Reversible reactions

Question 1

What is the job of a catalyst?

Answer 1

To speed up the rate of reaction

Question 2

What is a reversible reaction?

Answer 2

A reaction where the products can react together to make the original reactants again.

Question 3

What indicates a reversible reaction in a chemical formula?

Answer 3

⇌

instead of →

Question 4

What is the “equilibrium” in reversible reactions?

Answer 4

When the rate of forward reaction = the rate of reverse reaction.

Question 5

What is the NAME of the process that produces Ammonia?

Answer 5

The Haber Process

Question 6

What is the main reaction for the Haber Process and what is it’s type?

Answer 6

N₂+ 3H₂ ⇌ 2NH₃

Exothermic

Question 7

What are the conditions needed for the Haber Process?

Answer 7

400-450°C
200 atm
iron catalyst

Question 8

What are the steps in the Haber process

Answer 8

1) Nitrogen gas (for the air) and hydrogen gas (obtained from methane) are pumped into the system
2) The mixture of nitrogen and hydrogen is compressed in the compressor to a pressure of 200 atmospheres and heated to a temperature of 450°C
3) The mixture passes through a reaction vessel containing an iron catalyst (beds)
4) It is then cooled so that the ammonia liquifies and is removed
5) Unreacted nitrogen and hydrogen are returned to the reaction vessel via the compressor

Question 9

What is the effect of pressure on a reversible reaction.

Answer 9

If the product has less molecules than the reactants then the forward reaction is preferred (e.g. N₂+ 3H₂ ⇌ 2NH₃)
If the products have more molecules than the reactants then the reverse reaction is preferred.

The high pressure increased the conversion rate and thus the yield

Question 10

What’s the effect of temperature on a reversible reaction that’s exothermic?

Answer 10

Warm wants to be cold
If a forward reaction is exothermic:
- An increased temperature decreases the products formed but increases the rate of reaction
- A decreased temperature increases the amount of products formed but decreases the rate of reaction

Question 11

What’s the effect of temperature on a reversible reaction that’s endothermic?

Answer 11

Cold wants to be warm
If a forward reaction is endothermic:
- An increased temperature increases the products formed and increases the rate of reaction
- A decreased temperature decreases the amount of products formed and decreases the rate of reaction

Question 12

How do we test for ammonia?

Answer 12

damp red litmus paper turns blue in its presence.

Question 13

How can ammonium (NH₄⁺) ions be identified in a compound?

Answer 13

By adding hydroxide ions and warming gently.
This produces an ammonia gas that is detected using red litmus paper- if it turns blue there is ammonium ions.
NH₄⁺(aq) + OH⁻ (aq) → NH₃(g) + H₂O(l)

Question 14

What are the factors taken into account when deciding the conditions for the Haber process of 200atm, 400°C and an iron catalyst?

Answer 14

Rate of reaction (increased by temp and catalyst)
Percentage yield (increased by pressure, decreased my temp)
Cost of equipment (greatly increased by pressure)

Question 15

What are the uses for ammonia (with formulas)?

Answer 15

The production of fertilizers (ammonium sulphate)
2NH₃ + H₂SO₄ → (NH₄)₂SO₄
This is the main use for ammonia and sulfuric acid

Question 16

What are the advantages and disadvantages of fertilisers?

Answer 16

Advantage

• Increases crop yield (profit)
• Healthier crops
• Improves soil quality

Disadvantage

• Eutrophication (Algae bloom→ No sunlight → anaerobic environment → plant eating bacteria → no life)
• Risk of stomach cancer
• Blue baby syndrome (caused by nitrates)

Question 17

What is the name of the industrial process for the production of sulfuric acid?

Answer 17

The contact process

Question 18

What is the formula of the formation sulfur trioxide and the conditions needed?

Answer 18

sulphur dioxide + oxygen ⇌ sulfur trioxide
2SO₂(g) + O₂(g) ⇌ 2SO₃

400°C, 1 atm and Vanadium(V) oxide catalyst

Question 19

What is the steps for the contact process?

Answer 19

1) Solid sulfur burns in air to form sulfur dioxide
- S + O₂→SO₂

2) Sulfur dioxide reacts with more oxygen to form sulfur trioxide
- 2SO₂ + O₂ ⇌ 2SO₃
- 400°C, 1atm and Vanadium(V) oxide catalyst

3) Sulfur trioxide is dissolved in concentrated sulfuric acid to produce oleum
- SO₃ + H₂SO₄ → H₂S₂O₇ (l)
The oleum is then diluted with water to produce sulfuric acid.
H₂S₂O₇ + H₂O → 2H₂SO₄ (l)

Question 20

Why isn’t sulfur trioxide added straight to water instead of forming oleum?

Answer 20

Adding sulfur trioxide directly to water is very violent.

Question 21

What are 4 uses for sulfuric acid?

Answer 21

• Dehydration agent (Removes water from a compound and evaporates it)
• Production of fertilizers
• Dyes (pigments)
• Explosives

Question 22

What happens to Hydrated Copper Sulfate crystals when toy add concentrated sulfuric acid?

Answer 22

They become anhydrous copper sulfate and steam in produced (due to the exothermic nature of the reaction).