This section tests the identification of unknown cations and anions through a series of "Observations and Inferences".
| Procedure | Observation (1 mark each) | Inference (1 mark each) | | :--- | :--- | :--- | | Add dilute HNO₃ to solid U. | Effervescence (bubbles) of a colorless gas. | CO₃²⁻ or HCO₃⁻ present. | | Gas turns limewater. | White precipitate forms in limewater; gas is CO₂. | Carbonate confirmed. | kcse 2006 chemistry paper 3 marking scheme
Adding reagents like aqueous sodium sulphate or sodium hydroxide. Common Marking Points: This section tests the identification of unknown cations
In the 2006 paper, candidates were provided with Solid E . Heating: Observing effects of strong heat on the solid. Solubility: Dissolving in water and filtering. | CO₃²⁻ or HCO₃⁻ present
For every Kenyan student preparing for the Kenya Certificate of Secondary Education (KCSE) examinations, the phrase "past papers" is a mantra. However, smart students know that doing the paper is only half the battle; the real learning happens when you review the answers against the official marking scheme. This is especially true for practical subjects.
