Formula Weights


by courtrigrad
Tags: formula, weights
courtrigrad
courtrigrad is offline
#1
Oct18-04, 06:19 PM
P: 1,239
Hello all

I encountered the following problems:

What is the formula weight of:

a. potassium phosphate

b. iron(III) oxide

c. diphosphorous pentasulfide

I know that the formula for (a) is K2S04. Hence I know there are 2K's 1 S and 4 O's. After obtaining the atomic masses, I sum them all up. The answer is 212.3 amu but I dont get this.

Any help would be appreciated

Thanks!
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wolfson_1123
wolfson_1123 is offline
#2
Oct19-04, 04:42 AM
P: 14
K=39.098
S=32.060
O=15.999

So:

K2=78.197
S=32.060
O4=63.998

So:

K2SO4=174.254

Do the same for the other ones.
chem_tr
chem_tr is offline
#3
Oct19-04, 07:59 AM
Sci Advisor
PF Gold
chem_tr's Avatar
P: 613
The rest corresponds to two moles of water ions, as 2*18=36 grams/mol. So the total formula should be like K2SO4.2H2O.


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