Q. How many H-atoms are present in 0.046 g of ethanol?
A) $6 \times 10^{20}$
B) $1.2 \times 10^{21}$
C) $3 \times 10^{21}$
D) $3.6 \times 10^{21}$
Explanation
(d)
Mol. wt. of $C_{2}H_{5}OH$
$= 12 \times 2 + 1 \times 5 + 16 + 1 = 46$ g
$\because$ 46 g of $C_{2}H_{5}OH$ has hydrogen atoms
$= 6 \times$ Avogadro number
$\therefore$ 0.046 g of $C_{2}H_{5}OH$ has hydrogen atoms
$= \frac{6 \times 6.023 \times 10^{23} \times 0.046}{46}$
$= 3.6 \times 10^{21}$ atoms of hydrogen.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.