Question

What is the mass of carbon dioxide which contains the same number of molecules as are contained in $40g$ of oxygen?

• A. $40g$
• B. $55g$
• C. $32g$
• D. $44g$

Answer 1

Answer: (B)

Molar mass of $O_2=32gmo{l}^{-1}$
$32g$ of $O_2=6.023\times 10^{23}$ molecules
$40g$ of $O_2=\frac{6.023\times 10^{23}\times 40}{32}$
$=7.529\times 10^{23}$ molecules
Mass of $6.023\times 10^{23}$ molecules of $C{O}_2=44g$
Mass of $7.529\times 10^{23}$ molecules of $C{O}_2$
$=\frac{44\times 7.529\times 10^{23}}{6.023\times 10^{23}}=55g$