# What is the number of representative particles in .400 mol KCl?

There are $0.4$ $\times$ ${N}_{A}$ potassium cations, and an equal quantity of chloride anions.
But what is ${N}_{A}$? ${N}_{A}$ is simply $\text{Avogadro's number}$, 6.022140857 × 10^23. This number has the property that ${N}_{A}$ ""^12C atoms has a mass of $12.00$ $g$ precisely. ${N}_{A}$ is thus the link between atoms and molecules, about which we can only conceive, and the macro world of grams and kilograms, and litres, that which we can measure in a laboratory.
What is the mass of $0.400$ $m o l$ $K C l$, given that $K C l$ has a mass of $74.55 \cdot g \cdot m o {l}^{-} 1$?