Question

How many grams of sodium are in $25$ moles?

Answer 1

We know that on multiplying molar mass of substance to the number of molecules provided in the problem we get grams of substance contained in a particular mole of a substance. Atomic weight when multiplied to the number of mole results in it's gram weight.

Complete step-by-step answer: Here mole is standard unit of measurement of amount of substance. Substances react in simple ratios of their respective mole. One mole consist of Avogadro number of atoms that is $6.022\times 10{}^\text{2}{}^\text{3}\text{ }atom$ The amount of atom in $12$ gram of $Carbon-12$ is same as a Avogadro's number as it's for $1$ mole of a carbon that is a sample of $12$ gram of a carbon which is equal to it's $1$ mole. It is similar to a dozen.
Thus the molar mass is amount of gram present in one
mole of substance. It's also average atomic weight of substance, for example carbon has atomic weight of $12$ amu, so a molar mass is given as $12$ gram per mole. The formula for conversion of mole to gram is given as:
$Gram~=~mole~\times atomic\text{ }weight$
We have here given $25$ moles of sodium atom
Therefore here $gram~=~1\text{ }mole\text{ }\times \text{ }atomic\text{ }weight\text{ }of\text{ }a\text{ }sodium\text{ }atom$
Also, atomic weight of a sodium atom which is $23$ (number of a neutron $+$ number of a proton)grams $=\text{ }25mole\text{ }\times \text{ }23\text{ }=\text{ }575\text{ }grams$
Thus, $575$ grams are contained in a $25$ mole of a sodium atom.

Note: Note that calculating mass is known as gram atomic mass. It's mass of one mole of element example; gram atomic mass of a hydrogen which is $1$ gram for one mole of hydrogen. It's the same as the atomic weight of a hydrogen atom.