Which of the following pairs of oxoacids have a basicity of $2$?

Heating $(NH_4)_2Cr_2O_7$ produces a gas. This gas can also be obtained by:

Which statement is incorrect for nitric oxide $(NO)$?

Write a note on oxidation states of group $-15$ elements. Write a note on the nature of bonding of group $-15$ elements.

Ionic radius (in $\mathring{A}$) of $As^{3+}$,$Sb^{3+}$ and $Bi^{3+}$ follow the order:

Which of the following are the correct orders of stability of oxidation states of cations?
$(a) \ Pb^{+2} > Pb^{+4}, Tl^{+1} < Tl^{+3}$
$(b) \ Bi^{+3} < Sb^{+3}, Sn^{+2} < Sn^{+4}$
$(c) \ Pb^{+2} > Pb^{+4}, Bi^{+3} > Bi^{+5}$
$(d) \ Tl^{+3} < In^{+3}, Sn^{+2} > Sn^{+4}$
$(e) \ Sn^{+2} < Pb^{+2}, Sn^{+4} > Pb^{+4}$
$(f) \ Sn^{+2} < Pb^{+2}, Sn^{+4} < Pb^{+4}$