CUET UG Chemistry Booster Test

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CUET UG Chemistry Booster Test - 3 Nomenclature

⏱️ 30 Minutes

❓ 20 Questions

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CUET UG Chemistry Booster Test - 3 Nomenclature

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QUESTION 1 OF 20

Why is the additive nomenclature system exceptionally vital for compounds like [CoCl₂(NH₃)₄]⁺?

Answer Review

1 Why is the additive nomenclature system exceptionally vital for compounds like [CoCl₂(NH₃)₄]⁺?

A It dictates whether the compound will dissolve in polar solvents.

B It systematically distinguishes between structural and spatial isomers (like cis and trans forms) that share identical empirical formulas.

C It alters the primary valence of the central atom.

D It replaces the need to identify the oxidation state.

💡 Short Explanation

�� Additive nomenclature provides systematic naming. �� It distinguishes coordination isomers and stereoisomers. �� Cis and trans forms require unique identification.

✅ Correct Answer Explanation

Additive nomenclature was developed to provide an unambiguous naming system for coordination compounds. Complexes such as [CoCl₂(NH₃)₄]⁺ can exist as cis and trans isomers that possess the same empirical formula but differ in spatial arrangement. The nomenclature system explicitly identifies these differences through appropriate descriptors, ensuring that each distinct structure receives a unique name. Therefore, the major importance of additive nomenclature is its ability to distinguish structural and stereochemical variations systematically.

❓ Why Other Options Are Incorrect

�� Option A → Solubility depends on intermolecular interactions and is not determined by nomenclature.
�� Option C → Nomenclature does not alter the primary valence or oxidation state of a metal.
�� Option D → Oxidation state determination remains an essential part of coordination compound nomenclature.

🎯 Strategy

Used

Definition Matching

Application:

�� Identify the primary purpose of additive nomenclature in coordination chemistry.

Final Logic:

�� Additive nomenclature uniquely identifies isomers having the same molecular formula.

🧠 Memory Trick

Same Formula, Different Shape → Need Different Name

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Nomenclature of Coordination Compounds

2 Evaluate the following rules from the 2004 IUPAC draft regarding nomenclature. Choose the correct statements:
1. Ligands are sorted alphabetically irrespective of their charge.
2. Anionic ligands must end in -ido.
3. The central atom is always named before the ligands.
4. Neutral complexes are named similarly to complex cations.

A 1, 2, 3

B 1, 2, 4

C 3, 4

D 2, 3, 4

💡 Short Explanation

�� Ligands are arranged alphabetically. �� Anionic ligands generally end with "-ido". �� Metal name comes after ligand names.

✅ Correct Answer Explanation

Evaluate each statement: • Statement 1 → Correct. Ligands are arranged alphabetically irrespective of their charge. • Statement 2 → Correct. Modern IUPAC nomenclature uses the suffix "-ido" for anionic ligands. • Statement 3 → Incorrect. Ligands are named before the central metal atom. • Statement 4 → Correct. Neutral complexes are named in the same manner as cationic complexes. Hence Statements 1, 2 and 4 are correct.

❓ Why Other Options Are Incorrect

�� Option A → Includes Statement 3, which is incorrect.
�� Option C → Omits Statements 1 and 2, which are correct.
�� Option D → Includes Statement 3, which is incorrect and omits Statement 1.

🎯 Strategy

Used

Elimination

Application:

�� Check each statement against IUPAC naming rules.

Final Logic:

�� Statements 1, 2 and 4 are correct while Statement 3 violates the ligand-before-metal rule.

🧠 Memory Trick

Ligands First, Metal Last

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: IUPAC Nomenclature Rules

3 Deduce the correct sequence of components to write the chemical formula for potassium trioxalatoaluminate(III):
1. K
2. [Al
3. ₃
4. (C₂O₄)₃]

A 1, 3, 2, 4

B 2, 4, 1, 3

C 1, 2, 4, 3

D 1, 2, 3, 4

💡 Short Explanation

�� Potassium is the counter cation. �� Three K⁺ ions balance the complex anion. �� Formula becomes K₃[Al(C₂O₄)₃].

✅ Correct Answer Explanation

The complex anion is: [Al(C₂O₄)₃]³⁻ To neutralize the −3 charge, three K⁺ ions are required: K₃[Al(C₂O₄)₃] Thus the sequence is: • 1 → K • 3 → ₃ • 2 → [Al • 4 → (C₂O₄)₃] Therefore the correct order is: 1, 3, 2, 4

❓ Why Other Options Are Incorrect

�� Option B → Places the coordination entity before the counter ion.
�� Option C → Places the subscript after the complex.
�� Option D → Produces an incorrect formula arrangement.

