Question

$ 20mL $ of $ 0.2M $ $ A{l_2}{(S{O_4})_3} $ is mixed with $ 20mL $ of $ 6.6M $ $ BaC{l_2} $ , the concentration of $ C{l^ - } $ ion in solution is?
(a) $ 0.2M $
(b) $ 6.6M $
(c) $ 0.02M $
(d) $ 0.06M $

Answer 1

Hint: Concentration is a term that states that the number of moles or ions present in the given volume of the solution or solvent. There are different concentration related terms like Molarity, Molality, percentage composition and many more.

Complete step-by-step answer:
First of all we have to complete the reaction,
So, the complete reaction is as follows:
 $ BaC{l_2} + A{l_2}{\left( {S{O_4}} \right)_3} \to BaS{O_4} + AlC{l_3} $
The reaction is not balanced, so, the complete balanced equation is as follows:
But before these, we must know the definition of balanced equation:
Balanced chemical equation: Balanced chemical equation is the equation in which the number of elements in the reactants side is equal to the product side.
 $ 3BaC{l_2} + A{l_2}{\left( {S{O_4}} \right)_3} \to 3BaS{O_4} + 2AlC{l_3} $
So, now the reaction is balanced.
Now, we will write the given data in the question:
Moles of $ A{l_2}{(S{O_4})_3} = 0.2M $
Volumes of $ A{l_2}{(S{O_4})_3} = 20mL $
Moles of $ BaC{l_2} = 6.6M $
Volumes of $ BaC{l_2} = 20mL $
As $ BaS{O_4} $ is a precipitated, so, no moles of $ BaS{O_4} $ is present in the solution and as $ AlC{l_3} $ is an ionic compound, and hence, ions of chlorine and aluminium are present in the solution.
From the concepts of ionic equilibrium, when there is presence of some precipitated solids as they are insoluble, they do not make ions and so their concentration is not considered.
So, the concentration of the chlorine will be the same as the concentration is before because the electrolyte is a strong electrolyte.
Hence, when $ 20mL $ of $ 0.2M $ $ A{l_2}{(S{O_4})_3} $ is mixed with $ 20mL $ of $ 6.6M $ $ BaC{l_2} $ , the concentration of $ C{l^ - } $ ion in solution is $ 6.6M $ .
Hence, the correct option is (b) $ 6.6M $ .

Note:
The equilibrium in which the ions of ionic compounds are dissociated into polar solvents and the un-dissociated ionic compound and the dissociated ions are always in equilibrium with each other. This type of equilibrium is called ionic equilibrium.