Which one of the following is not a colourless compound?

What is the number of hydroxyl groups in pyrophosphoric acid?

Red phosphorus is less reactive than yellow phosphorus because

Which of the following oxides of nitrogen is a mixed anhydride of two acids?

The total number of paramagnetic gaseous products formed in all the following reactions $[A + B + C ]$:
$(A)\ NH_4 NO_3 \xrightarrow{\Delta} \text{Products}$
$(B)\ 3 NaNO_2 + 3 H_2 SO_4 \longrightarrow \text{Products}$
$(C)\ Pb(NO_3)_2 \xrightarrow{673 \ K} \text{Products}$

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