Question

Calculate the number of moles of electrons present in $54.6\text{g}$ of electrons.
(Take $N_A=6\times {10}^{23}$)

• A. $5.0\times {10}^5\text{mol}$
• B. $2.0\times {10}^4\text{mol}$
• C. $1.0\times {10}^5\text{mol}$
• D. $1.0\times {10}^4\text{mol}$

Answer 1

The correct option is C $1.0\times {10}^5\text{mol}$

We know,
Mass of one electron $=9.1\times {10}^{-31}\text{kg}$
So, mass of one mole of electron $=9.1\times {10}^{-31}\times 6.022\times {10}^{23}\text{kg}$

The number of moles in $54.6\times {10}^{-3}\text{kg}$ electron
$=\frac{54.6\times {10}^{-3}}{9.1\times {10}^{-31}\times 6\times {10}^{23}}\text{mol}$
$=1.0\times {10}^5\text{mol}$