Some Basic Concepts Of Chemistry Question 311

Question: The number of water molecules present in a drop of water (volume 0.0018 ml) at room temperature is [DCE 2000]

Options:

A) $ 6.023\times 10^{19} $

B) $ 1.084\times 10^{18} $

C) $ 4.84\times 10^{17} $

D) $ 6.023\times 10^{23} $

Show Answer

Answer:

Correct Answer: A

Solution:

Density $ =\frac{Mass}{Volume} $ ; $ 1=\frac{g}{ml} $ or $ g=ml $

0.0018ml = 0.0018gm No. of moles $ =\frac{weight}{\text{Molecular weight }}=\frac{0.0018}{18}=1\times {10^{-4}} $

$ \therefore $ No. of water molecules = $ 6.023\times 10^{23}\times 1\times {10^{-4}} $

$ =6.023\times 10^{19} $ .



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