NEB Class 12 Science Chemistry Question Paper 2080 (Set A)

Phenol is heated with CHCl₃ and aq. KOH then produce salicylaldehyde. This reaction is called

Which of the following reaction is used to distinguish carboxylic acid with other organic compound?

Silver gets tarnished in air due the reaction with

Lithophone is a mixture of

The correct decreasing order of acidic strength of 0.1 m solution of following acids, is

Another name of grain alcohol is

Primary and secondary amines are distinguished by.

The specific rate constant of 1st order reaction depends on

Calculate number of H⁺ ion present in 1 mL of a solution whose pH = 13.

What will be the value of ΔS for conversion of ice into water when they are in equilibrium? (Δh = 6 KJ/mol)

Find out the volume of water to be added to 20 mL of 2N HCl to make it exactly decinormal.

Give an example of each of the following reaction:

i) Coupling reaction

ii) Hydroboration oxidation

iii) Clemmensen's reduction

iv) Fehling test

v) Carbonylation reaction (1×5=5)

An organic compound (A) having molecular formula C₄H₈O₂ undergoes acid hydrolysis to produce a carboxylic acid (B) and an alcohol (C). When (B) is reduced with LiAlH₄ then the alcohol (C) is produced. (4+1)

i) Draw molecular structure of (A) (B) and (C) with proper reaction.

ii) What products would you expect when (A) is reduced with LiAlH₄?

You are given a bottle containing a mixture of R-NH₂, R₂NH and R₃N. How would you apply Hoffmann's method to separate each compound in pure state? (5)

Describe rusting theory of Iron. Name the process of preventing iron from rusting. (4+1)

i) What is meant by transition metal? (1)

ii) Justify giving proper reason. (1+1)

a) Transition metals mostly form coloured compounds.

b) Zinc is regarded as non-typical transition metal.

iii) Draw splitting of d-orbital in octahedral field showing e₉ set and t₂g set. (2)

An electrochemical cell is connected by using Aluminum (Al) electrode and silver (Ag) electrode whose standard electrode potential value -1.67 V and +0.80V respectively.

i) Write cell notation of an electrochemical cell indicating anode and cathode. (2)

ii) Write down oxidation half and reduction half reaction occurring in the cell. (2)

iii) Calculate e.m.f. of the cell. (1)

Enthalpy of formation of H₂O (l), CO₂ (g) and C₃H₇OH(l) are -286 KJ/mol, -394 KJ/mol and -2010 KJ/mol respectively.

i) What is meant by enthalpy of formation? (1)

ii) Write down balanced thermochemical reactions for each of above process. (1)

iii) Calculate the enthalpy of combustion of C₃H₇OH (l) from the above data. (3)

Or

i) Deduce the relation between pH and pOH at 25°C. (2)

ii) The solubility product of AgCl is 1.8×10⁻¹⁰. What mass of AgCl (Molecular mass = 143.5) will be precipitate if 0.2 mole of HCl solution is added to the saturated solution of AgCl. (3)

Represent a regular sequence of reaction of the following sets of organic compounds using suitable catalysts, reagents or conditions:

$CH_3CH_2CH_2Cl,\ CH_3CH_2NH_2,\ CH_3CH_2CH_2OH,\ CH_3CH_2COOH,\ CH_3CH_2CONH_2$

Or

Formic acid is the first member of carboxylic acid and naturally found ant stings and venom of bee.

i) Draw the molecular formula of formic acid and write its IUPAC name. (1)

ii) How is formic acid prepared from a) chloroform b) ethane-1,2-dioic acid? (1+1)

iii) Distinguish formic acid from acetic acid with a chemical reaction. (1)

iv) Why is formic acid more acidic than acetic acid? (1)

a) Normality factor and titration error are important in analytical chemistry for the determination of variation of the observed result for the same experiment.

i) Distinguish between normality factor and titration error. (2)

ii) A chemistry lab-boy weighed 1.31 gm of Na₂CO₃ to prepare 250 mL of its decinormal solution.

a) Calculate the actual strength of the solution indicating normality factor.

b) Find the volume of water required to be evaporated to make it exactly normal solution.

c) Calculate the mass of oxalic acid crystal required to neutralisation the solution completely. (2+1+2)

iv) How would you apply of titration in pharmaceutical industry? (1)

Or

i) Define half-life period of reaction. (1)

ii) Why is half-life period of first order reaction independent of the initial concentration. (2)

iii) Mention the major application of half life period in biological Scientific research. (1)

iv) A first order reaction is 60% complete in 30 minute. a) Find out the rate constant and half life period. (2) b) Calculate the time required to convert 99% of the reactant into products. (1)

v) Mention an example to show effect of surface area of reactant on rate of reaction. (1)

An alcohol (A) of molecular formula C₃H₈O undergoes Victor Meyer's reaction to give blue colour at the end of reaction when added KOH solution.

i) Draw structural formula and IUPAC name of (A) (1)

ii) Give the complete chemical reaction for the Victor-Meyer's test of (A) (2)

iii) Starting from CH₃MgBr, how would you prepare compound A? (2)

iv) What happens when (A) is oxidised. (1)

v) Convert (A) into propene. (2)

Or

i) Give proper chemical reaction for the preparation of benzaldehyde from a) Benzyl chloride b) Toluene (2)

ii) Convert benzaldehyde into a) Toluene b) cinnamic acid. (2)

[Question 22 of Group 'C' — not fully legible in the provided scan.]