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| test | observations |
| Add aq. NaOH in excess until no further change is observed. | - ..... (colour) ppt formed
- insoluble in excess aq. NaOH OR soluble in excess aq. NaOH to give ...... (colour) solution Example: - white ppt formed insoluble in excess aq. NaOH (deduction: unknown contains Ca2+) |
| Add aq. NH3 in excess until no further change is observed. | - ..... (colour) ppt formed
- insoluble in excess aq. NH3 OR soluble in excess aq. NH3 to give ...... (colour) solution Example: - light-blue ppt formed soluble in excess NH3 to give a deep-blue solution (deduction: unknown contains Cu2+) |
| Add aq. NaOH in excess until no further change is observed. Warm the mixture. |
- no ppt formed
- colourless, pungent gas evolved - gas turned moist red litmus paper blue (deduction: gas is NH3; unknown contains NH4+) |
| Add aq. NaOH in excess until no further change is observed. Allow the mixture to stand in air. |
- dirty-green ppt formed
- insoluble in excess NaOH - dirty-green ppt turned reddish-brown on standing (deduction: unknown contains Fe2+; iron(II) hydroxide is oxidised to iron(III) hydroxide in air) |
| test | observations |
| Add dilute nitric acid or hydrochloric acid | - effervescence
- colourless, odourless gas produced - gas formed white ppt with limewater (deduction: gas is CO2; unknown contains CO32–) |
| Add dilute nitric acid, followed by silver nitrate solution. Add aq NH3 to the resulting mixture. |
- white ppt formed
- ppt soluble in aq NH3 to give a colourless solution (deduction: unknown contains Cl–) |
| Add dilute nitric acid, followed by silver nitrate solution. Add aq NH3 to the resulting mixture. |
- yellow ppt formed
- ppt insoluble in aq NH3 (deduction: unknown contains I–) |
| Add dilute nitric acid, followed by barium sulfate solution | - white ppt formed (deduction: unknown contains SO42–) |
| Add barium sulfate solution, followed by dilute nitric acid | - white ppt formed - ppt insoluble in nitric acid (deduction: unknown contains SO42–) |
| Add sodium hydroxide, followed by aluminium foil. Heat the mixture gently | - effervescence
- colourless, pungent gas produced - gas turned moist red litmus paper blue (deduction: gas is NH3; unknown contains NO3–) |
| test | observations |
| Add aq. sulfuric acid followed by potassium manganate(VII). | - potassium manganate(VII) turned from purple to colourless
(deduction: unknown contains a reducing agent) |
| Add aq. sulfuric acid followed by potassium manganate(VII). (unknown contains Fe2+) | - potassium manganate(VII) turned from purple to colourless
- solution turned from colourless/ pale green to yellow/ brown (deduction: unknown contains a reducing agent) |
| Add aq. sulfuric acid followed by potassium manganate(VII). (unknown contains I–) | - potassium manganate(VII) turned from purple to colourless
- solution turned from colourless to yellow/ brown (deduction: unknown contains a reducing agent) |
| Add aq. potassium iodide. Add starch solution to the resulting mixture. |
- brown/ yellow solution formed - solution turned blue black. (deduction: unknown contains an oxidising agent) |
| test | observations |
| Heat the solid strongly until no further changes are seen (unknown is NH4Cl) |
- white fumes produced
- gas turned moist blue litmus red - white solid formed at the mouth of test-tube (deduction: gas is HCl; unknown is NH4Cl) |
| Heat the solid strongly until no further changes are seen (unknown is KClO3) |
- colourless, odourless gas produced
- gas relighted a glowing splint (deduction: gas is O2) |
| Heat the solid strongly until no further changes are seen (unknown is NaHCO3) |
- colourless, odourless gas produced
- gas formed white ppt with limewater - colourless liquid formed at the mouth of test-tube - liquid turned cobalt(II) chloride paper from blue to pink. (deduction: gas is CO2; colourless liquid is H2O; solid is NaHCO3) |
| Heat the solid strongly until no further changes are seen (unknown is CuCO3) |
- Green solid turned black - colourless, odourless gas produced - gas formed white ppt with limewater (deduction: gas is CO2; colourless liquid is H2O; solid is NaHCO3) |
| Heat the solid strongly until no further changes are seen Allow the solid to cool. (unknown is ZnCO3) |
- yellow solid formed on heating - yellow solid turned white when cool - colourless, odourless gas produced - gas formed white ppt with limewater (deduction: gas is CO2; solid is ZnCO3 which decomposed to form ZnO) |
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