Systematic Qualitative Analysis of Inorganic Salts

Flashcards covering the systematic qualitative analysis of inorganic salts, including preliminary and confirmatory tests for anions and cations, laboratory procedures, and chemical reactions.

What is the distinction between macro, semimicro, and micro analysis in qualitative analysis based on substance amount?

Macro analysis uses $0.1$ to $0.5\,g$ of substance and about $20\,mL$ of solution; semimicro analysis needs $0.05\,g$ of substance and $1\,mL$ of solution; and micro analysis requires a very small amount of substance.

In the formation of an inorganic salt, which parts are contributed by the acid and the base?

The part contributed by the acid is called the anion, and the part contributed by the base is called the cation.

What characterizes the reaction of a Sulphide ($S^{2-}$) ion with dilute sulphuric acid ($H_2SO_4$)?

A colourless gas with the smell of rotten eggs ($H_2S$) is evolved, which turns lead acetate paper black due to the formation of lead sulphide ($PbS$).

Why does the milkiness disappear when excess $CO_2$ is passed through lime water during the Carbonate test?

The milkiness disappears due to the formation of calcium hydrogen carbonate, $(Ca(HCO_3)_2)$, which is soluble in water.

What is the observation for the sodium nitroprusside test used to confirm Sulphide ($S^{2-}$) ions?

A purple or violet colouration appears due to the formation of the complex compound $Na_4[Fe(CN)_5NOS]$.

How is the presence of Sulphite ($2- 3 SO$) ions indicated in a preliminary test with dilute sulphuric acid?

By the evolution of a colourless gas ($SO_2$) with a pungent smell like burning sulphur, which turns acidified potassium dichromate solution green.

Describe the observation for the Griss-Ilosvay test (Sulphanilic acid — 1-naphthylamine reagent test) for Nitrite ($NO_2^-$).

Appearance of a red colour indicates the presence of nitrite ions due to the formation of a red azo-dye.

What is the 'fruity odour' test for Acetate ($CH_3COO^-$)?

Heating the salt with ethanol ($C_2H_5OH$) and concentrated $H_2SO_4$ produces ethyl acetate ($CH_3COOC_2H_5$), which has a characteristic fruity odour.

In the Chromyl chloride test, what result confirms the presence of Chloride ($Cl^-$) ions?

Passing the evolved gas through $NaOH$ results in a yellow solution; upon acidifying with acetic acid and adding lead acetate, a yellow precipitate of lead chromate ($PbCrO_4$) forms.

What are the observations for Bromide ($Br^-$) and Iodide ($I^-$) in the layer test using chloroform or carbon tetrachloride?

A brown colouration in the organic layer confirms bromide ions, while a violet colouration in the organic layer confirms iodide ions.

What is the chemical composition of the dark brown ring formed in the test for Nitrate ($NO_3^-$)?

The brown ring is caused by nitroso ferrous sulphate ($[Fe(NO)]SO_4$).

How are Phosphate ($PO_4^{3-}$) ions confirmed?

By adding concentrated $HNO_3$ and ammonium molybdate solution and heating to boiling, which forms a canary yellow precipitate of ammonium-phosphomolybdate ($(NH_4)_3[P (Mo_3O_{10})_4]$).

What flame colours are observed for $Ba^{2+}$, $Sr^{2+}$, and $Ca^{2+}$ ions?

$Ba^{2+}$ gives an apple green flame; $Sr^{2+}$ gives a crimson red flame; and $Ca^{2+}$ gives a brick red flame.

What is formed when borax ($Na_2B_4O_7 \cdot 10H_2O$) is heated on a platinum wire?

It loses water of crystallisation and decomposes to give sodium metaborate ($NaBO_2$) and boric anhydride ($B_2O_3$), which form a colourless transparent bead.

What cation is indicated if a charcoal cavity test produces a yellow residue when hot and a white residue when cold?

Zinc ion ($Zn^{2+}$).

Define aqua regia and its usage in cation analysis.

Aqua regia is a mixture of concentrated $HCl$ and concentrated $HNO_3$ in the ratio $3:1$; it is used to dissolve salts that are insoluble in individual concentrated acids.

What is the Nessler's reagent test for Ammonium ($NH_4^+$) ions?

Passing ammonia gas through Nessler's reagent ($K_2HgI_4$) produces a brown precipitate of basic mercury (II) amido-iodine ($HgO \cdot Hg(NH_2)I$).

Which reagents are used to precipitate Group-III cations ($Fe^{3+}$, $Al^{3+}$)?

Ammonium hydroxide ($NH_4OH$) in the presence of ammonium chloride ($NH_4Cl$).

What is the 'lake test' for Aluminium ($Al^{3+}$)?

Adding blue litmus and then $NH_4OH$ drop by drop produces a blue mass ('lake') floating in a colourless solution as aluminium hydroxide adsorbs the blue colour.

What is the confirmatory test for Nickel ($Ni^{2+}$) ions in Group-IV?

The formation of a bright red precipitate when dimethyl glyoxime is added to an alkaline solution containing nickel chloride.