Question

How many moles of electrons weigh one kilogram?

(A) 6.022 x 10²³

(B) \(\cfrac{1}{9.108}\) x 10³¹

 (C) \(\cfrac{6.022}{9.108}\) x 10⁵⁴

(D) \(\cfrac{1}{9.108\times6.022}\) x 10⁸

Answer 1

Correct option: (D) \(\cfrac{1}{9.108\times6.022}\) x 10⁸

1 mole ≡ 6.022 x 10²³ electrons

One electron weighs 9.108 x 10^-31 kg

∴ 1 mole of electrons weighs

6.022 x 10²³ x 9.108 x 10^–31 kg

∴ Number of moles that will weigh 1 kg

= \(\cfrac{1}{6.022\,\times \,10^{23}\, \times \,9.108\, \times\,10^{-31}}\) moles

∴ \(\cfrac{1}{6.108 \,\times\,6.022}\) x 10⁸ moles of electrons will weigh one kilogram.