ASSIGNMENT FOR CHAPTER 5 & 6     CLASS XI




1.The enthalpy of combustion of methane, graphite and dihydrogen at 298K are -890.3 KJ/mole, -393.5 KJ/mole, and -285.8 KJ/mole, respectively. Find the enthalpy of formation of methane.                                  
2. The ejection of the photoelectrons from the silver metal in the photoelectric effect experiment can be stopped by applying the voltage of 0.35eV when the radiation 256.7 nm is used. Calculate the work function for silver metal.
3.In a compound C,H and N are present in ratio 9:1:3.5 by weight. Molecular mass of the compound is 108.Find out its molecular formula?                                                           
4.Explain Andrew’s Experiment for Liquifaction of gases? What is the significance of critical temperature?                                                                                                                     

5. a) What is the effect of temperature on viscosity and surface tension of a liquid?          

   b) Calculate the average kinetic energy of 32g of methane at 27°C [ R=8.314J/K/mol ]   

   c) What will be the minimum pressure required to compress 500 dm³ of air at 1 bar to 200 dm³ at 30°C?   






 ASSIGNMENT FOR CHAPTER 5 & 6     CLASS XIi    

 1. State the principles: Zone refining, van Arkle process, Liquation
 2.Explain the following terms giving a suitable example in each case: emulsification, homogeneous catalysis

 3 Define adsorption. Write any two features which distinguish physisorption from chemisorption.  

 4. What are associated colloids? Give two examples. How does associated colloid differ from  Multi molecular and macro molecular colloids.   

 5.Why NaCN is used in froth floatation process?  

 6.  What is peptization? Give example. 

 7. (i) Dialysis is a method of purification of sols. But prolonged dialysis of the sol makes it unstable.Why ?

    (ii)Out of CO and NH3 which is adsorbed on activated charcoal to a large extent and why?

    (iii)Out of PO43–,SO42–, Al3+ and Na+,which will have the highest coagulating power for As2S3 colloid ?                                                                                                        

chapter 9          coordination  compounds          XII CHEM 

1.
For the complex [Fe(en)2Cl2] Cl, (en = ethylene diamine), identify

(i) The oxidation number of iron,

(ii) The hybrid orbitals and the shape of the complex,

(iii) The magnetic behaviour of the complex,

(iv) The number of geometrical isomers,

(v) Whether there is an optical isomer also, and

(vi) Name of the complex. (At. No. of Fe = 26)

2.
Compare the following complexes with respect to their shape, magnetic behaviour and the hybrid orbitals involved:

(i) [CoF4]2−

(ii) [Cr(H2O)2 (C2O4)2]−

(iii) [Ni(CO)4]

3.
Write the name and draw the structure of each of the following complex compounds:

(i) [Co(NH3)4 (H2O)2]Cl3

(ii) [Pt(NH3)4] [NiCl4]

XII CHEM Practice assignments dated 26.06.12

p-block elements
1.
In the following cases rearrange the compounds as directed:

(i) In an increasing order of basic strength:

C6H5NH2,C6H5 N (CH3)2, (C2H5)2 NH and CH3NH2

(ii) In a decreasing order of basic strength:

Aniline, p-nitroaniline and p-toluidine

(iii) In an increasing order of pKb values:

C2H5NH2, C6H5 NHCH3, (C2H5)2 NH and C6H5NH2

2.
 How would you account for the following?

(i) The value of electron gain enthalpy with negative sign for sulphur is higher than that for oxygen.

(ii) NF3 is an exothermic compound but NCl3 is endothermic compound.

(iii) ClF3 molecule has a T-shaped structure and not a trigonal planar one.

3.
 Explain the following observations giving appropriate reasons:

(i) The stability of + 5 oxidation state decreases down the group in group 15 of the periodic table.

(ii) Solid phosphorus pentachloride behaves as an ionic compound.

4.
Account for the following:

(i) NH3 is a stronger base than PH3.

(ii) Sulphur has a greater tendency for catenation than oxygen.

(iii) Bond dissociation energy of F2 is less than that of Cl2.

5.
Explain the following situations:
(i) In the structure of HNO3 molecule, the N − O bond (121 pm) is shorter than the N − OH bond (140 pm).

(ii) SF4 is easily hydrolysed whereas SF6 is not easily hydrolysed.

(iii) XeF2 has a straight linear structure and not a bent angular structure.

classXII chem                                                     DATE: 25.06.12

Subjective Ques. from d- and f- blocks

1.Explain the following observations:

(i) Transition elements generally form coloured compounds.

