Q40. The emf of cell $\mathrm { Tl } \left| \underset { ( 0.001 \mathrm { M } ) } { \mathrm { Tl } ^ { + } } \right| \left| \underset { ( 0.01 \mathrm { M } ) } { \mathrm { Cu } ^ { 2 + } } \right| \mathrm { Cu }$ is 0.83 V at 298 K . It could be increased by :\\
(1) decreasing concentration of both $\mathrm { Tl } ^ { + }$and $\mathrm { Cu } ^ { 2 + }$\\
(2) increasing concentration of $\mathrm { Cu } ^ { 2 + }$ ions ions\\
(3) increasing concentration of $\mathrm { T } 1 ^ { + }$ions\\
(4) increasing concentration of both $\mathrm { Tl } ^ { + }$and $\mathrm { Cu } ^ { 2 + }$ ions