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

Molar mass of each substance

  • Thread starter nobahar
  • Start date
  • #1
493
2
Hello!
How many moles of each substance are contained in 88g of carbon dioxide?
Since it's CO2:
Ar of carbon= 12
Ar of oxgen = 16
Mr of Carbon dioxide = 44
88g/44= 2 Mol of CO2 formula units
Since the ratio is 1:2 carbon to oxygen:
(88/3)/12=22/9 Mol of Carbon
(i.e. 1/3 of 88g is how many grams carbon represents?)
and
(176/3)/16=11/3 Mol of oxygen
(i.e. 2/3 of 88g is how many grams oxygen represents)
Is this right? Any replies much appreciated! Thanks in advance!
Jay
 

Answers and Replies

  • #2
73
0
Ar of carbon= 12
Ar of oxgen = 16
Mr of Carbon dioxide = 44
88g/44= 2 Mol of CO2 formula units
Since the ratio is 1:2 carbon to oxygen:
This part is good, but afterward I'm not quite sure how your calculations go. Here's a simpler way, I believe:

You have 2mol of CO2. This means you have 2mol C and 4mol O (each atom is multiplied by the mole amount (2).)
2mol C = 2mol(12g/mol) = 24g
4mol O = 4mol(16g/mol) = 64g
Make sure all masses add up to the total mass (88g), and that's it! It gets a bit more complicated for larger molecules (e.g. H3PO4) or with messier numbers (8.57mol rather than 2mol) but they should work the same way.

So this is the mass of each; if you wanted percent by mass (common for high school or basic college chem):
C = 24g/88g x 100 = ~27%
O = 64g/88g x 100 = ~73%
 
Last edited:
  • #3
493
2
I don't know where they were going either.
Thanks for the help though!
 

Related Threads on Molar mass of each substance

  • Last Post
Replies
7
Views
3K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
12
Views
9K
  • Last Post
Replies
4
Views
11K
  • Last Post
Replies
7
Views
2K
  • Last Post
Replies
3
Views
6K
  • Last Post
Replies
4
Views
5K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
1
Views
1K
Top