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Question from Acidic Environment

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steph_batten:
So stuck with this question. Please help!!  :)

The following data was collected for an organic compound
M (g/mol) : 88.1
Composition (by weight):
54.5% C
36.4% O
9.1% H
m.p.(degreeC) : -5.4
b.p.(degreeC) : 163.3
Universal Indicator: turns red

(b) Calculate the empirical formula of the compound
(c) Calculate the molecular formula of the compound
(d) Draw five possible isomers of this compound

RuiAce:

--- Quote from: steph_batten on February 27, 2017, 06:27:33 pm ---So stuck with this question. Please help!!  :)

The following data was collected for an organic compound
M (g/mol) : 88.1
Composition (by weight):
54.5% C
36.4% O
9.1% H
m.p.(degreeC) : -5.4
b.p.(degreeC) : 163.3
Universal Indicator: turns red

(b) Calculate the empirical formula of the compound
(c) Calculate the molecular formula of the compound
(d) Draw five possible isomers of this compound

--- End quote ---
Compare the molar mass to the percentage composition to determine the molar mass of each atom that builds the compound

C: 88.1 * 54.5% = 48.0145
O: 88.1 * 36.4% = 32.0684
H: 88.1 * 9.1% = 8.0171

These molar masses reveal the total molar mass of carbon/oxygen/hydrogen atoms are present. Divide by the molar mass of the atoms themselves to therefore determine how many atoms are present. (All answers here will be approximates)

48.0145/12.01 = 4
32.0684/16.00 = 2
8.0171/1.008 = 8

Hence we anticipate that the atom ratio of C:O:H is 4:2:8, which simplifies to 2:1:4

So the empirical formula is given C2H4O

Now, the organic compound turns universal indicator red. Hence we should expect some kind of an acid.
The 4 carbons is self-explanatory.

What could possibly have 4 atoms, be an organic compound, an acid, and also coincidentally 2 oxygens?
The answer is a carboxylic acid (like acetic acid).
Here, I propose that the answer is butanoic acid.

Check: Butanoic acid has formula C4H7COOH.
12.01*4 + 1.008*8 + 16.00*2 = 88.104
Liquid at room temperature, which is between the m.p. and b.p.
Perfect

Scroll a bit down to find some isomers of butanoic acid.

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