Galena (an ore) is partially oxidized by passing air through it at high temperature. After some time, the passage of air is stopped, but the heating is continued in a closed furnace such that the contents undergo self-reduction. The weight (in kg) of $$Pb$$ produced per kg of $${O_2}$$ consumed is ___________.

(Atomic weights in $$g\,mo{l^{ - 1}}:O = 16,S = 32,Pb = 207$$)

The correct option(s) to distinguish nitrate salts of $$M{n^{2 + }}$$ and $$C{u^{2 + }}$$ taken separately is (are)

The total number of compounds having at least one bridging oxo group among the molecules given below is _________.

$${N_2}{O_3},{N_2}{O_5},$$ $${P_4}{O_6},{P_4}{O_7},$$ $${H_4}{P_2}{O_5},{H_5}{P_3}{O_{10}},$$ $${H_2}{S_2}{O_3},{H_2}{S_2}{O_5}$$

The correct option(s) regarding the complex

$${\left[ {Co\left( {en} \right){{\left( {N{H_3}} \right)}_3}\left( {{H_2}O} \right)} \right]^{3 + }}\,\,$$ $$\left( {en = {H_2}NC{H_2}C{H_2}N{H_2}} \right)$$ is (are)