Q78 / 180 · NEET 2026 (Cancelled) · Chemistry
The number of hydrogen atoms present in $5.4$ g of urea is :
(Given : Molar mass of urea : $60$ g mol$^{-1}$, $N_A : 6.022 \times 10^{23}$ particles mol$^{-1}$)
(Given : Molar mass of urea : $60$ g mol$^{-1}$, $N_A : 6.022 \times 10^{23}$ particles mol$^{-1}$)
- A$1.084 \times 10^{23}$
- B$1.084 \times 10^{22}$
- C$2.168 \times 10^{22}$
- Correct answerD$2.168 \times 10^{23}$
Solution
The chemical formula of urea is $NH_2CONH_2$.
Number of moles of urea $= \dfrac{5.4}{60} = 0.09$ mol.
One molecule of urea contains $4$ hydrogen atoms.
Number of moles of hydrogen atoms $= 4 \times 0.09 = 0.36$ mol.
Total number of hydrogen atoms $= 0.36 \times N_A = 0.36 \times 6.022 \times 10^{23} = 2.16792 \times 10^{23} \approx 2.168 \times 10^{23}$.
Answer: $2.168 \times 10^{23}$
Number of moles of urea $= \dfrac{5.4}{60} = 0.09$ mol.
One molecule of urea contains $4$ hydrogen atoms.
Number of moles of hydrogen atoms $= 4 \times 0.09 = 0.36$ mol.
Total number of hydrogen atoms $= 0.36 \times N_A = 0.36 \times 6.022 \times 10^{23} = 2.16792 \times 10^{23} \approx 2.168 \times 10^{23}$.
Answer: $2.168 \times 10^{23}$
Hence, the correct answer is option: 'D'.