18.4 Soluble and Insoluble Salts Several factors effect the solubility of a salt including the nature of salt and the temperature. Soluble salts include all sodium, potassium, and ammonium salts. Similarly all metallic nitrates are soluble in water and the same is true for most chlorides and sulfates. In contrast all carbonates with the exception of carbonates of sodium, potassium and ammonium are insoluble in water. Similarly, chlorides of silver and lead and sulfates of barium and lead are also insoluble in water. Hydroxides of sodium, potassium and ammonium are soluble while calcium hydroxide is only partially soluble in water. All other hydroxides are insoluble in water.
The following table shows the pattern for the solubility of salts in water.
| Salts | Soluble | Insoluble |
|---|---|---|
| Salts of sodium, potassium and ammonium and all nitrates | All | None |
| Chlorides, bromides and iodides | Most soluble | Silver, Lead (II) |
| Sulphates | Most soluble | Barium, Lead (II), Calcium |
| Carbonates | Sodium, Potassium, Ammonium | Most insoluble |
| Hydroxides | Sodium, Potassium, Ammonium, Calcium (partially soluble) | Most insoluble |
📌 key notes from text: All Na⁺, K⁺, NH₄⁺ salts & all nitrates are soluble. Most chlorides soluble – exceptions AgCl, PbCl₂. Most sulphates soluble – exceptions BaSO₄, PbSO₄, CaSO₄. Carbonates: only Na, K, NH₄ carbonates soluble, rest insoluble. Hydroxides: Na, K, NH₄ soluble; Ca(OH)₂ partially soluble; all other hydroxides insoluble.
🧠 memory tips & tricks
🔹 NAK (SNAK) — Sodium, potassium, ammonium (and Nitrate) are Always Soluble.
🔹 Chloride exceptions: SPilver and Lead (AgCl, PbCl₂) – “Silver & Lead Chloride? No thanks!”
🔹 Sulphate exceptions: BBC (Barium, Lead, Calcium) – “Big Bad Calcium (sulphate) sinks”.
🔹 Carbonates: only NaK (sodium, potassium) and ammonium carbonates dissolve; rest = solid sink.
🔹 Hydroxides: soluble: NaK + NH₄; partially Ca; all others insoluble.
📅 lesson planner
⬇️ click an answer: true turns green, others red.
📚 student guidelines: Study the solubility table 18.1. Note the always-soluble ions: Na⁺, K⁺, NH₄⁺, NO₃⁻. Memorise exceptions using acronyms. Use the 10 MCQ quiz to test yourself – immediate feedback shows green (true) and red (false). Adjust font size, switch day/night. Plan your revision with the lesson planner.