Q25 of 26 Page 1

(a) Account for the following:

(i) Mn2O7 is acidic whereas MnO is basic.


(ii) Though copper has completely filled d-orbital (d10) yet it is considered as a transition metal.


(iii) Actinoids show wide range of oxidation states.


(b) Write the preparation of potassium permanganate from pyrolusite ore (MnO2).


OR


(a) The elements of 3d transition series are given as:



Answer the following:


(i) Which element has the highest m.p. and why?


(ii) Which element is a strong oxidizing agent in +3 oxidation state and why?


(iii) Which element is soft and why?


(b) Write the equations involved in the preparation of Potassium dichromate from Sodium chromate (Na2CrO4).


(a)

(i) Mn has +7 oxidation state in Mn₂O₇ and +2 in MnO. Transition metals are basic in lowest oxide and acts as acidic in highest oxide. Thus, MnO is basic whereas Mn2O7 is acidic in nature.

(ii) Cu has electronic configuration 3d104s1. On losing two electrons it forms Cu2+ and its electronic configuration becomes 3d9 which is partially filled. It means Cu has partially filled d-orbitals in its stable oxidation state and thus, Cu is a transition element.

(iii) Actinoids show wide range of oxidation states due to comparable energies of 5f, 6d, 7s orbitals. Moreover, 5f orbitals are not as buried as 4f and hence, 5f electrons can participate in bonding.


(b)


OR


(a)


(i) Cr has highest melting point because it has half-filled orbitals (3d54s1). More the number of unpaired electrons, stronger is the metallic bonding because the strength of metallic bonding depends on the no. of unpaired d-electrons. Stronger the metallic bonding, higher will be the boiling point.


(ii) Manganese is a strong oxidizing agent in +3 oxidation state as Mn3+ has 3d4 configuration, it will oxidize others and itself will get reduced to Mn2+ which has stable 3d5 configuration because it is exactly half-filled.


(iii) Zn is a soft element because it has d10 configuration that’s why it does not form metallic bonds and is soft.


(b) The equations involved in the preparation of Potassium dichromate from Sodium chromate (Na2CrO4) is


2 Na2CrO4 + 2H+ → Na2Cr2O7 + H2O + 2Na+


Na2Cr2O7 + 2KCl → K2Cr2O7 + 2NaCl

More from this chapter

All 26 →
22

Write the major product(s) in the following reactions:


 23

Due to hectic and busy schedule, Mr. Awasthi made his life full of tensions and anxiety. He started taking sleeping pills to overcome the depression without consulting the doctor. Mr. Roy, a close friend of Mr. Awasthi, advised him to stop taking sleeping pills and suggested to change his lifestyle by doing Yoga, meditation and some physical exercise. Mr. Awasthi followed his friend’s advice and after few days he started feeling better.

After reading the above passage, answer the following:


(i) What are the values (at least two) displayed by Mr. Roy?


(ii) Why it is not advisable to take sleeping pills without consulting doctor?


(iii) What are tranquilizers? Give two examples.


 24

(a) Calculate ∆G° and log Kc for the following reaction at 298 K:

2Cr(s) + 3Fe2+(aq) → 2Cr3+(aq) + 3Fe(s)


Given: E°cell = 0.30 V


(b) Using the E° values of A and B, predict which is better for coating the surface of iron [E° (Fe2+|Fe) = –0.44 V] to prevent corrosion and why?


Given: E°(A2+|A) = –2.37 V : E°(B2+|B) = –0.14 V


OR


(a) The conductivity of 0.001 mol/L solution of CH3COOH is 3.905 × 10-5 S/cm. Calculate its molar conductivity and degree of dissociation.


Given: λ° (H+) = 349.6 S cm2 mol-1 and λ° (CH3COO-) = 40.9 S cm2 mol-1.


(b) What type of battery is lead storage battery? Write the overall reaction occurring in lead storage battery.


 26

(a) Write the major product(s) in each of the following reactions:


(b) Write the chemical reaction involved in the following reactions:


(i) Kolbe’s reaction


(ii) Friedal-Crafts acetylation of anisole


OR


(a) What happens when


(i) Phenol reacts with Bromine water?


(ii) Ethanol reacts with CH3COCl/pyridine?


(iii) Anisole reacts with HI?


Write the chemical equations involved in the above reactions.


(b) Distinguish between:


(i) Ethanol and phenol


(ii) Propan-2-ol and 2-methylpropan-2-ol