Chlorine gas reacts with red hot calcium oxide to give

Gold dissolves in aqua regia forming:

In which of the following is silica $(SiO_2)$ soluble?

What is the final chemical form of Gold $(Au)$ when it is dissolved in aqua-regia?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A :$ Fluorine forms one oxoacid.
Reason $R :$ Fluorine has the smallest size amongst all halogens and is highly electronegative.
In the light of the above statements,choose the most appropriate answer from the options given below.

When chlorine gas is passed through an aqueous solution of a potassium halide in the presence of chloroform,a violet colouration is obtained. On passing more of chlorine water,the violet colour disappears and the solution becomes colourless. This test confirms the presence of ........... in the aqueous solution.