Gases and Reversible Reactions

Question 1

What is the volume of a gas at room temperature and pressure? What is this called?

Answer 1

One mole: 24 dm^3. Avogadro’s Law

Question 2

What is the equation for the number of moles of a gas?

Answer 2

Number of moles = Volume (dm^3) / 24

Question 3

How do you calculate the volume of a gas in a reaction from a solid?

Answer 3

1: Work out the number of moles of solid
2: Find the ratio of solid to gas
3: Use this to find the moles of gas
4: Work out the volume of gas (x24)

Question 4

How do you calculate the volume of a gas in a reaction with gases?

Answer 4

Find the ratio of balancing numbers in the equation. The ratio of numbers is the ratio of volumes.

Question 5

What are reversible reactions?

Answer 5

Reversible reactions occur when the backwards reaction (products -> reactants) takes place relatively easily under certain conditions. The products turn back into the reactants

Question 6

What is dynamic equilibrium?

Answer 6

In some reversible reactions, the forward and backwards reactions largely occur in the same conditions and at the same rate. These reactions are said to be in dynamic equilibrium - there is no overall change in the amount of products and reactants, even though the reactions are ongoing.

Question 7

Where can dynamic equilibrium take place?

Answer 7

In a closed system, otherwise products would escape

Question 8

What is Le Chatelier’s Principle?

Answer 8

If a change is imposed on an equilibrium, the position of equilibrium will shift to minimise that change

Question 9

How does changing the temperature affect the position of equilibrium?

Answer 9

If you increase the temperature, the equilibrium will move in the endothermic direction to absorb the extra heat.
If you decrease the temperature, the equilibrium will move in the exothermic direction to produce more heat.

Question 10

How does changing the pressure affect the position of equilibrium?

Answer 10

If you increase the pressure, the equilibrium will move towards the side that has fewer moles of gas to reduce pressure.
If you decrease the pressure, the equilibrium will move towards the side that has more moles of gas to increase pressure.

Question 11

How does changing the concentration affect the position of equilibrium?

Answer 11

If you increase the concentration of the reactants, the equilibrium will move to the right to use up the reactants (making more products).
If you increase the concentration of the products, the equilibrium will move to the left to use up the products (making more reactants).
Decreasing the concentration will have the opposite effect.

Question 12

How does adding a catalyst affect the position of equilibrium?

Answer 12

The position of equilibrium will stay the same, but the time taken to attain equilibrium will decrease, as the activation energy is lower.

Question 13

What are the reactants in the Haber Process? How are they made?

Answer 13

Hydrogen - made from water and methane

Nitrogen - taken from air

Question 14

What are the conditions in the Haber Process?

Answer 14

200 atmosphere pressure
400 degrees C temperature
Iron based catalyst

Question 15

What are the uses of ammonium?

Answer 15

Explosives
Dyes
Medicines
Fertilisers

Question 16

How are fertilisers useful?

Answer 16

Plants need nitrogen, phosphorus and potassium from the soil in order to grow and live. Fertilisers supply these, increasing crop yield. Artificial fertilisers can have precise compositions. Ammonia fertilisers are soluble, so chemicals can dissolve into soil to get to plants.

Question 17

How would you make ammonium sulphate in a lab and in industry?

Answer 17

In a lab - perform a titration with ammonia, sulphuric acid and methyl orange. Repeat without the indicator and do crystallisation.
In industry - make the raw materials. Fill a large reaction chamber with ammonia gas and spray sulphuric acid in. Remove ammonium sulphate powder.