Equilibrium

Question 1

All combustion reactions are

Answer 1

irreversible

Question 2

Ammonium chloride reversible

Answer 2

Ammonia + HCl

Question 3

Le Chatelier’s Principle

Answer 3

when a system in dynamic equilibrium is subjected to a change in conditions that disturb the equilibrium, the system will respond in such a way so as to reduce that change

Question 4

Concentration change

Answer 4

Reduce (move towards that side to produce more)
Add (move away from that side to remove)

Question 5

Concentration only for what substances

Answer 5

Aqueous and gaseous

Question 6

Pressure/vol change only for what substances

Answer 6

Gaseous

Question 7

Pressure change

Answer 7

Increase in pressure (decrease moles of gas molecules)
Decrease in pressure (increase moles of gas molecules)

Question 8

What happens if both side of equation has same number of moles of gas particles (pressure change)

Answer 8

Nothing
BUT
Rate of achieving dynamic equilbrium is faster

Question 9

Temperature change

Answer 9

Only for endo/exo reactions

Increase in temp (move towards endo side to remove added heat)
Decrease in temp (move towards exo side to release more heat)

Question 10

Catalyst

Answer 10

Provides an alternative pathway with lower activation energy
Increases rate of forward and backward reaction to the same extent

Helps system reach dynamic equilibrium at a faster rate

Question 11

Where to get hydrogen and nitrogen for Haber process

Answer 11

Hydrogen: Cracking of crude oil
Nitrogen: Fractional distillation of liquid air

Question 12

Equation for Haber process

Answer 12

3H2 + N2 –> 2NH3

enthalpy change = -92kj/mol

Question 13

Temperature for Haber process

Answer 13

Optimum is 450˚C

The lower the better (cos exo) but going too low will lead to a very slow rate of reaction

Too high is too expensive to maintain

Hence 450˚C is a compromise temperature to result in high yield of ammonia in a short period of time

Question 14

Pressure for Haber process

Answer 14

Optimum is 250 atm

High pressure favours forward reaction 👍 and leads to high rate of reaction 👍
But very expensive to maintain (pipes etc.)

Hence 250 atm is a compromise pressure

Question 15

Catalyst for Haber process

Answer 15

Iron to speed up rate of reaction

Question 16

Concentration for Haber process

Answer 16

Continual removal of ammonia (decrease in conc) to favour forward reaction

Question 17

Steps in Haber process

Answer 17

1. Hydrogen (cracking of crude oil) and Nitrogen (fractional distillation of liquid air) is mixed in the ratio 1:3
2. Gases compressed to 250 atm in the compression chamber
3. Heated to 450˚C and passed over finely divided iron in the catalyst chamber (10-15% become ammonia)
4. Nitrogen, Hydrogen and Ammonia (gas) are cooled in the cooling chamber
5. Ammonia condenses and is removed as liquid ammonia
6. Hydrogen and Nitrogen are pumped back into the converter for further reaction