When a standard solution of $NaOH$ is left in air for a few hours,

What volume of $NH_3$ gas at $STP$ would be needed to prepare $100 \ mL$ of $2.5$ molal $(2.5 \ m)$ ammonium hydroxide solution? (Assume the density of the solution is $1 \ g/mL$)

$100 \ mL$,$1 \ M$ $H_2SO_4$ solution of density $1.5 \ g/mL$ is mixed with $400 \ mL$ of water,resulting in a diluted solution of density $1.25 \ g/mL$. Find the molarity of the final diluted solution. (Density of water $= 1 \ g/mL$)

When water is added to quick lime,the reaction is

Green compound $(A)$ on decomposition gives gases $(B)$ and $(C)$ along with a red-brown residue. $(B)$ and $(C)$ are acidic oxides of sulphur. Gas $(B)$ gives a positive test with $KMnO_4$.
$(C) + H_2SO_4 \to (D)$ $\xrightarrow{+ [O]} (E)$ $\xrightarrow{2H_2O} (F) + H_2SO_4$
$(F)$ $\xrightarrow{K_3[Fe(CN)_6] / KOH} (G)$ $\xrightarrow{Conc. H_2SO_4} (H) \text{ (Neutral oxide, poisonous)}$
Total number of $\sigma$ bonds in $(E)$ is:

$A$ gas has a density of $2.68 \ g/L$ at $STP$. Identify the gas.