In potash alum, the ratio of $K^+$ and $SO_4^{2-}$ ions is

Which of the following contain the same number of atoms?
$A$. $2 \text{ g}$ of $O_2$ gas
$B$. $4 \text{ g}$ of $SO_2$ gas
$C$. $1400 \text{ mL}$ of $O_2$ at $STP$
$D$. $0.05 \text{ L}$ of $He$ at $STP$
$E$. $0.0625 \text{ mol}$ of $H_2$ gas
Choose the correct answer from the options given below:

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:

If $10^{21}$ molecules are removed from $100 \, mg$ of $CO_2$,how many moles of $CO_2$ remain?

An organic compound contains $46.78 \%$ of a halogen $X$. When $2.00 \ g$ of this compound is heated with fuming $HNO_3$ in the presence of $AgNO_3$,$2.21 \ g$ of $AgX$ is formed. The halogen $X$ is:
[Given: atomic weight of $Ag = 108, F = 19, Cl = 35.5, Br = 80, I = 127$]

$0.45 \ g$ of an organic compound on combustion gives $0.792 \ g$ of $CO_2$ and $0.324 \ g$ of $H_2O$. In the Kjeldahl method,$0.24 \ g$ of the same compound yields ammonia,which is absorbed in $50 \ mL$ of $0.25 \ N \ H_2SO_4$. The excess acid requires $77.0 \ mL$ of $0.25 \ N \ NaOH$ for neutralization. Determine the empirical formula of the compound. (Atomic masses: $C = 12, H = 1, O = 16, N = 14, S = 32$)