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help checking my answers to an emperical formula question

Hi, help would be appreciated ,doing my head in :smile:

Q1. An organic compound contains 52.2% Carbon, 8.6% hydrogen and 35.2% oxygen. Deduce its emperical formula

Q2. If the compound has an RMM of 88, deduce its molecular formula.

Q3. The compound can be formed from the oxidation of butan-1-ol, and reacts with sodium carbonate to produce a salt, co2 and h2o. Suggest a possible structural formula and name for the compound

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My answers

Q1. So i think I can do this part. its for example 52.2/12 , 8.6/1 and 35.2/16 , which gives a result of C2H4O when you divide by smallest.

Q2. I get confused here, I cant seem to work out a molecular formula that is different from Q1. Maybe they are the same, but if so....

Q3 .... I recognise that acid needs to react with a carbonate, and alcohols can be oxidised to carboyxlic acids, so im thinking this is butanoic acid, but then it doesnt line up with the number of carbons I have put in for the molecular formula.

Im probably just getting the molecular formula wrong, but could someone please help. Much appreicated :smile:

(edited 10 years ago)

Reply 1

AquisM

Original post by skribble

Hi, help would be appreciated ,doing my head in :smile:

Q2. If the compound has an RMM of 88, deduce its molecular formula.

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My answers

Q2. I get confused here, I cant seem to work out a molecular formula that is different from Q1. Maybe they are the same, but if so....

Remember your empirical formula is the smallest whole number ratio between the elements of the compound. The molecular formula can be whole number multiples of it.

So you've calculated the empirical formula correctly - C2H4O. Now the RMM of the empirical formula is 24 + 4 + 16 = 44, but the RMM of the molecular formula is 88, so we know that the compound's real structure has twice the number of atoms and so we multiply all of the numbers in the empirical formula by 2 to get the molecular formula - C4H8O2, or, butanoic acid. :smile:

Reply 2

skribble

Original post by AquisM

OOH its so simple, i was taking the RMM of the empirical formula to be 100g, argh! should have came on here and asked instead of spending the last hour on this, doh!

Thanks :smile:

Reply 3

AquisM

Original post by skribble

OOH its so simple, i was taking the RMM of the empirical formula to be 100g, argh! should have came on here and asked instead of spending the last hour on this, doh!

Thanks :smile:

No problem. :smile: