Empirical formula

  • #1
rachelmaddiee
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Homework Statement:
I need help with a question
Relevant Equations:
N/A
Is everything correct?
Percent by mass C = 40.60%
Percent by mass H = 5.18%
Percent by mass O = 54.22%
Empirical formula = ? (unknown)

Inverse molar mass C = 1 mol/12.01 g
Inverse molar mass H = 1 mol/1.008 g
Inverse molar mass O = 1 mol/16.00 g

Convert the masses to moles.
C = 40.60 g/12.01 g/mol = 3.380 mol
H = 5.18 g/1.008 g/mol = 5.138 mol
O = 54.22 g/16.00 g/mol = 3.388 mol

Divide by the lowest, seeking the smallest whole-number ratio
C = 3.380/3.380 = 1 = 1 mol C
H = 5.138/3.380 = 1.52 = 1.5 mol H
O = 3.388/3.380 = 1.00 = 1 mol O
The simplest mole ratio is (1 mol C):(1.5 mol H):(1 mol O).

2 x 1 mol C = 2 mol C
2 x 1.5 mol H = 3 mol H
2 x 1 mol O = 2 mol O
The simplest whole-number ratio of atoms is (2 atoms C):(3 atoms H):(2 atoms O). The empirical formula of succinic acid is C2H3O2.
84F408B9-8124-49F8-B2C9-B3F0D490F513.png
 

Answers and Replies

  • #2
chemisttree
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That is a textbook answer to that problem!
 
  • #3
rachelmaddiee
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That is a textbook answer to that problem!
A textbook answer??
 
  • #4
chemisttree
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Like you authored the answer in the textbook’s solution manual!
👍🏻
 
  • #5
rachelmaddiee
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Like you authored the answer in the textbook’s solution manual!
👍🏻
I followed an example in my book but I’m not sure if it’s correct..
 
  • #6
chemisttree
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good job. Correct!
Also note that the correct molecular formula is C4H6O4

So, empirical formula is not always the same as molecular formula.
 
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