Which of the following substances cannot be analyzed using the Kjeldahl method for the estimation of nitrogen?

Which method is used for the estimation of nitrogen 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 $\%$)

For which of the following compounds can the Kjeldahl method be used to determine the percentage of nitrogen?

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

$A$ sample of $0.50 \, g$ of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in $50 \, mL$ of $0.5 \, M \, H_{2}SO_{4}$. The residual acid required $60 \, mL$ of $0.5 \, M \, NaOH$ solution for neutralisation. Find the percentage composition of nitrogen in the compound. (in $\%$)