UP Board Class 12 Chemistry Question Paper 2024 (Code 347 GB) Available- Download Here with Solution PDF

Moles of water can be calculated using: \[ Moles = \frac{Mass}{Molar mass} = \frac{180}{18} = 10. \] Quick Tip: To calculate moles, divide the given mass of the substance by its molar mass.

The SI unit of resistivity (\( \rho \)) is \( \Omega \, m \), which is derived from: \[ \rho = R \cdot \frac{A}{l}, \]
where \( R \) is resistance, \( A \) is cross-sectional area, and \( l \) is length. Quick Tip: Resistivity depends on the material and is measured in \( \Omega \, m \).

For a second-order reaction, the rate law is: \[ Rate = k[A][B]. \]
The unit of \( k \) is: \[ \frac{Rate}{Concentration^2} = \frac{mol litre^{-1} second^{-1}}{(mol litre^{-1})^2} = litre mol^{-1} second^{-1}. \] Quick Tip: The unit of the rate constant depends on the order of the reaction.

The \( C_2O_4^{2-} \) (oxalate) ligand is bidentate, meaning it donates two pairs of electrons to the central metal atom. Since there are three oxalate ligands, the co-ordination number of Cr is: \[ 3 \times 2 = 6. \] Quick Tip: Co-ordination number is the total number of coordinate bonds formed between the central metal and ligands.

The reaction of Grignard reagent (\( RMgX \)) with water produces an alkane: \[ RMgX + H_2O \rightarrow RH + Mg(OH)X. \] Quick Tip: Grignard reagents react with water to produce hydrocarbons and metal hydroxides.

A \( 2^\circ \) (secondary) amine has two alkyl or aryl groups attached to the nitrogen atom along with one hydrogen atom, represented as \( R_2-NH \). Quick Tip: Amines are classified as primary (\( RNH_2 \)), secondary (\( R_2NH \)), or tertiary (\( R_3N \)) based on the number of organic groups attached to nitrogen.

- Molarity (M): The number of moles of solute dissolved in 1 liter of solution. \[ M = \frac{moles of solute}{volume of solution (L)}. \]
Example: A 1 M solution of NaCl contains 1 mole of NaCl in 1 liter of solution.

- Molality (m): The number of moles of solute dissolved in 1 kg of solvent. \[ m = \frac{moles of solute}{mass of solvent (kg)}. \]
Example: A 1 m solution of NaCl contains 1 mole of NaCl in 1 kg of solvent. Quick Tip: Molarity depends on volume (temperature-sensitive), while molality depends on mass (temperature-independent).

The standard electrode potentials are given as: \[ E^\circ_{Fe^{3+}/Fe^{2+}} = 0.771 \, V, \quad E^\circ_{Br_2/Br^-} = 1.09 \, V. \]
Since the reduction potential of \( Br_2/Br^- \) is higher than \( Fe^{3+}/Fe^{2+} \), bromide ions cannot be oxidized by ferric ions. Quick Tip: The species with a higher reduction potential acts as the oxidizing agent.

The velocity (rate) constant \( k \) of a reaction is the proportionality factor in the rate equation: \[ Rate = k[A]^m[B]^n, \]
where \( m \) and \( n \) are the orders of the reaction. \( k \) depends on temperature and the nature of the reactants. Quick Tip: The rate constant increases with temperature, as explained by the Arrhenius equation.

Cerium (\( Ce \)) has an atomic number of 58, with the electronic configuration: \[ [Xe] 4f^1 5d^1 6s^2. \]
The \( +3 \) state is stable due to the removal of outer electrons (\( 6s^2, 5d^1 \)), while the \( +4 \) state achieves a stable \( 4f^0 \) configuration. Quick Tip: The stability of oxidation states in lanthanides depends on electronic configuration and lattice energy.

The co-ordination number is the number of ligand atoms directly bonded to the central atom in a coordination compound. Example: \[ [Co(NH_3)_6]^{3+}, \]
where the co-ordination number of cobalt is 6. Quick Tip: Co-ordination number depends on the number of donor atoms attached to the central metal ion.

