Which of the following salts does not impart color to the flame?

(Milky Cloud) $C \xleftarrow{CO_2} A + Na_2CO_3 \rightarrow B + C$
The chemical formulae of $A$ and $B$ are

Fill in the blanks:
$(1)$ Lithium on reaction with nitrogen present in air is denoted by .....
$(2)$ Potassium gives ...... colour in oxidizing flame.
$(3)$ ....... and ........ metals are used in photoelectric cells.
$(4)$ When alkali metal dissolves in ammonia,it produces a blue-coloured solution. This colour is due to .......

Which of the following is the chemical formula for dolomite?

Chemically,philosopher's wool is

Which alkali metal during flame test will show color corresponding to maximum wavelength?