Ascorbic acid (vitamin C), an essential nutrient for humans, is
an organic compound containing carbon, hydrogen & oxygen. when
1.000g of ascorbic acid was completely burnt in oxygen, 1.500g of
carbon dioxide and 0.405g of water were formed. Calculate the
empirical formula of ascorbic acid and determine its molecular
formula if its relative molecular mass is 176.
Hi UltimaOnline, how should i start the question? i tried to
form the equation of the combustion of a carboxylic acid but i
couldn't get the answer :(
Thank you so much! :)
That's because Vitamin C isn't a carboxylic acid.
From moles of CO2 generated, find moles of C in sample to be
3.4091x10-2 mol, ie. 4.0909x10-1 g.
From moles of H2O generated, find moles of H in sample to be
4.5x10-2 mol, ie. 4.5 x 10-2 g.
Hence mass of O in sample = 1.00 - (4.0909x10-1 + 4.5x10-2) =
5.4591x10-1 g, ie. 3.4119x10-2 mol.
Moles of Vitamin C = 1.00 / 176 = 5.6818x10-3 mol.
Hence mole ratio of VitaminC to C to H to O is 5.6818x10-3 :
3.4091x10-2 : 4.5x10-2 : 3.4119x10-2, which simplifies to 1 : 6 : 8
: 6.
Hence molecular formula of Vitamin C = C6 H8
O6
No prob, KeeFay! :)
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BedokFunland JC Challenge Qn
Cambridge can ask as an A grade H2 A level exam question,
"Identify the most acidic H atom, hence or otherwise, explain
why Vitamin C is acidic."
(Interested JC students go ask your school teacher or private
tutor for the answer)