- Primary: \( C_6H_5CH_2OH \)
- Secondary: \( C_6H_5CH(OH)CH_3 \)
- Tertiary: \( C_6H_5C(CH_3)_2OH \) Quick Tip: Primary, secondary, and tertiary alcohols differ based on the number of alkyl groups attached to the carbon bonded to the hydroxyl group.

- Increase in boiling point: Higher carbon atoms increase molecular weight and van der Waals forces.
- Decrease in branching: Branching reduces surface area, weakening intermolecular forces. Quick Tip: Boiling point trends in alcohols depend on molecular weight, branching, and intermolecular hydrogen bonding.

RNA (ribonucleic acid) is a nucleic acid involved in protein synthesis. Types:
- \( mRNA \): Carries genetic information from DNA to ribosomes.
- \( tRNA \): Transfers amino acids during translation.
- \( rRNA \): Structural component of ribosomes. Quick Tip: RNA is single-stranded and plays a vital role in gene expression and protein synthesis.

Haloarenes undergo electrophilic substitution due to the resonance effect, which stabilizes the intermediate carbocation. Example: \[ C_6H_5Cl + Cl_2 \xrightarrow{FeCl_3} C_6H_4Cl_2 + HCl. \] Quick Tip: In haloarenes, the halogen group directs electrophilic substitution to ortho and para positions.

- Elimination: Haloalkane reacts with \( alc. \, KOH \) to form an alkene. \[ C_2H_5Br + alc.\,KOH \rightarrow C_2H_4 + HBr. \]

- Substitution: Haloalkane reacts with \( aq. \, KOH \) to form an alcohol. \[ C_2H_5Br + aq.\,KOH \rightarrow C_2H_5OH + KBr. \] Quick Tip: Elimination forms alkenes, while substitution forms alcohols.

(i) Chlorobenzene: \[ C_6H_5Cl + 2NaOH \xrightarrow{\Delta} C_6H_5OH + NaCl. \]

(ii) Aniline: \[ C_6H_5NH_2 + NaNO_2 + HCl \rightarrow C_6H_5N_2^+Cl^- \xrightarrow{H_2O} C_6H_5OH + N_2 + HCl. \]

(iii) Benzene: \[ C_6H_6 + SO_3 \xrightarrow{H_2SO_4} C_6H_5SO_3H \xrightarrow{NaOH, \Delta} C_6H_5ONa \xrightarrow{HCl} C_6H_5OH. \] Quick Tip: Phenol can be prepared by nucleophilic substitution or from diazonium salts.

(i) Rosenmund reduction: \[ RCOCl + H_2 \xrightarrow{Pd/BaSO_4} RCHO. \]


Rosenmund reduction selectively reduces acid chlorides to aldehydes using a poisoned palladium catalyst.


(ii) Stephen reaction: \[ R-CN + 2[H] \xrightarrow{SnCl_2/HCl} R-CHO + NH_3. \]


The Stephen reaction is used to reduce nitriles to aldehydes using stannous chloride (\( SnCl_2 \)) in acidic medium.


(iii) Gattermann-Koch reaction: \[ C_6H_6 + CO + HCl \xrightarrow{AlCl_3/CuCl} C_6H_5CHO. \] Quick Tip: The Gattermann-Koch reaction introduces a formyl group into benzene to produce benzaldehyde.

- Molar Conductivity (\( \Lambda_m \)): It is the conductivity of an electrolyte solution per unit concentration: \[ \Lambda_m = \kappa \cdot \frac{1000}{C}, \]
where \( \kappa \) is the conductivity and \( C \) is the molarity of the solution.

Calculation:
1. Conductivity (\( \kappa \)): \[ \kappa = \frac{Cell constant}{Resistance} = \frac{1.29}{480} = 0.0026875 \, S cm^{-1}. \]
2. Molar conductivity (\( \Lambda_m \)): \[ \Lambda_m = 0.0026875 \cdot \frac{1000}{0.02} = 134.375 \, S cm^2 mol^{-1}. \] Quick Tip: Molar conductivity increases with dilution due to a decrease in interionic attractions.

