WAEC Chemistry practical: Identify the substances present in sample C based on the given tests and observations.

Welcome back harunaajuma — been a while! Let's pick up where you left off. Here are the observations and inferences for the WAEC Chemistry practical question: a) Test: Put about half a spatula of C in a boiling tube and heat strongly. Allow it to cool. Observation: The sample chars, a colorless liquid condenses at the cooler part of the test tube, and a gas is evolved which turns lime water milky. Inference: Presence of an organic compound (chars), water of crystallization or constitution (colorless liquid), and a carbonate or oxalate (gas turns lime water milky, indicating carbon dioxide*, CO_2). b) i) Test: To the remaining portion of C, add about 2 cm^3 of dilute trioxonitrate (V) acid, HNO_3. Stir well to dissolve and filter, keep both the filtrate and the residue. Observation: Effervescence occurs, a colorless, odorless gas is evolved which turns lime water milky. Part of the sample dissolves, leaving a white residue. Inference: Presence of carbonate (CO_3^2-). The gas evolved is carbon dioxide* (CO_2). The sample contains both soluble and insoluble components. b) ii) Test: To the residue, add a few drops of iodine solution. Observation: The white residue turns blue-black. Inference: Presence of starch*. c) i) Test: To the first portion of the filtrate obtained in (b)(i), add Sodium Hydroxide Solution (NaOH) in drops and then in excess. Observation: In drops:* A dirty green precipitate is formed. In excess:* The dirty green precipitate is insoluble in excess NaOH. Inference: Presence of iron(II) ions* (Fe^2+). c) ii) Test: To the second portion of the filtrate obtained in (b)(i), add aqueous NH_3 in drops and then in excess. Observation: In drops:* A dirty green precipitate is formed. In excess:* The dirty green precipitate is insoluble in excess NH_3. Inference: Presence of iron(II) ions* (Fe^2+) confirmed. Send me the next one 📸