(a)How do you prepare : (i)K_(2)MnO_(4) from MnO_(2) (ii) Na_(2)Cr_(2)O_(7)from Na_(2)CrO_(4)? (b)Account for the following : (i) Mn^(2+) is more stable than Fe^(2+) towards oxidation to +3 state. (ii) The enthalpy of atomisation is lowest for Zn in 3d series of transition elements. (iii) Actinoid elementsshow widerange of oxidation states. or(i) Namethe elements of 3d transition series whichshows maximum number of oxidation states. Why dows itshow so ? (ii)Which transition element of 3d series has positiveE_(M^(+)//M)^(@) value and why ? (iii)Out of Cr^(3+) and Mn^(3+) which is stronger oxidizing agent and why ? (iv) Name a member of the lanthanoidseries which is well knownto exhibit +2oxidation state. (v)Complete the equation :MnO_(4)^(-) +8 H^(+) + 5e^(-) rarr

(a)How do you prepare : (i)K_(2)MnO_(4) from MnO_(2) (ii) Na_(2)Cr_(2

1.	(a)How do you prepare : (i)K_(2)MnO_(4) from MnO_(2) (ii) Na_(2)Cr_(2)O_(7)from Na_(2)CrO_(4)? (b)Account for the following : (i) Mn^(2+) is more stable than Fe^(2+) towards oxidation to +3 state. (ii) The enthalpy of atomisation is lowest for Zn in 3d series of transition elements. (iii) Actinoid elementsshow widerange of oxidation states. or(i) Namethe elements of 3d transition series whichshows maximum number of oxidation states. Why dows itshow so ? (ii)Which transition element of 3d series has positiveE_(M^(+)//M)^(@) value and why ? (iii)Out of Cr^(3+) and Mn^(3+) which is stronger oxidizing agent and why ? (iv) Name a member of the lanthanoidseries which is well knownto exhibit +2oxidation state. (v)Complete the equation :MnO_(4)^(-) +8 H^(+) + 5e^(-) rarr
Answer» Solution :(i) MN, (ii)Cu,(ii) `Mn^(3+)`,`(E_(M^(+)//Mn^(2+))^(@)= + 1.57V)` (iv)`EU^(2+)` due to exactly half FILLED `f^(7)` configurationand `Yb^(2+)` due to completely filled `f^(14)` configuration(v) `MnO_(4)^(-) +8 H^(+)+ 5e^(-) rarr Mn^(2+)4H_(2)O)`