Learning focus
Develop precise chemical language, connect equations and practical observations, interpret periodic trends and apply salt-preparation rules to unfamiliar examples.
Always-soluble groups
All sodium, potassium and ammonium salts are soluble. All nitrates are soluble. These rules are useful when selecting soluble reagents for precipitation.
Chlorides and sulfates
Most chlorides are soluble except silver chloride and lead(II) chloride. Most sulfates are soluble except barium sulfate, calcium sulfate and lead(II) sulfate. Questions may expect the named exceptions.
Carbonates and hydroxides
Most carbonates are insoluble except sodium, potassium and ammonium carbonates. Most hydroxides are insoluble except sodium, potassium and ammonium hydroxides; calcium hydroxide is partially soluble.
Using rules systematically
Separate a formula into cation and anion. Apply the strongest general rule first, especially sodium, potassium, ammonium and nitrate rules. Then check listed exceptions. A solubility decision should be explicit, not guessed from familiarity.
Practical or data skill
Classify a list of salts as soluble or insoluble and explain each decision using the rule and exception.
Examination tip
Memorise the exceptions exactly; calcium sulfate is listed as insoluble in the syllabus rule set.
Review questions and suggested answers
Question 1
Are all nitrates soluble?
Suggested answer
Yes.
Question 2
Name two insoluble chlorides.
Suggested answer
Silver chloride and lead(II) chloride.
Question 3
Which carbonates are soluble?
Suggested answer
Sodium, potassium and ammonium carbonates.
