Chemistry - B.Tech 2nd Semester Special Exam., 2020
Chemistry
Instructions:
- The marks are indicated in the right-hand margin.
- There are NINE questions in this paper.
- Attempt FIVE questions in all.
- Question No. I is compulsory.
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Arrange the following in increasing order of stability:
\( \text{N}_2, \text{N}_2^+, \text{N}_2^-, \text{N}_2^{2-} \)
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Transition metal ions like \( \text{Cu}^+ \) and \( \text{Ag}^+ \) are colourless. Why?
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Which of \( \text{Cr}^+ \) or \( \text{Cu}^+ \) is expected to be coloured?
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\( ^{13}\text{C} \) is NMR active, but \( ^{12}\text{C} \) is not. Why?
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What is the direction of a reaction when \( \Delta G = 0 \)?
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Why is work not a state function?
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Write the relationship between parts per million [ppm] and Clarke's degree [°C].
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What is critical temperature of a gas?
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Arrange the following ligands in order of increasing field strength:
\( \text{CN}^-, \text{CO}, \text{H}_2\text{O}, \text{NH}_3 \)
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Arrange the following in order of their increasing reactivity in nucleophilic substitution reaction:
\( \text{CH}_3\text{F}, \text{CH}_3\text{I}, \text{CH}_3\text{Br}, \text{CH}_3\text{Cl} \)
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At what temperature will water boil when the applied pressure is 528 mm of Hg? (Latent heat of vaporisation of water = 545.5 cal/g)
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At NTP, 2.8 L of \( \text{O}_2 \) were mixed with 19.6 L of \( \text{H}_2 \). Calculate the increase in entropy (assume ideal gas behaviour).
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The equilibrium constants for the reaction \( \text{H}_2[g] + \text{S(s)} \rightarrow \text{H}_2\text{S[g]} \) are 18.5 at 925 K and 9.25 at 1000 K. Calculate standard enthalpy of the reaction. Also calculate \( \Delta G^\circ \) and \( \Delta S^\circ \) at 925 K.
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The uncertainties in the position and velocity of a particle are \( 9.5 \times 10^{-10} \, \text{m} \) and \( 5.5 \times 10^{-20} \, \text{ms}^{-1} \), respectively. Calculate the mass of the particle. \( (h = 6.626 \times 10^{-34} \, \text{J·s}) \)
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Calculate the kinetic energy of a moving electron which has a wavelength of 48 pm. [Mass of electron = \( 9.11 \times 10^{-31} \, \text{kg} \)]
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Discuss the failures of classical mechanics to explain properties of particles at atomic and sub-atomic levels.
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Draw the MO energy-level diagram for \( \text{O}_2 \) and based on the diagram, and explain the magnetic property observed in \( \text{O}_2 \), \( \text{O}_2^+ \) and \( \text{O}_2^- \).
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Explain geometrical isomerism and optical isomerism for transition metal complex with an example for each.
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The internuclear distance of NaCl is \( 2.36 \times 10^{-10} \, \text{m} \). Calculate the reduced mass and moment of inertia of NaCl. (Atomic mass of Cl = \( 35 \times 10^{-3} \, \text{kg mol}^{-1} \) and Na = \( 23 \times 10^{-3} \, \text{kg mol}^{-1} \))
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Calculate the force constant for CO, if it absorbs at \( 2.143 \times 10^{5} \, \text{m}^{-1} \). (Atomic mass of C = \( 12 \times 10^{-3} \, \text{kg mol}^{-1} \) and O = \( 16 \times 10^{-3} \, \text{kg mol}^{-1} \))
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How many \( ^{1}\text{H} \) NMR signals are there in—
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2 mole of \( \text{NH}_3 \) at 300 K occupy a volume of \( 5 \times 10^{-3} \, \text{m}^3 \). Calculate the pressure using van der Waals equation \( (a = 0.417 \, \text{N m}^4 \, \text{mol}^{-2} \) and \( b = 0.037 \times 10^{-3} \, \text{m}^3 \, \text{mol}^{-1}) \). Compare the above result with the pressure calculated using ideal gas equation.
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Write short notes on the following:
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Consider the following half-cell reactions:
\( \text{PbO}_2(s) + 4 \text{H}^+ (aq) + \text{SO}_4^{2-} (aq) + 2e \rightarrow \)
\( \text{PbSO}_4(s) + 2\text{H}_2\text{O}, E^\circ = 1.70 \, \text{V} \)\( \text{PbSO}_4(s) + 2e \rightarrow \text{Pb}(s) + \text{SO}_4^{2-} (aq) \), \( E^\circ = -0.31 \, \text{V} \)
Write the cell (in proper cell notation) and the cell reaction. Calculate the value of \( E^\circ \) for the cell and the EMF generated if \( [\text{H}^+] = 0.1 \, \text{M} \) and \( [\text{SO}_4^{2-}] = 2 \, \text{M} \).
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A water sample had the following constituents per litre:
\( \text{CaCO}_3 = 81 \, \text{mg} \), \( \text{MgHCO}_3 = 75 \, \text{mg} \), \( \text{CaSO}_4 = 136 \, \text{mg} \), \( \text{MgSO}_4 = 120 \, \text{mg} \), \( \text{NaCl} = 47 \, \text{mg} \)
Calculate the quantity of temporary and permanent hardness in the water sample. Calculate the quantity of lime (78% purity) and soda (92% purity) required for softening of 1.5 million litres of the above water sample.
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Describe two methods used for resolving racemic mixtures into optically active compounds.
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Write the possible optical isomers of tartaric acid and indicate the point of symmetry or plane of symmetry (if any) in the isomers.
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Differentiate between (i) enantiomers and diastereomers and (ii) racemic mixture and meso compounds.
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How do you decide whether the reaction \( \text{CH}_3\text{Br} + \text{OH}^- \rightleftharpoons \text{CH}_3\text{OH} + \text{Br}^- \) proceeds by \( S_N1 \) or \( S_N2 \) reaction? Give justification in favour of your answer.
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Draw the energy profile diagram for the following reaction:
\( (\text{CH}_3)_2\text{CBr} + \text{OH}^- \rightleftharpoons (\text{CH}_3)_2\text{COH} + \text{Br}^- \)
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Write short notes on the following: