Question

Which of the following contain same number of molecules?
(1) $0.1mol$ of $C{O}_2$
(2) $3.2g$ of $O_2$
(3) $0.1g$-atom of helium gas
(4) $11.2L$ of $S{O}_2$

• A. 1, 2 and 3 are correct
• B. 1 and 2 are correct
• C. 2 and 4 are correct
• D. 1 and 3 are correct

Answer 1

Answer: (A)

1. Number of molecules in $0.1$ mole of $C{O}_2$
$=0.1\times N_A=0.1N_A$
2. Number of molecules in $3.2g$ of $O_2$
$=\frac{3.2}{32}\times N_A=0.1N_A$
3. Number of molecules in $0.1g$-atom of He gas
$=0.1\times N_A=0.1N_A$
4. Number of molecules in $11.2L$ of $S{O}_2$
$=\frac{11.2}{22.4}\times {\dot{N}}_A$
$=\frac{N_A}{2}$
$\therefore 0.1mole$ of $C{O}_2,3.2g$ of $O_2$ and $0.1g$-atom of He gas have the same number of molecules, ie, $0.1N_A$