Experiment For Hydrochloric Acid

For Hydrochloric Acid

HCl (aq) + H2O (l) ↔ Cl- (aq) + H3O+ (aq)

Net ionic: HCl (aq) ↔ Cl- (aq) + H+ (aq)

From the experimental data, the [H+] decreases as the concentration of the HCl in each solution decreases. Since acids dissociate in water, the dilution of the acid’s concentration (Macid) will determine the number of free hydrogen ions in the solution, being that they are equal to each other when the -log is used. By changing the concentration of the HCl, the acid strength decreases, as shown in the change in pH, due to the presence of H+ ions as they break away from the original molecules of the acid. These free ions are in the form of hydronium ions, which shows in the decrease of the H+ in the table above.

The data collected indicates

The observations that led to this pH value can be found in the table above. Once the colors were observed, the observations were compared to that of the previous salts in order to help determine the overall pH. The unknown salt had very similar colors to the ZnCl2 for each indicator, so the range of pH was based around the same values.

The hydrolysis of salts can be determined on the basis of the strength of the acid or base which forms it. If the salt is formed from a strong acid and a strong base, such as NaCl, the salt will form a neutral solution, since the anions of the acid and the cations of the base will not react with the water. A salt from a weak base and a strong acid, with NH4Cl as an example, will form an acidic solution. This is due to the cations from the base that increase the hydrogen ion concentration, by donating protons, which is known as a Bronsted acid. When concerning a salt formed by a weak acid and a strong base, such as Na C2H3O2, a basic solution will form. The anions of a weak acid in water will generate hydroxide ions, since the molecule will accept protons. It is termed as a Bronsted base. Though no examples were present, the salt that forms from a weak acid and a weak base can be determined by comparing the Ka (cation) and the Kb (anion) values. Most metallic ions, those found in groups 1A and 2A on the periodic table, such as Ca2+, a strong base, will have no reaction with water. However, all other metallic ions will undergo hydrolysis to form an acidic solution, such as KAl (SO4)2. As the Al is the molecule that was hydrolyzed, the spectator ions would not be present in the hydrolysis reaction, as is shown in the net ionic equations