Step 1: Choose HKDSE Topic(s) First
0 Topics SelectedSelect one or multiple topics (from Topic 1b to 15c) to load and arrange reactions in ascending syllabus order.
Tip: Reactions spanning multiple topics appear under each relevant topic in ascending order.
One card · one reaction or test · stated conditions — 219 scenarios
Observation wording: “The solution changes from purple to yellow-brown.” “Colourless gas bubbles are evolved.” “A white precipitate forms.” Name the material and give both colours; distinguish precipitation, dissolution and gas evolution.
Choose a topic, then a reaction family or reagent. Salt tests show initial precipitation and the effect of excess reagent in order. Different redox addition orders have separate entries. The quiz uses the same reviewed records.
Redox coverage includes common permanganate, dichromate, iron(III), halogen, peroxide, nitric-acid and concentrated-sulfuric-acid examples. Only reacting scenarios under the stated conditions have cards. Useful no-change comparisons stay within the relevant reminders.
Precipitation coverage includes common halides, sulfates, carbonates, hydroxides, excess alkali/ammonia tests and soap scum. Cards name the soluble salt solutions; equations distinguish spectator ions from reacting ions.
Original practice for HKDSE Chemistry. Apply the stated conditions and any information given in the question.
HKDSE Gas Tests
H2(g): Burning splint → 'pop' sound
O2(g): Glowing splint → relights
CO2(g): A white precipitate forms in limewater
Cl2(g): Moist litmus paper changes from blue to red, then from red to white
NH3(g): Moist litmus paper changes from red to blue
SO2(g): Acidified dichromate solution changes from orange to green
Excess Alkali Complexes
Excess NaOH(aq) dissolves :
Al(OH)3 → [Al(OH)4]-(aq)
Pb(OH)2 → [Pb(OH)4]2-(aq)
Zn(OH)2 → [Zn(OH)4]2-(aq)
Excess NH3(aq) dissolves :
Zn(OH)2 → [Zn(NH3)4]2+(aq) (colourless)
Cu(OH)2 → [Cu(NH3)4]2+(aq) (deep blue)
Ag2O → [Ag(NH3)2]+(aq) (colourless)
Key Ion & Vanadium Colors
Aqueous Ions: Cu2+ (blue), Fe2+ (pale green), Fe3+ (yellow/brown), Cr3+ (green), MnO4- (purple), Cr2O72- (orange)
Vanadium : VO2+ (+5, yellow) → VO2+ (+4, blue) → V3+ (+3, green) → V2+ (+2, violet)
Reactivity & Halides
Metals: K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Pt > Au
Silver Halides + AgNO3(aq)/HNO3(aq):
AgCl(s) (white), AgBr(s) (creamy), AgI(s) (yellow)
Step 1: Choose Quiz Topic(s) First
0 Topics Selected Pool: 0 QsReviewed questions on observations, equations and correct/incorrect statements. Shared questions appear only once when topics overlap.
Up to 20 unique questions are drawn from your chosen topics. Topics 13–15 are elective; unfamiliar reaction details are supplied in the question. Select the topics you study.
20-Question Randomized HKDSE Quiz
Randomly draws 20 questions from your selected topic(s) and shuffles their order, with instant answer explanations aligned with HKDSE topics and PDF report export.
Instant feedback on every selection
Review rationales below each question