Question

Calculate the number of moles present in $80g$ of calcium. (atomic mass of calcium $=40u$)

Answer 1

Hint: Mole concept which gives a relationship between number of moles, weight and the molar mass of a compound. Molecular mass is calculated by adding up the atomic masses of all the elements bound in a molecule, multiplying each with the number of atoms in the molecule. A mole is defined as a unit which is used to determine the amount of atoms, ions and molecules.

Formula used:
$n=\dfrac{W}{M}$
where, $n$ is the number of moles, $W$ is the weight and $M$ is the molar mass.

Complete step by step answer:
Here, it is given that the weight of calcium is $80g$ and the atomic mass of calcium is $40u$ .
To calculate the number of moles, you should know about the concept, which states that,
$n=\dfrac{W}{M}$
where, $n$ is the number of moles of calcium, $W$ is the weight of calcium and $M$ is the molar mass of calcium.
Now, substituting the values in the above formula, we get,
$n=\dfrac{80}{40}$
$\Rightarrow n=2$

Therefore, the number of moles present in $80g$ of calcium is $2\,mol$ .

Note: Mole is defined as the scientific unit which is used to measure large quantities of atoms, ions, and molecules. It is defined as the amount of substance present in sample, and
$1\,mole=6.022\times {{10}^{23}}$ particles. This number is known as Avogadro’s number $({{N}_{A}})$.
It is calculated as the weight of the compound per molar mass of that compound.
Molar mass is defined as the addition of atomic masses of atoms combined in a molecule.
The mole is very important because it helps to study atoms, molecules and ions.
The molar mass is calculated in $g\,mo{{l}^{-1}}$ .
The molar mass of any compound is calculated by adding the atomic mass of all the elements present in the compound .