# AQA A Level chemistry help

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#1
Hi can someone help me with this question please

The equation below represents the complete combustion of butane. C4H10(g) + 6.5 O2(g) ---------> 4 CO2(g) + 5 H2O(g)
20 cm3 of butane are completely burned in 0.20 dm3 of oxygen. Which statement is correct?
All volumes are measured at the same temperature and pressure.
A 40 cm3 of carbon dioxide are formed
B 0.065 dm3 of oxygen react
C 70 cm3 of oxygen remain
D 0.50 dm3 of steam are formed
Last edited by 123abc123!; 1 month ago
0
1 month ago
#2
(Original post by 123abc123!)
Hi can someone help me with this question please

The equation below represents the complete combustion of butane. C4H10(g) + 6.5 O2(g) ---------> 4 CO2(g) + 5 H2O(g)
20 cm3 of butane are completely burned in 0.20 dm3 of oxygen. Which statement is correct?
All volumes are measured at the same temperature and pressure.
A 40 cm3 of carbon dioxide are formed
B 0.065 dm3 of oxygen react
C 70 cm3 of oxygen remain
D 0.50 dm3 of steam are formed
Well what are your thoughts on this question?

Remember that if they are all at the same conditions of pressure and temperature, then the ratio of moles is proportionate to ratio of volumes of gases.
0
1 month ago
#3
The answer is C because you know the ratio to burn 1 mole of C4H10 is 1:6.5 so to burn 20cm3 of it you need 130cm3 of oxygen. 0.2 dm3 is 200cm3 so 200-130=70cm3 of oxygen left over
1
#4
(Original post by Wannabevet133)
The answer is C because you know the ratio to burn 1 mole of C4H10 is 1:6.5 so to burn 20cm3 of it you need 130cm3 of oxygen. 0.2 dm3 is 200cm3 so 200-130=70cm3 of oxygen left over
Thank you!
0
1 month ago
#5
(Original post by 123abc123!)
Hi can someone help me with this question please

The equation below represents the complete combustion of butane. C4H10(g) + 6.5 O2(g) ---------> 4 CO2(g) + 5 H2O(g)
20 cm3 of butane are completely burned in 0.20 dm3 of oxygen. Which statement is correct?
All volumes are measured at the same temperature and pressure.
A 40 cm3 of carbon dioxide are formed
B 0.065 dm3 of oxygen react
C 70 cm3 of oxygen remain
D 0.50 dm3 of steam are formed
1
#6
(Original post by Davies Chemistry)
Thank you so much!!
0
1 month ago
#7
(Original post by Davies Chemistry)
I get what you’ve done here but just to add, the question doesn’t tell you that it’s at standard room temperature and pressure, hence we can’t assume that 1 mole is = 24dm3 of gas. The question just says they are at the same conditions, which might not necessarily be rtp

Obviously it doesn’t do any danger here because it cancels out in the end and so you still get the right answer.
Last edited by qwert7890; 1 month ago
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