Question

what is the molarity of 20.0 ml of a KCl solution that reacts completely with 30.0 ml of a 0.400 M Pb(NO3)2 solution?

Answer 1

The molarity of KCl solution is 1.2 M

Explanation:

To calculate the molarity of solution, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (in mL)}}$       .......(1)

Molarity of lead nitrate solution = 0.400 M

Volume of solution = 30.0 mL

Putting values in equation 1, we get:

$0.400M=\frac{\text{Moles of lead nitrate}\times 1000}{30.0}\\\\\text{Moles of lead nitrate}=\frac{0.400\times 30.0}{1000}=0.012moles$

The chemical equation for the reaction of lead nitrate and potassium chloride follows:

$Pb(NO_3)_2+2KCl\rightarrow PbCl_2+2KNO_3$

By Stoichiometry of the reaction:

1 mole of lead nitrate reacts with 2 moles of KCl

So, 0.012 moles of lead nitrate will react with = $\frac{2}{1}\times 0.012=0.024mol$ of KCl

Now, calculating the molarity of KCl by uisng equation 1, we get:

Moles of KCl = 0.024 moles

Volume of solution = 20.0 mL

Putting values in equation 1, we get:

$\text{Molarity of KCl}=\frac{0.024\times 1000}{20}=1.2M$

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