Question

A mothball, composed of naphthalene (C10H8), has a mass of 1.52g. How many naphthalene molecules does it contain?

Answer 1

The molar mass of naphthalene is calculated as follows,
                          10 x (12.01 g/ mol) + 8 x (1.01 g/mol) = 128.12 g/mol
Divide the given mass by the molar mass to determine the number of moles of naphthalene present in the ball.
                                  n =  1.52 g / 128.12 g/mol  = 0.01186 mole
Multiply the number of moles to number of moles per mole.
                                 (0.01186 mol) x (6.022 x10^23 molecules / mole) = 7.14 x 10^21 molecules