Determine whether aqueous solutions of the following salts are acidic, basic, or neutral:
(a) K2CO3
(b) CaCl2
(c) KH2PO4
(d) (NH4)2CO3
Can you show work that was used to find out of the compound was acidic, basic, neutral.
The Correct Answer and Explanation is :
To determine whether aqueous solutions of the given salts are acidic, basic, or neutral, we analyze the ions produced upon dissociation and their interactions with water. The key concept is that salts derived from strong acids and strong bases form neutral solutions, while those derived from weak acids and/or weak bases can form acidic or basic solutions.
Analysis of Each Salt
(a) K₂CO₃ (Potassium Carbonate) – Basic
- Dissociation:
[
K_2CO_3 \rightarrow 2K^+ + CO_3^{2-}
] - K⁺ comes from KOH (a strong base) – does not hydrolyze.
- CO₃²⁻ comes from H₂CO₃ (a weak acid) – hydrolyzes in water:
[
CO_3^{2-} + H_2O \rightleftharpoons HCO_3^- + OH^-
] - Produces OH⁻ (hydroxide ions), making the solution basic.
(b) CaCl₂ (Calcium Chloride) – Neutral
- Dissociation:
[
CaCl_2 \rightarrow Ca^{2+} + 2Cl^-
] - Ca²⁺ (from strong base Ca(OH)₂) and Cl⁻ (from strong acid HCl) do not hydrolyze.
- Since neither ion affects pH, the solution is neutral.
(c) KH₂PO₄ (Potassium Dihydrogen Phosphate) – Acidic
- Dissociation:
[
KH_2PO_4 \rightarrow K^+ + H_2PO_4^-
] - H₂PO₄⁻ is the conjugate base of H₃PO₄ (a weak acid) and can donate a proton:
[
H_2PO_4^- \rightleftharpoons HPO_4^{2-} + H^+
] - Releases H⁺ (protons), making the solution acidic.
(d) (NH₄)₂CO₃ (Ammonium Carbonate) – Basic
- Dissociation:
[
(NH_4)_2CO_3 \rightarrow 2NH_4^+ + CO_3^{2-}
] - NH₄⁺ (from NH₃, a weak base) hydrolyzes to release H⁺:
[
NH_4^+ + H_2O \rightleftharpoons NH_3 + H_3O^+
] - CO₃²⁻ hydrolyzes to produce OH⁻.
- Since CO₃²⁻ has a stronger basic effect than NH₄⁺’s acidic effect, the solution is basic.
Final Answers:
(a) Basic
(b) Neutral
(c) Acidic
(d) Basic
Image Representation
I will now generate an image illustrating the dissociation of these salts and the hydrolysis reactions involved.
Here is a scientific illustration depicting the dissociation of the given salts in aqueous solutions, showing their pH effects with appropriate indicator colors. Let me know if you need any modifications or further explanations!