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An **acid-base reaction** is a chemical reaction that occurs between an acid and a base. The result of this reaction is often the formation of water and a salt. An acid donates a proton (H鈦�) in the reaction, while a base accepts the proton. These reactions are important in many biological processes and industrial applications. For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), they produce water (H鈧侽) and sodium chloride (NaCl) 鈥� a neutral salt.

Types of acid-base reactions include:

• Neutralization: Acid + Base 鈫� Salt + Water
• Acid with a carbonate: Acid + Carbonate 鈫� Salt + Water + CO鈧�

Understanding these reactions helps explain why certain salts result in acidic or alkaline solutions in water.

The **pH level** measures how acidic or basic (alkaline) a solution is, ranging from 0 to 14. A pH of 7 is neutral, meaning the concentration of hydrogen ions (H鈦�) equals the concentration of hydroxide ions (OH鈦�).

A solution with a pH less than 7 is acidic:

• Examples include lemon juice and vinegar.
• They have a higher concentration of H鈦� ions.

A solution with a pH greater than 7 is basic or alkaline:

• Examples include baking soda and detergents.
• They have a higher concentration of OH鈦� ions.

In the given exercise, an alkaline solution has a pH greater than 7, indicating it has more OH鈦� ions than H鈦� ions. This helps to determine that the salt causing the solution to be alkaline must come from a weak acid and a strong base.

Hydrolysis is a process where a salt reacts with water to form an acidic or basic solution. The type of solution formed depends on the strengths of the acid and base that created the salt. When a salt dissolves in water, it can either donate H鈦� or OH鈦� ions, influencing the pH.

**Non-reactive salts** from strong acids and bases don鈥檛 affect the pH, resulting in a neutral solution.

Salts from:

• Strong acid and weak base release H鈦� ions, making the solution acidic.
• Weak acid and strong base release OH鈦� ions, making the solution basic or alkaline.

This helps to determine in the exercise why the salt from a weak acid and strong base makes the solution alkaline. The weak acid's conjugate base interacts with water to produce OH鈦� ions.

An acid or base鈥檚 strength is determined by how completely it ionizes in water:

**Strong acids** completely dissociate in water, releasing all their H鈦� ions. Examples include HCl and H鈧係O鈧�.

**Weak acids** only partially dissociate, leaving some of the acid intact. Examples include acetic acid (CH鈧僀OOH) and citric acid.

**Strong bases** fully dissociate to release OH鈦� ions. Examples are NaOH and KOH.

**Weak bases** only partially produce OH鈦� ions in water, such as ammonia (NH鈧�).

In the exercise, the salt was formed from a weak acid and a strong base, resulting in an alkaline solution. This is because the weak acid鈥檚 conjugate base is strong enough to react with water, producing additional OH鈦� ions and raising the pH above 7.