Ncert Exercises & Solutions

The number of molecules of H₂SO₄ present in 100 mL of 0.02 M H₂SO₄ solution is:

1. $12.044 \times 10^{20}$ molecules

2. $6.022 \times 10^{23}$ molecules

3. $1 \times 10^{23}$ molecules

4. $12.044 \times 10^{23}$ molecules

Hint: Use the formula, Number of moles =

molarity \times volume in L

Explanation:

Step 1:

One mole of any substance contains

6.022 \times 10^{23}

atoms/molecules

Hence, Number of millimoles of

H_{2} {SO}_{4}

= molarity \times volume in L

= 0.02 \times 100 \times \frac{1 L}{1000}

= 2 \times 10^{- 3} mol

Step 2:

Number of molecules = number of molecules \times N

= 2 \times 10^{- 3} \times 6.022 \times 10^{23}

= 12.044 \times 10^{20} molecules