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) 1 electron weigh 9.1x10^-31kg
    so 1g ie,10^-3 kg contains (1/9.1x10^-31) x 10^-3 =1.09x10^-27 electrons
ii) 1 mole of es =6.022x10^23 es
     1 e has mass 9.1x10^-31kg
    so 1 mole will weigh 9.1x10^-31kg x6.022x10^23 kg= 5.48x 10 ^-7 kg
     charge of 1 e = 1.6x10^-19 C
  so 1 mole will have charge= Avagadro no x1.6x10^-19 =9.65x10^4 C

Answer 2

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 × 1031 x 10 -3

                                                                                     = 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 × 10–19 C) X (6.022 × 1023) = 9.65 × 104 C