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Topic: Simple Gas Stoich problem  (Read 5164 times)

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Offline al526

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Simple Gas Stoich problem
« on: March 01, 2011, 07:58:56 PM »
How many liters of carbon dioxide gas are produced from the complete combustion of 24.0 liters of C2H2 if all gases are measured at 50°C and 101.3 kPa?

I got the answer as 56.8 L, but apparently it's wrong. I don't know if there's been a mistake on the answer key, or if I did something wrong.

What I did:
2C2H2+ 5O2 = 4CO2+ 2H2O
24.0 L C2H2= 1.07 M
1.07M * 2= 2.14 M CO2

V=nRT/P=2.14M(0.0821)(323.15K)/1atm= 56.8 L CO2


thanks!

Offline opti384

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Re: Simple Gas Stoich problem
« Reply #1 on: March 01, 2011, 08:48:10 PM »
Quote
V=nRT/P=2.14M(0.0821)(323.15K)/1atm= 56.8 L CO2

Is the pressure really 1atm?

Offline DrCMS

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Re: Simple Gas Stoich problem
« Reply #2 on: March 01, 2011, 08:58:00 PM »
How many liters of carbon dioxide gas are produced from the complete combustion of 24.0 liters of C2H2 if all gases are measured at 50°C and 101.3 kPa?

I got the answer as 56.8 L, but apparently it's wrong. I don't know if there's been a mistake on the answer key, or if I did something wrong.

I do not know what the answer key says but i do know your answer is wrong.  If you read the question again properly you might get the right answer which does not require much maths at all.

Offline rabolisk

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Re: Simple Gas Stoich problem
« Reply #3 on: March 01, 2011, 09:19:01 PM »
I got the answer as 56.8 L, but apparently it's wrong. I don't know if there's been a mistake on the answer key, or if I did something wrong.

24.0 L C2H2= 1.07 M
1.07M * 2= 2.14 M CO2

V=nRT/P=2.14M(0.0821)(323.15K)/1atm= 56.8 L CO2


You did something wrong, namely the bolded parts.

Offline al526

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Re: Simple Gas Stoich problem
« Reply #4 on: March 01, 2011, 09:44:20 PM »
I got the answer as 56.8 L, but apparently it's wrong. I don't know if there's been a mistake on the answer key, or if I did something wrong.

24.0 L C2H2= 1.07 M
1.07M * 2= 2.14 M CO2

V=nRT/P=2.14M(0.0821)(323.15K)/1atm= 56.8 L CO2


You did something wrong, namely the bolded parts.

okay thanks~
so the conversion between kPa and atm is correct.
is the liter to mole conversion incorrect? (24 L / 22.414)? which would affect the number of moles of CO2...

Offline opti384

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Re: Simple Gas Stoich problem
« Reply #5 on: March 01, 2011, 10:03:50 PM »
The volume of 1 mol of gas will be 22.4L only at 1atm, 0°C.

Offline rabolisk

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Re: Simple Gas Stoich problem
« Reply #6 on: March 01, 2011, 10:06:17 PM »
I got the answer as 56.8 L, but apparently it's wrong. I don't know if there's been a mistake on the answer key, or if I did something wrong.

24.0 L C2H2= 1.07 M
1.07M * 2= 2.14 M CO2

V=nRT/P=2.14M(0.0821)(323.15K)/1atm= 56.8 L CO2


You did something wrong, namely the bolded parts.

okay thanks~
so the conversion between kPa and atm is correct.
is the liter to mole conversion incorrect? (24 L / 22.414)? which would affect the number of moles of CO2...

That is both incorrect and unnecessary.

Quote
V=nRT/P=2.14M(0.0821)(323.15K)/1atm= 56.8 L CO2

Is the pressure really 1atm?

The pressure is indeed 1 atm, and not the reason why he got the answer wrong..

Offline opti384

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Re: Simple Gas Stoich problem
« Reply #7 on: March 01, 2011, 10:22:27 PM »
Quote
The pressure is indeed 1 atm, and not the reason why he got the answer wrong..

Did you keep this "if all gases are measured at 50°C and 101.3 kPa" in mind?


Offline rabolisk

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Re: Simple Gas Stoich problem
« Reply #8 on: March 01, 2011, 10:52:18 PM »
Quote
The pressure is indeed 1 atm, and not the reason why he got the answer wrong..

Did you keep this "if all gases are measured at 50°C and 101.3 kPa" in mind?



I'm not sure exactly what you mean. I was just saying that 101.3 kPa = 1 atm, but that is irrelevant in solving this problem, because "all gases are measured at 50°C and 101.3 kPa".

Offline al526

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Re: Simple Gas Stoich problem
« Reply #9 on: March 01, 2011, 10:55:22 PM »
Wow, I see what I did wrong...such an obvious mistake.

I got the right answer.
Thanks so much for everyone's *delete me*! :)

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