Equilibrium (19)

Question 1

Calculating units of equilibrium

Answer 1

Always write the positive indices first

Question 2

Homogenous Equilibrium

Answer 2

This is where all species in the equilibrium have the same state.

Question 3

Heterogenous Equilibrium

Answer 3

This is where species in the equilibrium can be different states. This means that any of the species that are different like solids or liquids will be left out of the Kc equation unless there is no aqueous solution

Question 4

Kp

Answer 4

This is the equilibrium constant of gases in terms of partial pressure. You use this for gases because it’s easier to work with pressure than concentration

Question 5

Mole Fraction

Answer 5

If you have the same volume of different gases that are in the same conditions, they will have the same number of moles.

Mole Fraction= Moles in A / Moles In Gas Mixture

Question 6

What is the sum of mole fractions

Answer 6

1

Question 7

Partial Pressure

Answer 7

The contribution that each gas makes to the total pressure.

Partial pressure = mole fraction A x total pressure

Question 8

How much do all the partial pressures add up to?

Answer 8

The total pressure

Question 9

Kp equation

Answer 9

This is written in the same way as Kc only you use partial pressure instead of concentration.

Question 10

The equilibrium constant

Answer 10

The constant is the value K and when:
K=1 the equilibrium is in the middle
K=100 the equilibrium is to the right and in favour of products
K= 1x10-2 the equilibrium is to the left and in favour of the reactants
It gives you the exact position of equilibrium

Question 11

What can change the K constant?

Answer 11

Only if a temperature is changed, that will change the K constant. Pressure and concentration wont. K will get larger or smaller depending on if it’s exo or endothermic.

Question 12

Exothermic effect on K

Answer 12

If the forward reaction is exothermic and you are raising the temperature, K will decrease as the equilibrium is moving to the left so the yield will also decrease.

Question 13

Explaining the shift in equilibrium on exothermic

Answer 13

When the temperature is increased from 500k to 700k, the K value will decrease and the system will no longer be in equilibrium, the ratio will also increase and be greater than the Kp value. This shows that the partial pressure of the reactants will increase and the partial pressure of the products will decrease. A new equilibrium will be reached where the Kp value is equal to the partial pressure equation. This is also the case for Kc.

Question 14

Endothermic Effect on K

Answer 14

If the forward reaction is endothermic and the temperature is being raised, the K value will increase and the equilibrium will shift to the right which means there will be a higher yield of products

Question 15

Explain the shift in equilibrium on endothermic

Answer 15

If the temperature is increased from 700K to 1000K, the Kp value will increase which means the system is no longer in equilibrium. There will be a greater partial pressure for the products and a smaller partial pressure for the reactants until they reach the same value as the new Kp. This is also the case for Kc

Question 16

Pressure and Concentration Effect on K

Answer 16

There will be no affect on K from either of these factors, but it is this very reason that a shift happens as we know from le Chatelier.

Question 17

Explain the shift in equilibrium from concentration

Answer 17

If you have a system in equilibrium and a certain Kc value, and you increase the amount of reactants you have, the ratio is now less than Kc which means the system is no longer in equilibrium. It must return back to it’s original Kc value which means the product concentration must increase and the reactants must decrease. The equilibrium will shift to the right to combat this until you reach your original Kc value. You have to remember the K value doesn’t change, it’s only the ratio that changes and causes the shift.

Question 18

Explain the shift in equilibrium from pressure

Answer 18

If you have a system in equilibrium and you double the pressure, the total pressure will double and so will the reactants and products. This means the ratio will increase and be bigger than the Kp value and it’s no longer in equilibrium. The Kp value must be returned to normal so the partial pressure of the product must decrease and the partial pressure of the reactant must increase. the Kp value will return back to its value and the equilibrium will have shifted to the left.