List of top Questions asked in UP Board XII

Write the structure of (A), (B) and (C) in the following reaction: phenol (C₆H₅OH) with concentrated HNO₃ gives (C); phenol with dilute HNO₃ gives (A) + (B).

What happens when aniline reacts with the following?
i) Bromine water
ii) (CH₃CO)₂O / Pyridine
iii) HNO₂ + HCl (0°-5°C)

Write the structure of (A), (B) and (C) in the following reaction:
\[ C_6H_5NO_2 \xrightarrow{Fe/HCl} (A) \xrightarrow{NaNO_2 + HCl,\ 273\,K} (B) \xrightarrow{H_2O/H^+,\ \Delta} (C) \]

i) Write the electronic configuration of an element with atomic number 24.
ii) Find the number of unpaired electrons in the Co²⁺ ion.
iii) Why is the range of oxidation states in the actinoid series greater than in the lanthanoid series?

Write the mechanism of the bimolecular nucleophilic substitution reaction (S_N2) of an alkyl halide.

Why do the transition metals and many of their compounds act as catalysts? Explain.

\( [NiCl_4]^{2-} \) is paramagnetic, while \( [Ni(CO)_4] \) is diamagnetic although both are tetrahedral. Why?

Define electrode potential and emf of a cell.

What is the van't Hoff factor? Write the equation for colligative properties including the van't Hoff factor.

Give the IUPAC names of the following organic compounds:
i) \( CH_3-CH_2-CO-CH_2-CH(CH_3)-CH_3 \)
ii) \( C_6H_5-CH=CH-CHO \)

Which of the following is temperature independent?

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 \( -NO_2 \))

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?

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.

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?

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

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) Denaturation of proteins (ii) Name and structural formula of bases present in the nucleic acid. (2 + 2)

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.

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 \( E^{\circ}_{Cd^{2+}/Cd} = -0.40\ V \))

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

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