I NEED HELP ON A CHEMISTRY PROBLEM.

Omegachi

Diamond Member
Mar 27, 2001
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what is the molarity of an 85.0 ml ethanol (C2H5OH) solution containing 1.77 g of ethanol?

The molar mass of ethanol is 36.0694 (C2H5OH)

please list the steps for mee....thank you...
 

Weyoun

Senior member
Aug 7, 2000
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Ok, you should remember all of this:

[Amended Proof]
Molarity = moles / litres

moles of ethanol = 1.77/46.068

Therefore, molarity = 1.77/(46.068 * .085)
. . . . . . . . . . . . . . . .= 0.452017222
 

Aelus

Golden Member
Oct 1, 2000
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i think it's 0.577 M

1000/85=11.7647

1.77x11.7647=20.8235

20.8235/36.0694=0.5773

Aelus
 

Aelus

Golden Member
Oct 1, 2000
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I'd think either your givens are wrong, or your answer is wrong then. you'll have to consult your teacher.

Aelus
 

Weyoun

Senior member
Aug 7, 2000
700
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Ok, can you see that the moles of ethanol is 1.77/46.086?

What I was actually doing was dividing that fraction by the litres of solution, 0.085. When dividing by a fraction, you multiply by its reciprocal. In other words (1.77/46.086)/(0.085/1) = 1.77/(46.086 * 0.085) I have a tendency to work with fractions and not decimals, as I like to keep my mathematical results as accurate as possible. It's just the way I deal with things, and you'll find that if you express the moles of ethanol as a decimal and divide by the litres, you'll again achieve the same thing :)
 

Omegachi

Diamond Member
Mar 27, 2001
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yea... its the stuff in the beginning of the book. I am kinda new to this, so i need to get adjusted.
 

Weyoun

Senior member
Aug 7, 2000
700
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The whole concept of moles etc. can be fairly confusing to start with. However, I'm sure you'll be fine with it one you get used to it :)