b) List one cation whose salts is likely to have the colour (c) blue (b) white (c) brown (d) green. List three (3) cations whose salts are very soluble in water irrespective of the anion. An aqueous solution of an organic compound turned litmus paper from blue to red.

Here are the answers to the questions:

b)

• I) One cation whose salts are likely to have a green colour is $\boxed{\text{Fe}^{2+}}$.
• II) Three cations whose salts are very soluble in water irrespective of the anion are $\boxed{\text{Na}^{+}}$, $\boxed{\text{K}^{+}}$, and $\boxed{\text{NH}_{4}^{+}}$.
• III) An aqueous solution of an organic compound turned litmus paper from blue to red.

Q3

• a) Preliminary inference: The compound is $\boxed{\text{acidic}}$.
• b) Two functional groups: $\boxed{\text{Carboxylic acid}}$ ($\text{-COOH}$) and $\boxed{\text{Phenol}}$ ($\text{-OH}$ attached to a benzene ring).
• c) Reaction with 5% $\text{NaHCO}_{3}$ solution:
  • Carboxylic acid: It will react with $\text{NaHCO}_{3}$ to produce carbon dioxide gas, observed as $\boxed{\text{effervescence}}$.
  • Phenol: It is generally too weak an acid to react with $\text{NaHCO}_{3}$, so $\boxed{\text{no observable reaction}}$ will occur.
• d) Confirmatory tests:
  • Carboxylic acid: Perform an $\boxed{\text{esterification test}}$. Heat the compound with an alcohol (e.g., ethanol) in the presence of a few drops of concentrated sulfuric acid. The formation of a sweet-smelling ester confirms the presence of a carboxylic acid.
  • Phenol: Perform the $\boxed{\text{ferric chloride test}}$. Add a few drops of neutral ferric chloride solution to the compound. A characteristic purple, blue, or green coloration indicates the presence of a phenol.

Q3 A

• I) Two carbonates that do not decompose on direct heating in the solid state are $\boxed{\text{Sodium carbonate}}$ ($\text{Na}_{2}\text{CO}_{3}$) and $\boxed{\text{Potassium carbonate}}$ ($\text{K}_{2}\text{CO}_{3}$).
• II) The class of organic compounds that normally burns with a sooty flame is $\boxed{\text{Aromatic compounds}}$ (or compounds with a high carbon-to-hydrogen ratio).
• III) The brown ring test is normally used to detect the presence of the $\boxed{\text{nitrate ion}}$ ($\text{NO}_{3}^{-}$).
• IV) Two cations that readily impart characteristic colour to a Bunsen flame are $\boxed{\text{Sodium ion}}$ ($\text{Na}^{+}$) and $\boxed{\text{Potassium ion}}$ ($\text{K}^{+}$).

Q3 B

• I) An unknown colourless inorganic sample in water was acidified with dilute nitric acid and 2 drops of silver nitrate ($\text{AgNO}_{3}$)$_{\text{aq}}$ was added, resulting in instant formation of a precipitate. Three anions that are likely to be present in the sample are $\boxed{\text{Chloride ion}}$ ($\text{Cl}^{-}$), $\boxed{\text{Bromide ion}}$ ($\text{Br}^{-}$), and $\boxed{\text{Iodide ion}}$ ($\text{I}^{-}$).
• II) For each of the anions listed in (I), the likely colour of the precipitate formed:
  • $\text{Cl}^{-}$: $\boxed{\text{White precipitate}}$ ($\text{AgCl}$)
  • $\text{Br}^{-}$: $\boxed{\text{Cream precipitate}}$ ($\text{AgBr}$)
  • $\text{I}^{-}$: $\boxed{\text{Yellow precipitate}}$ ($\text{AgI}$)
• III) Procedure to confirm one anion (e.g., Chloride ion): Add $\boxed{\text{dilute aqueous ammonia}}$ to the white precipitate formed. If the precipitate dissolves completely, it confirms the presence of chloride ions ($\text{AgCl}$ is soluble in dilute ammonia).