- First-order Reaction: The rate of reaction depends on the concentration of a single reactant. The rate law is: \[ Rate = k[A]. \]

- Half-life (\( t_{1/2} \)): For a first-order reaction: \[ t_{1/2} = \frac{0.693}{k}. \]

Calculation: \[ t_{1/2} = \frac{0.693}{5.5 \times 10^{-14}} = 1.26 \times 10^{13} \, s. \] Quick Tip: The half-life of a first-order reaction is independent of the initial concentration of the reactant.

- Lanthanide Contraction: A gradual decrease in atomic and ionic radii across the lanthanide series due to poor shielding by 4f electrons.

- Reason for Colour: Transition elements have partially filled d-orbitals. When light falls on them, d-d transitions occur, absorbing certain wavelengths and reflecting others, giving them color. Quick Tip: Lanthanide contraction affects the properties of elements, including ionic radii and electronegativity.

Valence Bond Theory explains bonding in coordination compounds by hybridization of atomic orbitals on the central metal ion:
1. Ligands donate lone pairs to vacant orbitals of the metal ion.
2. Hybrid orbitals form sigma bonds with the ligands.
3. Example: In \( [Ni(CN)_4]^{2-} \), \( Ni^{2+} \) undergoes \( dsp^2 \) hybridization, forming a square planar structure. Quick Tip: VBT explains geometry but cannot predict color or magnetic properties of complexes.

- Raoult’s Law: The relative lowering of vapour pressure is proportional to the mole fraction of the solute: \[ \frac{P^0 - P}{P^0} = x_2 = \frac{n_2}{n_1 + n_2}, \]
where \( P^0 \) is the vapour pressure of the pure solvent, \( P \) is the vapour pressure of the solution, \( n_1 \) and \( n_2 \) are moles of solvent and solute.

Expression for Molar Mass:
For dilute solutions, \( n_2 \ll n_1 \), so: \[ \frac{P^0 - P}{P^0} = \frac{w_2}{M_2} \cdot \frac{M_1}{w_1}. \]
Rearranging: \[ M_2 = \frac{w_2 M_1}{w_1 \cdot \frac{P^0 - P}{P^0}}. \] Quick Tip: Raoult’s law is used to calculate molar mass and study colligative properties.

Depression in Vapour Pressure: \[ \Delta P = P^0 - P = 0.745 - 0.740 = 0.005 \, bar. \]

Relative lowering of vapour pressure: \[ \frac{\Delta P}{P^0} = \frac{n_2}{n_1} = \frac{w_2}{M_2} \cdot \frac{M_1}{w_1}. \]

Given: \[ w_2 = 0.5 \, g, \, w_1 = 39.0 \, g, \, M_1 = 78 \, g mol^{-1}. \]

Substitute values: \[ \frac{0.005}{0.745} = \frac{0.5}{M_2} \cdot \frac{78}{39}. \]

Simplify: \[ M_2 = \frac{0.5 \cdot 78}{0.005 \cdot 39 \cdot 0.745} = 261.86 \, g mol^{-1}. \] Quick Tip: Depression in vapour pressure helps determine molar mass of non-volatile solutes.

(i) Oxidation of primary alcohol: \[ RCH_2OH + [O] \rightarrow RCHO + H_2O. \]

(ii) Rosenmund reduction: \[ RCOCl + H_2 \xrightarrow{Pd/BaSO_4} RCHO. \]

(iii) Stephen reaction: \[ R-CN + 2[H] \xrightarrow{SnCl_2/HCl} RCHO. \]

(iv) Hydrolysis of geminal dihalides: \[ RCHCl_2 + H_2O \rightarrow RCHO + 2HCl. \]

(v) Gattermann-Koch reaction: \[ C_6H_6 + CO + HCl \xrightarrow{AlCl_3} C_6H_5CHO. \] Quick Tip: Aldehydes can be prepared from alcohols, acid chlorides, nitriles, and hydrocarbons.

Mechanism of Nucleophilic Addition Reaction:
Aldehydes and ketones undergo nucleophilic addition reactions due to the presence of a polar carbonyl group (\( C=O \)).

