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# Chemistry practice multiple choice Q edexcel watch

1. Carbon monoxide and oxygen react together as follows.
2CO(g) + O2(g) = 2CO2(g)
If all volumes of gas are measured at the same temperature and pressure, the volume
of carbon dioxide produced after 50 cm3
of carbon monoxide react with 25 cm3
of oxygen is
A 100 cm3
B 75 cm3
C 50 cm3
D 25 cm3

Not sure how the answer is 50cm3, I added them up and got 75cm3??
2. Due to the ideal gas law (pV=nRT), the same mole of any gas will take up the same volume as any other gas. This means since CO and CO2 have a 1:1 ratio they will take up the volume. This can be proven below:

These figures are for ideal conditions and assuming no mass is lost due to impurities
volume = 24dm3 x moles
for CO:
v=50cm3
v=50000dm3
n=50000dm3/24dm3
=2083.333

ratio of CO:CO2
2:2
therefore 2083.333 moles of CO: 2083.333 moles of CO2
V=24n
V=24dm3 x 2083.333V
=49999.99dm3
V=50000dm3
V=50cm3
it is understandable to add up the volume of the gases but due to the ideal gas law (pV=nRT), all gases take up the same volume under ideal conditions. The mass of the CO and the O2 are added up though to find the mass of the CO2
3. Equal amounts of all gases occupy the same volume. Or in reverse, equal volumes contain the same amount of gas particles.

2 mol (or 2 volumes) of CO reacts with 1 mol (or 1 vol) of O2 producing 2 mol (or 2 volumes) of CO2.

LET 1 volume = 25 cm3 and that becomes:

50 cm3 (2 x 25 cm3) of CO reacts with 25 cm3 of O2 producing 50 cm3 of CO2.

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