A mothball, composed of naphthalene (c10h8), has a mass of 1.64 g. part a how many naphthalene molecules does it contain?

The molar mass of Naphthalene is 128g/mol

Therefore; a mass of 1.64 g of Naphthalene contains'

= 1.64g/128 g

= 0.0128 moles

But, from the Avogadro's law 1 mole of a substance contains 6.022 * 10^23 particles

Therefore 1 mole of Naphthalene contains 6.022*10^23 molecules

Hence; 0.0128 moles * 6.022 * 10^23 molecules

= 7.716 * 10^21 molecules