Chemistry : CBSE Class XII Important Questions Chemistry (2008)

Q. 1. What is lanthonoid contraction? What is the reason for lanthonoid contraction? Mention the consequences of lanthonoid contraction.

Q. 2. What is mischmetal? Mention two uses of mischmetal.

Q. 3. How is a) KMnO₄ prepared from pyrolusite ore? b) K₂Cr₂O₇ prepared from chromiteore?

Q. 4. Write the ionic equations of the reactions involved when acidified KMnO₄is treated with

1. FAS solution

2. Oxalic acid solution

3. hydrogen sulphide

4. KI solution

5. Sn²⁺ solution

6. SO₃^2-

7. NO₂-

Q. 5. Write the ionic equation of the reaction involved when alkaline KMnO₄ is reacted with

1. KI solution.

2. S₂O₃^2-

Q. 6. Write the ionic equation of the reaction involved when acidified K₂Cr₂O₇ reacts with

1. Sn²⁺solution

2. SO₂

3. hydrogen sulphide

4. Fe²⁺

Q. 7. What is the effect of PH on chromate and dichromate solutions?

Q. 8. Compare the chemistry of lanthonoids and actinoids with reference to

1. electronic configuration

2. oxidation state

3. ionization enthalpy

4. chemical reactivity

5. magnetic behaviour f) atomic size

Q. 9. What is actinoid contraction? Why is it more pronounced than lanthonoid contraction?

Q. 10. Compare the general characteristic of first row transition metals with those of second and third series metals in the respective vertical columns with reference to

1. electronic configuration

2. oxidation state

3. ionization enthalpies

4. atomic size.

Q. 11. Compare the stability of +2 oxidation state for the elements of the 3d series.

Q. 12. Cr²⁺(aq) is a better reducing agent than Fe²⁺ despite the half filled stability of Fe³⁺ Why?

Q. 13. Which transition metal exhibit only one oxidation state. Why?

Q. 14. For M²⁺/M and M³⁺/M²⁺ systems E0 values of some metals are given below.

Use the data to comment upon :

1. Stability of Fe³⁺ in acid solution when compared to Cr³⁺ and Mn³⁺

2. ease with which iron can be oxidized as compared to chromium and manganese.

Q. 15. Outer electronic configuration of elements a) X = 4f¹ 5d¹ 6s² b) Y=4f⁷ 5d⁰ 6s² Determine the

1. atomic numbers of X and Y

2. Stable oxidation states of X and Y

3. Which is an oxidizing agent and which is a reducing agent? Why?

Q. 16. Outer electronic configuration of element X is 5f⁷ 6d⁰ 7s² Determine the atomic number of the element. What is the stable oxidation state of this element?

Q. 17. Draw the structures of a) manganate ion b) permanganate ion c) chromate ion and d) dichromate ion.

Q. 18. What is disproportination reaction? Give the reaction involving disproportination of

1. Cu⁺ ion

2. MnO₄^2- ion.

Q. 19. Discuss the general properties of transition metals with reference to a) electronic configuration b) atomic radius b) ionization enthalpy c) oxidation state d) magnetic behavior e) colored compounds f) complex formation g) catalytic behavior h) interstitial compounds i) alloy formation j) electrode potential(M²⁺/M and M³⁺/M²⁺)

Q. 20. What are transition metals? Which three elements are not considered as transition metals though they are kept in d block? In which way the electronic configuration of transition element differ from non transition elements?

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