Question

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

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

Answer 1

(i) Mass of one electron = 9.10939 × 10^–31 kg 

∴ Number of electrons that weigh 9.10939 × 10^–31 kg = 1

Number of electrons that will weigh 1 g = (1 × 10^–3 kg)

= 0.1098 × 10^{–3 + 31} 

= 0.1098 × 10²⁸ 

= 1.098 × 10²⁷ 

(ii) Mass of one electron = 9.10939 × 10^–31 kg 

Mass of one mole of electron = (6.022 × 10²³) × (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^–19C) (6.022 × 10²³) 

= 9.65 × 10⁴ C