$2.18 \ g$ of an organic compound containing sulphur produces $0.12 \ g$ of $BaSO_4$. The percentage of sulphur in the compound is?

$A$ student has been given $0.314 \ g$ of an organic compound and asked to estimate Sulphur. During the experiment, the student has obtained $0.4813 \ g$ of barium sulphate. The percentage of sulphur present in the compound is . . . . . .
(Given Molar mass in $g \ mol^{-1}$: $S = 32$, $BaSO_4 = 233$) (in $\%$)

$0.3 \ g$ of an organic compound gave $50 \ mL$ of nitrogen collected at $300 \ K$ and $715 \ mm$ pressure in Dumas method. Calculate the percentage of nitrogen in the compound (aqueous tension of water at $300 \ K$ is $15 \ mm$).

What is the reason for passing dry air through the combustion tube during the estimation of $C$ and $H$?

In Dumas's method for estimation of nitrogen,$0.25 \, g$ of an organic compound gave $40 \, mL$ of nitrogen collected at $300 \, K$ temperature and $725 \, mm$ pressure. If the aqueous tension at $300 \, K$ is $25 \, mm,$ the percentage of nitrogen in the compound is

$1.2 \ g$ of an organic compound on Kjeldahlization liberates ammonia which consumes $30 \ cm^3$ of $1 \ N \ HCl$. The percentage of nitrogen in the organic compound is: