Standard electrode potential values for `Al^(3+)//Al` is -1.66V and that of `Tl^(3+)//Tl` is +1.26. then,

Options

A. Aluminium is more electropositive than thallium
B. Aluminium is less electropositive than thallium
C. Both aluminium and thallium are equally electropositive
D. Cannot be predicted

Answer

To solve the problem, we need to analyze the standard electrode potential values provided for aluminum (Al) and thallium (Tl) and draw conclusions about their electropositivity based on these values.

### Step-by-Step Solution:

1. **Identify the Standard Electrode Potentials**:
- The standard electrode potential for the reaction \( Al^{3+} + 3e^- \rightarrow Al \) is given as \( -1.66 \, V \).
- The standard electrode potential for the reaction \( Tl^{3+} + 3e^- \rightarrow Tl \) is given as \( +1.26 \, V \).

2. **Interpret the Electrode Potentials**:
- A more negative electrode potential indicates that the species is less likely to be reduced (i.e., it is less stable in its reduced form).
- Conversely, a more positive electrode potential indicates that the species is more likely to be reduced (i.e., it is more stable in its reduced form).

3. **Analyze Aluminum**:
- For aluminum, the electrode potential of \( -1.66 \, V \) indicates that \( Al^{3+} \) is more stable than \( Al \). This means that aluminum readily loses electrons to form \( Al^{3+} \).

4. **Analyze Thallium**:
- For thallium, the electrode potential of \( +1.26 \, V \) indicates that \( Tl \) is more stable than \( Tl^{3+} \). This means that thallium does not readily lose electrons to form \( Tl^{3+} \).

5. **Compare the Stability of Ions**:
- Since \( Al^{3+} \) is more stable than \( Tl^{3+} \) (because \( -1.66 \, V \) is less than \( +1.26 \, V \)), aluminum is more electropositive than thallium. This is because aluminum can easily lose electrons to form \( Al^{3+} \), while thallium is less willing to lose electrons to form \( Tl^{3+} \).

6. **Conclusion**:
- Based on the analysis of the standard electrode potentials, we conclude that aluminum is more electropositive than thallium.

### Final Answer:
Aluminum is more electropositive than thallium.