Question

When ${{\text{K}}_2}{\text{O}}$ is added to water, the solution becomes basic in nature because it contains a significant concentration of:
A.${{\text{K}}^ + }$
B.${{\text{O}}^{ - 2}}$
C.${\text{O}}{{\text{H}}^ - }$
D.${\text{O}}_2^{ - 2}$

Answer 1

A solution is basic when its hydroxide ion concentration is more than that of hydrogen ion concentration. A basic solution has more than 7 ${\text{pH}}$ or less than 7 ${\text{pOH}}$.

Complete step by step answer:
According to Arrhenius' concept; acids are those which give hydrogen ions and bases are those which give hydroxide ions in the aqueous solution. Bronsted lowry concept describes acid as proton or hydrogen ion donor and base as hydrogen ion or proton acceptor. Lewis concept describes acids as electron acceptors and bases as electron donors.
A basic solution have more number of hydroxide ion ${\text{O}}{{\text{H}}^ - }$ than hydrogen ion ${{\text{H}}^ + }$. But on the other hand, acidic solution have more concentration of hydrogen ion ${{\text{H}}^ + }$ than hydroxide ion ${\text{O}}{{\text{H}}^ - }$.
As when ${{\text{K}}_2}{\text{O}}$ is added to the water it will form the potassium hydroxide ${\text{KOH}}$ in the solution according to the reaction: ${{\text{K}}_2}{\text{O}} + {{\text{H}}_2}{\text{O}} \to 2{\text{KOH}}$. As ${\text{KOH}}$ being strong base, it will get completely dissociate into potassium ion ${{\text{K}}^ + }$ and hydroxide ion ${\text{O}}{{\text{H}}^ - }$ according to the reaction: ${\text{KOH}} \to {{\text{K}}^ + } + {\text{O}}{{\text{H}}^ - }$. Now due to increase in concentration of hydroxide ion ${\text{O}}{{\text{H}}^ - }$ in the solution, solution becomes basic and thereby ${\text{pH}}$ of solution will increase.
Hence, increase in ${\text{pH}}$ of the solution after addition of ${{\text{K}}_2}{\text{O}}$ is due to increased concentration of hydroxide ion ${\text{O}}{{\text{H}}^ - }$ in the solution.

Thus, the correct option is C.

Note:
For a solution, the sum of ${\text{pH}}$ and ${\text{pOH}}$ is equal to 14. A solution with equal concentration of hydrogen ion and hydroxide ion is said to be neutral and have a ${\text{pH}}$ of 7.