List of top Questions asked in UP Board XII

Which of the following is most acidic?
(I) 4-methoxybenzoic acid (\( -COOH \) with para \( -OCH_3 \))
(II) benzoic acid
(III) 4-nitrobenzoic acid (\( -COOH \) with para \( -NO_2 \))

Which of the following is temperature independent?

The increasing order of reactivity of the following compounds in \( S_N1 \) reaction is:
A. \( (CH_3)_3CBr \)
B. \( CH_3CH_2CH_2CH_2Br \)
C. \( (CH_3)_2CHCH_2Br \)
D. \( CH_3CH(Br)CH_2CH_3 \)

Explain whether the half-life of a first order reaction depends or not on the initial concentration of the reactants.

For which of the following ions is the magnetic moment \( (\mu) \) the highest?

What will be the Nernst equation of the cell for the following reaction?
\( 2Cr(s) + 3Cd^{2+}(aq) \rightarrow 2Cr^{3+}(aq) + 3Cd(s) \)

Reactivity of haloarene increases if an electron withdrawing group (\( -NO_2 \)) is present at the ortho or para position. Explain it with an example and give the reaction mechanism.
OR
Write short notes on the applications of the following: (i) DDT (ii) Freon (iii) Carbon tetrachloride (iv) Chloroform (v) Dichloromethane.

Rate constant \( K \) for a first order reaction is found \( 5.5 \times 10^{-14}\ \text{s}^{-1} \). Calculate the half-life of this reaction.
OR
For the following first order reaction — \( N_2O_5(g) \rightarrow 2NO_2(g) + \tfrac{1}{2}O_2(g) \) — the initial concentration of \( N_2O_5 \) at 318 K was \( 1.24 \times 10^{-2}\ \text{mol L}^{-1} \). After 60 min it became \( 0.20 \times 10^{-2}\ \text{mol L}^{-1} \). Calculate the rate constant at 318 K.

Explain Kohlrausch's law. If \(\Lambda^\circ_m\) for NaCl, HCl and NaAc are 126.4, 425.9 and 91.0 S cm² mol^−1, calculate \(\Lambda^\circ\) for HAc. (4)

Write short notes on the following:
(i) Gabriel phthalimide reaction
(ii) Hoffmann bromamide reaction
OR
Write the following chemical reactions:
(i) Reaction of ethanolic NH₃ with C₂H₅Cl.
(ii) Reaction of ammonia with benzyl chloride, followed by reaction with two moles of CH₃Cl.

Write short notes on the following: (i) Denaturation of proteins (ii) Name and structural formula of bases present in the nucleic acid. (2 + 2)

Explain the crystal field splitting in octahedral complexes with the help of a diagram. (4)

Write the products of the following reactions:
(i) Phenol (C₆H₅OH) + CHCl₃ + aq. NaOH → ?
(ii) Phenol (C₆H₅OH) + Zn / Δ → ?
OR
(i) Explain hydrogen bonding in o-nitrophenol and p-nitrophenol.
(ii) What is formed in the nitration of phenol with concentrated HNO₃?

What is Lanthanoid contraction? Write in increasing order of basic nature of oxides \( (Ln_2O_3) \) and hydroxides \( [Ln(OH)_3] \) of Lanthanoids.

Write short notes on Etard reaction and Gattermann-Koch reaction. (2 + 2)

Write short notes on the following:
(i) Aldol condensation
(ii) Cannizzaro's reaction

What is the colligative property? Write an expression for the determination of molar mass of solute using relative lowering in vapour pressure.

For the following cell reaction, write the half reactions occurring at the anode and cathode and determine the electromotive force (EMF) of the cell:
\( 2Ag^+ + Cd \rightarrow 2Ag + Cd^{2+} \)
(Given, \( E^{\circ}_{Ag^+/Ag} = +0.80\ V \) and \( E^{\circ}_{Cd^{2+}/Cd} = -0.40\ V \))

Write the effect of catalyst on the rate of reaction.

Complete the following chemical reaction:
\( CH_3CH_2CH_2OH \xrightarrow{PBr_3} [A] \xrightarrow[\Delta]{Alc.\ KOH} [B] \)

Represent α-D-(+)-glucopyranose and β-D-(+)-glucopyranose by Haworth structure.

Write the reaction mechanism of the unimolecular nucleophilic substitution (S_N1) reaction of 2-bromo-2-methylpropane.

Write the IUPAC names of the following coordination compounds:
(i) \( [Co(en)_2ClBr]NO_3 \)
(ii) \( [Ni(NH_3)_4][Pt(CN)_4] \)

45 g ethylene glycol is mixed with 600 g H₂O. Calculate the depression of freezing point of this solution. \( (K_f = 1.86\ \text{K kg mol}^{-1}) \)

Transition metals, with a few exceptions, are extremely hard and less volatile. Explain.