How many molecules are contained in two 540.−mg tablets of penicillin (c16h18n2o4s, molar mass 334.4 g/mol)? report your answer with the appropriate number of significant figures.

9.72 × 10^20 molecules

We are given;

We are required to determine the number of molecules in 540 mg of penicillin.

But, 1 mole = 334.4 g

Thus, 334.4 g of C16H18N2O4S contains 6.022 × 10^23 molecules

Mass of C16H18N2O4S = 540 mg or 0.54 g

Molecules in 0.54 g will be;

= (0.54 g ÷ 334.4 g) × 6.022 × 10^23 molecules

= 9.72 × 10^20 molecules

i believe the answer is a.