Question

Consider the following standard electrode potentials (E° in volts) in aqueous solution:

Element	M3+/M	M+/M
Al	- 1.66	+0.55
Tl	+ 1.26	-0.34

Based on these data, which of the following statements is correct?

Options

• Tl⁺ is more stable than Al³⁺

• Al⁺ is 'more stable than Al³⁺ 

• TI⁺ is more stable than Al³⁺

• Tl³⁺ is more stable than Al³⁺

Answer 1

TI⁺ is more stable than Al³⁺

Explanation:

(i) \[\ce{\underset{Most stable}{Al^{3+}} ->[E° = - 1.66] Al <-[E° = +0.55] \underset{Less stable}{Al+}}\]

(ii) \[\ce{\underset{Less stable}{Tl^{3+}} ->[E° = + 1.26] Tl <-[E° = -0.34] \underset{More stable}{Tl+}}\]

Tl⁺ has negative electrode potential (E° = - 0.34) means, it does not prefer to convert into Tl but reverse must be preferred that's why it is more stable than Tl³⁺ (E° = + 1.26). In Al,  Al³⁺ is more stable (E° = - 1.66) than Al⁺ (E° = +  0.55) and also from Tl⁺ due to more negative value of E°. Therefore, by comparison it confirms that Tl⁺ is more stable than Al⁺.