Equillibrium

Question 1

What is Dynamic Equilibrium?

Answer 1

Equilibrium means that both reactions are happening at the same rate in a closed system and the concentration of reactants and the products remains constant.

Question 2

Le Chatelier’s principal -

Answer 2

When a change is made to the reaction, that is in a dynamic equilibrium in a closed system, the reaction will oppose that change.

Question 3

Factors affecting equilibrium?

Answer 3

1. Temperature;
2. Pressure (for gaseous substances);
3. Concentration.

Question 4

How does Temperature affect the equilibrium?

Answer 4

Increasing the temperature will shift the equilibrium towards the products of an endothermic reaction.
Decreasing the temperature shifts the equilibrium towards the products of an exothermic reaction.

Question 5

How does pressure affect the equilibrium?

Answer 5

Increasing the pressure will shift the equilibrium towards the side where there are less gaseous particles.
Decreasing the pressure will shift the equilibrium towards the side where there are more gaseous particles.
If no gaseous particles are present pressure will have no effect on the equilibrium.

Question 6

How does concentration affect the equilibrium?

Answer 6

Increasing the concentration will shift the equilibrium towards the ‘other side’ of the reaction to oppose that change.
Decreasing the concentration will shift the equilibrium towards the ‘same side’ where the change occurred.

Question 7

What effect does Catalyst have on the equilibrium?

Answer 7

No effect. It just speeds up both, forward and backward reactions.

Question 8

What is Kc?

Answer 8

Kc - an equilibrium constant, it shows whether equilibrium favors the reactants or the products.
If Kc<1 - equilibrium favors the reactant side.
If Kc>1 - equilibrium favors the product side.
It is concentration of the products devided by the concentration of the reactants.
[] - concentration.

Question 9

Write and explain the Kc for 3H2 + N2 <—> 2NH3

Answer 9

Kc = [products]/[reactants] = [NH3]^2/[H2]^3[N2]

Question 10

What are the Units for the Kc? Use the previous equation (3H2 + N2 <—> 2NH3) to explain.

Answer 10

Units of the Kc depend on a ratio of the reactants and products we have.
Concentration is measured in moldm^-3 so when putting them in an equation —>

Kc = [products]/[reactants] = [NH3]^2/[H2]^3[N2] = (moldm^-3)^2/(moldm^-3)^3*moldm^-3 = mol^2dm^-6/mol^4dm^-12 = 1/mol^2dm^-6 = mol^-2dm^6

Question 11

Calculations of Kc (I mean how)

Answer 11

Since [] means concentration we’ll obviously need concentration for that.
It can be obtained from the question or using the ICE table.

Question 12

Evaluate on ICE table.
Complete a table I’ll leave you know where, might as well calculate the Kc by just putting concentration value into the brackets.(I did not, in fact, leave the table anywhere so here just look up some examples)

Answer 12

ICE table helps determine the concentration when we have moles!
I - Initial moles
C - Change in moles
E - Moles at Equilibrium which than can be used for concentration or for its calculation (if Volume is given)

Question 13

Haber process:
1. Ideal conditions.
2. Compromised conditions.
3. Reasons for why not using ideal conditions.

Answer 13

Haber process is the production of ammonia.
N2 + 3H2 <—> 2NH3 (exothermic)
1. Ideal conditions:
• Low temperature (since the reaction is exothermic, lowering temperature will shift equilibrium towards the ammonia);
• High pressure (equilibrium will shift towards the ammonia).
2. Compromised conditions:
• 450°C;
• 200 atmospheric pressure;
• Iron based catalyst.
3. Reasons for why not using ideal conditions:
• Low temperature is ideal but it significantly slows the reaction down and time is money, so compromised temperature is chosen.
• High pressure is very expensive to maintain and dangerous to work with so compromised pressure is chosen.

Question 14

Contact process:
1. Ideal conditions;
2. Compromised conditions;
3. Reasons for why not use the ideal conditions.

Answer 14

Contact process involves a stage in a manufacturing of a Sulfuric acid.
2SO2 + O2 <—> 2SO3 (exothermic)

1. Ideal conditions:
   • Low temperature (since the reaction is exothermic, lowering temperature will shift equilibrium towards the ammonia);
   • High pressure (equilibrium will shift towards the ammonia).
2. Compromised conditions:
   • 450°C;
   • 2 atmospheric pressure;
   • V2O5 as a catalyst.
3. Reasons for why not using ideal conditions:
   • Low temperature is ideal but it significantly slows the reaction down and time is money, so compromised temperature is chosen.
   • High pressure is very expensive to maintain and dangerous to work with so compromised pressure is chosen.