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NEET · Chemistry · STD 11 - 1. Some basic concept of 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 \(mol ^{-1}\) )

  1. A \(1.084 \times 10^{23}\)
  2. B \(1.084 \times 10^{22}\)
  3. C \(2.168 \times 10^{22}\)
  4. D \(2.168 \times 10^{23}\)
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Answer & Solution

Correct Answer

(D) \(2.168 \times 10^{23}\)

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Detailed explanation

(D) \(2.168 \times 10^{23}\)
The chemical formula of urea is \(NH _2 CONH _2\).
Number of moles of urea \(=\frac{5.4}{60}=0.09 mol\).
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 \(=0.36 \times N_A=0.36 \times 6.022 \times 10^{23}=2.16792 \times 10^{23} \approx 2.168 \times 10^{23}\).
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