Among the following cations, the number of cations which will give characteristic precipitate in their identification tests with K₄[Fe(CN)₆]$\mathrm{K}_4[\mathrm{Fe}(\mathrm{CN})_6]$ is: Cu²⁺$\mathrm{Cu}^{2+}$ , Fe³⁺$\mathrm{Fe}^{3+}$ , Ba²⁺$\mathrm{Ba}^{2+}$ , Ca²⁺$\mathrm{Ca}^{2+}$ , NH₄^+$\mathrm{NH}_4^+$ , Mg²⁺$\mathrm{Mg}^{2+}$ , Zn²⁺$\mathrm{Zn}^{2+}$

Core Logic

The Griss-Ilosvay test is the standard diagnostic test for Nitrite ions (NO₂^-$\mathrm{NO_2^-}$).\nReaction sequence:\nNO₂^- + CH₃COOH arrow HNO₂ + CH₃COO^-$$NO_2^- + CH_3COOH \rightarrow HNO_2 + CH_3COO^-$$\n1. The nitrous acid (HNO₂$HNO_2$) diazotizes sulphanilic acid to form a diazonium salt.\n2. This diazonium salt then couples with α$\alpha$-naphthylamine (1-Naphthylamine) to produce a distinct red azo-dye.\n

Final Conclusion

Both statements perfectly describe the reaction mechanism and reagents for the Griss-Ilosvay test. Both are true.

Pattern Recognition

Tests utilizing diazotization followed by coupling almost always produce colored azo dyes. Knowing the name-to-reagent mapping (Griss-Ilosvay = Sulphanilic acid + Naphthylamine) guarantees the answer.

Chapter Mix

Class 12 Chemistry: Principles Related to Practical Chemistry Class 12 Chemistry: Amines

Related Formula

Na₂S + Na₂[Fe(CN)₅NO] arrow Na₄[Fe(CN)₅NOS]$\text{Na}_2\text{S} + \text{Na}_2[\text{Fe}(\text{CN})_5\text{NO}] \rightarrow \text{Na}_4[\text{Fe}(\text{CN})_5\text{NOS}]$

AI responses may include mistakes.

Core Logic

Sulphide ion (S²⁻$S^{2-}$) undergoes a qualitative verification test when reacted with sodium nitroprusside. Sodium extract of the salt containing sulphide forms sodium sulphide (Na₂S$\mathrm{Na_2S}$).

When sodium nitroprusside solution is added to the sodium carbonate extract, the sulphide reacts to yield a deep violet/purple coloured complex called sodium thionitroprusside:

Step 1: Verification

This specific purple/violet reaction occurs exclusively for the identification of the Sulphide ion (S²⁻$S^{2-}$).

Pattern Recognition

Mnemonic: 'Nitroprusside turns purple for Sulphide'. This is a highly specific redox/substitution reaction of coordination complexes used inside analytical laboratory practices.

Chapter Mix

Class 11 Chemistry: Practical Chemistry

Related Formula

Precipitation equations matching standard analytical profiles:

Core Logic

Let's examine each analytical chemistry reaction step row-by-row:

• Reaction (A) produces Cu₂[Fe(CN)₆]$\mathrm{Cu_2[Fe(CN)_6]}$, confirming a chocolate brown residue profile (Correct).
• Reaction (B) forms complex Fe₄[Fe(CN)₆]₃$\mathrm{Fe_4[Fe(CN)_6]_3}$, yielding Prussian Blue coloration (Correct).
• Reaction (C) yields potassium zinc ferrocyanide matrix K₂Zn₃[Fe(CN)₆]₂$\mathrm{K_2Zn_3[Fe(CN)_6]_2}$, appearing as a white or bluish-white solid precipitate (Correct).
• Reactions (D) & (E) do not form the described colored precipitates with this reagent under regular analytical configurations.

Step 1: Selection

Thus, only tests A, B, and C provide correct observations.

Pattern Recognition

Potassium ferrocyanide K₄[Fe(CN)₆]$\mathrm{K_4[Fe(CN)_6]}$ is a vital reagent for identifying transition metal cations. Note the specific colors: Copper yields chocolate brown, Iron(III) gives Prussian blue, and Zinc forms a white solid.

Chapter Mix

Class 12 Chemistry: Practical Chemistry Class 12 Chemistry: Coordination Compounds

Related Formula

A primary standard is a highly pure, stable chemical substance with a known, definite composition that can be directly weighed. It must not be hygroscopic, deliquescent, or easily oxidized by air.

Core Logic

Evaluate each substance:

• Na₂Cr₂O₇$\mathrm{Na}_2\mathrm{Cr}_2\mathrm{O}_7$: Highly hygroscopic (unlike K₂Cr₂O₇$\mathrm{K}_2\mathrm{Cr}_2\mathrm{O}_7$), absorbs water from air, composition varies arrow$\rightarrow$ Cannot be used.
• Oxalic acid: Highly stable, non-hygroscopic, definite composition arrow$\rightarrow$ Can be used.
• NaOH$\mathrm{NaOH}$: Extremely hygroscopic, absorbs moisture and CO₂$\mathrm{CO}_2$ from air arrow$\rightarrow$ Cannot be used.
• FeSO₄ · 6H₂O$\mathrm{FeSO}_4 \cdot 6\mathrm{H}_2\mathrm{O}$: Easily oxidized by air, unstable composition arrow$\rightarrow$ Cannot be used.
• Sodium tetraborate (Borax): Highly stable, clear hydration state arrow$\rightarrow$ Can be used.

Step 1: Select incorrect standards

The compounds that should not be used are A, C, and D. This corresponds to Option (4).

Pattern Recognition

Sodium salts of di-chromate (Na₂Cr₂O₇$\mathrm{Na}_2\mathrm{Cr}_2\mathrm{O}_7$) are highly hygroscopic, whereas potassium di-chromate (K₂Cr₂O₇$\mathrm{K}_2\mathrm{Cr}_2\mathrm{O}_7$) is non-hygroscopic and works as an excellent primary standard. Deliquescent bases like NaOH$\mathrm{NaOH}$ and easily oxidized transition metal salts like Mohr's salt counterparts can never serve as primary standards.

Chapter Mix

Class 11 Chemistry: Practical Chemistry