Question

How many moles of $e^{-}$s weigh one kilogram?

• A. $\frac{1}{9.108\times 6.023}\times {10}^8$
• B. $\frac{6.023}{9.108}\times {10}^{54}$
• C. $\frac{1}{9.108}\times {10}^{31}$
• D. $6.023\times {10}^{23}$

Answer 1

The correct option is A

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

Mass one one $e^{-}=9.108\times {10}^{-31}kg$

$1kg=\frac{1}{9.108\times {10}^{-31}}$ electrons.

Moles of electrons:

$\frac{1}{9.108\times {10}^{-31}}\times \frac{1}{6.023\times {10}^{23}}=\frac{1}{9.108\times 6.023}\times {10}^8$