Goa Gbshse Class 12 Chemistry — Real Previous-Year Papers

The product formed in Aldol condensation is ........................ . (a) an α, β unsaturated ester (b) an α-hydroxy aldehyde or ketone (c) a β-hydroxy acid (d) a β-hydroxy aldehyde or ketone.

The Kₕ values of Ar(g), CO2(g), HCHO(g) and CH4(g) are 40.39, 1.67, 1.83 × 10⁻⁵ and 0.413 respectively. The correct order of their solubility is... (a) HCHO < CH4 < CO2 < Ar (b) HCHO < CO2 < CH4 < Ar (c) Ar < CO2 < CH4 < HCHO (d) Ar < CH4 < CO2 < HCHO

Write the chemical name of Vitamin C.

Draw the structure of the chromate ion.

Write the structural formula of 2-ethoxy-2-methylpropane.

Define : Activation energy.

Identify the structure of the missing component in the given reaction sequence : Toluene --(conc. HNO3 + conc. H2SO4)--> ? --(Fe/HCl)--> 4-aminotoluene

Draw a neat labelled diagram of the Hydrogen-Oxygen fuel cell by specifying the electrolyte and the electrode material used.

State Faraday's first law of electrolysis. Calculate Λ°m for CaCl2 from the given data : λ°m for Ca+2 = 119.0 S cm2 mol⁻¹ and λ°m for Cl⁻¹ = 76.3 S cm2 mol⁻¹

Write the IUPAC name of each of the following complexes : (i) K3[Al(C2O4)3] (ii) [Cr(NH3)4(H2O)2]Cl3

On the basis of Valence Bond theory, deduce the type of hybridisation and geometry of the high spin complex [CoF6]⁻³. **OR** On the basis of Valence Bond theory, deduce the type of hybridisation and magnetic character of the tetrahedral complex [Ni(CO)4].

Select the correct compound from each of the given pairs. (i) Which halogen compound from the following will undergo SN2 reaction faster ? [Structure: a six-membered ring bearing a –CH2Cl substituent via a double-bond linkage, and a six-membered ring with Cl attached directly to the ring, shown as a pair joined by 'and'] (ii) Which molecule from the given pair is chiral ? CH3CH2CH2CH2Br and CH3CH(Br)CH2CH3

Write one point of difference as specified in each case : (i) Essential amino acids and non-essential amino acids on the basis of their synthesis. (ii) DNA and RNA with respect to the sugar moiety present in them.

Name the following : (i) An element of the 3d series that exhibits maximum number of Oxidation states. (ii) An alloy which consists of 95% lanthanoid metal along with iron and other trace elements.

Identify the structure of the final product 'X' and 'Y' formed in each of the following reactions : (i) C6H5–CH=CH2 --(hydroboration-oxidation)--> 'X' (ii) CH3CH2CH2–OH --(conc. H2SO4 at 413K)--> 'Y'

Write chemical equations for each of the following reactions : (i) Phenol is treated with Bromine water. (ii) Vapours of ethyl alcohol are passed over heated copper at 573 K.

Define azeotropes. State the type of azeotrope formed by a solution exhibiting positive deviation from Raoult's Law.

Identify the structure or name of Compounds 'P' and 'Q' in the following reactions : (i) CH3CH2-CONH2 + Br2 + alcoholic NaOH → Compound 'P' + Na2CO3 + NaBr + H2O (ii) [Structure: a benzene ring with a –SO2Cl group attached] + C2H5–NH2 → Compound 'Q' + HCl

For a reaction, H2 + Cl2 --(hν)--> 2 HCl, the rate law is Rate = k (i) Write the Order of the reaction. (ii) State the Unit of rate constant 'k' for the above reaction.

Half life period of a first order reaction is 693 seconds. Calculate the following : (i) Rate constant 'k'. (ii) Time required for 90% completion of this reaction in minutes.

Identify the Name of the reactions which are illustrated by the following chemical equations : (i) C6H5Br + 2Na + CH3Br → C6H5–CH3 + 2NaBr (ii) C6H5N2(+)Cl⁻ + HCl --Cu2Cl2--> C6H5Cl + N2 (iii) CH3CH2Cl + AgF → CH3CH2F + AgCl

Answer the following : (i) Draw and label the facial (fac–) and meridional (mer-) isomers of [Co(NH3)3(NO2)3]. (ii) Write one point of difference between homoleptic and heteroleptic complexes.

