Question

Calculate number of molecules present in 5.4 g of urea (Molar mass of urea $=60~g~mol^{-1}$)

• A. $6.022\times10^{22}$
• B. $5.419\times10^{22}$
• C. $4.312\times10^{22}$
• D. $9.933\times10^{22}$

Hint:

Always convert mass to moles first using the given molar mass.

Answer 1

The Correct Option is B

Step 1: Concept
Number of molecules is calculated by finding moles and multiplying by Avogadro's number ($N_A = 6.022 \times 10^{23}$).

Step 2: Formula
$Moles = \frac{Mass}{Molar~Mass}$

Step 3: Analysis
- $Moles = \frac{5.4}{60} = 0.09~mol$
- $Molecules = 0.09 \times 6.022 \times 10^{23}$

Step 4: Conclusion
$Molecules = 5.4198 \times 10^{22}$. Hence, correct answer is (B). Final Answer: (B)