🎯 Strategy

Used

Substitution

Application:

�� Construct the actual chemical formula from the compound name.

Final Logic:

�� Potassium trioxalatoaluminate(III) = K₃[Al(C₂O₄)₃].

🧠 Memory Trick

Counter Ion First, Complex Next

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Writing Formulae of Coordination Compounds

4 In the coordination formula [Co(NH₃)₅(CO₃)]Cl, why is the carbonate group enclosed in parentheses while the ammine group is as well, but chloride is not?

A Carbonate and ammine are polyatomic ligands, whereas chloride is a monoatomic counter ion.

B Carbonate is anionic while ammine is neutral.

C Parentheses indicate the oxidation state of the metal.

D Brackets are strictly for cations, parentheses for anions.

💡 Short Explanation

�� Ligands within the coordination sphere are enclosed appropriately. �� Carbonate and ammine are coordinated ligands. �� Chloride acts as a counter ion.

✅ Correct Answer Explanation

Within the coordination sphere, ligands are attached directly to the central metal ion. Carbonate (CO₃²⁻) and ammine (NH₃) function as ligands and are represented within the coordination entity. Chloride is outside the coordination sphere and acts as a counter ion. Therefore, it is not enclosed as part of the ligand notation.

❓ Why Other Options Are Incorrect

�� Option B → Ligand charge is not the reason for bracket placement.
�� Option C → Parentheses do not indicate oxidation state.
�� Option D → Parentheses are not restricted to anions.

🎯 Strategy

Used

Definition Matching

Application:

�� Identify the role of each species in the coordination compound.

Final Logic:

�� Coordinated ligands are written inside the coordination sphere, counter ions outside.

🧠 Memory Trick

Inside = Ligand, Outside = Counter Ion

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Formula Representation

5 Match the abbreviated ligand (List-I) with the letter used to determine its alphabetical position in a chemical formula (List-II):

List I	List II
1. en (ethane-1,2-diamine)	a. e
2. EDTA	b. p
3. ox (oxalate)	c. o
4. py (pyridine)	d. E

A 1-a, 2-d, 3-c, 4-b

B 1-d, 2-a, 3-b, 4-c

C 1-c, 2-b, 3-a, 4-d

D 1-a, 2-c, 3-d, 4-b

💡 Short Explanation

�� Alphabetization uses ligand abbreviations. �� en begins with e. �� EDTA begins with E, ox with o, py with p.

✅ Correct Answer Explanation

Matching: • 1 → a (en → e) • 2 → d (EDTA → E) • 3 → c (ox → o) • 4 → b (py → p) Hence the correct matching is: 1-a, 2-d, 3-c, 4-b.

❓ Why Other Options Are Incorrect

�� Option B → Incorrectly assigns EDTA and en.
�� Option C → Multiple alphabetical mismatches.
�� Option D → Incorrect assignments for EDTA and oxalate.

🎯 Strategy

Used

Definition Matching

Application:

�� Match each ligand abbreviation with its alphabetical starting letter.

Final Logic:

�� Alphabetization follows the ligand abbreviation itself.

🧠 Memory Trick

en-e, EDTA-E, ox-o, py-p

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Alphabetical Order of Ligands

6 A complex contains one chloride ion, one nitrite ion, and four ammine molecules attached to Cobalt(III). Assuming formula writing rules (alphabetical listing irrespective of charge), which represents the correct formula?

A [CoCl(NO₂)(NH₃)₄]⁺

B [Co(NH₃)₄Cl(NO₂)]⁺

C [Co(NO₂)Cl(NH₃)₄]⁺

D [Co(NH₃)₄(NO₂)Cl]⁺

💡 Short Explanation

�� Ligands are arranged alphabetically. �� Ammine comes before chlorido and nitrito. �� Charge does not affect ordering.

✅ Correct Answer Explanation

Alphabetical order: ammine (A) chlorido (C) nitrito (N) Thus the correct ligand arrangement is: [Co(NH₃)₄Cl(NO₂)]⁺ Therefore Option B follows IUPAC formula-writing rules.

❓ Why Other Options Are Incorrect

�� Option A → Chlorido incorrectly precedes ammine.
�� Option C → Nitrito incorrectly appears first.
�� Option D → Nitrito incorrectly precedes chlorido.

🎯 Strategy

Used

Option Grouping

Application:

�� Arrange ligands according to alphabetical order.

