Inorganic Chemistry

Step 1: Concept
Molecules or ions having no unpaired electrons are diamagnetic.
Step 2: Analysis
For (6 electrons), the configuration is .
Step 3: Conclusion
Since all electrons are paired, it is diamagnetic.
Final Answer: (C)

Step 1: Concept
.
Step 2: Analysis
* Atomic weight of metal . * Formula of chloride is (as metal is bivalent). * Molecular weight .
Step 3: Conclusion
Molecular weight .
Final Answer: (C)

Step 1: Process
In a ruby laser, chromium atoms are excited to higher energy levels by a flash of light.
Step 2: Transition
These atoms drop to a metastable state before the laser action occurs.
Step 3: Conclusion
The stimulated emission that produces the laser light happens during the transition from this metastable state to the ground state.
Final Answer: (c)

Step 1: Concept
NMR involves the interaction of atomic nuclei (like protons) with an external magnetic field.
Step 2: Mechanism
When radiofrequency energy matches the energy difference between spin states, the proton "flips" its orientation.
Step 3: Identification
This specific flip is the fundamental basis of Nuclear Magnetic Resonance (NMR).
Final Answer: (a)

Step 1: Understanding the oxide.
The compound is iron(III) oxide, also known as ferric oxide. It is an inorganic compound that forms when iron reacts with oxygen in excess.

Step 2: Behavior of with acids and bases.
To determine the nature of , we need to analyze how it reacts with acids and bases. - reacts with acids such as hydrochloric acid to form iron salts, such as iron chloride: This reaction indicates that behaves as an acid. - also reacts with strong bases like sodium hydroxide to form soluble complex compounds, such as ferrate ions: This reaction indicates that behaves as a base.

Step 3: Conclusion.
Since reacts both with acids and bases, it is considered an amphoteric oxide, which can act as both an acid and a base. Thus, the correct answer is is amphoteric, corresponding to option (3).

Step 1: Understanding the Concept:
CO dissolves in water to form carbonic acid (H CO ), which is acidic. Chromate (yellow) converts to dichromate (orange-red) in acidic medium.
Step 2: Detailed Explanation:
2CrO (yellow) + 2H Cr O (orange-red) + H O.
CO + H O H CO 2H + CO .
Step 3: Final Answer:
Thus, colour changes from yellow to orange-red.

Concept: Grignard reagents (RMgX) are formed when alkyl/aryl halides react with Mg in dry ether. However, any compound containing an acidic hydrogen (–OH, –NH, –SH) prevents their formation because it reacts with the Grignard reagent.

Step 1: Analyze each option
(A) CH =CHBr → forms Grignard reagent
(B) CH CH I → forms Grignard reagent
(C) CH OHCH Br → contains –OH group
(D) CH COCH → no halogen, so irrelevant here

Step 2: Effect of –OH group
The –OH group has acidic hydrogen which reacts with RMgX: Conclusion:
Thus, CH OHCH Br does not form Grignard reagent.

Concept: Diagonal relationship in periodic table

Step 1: Li–Mg and B–Al show diagonal similarity.

Step 2: Ca–Mg belong to same group.

Step 3: Na–K also belong to same group.

Step 4: Only Li–Mg is a diagonal pair (unique).
Conclusion:
Different pair = Li–Mg

Concept: Valency based on achieving octet

Step 1: Element A has 3 valence electrons → valency = 3.

Step 2: Element B has 6 valence electrons → valency = 2.

Step 3: Combine using cross valency method.
Conclusion:
Compound formed = A B

Concept: Reducing power depends on ease of electron loss

Step 1: Down the group, atomic size increases.

Step 2: Ionization energy decreases from Be to Ba.

Step 3: Lower ionization energy means easier loss of electrons.

Step 4: Hence reducing power increases down the group.
Conclusion:
Reducing activity increases from Be to Ba

Step 1: Understanding the Concept:
Brine is a saturated solution of NaCl containing impurities like CaCl , MgCl , etc. The process involves precipitating pure NaCl from this solution.
Step 2: Detailed Explanation:
When HCl gas is passed through the brine solution, it dissociates to give H and Cl ions. The high concentration of Cl ions (common ion) from HCl suppresses the dissociation of NaCl ( ) by the common ion effect. This shifts the equilibrium backwards, leading to the precipitation of pure NaCl. The impurities, being more soluble, remain in the solution.
Step 3: Final Answer:
Hence, the purification is based on the common ion effect, option (A).

