Q13 of 30 Page 1

(a) Which solution is used for the leaching of silver metal in the presence of air in the metallurgy of silver?

(b) Out of C and CO, which is a better reducing agent at the lower temperature range in the blast furnace to extract iron from the oxide ore?


(a) In the metallurgy of silver, a dilute solution (0.5%) of NaCN or KCN is used for leaching of silver metal in the presence of air.


(b) Out of C and CO, CO is a better reducing agent at the lower temperature range because, in the Ellingham diagram, the plot between ΔG and T, shows that the Gibbs free energy of CO and CO2 line lies below to that of Fe and FeO line.


ΔG(CO,CO2) < ΔG(Fe, FeO)


So, CO will reduce FeO to Fe, and will itself be oxidized to CO2.



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Write the dispersed phase and dispersion medium of the following colloidal systems:

(i) Smoke


(ii) Milk


OR


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Write the differences between physisorption and chemisorption with respect to the following:

(i) Specificity


(ii) Temperature dependence


(iii) Reversibility and


(iv) Enthalpy change


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What happens when

(i) PCl5 is heated?


(ii) H3PO3 is heated?


Write the reactions involved.


 15

(a) Which metal in the first transition series (3d series) exhibits + 1 oxidation state most frequently and why?

(b) Which of the following cations are coloured in aqueous solutions and why?


Sc3+, V3+, Ti4+,Mn2+


(At. nos. Sc= 21, V = 23, Ti = 22, Mn= 25)