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} $ .