Final Logic:

�� Ammine → Chlorido → Nitrito.

🧠 Memory Trick

A before C before N

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Ligand Ordering Rules

7 In the complex [Cr(NH₃)₃(H₂O)₃]Cl₃, the numerical "unit" multiplier for the ammine ligands in its IUPAC name is represented by:

A Tris

B Tri

C Three

D Tetrakis

💡 Short Explanation

�� Three identical simple ligands are present. �� Simple ligands use mono, di, tri, tetra. �� Ammine is a simple ligand.

✅ Correct Answer Explanation

NH₃ is a simple ligand. When three such ligands are present, the numerical prefix used is "tri". Hence the name contains triammine. Prefixes like bis, tris and tetrakis are reserved for more complex ligand names.

❓ Why Other Options Are Incorrect

�� Option A → Tris is used for complex ligand names.
�� Option C → IUPAC uses prefixes, not ordinary numbers.
�� Option D → Indicates four ligands.

🎯 Strategy

Used

Definition Matching

Application:

�� Identify the appropriate multiplicative prefix.

Final Logic:

�� Three simple ligands = tri.

🧠 Memory Trick

3 Simple Ligands = Tri

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Multiplicative Prefixes

8 Determine the correct IUPAC name for [CoCl₂(en)₂]⁺:

A Dichloridobis(ethane-1,2-diamine)cobalt(III)

B Dichloridodiethylenediaminecobaltate(III)

C Bis(ethane-1,2-diamine)dichloridocobalt(III)

D Dichloridotris(ethane-1,2-diamine)cobalt(III)

💡 Short Explanation

�� Two chlorido ligands → dichlorido. �� Two ethane-1,2-diamine ligands → bis. �� Complex is cationic → cobalt(III).

✅ Correct Answer Explanation

The ligands present are: 2 chlorido ligands → dichlorido 2 ethane-1,2-diamine ligands → bis(ethane-1,2-diamine) Since the complex is cationic, the metal name remains cobalt(III). Therefore the correct name is Dichloridobis(ethane-1,2-diamine)cobalt(III).

❓ Why Other Options Are Incorrect

�� Option B → Incorrect use of cobaltate and ligand naming.
�� Option C → Violates ligand alphabetical order.
�� Option D → Uses tris despite only two en ligands.

🎯 Strategy

Used

Rule Application

Application:

�� Apply ligand naming, prefixes and metal naming rules.

Final Logic:

�� Dichlorido + bis(en) + cobalt(III).

🧠 Memory Trick

Complex Ligand Repeated Twice = Bis

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: IUPAC Naming of Coordination Compounds

9 The distinction between naming a ligand "nitrito-N" versus "nitrito-O" identifies what type of specific ligand behavior?

A Polydentate chelation

B Ambidentate linkage

C Optical isomerism

D Hydrate forming

💡 Short Explanation

�� Nitrite can coordinate through N or O. �� Different donor atoms produce linkage isomers. �� Such ligands are ambidentate.

✅ Correct Answer Explanation

The nitrite ion (NO₂⁻) can coordinate through either nitrogen or oxygen. When the same ligand binds through different donor atoms, linkage isomerism arises. Such ligands are called ambidentate ligands. Therefore nitrito-N and nitrito-O represent ambidentate linkage behavior.

❓ Why Other Options Are Incorrect

�� Option A → Chelation involves multiple donor atoms simultaneously.
�� Option C → Optical isomerism involves non-superimposable mirror images.
�� Option D → Hydrate formation is unrelated.

🎯 Strategy

Used

Definition Matching

Application:

�� Identify the coordination behavior described.

Final Logic:

�� Same ligand, different donor atom = ambidentate linkage.

🧠 Memory Trick

One Ligand, Two Attachment Points

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Ambidentate Ligands and Linkage Isomerism

10 When forming the name of [Co(NH₃)₅(H₂O)]³⁺, which correctly reflects the naming rules for neutral ligands?

A Pentaammineaquacobalt(III)

B Aquapentaamminecobalt(III)

C Pentaaminemonowatercobalt(III)

D Pentaamminemonohydratocobalt(III)

💡 Short Explanation

�� Neutral ligand names are ammine and aqua. �� Ligands are arranged alphabetically. �� Ammine precedes aqua.

