(i) Calculate the number of electrons which will together weigh one gram. (ii) Calculate the mass and charge of one mole of electrons.

Question 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.
Answer
(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 × 10 ²⁸
= 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^-19 C) (6.022 × 10²³) = 9.65 × 10⁴ C