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

Molar mass of carbon dioxide $=12+2\times 16=44g$

Molar mass of $O_2=2\times 16=32g$

Number of molecules in 32 g oxygen = $N_A$

Number of molecules in 40 g oxygen $=\frac{40}{32}\times N_A$

Given: molecules in 40 g oxygen = molecules of $m$ g carbon dioxide

$\frac{m}{44}\times N_A=\frac{40}{32}\times N_A$

$\frac{m}{44}=\frac{40}{32}$

$m=55g$