chemistry calculation basic

Question

how many moles and how many molecules of lipids is included in one bacteria cell which mass is 2.10^-11 gram? We assume that such a cell contains 2% of lipids and that the average molar mass of lipids is 750 g/mol.

Answer 1

Mass of lipids = 2% x 2x10^-11g = 4x10^-13 g

Moles of lipids = 4x10^-13g x 1 mol / 750 g = 5.33x10^-16 mols = 5x10^-16 mols (1 sig.fig.)