Learning focus
Develop precise chemical language, connect equations and practical observations, interpret periodic trends and apply salt-preparation rules to unfamiliar examples.
Hydrochloric acid
Hydrochloric acid dissociates as HCl(aq) -> H+(aq) + Cl-(aq). The chloride ion is the acid residue. A single arrow is used because dissociation is treated as complete.
Nitric acid
Nitric acid dissociates as HNO3(aq) -> H+(aq) + NO3-(aq). Nitrate salts are named from the nitrate ion and are soluble according to the general solubility rules.
Sulfuric acid
At this syllabus level, sulfuric acid may be represented as H2SO4(aq) -> 2H+(aq) + SO4 2-(aq), showing that one formula unit can supply two hydrogen ions. Charge and atom totals must balance.
Checking equations
A dissociation equation must conserve atoms and charge. State symbols should be included. Do not place coefficients as subscripts: 2H+ means two ions, while H2 would mean a molecule containing two hydrogen atoms.
Practical or data skill
Balance a set of acid dissociation equations and check total charge on both sides.
Examination tip
Use a single arrow for complete dissociation and a reversible arrow for partial dissociation.
Review questions and suggested answers
Question 1
Write the dissociation equation for HCl.
Suggested answer
HCl(aq) -> H+(aq) + Cl-(aq).
Question 2
How many H+ ions can one H2SO4 unit provide in the syllabus model?
Suggested answer
Two.
Question 3
What nitrate ion forms from HNO3?
Suggested answer
NO3-(aq).
