The element which catches fire in air at $30^o\,C$ and is stored under water is

Which of the following is used as an anesthetic?

Anhydrous $AlCl_3$ is formed in

Given below are the two statements: one is labeled as Assertion $(A)$ and the other is labeled as Reason $(R)$.
Assertion $(A)$: There is a considerable increase in covalent radius from $N$ to $P$. However,from $As$ to $Bi$,only a small increase in covalent radius is observed.
Reason $(R)$: Covalent and ionic radii in a particular oxidation state increase down the group.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following is obtained by catalytic oxidation of ammonia?

Which of the following orders is correct?