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Class : XIIth Subject : CHEMISTRY Date : DPP No. : 1 1 (c) Al →Al3+ + 3e ― The charge required = 3 × 96500 C 2 (b) Eq. of H2 = Eq. of Cu ∴ 0.504 1 = W 63.5/2 ∴ WCu = 16 g 3 (a) E° = 0.059 n logKeq and ∆G° = ― nE°F ∴ ∆G° = +ve, E° will be ― ve and Keq < 1; one should not write ∆G° > 0. 4 (d) E ° cell = 0.87 + 0.40 = 1.27 V Cell reaction :Fe + Ni2O3→FeO + 2NiO 5 (a) The given values areE ° RP. More is E ° RP more is the tendency to gain electron or to show reduction or to show strong oxidant nature. 6 (d) E ° cell = E ° OPSn +E ° RPFe = 0.14 + (⎯0.44) = ―0.30 V 8 (a) Smallest ion possesses maximum mobility. 9 (a) Λ 0 M = Λ 0 a + Λ 0 c 10 (c) Molten NaCl possesses Na + and Cl ― ions. 11 (a) Given, that Zn / Zn2+ || Cu2+ / Cu ∴ Zn is anode and Cu is cathode. Topic :- Electro Chemistry Solutions
Given, Zn2+/ Zn = ― 0.76 V Cu2+ / Cu = + 0.34 V Ecell = Ecathode ― Eanode = 0.34 – (- 0.76) = 0.34 + 0.76 = 1.10 V 12 (a) Net redox change is zero. 13 (a) Cathode 2H2O + 2e ―→H2 +2OH― Anode : H2O→2H + + 1 2 O2 +2e ― 14 (d) More is E ° OP, more is reducing power of metal. 15 (b) The charge required to liberate one gram equivalent of an element is always equal to 1 faraday (i.e., = 96500 C). 16 (c) pH < 7; Aqueous solution of CuSO4 is acidic in nature. Furthermore some drops of H2SO4 is also added during electrolysis. 17 (a) Anode is positive electrode and cathode is –ve electrode in electrolytic cell whereas, anode is –ve electrode and cathode is +ve electrode in electrochemical cells. 18 (c) △ G = △ H ― T △ S For a spontaneous cell reaction, △ H should be negative and △ S should be positive. Hence, △ G should be negative. 19 (a) Cell reaction is Mg + Sn2+→Mg2+ +Sn Ecell = E ° cell ― 0.0591 2 log [Mg2+] [Sn 2+] = (2.34 ― 0.14) ― 0.0591 2 log 10―2 10―1 = 2.23 V 20 (a) pH of solution increases due to formation of LiOH or due to increase in [OH ―] because H + ions are discharged at cathode in preference to Li + .
ANSWER-KEY Q. 1 2 3 4 5 6 7 8 9 10 A. C B A D A D D A A C Q. 11 12 13 14 15 16 17 18 19 20 A. A A A D B C A C A A