Question

In water, or aqueous solution of $HCl$ or ${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$ , proton exists as:
A. ${{\text{H}}_3}{{\text{O}}^{\text{ + }}}$
B. ${\text{H(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_4}^{\text{ + }}$
C. ${\text{H(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_n}^{\text{ + }}$
D. All correct

Answer 1

Hint: We must have to need to remember that the protons that usually exist in solutions are ${H^+}$, ${{\text{H}}_3}{{\text{O}}^{\text{+}}}$, ${\text{H(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_2}^{\text{+}}$ and ${\text{H(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_3}^{\text{ + }}$ . Mostly the ${H^ + }$ proton is present in the acids which are of good strength but as the quantity of water keep on increasing the amount of ${H^ + }$ ion keeps on decreasing and the concentration of ${H_3}{O^ + }$ ions increases.

Complete step by step answer:
Let’s start with discussing the types of protons that can exist. As we know that the protons that usually exist in solutions are ${H^+}$ , ${{\text{H}}_3}{{\text{O}}^{\text{+}}}$ , ${\text{H(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_2}^{\text{+}}$ and ${\text{H(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_3}^{\text{ + }}$ . We have to remember that mostly the ${H^ + }$ proton is present in the acids which are of good strength but as the quantity of water keep on increasing whereas the amount of ${H^ + }$ ion keeps on decreasing and the concentration of ${H_3}{O^ + }$ ions increases.
We must have to remember that in water, or aqueous solution of $HCl$ or ${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$ , proton exists not as ${H^ + }$ ion but one which is solvated with one, two or three molecules of water. In the options given to us the possible answers are ${{\text{H}}_3}{{\text{O}}^{\text{ + }}}$ , ${\text{H(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_4}^{\text{ + }}$and ${\text{H(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_n}^{\text{ + }}$.

So, the correct answer is Option D.

Note: When we keep on adding water to the acid or base, water being neutral in nature when added reduces the concentration of ions in the acid or base. Which means that the strength of the acid decreases as we keep on adding water, also the pH of the acid starts moving towards $7$ . We have to remember that pH means potential of hydrogen which is a scale used to specify the acidic or basic nature of an aqueous solution. The range of pH values goes on from 0-14.