# Reacting gas volumes a level chem - help

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#1
A )What volume of oxygen reacts with 0.24cm3 of methane , CH4, at 298K and 100kPa

CH4 2O2 —-> CO2 2H2O

B) when 100cm3 of hydrogen bromide reacts with 80cm3 of ammonia , a white solid is formed and some gas is left over . What gas and how much of it is left over?

NH3 HBr —-> NH4Br

Last edited by CalypsoXenoo; 2 months ago
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2 months ago
#2
(Original post by CalypsoXenoo)
A )What volume of oxygen reacts with 0.24cm3 of methane , CH4, at 298K and 100kPa

CH4 2O2 —-> CO2 2H2O

B) when 100cm3 of hydrogen bromide reacts with 80cm3 of ammonia , a white solid is formed and some gas is left over . What gas and how much of it is left over?

NH3 HBr —-> NH4Br

For A, rearrange the ideal gas equation to get:
n=pv/RT.
Use this equation to find the moles of methane.
From the balanced equation, you can see two moles of oxygen react with 1 mole of methane, so multiply the number of moles of methane by 2 to get the moles of oxygen.
Then use the ideal gas equation again:
v=nRT/p to find the volume of Oxygen.

(Remember to convert units into Pa and m^3)

For B, Equal volumes of gases contain equal number of moles. The hydrogen bromide-ammonia reaction is 1:1, so you'll have 20cm3 of hydrogen bromide left over.
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#3
(Original post by epicnm)
For A, rearrange the ideal gas equation to get:
n=pv/RT.
Use this equation to find the moles of methane.
From the balanced equation, you can see two moles of oxygen react with 1 mole of methane, so multiply the number of moles of methane by 2 to get the moles of oxygen.
Then use the ideal gas equation again:
v=nRT/p to find the volume of Oxygen.

(Remember to convert units into Pa and m^3)

For B, Equal volumes of gases contain equal number of moles. The hydrogen bromide-ammonia reaction is 1:1, so you'll have 20cm3 of hydrogen bromide left over.
Ah this makes so much sense !! I’ve been doing pV=nRT all day and I’ve been getting most questions right but it just completely slipped out of my mind for these questions !! Thanks so much
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2 months ago
#4
(Original post by CalypsoXenoo)
Ah this makes so much sense !! I’ve been doing pV=nRT all day and I’ve been getting most questions right but it just completely slipped out of my mind for these questions !! Thanks so much
No problem!
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