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!
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.
The rest corresponds to two moles of water ions, as 2*18=36 grams/mol. So the total formula should be like K_{2}SO_{4}.2H_{2}O.