Question

1 mL of water contains 20 drops. Then number of molecules in a drop of water is _______ molecules.

(A) 6.023 x 10²³ 

(B) 1.376 x 10²⁶ 

(C) 1.344 x 10¹⁸ 

(D) 4.346 x 10²⁰

Answer 1

Correct  option: (C) 1.344 x 10¹⁸ 

22.4 L of water contains N_A molecules

22400 mL of water contains N_A molecules

1 mL of water i.e., 20 drops contains

\(\cfrac{N_A}{22400} \) molecules

∴ 1 drop contains \(\cfrac{N_A}{22400\, \times 20} \) = \(\cfrac{6.022\, \times\, 10^{23}}{448\, \times 10^3} \)

= 1.344 x 10¹⁸