Question
How many moles of electron weigh one kilogram?
A.
$$6.023 \times {10^{23}}$$
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 :
$$\frac{1}{{9.108 \times 6.023}} \times {10^8}$$
Solution :
TIPS/Formulae:
(i) Mass of one electron $$ = 9.108 \times {10^{ - 31}}{\text{kg}}$$
(ii) $$1$$ mole of electron $$ = 6.023 \times {10^{23}}$$ electrons
Weight of $$1$$ mole of electron
= Mass of one electron x Avogadro Number
$$ = 9.108 \times {10^{ - 31}} \times 6.023 \times {10^{23}}{\text{kg}}$$
∴ No. of moles of electrons in $$1$$ kg
$$\eqalign{
& {\text{ = }}\frac{1}{{9.108 \times {{10}^{ - 31}} \times 6.023 \times {{10}^{23}}}} \cr
& = \frac{1}{{9.108 \times 6.023}} \times {10^8} \cr} $$