RGU Question Paper Chemistry Semester III 2022: General Chemistry-III

 

December-2022

B.Sc (III Semester) Examination (CBCS)

CHEMISTRY

Paper: CHE-GE-003

( General Chemistry-III)

Full Marks : 80

Pass Marks : 35%

Time : Three Hours

Note: 1. Questions are divided into three Sections -A, B and C.

2. Read the instructions given in each Section carefully and answer the questions accordingly.
3. The figures in the margin indicate full marks for the questions.

Section-A

1. Answer any four of the following questions : 5×4=20

(a) Draw the structure of peroxoacids of sulphur and phosphorus.

(b) Define the terms - phase, component and degree of freedom. Calculate the number of phases and degrees of freedom for the following systems :
(i) A gas in equilibrium with its solution in a liquid
(i) Two partially miscible liquids in absence of vapour

(c) Express the relation between conductivity and molar conductivity of solution. The resistance of 0•01 M NaC1 solution at 25 °C is 200 ohm. The cell constant of the conductivity cell used is unity. Calculate the molar conductivity of this solution.

(d) Calculate the e.m.f. of the following cell at 25 °C :
$Cr\left|C{r}^{3+}(0.1 M)\parallel F{e}^{2+} \left(0.01M\right)\right|Fe$
Given,

${\dot{E}}_{C{r}^{3+}|Cr}=-0.74 volt,{\dot{E}}_{F{e}^{2+}|Fe}=-0.44 volt$

(e) What is pinacol-pinacolone rearran-gement?

(f) Discuss the bromination and nitration of phenol.

Section-B

2. Answer any three of the following questions : 10×3=30

(a) What are carbides? Discuss the classification of carbides. Give the action of water on different types of carbides. 2+3+5=10

(b) State and explain Clausius-Clapeyron equation. Discuss its applications to solid-liquid and liquid-vapour equilibria. 2+5+3=10

(c) Discuss the determination of free energy, enthalpy and entropy of a cell reaction using EMF data.

(d) (i) Discuss the mechanism of Reimer-Tiemann reaction and aldol condensation. 6

(ii) How will you convert the following? 1×4=4

1. Toluene to benzaldehyde 

2. Ethyne to ethanal
3. Propanone to propanol
4. Benzoic acid to benzaldehyde

(e) What do you mean by Kohlrausch's law of independent law of migration Discuss its application. The molar conductivities at infinite dilution of NHCI, NaOH and NaCI are 129.8, 217.4 and 108.9 $S c{m}^2 mo{l}^{-1}$, respectively. Calculate the molar conductivity of $N{H}_{4}OH$ at infinite dilution at 298 K. 2+3+5=10

Section-C

3. Answer any two of the following questions: 15×2=30

(a) (i) What are silicones? How are they prepared? Mention important properties and uses of silicones. 1+5+4=10

(ii) Why are interhalogen compounds more reactive than halogens? Discuss the hybridization and geometry of interhalogen compounds of $XX{\text{'}}_3$ and $XX{\text{'}}_5$ types. 2+3=5

b) i) What is Nernst distribution law? What are its limitations? How can it be derived thermodynamically? 2+2+6=10

(ii) Succinic acid is shaken with a mixture of 100 ml of water and 50 ml of ether. At equilibrium, 0•127 g of the acid is found in ether layer and 1•843 g in water layer. Find the partition coefficient of succinic acid between water and ether. 5

(c) (i) What is transport number? Derive relation between ionic mobility and transport number. The ionic mobilities of $N{H}^{4+}$ and $HC{O^{-}}_3$ are $6\times {10}^{-4} V^{-1}{s}^{-1}$ and $6\times {10}^{-4} V^{-1}{s}^{-1}$ respectively. Calculate the transport number of $N{H}^{4+}$ and $HC{O^{-}}_3$. 1+4+5=10

(i) Define liquid junction potential. How can it be eliminated? 5

(d) (i) What is the drawback of Williamson ether synthesis? What happens when anisole is treated with HI? 4+1=5

(ii) Identify the products (A, B and C) in the following sequence of reactions: 5

$Isopropyl alcohol\underset{H_{2}S{O}_4}{\overset{K_{2}C{r}_2{O}_7}{\to }}A\stackrel{C{H}_{3}MgBr}{\to }B\stackrel{H_{2}O/H^{+}}{\to }C$

(iii) An organic compound A, having the formula, $C_3{H}_{8}O$, on treatment with copper at 573 K, gives B. B does not reduce Fehling's solution but gives a yellow precipitate of the compound C with $I_2/NaOH$. Deduce the structures of A, B and C. 5