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Another Moles Question
Hey,
I'm having trouble with the following question:
10.4g of a gas occupies a volume of 3.72dm³ at standard temp and pressure. What is the molar mass of the gas?
Ok, so I know you're meant to use the equation:
Number of moles of gas = Volume of gas/Molar volume at same T&P
and then use the standard moles = mass/molar mass to find the final answer.
But, for the bit "Molar volume at same T&P" I don't know how to get that value. What do I do? Because I thought it was always 24, but my answers say 22.4 for this question.
Thankyou very much x
I'm having trouble with the following question:
10.4g of a gas occupies a volume of 3.72dm³ at standard temp and pressure. What is the molar mass of the gas?
Ok, so I know you're meant to use the equation:
Number of moles of gas = Volume of gas/Molar volume at same T&P
and then use the standard moles = mass/molar mass to find the final answer.
But, for the bit "Molar volume at same T&P" I don't know how to get that value. What do I do? Because I thought it was always 24, but my answers say 22.4 for this question.
Thankyou very much x
Find the number of moles of substance. Since you don't know what the gas is, use 'X' for the Molar mass.
moles = mass/RMM or RAM
moles = 10.4/ X
1 mole of gas occupies 24 (or 22.4) dm^3 of volume at standard T & P.
X moles of gas will occupy 3.24 dm^3 of volume at standard T & P.
I think you can solve it from here.
HINT: Equate the two!
I didn't give the answer out on purpose. If you CAN'T do this, go thru your mole chapter AGAIN! Don't ask for any answers. You'll get confused FURTHER.
Cheers!
moles = mass/RMM or RAM
moles = 10.4/ X
1 mole of gas occupies 24 (or 22.4) dm^3 of volume at standard T & P.
X moles of gas will occupy 3.24 dm^3 of volume at standard T & P.
I think you can solve it from here.
HINT: Equate the two!
I didn't give the answer out on purpose. If you CAN'T do this, go thru your mole chapter AGAIN! Don't ask for any answers. You'll get confused FURTHER.
Cheers!
lil one
Hey,
I'm having trouble with the following question:
10.4g of a gas occupies a volume of 3.72dm³ at standard temp and pressure. What is the molar mass of the gas?
Ok, so I know you're meant to use the equation:
Number of moles of gas = Volume of gas/Molar volume at same T&P
and then use the standard moles = mass/molar mass to find the final answer.
But, for the bit "Molar volume at same T&P" I don't know how to get that value. What do I do? Because I thought it was always 24, but my answers say 22.4 for this question.
Thankyou very much x
I'm having trouble with the following question:
10.4g of a gas occupies a volume of 3.72dm³ at standard temp and pressure. What is the molar mass of the gas?
Ok, so I know you're meant to use the equation:
Number of moles of gas = Volume of gas/Molar volume at same T&P
and then use the standard moles = mass/molar mass to find the final answer.
But, for the bit "Molar volume at same T&P" I don't know how to get that value. What do I do? Because I thought it was always 24, but my answers say 22.4 for this question.
Thankyou very much x
when they say standard temp & pressure(STP)..its 22.4dm3, while if its room temp & pressure,(RTP) then its 24dm3...
if we say 1 mole has a volume of 22.4...
and x moles have a volume of 3.72..
x=3.72/22.4=0.16607 moles.
m= 10.4
n=m/M so M= 10.4/0.16607=62.6g/mol... weird its usually a whole number.. nevermind! prob did a calculation mistake somewhere.. or its prob right!
oops! i gave her da answer! sorry ayaz!
xxx24 is considered as the STANDARD.
You see, the average room temp and pressure isn't the same all around the world. You'd have to go deep into details about physics if you want to find out why. The pressure varies from place to place due to the temperature.
Its damn hot in the Middle East, so you won't expect the gas to be at the same temperature and pressure as some gas, say, in the Arctic, would you?
24 is the STANDARD for a LABORATORY.
22.4 is the AVERAGE.
You see, the average room temp and pressure isn't the same all around the world. You'd have to go deep into details about physics if you want to find out why. The pressure varies from place to place due to the temperature.
Its damn hot in the Middle East, so you won't expect the gas to be at the same temperature and pressure as some gas, say, in the Arctic, would you?
24 is the STANDARD for a LABORATORY.
22.4 is the AVERAGE.
Thats wrong Rana 
Your working is correct though. If you follow this lil_one, you should get the answer. But don't ask! We can solve this question for you, but what about those in the exams?
And don't worry.. you wouldn't get confused between using 24 and 22.4. Its given in the question SPECIFICALLY what they WANT you to use. Or the mention it in front of the papers.
Rana try it with 24 dm^3 and you'll get the correct answer.
Your working is correct though. If you follow this lil_one, you should get the answer. But don't ask! We can solve this question for you, but what about those in the exams?
And don't worry.. you wouldn't get confused between using 24 and 22.4. Its given in the question SPECIFICALLY what they WANT you to use. Or the mention it in front of the papers.
Rana try it with 24 dm^3 and you'll get the correct answer.
umm in the question they said "standard temp & pressure" (STP)which is 0 degrees and 1 atm..so its 22.4
when its standard for a lab (room temprature and pressure, RTP) the temp id 24 degrees and pressure 1 atm... its 24..
u can learn it easilly as at higher temparatures volumes take up more space
when its standard for a lab (room temprature and pressure, RTP) the temp id 24 degrees and pressure 1 atm... its 24..
u can learn it easilly as at higher temparatures volumes take up more space
wait wait.. so u use 24? how come?
A Y Z
24 is considered as the STANDARD.
You see, the average room temp and pressure isn't the same all around the world. You'd have to go deep into details about physics if you want to find out why. The pressure varies from place to place due to the temperature.
Its damn hot in the Middle East, so you won't expect the gas to be at the same temperature and pressure as some gas, say, in the Arctic, would you?
24 is the STANDARD for a LABORATORY.
22.4 is the AVERAGE.
You see, the average room temp and pressure isn't the same all around the world. You'd have to go deep into details about physics if you want to find out why. The pressure varies from place to place due to the temperature.
Its damn hot in the Middle East, so you won't expect the gas to be at the same temperature and pressure as some gas, say, in the Arctic, would you?
24 is the STANDARD for a LABORATORY.
22.4 is the AVERAGE.
no its not!
22.4 is the volume at 0 degrees & 1 atm which is internationally known as STP
yeah in labs its 24.. known as RTP.. but they said at STP..
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