# Chemistry Percent Composition of Compounds?

I have missed a day in my chemistry class and am completely behind on how to find the percent composition of compounds. Can someone please help me determine the percent composition (of each element) for these compounds:

AlF3 Fe(HCO3)2 Fe3O4

It'd be great if you could explain how you did at least one of them. I'm sure I'm missing a really small point!

Relevance
• david
Lv 7
4 weeks ago

Fe(HCO3)2   ...  begin by finding the molar mass.

1 Fe  ===  1(55.85)  =  55.85

2 H  ===  2(1.00)  =  2.00

2 C  ===  2(12.0)  =  24.0

6 O  ===  6(16.0)  =  96.0

======================

molar mass =   - - - -   177.85

% Fe  =  55.85/177.85  X 100% =

% H  =  2.00/177.85 X 100%  =

% C  =  24.0/177.85 X 100%  =

% O  =  96.0/177.85 X 100%  =

....  use your calculator ,, yu can do the rest

• Fern
Lv 7
4 weeks ago

AlF3: sum up atomic weights (I rounded to the nearest whole number)

1Al + 3F = 1(27) + 3(19) = 27 + 57 = 84

Percent Al = 27/84 *100= 32%Al

Percent F = 57/84 *100 = 68%

Fe(HCO3)2 ;

1Fe + 2H + 2C + 6O

1(56) + 2(1) + 2(12) + 6(16) = 178

Percent Fe = 56/178 *100 = 31.5%

Percent H = 2/178 * 100 = 1%

Percent C = 24/178 *100 = 13.5%

Percent O = 96/178 * 100 = 54%