Question

Which of the following solutions have the same concentration ?

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

(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

Answer 1

a & b

(a) $Molarity\left(M\right)=\frac{WeightofNaOH\times 1000}{MolecularweightogNaOH\times V\left(mL\right)}$

$=\frac{20\times 1000}{40\times 200}=2.5M$

(b) $M=\frac{0.5\times 1000}{2000}=2.5M$

(c) $M=\frac{40\times 1000}{10\times 100}=10M$

(d) $M=\frac{20\times 1000}{56\times 200}=1.785N$

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