Step 1: Understanding the Question:
We need to calculate the total number of hydrogen atoms in a given mass of urea. Step 2: Key Formula or Approach:
1. Find the molecular formula of urea.
2. Calculate the molar mass.
3. Find moles of urea.
4. Use Avogadro's number ($N_A = 6.022 \times 10^{23}$) and atomicity to find the number of atoms. Step 3: Detailed Explanation:
1. Molecular formula of urea: $NH_2CONH_2$.
2. Molar mass = $(14 \times 2) + (1 \times 4) + 12 + 16 = 28 + 4 + 12 + 16 = 60\text{ g/mol}$.
3. Moles of urea = $\frac{\text{Given mass}}{\text{Molar mass}} = \frac{5.4}{60} = 0.09\text{ moles}$.
4. One molecule of urea contains 4 hydrogen atoms.
5. Total number of $H$ atoms = Moles $\times N_A \times \text{Atomicity of } H$:
\[ \text{H atoms} = 0.09 \times 6.022 \times 10^{23} \times 4 \]
\[ \text{H atoms} = 0.36 \times 6.022 \times 10^{23} \]
\[ \text{H atoms} \approx 2.16792 \times 10^{23} \approx 2.168 \times 10^{23} \] Step 4: Final Answer:
The number of hydrogen atoms is $2.168 \times 10^{23}$.