An aqueous solution of borax is

What is $Z$ in the following reactions?

Which one of the following oxides dissolves in both hydrochloric acid and sodium hydroxide?

Diborane $(B_2H_6)$ reacts independently with $O_2$ and $H_2O$ to produce,respectively

Which of the following statements is not correct about diborane $(B_2H_6)$?

Given below are two statements:
Statement $I$: Aluminium is more electropositive than thallium as the standard electrode potential value of $E^\circ_{Al^{3+}/Al}$ is negative and $E^\circ_{Tl^{3+}/Tl}$ is positive.
Statement $II$: The sum of first three ionization enthalpies of boron is very high when compared to that of aluminium. Due to this reason,boron forms covalent compounds only and aluminium forms $Al^{3+}$ ion.