Non-stoichiometric cuprous oxide, 'Cu_2 O' can be prepared in laboratory. In this oxide, Copper to oxygen ratio is slightly less than '2: 1 .' Can you account for the fact-that this substance is a p-type semiconductor?

Knowing the electron gain enthalpy values for O rarr O^- and O rarr O^2- as -141 and 702 ~kJ ~mol^-1 respectively, how can you account for the formation of a large number of oxides having O^ 2- species and not O^-

Calcium oxide (CaO) is used as dry- ing agent in the preparation of Am- monia in laboratory. Can concen- trated H_2SO_4 be used as drying agent instead of CaO? Justify your answer.

F centre is an example of metal excess defect due to the presence of extra cations at interstitial sites. Zinc oxide is white in colour at room temperature, on heating it loses oxygen and turns yellow. ZnO overset("Heat")toZn^(2+)+(1)/(2)O_(2)+2e^(-) Now there is excess of zinc in the crystal and its formula becomes Zn_(1+x) O. the excess of Zn^(2+) ions move to interstitial sites and the electrons to neighbouring interstitial sites. There are many solids which are difficult to prepare in the stiochiometric composition and contain less amount of the metal as compared to stiochiometric proportion. a typical example of this type is FeO which is mostly found with a composition of Fe_(0.95) . it may actually range from Fe_(0.96) O. Q. In Fe_(0.95) O:

Which of the following statements are correct? Fuel cells are galvanic cells in which the chemical energy of fuel is directly converted into electrical energy. Type of fuel cell is a hydrogen - oxygen fuel cell. It consists of two electrodes made up of two porous graphite impregnated with a catalyst (platinum, silver, or metal oxide). The electrodes are placed in aqueous solution of NaOH. Oxygen nad hydrogen are continuously fed into the cell. Hydrogen gets oxidized to H^(oplus) which is neutralized by overset(Θ)(OH) , ie., anodic reaction. H_(2) hArr 2H^(oplus) + 2e^(-) 2H^(oplus) + 2 overset(Θ)(OH) hArr 2H_(2)O H_(2) + 2 overset(Θ)(OH) hArr 2H_(2)O + 2e^(-) At cathode, O_(2) gets reduced to overset(Θ)(OH) i.e., O_(2) + 2H_(2)O + 4e^(-) hArr overset(Θ)(4)OH Hence, the net reaction is 2H_(2) + O_(2) hArr 2H_(2)O The overall reaction has Delta H= -285.6kJ mol^(-1) and Delta G= -237.4kJ mol^(-1) " at " 25^(@)C A fuel cell is I. A voltaic cell in which continuous supply of fuels are sent at anode to perform oxidation II. A voltaic cell in which fuels such as CH_(4), H_(2) and CO are used up at anode. III. One which involves the reaction of H_(2)- O_(2) fuel cell such as: Anode 2H_(2) + 4 overset(Θ)(OH) rarr 4H_(2)O(I) + 4e^(-) cathode : O+ 2H_(2)O(I) + 4e^(-) rarr 4 overset(Θ)(OH) IV. The efficiency of H_(2)-O_(2) fuel cell is 70 to 75%