Question

How do I calculate the molarity of a solution prepared by diluting $87.44mL$ of $0.743M$ potassium chloride to $150.00mL$ ?

Answer 1

‌There are various measures which can be used to determine the concentration of a solution, one of them is molarity, which is the number of moles of solute present per litre of the solution. When two different solutions have same number of moles of solute, we can use the equation ${{C}_{1}}{{V}_{1}}={{C}_{2}}{{V}_{2}}$ to find out the volume or concentration of the solution if three of the values of quantities are given to us.

Complete step by step answer:
Molarity of a solution can be defined as the number of moles of solute present per litre of the solution. It is a measure of concentration of a solution and has a unit $mol{{L}^{-1}}$ or $M$.
In order to find out the molarity of the substance, at first we need to write the known values of all the quantities which are provided to us, to get an idea about the approach of the answer.
Initially it was given that the concentration of the potassium chloride is $0.743M$, and we will denote it by using ${{C}_{1}}$ and the volume of the same solution is given as $87.44mL$, and we would denote it by ${{V}_{1}}$.
It is given that the volume of the compound or solution whose concentration is to be determined, is $150.00mL$, and we will denote this volume as ${{V}_{2}}$. And the unknown concentration of the solution would become ${{C}_{2}}$.
Now, we know that if two solutions have the same amount of moles of solute, they can be equated in terms of concentration and volume. It can be expressed by the equation,
${{C}_{1}}{{V}_{1}}={{C}_{2}}{{V}_{2}}$
Where all the symbols denote the same quantities as discussed earlier.
After rearranging this equation by writing all the known values at one side, we will get,
${{C}_{2}}=\dfrac{{{C}_{1}}{{V}_{1}}}{{{V}_{2}}}$
Now, we will put all the values of the quantities which are provided to us in this equation, we get,
${{C}_{1}}=\dfrac{0.743mol{{L}^{-1}}\times 87.44mL}{150.00mL}$
After solving this equation we get, $0.43M$ is the concentration of the solution.

Note: Molarity is a measure of concentration in terms of number of moles of solute and the volume of solution. It is not temperature independent, meaning it can change with change in temperature, as we take into account the volume of the solution, and volume changes with change in temperature.