✅ Correct Answer Explanation

The ligands present are: 5 NH₃ → pentaammine 1 H₂O → aqua Ligands are named alphabetically before the metal name. Since ammine comes before aqua alphabetically, the correct name is: Pentaammineaquacobalt(III)

❓ Why Other Options Are Incorrect

�� Option B → Incorrect alphabetical order.
�� Option C → "Water" is not the accepted ligand name.
�� Option D → "Hydrato" is incorrect in this context.

🎯 Strategy

Used

Definition Matching

Application:

�� Apply accepted ligand names and alphabetical ordering.

Final Logic:

�� Ammine comes before aqua alphabetically.

🧠 Memory Trick

Ammine Before Aqua

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Neutral Ligand Names and Ordering

11 In the linkage isomer [Co(NH₃)₅(NO₂)]Cl₂, the complex entity is a cation. How must the central metal be formally named?

A Cobaltate(III)

B Cobalt(III)

C Cobaltic(III)

D Cobaltous(II)

💡 Short Explanation

�� The coordination entity is positively charged. �� Cationic complexes retain the normal metal name. �� Oxidation state is indicated using Roman numerals.

✅ Correct Answer Explanation

The coordination entity [Co(NH₃)₅(NO₂)]²⁺ is a cationic complex. According to IUPAC nomenclature, the metal name remains unchanged in cationic and neutral complexes. Therefore, cobalt is named as cobalt(III), where III represents the oxidation state of cobalt. Hence, the correct name of the central metal is cobalt(III).

❓ Why Other Options Are Incorrect

�� Option A → The suffix "-ate" is used only for metals present in complex anions.
�� Option C → "Cobaltic" belongs to older nomenclature and is not accepted in modern IUPAC naming.
�� Option D → Incorrect oxidation state and obsolete nomenclature.

🎯 Strategy

Used

Definition Matching

Application:

�� Determine whether the complex is cationic or anionic.

Final Logic:

�� Cationic complex → retain the normal metal name.

🧠 Memory Trick

Positive Complex = Plain Metal Name

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Naming of Cationic Complexes

12 In the nomenclature of Hg[Co(SCN)₄], the central metal of the complex anion is named:

A Cobalt(II)

B Cobalt(III)

C Cobaltate(III)

D Mercurate(I)

💡 Short Explanation

�� The coordination entity is an anion. �� Anionic complexes require the suffix "-ate". �� Cobalt becomes cobaltate.

✅ Correct Answer Explanation

In Hg[Co(SCN)₄], the coordination entity [Co(SCN)₄] is a complex anion. According to IUPAC nomenclature, when the coordination sphere carries a negative charge, the metal name ends with the suffix "-ate". Therefore cobalt is named cobaltate(III).

❓ Why Other Options Are Incorrect

�� Option A → Used for cationic or neutral complexes.
�� Option B → Missing the mandatory "-ate" suffix.
�� Option D → Mercury is not the central metal of the coordination entity.

🎯 Strategy

Used

Rule Application

Application:

�� Apply the naming rule for anionic complexes.

Final Logic:

�� Anionic complex → metal name ends with "-ate".

🧠 Memory Trick

Negative Complex = Add "-ate"

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Naming of Anionic Complexes

13 The Roman numeral placed in parentheses after the metal's name defines:

A The number of secondary valences

B The charge it would carry if all ligands and shared electron pairs were removed

C The total charge of the coordination sphere

D The number of unshared electron pairs

💡 Short Explanation

�� Roman numerals represent oxidation state. �� Oxidation state is a formal charge. �� It differs from the overall complex charge.

✅ Correct Answer Explanation

The Roman numeral written after the metal name indicates its oxidation state. Oxidation state is defined as the hypothetical charge that the metal would possess if all ligands and shared electron pairs were completely removed. Thus Option B correctly defines the meaning of the Roman numeral.

❓ Why Other Options Are Incorrect

�� Option A → Secondary valence refers to coordination number, not oxidation state.
�� Option C → Overall charge of the complex may differ from the metal oxidation state.
�� Option D → Oxidation state has no relation to the number of lone pairs.

🎯 Strategy

Used

Definition Matching

Application:

�� Recall the formal definition of oxidation state.

Final Logic:

�� Roman numeral = oxidation state.

🧠 Memory Trick

Roman Numeral = Formal Charge

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Oxidation State

14 Determine the oxidation state of the central metal in the complex [Pt(NH₃)(H₂O)Cl₂]:

A 0

B +2

C +4

D -2

💡 Short Explanation

�� NH₃ and H₂O are neutral ligands. �� Each Cl⁻ contributes −1 charge. �� The complex is electrically neutral.

