UPSC  Chemistry

31. Which of the following statements is incorrect?

In K4 [Fe(CN)6], the ligand has satisfied both primary and secondary valencies of ferrous ion. In [Cu(NH3)4]SO4, the ligand has satisfied only the secondary valency of copper. In K3[Fe(CN)6] , the ligand has satisfied only the secondary valency of ferric ion. In K3[Fe(CN)6], the ligand has satisfied both primary and secondary valencies of ferric ion

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32. A solution containing 2.675 g of CoCl3 · 6NH3 (molar mass = 267.5 g mol–1) is passed through a cation exchanger. The chloride ions obtained in solution were treated with excess of AgNO3 to give 4.78 g of agcl (molar mass = 143.5 g mol–1). The formula of the complex is
(At. Mass of Ag = 108 u)

[Co(NH3)6]Cl3 [CoCl2(NH3)4]Cl [CoCl3(NH3)3] [CoCl(NH3)5]Cl2

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33. Consider the reaction :
4NO2(g) + O2(g) ® 2N2O5(g), ΔrH = –111kJ.
If N2O5(s) is formed instead of N2O5(g) in the above reaction, the ΔrH value will be:
(given, ΔH of sublimation for N2O5 is 54 kJ mol–1)

–219 kJ –165 kJ + 54 kJ + 219 kJ

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34. The standard enthalpy of formation of NH3 is –46.0 kJ mol–1. If the enthalpy of formation of H2 from its atoms is –436 kJ mol–1 and that of N2 is –712 kJ mol–1, the average bond enthalpy of N — H bond is NH3 is

–1102 kJ mol–1 –964 kJ mol–1 +352 kJ mol–1 +1056 kJ mol–1

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35. An ideal gas is allowed to expand both reversibly and irreversibly in an isolated system. If Ti is the initial temperature and Tf is the final temperature, which of the following statements is correct?

(Tf)irrev > (Tf)rev Tf > Ti for reversible process but Tf = Ti for irreversible process (Tf)rev = (Tf)irrev Tf = Ti for both reversible and irreversible processes

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36. The standard enthalpy of formation (ΔfH°) at 298 K for methane, CH4(g), is –74.8 kJ mol–1. The additional information required to determine the average energy for C – H bond formation would be

the dissociation energy of H2 and enthalpy of sublimation of carbon latent heat of vaporization of methane the first four ionization energies of carbon and electron gain enthalpy of hydrogen the dissociation energy of hydrogen molecule, H2

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