Question

Arrange the following reducing agents in the order of increasing strength under standard state condition. Justify the answer.
`{:("Element",Al(s),Cu(s),Cl(aq),Ni(s)),(E^(@),-1.66V,0.34V,1.36V,-0.26V):}`

Answer 1

Given `Delta=-110kJ`
`DeltaS=40JK^(-1)` ltbr? `=0.04kjK^(-1)`
Temperature, `T=4000K`
`DeltaG=?`
Since `DeltaH` is -ve, the reaction is exothermic
`DeltaG=DeltaH-TDeltaS`
`=-110-400xx0*04`
`=-110-16`
`=-126kJ`
Since, `DeltaG` is negative, the reaction is spontaneous and exothermic.
(b) Given `DeltaH=40kJ`,
`Delta=-120JK^(-1)`
`=-0*12kJK^(-1)`
Temperature, `T=250K`
`DeltaG=?`
Since `DeltaH` is + ve reaction is endothermic
`DeltaG=DeltaH-T.DeltaS`
`=40-250xx(0*12)`
`=40+30`
`=70kJ`.
Sice `DeltaGgt0`, the reaction is non-spontaneous.
`DeltaG=70kJ`, The reaction is endothermic and non-spontaneous.