Question

How do you convert $1.55moles$ of water to grams?

Answer 1

A mole is a systematic unit to express a quantity of a substance. A mole is the amount of substance taken in amount equal to the molar mass or molecular weight of the substance.

Complete step by step answer:
Mole is a convenient or appropriate unit of measurement for describing the amount of a substance in a chemical field. As we measure the weight of an apple or ball in grams and kilogram, a bottle of milk in litres, the weight of a molecule or compound related to chemistry is measured in moles.
The mentioning of moles of a compound gives a more specific information rather than grams or milliliters of the substance. Further knowing the moles of a substance we can deduce the molecular weight in grams or milligrams. Also we can calculate the volume of the substance in litres or milliliters.
According to the mole concept a mole of a substance contains that amount of substance which is equal to the molar mass of the substance. Thus we can say that one mole of carbon contains $12g$ of carbon which is the molar mass of carbon. Also one mole of water contains $18g$ of water which is the molar mass of water.
Here we need to determine the amount of water present in a certain mole of water. So we need to determine first the molar mass of water. The molar mass of water (${H_2}O$) is calculated from the atomic masses of the atoms present in water. The molar mass of water = $2{\text{ }} \times$ atomic mass of $H$ + atomic mass of $O$.
Atomic mass of $H$ is $1.008g/mol$ and the atomic mass of $O$ is $15.999g/mol$ as obtained from the periodic table.
Thus the molar mass of water =$2 \times 1.008 + 15.999 = 18.015g/mol$.
Therefore, one mole of water = $18.015g/mol$
Hence $1.55moles$ of water = $18.015 \times 1.55 = 27.923g$

Note:
The mole calculation is very useful for setting up reaction. Using the number of moles we can determine the amount of the reactants and the amount of products produced from a chemical reaction.