Question

A student wants to make 135 mL of 8.5 M $KBr$ by diluting a 6.0 M $KBr$ solution. How much of that solution should be used?

Answer 1

Hint: Solution is composed of two components known by the name solute and solvent where solute is the component in which gets dissolved and present in lower concentration while solvent is the substance in which solute is dissolved and present in higher amounts.

Complete answer: Here the amount of $KBr$ is given in molar concentration or we can define it as molarity which can be defined as the number of moles of solute dissolved per liter of the solution. This can be represented by the formula:
$M=\dfrac{n}{V}$; Where M = Molarity, n = number of moles of solute and V = Volume in liters.
Now by applying the equation as given below we can find out the volume of solution used:
$\dfrac{6.0\times 0.135}{8.5}={{V}_{1}}$, Here ${{M}_{1}}$= 8.5 M, ${{V}_{1}}$ is to be calculated, ${{M}_{2}}$= 6.0 M and the value of ${{V}_{2}}$= 135 mL but we need the volume in liters, therefore ${{V}_{2}}$= 0.135 L Now put the given values in the equation
$8.5\times {{V}_{1}}=6.0\times 0.135$
$\dfrac{6.0\times 0.135}{8.5}={{V}_{1}}$
${{V}_{1}}$= 0.095 L or we can say 95 mL
Hence if a student wants to make 135 mL of 8.5 M $KBr$ by diluting a 6.0 M $KBr$ solution then 0.095 L of that solution should be used.

Note: $KBr$ is a salt known by the name potassium bromide which is generally used as an anticonvulsant i.e. antiseizure drugs and also as tranquilizers. It is white crystalline powder like substance which can easily dissolve in water.