Unit 3 calculation questions
What volume of oxygen (in litres) would be required for the complete combustion of a gaseous mixture containing 1 litre of carbon monoxide and 3 litres of hydrogen? (All volumes are measured at the same temperature and pressure.)
What is the balanced equation for this reaction?
What is the balanced equation for this reaction?
Standard equation for enthalpy of combustion:
1 mole of substance plus O2 ---> CO2 plus H2O
Balanced equation for this question:
CO plus H2 plus 1.5O2 ---> CO2 plus H2O
Convert litres to dm3. You don't have to do this as litres and dm3 are equal to each other but I'm used to working in dm3.
CO2 = 1 litre = 1 dm3
H2 = 3 litres = 3 dm3
Work out moles of CO2 and H2 using the equation "n = V / molar gas volume":
n (CO2) = 1 / 24 = 0.0417 mol
n (H2) = 3 / 24 = 0.125 mol
Work out moles of oxygen needed to combust moles of CO2 and O2 using stoichiometry (1 : 1.5):
n (O2) for CO2 = 0.0417 x 1.5 = 0.0626 mol
n (O2) for H2 = 0.125 x 1.5 = 0.188 mol
Work out volume of oxygen needed to combust moles of CO2 and H2 using the equation "V = n x molar gas volume":
V (O2) for CO2 = 0.0626 x 24 = 1.50 dm3
V (O2) for H2 = 0.188 x 24= 4.51 dm3
Work out total volume of O2 and convert dm3 into litres:
Total V (O2) = 1.50 plus 4.51 = 6.01 dm3
6.01 dm3 = 6.01 litres
PS. For some reason it doesn't show the plus symbol so I just used plus the word instead
1 mole of substance plus O2 ---> CO2 plus H2O
Balanced equation for this question:
CO plus H2 plus 1.5O2 ---> CO2 plus H2O
Convert litres to dm3. You don't have to do this as litres and dm3 are equal to each other but I'm used to working in dm3.
CO2 = 1 litre = 1 dm3
H2 = 3 litres = 3 dm3
Work out moles of CO2 and H2 using the equation "n = V / molar gas volume":
n (CO2) = 1 / 24 = 0.0417 mol
n (H2) = 3 / 24 = 0.125 mol
Work out moles of oxygen needed to combust moles of CO2 and O2 using stoichiometry (1 : 1.5):
n (O2) for CO2 = 0.0417 x 1.5 = 0.0626 mol
n (O2) for H2 = 0.125 x 1.5 = 0.188 mol
Work out volume of oxygen needed to combust moles of CO2 and H2 using the equation "V = n x molar gas volume":
V (O2) for CO2 = 0.0626 x 24 = 1.50 dm3
V (O2) for H2 = 0.188 x 24= 4.51 dm3
Work out total volume of O2 and convert dm3 into litres:
Total V (O2) = 1.50 plus 4.51 = 6.01 dm3
6.01 dm3 = 6.01 litres
PS. For some reason it doesn't show the plus symbol so I just used plus the word instead
(edited 6 years ago)
Original post by A_Ch
Thanks for the help, but I'm doing Higher Chemistry so don't know what stoichiometry is. Thanks for the balanced equation, that was the bit I was confused on.
Stoichiometry is basically the amount of products and reactants you have.
For example, in this question we have one mole of carbon monoxide and hydrogen but 1.5 moles of oxygen. If you want to find the moles of oxygen you need to find the moles of carbon monoxide and hydrogen needed to combust oxygen.
Are you doing GCSE or A-level?
(edited 6 years ago)
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