Question

Solution A contains 20g of alkali in 250cm3 of water and solution B contains 10g of alkali in 500cm3 of water. Which one is more concentrated? Show your working.

Answer 1

Answer : The solution A is more concentrated than the solution B.

Explanation : Given,

Mass of alkali in solution A = 20 g

Mass of alkali in solution B = 10 g

Volume of solution in solution A = $250cm^3=250ml$

Volume of solution in solution B= $500cm^3=500ml$

First we have to calculate the concentration of both the solution A and B.

For solution A :

$\text{Concentration}=\frac{\text{Mass of alkali in solution A}\times 1000}{\text{Molar mass of alkali}\times \text{Volume of solution}}$

Let the molar mass of alkali be, 'M'.

$\text{Concentration}=\frac{20g\times 1000}{M\times 250ml}=\frac{80}{M}$

For solution B :

$\text{Concentration}=\frac{\text{Mass of alkali in solution B}\times 1000}{\text{Molar mass of alkali}\times \text{Volume of solution}}$

$\text{Concentration}=\frac{10g\times 1000}{M\times 500ml}=\frac{20}{M}$

From the above, we conclude that the value of solution A more than the solution B. So, the solution A more concentrated as compared to the solution B.

Hence, the solution A is more concentrated than the solution B.