Explain why: (i) E° for Mn3+ / Mn2+ couple is more positive than that Fe3+/Fe2+. (At. No. Mn = 25, Fe = 26). (ii) Ce3+ can be easily oxidised to Ce4+ (At. No. Ce= 58).
Answer:
(i) Mn2+ is more stable than Mn3+ because Mn+2 has exactly half-filled orbitals, while Fe+2 after losing one e– half-filled orbitals. (ii) Ce+4 achieve inert gas structure of Xenon, to require extra stability.
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The standard reduction potential values of three metal cations Xa+, Yb+ and Zc+are + 0.52, – 3.03, – 1.18 V respectively. Arrange the corresponding metals, in the order of their increasing reducing power.
Answer:
The Standard reduction potential is the tendency for a chemical species to reduced and is measured in volts at standard condition the more is positive the potential is more likly it will reduced.
Yb+ > Zc+ > Xa+.
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Explain with the help of a diagram the effect of change in concentration of solution on the molar conductance of (i) a weak electrolyte, (ii) a strong electrolyte.
Λm increase a little in strong electrolyte because numbers of ions do not increase appreciably, only mobility of ions increases. Λm increases sharply in weak electrolyte because both number of ions and mobility of ions increases.
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With the halp of ionic equations describe what happen: When (i) pH of a solution of dichromate ions is raised. (ii) Potassium manganate is electro-chemically oxidised.
when pH is increased, i.e., solution is more basic, orange coloured dichromate ion change to yellow coloured chromate ion. When potassium manganate is electro-chemically oxidised i.e., undergoes, electrolytic oxidation, it forms purple colour KMnO4.
State two advantages of H2O fuel cell over ordinary cell.
Answer: The advantage of water fuel cell over ordinary cell is, (i) It has high-efficiency and eco-friendly. (ii) The H2O produced can be used by astronauts for drinking purposes.
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