1. Percentage Composition

2. Calculate the percentage composition of C3H7NO2
Step 1: Find the molar mass of C3H7NO2
M = 3(12.01) + 7(1.01) + (14.01) + 2(16.00)
= g/mol

3. Step 2: Find the % of each element by dividing the mass of each element by the total mass
3(12.01)
89.11
%C = x 100 = %
%H = x 100 = 7.93%
%N = x 100 = 15.72%
%O = x 100 = %
7(1.01)
89.11
1(14.01)
89.11
2(16.00)
89.11

4. Calculate the mass of aluminum in 28 g of Aluminum Oxide
Step 1: Calculate the molar mass of aluminum oxide.
Al2O3
M = 2(26.98) + 3(16.00)
= g/mol

5. Step 2: Calculate the % mass of aluminum in aluminum oxide.
%Al = x 100 = 52.92%
2(26.98)
101.96

6. Step 3: Find the mass of aluminum in 28g of aluminum oxide.
mAl = x 28g = 15g
52.92
100

7. Alternate Solution = Al on top Total on bottom = mAl = 15 g MAl MTotal
2(26.98)
101.96
mAl
28g