Question

How many moles of electrons weigh one kilogram? (mass of electron $=9.108\times 10^{-31}kg$, Avogadro number $=6.023\times 10^{23})$

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

Answer 1

Answer: (D)

As mass of one electron $=9.108\times 10^{-31}kg$
So, $1kg$ of electrons $=1/9.108\times 10^{-31}$
$=\frac{10^{31}}{9.108\times 6.022\times 10^{23}}mol$
$=\frac{10^{31-23}}{9.108\times 6.022}mol$
$=\frac{10^8}{9.108\times 6.022}mol$