Question

Equal volume of 0.200 M $HCl$ and 0.400 M $KOH$ is mixed. The concentration of the principal ions in the resulting solution is:
A.$[{{K}^{+}}]=0.200M,[C{{l}^{-}}]=0.100M,[{{H}^{+}}]=0.200M$
B. $[{{K}^{+}}]=0.200M,[C{{l}^{-}}]=0.200M,[{{H}^{+}}]=0.100M$
C. $[{{K}^{+}}]=0.200M,[C{{l}^{-}}]=0.100M,[{{H}^{+}}]=0.100M$
D. $[{{K}^{+}}]=0.200M,[C{{l}^{-}}]=0.100M,[{{H}^{+}}]=0.200M$

Answer 1

Hint: In chemistry concentration can be defined as the abundance of a constituent divided by the total volume of mixture. There are many types of different concentrations there like molar concentration, mass concentration and volume concentration.

Complete step-by-step answer: Equal volume of 0.200 M $HCl$and 0.400 M $KOH$is mixed and the reaction between this can be shown as:
$KOH+HCl\to KCl+{{H}_{2}}O$
$\dfrac{0.4-0.2}{2}=0.1$ ${{K}^{+}}$and $C{{l}^{-}}$remain unchanged but due to dilution which is done in equal volumes molar concentration of each ion is halved which can be represented as $[C{{l}^{-}}]=0.100M$and $[{{K}^{+}}]=0.200M$. Now in the equation $KOH$is mixed which dissociates large number of $O{{H}^{-}}$ions and the solution become basic in nature which suggests that the concentration of $O{{H}^{-}}$ions is greater than concentration of ${{H}^{+}}$ion and the concentration of $O{{H}^{-}}$can be calculated by subtracting the concentration of base by the concentration of acid and divide them by 2 as shown follows:
$\dfrac{0.4-0.2}{2}=0.1$
Hence from the above discussion we can conclude that the concentration of the principal ions in the resulting solution is $[{{K}^{+}}]=0.200M,[C{{l}^{-}}]=0.100M,[{{H}^{+}}]=0.100M$

Hence option C is the correct answer.

Note:Concentration generally tells us about the acidity or basicity of solution. Where solution is made up of solute and solvent where solute is that which has to be dissolved and solvent in which solute is dissolved. Here concentration describes the amount of solute is solvent.