At high temperatures,which of the following are present?

Dry air is passed through a solution containing $10 \ g$ of solute and $90 \ g$ of water,and then it is passed through pure water. The loss in weight of the solution is $2.5 \ g$ and the loss in weight of the pure solvent is $0.05 \ g$. Calculate the molecular weight of the solute.

$\int \tan ^{-1}\left(\sqrt{\frac{1-x}{1+x}}\right) d x$ is equal to

Which of the following is not produced during the electrolysis of brine solution?

If $[x]$ denotes the greatest integer not exceeding $x$ and if the function $f$ defined by $f(x)= \begin{cases} \frac{a+2 \cos x}{x^2} & , x < 0 \\ b \tan \frac{\pi}{[x+4]} & , x \geq 0 \end{cases}$ is continuous at $x=0$,then the ordered pair $(a, b)$ is equal to

Example of a biodegradable polymer pair is