Hey Chris, I was wondering if you could help me. Tomorrow I have a Chemistry test that is basically the deciding factor, possibly, whether or not I fail. LOL.
It's on: formula mass, molar mass, percent composition, emperical formulas, and molecular formula.
I was just wondering if you had any hints or anything to help me remember which is which. I know how to do all of them, but I can't tell which one is which, yanno? :)
Sure, he ya go........dracschickMarch 27 2006, 22:56:53 UTC
Molar Mass = molecular weight = larger # on periodic table.
for example, the molar mass (MW) of CO2 is 12 + 2(16) = 44 grams/1mol
6 grams of CO2 is 6/44 or 0.14 mol.
In general:
1. grams/MW is moles
2.Moles x MW is grams
Change % to grams, then change grams to moles (#1), then divide each moles by smallest # of moles to get numbers for empirical formula.
The molecular formula is the molecular weight of the empirical formula multiplied by a whole number.
To go backwards:
find the molecular weight of the entire compound using the periodic table. For example CO2 is 44g/mol
There is 12/44 or 27% Carbon There is 32/44 or 72% Oxygen.
Your % should add up to 100%
After you find the empirical formula, you can then find the % of each of the elements. It should add up to 100%. so, therefore, you can check yourself.
Comments 17
I love Dracula!
Ah!
When Gary Oldman did that one films of it in the 1990s...AH!
He made a hottie vampire in his youth form.
Reply
Reply
^^
Reply
Reply
Reply
Reply
Reply
Reply
skeletal, corpse!Erik turns me on...
Reply
Reply
It's on: formula mass, molar mass, percent composition, emperical formulas, and molecular formula.
I was just wondering if you had any hints or anything to help me remember which is which. I know how to do all of them, but I can't tell which one is which, yanno? :)
Thanks so much!
Reply
for example, the molar mass (MW) of CO2 is 12 + 2(16) = 44 grams/1mol
6 grams of CO2 is 6/44 or 0.14 mol.
In general:
1. grams/MW is moles
2.Moles x MW is grams
Change % to grams, then change grams to moles (#1), then divide each moles by smallest # of moles to get numbers for empirical formula.
The molecular formula is the molecular weight of the empirical formula multiplied by a whole number.
To go backwards:
find the molecular weight of the entire compound using the periodic table. For example CO2 is 44g/mol
There is 12/44 or 27% Carbon
There is 32/44 or 72% Oxygen.
Your % should add up to 100%
After you find the empirical formula, you can then find the % of each of the elements. It should add up to 100%. so, therefore, you can check yourself.
Any other questions, just ask:)
Reply
Leave a comment