This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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Here is a table of possible observations and their corresponding inferences for the qualitative analysis of mixture C, as you would record them during the experiment. | Test | Possible Observation | Inference | | :--- | :------------------- | :-------- | | (a) Put all of C into a beaker and add about 5 cm^3 of dil. HNO_3. Stir the mixture and filter. Keep the residue and divide the filtrate into two portions. | Effervescence occurs; a colorless, odorless gas is evolved which turns limewater milky. | CO_3^2- (carbonate) is present in the inorganic salt. | | | No effervescence. | CO_3^2- (carbonate) is absent. | | | A blue solution is formed, and a white residue remains. | A Cu^2+ salt is soluble in dilute HNO_3; an insoluble organic compound or inorganic salt is present. | | | A colorless solution is formed, and a white residue remains. | A colorless cation salt is soluble in dilute HNO_3; an insoluble organic compound or inorganic salt is present. | | (b) (i) To the first portion of the filtrate, add NaOH(aq) in drops, then in excess. | White precipitate, insoluble in excess NaOH. | Mg^2+ or Ca^2+ is present. | | | White precipitate, soluble in excess NaOH. | Al^3+, Zn^2+, or Pb^2+ is present. | | | Blue precipitate, insoluble in excess NaOH. | Cu^2+ is present. | | | Green precipitate, insoluble in excess NaOH. | Fe^2+ is present. | | | Reddish-brown precipitate, insoluble in excess NaOH. | Fe^3+ is present. | | (b) (ii) To the second portion of the filtrate, add NH_3(aq) in drops, then in excess. | White precipitate, insoluble in excess NH_3. | Al^3+ or Mg^2+ is present. | | | White precipitate, soluble in excess NH_3. | Zn^2+ is present. | | | Blue precipitate, soluble in excess NH_3 to form a deep blue solution. | Cu^2+ is present. | | | Green precipitate, insoluble in excess NH_3. | Fe^2+ is present. | | | Reddish-brown precipitate, insoluble in excess NH_3. | Fe^3+ is present. | | (c) To the residue, add about 2 cm^3 of distilled water. Boil the mixture and add few drops of iodine solution. | Solution turns blue-black. | Starch is present in the residue (as the organic compound). | | | Solution remains yellow/brown (color of iodine). | Starch is absent in the residue. | 3 done, 2 left today. You're making progress.