Each molecule of ampicillin contains 16 atoms of carbon (plus other atoms). The mass percent of carbon in ampicillin is 55.00%. What is the molar mass of ampicillin?

A) 698.8 g/mol

B) 105.7 g/mol

C) 192.2 g/mol

D) 290.9 g/mol

E) 349.4 g/mol

do i divide the mass of carbon by the mass percent?

The answer is E) 349.4 g/mol

Yes, divide the mass of carbon by the mass percent

Step 1. Calculate the mass of 16 atoms of carbon in ampicillin.

Step 2. Make a proportion and divide the mass of carbon by the mass percent.

Step 1.

Atomic mass of carbon is 12.01 g/mol

Since there are 16 atoms of carbon, the mass of carbon in ampicillin will be:

16 * 12.01 g/mol = 192.16 g/mol

Step 2.

Make a proportion. 192.16 g/mol are 55%. How many grams are 100% (ampicillin mass is 100%):

192.16 g/mol : 55% = x : 100%

x = 192.16 g/mol : 55% * 100%

x = 349.38 g/mol

x ≈ 349.4 g/mol

First, we calculate the mass of Carbon ampicillin contains:

16 moles of atoms x 12 grams per mole

= 192 grams

192 is 55% of the total mass of ampicillin.

Total mass = 192 / 0.55

= 349 g/mol

The answer is E.