Qualitative Analysis

Copper (II) carbonate is the correct answer because it fits all the given properties. It is insoluble in water, as indicated by property (i). When heated, it decomposes and gives off carbon dioxide gas, satisfying property (ii). Additionally, when added to dilute sulfuric acid, it also produces carbon dioxide gas, fulfilling property (iii). Calcium hydroxide, sodium carbonate, and zinc oxide do not exhibit all of these properties, making copper (II) carbonate the most suitable option.

Pale green solution: Iron(II) ions (Fe²⁺) in solution often appear pale green.

Green precipitate with excess aqueous sodium hydroxide: Iron(II) hydroxide, Fe(OH)₂, forms a green precipitate when iron(II) ions react with sodium hydroxide.

Alkaline gas given off when warmed with powdered aluminum: This indicates the presence of nitrate ions (NO₃⁻). When nitrates are warmed with powdered aluminum in an alkaline solution, ammonia gas (NH₃) is released.

When aqueous copper (II) sulfate is added to aqueous sodium hydroxide, a precipitation reaction occurs. This means that a solid substance, called a precipitate, is formed. In this case, the precipitate formed is copper (II) hydroxide, which is insoluble in water. The reaction can be represented by the following equation: CuSO4 (aq) + 2NaOH (aq) → Cu(OH)2 (s) + Na2SO4 (aq).

Adding aqueous lead (II) nitrate to the solutions would identify the solutions. This is because when lead (II) nitrate is added to a solution containing iodide ions (such as the one with aqueous sodium iodide), a yellow precipitate of lead (II) iodide is formed. On the other hand, if lead (II) nitrate is added to a solution containing chloride ions (such as the one with aqueous sodium chloride), a white precipitate of lead (II) chloride is formed. Therefore, by observing the color of the precipitate formed, we can identify which solution contains sodium iodide and which contains sodium chloride.

Aqueous sodium hydroxide cannot be used to distinguish between aqueous lead (II) nitrate and aqueous aluminium nitrate because both lead (II) nitrate and aluminium nitrate will form white precipitates when reacted with aqueous sodium hydroxide. Therefore, this test will not provide a reliable distinction between the two compounds.

When sodium chloride and lead (II) nitrate are mixed, a white precipitate of lead chloride is formed. This is because lead chloride is insoluble in water and therefore forms a solid precipitate.

Carbon dioxide and chlorine are the two gases that change the color of damp blue litmus paper. Carbon dioxide turns the litmus paper pink, indicating acidity, while chlorine turns it white, indicating the presence of a strong oxidizing agent.

The correct answer is calcium oxide. When dilute HCl is added to calcium oxide, it reacts to form calcium chloride and water. This reaction does not produce any gas, so no effervescence is observed. When excess aqueous sodium hydroxide is added to the tube, it reacts with the remaining calcium chloride to form calcium hydroxide, which is insoluble in water and appears as a white precipitate. This confirms that the unknown powder was calcium oxide.

Limewater is the only substance among the options that gives a colorless solution when reacted with dilute HCl. Aqueous silver nitrate produces a white precipitate of silver chloride, calcium carbonate reacts to form a white precipitate of calcium chloride, copper (II) oxide forms a blue solution due to the formation of copper chloride, while limewater reacts with HCl to form calcium chloride, which remains in solution and does not produce any visible color change.

When excess barium nitrate is added to dilute sulfuric acid, a reaction occurs between the barium nitrate and sulfuric acid, resulting in the formation of a precipitate. The precipitate is then removed by filtration, leaving behind the ions that were present in the filtrate. Since barium nitrate is a salt composed of Ba2+ and NO3- ions, and sulfuric acid is an acid composed of H+ and SO42- ions, the ions present in the filtrate would be Ba2+, H+, and NO3-.