Which of the following oxides does not give any oxyacid in aqueous solution?

The total number of compounds having at least one bridging oxo group among the molecules given below is. . . . . . .
$N_2O_3, N_2O_5, P_4O_6, P_4O_7, H_4P_2O_5, H_5P_3O_{10}, H_2S_2O_3, H_2S_2O_5$

Phosphorous and phosphoric acids are, respectively, . . . . . . acids.

Which gas is used in the manufacturing of nitrogenous fertilizers?

Consider two reactions:
$(I) \, Zn + \text{conc. } HNO_3 \text{ (hot)} \to Zn(NO_3)_2 + X + H_2O$
$(II) \, Zn + \text{dil. } HNO_3 \text{ (cold)} \to Zn(NO_3)_2 + Y + H_2O$
Compound $X$ and $Y$ are respectively:

The element that can form multiple bonds with itself from the following is