Sub. code 3021
NEB — GRADE XII
2082
Old Question
Class 12 Chemistry Old Question 2082
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 paper is for Class 12 Chemistry, 2082 (subject code 3021), carrying full marks of 75 with a pass mark of 32, to be completed within 3 Hours. Model answers are available for questions that have one — reveal them with a free account (a few reveals) or a paid plan (unlimited).
Group A
Rewrite the correct option of each question in your answer sheet
To estimate the chloride ion present in tap water, volumetric analysis has been commonly used in the laboratory. Which of the following solutions can be used for the above mentioned titration?
BaCl2
NaOH
KCrO
AgNO
The half-life of a certain reaction is 50 seconds, and it remains constant even if the initial concentration of the reaction is doubled. What is the order of the reaction?
Zero-order reaction
First-order reaction
Second-order reaction
Pseudo-first order reaction
Gibbs-Helmholtz equation is represented as . For what value of will the reaction be spontaneous?
Positive
Zero
Negative
Infinite
Standard reduction potential values for P, Q, R and S are +0.34 V, -0.76 V, +0.0 V and -3.05 V, respectively. What is the correct order of their reducing power?
P > R > Q > S
S > R > Q > P
Q > P > S > R
S > Q > R > P
A deep blue complex is formed when conc. ammonium hydroxide is added to an aqueous solution of CuSO. Which of the following formulae represents the complex?
Which of the following is the maximum possible oxidation state of the transition metals in the 3d series?
+3
+6
+7
+8
Which of the following are organometallic compounds?
i) CHMgI
ii) Ni(CO)
iii) CHLi
iv) CHONa
v) (C₄H₉)₂SnCl₂
i)and ii) only
i), ii) and iii) only
i), ii), iii) and iv) only
i), ii), iii) and v) only
The organic compound (X) boiled with water gives phenol. What is the compound (X)?
Chlorobenzene
Benzenediazonium chloride
Benzenesulphonic acid
Aniline
Which of the following compounds gives a positive carbylamine reaction?
A compound 'Z' with molecular formula C₃H₄O₄ is heated to produce compound 'Y' and CO₂ gas. Heating of 'Y' with P₂O₅ forms compound 'X' and a water molecule. Identify the compound 'X'.
Ethanoic acid
Ethanoic anhydride
Methanoic anhydride
Ethanal
A sequence of reactions is represented as:
Benzene (A) (B) (C)
Predict the name of the reaction that converts (B) to (C).
Benzoin condensation
Perkin’s condensation
Aldol condensation
Claisen condensation
Group B
Short answer question
Define instantaneous rate of reaction. Write down the rate expressions of the following reaction.
2N₂O₅(g) → 4NO₂(g) + O₂(g)
If 2.24 litres of O₂ at NTP is produced in 30 minutes, what is the rate of disappearance of N₂O₅(g)?
Define standard heat of formation. Calculate the heat of formation of acetic acid from the following data:
C(s) + O₂(g) → CO₂(g), ΔH = −99 kcal/mol
H₂(g) + 1/2 O₂(g) → H₂O(l), ΔH = −68 kcal/mol
CH₃COOH(l) + 2O₂(g) → 2CO₂(g) + 2H₂O(l), ΔH = −208 kcal/mol
You are given the standard reduction potentials:
E°(Zn²⁺/Zn) = −0.76 V
E°(Mg²⁺/Mg) = −2.38 V
Answer the following questions:
What is the standard electrode potential?
Construct the galvanic cell notation for the given electrodes, indicating the anode and cathode.
Write the complete cell reaction for the given cell.
Calculate the cell potential for the given cell at 25°C.
A chemical reaction occurs as follows:
CH₂CH₂CH₂Br + KOH(aq.) → B + KBr
Identify the compound ‘B’ in the above reaction.
Which substitution reaction mechanism occurs in the above reaction and why?
What is the product formed when alc. KOH solution is used instead of aq. KOH in the above reaction?
How can you obtain nitropropane from compound ‘A’?
A list of compounds is given as follows:
P-aminoazobenze, Benzenediazonium chloride, Aniline, Nitrobenzene, Phenol and Benzene
From the above list of compounds, prepare a sequence of reaction chain with suitable conditions and reagents.
