In Dumas method for estimation of nitrogen,$0.3 \ g$ of an organic compound gave $41.9 \ mL$ of nitrogen gas at $\text{STP}$. What is the percentage of nitrogen (in $.5$)?

In Kjeldahl's method for estimation of nitrogen,$CuSO_4$ acts as :

Why is a solution of potassium hydroxide used to absorb carbon dioxide evolved during the estimation of carbon present in an organic compound?

$A$ 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 $\%$)

In the sulphur estimation,$0.471 \, g$ of an organic compound gave $1.44 \, g$ of barium sulphate. The percentage of sulphur in the compound is $...... \%$. (Nearest integer)
(Atomic Mass of $Ba=137 \, u$)

Calculate the percentage of nitrogen in $0.25 \ g$ of an organic compound if $38 \ cm^3$ of $N_2$ gas is evolved at $300 \ K$ and $96 \ kPa$ pressure. (Given: $1 \ atm = 101.3 \ kPa$)