Question

Calculate the formula mass for each of the following compounds

1. CS2

2. C6H12O6

3. Fe(NO3)3

4. C7H16

Using 5 sig figs

Answer 1

1. CS2

MW = MW of C + 2* MW of S

MW = 12 + 2*32.065

MW = 76.130 g/mol

2. C6H12O6

MW of C6H12O6 = 6*MW of C + 12*MW of H + 6*MW of O

MW of C6H12O6 = 6*12 + 12*1.00794 of H + 6*15.999

MW of C6H12O6 = 180.0892 g/mol

5 sig fig --> 180.09 g/mol

3. Fe(NO3)3

MW = Fe + 3(N) + 3(3)O

MW = Fe + 3(N) + 3(3)O

MW = 55.845 + 3*14.0067 + 9*15.999

MW = 241.8561 --> 241.86 (5 sig fig)

MW Fe(NO3)3 = 241.86 (5 sig fig)

4. C7H16

MW = 7*c + 16*H = 7*12 + 16*1.00794 = 100.12704

MW = 100.13 g/mol