Question

How many millilitres of $ 0.45{\text{M}} {\text{HCl}} $ will neutralize $ 25.0\;{\text{mL}} $ of $ 1.00{\text{M}} {\text{KOH}} $ ?

Answer 1

Hint: This problem can easily be solved with the help of basic stoichiometry and fundamentals of concentration of liquids. First, we will compare the reactant side with the products and then we will proceed after balancing the chemical equation. Then, we shall find the moles of KOH present and thus the volume of HCl required for that number of moles of hydrogen ions.

Formula used:
We would require the formula for molarity to solve this question
 $ {\text{molarity}} = \dfrac{{{n_s}}}{{{v_s}}} $
Where, $ {n_s} $ is the number of moles of solute
 $ {v_s} $ is the volume of solvent in litres.

Complete Step-by-Step solution
Let us first write the chemical equation for the reaction:
 $ {\text{HCl}}(aq) + {\text{KOH}}(aq) \to {\text{KCl}}(aq) + {{\text{H}}_2}{\text{O}}(l) $
According to the question, the volume of $ {\text{KOH = 25}} {\text{mL = 0}}{\text{.025}} {\text{L}} $
Let us now find the number of $ {\text{KOH}} $ present with the help of the above formula
 $ {\text{molarity}} = \dfrac{{{n_s}}}{{{v_s}}} $
On rearranging the formula, we get the number of moles
 $ {n_s} = {\text{molarity}} \times {v_s} $
Now, let us substitute the known values in the formula above to find the number of moles
 $ {n_s} = 1 M \times 0.025 L = 0.025 $ moles of $ {\text{KOH}} $
 Now, we will calculate the volume of the solution with the help of formula above
 $ {\text{molarity}} = \dfrac{{{n_s}}}{{{v_s}}} $
Rearranging the formula will give us the equation of volume
 $ {v_s} = \dfrac{{{n_s}}}{{{\text{molarity}}}} $
Now, let us put the known values in the formula
 $ {v_s} = \dfrac{{0.025{\text{ moles}}}}{{0.45 {\text{M}}}} = 0.056{\text{ L}} $
Now, we will convert litre into millilitres to get or required answer
Hence, the required volume is $ 0.056 {\text{L}} = 56{\text{ mL}} $ .

Additional information:
Molarity, which is referred to as molar, is represented by M. The molarity of a solution where one gram of solute is dissolved in a litre of solution is one molar. As we know, the solvent and solute blend is used in a solution to form a solution, so the total volume of the solution is taken.

Note:
A neutralization reaction can be defined as a chemical reaction in which an acid and a base react together quantitatively to form a product of salt and water.
There is a combination of $ {H^ + } $ ions and $ O{H^ - } $ ions which form water in a neutralization reaction. In general, a neutralisation reaction is an acid-base neutralization reaction.