Write the chemical equations to illustrate the following reactions:
2,4-DNP test
Reimer-Tiemann Reaction
Williamson's Reaction
Perkin Condensation reaction
Wurtz-Fitting reaction
An aliphatic compound (A) reacts with SOCI to give (B). The compound (B) is heated with ammonia to produce (C). The compound (C) is further heated with Br /KOH to yield (D). The compound (D) gives (E) when treated with NaNO /HCI at low temperature. The compound (E) is a primary alcohol which gives positive iodoform test. Identify compounds (A) to (E) with the reactions involved.
You are given the mixture of two compounds A and B.
A = CH₃CH₂CH₂NH₂ and B = CH₃CH₂NHCH₃
How would you separate their mixture by applying Hoffmann’s method? Give the nitrous acid test to distinguish between compounds A and B.
The metal ‘M’ with electronic configuration [Ar] 3d¹⁰4s² belongs to group IIB in the periodic table and is commonly called ‘Jasta’.
Identify metal ‘M’ and write its main ore
Metal (M) = Zinc (Zn)
main ore = Zinc Blende (ZnS)
Why is metal ‘M’ not considered a transition element?
Draw the vertical retort. Write its reduction reaction.
What happens when metal ‘M’ is exposed to air for a long time?
What is rusting? Describe the electrochemical theory of the rusting of iron. List any two methods for the prevention of rusting
Group C
Long answer question
Deduce the normality equation, N₁V₁ = N₂V₂.
Experimental data obtained by titrating a decinormal solution of oxalic acid with potassium permanganate solution are given below.
S.N | Vol. of oxalic acid taken (ml) | Burette reading (ml) (KMnO₄) — Initial reading | Final reading |
|---|---|---|---|
1. | 10 | 0.0 | 11.5 |
2. | 10 | 0.0 | 11.0 |
3. | 10 | 0.0 | 11.0 |
Name the above titration.
Calculate the equivalent weight of KMnO4 .
Calculate the normality of KMnO4 from the above data.
Why is dil. H₂SO₄ added to the conical flask containing standard oxalic acid before titrating with KMnO₄ solution?
Identify the titrant and titrand in this titration.
Write the applications of the solubility product principle and the common ion effect in qualitative salt analysis.
Differentiate between the Bronsted–Lowry and Lewis concepts of bases.
Calculate the degree of ionization of HCN having concentration 0.01 M (Kₐ of HCN = 4.8 × 10⁻¹⁰). Also, calculate the H⁺ concentration and pH of the solution.
An organic compound (X) reacts with Grignard’s reagent to give (Y), which on oxidation gives (Z). All of the compounds (X), (Y) and (Z) give a positive iodoform test.
Identify the compounds (X), (Y) and (Z) with reactions and conditions involved.
Why do these compounds give a positive iodoform test?
How would you convert compound (Y) into pseudonitrol?
Write any two methods for the preparation of compound (Z).
How will you carry out the following conversions?
Ethanol to chloroform
Phenol into DDT
Ethoxyethane into methoxymethane
Aniline into chlorobenzene
Answer the following questions:
What are the raw materials for the production of paper?
Draw the flow sheet diagram for the manufacture of Portland cement.
Nuclear fusion reaction is also called a thermonuclear reaction. Why?
How are addition and condensation polymers formed? Give an example.
Paper Overview & Analysis
2082
Year
Old Question
Type
75
Full Marks
32
Pass Marks
3 Hours
Duration
55
Question Items
Question Type Breakdown
Group Breakdown
Chapter Breakdown
| Amines | 4 items | 13 marks |
| Chemical Kinetics | 2 items | 6 marks |
| Thermodynamics | 2 items | — |
| Transition Metals | 2 items | 1 mark |
| Haloarenes | 2 items | 3 marks |
| Carboxylic Acid and its Derivatives | 2 items | 6 marks |
| Volumetric Analysis | 1 item | 1 mark |
| Electrochemistry | 1 item | 1 mark |
| Organometallic Compounds | 1 item | 1 mark |
| Aldehydes and Ketones | 1 item | 1 mark |
| Study of Heavy Metals | 1 item | — |
| Alcohols | 1 item | 2 marks |
| Ethers | 1 item | 2 marks |
| Paper and Pulp | 1 item | 2 marks |
| Cement | 1 item | 2 marks |
| Nuclear chemistry and application of radioactivity | 1 item | 2 marks |
| Chemistry in the Service of Mankind | 1 item | 2 marks |
Chapter breakdown covers 25 of 55 question items on this paper — the rest aren't tagged to a chapter yet.