Question

Succinic acid is a substance produced by lichens. Chemical analysis indicates it is composed of 40.68% C, 5.08% H, and 54.24% O. Determine the empirical formula.

Answer 1

Answer:  

C₂H₃O₂

Explanation:  

Assume that you have 100 g of the compound.  

Then you have 40.68 g C, 5.08 g H, and 54.24 g O.  

1. Calculate the moles of each element.

Moles of C  = 40.68 × 1/12.01   = 3.387 mol C

Moles of H =    5.08 × 1/1.008   = 5.010 mol H

Moles of O = 54.24 × 1/16.000 = 3.390 mol O

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2. Calculate the molar ratios.  

Divide all values by the smallest number.

C:  3.387/3.387 = 1

H: 5.010/3.387 = 1.479

O: 3.390/3.387 = 1.001

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3. Multiply each ratio by 2

C:  2 × 1       = 2

H: 2 × 1.479 = 2.958

O: 2 × 1.001 = 2.002

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4. Determine the empirical formula

Round off all numbers to the closest integer.  

C: 2

H: 3

O: 2

The empirical formula is C₂H₃O₂.