the question is like this:
"The empirical formula for a compound is C2H3As3Cu2O8 with a molar mass of 1013.71g. What is the molecular formula?"
i dont understand how you to find the molecular formula here -_-
2007-12-13 11:29:29 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
Firstly you need a periodic table. Accompanying each of the elements in question are two numbers: the atomic number, and the mass number. The mass number should be roughly twice the size of the atomic number. The mass number represents the mass in grams of one mole of that element. Regardless, to solve the problem, you should follow these steps:
- Look up the mass number of the first element and multiply it by the subscript
- Do the same for all the elements and add them together
- You should end up with a number that is approximately a multiple of the mass given eg 506g or 2026g.
- Now you should divide the mass given by the mass you just found.
- For instance the mass you found may hav been 506. 1013/506=2. This means that you need to double all the subscripts on the empirical ormula to get the molecular formula.
The main difficulty here is understanding the mole concept an its relationship with molecular formulas and stoichiometry. You should read up on that.
2007-12-13 11:40:26 · answer #1 · answered by Derek D 1 · 0⤊ 0⤋
The molecular formula must be an exact multiple of the empirical formula. So work out the mass of one empirical formula's worth, see how many times that goes into the molar mass, and that's the number of times you need to multiply the empirical formula by.
Easier done than said. Simple example: empirical formula, HO (mass 17). Molar mass 34. So it must be (HO)2 or H2O2.
2007-12-13 11:38:27 · answer #2 · answered by Facts Matter 7 · 0⤊ 0⤋
you have to find the empirical weight for C2H3As3Cu2O8 so...
C= 2(12)= 24
H= 3(1)= 3
As= 3(74.9)= 224.7
Cu= 2(63.5)= 127
O= 8(16)= 128
Add up all the weights to find the empirical weight which is 506.7
take the molecular weight given and divide it by the empirical weight 1013.7/506.7= 2
now take two and multiply the empirical formula 2 (C2H3As3Cu2O8)= the molecular formula C4H6As6Cu4O16
2007-12-13 11:42:27 · answer #3 · answered by travis_rose5 1 · 0⤊ 0⤋
the empirical numbers are like a ratio to the total weight. multiply the subscript numbers to its respective element and find out the total molecular weight of that. then compare that to the 1013.71 and multiply accordingly. if its the same then the empirical is the molecular.
2007-12-13 11:34:10 · answer #4 · answered by wwing03 2 · 0⤊ 1⤋
Go to the link...
rickards.leon.k12.fl.us/Teachers/Chemical Composition 7.htm
By the way, wwing03... is lying.
Hope this helps,
Cheers, Sam :)
2007-12-13 11:34:01 · answer #5 · answered by Anonymous · 0⤊ 0⤋
find the mass of the empirical unit.
figure out how many empirical units are in a molecular unit.
write the molecular formula
i dunno wat i just said
(i looked online)
2007-12-13 11:33:46 · answer #6 · answered by Anonymous · 0⤊ 1⤋
its complicated... use your textbook
2007-12-13 11:31:55 · answer #7 · answered by Anonymous · 0⤊ 1⤋