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Topic: Elemental Analysis and Empirical Formula  (Read 7686 times)

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sundrops

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Elemental Analysis and Empirical Formula
« on: January 22, 2005, 06:24:14 AM »
A particular carborane has the following mass percentages:
71.94% B
12.07% H
15.99% C

What is the empirical formula of this compound?

Now what I did is the following,
71.94g B * (1mol B / 100g B) = 0.7194mol B
12.07g H * (1mol H / 100g H) = 0.1207mol H
15.99g C * (1mol C / 100g C) = 0.1599mol C

then I wdivided by the lowest denominator:

B 0.7194/0.1207 = 5.96
H 0.1207 / 0.1207 = 1
C 0.1599/0.1207 = 1.32

but I'm having trouble writing out an empirical formula because don't have whole numbers. please help.

Offline AWK

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Re:Elemental Analysis and Empirical Formula
« Reply #1 on: January 22, 2005, 08:02:43 AM »
Calculate moles of B,C and H in 100 grams of compound, ie;
moles B=71.94/10.811
and so on
Then all moles divide by a smallest number of moles, and multiply evrentually by whole nambers, 2 3 to obtain numbers of moles close to whole numbers.

What you did ?
71.94g B * (1mol B / 100g B) = 0.7194mol B
12.07g H * (1mol H / 100g H) = 0.1207mol H
15.99g C * (1mol C / 100g C) = 0.1599mol C
You calculated mass of elements (not moles of elements) in 1 gram of carborane.

The rest of calculations are useless for this problem
AWK

sundrops

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Re:Elemental Analysis and Empirical Formula
« Reply #2 on: January 22, 2005, 09:33:21 AM »
Thanks - that worked!

My answer was correct!  ;D

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