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Chemistry Question Help

Which volume of oxygen gas, at room temperature and pressure, is required for complete combustion of 1.25 × 103 mol of propan-1-ol?

A 105 cm3
B 120 cm3
C 135 cm3
D 120 cm3

Choose one
Reply 1
Avatar for ReeceM1
ReeceM1
12
1. Write out the equation for the complete combustion of propan-1-ol
2. Balance the equation
3. Determine moles of oxygen using molar ratios
4. Multiply moles of oxygen by 24000 to determine volume occupied by oxygen
Reply 2
Avatar for Kozmo
Kozmo
10
Write out the equation for the complete combustion of propan-1-ol. Work out the number of moles of O2 in this combustion using the ratios and the moles you have. Rearrange moles = mass/mr to find mass - 1g = 1cm^3 and therefore you have your answer.
Reply 3
Avatar for Kozmo
Kozmo
10
Original post by ReeceM1
1. Write out the equation for the complete combustion of propan-1-ol
2. Balance the equation
3. Determine moles of oxygen using molar ratios
4. Multiply moles of oxygen by 24000 to determine volume occupied by oxygen


Multiply by 24000? Why?
Reply 4
Avatar for ReeceM1
ReeceM1
12
Original post by Kozmo
Multiply by 24000? Why?


1 mol of gas occupies 24 dm^3 at RTP. The answers are given in cm^3, so you multiply by 24000 as there are 1000 cm^3 in a dm^3.

Original post by Kozmo
Write out the equation for the complete combustion of propan-1-ol. Work out the number of moles of O2 in this combustion using the ratios and the moles you have. Rearrange moles = mass/mr to find mass - 1g = 1cm^3 and therefore you have your answer.
1g = 1cm^3 for water
(edited 7 years ago)
Reply 5
Avatar for Kozmo
Kozmo
10
Original post by ReeceM1
1 mol of gas occupies 24 dm^3 at RTP. The answers are given in cm^3, so you multiply by 24000 as there are 1000 cm^3 in a dm^3.

1g = 1cm^3 for water


Ah yes, you're right.
And in reference to the 1g = 1cm^3, I've seen a mark scheme answer just using volume (1cm^3) in place of mass in this equation. As far as I can recall, it wasn't waster and just used as volume in cm^3 as opposed to mass in grams.
Reply 6
Avatar for F_Afzal
F_Afzal
OP
9
Thanks Guys :smile:

I was really stuck on this question (i don't know why) it sounds easy now its explained. Its from the new specification for A-level so they decide to put in multiple choice and all that
hi david
Original post by ishhhyyyy
hi david

Hey cutie
Original post by Daviddavidson22
Hey cutie

very well answered
for anyone wondering, the answer is c (135cm3) :smile:
Sorry for the late ask- but how do we know it is C? I have found the equation for combustion but I don't understand how you find the moles of oxygen by simply using a molar ratio :frown:
Original post by imscrewedlol
for anyone wondering, the answer is c (135cm3) :smile:

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