Question

• Recall that you have been contracted to determine how different salts affect the pH of bath water. At this point, you should have a procedure that allows you to determine how the pH is affected when different cations and/or anions are added to water. Describe how the company could use it to determine any salt's acid–base properties. Keep in mind that the company is confused by the terms "strong," "weak," "conjugate," and "dissociates" when describing acids and bases. Be sure to explain these terms to a lay- man, a person without strong chemistry knowledge. Textbook definitions will not be understood by your audience.

Answer 1

Step-by-step explanation:

A salt is a chemical compound that is formed when an acid combines with a base to form salt and water.

Therefore when salts are dissolved in bath water, they dissociate or are broken down into their constituent charged particles called IONS.

Ions can either be positively charged (cations) or negatively charged (anions).

We can measure the pH of the resulting bath water solution using an indicator which changes colour to denote whether it is acidic, basic or neutral

Lets take some examples.

Common salt (NaCl) when dissolved in water is broken down into the following

NaCl (s) → Na⁺ (aq) + Cl⁻ (aq)

The positively charged sodium ions are attracted to the negatively charged hydroxide ion (OH-) from bath water and form sodium hydroxide (NaOH) while the negatively charged chloride ion is attracted to the proton (H+) also from bath water to form hydrochloric acid.

When the pH of the resulting solution is taken using either a litmus paper or universal indicator, it is found to be neutral (no change in colour observed) suggesting that the resulting solution is neither acidic or basic.

This is so because both hydrochloric acid and sodium chloride which combine to form common salt are strong acids and strong bases.

A strong acid is one the bond between its positively charged ion (hydrogen ion) and the negatively charged ion is completely broken, thus completely releasing its protons (hydrogen ions) in aqueous solution. The more the concentration of this hydrogen ion in solution, the stronger the acid.

Acids have pH values less than 7, strong acids have pH values closer to 1 while weak acids have pH values closer to 7

A salt like baking soda - sodium bicarbonate (NaHCO₃) however will dissociate in bath water to give:

NaHCO3 → Na⁺(aq) + HCO₃⁻ (aq)

The conjugate base (HCO₃⁻) will be attracted to the proton from bath water to form H₂CO₃ which is unstable and further breaks down to give carbon dioxide and water.

The sodium cation however is attracted strongly to the hyroxide ion (OH-) from bath water to form sodium hydroxide which is a strong base.

When the pH of the resulting solution is taken using an indicator, it is found to be slightly above 7, indicating a slightly alkaline solution and confirming that sodium bicarbonate forms a weak base in solution.