(ii) Zinc is not regarded as a transition element.



2.How would you account for the following?

(i) The atomic radii of the metals of the third (5d) series of transition elements are virtually the same as those of the corresponding members of the second (4d) series.

(ii) The E° Value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+ couple or Fe3+/Fe2+ couple.

(iii) The highest oxidation state of a metal is exhibited in its oxide or fluoride.


3.(a) What is meant by the term lanthanoid contraction? What is it due to and what consequences does it have on the chemistry of elements following lanthanoids in the periodic table?

(b) Explain the following observations:

(i) Cu+ ion is unstable in aqueous solutions.

(ii) Although Co2+ ion appears to be stable, it is easily oxidised to Co3+ ion in the presence of a strong ligand.

(iii) The value for manganese is much more than expected from the trend for other elements in the series.


4.Explain the following observations about the transition/inner transition elements:

(i) There is in general an increase in density of element from titanium (Z = 22) to copper (Z = 29).

(ii) There occurs much more frequent metal−metal bonding in compounds of heavy transition elements (3rd series).

(iii) The members of the actinoid series exhibit a larger number of oxidation states than the corresponding members of the lanthanoid series.


5.Give an explanation for each of the following observations:

(i) The gradual decrease in size (actinoid contractions) from element to element is greater among the actinoids than among the lanthanoids (lanthanoid contraction).

(ii) The greatest number of oxidation states are exhibited by the members in the middle of a transition series.

(iii) With the same d-orbital configuration (d4) Cr2+ ion is a reducing agent but Mn3+ ion is an oxidising agent.

Chapter	The Solid State	Time Allotted:  15 Minutes	Test Date:  22-Jun-2012
Class	XII-CHEMISTRY

Q1.Metals act as good conductors of electricity because they have A : empty spaces in the valence energy band B : filled spaces in the valence energy band C : hydrogen bonding D : ionic bonding

Q2.Which type of bond leads to good thermal and electrical conductivity in solids? A : Ionic B : Metallic C : Covalent D : Van der Waals

Q3.Covalent compounds are soluble in A : methanol B : ammonia C : benzene D : water

Q4.Which of the following solutes will dissolve to form a molecular solution? A : AlCl3 B : AgNO3 C : CH3OH D : KMnO4

Q5.. The decomposition reaction of potassium chlorate is represented as 2KClO3 (s) → 2KCl (s) + 3O2 (g) KCl can be characterized as A : brittle B : very hard C : soft and waxy D : malleable and ductile

Q6. The decomposition reaction of potassium chlorate is represented as 2KClO3 (s) → 2KCl (s) + 3O2 (g) KCl will conduct electricity in A : water B : ethanol C : benzene D : chloroform

Q7.. The decomposition reaction of potassium chlorate is represented as 2KClO3 (s) → 2KCl (s) + 3O2 (g) The KCl formed in the given reaction is an example of A : molecular solids B : metallic solids C : covalent solids D : ionic solids

Q8. The given chemical equation represents an anionic single replacement reaction. 2ZnS + O2 → 2ZnO + 2S ZnO can be characterized as A : brittle B : very hard C : soft and waxy D : malleable and ductile

Q9. The given chemical equation represents an anionic single replacement reaction. 2ZnS + O2 → 2ZnO + 2S The boiling point of ZnO is A : moderate B : variable C : high D : low

Q10. The precipitation reaction of silver chloride is represented as 2AgNO3 + CaCl2 → AgCl + Ca(NO3)2 The silver chloride (AgCl) formed in the given reaction is an example of A : ionic solids B : metallic solids C : polar covalent solids D : non-polar covalent solids

Q11. Common table sugar i.e., sucrose is an example of A : molecular solids B : covalent solids C : metallic solids D : ionic solids

Q12.In a crystal structure, the formula for ionic solids represents the A : complete molecule B : symbol for the metallic element C : ratio of cations to anions in the crystal D : ratio of the various atoms in the crystal

Q13.Malleability and ductility are the properties of A : ionic solids B : metallic solids C : covalent solids D : molecular solids

Q14.The class of solids that has very high melting and boiling points is A : non-polar molecular solids B : polar molecular solids C : covalent solids D : metallic solids

Q15.Which type of solid is soft and waxy in nature? A : Covalent B : Metallic C : Polar D : Ionic