Ncert Exercises & Solutions

2.1 (i) Calculate the number of electrons which will together weigh one gram.

(ii) Calculate the mass and charge of one mole of electrons.

The number of electrons which will weigh 1 g is $= \frac{{10^{-}}^{3}}{9.1 x 10^{- 31}} = 1.098 \times 10^{27} .$

(ii)Mass of one electron = 9.10939 × $10^{- 31}$ kg

Mass of one mole of electron = (6.022 × $10^{23}$ ) × (9.10939 × $10^{- 31}$ kg)
= 5.48 × $10^{- 7}$ kg

Charge on one electron = 1.6022 × $10^{- 19}$ coulomb

Charge on one mole of electron = (1.6022 × $10^{- 19}$ C) (6.022 × $10^{23}$ )
= 9.65 × $10^{4}$ C