As you know, sodium hydroxide and hydrochloric acid neutralize each other in a #1:1# mole ratio as described by the balanced chemical equation
This means that a complete neutralization, which would result in a neutral solution, i.e. a solution that has #"pH" = 7# at room temperature, requires equal numbers of moles of sodium hydroxide and hydrochloric acid. Notice that your two solutions have equal molarities, but that the volume of the hydrochloric acid solution is
times larger than the volume of the sodium hydroxide solution. This implies that the number of moles of hydrochloric acid is #4# times bigger than the number of moles of sodium hydroxide. This means that after the reaction is complete, you will be left with excess hydrochloric acid #-># the #"pH"# of the resulting solution will be #< 7#. Now, the number of moles of hydrochloric acid that will not take part in the reaction is given by
The total volume of the resulting solution will be
As you know, the #"pH"# of the solution is given by
Since hydrochloric acid is a strong acid that ionizes in a #1:1# mole ratio to produce hydronium cations, you can say that the concentration of hydronium cations in the resulting solution will be
This means that you have
The answer is rounded to three decimal places, the number of sig figs you have for your values.
Category: Chemical Engineering Math What is the pH of the resulting solution made by mixing 25 mL of 0.1 M HCl and 15 mL of 0.1 M NaOH? Solution: The given word problem is about the mixing of an acid and a base. If you mix an acid and a base, their products are salt and water. The chemical reaction for the given mixture is written as follows
In order to convert the HCl and NaOH completely into NaCl and water, you must have equal moles at each reactants which are HCl and NaOH. Let's see if the two reactants will be used completely as follows
Since the number of moles of HCl is greater than the number of moles of NaOH, then the resulting solution is an acid. Hence, the molarity of the resulting solution which is HCl is
Since HCl is a strong acid, then it is completely ionized as follows
Therefore, the pH of the resulting solution which is HCl solution is
|