1. Step 1: Nucleophilic attack on the carbonyl carbon: \[ R-C(=O)-R' + Nu^- \rightarrow R-C(O^-)-R'Nu. \]

2. Step 2: Protonation: \[ R-C(O^-)-R'Nu + H^+ \rightarrow R-C(OH)-R'Nu. \]

Example: Reaction of formaldehyde with cyanide ion: \[ HCHO + CN^- \rightarrow H-C(CN)(OH). \]


Nucleophilic addition occurs due to the electrophilic nature of the carbonyl carbon.


Aldol Condensation:
Aldehydes or ketones having at least one \(\alpha\)-hydrogen undergo aldol condensation in the presence of a base: \[ 2CH_3CHO \xrightarrow{Dil. NaOH} CH_3CH(OH)CH_2CHO \xrightarrow{\Delta} CH_3CH=CHCHO + H_2O. \]


Aldol condensation involves the formation of \(\beta\)-hydroxy aldehydes or ketones, followed by dehydration.


Cross Aldol Condensation:
Cross aldol condensation occurs between two different aldehydes or ketones: \[ CH_3CHO + CH_3COCH_3 \xrightarrow{Dil. NaOH} CH_3CH(OH)CH_2COCH_3 \xrightarrow{\Delta} CH_3CH=CHCOCH_3 + H_2O. \] Quick Tip: In cross aldol condensation, products are a mixture of aldols, requiring careful selection of reactants for specificity.

Resonating Structures of Arylamines:
Arylamines, such as aniline (\( C_6H_5NH_2 \)), exhibit resonance due to the delocalization of the lone pair of electrons on the nitrogen atom into the benzene ring.
\[ Structure 1: \quad {C6H5NH2} \quad \rightarrow \quad Structures showing delocalized electrons. \]

Basic Properties:
Arylamines are basic because the lone pair of electrons on the nitrogen atom can accept a proton (\( H^+ \)). However, resonance decreases the availability of the lone pair, making them less basic than aliphatic amines.

Preparation of Amines:
1. From Nitro Compounds: \[ {RNO2 + 6[H] -> RNH2 + 2H2O} \quad (Reduction with Sn/HCl or catalytic hydrogenation). \]

2. From Nitriles: \[ {RCN + 2[H] -> RCH2NH2} \quad (Reduction with LiAlH4). \] Quick Tip: Arylamines are less basic than aliphatic amines due to resonance, which delocalizes the lone pair on nitrogen.

(i) Gabriel Phthalimide Synthesis: \[ {C6H4(CO)2N + KOH -> C6H4(CO)2NK + RX -> C6H4(CO)2NR -> RNH2}. \]

(ii) Hoffmann Bromamide Reaction: \[ {RCONH2 + Br2 + 4NaOH -> RNH2 + Na2CO3 + 2NaBr + 2H2O}. \]

(iii) Carbylamine Reaction: \[ {RNH2 + CHCl3 + 3KOH -> RNC + 3KCl + 3H2O}. \]

(iv) Coupling Reaction of Benzene Diazonium Chloride with Phenol and Aniline:
1. With Phenol: \[ {C6H5N2+Cl- + C6H5OH -> C6H5N=NC6H4OH}. \]

2. With Aniline: \[ {C6H5N2+Cl- + C6H5NH2 -> C6H5N=NC6H4NH2}. \] Quick Tip: The Gabriel synthesis is used for primary amines, Hoffmann reaction for amides, and carbylamine reaction for isocyanides.

Nucleic acids are biopolymers made of nucleotide monomers. Each nucleotide consists of:
1. A nitrogenous base (adenine, thymine/uracil, guanine, cytosine).
2. A pentose sugar (ribose in RNA, deoxyribose in DNA).
3. A phosphate group.

- DNA stores genetic information, and RNA helps in protein synthesis.
- DNA is double-stranded with complementary base pairing (\( A-T \), \( G-C \)), while RNA is single-stranded.

Biological Action:
- DNA replication ensures the transfer of genetic information.
- RNA facilitates transcription and translation processes for protein synthesis. Quick Tip: DNA stores genetic information, while RNA plays a key role in protein synthesis.