CBSE Class 12 Chemistry — Long Answer Questions

(a) (i) An organic compound (X) has the molecular formula $C_5H_{10}O$. Draw structures for (X) if it: (3 + 2) (I) does not give Tollen's test but gives a positive iodoform test. (II) does not give Tollen's test and iodoform test but undergoes Aldol condensation. (III) undergoes Cannizzaro's reaction. (ii) Show how each of the following compounds can be converted to benzoic acid: (I) Acetophenone (II) Ethyl benzene OR (b) Answer the following questions: $(5 \times 1)$ (i) Draw structure of the 2, 4-dinitrophenyl hydrazone derivative of benzaldehyde. (ii) Arrange the following in increasing order of their reactivity towards HCN: Di-tert. butyl ketone, Acetaldehyde, Acetone (iii) Give a simple chemical test to distinguish between benzoic acid and ethyl benzoate. (iv) Write the name of the reagent to convert Ethanenitrile to Ethanal. (v) Draw the structure of 'X' in the following reaction: Cyclohexanol —($CrO_3$)→ 'X'

(a) (i) From the given data of E° values, answer the following questions: (3 + 2) $E^\circ(M^{2+}/M)$ values (V): $V = -1.18, Cr = -0.91, Mn = -1.18, Fe = -0.44, Co = -0.28, Ni = -0.25, Cu = +0.34$ (I) Why $E^\circ(M^{2+}/M)$ show irregular trend in the above values? (II) Why is $E^\circ(Cu^{2+}/Cu)$ value exceptionally positive? (III) Why $E^\circ(Mn^{2+}/Mn)$ value is highly negative? (ii) Write the ionic equations for the oxidising action of potassium permanganate for its reaction with $I^-$ in both acidic and alkaline solutions. OR (b) Answer the following questions: (1 + 1 + 1 + 2) (i) Name a member of the lanthanoid series (I) which exhibits +4 oxidation state (II) which exhibits +2 oxidation state. (ii) Why transition metals act as good catalyst? (iii) Why Cr has higher melting point than Mn? (iv) What happens when acidic solution of potassium permanganate is allowed to stand for sometime? Give the equation involved. What is this type of reaction called?

(a) Calculate emf and $\Delta G$ for the following cell at 298 K: $Mg(s) / Mg^{2+}(0.01\text{ M}) // Ag^+(0.001\text{ M}) / Ag(s)$ Given: $E^\circ(Mg^{2+}/Mg) = -2.37 \text{ V}$, $E^\circ(Ag^+/Ag) = +0.80 \text{ V}$ [$1F = 96500 \text{ C mol}^{-1}$, $\log 10 = 1$] OR (b) For the reaction: $2AgCl(s) + H_2(g) (0.4\text{ atm}) \to 2Ag(s) + 2H^+(0.1\text{ M}) + 2Cl^-(0.2\text{ M})$ Calculate emf of the cell at 25 °C. Given: $\Delta G^\circ = -43500 \text{ J mol}^{-1}$ [$\log 10 = 1$, $1F = 96500 \text{ C mol}^{-1}$]