Question

A throat lozenge contains 5.0 mg of menthol, which has the formula c10h20o.

Answer 1

A) 
the molecular formula of menthol is C₁₀H₂₀O 
molar mass of menthol is (12x10) + (1x20) + 16 = 156 g/mol
number of moles of menthol in 156 g - 1 mol
In 1 g of menthol number of moles - 1/156 
Therefore in 5.0 g of menthol - 1/156 x 5 = 0.032 mol
therefore in 5.0 g of menthol there are 0.032 mol of menthol

b)
Molar mass of menthol - 156 g/mol
1 mol of menthol weighs 156 g
Therefore 1.56 mol of menthol weighs - 156 g/mol x 1.56 mol = 243.36 g