Question

How many water molecules are in 4 moles of water.

Answer 1

Hint: No of molecules of certain compounds can be calculated with the help of Avogadro number. Avogadro number means that one mole of any compound has $6.023 \times {10^{23}}$. molecules.

Complete step-by-step answer:
The Avogadro constant is the proportionality factor that relates the number of constituent particles ( molecules, atoms or ions) in a sample with the amount of substance present in the sample. Its SI unit is the reciprocal mole, and it is well-defined as $NA = 6.023 \times {10^{23}}$ mol−1. It is called after the Italian scientist Amedeo Avogadro. Although this is called Avogadro's constant, he was not the chemist who determined its value. Stanislao Cannizzarro explained exactly this number four years after

Avogadro's death while at the Karlsruhe Congress in 1860.
Now we understand that 1 mole of any substance will have $6.023 \times {10^{23}}$.
So to find 4 mole of water we will multiply.
$4 \times 6.023 \times {10^{23}} = 2.4 \times {10^{24}}$

The numeric value of the Avogadro constant expressed in reciprocal mole, a dimensionless number, is called the Avogadro number, sometimes denoted N or NO which is thus the number of particles that are contained in one mole, $6.023 \times {10^{23}}$.

Note: In chemistry we define the molar mass of a chemical compound as the mass of a sample of that compound divided by the amount of substance in that specific sample, measured in moles. The molar mass is a bulk quantity of any substance, not molecular, property of a substance.