Example of Chemical Neutralization

Chemical neutralization is the reaction between an acid and a base.

The degree of acidity or alkalinity is measured by the pH scale, which stands for hydrogen potential. Acids have a pH less than 7 and bases or alkalis have a pH greater than 7. The degree of pH 7 is the center of the scale, and corresponds to a chemically neutral mixture, that is, neither acid nor alkaline.

The result of the neutralization reaction is a salt and water.

Generally speaking, neutralization reactions are exothermic, that is, they give off heat.

The neutralization reaction will vary depending on whether the reacting acids and bases are strong or weak.

A strong acid with a strong base will react violently and give off a lot of heat. Both the acid and the base quickly change the pH of the mixture, so if some of the substances are passed a little, the solution will quickly be alkaline or acidic.

When a strong acid reacts with a weak base, then the pH change will not be so abrupt when adding the base, so with the same amount, the pH will slowly alkalize the mixture until neutralizing the acid.

The opposite happens with the combination of a weak acid with a strong base. In this case the acid will react slowly, acidifying the mixture until it reaches the point of neutralization.

If a weak acid reacts with a weak base, then both will react slowly until neutral. This reaction is the one that gives off the least amount of heat, but being slow, the heating can be more constant.

Knowing the amount of acid or base to be neutralized, we can calculate the amount of substance necessary to neutralize, from its molecular mass.

An example of chemical neutralization:

We have an acid solution with 10 grams of sulfuric acid. Calculate the necessary amount of potassium hydroxide to neutralize it and indicate the resulting products.

The reaction formula is:

H₂SW₄ + 2KOH -> K₂SW₄ + 2H₂OR
 Acid Hydroxide Sulfate Water
Potassium Sulfuric Potassium

So one mole of sulfuric acid is neutralized with two moles of potassium hydroxide.

We calculate the molecular mass of sulfuric acid:

Atomic mass of its components:

H = 1 Total = 2
S = 32 Total = 32
O = 16 Total = 64

Molecular mass of sulfuric acid: 98 g / mol.

Now we calculate the molecular mass of potassium hydroxide:

K = 39 Total = 39
H = 1 Total = 1
O = 16 Total = 16

Molecular mass of potassium hydroxide: 56 g / mol

Now, according to our formula, we have to neutralize one mole of sulfuric acid, we need two moles of potassium hydroxide, so we multiply the weight of potassium hydroxide by 2, which gives us 112 grams / mole. To calculate the amount of potassium hydroxide we need to neutralize the 10 grams of sulfuric acid, we apply the rule of 3:

10:98 = x: 112
112 X 10 = 1120/98 = 11.428 grams of potassium hydroxide are necessary to neutralize 10 grams of sulfuric acid.

We could also calculate it by dividing, to establish the relationship of substances:

98/10 = 9.8 which is the ratio of reactants
112/9.8 = 11.428

And as for the resulting substances, we will have:

Molecular mass of potassium sulfate:

K = 39 Total = 78
S = 32 Total = 32
O = 16. Total = 64

So the molecular mass of potassium sulfate is 174 g / mol.

And from the water

H = 1 Total = 2
O = 16 Total = 16

Molecular mass of water: 18 g / mol.

We then have that one molecule of potassium sulfate and two of water are produced.

We divide them by the ratio of reactants, and then we have:

135 / 9.8 = 13.775 g of potassium sulfate
36 / 9.8 = 3.673 grams of water.

And heat is given off.