Question

The largest number of molecules is in

• A. 34 g of $H_2O$
• B. 28 g of $CO_2$
• C. 46 g of ethyl alcohol
• D. 54 g of nitrogen pentaoxide $(N_2O_ 5)$

Answer 1

Answer: (A)

34 g of $H_2O$

Answer 2

34 g of $H_2O$
$\because$ 18 g of $H_2O = 6 \times 10^{23}$ molecules
$\therefore$ 34 g of $H_2O = \frac{6 \times 10^{23} \times 34}{18}$
= $11.33 \times 10^{23}$ molecules
(b) 28 g of $CO_2$
$\because$ 44 g of $CO_2 = 6 \times 10^{23}$
$\therefore$ 28 g of $CO_2 = \frac{6 \times 10^{23} \times 28}{44}$
= $3.8 \times 10^{23}$ molecules
(c) 46 g of $CH_3OH$
$\because$ 32 g of $CH_3OH = 6 \times 10^{23}$ molecules
$\therefore$ 46 g of $CH_3OH = \frac{6 \times 10^{23} \times 46}{32}$
= $8.625 \times 10^{23}$ molecules
(d) 54 g of $N _2O_5$
$\because$ 108 g of $N _2O_5 = 6 \times 10^{23}$ molecules
$\therefore$ 54 g of $N _2O_5 = \frac{6 \times 10^{23} \times 54}{108}$
= $3 \times 10^{23}$ molecules