At 298 K

$$\mathrm{N_2~(g)+3H_2~(g)\rightleftharpoons~2NH_3~(g),~K_1=4\times10^5}$$

$$\mathrm{N_2~(g)+O_2~(g)\rightleftharpoons~2NO~(g),~K_2=1.6\times10^{12}}$$

$$\mathrm{H_2~(g)+\frac{1}{2}O_2~(g)\rightleftharpoons~H_2O~(g),~K_3=1.0\times10^{-13}}$$

Based on above equilibria, then equilibrium constant of the reaction, $$\mathrm{2NH_3(g)+\frac{5}{2}O_2~(g)\rightleftharpoons~2NO~(g)+3H_2O~(g)}$$ is ____________ $$\times10^{-33}$$ (Nearest integer).

The denticity of the ligand present in the Fehling's reagent is ___________.

When 0.01 mol of an organic compound containing 60% carbon was burnt completely, 4.4 g of CO$$_2$$ was produced. The molar mass of compound is _____________ g mol$$^{-1}$$ (Nearest integer).

Total number of acidic oxides among

$$\mathrm{N_2O_3,NO_2,N_2O,Cl_2O_7,SO_2,CO,CaO,Na_2O}$$ and $$\mathrm{NO}$$ is ____________.