Question

How many molecules are contained in 1.55 moles of methane, CH 4 ?

Answer 1

Avogadro's law states that in one mole of a substance, there are $6.022 \times 10^{23}$ molecules.

This means that in 1.55 moles, there are $1.55(6.022 \times 10^{23})=\boxed{9.33 \times 10^{23} \text{( to 3 sf)}}$