ADVANCED CHEMISTRY QUESTIONS & ANSWERS – SOLVED PROBLEMS

Conditions of hydrogen bonding
(i)  The highly electronegative atom should be small in size

(ii) The more electronegative atom must have a lone pair
(iii) Hydrogen should be bonded to one of the most electronegative atom N, O, F

CO₂  is non polar since its dipole moment cancel each other since it is symmetrical.  But CO is polar since it has a dipole moment caused by electronegativity difference between carbon and oxygen.

                                    Na and K

•                            Na has higher Boiling Point since it has stronger metallic bond than K
•                            Ca has a small size with high charge (+2) hence high polarizing power to C

Thus CaCis more covalent.  N has high size with low charge (+1) this results to low p.p to CC^– hence NaCl is ionic.

1.   9. (a)  Give the meaning of second order reaction and derive the units of its rate constant

(b)   The reaction between Br  and B in acidic medium is given by the equation.
Br_(aq)^–  +  5B_(aq)  +  6 _(aq)         → 3B_(l)   +  O_{(l) .}

The following table gives the results of four different experiments

Experiment. No	1	2	3	4
Br – Br– H+	0.2 0.2 0.2	0.4 0.2 0.2	0.4 0.4 0.2	0.2 0.2 0.4
Initial rates	1.56×10-2	2.56×10-2	5.12×10-2	5.12×10-2

 

Calculate:

 (i) Order of reaction with respect to each reactant

(ii) The value of rate constant

2.  10.  (a)   Briefly explain the meaning of:

(i) Metallurgy

(ii) An ore

  (b)  Describe the essential steps used during extraction of tin(Sn) show clearly the reaction equations

3.     (c)  Indicate the structure of monomers  and polymerization method which is likely to be  used in making of each of the following commercial        polymer

(d)  Describe the preparation of benzanamine benzene

(e)  Write the chemical equation to show how propanamine reacts with

(i) Mixture of trichloromethane and potassium hydroxide

(ii)  Ethanoic acid

(iii) Chloromethane

  ANSWERS:

9.(a) Second order reaction is the reaction in which the rate of reaction is proportional to the Second power of concentration of a single reactant

or first powers of concentration of two reactants.

(b)   Solution:

(i) R = K [Br O₃^–] ^x    [Br^–] ^y [H] ²

     =

K= 1

   =

    =   ^y

   y   = 1

   =  

 = X

  = 

  = 

Z = 1, Y = 1, Z = 2

  ^I, ¹²

  (ii)   Solution:

  R = K      

 1.28×10 ^–L = K     

10.   (a) Ore

(b)   Solution:

      The ore in which tin is extracted is called cassiterite (Sn)

   Concentration of ore:

Cassiterite is pulverized in ball mills. Magnetic impurities such as Fe and Mn are separated out by magnetic separation while other

impurities are removed by Wilfley’s table or hydraulic classifier method. This is done in a reverberatory furnace excess supply of air where

volatile impurities are given out. Impurities of sulphur and arsenic are volatized away.

 M +     _→  M  

 M = As, 5b

S +   _→  S

Smelting:
In this process, there is reduction of tin oxide to tin using coal. Temperature should be around 1200 to 1300

But some of the tin oxide will give SnO which will react with silica to form slag

Purification:

This is done in a chamber with no entrance of oxygen

(b) Solution:

N                                        N

        + H N                   

              Benzene                                                                                benzanamine

(c) Solution

   

1.   11. (a)  (i)   State the partition law

            (ii)   Write down the conditions for the law above to hold

(iii)  The partition coefficient for iodine between water and C at 20 is 2.43×10^-3 .A 100 cm³ sample of solution of iodine in O of conc 1.00×10^-3 M is shaken with 10.00 cm³ of C_. What fraction of iodine is extracted by C.

(b)  Define precisely the following terms:

 (i)  Standard molar enthalpy of formation

 (ii)  Heat of solution of a substance

(iii)  Ionization energy

(c)  (i)  State Hess’s law of constant heat summation

(ii) Calculate the standard heat of formation of carbon-monoxide if standard heat of combustion of carbon and carbon monoxide are 393 KJ

mol^-1 and – 285 KJ mol^-1 respectively.

(iii) Determine the enthalpy change for the isomerization reaction:

The heat of formation of OH is = 276 KJ mol^-1

The heat of combustion of C – O – C is = 1456 kJmol^-1

The heat of formation of O is =284 KJ mol^-1

The heat of combustion of carbon is  =394 KJ mol^-1

2.  12.  (a)   Explain the meaning of the following and give one example:

(i)   Nucleophilic addition reaction

(ii)  Nucleophilic substitution reaction

(iii) Elimination reaction

(b)   How can you distinguish the following compounds

(c) Illustrate the preparation of the following compounds

(i)  Propanoic acid from ethane
(ii) Propan  – 2 – ol from propan -1-ol
(iii) Propyne from ethyne

13.(a) Explain the following with vivid example and relevant chemical equations.
(i) Li and Mg are more related chemically than Li and Na although both Li and Na are group I
(ii) F is the most oxidizing element of all in the periodic table
(iii) Electron affinity of F is unusually low

(b)  Distinguish between the following:

(i)  Coordination number and oxidation number

(ii)  Paramagnetism and ferromagnetism

(iii)  Strong ligand and weak ligand

ANSWERS:

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