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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: iNerd on October 30, 2010, 01:32:39 pm

Title: Correct this Mol Question?
Post by: iNerd on October 30, 2010, 01:32:39 pm
Hey; we weren't given the sols and I'm just wondering if I've done all of this correct [ mainly worried about part (f) ]
Appreciate it if you could correct it.
Thanks

Ethanol undergoes combustion with oxygen.
a) Show the balanced eq.
b) What is the mass of one mol of ethanol
c) Determine the amount [ no. of mol ] in 10g of ethanol
d) How many mole of carbon atoms in 10g of ethanol?
e) Determine the % composition of carbon in ethanol
f) What mass of carbon dioxide is produced if 10g of ethanol is burnt.

MY ANSWERS
a) C2H5OH + 3O2 >>>> 2CO2 + 3H2O
b) (12x2) + (1x5) + 16 + 1 = 46gmol ^ -1
c) n = m/M ....n = 10/46......n = 5/23 mol so approximately 0.217mol.
d) 2mol of carbon atoms so 0.217 times 2 = 0.434 mol.
e) 24g of carbon in ethanol so 24/46 times 100 = 52.17%
f) Ratio: what we want/what we know
          : 2:1
Mol of ethanol reacting as found above is 5/23mol therefore mole of Carbon dioxide produced is 5/23 times 2 = 10/23mol
n = m/M therefore m = nM
m = 10/23mol times molar mass of carbon dioxide
M(carbon dioxide) = 12 + (16x2) = 44gmol ^ -1
therefore m = 10/23 times 44
therefore 19.13grams of carbon dioxide is produced
Title: Re: Correct this Mol Question?
Post by: iNerd on October 30, 2010, 02:15:41 pm
Anyone?
Title: Re: Correct this Mol Question?
Post by: 2317 on October 30, 2010, 02:25:41 pm
b) Answer is 46 grams. not grams/mol (Theyre asking for mass not molar mass.)

rest seems ok.
Title: Re: Correct this Mol Question?
Post by: iNerd on October 30, 2010, 02:26:35 pm
Quote from: 2317 on October 30, 2010, 02:25:41 pm
b) Answer is 46 grams. not grams/mol (Theyre asking for mass not molar mass.)

rest seems ok.
FOR SURE? really? I got part (f) right? :coolsmiley:
Title: Re: Correct this Mol Question?
Post by: m@tty on October 30, 2010, 02:29:00 pm
Quote from: iNerd on October 30, 2010, 02:26:35 pm
Quote from: 2317 on October 30, 2010, 02:25:41 pm
b) Answer is 46 grams. not grams/mol (Theyre asking for mass not molar mass.)

rest seems ok.
FOR SURE? really? I got part (f) right? :coolsmiley:

Yep. All correct.
Title: Re: Correct this Mol Question?
Post by: 2317 on October 30, 2010, 02:31:50 pm
yeah its correct :)
Title: Re: Correct this Mol Question?
Post by: iNerd on October 30, 2010, 02:37:27 pm
Hahahahaha im ecstatic! finally get this shit :P ...thanks guys; karma will be dished out appropiately ;)