✅ Correct Answer Explanation

Let the oxidation state of Pt be x. NH₃ = 0 H₂O = 0 2Cl⁻ = −2 Since the complex is neutral: x + 0 + 0 − 2 = 0 x = +2 Therefore, the oxidation state of platinum is +2.

❓ Why Other Options Are Incorrect

�� Option A → Would give an overall charge of −2.
�� Option C → Would give an overall charge of +2.
�� Option D → Would give an overall charge of −4.

🎯 Strategy

Used

Substitution

Application:

�� Form the oxidation-state equation using ligand charges.

Final Logic:

�� x − 2 = 0, therefore x = +2.

🧠 Memory Trick

Neutral Ligands Count as Zero

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Determination of Oxidation State

15 The complex [Ni(H₂O)₆]²⁺ is formed when nickel(II) chloride is dissolved in water. By IUPAC rules, this complex is categorized as a:

A Homoleptic neutral complex

B Heteroleptic cationic complex

C Homoleptic cationic complex

D Heteroleptic anionic complex

💡 Short Explanation

�� Only one type of ligand is present. �� The complex has a positive charge. �� Therefore it is homoleptic and cationic.

✅ Correct Answer Explanation

The complex contains six identical aqua ligands. Since only one type of ligand is present, the complex is homoleptic. The overall charge is +2, making it a cationic complex. Hence [Ni(H₂O)₆]²⁺ is a homoleptic cationic complex.

❓ Why Other Options Are Incorrect

�� Option A → The complex is not neutral.
�� Option B → Only one ligand type is present, so it is not heteroleptic.
�� Option D → The complex is positively charged, not anionic.

🎯 Strategy

Used

Definition Matching

Application:

�� Classify using ligand type and overall charge.

Final Logic:

�� One ligand type + positive charge = homoleptic cationic.

🧠 Memory Trick

One Ligand Type = Homo

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Homoleptic and Heteroleptic Complexes

16 In the coordination isomer [Co(NH₃)₆][Cr(CN)₆], the [Cr(CN)₆]³⁻ entity represents:

A The complex cation named first

B The complex anion named second

C A neutral homoleptic species

D The counter ion of a double salt

💡 Short Explanation

�� [Co(NH₃)₆]³⁺ is the complex cation. �� [Cr(CN)₆]³⁻ is the complex anion. �� Anions are named after cations.

✅ Correct Answer Explanation

The compound contains: [Co(NH₃)₆]³⁺ → Complex cation [Cr(CN)₆]³⁻ → Complex anion According to IUPAC nomenclature, the cation is named first and the anion is named second. Therefore [Cr(CN)₆]³⁻ represents the complex anion named after the cation.

❓ Why Other Options Are Incorrect

�� Option A → Describes the complex cation, not the anion.
�� Option C → The species carries a −3 charge and is not neutral.
�� Option D → This is a coordination compound, not a double salt.

🎯 Strategy

Used

Definition Matching

Application:

�� Identify the charge and role of each coordination entity.

Final Logic:

�� Negative coordination entity = complex anion.

🧠 Memory Trick

Positive First, Negative Second

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Complex Ions

17 For the compound [Cr(NH₃)₃(H₂O)₃]Cl₃, how is electrical neutrality achieved in the written formula?

A The +3 charge of the complex cation is balanced by three chloride counter ions, each with a -1 charge.

B The +3 charge is balanced by the neutral ammine and aqua ligands.

C The chromium metal reduces the chloride ions.

D The formula requires no counter ions due to hydration.

💡 Short Explanation

�� The complex ion carries a +3 charge. �� Three chloride ions contribute −3 charge. �� Total charge becomes zero.

✅ Correct Answer Explanation

The coordination entity [Cr(NH₃)₃(H₂O)₃]³⁺ possesses a +3 charge. Each chloride ion contributes −1 charge. Therefore: (+3) + 3(−1) = 0 The positive charge of the complex cation is exactly balanced by three chloride counter ions, producing an electrically neutral compound.

❓ Why Other Options Are Incorrect

�� Option B → NH₃ and H₂O are neutral ligands and cannot neutralize charge.
�� Option C → No reduction process occurs in formula writing.
�� Option D → Counter ions are required for charge balance.

🎯 Strategy

Used

Elimination

Application:

�� Analyze charge balance in the coordination compound.

Final Logic:

�� +3 complex charge requires three Cl⁻ ions.

🧠 Memory Trick

+3 Needs Three Cl⁻

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Charge Balance in Coordination Compounds

18 Which formatting rule prevents ambiguity when defining the exact boundaries of the primary and secondary valences in a written chemical formula?

