Gas Stoichiometry

Question 1

Mixture of gases

Answer 1

The sum of the original pressures gives you the new pressure

Question 2

Dalton’s Law of Partial Pressures

Answer 2

• The total pressure of a mixture of non reacting gases is equal to the sum of the partial pressures of all the gases
• This works because we assume that the individual gas particles do not interact with each other
• If they interact with each other, they should have a different pressure

Question 3

Partial pressure

Answer 3

pressure of an individual gas

Question 4

Collecting gas over water

Answer 4

• If a gas is produced in a reaction, we can collect this gas by bubbling the gas through water
• Changes in water level can be used as evidence that a gas is being produced
• It allows us to measure pressure and volume changes
• Since there is pressure change there is a possibility for changed in water vapour pressure (needs to be considered in our equations)
• This means we need to include the pressure of the water vapour and gas

Question 5

Collecting gas over water: Dalton’s Law of Partial Pressures

Answer 5

• A problem that can occur is a water vapour gets mixed in with the gas product
• This problem can be solved through dalton’s law
• To find gas product, we can just do P gas product= P total- P water

Question 6

Collecting gas over water: Pressure of water and temperature

Answer 6

• The total pressure can be measured directly but not pressure of water
• P of water depends on the temperature of the water
• The Higher the temperature, the more water molecules that have evaporated in the gas state, the greater the partial pressure of water
• Scientist have already created a chart of water partial pressure at different temperatures

Question 7

Volume ratios

Answer 7

• Mol ratios can be used for volume ratios
• At a constant of T and P, the amount of gas determines the volume of the gas (avogadro’s law)
• This means 1 mol/L of O2 reacts with 2 mol/L H2 to form 2 mol/L H2O
• This doesn’t mean 1 mol= 1 L

Question 8

Law of Combining Volumes

Answer 8

The product of 2 reactants is not the sum
It is based of mol ratios
ONLY IF T AND P ARE CONSTANT