Molar mass of the salt from NaBr , NaNO 3 , KI and CaF 2 which does not evolve coloured vapours on heating…

On heating $\mathrm{NaBr}$ with concentrated sulphuric acid gives brown colour bromine vapours.

On heating ${\mathrm{NaNO}}_3$ with concentrated sulphuric acid will release a brown colour ${\mathrm{NO}}_2$ gas 

On heating ${\mathrm{I}}^{-}$ with concentrated sulphuric acid gives a dark purple colour.

On heating with concentrated sulphuric acid with ${\mathrm{CaF}}_2$ does not give any colour because it produces colourless hydrogen fluoride.Molar mass of ${\mathrm{CaF}}_2$ is $78.07 \mathrm{g}/\mathrm{mol}$