Question

Which of the following samples contains the largest number of atoms?

• A. $1 g$ of $CO _{2}$
• B. $1 g$ of $C _{8} H _{8}$
• C. $1 g$ of $C _{2} H _{6}( g )$
• D. $1 g$ of $LiF (s)$

Answer 1

Answer: (C)

(c) Molar mass of $CO _{2}=44 \,g \,mol ^{-1}$

$44 \, g \, CO _{2}=3 \times 6.02 \times 10^{23}$ atoms

$\therefore 1 \, g$ of $CO _{2}=0.41 \times 10^{23}$ atoms

(b) Molecular mass of $C _{8} H _{8}=104 \,g \,mol ^{-1}$

$1 g$ of $C _{8} H _{8}=\frac{16 \times 6.02 \times 10^{23}}{104}$ atoms $=0.93 \times 10^{23}$ atoms

(c) molar mass of $C _{2} H _{6}=30\, g \, mol ^{-1}$

$1 g$ of $C _{2} H _{6}=\frac{8 \times 6.02 \times 10^{23}}{30}$ atoms

$=1.63 \times 10^{23}$ atoms

(d) molar mass of $L i F=7+19=26$

$1 g$ of $LiF =\frac{2 \times 6.02 \times 10^{23}}{26}$ atoms

$=0.46 \times 10^{23}$ atoms