Sub. code 3021
NEB — GRADE XII
2078
Model Question
Class 12 Chemistry Model Question 2078
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 model question paper is for Class 12 Chemistry, 2078 (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 answer in your answer sheet
What is the equivalent weight of H₃PO₃ in the reaction?
2 NaOH + H₃PO₃ ⟶ Na₂HPO₃ + 2 H₂O
2M
M
M/2
M/3
The solubility product of chalk is 9.3 × 10⁻⁸. What is its solubility in gram per liter?
3.04 × 10⁻¹
3.04 × 10⁻²
3.04 × 10⁻³
3.04 × 10⁻⁴
What is the concentration of NO₂ in the following first order reaction in which the rate is 2.4 × 10⁻⁵ mole L⁻¹ and rate constant is 3.0 × 10⁻⁵ s⁻¹?
2 NO₂ ⟶ 4 NO₂ + O₂
0.04
0.8
1.2
1.4
What happens when the lead storage battery is discharged?
SO₂ is evolved
PbSO₄ is consumed
Lead is formed
H₂SO₄ is consumed
What is general electronic configuration of transition metal?
(n−1)s²pd⁶d¹⁰ns⁰2
(n−1)s²p⁶ns²np¹
(n−1)s²p⁶d⁵ns¹
(n−1)d¹–¹⁰ns¹–²
Which of the following ore is concentrated by froth-flotation process?
Hematite
Siderite
Galena
Malachite
Which of the following products is obtained when nitrobenzene is electrolytically reduced?
p-aminophenol
azobenzene
azoxybenzene
hydrazobenzene
Which of the following compound is π-bonded organo-metallic compound which has ethene as one of the components and is the first synthesized organometallic compound?
Zeise’s salt
Ferrocene
Di-benzene chromium
Tetraethyl tin
What effect does calcium sulphate have on cement?
Retards setting action
Acts as flux
Imparts color
Reduces strength
Removal of which of the following leads to higher fiber-fiber bonding strength in paper?
Softwood
Hardwood
Lignin
Pulp
In the figure given below which one is correct?
Alpha rays deviate towards A, beta rays deviate towards C and gamma rays direct towards B.
Alpha rays direct towards B, beta rays deviate towards C and gamma rays towards A.
Alpha rays deviate towards C, beta rays direct towards B and gamma rays towards A.
Alpha rays deviate towards C, beta rays deviate towards A and gamma rays direct towards B.
Group B
Short answer question
Standard solution of Na₂CO₃ is used to determine the strength of H₂SO₄ during titration.
How is the completion of the reaction in this titration detected? Is the solution prepared from Na₂CO₃ primary standard? Why?
2.16 g of pure Na₂CO₃ is added to 400 mL deci-normal solution of H₂SO₄. How many grams of H₂SO₄ is further required to neutralize the resultant solution completely?
Derive the relation
k = log
Show that for the first order reaction the time required for half the change (half-life period) is independent of the initial concentration
A first order reaction is 50% completed in 10 second. How much time would it take for 90% completion?
Study the following data for the thermodynamic process H₂O(l) ⟶ H₂O(s) at different temperatures and at 1 atmospheric pressure.
Condition | Temperature | Entropy of system (J K⁻¹ mol⁻¹) | Entropy of surrounding |
|---|---|---|---|
1 | −1°C | −25.68 | +25.72 |
2 | 0°C | −26.55 | +26.88 |
3 | +1°C | −27.62 | +27.42 |
Calculate the total entropy of the universe at given condition 3.
Can we predict the spontaneity of the given reaction at 0°C?
Calculate the equilibrium constant for the fusion of ice at 1°C. What is the effect of temperature for the entropy change of reaction?
The figure shows the octahedral distortion of d-block orbital in the presence of ligand.
Why does octahedral distortion occur in the presence of ligand? Explain on the basis of CFT.
On the basis of the given distortion, how can you explain [Cu(H₂O)₆]²⁺ is blue colored complex?
Out of Fe³⁺ and Fe²⁺ which one is more stable? Explain on the basis of distortion seen in above figure
Why do such elements which give such splitting show good catalytic properties?
X is an ore of a metal M. X on calcination gives black precipitate (W) of metal oxide which belongs to group II of basic radicals in qualitative analysis. X on roasting gives the metal (M) and a gas as major byproduct. The gas when passed through an acidified K₂Cr₂O₇ solution turns green.
Identify the metal M.
Write the reaction involved during calcination of X.
Write the action of the gas on acidified K₂Cr₂O₇.
Convert metal X into its vitriol.
The given table shows the compounds and their molecular formula. How can you convert P to Q, where Q is a compound in which two methyl groups are substituted at adjacent carbons? How is P obtained from T, where T is secondary alcohol? Write the reactions involved in the conversion of P into R and S?
Compounds — Molecular formula
P — C₃H₇Br
Q — C₆H₁₄
R — CH₂O
S — C₂H₄O
T — C₃H₈O
An aromatic compound (A) in which one chlorine atom is substituted at benzene ring. When the compound (A) is heated with 2,2,2-trichloroethanal in presence of conc. H₂SO₄ gives an insecticide (B). The compound (A) when treated with an acid chloride containing two carbon atoms in the presence of anhydrous AlCl₃ gives (C).
How would you obtain compound A from benzene diazonium chloride?
Identify B and C.
Reaction of aq. NaOH on the compound (A) is more difficult than with chloroethane, justify with a suitable explanation.
A list of compounds is given as follows:
p-hydroxyazobenzene, C₆H₅NCl, C₆H₅NH₂, C₆H₅NO₂, C₆H₆
From the above list of compounds, prepare a sequence of reaction chain with suitable conditions and reactions.
Write down the isomeric alcohols of C₃H₈O and their IUPAC name. How would you apply Victor Meyer’s test to distinguish these isomers?
Define condensation polymerization. Write the molecular structures of monomers of Bakelite.
Differentiate between OPC and PPC cement.
Group C
Long Answer Questions
What amount of Zn(OH)₂ will be precipitated out at 25°C if 100 mL of 0.22 g NaOH is added to 1 litre of a saturated solution of Zn(OH)₂? Precipitate is obtained in this reaction, why? [Solubility product of Zn(OH)₂ at 25°C is 1.8 × 10⁻¹⁴]
Potassium hydroxide having pH 8 is diluted 1000 times. Calculate the pH of the diluted base
Calculate heat of formation of ethyl alcohol from the given data.
Heat of combustion of ethyl alcohol = −330 Kcal
Heat of formation of carbondioxide = −94 Kcal
Heat of formation of water = −68.5 Kcal
The standard electrode potential of the following electrode reaction at standard state is given.
Cu(s) ⟶ Cu²⁺(aq) + 2e⁻,................... E°Cu²⁺/Cu = +0.34V
Ag⁺(aq) + e⁻ ⟶ Ag(s),........................ E°Ag⁺/Ag = +0.80V
Write the cell notation indicating anode and cathode.
With 1M solution of ion at 25°C and 1atm. pressure, what will be the cell potential?
Will silver nitrate solution act in a copper vessel?
Can we store AgNO₃ solution in a copper vessel?
A primary alcohol of molecular weight 46 is boiled with sodium hydroxide and iodine. When the same alcohol is heated with ethanoic acid in presence of conc. H₂SO₄, one of the derivatives of carboxylic acid is obtained. Write the reactions involved in both conditions. What would be the product obtained when the same alcohol is heated with conc. H₂SO₄? How would you distinguish the above alcohol from methanol?
An aromatic compound known as oil of mirbane is prepared from benzene.
What product would you obtain when the compound is electrolyzed in acidic medium?
Give the complete reaction for the conversion of the compound into yellow dye.
An organic compound is used in the given figure to preserve museum specimens and also to prepare urinary antiseptics.
Write the reaction when the compound is heated with concentrated sodium hydroxide.
Draw the structure of urinary antiseptic.
Write the chemical reaction that would occur when the given preservative is treated with phenol in acidic medium.
How would you obtain the preservative from methanol?
A carbonyl compound with molecular formula C₃H₆O (it does not give silver mirror test) has treated with a compound Y which gives Z. Z on hydrolysis in acidic medium gives 2-hydroxy-2-methyl propanoic acid. Identify the carbonyl compound, Y and Z with proper reactions.
Starting from compound P, how do the reactions proceed ahead to obtain T which gives benzene where R is aniline? Complete the reaction sequence with suitable conditions.
Arrange the given compounds according to their ascending order of acidic strength and justify your order.
CH₃CH₂COOH, C₆H₅COOH, ClCH₂CH₂COOH
Paper Overview & Analysis
2078
Year
Model Question
Type
75
Full Marks
32
Pass Marks
3 Hours
Duration
51
Question Items
Question Type Breakdown
Group Breakdown
Chapter Breakdown
| Nitro Compounds | 3 items | 7 marks |
| Cement | 2 items | 4 marks |
| Alcohols | 2 items | 10 marks |
| Amines | 2 items | 7 marks |
| Volumetric Analysis | 1 item | 1 mark |
| Ionic Equilibrium | 1 item | 1 mark |
| Chemical Kinetics | 1 item | 1 mark |
| Electrochemistry | 1 item | 1 mark |
| Transition Metals | 1 item | 1 mark |
| Study of Heavy Metals | 1 item | 1 mark |
| Organometallic Compounds | 1 item | 1 mark |
| Paper and Pulp | 1 item | 1 mark |
| Nuclear chemistry and application of radioactivity | 1 item | 1 mark |
| Aldehydes and Ketones | 1 item | 5 marks |
| Chemistry in the Service of Mankind | 1 item | 1 mark |
| Thermodynamics | 1 item | 4 marks |
| Carboxylic Acid and its Derivatives | 1 item | 3 marks |
Chapter breakdown covers 22 of 51 question items on this paper — the rest aren't tagged to a chapter yet.