Question

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

Answer 1

Answer is: 7,5·10²¹ naphthalene molecules.
m(C₁₀H₈) = 1,64 g.
n(C₁₀H₈) = m(C₁₀H₈) ÷ M(C₁₀H₈).
n(C₁₀H₈) = 1,64 g ÷ 128,17 g/mol.
n(C₁₀H₈) = 0,0125 mol.
N(C₁₀H₈) = n(C₁₀H₈) · Na.
N(C₁₀H₈) = 0,0125 mol · 6,022·10²³ 1/mol.
N(C₁₀H₈) = 7,5·10²¹.
Na - Avogadro number.