium can be established from either side of the equation

Answer 8

The equilibium reached will be the same if you start with only the reactants (LHS) or only products (RHS)

Question 9

If position of equilibrium lies to the LEFT

Answer 9

Recatants predominate

Question 10

If position of equilibrium lies to the RIGHT

Answer 10

Products predominate

Question 11

Position of Equilibrium

Answer 11

+photo

Question 12

Homogeneous Equilibria

Answer 12

All of the reactants and products are in the same state at STANDARD CONDITIONS. ALL SAME STATE

Question 13

Heterogeneous Equilibria

Answer 13

Not all of the reactants and products are in the same state at STANDARD CONDITIONS. SUBSTANCES IN DIFFERENT STATES

Question 14

Le Chatelier’s Principle

Answer 14

When conditions are changed within a closed system in a dynamic equilibrium, the position of the equilibrium moves/shift to counteract/oppose this change

Question 15

How will increasing the conc of A change the Position of dynamic Equilibrium?
A + 2 B <=> C + D deltaH= -250kJmol^-1

Answer 15

More of A will cause an equilibria shift to the right to use more of A

Question 16

How will an increase in pressure affect the position of equilibia?
A (g) + B (g) <=> C (g)

Answer 16

2 mols on LHS, 1 mol of RHS. To make it more stable an increase in pressure will cause a shift to the RHS.
When the pressure increases the system will shift to oppose the change, moving to the right to form more products.

Question 17

How does an increase in temp affect the position of equilibria?
A + B <=> C + D deltaH= -ve

Answer 17

The forward reaction is exothermic as deltaH is negative, meaning that it produces heat, so this means that the backwards reaction is endothermic and so heat is taken in to oppose the change and the postiotion shifts to the left.

Question 18

The Equilibrium Law
aA + bB <=> cC + dD ( where the lower case letters represent no. moles in a homogeneous reaction )

Answer 18

Kc = [C]^c x [D]^d
——————–
[A]^a x [B]^b
Kc = equilibrium constant ( for concentration)
square brackets show conc. in mol dm^-3

Question 19

The Equilibrium Constant shows…

Answer 19

The set value, provided the temp doesn’t change, which represents what the reactants and products will settle to. ( Unaffected by pressure and catalyst)

Question 20

Values of Kc

Answer 20

If C+D are large no. moles, Kc will be large
If A+B are large no. moles, Kc will be small

Question 21

Working out Units for Kc
PCl5 <=> PCl3 + Cl2

Answer 21

Kc= [PCl3] [Cl2] = moldm^-3 x moldm^-3
—————- ——————————–
[PCl5] moldm^-3

= moldm^-3

Question 22

Working out Units for Kc
N2+3H2 ⇌ 2NH3

Answer 22

Kc= [2NH3]^2 = moldm^-3 x moldm^-3
—————- ——————————–
[N2] [H2]^3 moldm^-3 (x4)

= mol^-2 dm^6

Question 23

Calculating Kc

Question 24

If Kc’s calling

Answer 24

Think I REF
Initial moles
Reacting moles
Equilibrium moles
Final Concentration
( for table headers )

Question 25

Dalton’s Law of partial pressures

Answer 25

The sum of all the partial pressures of the gases in the mixture is equal to the total pressure

Question 26

Gas A = 10 Pa
Gas B = 5 Pa
Gas A+B= ? Pa

Answer 26

15 Pa

Question 27

How do gases exert pressure

Answer 27

By colliding with the wall of the container through random brownian motion

Question 28

What determines the partial pressure of a gas at a given temp and external pressure?

Answer 28

No. of gas molecules per unit volume

Question 29

Mole Fraction

Answer 29

Mole Fraction = Number of moles of gas A
—————————————–
Total number of moles of gas in mixture

Question 30

Partial Pressure

Answer 30

Partial Pressure = Moles fraction x total pressure

Question 31

Homogeneous Gaseous Equilibria

Answer 31

Kp = (pC)^c x (pD)^d
———————- ( you use the partial
(pA)^a x (pB)^b pressure for pC, pD…)

Question 32

If Kp’s calling

Answer 32

Think I REE
Initial Moles
Reacting Moles
Equilibrium Moles
Equilibrium partial pressure
( for table headers )