A Using Roman numerals for ligands

B Avoiding spaces between the metal and ligands within the square brackets

C Writing the counter ion inside the brackets

D Ensuring ligands are written in lowercase

💡 Short Explanation

�� Coordination formulas are written continuously. �� Square brackets define the coordination sphere. �� Spaces can create ambiguity.

✅ Correct Answer Explanation

The square brackets identify the coordination sphere. Writing the metal and ligands continuously within the brackets clearly distinguishes coordinated species from counter ions. Avoiding spaces ensures that the primary and secondary valences are represented unambiguously.

❓ Why Other Options Are Incorrect

�� Option A → Roman numerals indicate oxidation state, not formula boundaries.
�� Option C → Counter ions are written outside the coordination sphere.
�� Option D → Letter case does not determine coordination boundaries.

🎯 Strategy

Used

Definition Matching

Application:

�� Identify the formula-writing rule that defines the coordination sphere.

Final Logic:

�� No spaces preserve the boundaries of the coordination entity.

🧠 Memory Trick

Inside Brackets = No Gaps

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Writing Coordination Formulae

📄 Passage

[Cr(NH₃)₃(H₂O)₃]Cl₃ is named as: triamminetriaquachromium(III) chloride. Explanation: The complex ion is inside the square bracket, which is a cation. The ammine ligands are named before the aqua ligands according to alphabetical order. Since there are three chloride ions in the compound, the charge on the complex ion must be +3 (since the compound is electrically neutral). From the charge on the complex ion and the charge on the ligands, we can calculate the oxidation number of the metal. In this example, all the ligands are neutral molecules.

Question:
Based on the passage's explanation, why is 'ammine' placed before 'aqua' in the name triamminetriaquachromium(III) chloride?

A Ammine is a stronger ligand.

B Ammine comes before aqua according to alphabetical order.

C There are more ammine molecules than aqua molecules.

D Ammine determines the oxidation state.

💡 Short Explanation

�� Ligands are named alphabetically. �� Ligand strength is irrelevant. �� Ammine precedes aqua alphabetically.

✅ Correct Answer Explanation

According to IUPAC nomenclature, ligand names are arranged alphabetically before the metal name. The names "ammine" and "aqua" are compared alphabetically. Since "ammine" comes before "aqua", it is written first in the compound name.

❓ Why Other Options Are Incorrect

�� Option A → Ligand strength does not determine naming order.
�� Option C → Both ligands are present in equal numbers.
�� Option D → Oxidation state is independent of ligand order.

🎯 Strategy

Used

Contextual/Tonal Matching

Application:

�� Apply the rule explicitly stated in the passage.

Final Logic:

�� Alphabetical order determines ligand sequence.

🧠 Memory Trick

Ammine Before Aqua

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Alphabetical Order of Ligands

📄 Passage

Question:
According to the passage, how is the oxidation number of the chromium metal (+3) deduced from the formula [Cr(NH₃)₃(H₂O)₃]Cl₃?

A By directly measuring the secondary valence.

B Because the neutral ligands contribute +3 charge.

C From the +3 charge on the complex ion (balanced by three Cl⁻ ions) and the zero charge of the neutral ligands.

D By counting the total number of ligands inside the square brackets.

💡 Short Explanation

�� Three chloride ions indicate a +3 complex charge. �� NH₃ and H₂O are neutral ligands. �� Chromium therefore has oxidation state +3.

✅ Correct Answer Explanation

The three chloride ions outside the coordination sphere contribute a total charge of −3. Therefore, the coordination entity must carry a +3 charge for the compound to remain electrically neutral. Since NH₃ and H₂O are neutral ligands, the entire +3 charge must be contributed by chromium. Hence the oxidation state of chromium is +3.

❓ Why Other Options Are Incorrect

�� Option A → Oxidation state is calculated from charge balance, not measured in this manner.
�� Option B → Neutral ligands contribute zero charge.
�� Option D → Number of ligands does not determine oxidation state.

🎯 Strategy

Used

Substitution

Application:

�� Use charge balance to determine oxidation state.

Final Logic:

�� Complex charge = +3 and ligand charge = 0, therefore Cr = +3.

🧠 Memory Trick

Neutral Ligands → Metal Gives Charge

📚 Class XII – Chemistry Part II – Chapter: Coordination Compounds – Topic: Determination of Oxidation State

CUET UG Chemistry Booster Test – 3 Nomenclature

CUET UG Chemistry Booster Test - 3 Nomenclature

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