Which of the following salts will give highest pH in water ?

Question

At \(25^\circ \text{C}\), the ionic product of water is \(10^{-14}\). The free energy change (\(\Delta G^\circ\)) for the self-ionization of water in kcal mol\(^{-1}\) is:

Answer 1

To determine which salt will produce the highest pH when dissolved in water, we need to analyze the nature of the ions that make up these salts. The pH of a solution largely depends on the resultant cations and anions after the dissolution of the salt, whether they undergo any hydrolysis, and how they affect the solution's acidity or basicity.

NaCl (Sodium Chloride): When dissolved in water, it dissociates into Na⁺ and Cl^-. Both of these ions are neutral and do not undergo hydrolysis. Hence, the solution remains neutral with a pH near 7.
KCl (Potassium Chloride): Similar to NaCl, KCl dissociates into K⁺ and Cl^-. Both ions do not alter the pH significantly as they are neutral in water. The solution remains close to a neutral pH of 7.
CuSO₄ (Copper(II) Sulfate): This salt dissociates into Cu²⁺ and SO₄^2-. Copper ions (Cu²⁺) can undergo hydrolysis in water, which slightly increases the acidity (lowering the pH) by forming Cu(OH)₂ and releasing H⁺ ions. Hence, CuSO₄ results in an acidic solution.
Na₂CO₃ (Sodium Carbonate): This salt dissociates into 2 Na⁺ and CO₃^2-. The carbonate ion (CO₃^2-) is a weak base and undergoes hydrolysis to form OH^- ions, thus increasing the pH of the solution. Na₂CO₃ forms a basic solution.

Among the given salts, Na₂CO₃ is the one that dissolves in water to form a basic solution. Therefore, it will result in the highest pH compared to the other options.

The correct answer is Na₂CO₃, as it increases the pH significantly due to the basic nature of the carbonate ions.

Answer 2

To determine which salt will produce the highest pH when dissolved in water, we need to analyze the nature of the ions that make up these salts. The pH of a solution largely depends on the resultant cations and anions after the dissolution of the salt, whether they undergo any hydrolysis, and how they affect the solution's acidity or basicity.

NaCl (Sodium Chloride): When dissolved in water, it dissociates into Na⁺ and Cl^-. Both of these ions are neutral and do not undergo hydrolysis. Hence, the solution remains neutral with a pH near 7.
KCl (Potassium Chloride): Similar to NaCl, KCl dissociates into K⁺ and Cl^-. Both ions do not alter the pH significantly as they are neutral in water. The solution remains close to a neutral pH of 7.
CuSO₄ (Copper(II) Sulfate): This salt dissociates into Cu²⁺ and SO₄^2-. Copper ions (Cu²⁺) can undergo hydrolysis in water, which slightly increases the acidity (lowering the pH) by forming Cu(OH)₂ and releasing H⁺ ions. Hence, CuSO₄ results in an acidic solution.
Na₂CO₃ (Sodium Carbonate): This salt dissociates into 2 Na⁺ and CO₃^2-. The carbonate ion (CO₃^2-) is a weak base and undergoes hydrolysis to form OH^- ions, thus increasing the pH of the solution. Na₂CO₃ forms a basic solution.

Among the given salts, Na₂CO₃ is the one that dissolves in water to form a basic solution. Therefore, it will result in the highest pH compared to the other options.

The correct answer is Na₂CO₃, as it increases the pH significantly due to the basic nature of the carbonate ions.

Which of the following salts will give highest pH in water ?

The Correct Option is B

Solution and Explanation

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