Question

The mass of the electron is given $9.1\times {10}^{-31}kg$. Find the order of magnitude of the number of electrons of $1kg$.

• A. ${10}^{31}$
• B. ${10}^{-30}$
• C. ${10}^{30}$
• D. ${10}^{-31}$

Answer 1

The correct option is C ${10}^{30}$

Let n be the required number of electrons.
Thus, $n\times (9.1\times {10}^{-31})=1$
or $n=1.1\times {10}^{30}$
According to rule of order of magnitude, as $1.1<5$ so it will be taken as 1.
Thus, $n={10}^{30}$