Moles 2

Question 1

what do we usually measure volumes of gas in?

Answer 1

• cubic centimetres (cm^3)

Question 2

what unit is commonly used in mole calculations?

Answer 2

• cubic decimetres (dm^3)

Question 3

how do you convert between centimetres and decimetres?

Answer 3

• cm^3 -> dm^3 = /1000
• dm^3 -> cm^3 = x1000

Question 4

how can the moles of a gas be calculated?

Answer 4

• from its volume alone
• moles = volume(dm^3) / 24dm^3
• the denominator is 24dm^3 for EVERY gas
  OR
• moles = volume(cm^3) / 24000(cm^3)
• the denominator is 24000cm^3 for EVERY gas

Question 5

calculate the amount in moles in 1500cm^3 of H2.

Answer 5

• moles = volume(cm^3) / 24000(cm^3)
• 1500/24000
• 0.0625 mol

Question 6

calculate the amount in moles in 6dm^3 of CO2.

Answer 6

• moles = volume(dm^3) / 24dm^3
• 6/24
• 0.25mol

Question 7

calculate the volume of 0.8 moles of CH4.

Answer 7

• volume (dm^3) = moles x 24dm^3
• 0.8 x 24
• 19.2 dm^3

Question 8

what steps do you need to do in order to calculate the volume of O2 needed to react with 10g of N2?

Answer 8

• N2 + 2O2 -> 2NO2
  1. convert the mass of N2 into moles of N2
  2. use the mole ratio from the balancing numbers in the equation.
  3. convert moles of O2 into the volume of O2

Question 9

what steps do you need to do in order to calculate the volume of NO2 produced from 5dm^3 of N2?

Answer 9

• N2 + 2O2 -> 2NO2
  1. use the mole ratio from the balancing numbers in the equation

Question 10

what are the 3 different formulae for moles and in which circumstances do you use each one?

Answer 10

• mass(g) / RFM - USE THIS FOR ANYTHING
• volume (dm^3) / 24dm^3 - FOR GAS VOLUMES