The chemical used for cooling in refrigeration is

Which blue-colored liquid is obtained upon reacting equimolar amounts of two gases at $-30\,^{\circ}C$?

Which pair of oxyacids of phosphorus contains $P-H$ bonds?

Given below are two statements $:$
Statement $I :$ Nitrogen forms oxides with $+1$ to $+5$ oxidation states due to the formation of $p\pi-p\pi$ bond with oxygen.
Statement $II :$ Nitrogen does not form halides with $+5$ oxidation state due to the absence of $d$-orbital in it.
In the light of given statements,choose the correct answer from the options given below.

Which one of the following cannot form an amphoteric oxide?

Thallium shows different oxidation states because