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

(2) : Molar mass of $O_{2} = 32gmol^{- 1}$

$32gofO_{2} = 6.023 \times 10^{23}$molecules

$40gofO_{2} = \frac{6.023 \times 10^{23} \times 40}{32} = 7.529 \times 10^{23}$molecules

Mass of $6.023 \times 10^{23}$molecules of $CO_{2} = 44g$

Mass of $7.529 \times 10^{23}$molecules of $CO_{2}$

$= \frac{44 \times 7.529 \times 10^{23}}{6.023 \times 10^{23}} = 55g$