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# Calculate the number of electrons which will together weigh one gram.

$\begin{array}{1 1}(a)\;1.098 \times 10^{25}\\(b)\;1.098 \times10^{28}\\(c)\;1.098 \times 10^{20}\\(d)\;1.098 \times10^{27}\end{array}$

$Mass\; of\; one\; electron = 9.10939 \times 10–31 kg$
$Number\; of \;electrons\; that\; weigh\; 9.10939 \times 10–31 kg = 1$
$Number \;of \;electrons\; that\; will \;weigh\; 1 g = (1 \times 10–3 kg)$
$\large\frac{1}{{9.10939} \times10–31 \times 1\times10^{-3}} kg$
$= 0.1098 \times 10^{–3 + 31}$
$= 0.1098 \times 10^{28}$
$= 1.098 \times 10^{27}$