Question

How many moles of electrons weight one kilogram?

(A) $6.02 \times 10^{23}$

(B) $\frac{1}{9.108} \times 10^{31}$

(C) $\frac{6.023}{9.108} \times 10^{54}$

(D) $\frac{1}{9.108 \times 6.023} \times 10^{8}$

Answer 1

ANSWER : Here, The correct answer of this question will be option (D).

SOLUTION —

Mass of an clectron $=9.108 \times 10^{-31} kg$

$\therefore$ Mass of 1 mole of elcctron

$\begin{array}{l}=6.02 \times 10^{23} \times 9.108 \times 10^{-2+} kg \\=6.02 \times 9.108 \times 10^{-8} kg\end{array}$

$\therefore$ No of moles in 1 kg of electrons

$= \frac{1}{6.02 \times 9.108 \times 10^{-8}}=\frac{10^{8}}{6.02 \times 9.108}$