Step 1: Understanding the Concept:
Neil Bartlett discovered the first noble gas compound in 1962.
Step 2: Detailed Explanation:}}
Bartlett observed that PtF (a strong oxidizing agent) could oxidize O to O [PtF ] . Since the ionization energy of Xe (1170 kJ/mol) is similar to that of O (1175 kJ/mol), he reasoned that PtF could also oxidize Xe. He reacted Xe with PtF and obtained the first noble gas compound, xenon hexafluoroplatinate, Xe [PtF ] .
Step 3: Final Answer:
The first noble gas compound prepared was Xe [PtF ] , option (B).

Step 1: Understanding the Concept:
Conc. is a strong dehydrating agent.
Step 2: Detailed Explanation:
Conc. acts as a dehydrating agent, removing water from sugar and leaving carbon (char).
Step 3: Final Answer:
acts as a dehydrating agent.

Step 1: Understanding the Concept:
Radon is radioactive.
Step 2: Detailed Explanation:
Radon is radioactive and used in radiotherapy for cancer treatment.
Step 3: Final Answer:
Radon is used for cancer treatment.

Step 1: Understanding the Concept:
CO reacts with lime water.
Step 2: Detailed Explanation:
Ca(OH) + CO CaCO ↓ + H O
White precipitate of CaCO forms.
Step 3: Final Answer:
CaCO is precipitated.

Step 1: Understanding the Concept:
Ferric alum is Fe (SO ) ·(NH ) SO ·24H O.
Step 2: Detailed Explanation:
Ferric alum contains 24 water molecules.
Step 3: Final Answer:
x = 24.

Step 1: Understanding the Concept:
Sulfur reacts with hot NaOH.
Step 2: Detailed Explanation:
6NaOH + 3S 2Na S + Na SO + 3H O
Step 3: Final Answer:
A is Na SO .

Step 1: Understanding the Concept:
Silicon halides hydrolyze completely.
Step 2: Detailed Explanation:
SiF + 4H O Si(OH) + 4HF
Step 3: Final Answer:
Product is Si(OH) (silicic acid).

Step 1: Understanding the Concept:
Flux removes impurities.
Step 2: Detailed Explanation:
P O is acidic oxide, reacts with basic impurity CaO.
Step 3: Final Answer:
P O acts as acidic flux.

Step 1: Understanding the Concept:
Metal oxides are basic.
Step 2: Detailed Explanation:
Na O reacts with water to form NaOH (base).
Step 3: Final Answer:
Sodium oxide is basic.

Step 1: Understanding the Concept:
Conc. HNO is a strong oxidizing agent.
Step 2: Detailed Explanation:
HNO forms a protective layer of Fe O on iron surface.
Step 3: Final Answer:
Layer is Fe O .

Step 1: Understanding the Concept:
Ozone is a strong oxidizing agent.
Step 2: Detailed Explanation:
O + 2KI + H O 2KOH + I + O
Iodine turns starch blue.
Step 3: Final Answer:
Liberated substance is iodine.

Step 1: Understanding the Concept:
Iron reacts with SO at high temperature.
Step 2: Detailed Explanation:
3Fe + SO 2FeO + FeS
Step 3: Final Answer:
Products are FeO and FeS.

Concept: (potassium tetraiodomercurate(II)) is known as Nessler's reagent.

Step 1: Use of Nessler's reagent. It is used to detect the presence of ammonia (NH ) or ammonium ions (NH ).

Step 2: Reaction and observation. When Nessler's reagent is added to a solution containing NH , a brown precipitate (or yellow coloration) is formed:

Step 3: Why not other ions? Cl , NO , NO do not give a positive test with Nessler's reagent.

Concept: Important biological molecules and their metal ion components.

Step 1: Check each statement.
• (A) Chlorophyll contains Mg and is responsible for photosynthesis (carbohydrate synthesis) → True.
• (B) Haemoglobin (Fe ) binds oxygen reversibly to form oxyhaemoglobin → True.
• (C) Acetyl salicylic acid is the chemical name of aspirin → True.
• (D) Vitamin B (cobalamin) contains cobalt (Co ), not magnesium. Magnesium is in chlorophyll. → False.

Concept: In this reaction, manganese dioxide ( ) is oxidized from the +4 oxidation state to the +7 oxidation state. Concentrated and (lead dioxide) act as strong oxidizing agents in an acidic medium.

Step 1: Identify the oxidizing conditions. is a very strong oxidizing agent, especially in the presence of concentrated . It can oxidize (in ) to .

