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

Explanation:

We are given;

The mass of the compound C16H18N2O4S as 540 mg Molar mass of C16H18N2O4S = 334.4 g/mol

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

We know that 1 mole of a compound contains molecules equivalent to the Avogadro's number. That is, 1 mole of a compound = 6.022 * 10^23 molecules Therefore, 1 mole of C16H18N2O4S = 6.022 * 10^23 molecules

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