Ideal Gas equation question help???? Watch

Bertybassett
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Aluminium metal reacts with hydrochloric acid with the following equation:

2Al + 6HCL reacts to give 2AlCl3 +3H2

0.16 mol of aluminium reacted. Calculate the volume of H gas in dm3 that is formed at toom temp and pressure.

i first calculated that 0.24 moles of H2 are produced, then i'm stuck. the answer uses a formula which involves volume = number of moles x 24? where did this come from and how do you work out the answer. I know that 1 mole of a gas has a volume of 24 dm3 but not concentration?? could someone help??
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Winegum15
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Hello, wanted to clarify a few things, how did you go about calculating moles of H2? My answer is very different to yours
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Bertybassett
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(Original post by Winegum15)
Hello, wanted to clarify a few things, how did you go about calculating moles of H2? My answer is very different to yours
sorry i typed it up wrong. it's 0.16 mol of Al (not g) that reacted
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Winegum15
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Okay excellent, this makes sense now. Based on the fact that this is on the Ideal Gas formula we'll find the volume using pV=nRT. We already found the moles(n) of H2, which was 0.24, base on the ratio in the reaction.
Everything else is provided - Pressure(p) is normal (101000Pa), Reaction is at room temp (298K) and R represents the molar gas constant which is 8.314 -
Rearrange to find volume, V = (nRT)/p then substitute into the equation. I got an answer of 0.0057m³ which is the same as 5.7dm³
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Bertybassett
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(Original post by Winegum15)
Hello, wanted to clarify a few things, how did you go about calculating moles of H2? My answer is very different to yours
so the ratio is 2 to 5 so 0.16 divided by 2 times 3 gets you to my answer i think to work out the number of moles of h2.
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Winegum15
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Yes, we used the ratio to get the moles of H2, exactly as you described. Note that the ratio is 2:3 not 2:5 but I think that's just a typo as you got the same number as me
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Bertybassett
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(Original post by Winegum15)
Okay excellent, this makes sense now. Based on the fact that this is on the Ideal Gas formula we'll find the volume using pV=nRT. We already found the moles(n) of H2, which was 0.24, base on the ratio in the reaction.
Everything else is provided - Pressure(p) is normal (101000Pa), Reaction is at room temp (298K) and R represents the molar gas constant which is 8.314 -
Rearrange to find volume, V = (nRT)/p then substitute into the equation. I got an answer of 0.0057m³ which is the same as 5.7dm³
thanks a lot for the help that's the correct answer. however am i meant to memorise the 101000pa and 298k for the exam? furthermore, in the mark scheme they gave the equation volume of gas=number of moles x molar gas volume (which is 24) so could i have used this, and should i remember this also? my exam board is aqa btw.
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Winegum15
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(Original post by Bertybassett)
however am i meant to memorise the 101000pa and 298k for the exam?
Trust me, by the time the exam comes round you will know those numbers. Remember Celsius to Kelvin, just add 273. Remember that 25C is room temp, therefore 298K is room temp in Kelvin. 101000Pa is just something you have to remember I'm afraid!
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Bertybassett
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(Original post by Winegum15)
Trust me, by the time the exam comes round you will know those numbers. Remember Celsius to Kelvin, just add 273. Remember that 25C is room temp, therefore 298K is room temp in Kelvin. 101000Pa is just something you have to remember I'm afraid!
ah right. thank you for your help much appreciated.
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magicbeans1212
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I find chemistry quite difficult. Like I've learnt all the equations but then I still can't answer some questions and idek why
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Winegum15
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(Original post by Bertybassett)
furthermore, in the mark scheme they gave the equation volume of gas=number of moles x molar gas volume (which is 24) so could i have used this, and should i remember this also?.
Well that also works perfectly, I'm an engineer so much more used to the one I used. If you think about it though, 1 mole of any gas has 24dm³, multiply that by the moles you have and you'll get the volume of your gas. 2 mole will be 48dm³, 0.5 mole will be 12dm³, in our case, 0.24mole gives 5.7dm³
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Winegum15
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(Original post by magicbeans1212)
I find chemistry quite difficult. Like I've learnt all the equations but then I still can't answer some questions and idek why
Stick at it and it'll come to you. Chemistry requires imaginative and intuitive thinking. When I was in year 10 I got 40% in my end of year exam. I'm now embarking on a master's in Chemical Engineering with an A in Chemistry A level. The point is you're trying, asking questions, keep doing that and you will succeed!
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magicbeans1212
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(Original post by Winegum15)
Stick at it and it'll come to you. Chemistry requires imaginative and intuitive thinking. When I was in year 10 I got 40% in my end of year exam. I'm now embarking on a master's in Chemical Engineering with an A in Chemistry A level. The point is you're trying, asking questions, keep doing that and you will succeed!
Year 10 is minor tbh. Just before my GCSE exams I was a straight D in chemistry but I managed to get an A in the real thing. Yeah that's all I can do
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Bertybassett
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(Original post by Winegum15)
Trust me, by the time the exam comes round you will know those numbers. Remember Celsius to Kelvin, just add 273. Remember that 25C is room temp, therefore 298K is room temp in Kelvin. 101000Pa is just something you have to remember I'm afraid!
what exam board are do doing may i ask, i'm doing aqa and i was wondering if these figures change from exam board to exam board?
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