Step 2: Write the reaction. The oxidation of in acidic medium produces permanganic acid ( ): Alternatively:

Step 3: Identify the pink colour. Permanganic acid ( ) is a strong acid that dissociates to give (permanganate ions) in solution. Permanganate ions are known for their characteristic pink to purple colour. This colour is observed in the solution.

Step 4: Why not other options?
• (A) — Potassium permanganate is a salt that also gives a purple colour, but potassium ions ( ) are not present in the reaction mixture (no potassium source).
• (B) — Correct; formed in the acidic medium (conc. ).
• (C) — Lead permanganate is a solid that is also purple, but it is not the primary product formed under these conditions.
• (D) — This compound does not contain manganese in the +7 oxidation state.

Concept: Many inorganic compounds have common names based on their historical uses, sources, or appearance.

Step 1: Match A: (Sodium nitrate). Sodium nitrate occurs naturally in large deposits in the Atacama Desert in Chile. It was historically mined as a source of nitrates for fertilizers and gunpowder.

Step 2: Match B: (Sodium ammonium hydrogen phosphate). This compound is known as microcosmic salt. It was originally obtained from human urine ("microcosm" means "little world," referring to the human body) and is used in analytical chemistry for bead tests.

Step 3: Match C: (Sodium bicarbonate). Sodium bicarbonate decomposes to release carbon dioxide when heated, causing dough to rise. This property makes it useful in baking.

Step 4: Match D: (Sodium carbonate decahydrate). This hydrated form of sodium carbonate is used as a cleaning agent for laundry.

Step 5: Final matching. Looking at the codes, this corresponds to option (b).

Concept: Hybridisation depends on number of electron pairs and geometry.

Step 1: XeF .
Square planar

Step 2: H O.
Bent shape

Step 3: PCl .
Trigonal bipyramidal

Step 4: [Pt(NH ) ] .
Square planar (d ) Final Matching:

Concept: Common ion effect — the suppression of ionization of a weak electrolyte by the addition of a strong electrolyte containing a common ion.

Step 1: Identify the weak electrolyte. (ammonium hydroxide) is a weak base that partially ionizes as:

Step 2: Role of . is a strong electrolyte and dissociates completely: It provides a high concentration of ions (common ion).

Step 3: Apply common ion effect. Due to the high concentration of from , the equilibrium of shifts backward (Le Chatelier's principle), suppressing its ionization.

Step 4: Effect on . Since ionization of is suppressed, fewer ions are produced.

Step 5: Why add before in qualitative analysis? This controlled low allows selective precipitation of Group III cations (Al , Fe , Cr ) as hydroxides, while preventing precipitation of higher group cations like Mg , Zn , etc., which require higher .

Concept: acts as both oxidizing and reducing agent.

Step 1: Reaction.

Step 2: Explanation.
• Part of iron is oxidized to FeO
• Part combines with sulfur to form FeS

Step 3: Conclusion. Products are FeO and FeS.

Concept: Passivation occurs due to formation of a protective oxide layer.

Step 1: Nature of conc .
It acts as a strong oxidizing agent.

Step 2: Formation of oxide layer.


Step 3: Effect.
This compact oxide layer prevents further reaction → iron becomes passive.

Concept: forms an ammoniacal buffer that maintains low but controlled concentration.

Step 1: Role of buffer. suppresses ionization of , keeping low.

Step 2: Precipitation condition. Only ions forming highly insoluble hydroxides at low will precipitate.

Step 3: Why others do not precipitate.
• Zn → forms soluble complex
• Mg , Ca → require higher concentration

Concept: Use VSEPR theory: count bond pairs and lone pairs.

Step 1:
AX E square planar

Step 2:
AX tetrahedral

Step 3:
AX E see-saw

Step 4:
AX E square pyramidal

Concept:
• is strong field pairing diamagnetic
• is strong field pairing diamagnetic

Step 1:
Ni , , strong field , square planar, diamagnetic

Step 2:
Ni , , , tetrahedral, diamagnetic

Step 3: Conclusion.
Both complexes are diamagnetic.

Concept: Bond order: where = bonding electrons, = antibonding electrons.

Step 1: Calculate bond orders (I) : (II) : Electronic configuration gives: (III) : (IV) : (V) :

Step 2: Compare Species with same bond order: Final Answer:

Concept: Electronegativity trends:
•Increases across a period (left to right)
•Decreases down a group

Step 1:
•Si and C belong to same group →
•P and N belong to same group →

Step 2: Arrange from lowest to highest: