Chemistry Old Questions- Bsc I Year 2076

Bsc I Year Chemistry Question-2077,bsc questions, chemistry questions, tribhuvan university,first year question, bachelor in science,

Chemistry Old Questions- Bsc I Year 2076

Tribhuvan University 2076

Bachelor Level 4 Yrs. Prog/ 1st Year/Science & Tech

Full Marks: 100


Time: 3 hrs.

Candidates are required to give their answers in their own words as far as practicable. The figures in the margin indicate full marks.

The Comprehensive Question of each group is compulsory.

Use separate answer-book for each group. The Comprehensive Question  of each group is compulsory. Attempt SIX questions of Short Answer Questions of each Group.


  1. Comprehensive Question

What is Schrodinger's equation? What are the terms involved in the equation? Discuss the significance of Ψ and Ψ2 with reference to this equation. [1+4+4]


What is meant by Born-Haber cycle? How this concept can be applied for estimating the stability of ionic compounds? [2+7]

  1. Short Answer Questions (6×4=24)

2.1. Write the possible values of l and m for an electron in 4d orbital.

2.2. What is meant by nuclear fission and nuclear fusion give an example of each?

2.3. How many groups and periods are present in the IUPAC system of periodic table? Point out the advantages of IUPAC system over long form periodic table.

2.4. What are stoichiometric and non-stoichiometric defects? Give an example of each.

2.5. What is meant by electronegativity of an element? On what basis is panling’s scale of electronegativity is based?

2.6. What is meant by HSAB principle? What are the factors that governs the hardness of a hard acid?

2.7- Point out any two requirements that should be met in order that a gravimetric analysis be successful.

2.8. What is meant by USEPR theory? In what type of compound this theory can be applied? Predict the structure of ClF3 based on this theory.

2.9. Use molecular orbital theory to explain why the bond strength in N2 molecule is greater than in F2 molecule.




  1. Comprehensive Question

How does E1 reaction differ from E2 in mechanistic aspect? Explain reactivity order of alkylhalides towards El and E2. reactions. Dehalogenation of vicinal dihalides give alkenes. Give an example of such reaction and show appropriate mechanism. [3+3+3]


Why are alkanes called paraffins? Explain why branched chain alkanes have got lower boiling points as compared to their corresponding straight chain isomers with example. Give evidence to show that chlorination of methane involve a free radical mechanism. [1+3+5]

  1. Short Answer Questions (6×4=24)
  2. 1. Explain the following facts:
  3. a) Greater the resonance energy, greater is the stability of the molecule.
  4. b) The electronic effect comes into play when the attacking reagent is brought near the substrate.

4.2. What is crecking? How is it useful in the petroleum industry?

4.3. What do you understand by the contribution of a compound? Discuss with examples how the sequence rule applies in fixing the R and S configuration of a compound.

4.4. What are the factors that affect SN1 and SN2 reactions? Explain them.

4.5. How is it possible to know whether the given alkene is 1-hexene, 2-hexene or 3-hexene?

4.6. Give an explanation for the following facts:

a) 2-methyl-2-propanol dehydrates faster than 2-methyl-1-1-propanol.

b) Alcohols can act either as an acid or base.

4.7. Hydration of alkyne gave methyl propyl ketone. What formula would you assign to the alkyne? Give mechanism also.

4.8. Draw compounds that fit the following descriptions:

a)A chiral alcohol with four carbons.

b)A chiral haloalkane with the formula C5H11Br.

c)A meso alkane with the formula C8H18.

d)A chiral alkene with the formula C8H18.

4.9. When 3,3-dimethyl-2-butanol is treated with concentrated H2SO4, rearrangement takes place. What alkyliodide group would you expect from the reaction? Show the mechanism by which it is formed.


  1. Comprehensive Question

What arc critical constants and van der Waal's constants. Derive-: their relationship starting from van der Waal's equation. Show that the compressibility factor (z) of a gas at its critical point is 3/8. The critical temperature and critical pressure of Argon gas are -122.440C and 48 atm respectively. Calculate van der Waal’s constant 'a’ and ‘b’ of the gas. [3+3+2+2]


Define molar heat capacity. Derive the relationship between the molar heat capacity at constant pressure and the molar heat capacity at constant volume for an ideal gas. Calculate the enthalpy change at 35°C for the reaction:

½ H2(g) + Cl2(g) → 2 HCl(g); ΔH° = -22.0 k cal at 298 K,
given ,Cp for H2 = 6.8 cal K-1 mol-1 at 250C,
Cp for Cl2 = 7.7 cal K-1 mol-1 at 250C,
Cp for HCl = 6.8 cal K-1 mol-1 at 250C

  1. Short Answer Questions (6×4=24)

6.1: What are ionic solids, and how do they differ from molecular solids?

6.2: Describe a method to determine the surface tension of a liquid in the laboratory.

6.3: Deduce an expression for the pH of an aqueous solution of a salt that is formed by the reaction of a weak acid and a strong base at a particular concentration.

6.4: Show that for a reaction of the type AB(g) ⇌ A(g)+ B(g), the total pressure at which 50% of AB is dissociated will be numerically equal to three times the equilibrium constant, Kp.

6.5: How do you prepare a buffer of pH 4.70 using acetic acid and sodium acetate?
Given Ka for acetic acid is 1.75 × 10-5.

6.6: Write the expression for the law of elevation of boiling point of a dilute solution and define the boiling point constant.

6.7: An aqueous solution of a non-volatile solute boils at 373.09K. Calculate the freezing point of the same solution. Given, Kb = 0.512 K kg mol-1 and Kf = 1.86 K kg mol-1.

6.8: Define half-life and activation energy of a reaction. The half-life for a given reaction was halved as the initial concentration of a reactant was doubled. What is the order for this reaction?

6.9: Derive an expression for the rate constant of a second-order reaction with the same initial concentration of the reactants. A substance decomposes according to the second-order rate law. If the rate constant is 6.8 × 104 L mol-1, calculate the half-life of the substance when the initial concentration is 0.05 mol L-1.


OLD Course

Use separate answer-book for each group. The Comprehensive Question  of each group is compulsory. Attempt SIX questions of Short Answer Questions of each Group.



1.Comprehensive Question

(a) What are the basic postulates of Bohr's atomic model?

(b) Discuss the refinements of Bohr's theory of the hydrogen atom.


What is meant by linear combination of atomic orbitals (LCAO)? List three rules for LCAO. Draw the molecular orbital energy level diagram of the F2 molecule and also give the bond order and magnetic properties of the molecule.


  1. Short Answer Questions (6×4=24)

2.1 State and illustrate Pauli's exclusion principle.

2.2 What is half-life period? If 2.0 g of a radioactive element is reduced to 0.25 g in 24 hours, what is the half-life of the element?

2.3 How does the IUPAC system of the periodic table differ from the Mendeleev form of the periodic table?

2.4 What is electron affinity? What are the factors that affect electron affinity?

2.5 What is meant by Frenkel defect? How does it differ from Schottky defect?

2.6 Draw the crystal structure of Zinc Blende and explain it briefly.

2.7 Predict the shape of the following molecules based on the hybridization of the central atom: (a) SF6 (b) BF3 (c) PCI5 (d) IF7

2.8 What is the HSAB principle? What are its applications?

2.9 What is volumetric analysis? Explain briefly the general principle of volumetric analysis.



  1. Comprehensive Question

(a) How does the SN1 reaction differ from the SN2 mechanism in terms of stereochemistry? Give the mechanism of addition of HBr into propene in the presence of peroxide.


Discuss the mechanism of addition of the following reagents to an olefinic compound:

(a) water     (b) halogen     (c) Halogen acid

  1. Short Answer Questions (6×4=24)

4.1. Write a short note on Inductive effect and resonance effect.

4.2. Predict the proportions of isomeric products from chlorination at room temperature of
(a) propane and
(b) isobutene.

4.3. What is specific rotation? A 0.1 M solution of a compound with molecular weight 342 was placed in a one decimeter cuvette. When plane polarized light was passed through it, the light was rotated to ±2.2°. Calculate the specific rotation of the compound.

4.4. Draw the isomers of C4H9Br, give their IUPAC names, and arrange them in order of decreasing reactivity in the SN2 reaction with reason.

4.5. Rank the following substances in order of their acidity and explain the reason: (i) (CH3)2CHOH, (ii) CH3OH, (iii) (CF3)2CHOH, and (iv) H-C ≡ C-H.

4.6. Write a chemical reaction for the preparation of an ether by dehydration of an alcohol and give its mechanism.

4.7. What are ozonides and how are they formed? How has ozonolysis proved useful in locating double bonds in long organic molecules?

4.8. Outline all steps in the synthesis of propyne from (a) CH3COCH3 and (b) CH3-CH=CH2.

4.9. What is asymmetric synthesis? Explain it with two examples.

GROUP "C" (Physical)

  1. Comprehensive Question

Deduce an expression for the pH of an aqueous solution of a salt of weak base and strong acid at a particular concentration.

Find the pH of a buffer solution that contains equal volumes of 0.25 M NH3 and 0.40 M NH4Cl solutions.                           [5+5]


Write Van der Wall's equation of state for one mole of a gas. What are the units of Van der Wall's constants and what do they signify? How does the equation interprete the deviation of real gas from ideal gas behaviour? Calculate the temperature at which the average speed of hydrogen molecules equals that of oxygen at 320°C. [4+2+4]

  1. Short Answer Questions (6×4=24)

6.1. What is viscosity of a liquid? What is its unit? What is the effect of temperature on the viscosity of a liquid?

6.2. Point out the difference between a crystalline solid and an amorphous solid.

6.3. When 1.0 mole of acetic acid was mixed with 0.18 mole of ethyl alcohol, 0.171 mole of ethyl acetate was formed at equilibrium. If 1.0 mole of acetic acid be mixed with 0.5 mole of ethyl alcohol, how much ethyl acetate would be formed at equilibrium?

6.4. Give the reasons why osmotic pressure of a dilute solution is a colligative property. Define isotonic solution, hypotonic solution and hypertonic solution.

6.5. How can you determine the molecular weight of a non-volatile solute by measuring the elevation in boiling point of its solution?

6.6. Write notes on peptization and coagulation.

6.7. Define molar heat capacity. Deduce a relationship between the molar heat capacity at constant pressure and molar heat capacity at constant volume for an ideal gas.

6.8. Derive Kirchoff's equation showing the variation of enthalpy of reaction with temperature. Calculate the enthalpy changes at 35°C for the reaction:

H2(g) + Cl2(g) → 2HCl(g)

Given: Standard enthalpy of formation of HCl is -22.08 kcal mol-1, Cp for H2 = 6.8 cal K-1mol-1 at 25°C, Cp for Cl2 = 7.7cal K-1mol-1 at 25°C, Cp for HCl = 6.8 cal
K-1mol-1 at 25°C.

6.9. Derive expressions of work done during expansion of an ideal gas for reversible and irreversible processes. Show that Wrev>Wirr.