Saline Hydrolysis: Finding The Neutral Salt

by ADMIN 44 views

Hey guys! Ever wondered why some salts make water acidic or basic when you dissolve them? It's all thanks to a process called saline hydrolysis. But don't worry, we're going to break it down and make it super easy to understand. We'll also figure out which salt keeps things nice and neutral, with a pH of 7, just like pure water. Let's dive in!

Understanding Saline Hydrolysis

Saline hydrolysis, at its core, is the reaction of a salt with water, which leads to the formation of an acidic or basic solution. Not all salts undergo hydrolysis; it depends on the nature of the ions that make up the salt. To understand this, we need to consider the acids and bases that form these salts. Salts are formed from the reaction between an acid and a base (neutralization reaction). If the acid and base are both strong, the resulting salt will not undergo hydrolysis and will form a neutral solution. However, if one of the acid or base is weak, the salt will undergo hydrolysis, leading to a change in the pH of the solution.

For example, if a salt is formed from a strong acid and a weak base, the cation (positive ion) of the salt will react with water to produce hydronium ions (H3O+), making the solution acidic. Conversely, if a salt is formed from a weak acid and a strong base, the anion (negative ion) of the salt will react with water to produce hydroxide ions (OH-), making the solution basic. The extent of hydrolysis depends on the strength of the weak acid or base involved. Stronger the weak acid or base, lesser will be the degree of hydrolysis and vice versa.

Now, consider a salt formed from a weak acid and a weak base. In this case, both the cation and anion will undergo hydrolysis. The pH of the solution will depend on the relative strengths of the weak acid and weak base. If the weak acid is stronger than the weak base, the solution will be acidic. If the weak base is stronger than the weak acid, the solution will be basic. If both are of equal strength, the solution will be approximately neutral. Understanding these principles is key to predicting whether a salt solution will be acidic, basic, or neutral.

Identifying Neutral Salts

So, how do we pinpoint a salt that dissolves in water to give us a perfectly neutral solution, with a pH of 7? The key is to look for salts formed from the reaction of a strong acid and a strong base. These salts don't undergo hydrolysis because their ions don't react appreciably with water. This is because the conjugate acids and bases of strong acids and bases are very weak and have negligible tendencies to accept or donate protons. Consequently, the concentration of hydronium ions (H3O+) remains equal to the concentration of hydroxide ions (OH-), maintaining the neutrality of the solution. Let's examine some common strong acids and strong bases to help illustrate this concept.

Examples of strong acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), hydrobromic acid (HBr), hydroiodic acid (HI), and perchloric acid (HClO4). Strong bases typically consist of Group 1 and Group 2 hydroxides, such as sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), and barium hydroxide (Ba(OH)2). When a strong acid reacts with a strong base, the resulting salt contains ions that have no significant tendency to hydrolyze. Therefore, the pH of the solution remains neutral at 7. Identifying these salts requires recognizing their constituent strong acids and strong bases.

Let's consider sodium chloride (NaCl) as an example. Sodium chloride is formed from the reaction of hydrochloric acid (HCl), a strong acid, and sodium hydroxide (NaOH), a strong base. When sodium chloride is dissolved in water, neither the sodium ions (Na+) nor the chloride ions (Cl-) react significantly with water. As a result, the solution remains neutral, with a pH of 7. Recognizing these patterns allows us to predict the neutrality of salt solutions effectively.

Evaluating the Options

Let's analyze the given options to determine which salt produces a neutral solution when dissolved in water:

a) Cloreto de sódio (NaCl): As we discussed earlier, sodium chloride (NaCl) is formed from hydrochloric acid (HCl), a strong acid, and sodium hydroxide (NaOH), a strong base. Therefore, it does not undergo hydrolysis and produces a neutral solution.

b) Acetato de sódio (CH3COONa): Sodium acetate (CH3COONa) is formed from acetic acid (CH3COOH), a weak acid, and sodium hydroxide (NaOH), a strong base. The acetate ion (CH3COO-) will react with water to produce hydroxide ions (OH-), making the solution basic. Therefore, it will not produce a neutral solution.

c) Nitrato de potássio (KNO3): Potassium nitrate (KNO3) is formed from nitric acid (HNO3), a strong acid, and potassium hydroxide (KOH), a strong base. Similar to sodium chloride, it does not undergo hydrolysis and produces a neutral solution.

The Correct Answer

Based on our analysis, both sodium chloride (NaCl) and potassium nitrate (KNO3) are formed from strong acids and strong bases. Therefore, they do not undergo hydrolysis and produce neutral solutions when dissolved in water. However, since the question asks for only one alternative, and option A (NaCl) was presented first, it is a reasonable choice assuming the context implies selecting the first correct answer encountered.

So, the correct answer is:

a) Cloreto de sódio (NaCl)

Key Takeaways

  • Salts from strong acids and strong bases produce neutral solutions.
  • Salts from strong acids and weak bases produce acidic solutions.
  • Salts from weak acids and strong bases produce basic solutions.

Understanding saline hydrolysis helps us predict the pH of salt solutions, which is crucial in various chemical and biological applications. Keep these principles in mind, and you'll be a pro at determining whether a salt solution is acidic, basic, or neutral! Keep rocking guys!