Question

10mL of a solution of $NaOH$ is found to be completely neutralised by 8mL of a given solution of $HCl$. If we take 20mL of the same solution of $NaOH$, the amount $HCl$ solution (the same solution as before) required to neutralize it will be:
(A) 4mL
(B) 8mL
(C) 12mL
(D) 16mL

Answer 1

When a strong acid is neutralized by a strong base there are no excess hydrogen ions left in the solution. The solution is said to be neutral as it is neither acidic nor alkaline. The pH of such a solution is close to a value of 7.

Complete step by step solution:
A neutralization reaction can be defined as a chemical reaction in which an acid and base quantitatively react together to form salt and water as products.
In a neutralization reaction, there is a combination of ${{H}^{+}}$ ions and $O{{H}^{}}~$ ions which form water. A neutralisation reaction is generally an acid-base neutralization reaction.
The reaction of $NaOH$ and $HCl$ leads to the formation of $NaCl$ salt and Water. The reaction is as follows:
$HCl+NaOH\to NaCl+{{H}_{2}}O$
Here in the reaction, one molecule of $HCl$ reacts with one molecule of $NaOH$. But this happens when the molarity of both the acid and bases are the same. As per given in the question, 10mL of $NaOH$ is neutralized using 8 mL of $HCl$, so when 20mL of $NaOH$ is taken, so volume of base is doubled, so the volume of $HCl$ used will also be doubled for neutralization, therefore volume of $HCl$ needed will be 16 mL.

Hence the correct answer is the D option.

Note: The method of chemical titration is employed to find unknown concentrations of acids or bases by finding their neutralization point. To find the point where the neutralization happens, we use a pH indicator or pH meter.