Answer : The molarity of chloride anion in the solution is 0.05 mole/L
Explanation : Given,
Mass of
= 0.701 g
Volume of solution = 50 ml = 0.050 L
Molarity of AgCl = 55.0 mM = 0.055 M
Molar mass of
= 126.751 g/mole
First we have to calculate the moles of
.

Now we have to calculate the moles of
.

Now we have to calculate the limiting and excess reagent.
The balanced chemical reaction is,

From the balanced reaction we conclude that
As, 2 moles of
react with 1 mole of 
So, 0.00275 moles of
react with
moles of 
From this we conclude that,
is an excess reagent because the given moles are greater than the required moles and
is a limiting reagent and it limits the formation of product.
Now we have to calculate the moles of
.
As, 2 moles of
react to give 2 moles of 
So, 0.00275 moles of
react to give 0.00275 moles of 
Now we have to calculate the molarity of
.


As we know that, 1 mole of AgCl in solution gives 1 mole of silver ion and 1 mole of chloride ion.
So, the molarity of chloride ion = Molarity of AgCl = 0.05 mole/L
Therefore, the molarity of chloride anion in the solution is 0.05 mole/L