Which one of the following salts solution in water has the highest value of pH?

CONCEPT:

pH of a solution

• The pH of a solution is a measure of its acidity or basicity. It is calculated as:

  pH = -log[H⁺]

• Salts in water can undergo hydrolysis, affecting the pH of the solution:
  • Neutral salts like NaCl and KNO₃ do not hydrolyze and produce solutions with a neutral pH of 7.
  • Basic salts like Na₂CO₃ hydrolyze to form OH^-, increasing the pH above 7.
  • Acidic salts like ZnCl₂ hydrolyze to form H⁺, lowering the pH below 7.

EXPLANATION:

• Examining the given salts:
  • NaCl: Sodium chloride is a neutral salt formed from a strong acid (HCl) and a strong base (NaOH). It does not hydrolyze in water, resulting in a neutral pH of 7.
  • KNO₃: Potassium nitrate is also a neutral salt formed from a strong acid (HNO₃) and a strong base (KOH). Its solution has a pH of 7.
  • Na₂CO₃: Sodium carbonate is a basic salt formed from a weak acid (H₂CO₃) and a strong base (NaOH). Its solution has a pH greater than 7 due to hydrolysis producing OH^-.
  • ZnCl₂: Zinc chloride is an acidic salt formed from a strong acid (HCl) and a weak base (Zn(OH)₂). Its solution has a pH less than 7 due to hydrolysis producing H⁺.

Therefore, the correct answer is Na₂CO₃.