Sub. code 3021
NEB — GRADE XII
2079
Old Question
Chemistry Question Paper 2079 (Old Question)
The candidates are required to give their answers in their own words as far as practicable. The figures in the margin indicate full marks.
Pass Marks : 32
सबै प्रश्नको उत्तर दिनुहोस् । (Attempt All Questions)
This old question question paper is for Class 12 Chemistry, 2079 (subject code 3021), carrying full marks of 75 with a pass mark of 32, to be completed within 3hrs. Answers with step-by-step solutions are available for every question below.
Group A
Rewrite the correct answer of each question in your answer sheet
is an example of:
acidic nature of alcohol
basic nature of alcohol
electrophilic substitution reaction
nucleophilic substitution reaction
C₆H₅CH₂CHO and C₆H₅CHO can be distinguished by:
Iodoform test
Tollen's test
2,4-DNP test
Fehling test
An organic compound (X) undergoes reduction with LiAlH₄ to yield (Y). When vapour of Y is passed over freshly reduced copper at 300°C, (X) is formed. The compound Y is:
CH₃CHO
CH₃CH₂OH
CH₃COCH₃
CH₃OCH₃
The number of possible structural isomers of 1° amines of molecular formula C₄H₁₁N is:
1
2
3
4
Acetic anhydride is obtained from acetyl chloride by the reaction of:
Conc. H₂SO₄
P₂O₅
CH₃COONa
CH₃COOH
A metal (M) forms thiosulphate with molecular formula M₂S₂O₃. The valency of metal is:
1
2
3
4
The pH of 10⁻⁸ M aqueous solution of HCl is:
less than 7
7
8
more than 8
A catalyst accelerates the reaction because:
it brings reactants closer
it lowers the activation energy
it increases the activation energy
it forms complex with the reaction
What is the concentration of nitrate ions if equal volume of 1 M NaNO₃ and 1 M KCl are mixed?
0.25 M
0.5 M
1 M
2 M
Tailing of mercury is due to the formation of:
HgO
Hg₂O
HgO₂
Hg₂O₂
Bell metal is an alloy of:
Cu, Pb and Sn
Sn and Cu
Zn and Pb
Zn, Cu and Sn
Group B
short answer question
An electrochemical cell is constructed by using aluminum and silver electrodes whose electrode potential values are:
What is meant by electrochemical cell?
Represent an electrochemical cell using above electrodes.
Write down complete cell reactions.
Calculate the emf of the cell.
Hess's law is applied to calculate the different types of enthalpy of reactions.
Define Hess's law of constant heat summation.
What is meant by enthalpy of reaction?
Standard enthalpy of formation of H₂O₂(l) and H₂O(l) are −188 kJ/mol and −286 kJ/mol respectively. What will be the enthalpy change of the following reaction?
2H₂O₂(l) → 2H₂O(l) + O₂(g)
Ionic product of water at 25°C is 1 × 10⁻¹⁴ and water is regarded as very weak electrolyte.
Define ionic product of water.
Deduce the relation:
Calculate the [OH⁻] concentration of 0.01 M HCl at 25°C.
What is the effect of temperature on ionic product of water?
Ethyl alcohol is common alcohol and is used to manufacture alcoholic beverage. It can be prepared from sugar containing materials like molasses by fermentation process.
Define fermentation.
What is meant by molasses?
Mention the function of yeast in the fermentation of ethyl alcohol.
Write chemical reaction for the conversion of cane-sugar into ethyl alcohol.
Give a difference between absolute alcohol and denatured alcohol.
A carbonyl compound (M) contains three carbon atoms and it undergoes iodoform test.
Identify the compound (M).
Write a chemical reaction for the preparation of (M).
How is (M) converted into propane?
Predict the final product when (M) is treated with in dry ether followed by hydrolysis.
Give a laboratory test reaction of carbonyl compound.
Convert ethoxy ethane from a halo alkane C₂H₅Br by using Williamson's reaction.
What product is obtained when ethoxyethane is heated with excess HI?
Why are old samples of ether not distilled to dryness in air?
Convert phenol into anisole.
For the following reaction sequence.
Write down reagents and conditions for reaction (1), reaction (2), reaction (3) and reaction (4).
Identify the compound (Z) giving IUPAC name.
How would you apply Hoffmann's method for the separation of 1°, 2° and 3° amine from their mixture?
An important compound of non-typical transition metal zinc, which is used as eye lotion and is also called white vitriol.
Write down a method of preparation of white vitriol.
What happens when white vitriol is heated to 800°C?
Define double salt with an example.
How is lithopone obtained from white vitriol?
Why is zinc considered a non-typical transition metal?
Steel manufactured by Open Hearth process.
What is Open Hearth process?
Write down the chemical reactions occurring in Open-Hearth furnace.
Why is Spiegeleisen added in the Open-Hearth furnace?
Write down the composition of stainless steel.
Group C
long answer question
Write an example of each of the following reactions.
Hydroboration oxidation
Decarbonylation
Sandmeyer's reaction
Iodoform reaction
Elimination reaction
Cannizzaro's reaction
Reimer-Tiemann reaction
Friedel-Craft alkylation
An unsaturated hydrocarbon (C₃H₆) undergoes Markovnikov's rule to give (A). Compound (A) is hydrolysed with aqueous alkali to yield (B). When (B) is treated with PBr₃, compound (C) is produced. (C) reacts with AgCN (alc.) to give another compound (D). The compound (D), if reduced with LiAlH₄, produces (E).
Define Markovnikov's rule.
Identify (A), (B), (C), (D) and (E) with chemical reaction.
How does E react with nitrous acid?
How would you convert (B) into C₃H₈?
For a hypothetical chemical reaction:
mP + nQ → Z
The rate law is:
Rate = K[P]ᵐ[Q]ⁿ
Where K is the rate constant of the reaction. (m + n) is the overall order.
Define rate law.
Why is rate law an experimental parameter?
What is meant by rate constant?
Difference between order and molecularity of a reaction
For the above reaction, the order of reaction with respect to P and Q are first order and zero order respectively. Experimental data obtained from the reactions are as below:
Expt. | [P] M | [Q] M | Initial rate (M sec⁻¹) |
|---|---|---|---|
I | 0.1 | 0.1 | 2 × 10⁻² |
II | (A) | 0.2 | 4 × 10⁻² |
III | 0.4 | 0.4 | (C) |
IV | (B) | 0.2 | 2 × 10⁻² |
Identify the value of A, B and C.
Calculate rate constant [k]
Crystal of oxalic acid is generally used to prepare primary standard solution.
Define primary standard solution.
Which chemical indicator is used in the titration of KMnO₄ solution versus oxalic acid solution?
Why is oxalic acid solution warmed after adding dilute H₂SO₄ before titrating with KMnO₄?
Mention a major application of titration in quality control laboratory.
An aqueous solution of a dibasic acid containing 17.7 gram of acid per litre of the solution has density 1.0077 gm/litre (molar mass of the acid = 118 gm/mol). Calculate:
Molarity
Molality
What is Portland cement?
Name the major components present in Portland cement.
Why is gypsum used in clinker during cement production process?
Give any two instruments used for the quality control of cement.
Differentiate between homo-polymer and co-polymer giving an example of each.
Name the monomers of the following polymer and also write their molecular formula:
a) Polystyrene
b) Bakelite
Paper Overview & Analysis
2079
Year
Old Question
Type
75
Full Marks
32
Pass Marks
3hrs
Duration
77
Question Items
Question Type Breakdown
Group Breakdown