Ncert Exercises & Solutions

Which of the following solutions have the same concentration?

(a) 20 g of NaOH in 200 mL of solution

(b) 0.5 mol of KCl in 200 mL of solution

(c) 40 g of NaOH in 100 mL of solution

(d) 20 g of KOH in 200 mL of solution

Options:

1. (a) and (b)

2. (a) and (c)

3. (a) and (d)

4. (b) and (c)

Hint: Calculate the molarity of each solution.

(a, b)

(a)

Molarity (M) = \frac{weight of NaOH \times 1000}{Molecular weight of NaOH \times V (mL)} = \frac{20 \times 1000}{40 \times 200} = 2.5 M

(b)

M = \frac{0.5 \times 1000}{200} = 2.5 M

(c)

M = \frac{40 \times 1000}{10 \times 100} = 10 M

(d)

M = \frac{20 \times 1000}{56 \times 200} = 1.785 M

Thus, 20 g NaOH in 200 mL of solution and 0.5 mol of KCl in 200 mL have the same concentration.