Question

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

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

Answer 1

Answer: (B)

$55\,g$

Answer 2

Molar mass of $O_{2} = 32\, g\, mol^{-1}$ $32\, g\,$ of $\,O_{2} = 6.023 \times 10^{23}$ molecules $40 \,g$ of $O_{2}=\frac{ 6.023\times10^{23} \times40}{32}$ $= 7.529\times10^{23}$ molecules Mass of $6.023\times10^{23}$ molecules of $CO_{2} = 44\,g$ Mass of $7.529 \times 10^{23}$ molecules of $CO_{2}$ $= \frac{44\times7.529\times10^{23}}{6.023\times10^{23}} = 55g$