• Support PF! Buy your school textbooks, materials and every day products Here!

What are the empirical and molecular formulas of the compound

  • Chemistry
  • Thread starter Kingthi
  • Start date
  • #1
1
0
"A compound contains only carbon, hydrogen, and oxygen. Combustion of 10.68 mg of the compound yields 16.01 mg CO2 and 4.37 mg H2O. The molar mass of the compound is 176.1 g/mol. What are the empirical and molecular formulas of the compound."

I saw an earlier post but it wasn't solved yet. There were some good explanations but can I get a step by step guide to solving this, i just cant seem to get it

I have started off by finding the moles of CO2 and H2O but after that step i cannot find the next step. The answer to the problems are C3H4O3 and C6H8O6
 
Last edited:

Answers and Replies

  • #2
mgb_phys
Science Advisor
Homework Helper
7,774
12
You can work out how many moles of C and H are produced from the masses of the CO2 and H2O given, ignore the oxygen because you don't know how much came from the air.
You know how many moles of the substance there were so you can work out how many carbon and hydrogen it had.
You have the molecular mass so any difference between the amount of carbon and hydrogen you worked out must be oxygen.
 
  • #3
1,752
1
1) find the grams of C from CO2, find the grams of H from H2O

2) Original amount - grams of (C + H) = Grams of O

3) find the moles of C from CO2, H from H2O, O from molar mass of O

4) CxHyOz ... divide by the smallest amount of moles and manipulate your findings till you have a whole number which gives you your Empirical Formula

5) MW/EW = some value = Multiply your EF by this value.
 
Last edited:
  • #4
1,752
1
i just worked it ... it works, have you solved it yet?
 

Related Threads for: What are the empirical and molecular formulas of the compound

Replies
1
Views
12K
Replies
5
Views
7K
Replies
2
Views
5K
Replies
2
Views
1K
Replies
100
Views
7K
Replies
8
Views
1K
Replies
2
Views
741
Top