Answer the following : (i) Write the IUPAC name for : [Structure: a benzene ring with an –N(CH3)2 substituent attached] (ii) Name the foul smelling compound obtained when aniline is subjected to Carbylamine Reaction. (iii) State two factors that affect the basic strength of amines.

Name the following : (i) The linkage between two monosaccharide units in carbohydrates. (ii) A nonreducing disaccharide which upon hydrolysis gives equimolar mixture of D(+) glucose and D(-) fructose. (iii) The product obtained when glucose is heated with HI.

An alkene having molecular formula C5H10 upon ozonolysis and further decomposition with zinc and water forms Compound 'B' and Compound 'C' as products. Compound 'B' gives Fehling's test as well as a positive iodoform test. Compound 'C' gives a positive iodoform test and not the Fehling's test. Write the appropriate chemical equation involved in the formation of Compounds B and C from the alkene. Also write the names of Compounds B and C.

With respect to 'd' and 'f' block elements, answer the following : (i) Predict which of the following ions will be coloured in aqueous solution ? Cr3+, Zn2+, Cu1+, Ni2+ (ii) Write the complete ionic equation for the oxidising action of acidified permanganate ions on ferrous ions. (iii) State the reason : Actinoid contraction is greater from element to element than Lanthanoid contraction. **OR** With respect to 'd' and 'f' block elements, answer the following : (i) Predict which of the following ions will exhibit magnetic moment ? Sc3+, Fe2+, Ti4+, Co2+ (ii) Write the complete ionic equation for the conversion of dichromate ion into chromate ion. (iii) State the reason : Zirconium and Hafnium have similar atomic radii.

With respect to Solutions, answer the following : (i) Draw a neat labelled graph to represent the dependence of Vapour pressure on mole fraction of a component of a binary solution exhibiting ideal behaviour. (ii) Calculate the Osmotic pressure of a 5% (w/v) solution of urea (molar mass 60) at 27ºC. (Given : R = 0.083 litre bar K⁻¹mol⁻¹) **OR** With respect to Solutions, answer the following : (i) Draw a neat labelled graph to represent the elevation in boiling point of a solvent upon the addition of a non-volatile solute. (ii) Calculate the mole fraction of KI in an aqueous solution containing 20% of KI by mass. (Given : At. mass of K = 39, I = 127, H = 1, O = 16)

On the basis of the given data, answer the questions below : A galvanic cell is set up at 25ºC with the following half cells. Ag1+(10⁻³ M)/Ag(s) and Cu2+ (10⁻¹ M)/Cu(s) (Given : E° Ag1+/Ag = 0.80 V, E°Cu2+/Cu = 0.34 V) (i) Write the net cell reaction taking place in this cell. (ii) Is it possible to store a solution of Copper sulphate in a silver vessel ? (iii) Calculate Ecell at the given concentrations. (Consider the value of 2.303RT/F as 0.06 in the calculation) **OR** On the basis of the given half reactions, answer the questions below : Al3+(aq) + 3e⁻ → Al(s) ............... E° = − 1.66V Ni2+(aq) + 2e⁻ → Ni(s) ............... E° = − 0.25 V (i) Represent an electrochemical cell using Nickel and Aluminium electrodes as per cell conventions. (ii) Among Ni and Al, which is a better reducing agent ? (iii) Calculate the equilibrium constant (Kc) for the cell reaction. (Consider the value of 2.303RT/F as 0.06 in the calculation)

Answer the following : (i) Select the carboxylic acid from the following having the highest acid strength : 4-nitrobenzoic acid, benzoic acid, 4-methoxybenzoic acid (ii) Write the chemical equation for the preparation of an oxime from acetaldehyde. (iii) Identify the reagent/s and the final product in each of the following Name reactions : (a) Etard Reaction with methylbenzene. (b) Clemmensen reduction of acetone. **OR** Answer the following : (i) Select a compound that is most reactive towards nucleophilic addition reaction from the following : Acetone, acetaldehyde, propionaldehyde. (ii) Write the chemical equation involved when Sodium acetate is heated with sodalime. (iii) Identify the reagent/s and the main reactant in each of the following Name reactions : (a) Preparation of acetophenone by Friedel Craft's acylation. (b) Preparation of α-bromopropanoic acid by Hell Volhard Zelinsky Reaction.