O Level Chemistry: Mole Concepts / Chemical Calculations
05 Mar
Posted by: sean in: Chemistry Notes & Tips
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Below is a common Mole Calculation question on finding the Empirical and then Molecular Formulae of a compound. Do make sure you can amswer this one as it is a very common examination question that warrant a couple of important marks. I said Important because this is not a really tough question and we should score full marks for it.
Example:
Compound Y contains 40.0% carbon, 6.6% hydrogen and 53.3% oxygen. It has a relative molecular mass of 180. What is the molecular formula of Y?Tips:
1st Step – Find the mass of each component by taking a basis of 100g
2nd Step – Find the empirical formula
3rd Step – Find the molecular formula
Please leave your working and answers in the “Comment” section directly below this post.
PS: “Either You Practice & Utilize It, or You Loose It!”
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2 Responses
Jennifer
08|Mar|2008 1Element C H O
Mass of Element 40 6.6 53.3
Ar 12 1 16
no. of mol 3.33 6.6 3.33
molar ratio 1 2 1
hence empirical formula: CH2O
n
= 180/(12+2+16=30)
=6
therefore molecular formula of Y: C6H12O6
Reply
sean
09|Mar|2008 2You are spot on. The molecular formulae is indeed C6H12O6.
This is actually a Sugar compound.
Reply
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