Molar mass of the salt from NaBr, NaNO_3$NaNO_3$, KI and CaF_2$CaF_2$ which does not evolve coloured vapours on heating with concentrated H_2SO_4$H_2SO_4$ is ________ textg mol^-1$\text{g } mol^{-1}$. (Molar mass in textg mol^-1$\text{g } mol^{-1}$: Na: 23, N: 14, K: 39, O: 16, Br: 80, I: 127, F: 19, Ca: 40)

### Step 1: Analyzing the reactions with Concentrated H2SO4 NaBr xrightarrowtextconc. H_2SO_4 Br_2$NaBr \xrightarrow{\text{conc. } H_2SO_4} Br_2$ (Reddish-brown vapour evolves) NaNO_3 xrightarrowtextconc. H_2SO_4 NO_2$NaNO_3 \xrightarrow{\text{conc. } H_2SO_4} NO_2$ (Brown vapour evolves) KI xrightarrowtextconc. H_2SO_4 I_2$KI \xrightarrow{\text{conc. } H_2SO_4} I_2$ (Violet vapour evolves) CaF_2 xrightarrowtextconc. H_2SO_4 HF$CaF_2 \xrightarrow{\text{conc. } H_2SO_4} HF$ (Colorless vapour evolves) Thus, CaF_2$CaF_2$ does not evolve colored vapours. ### Step 2: Calculating Molar Mass Molar mass of CaF_2$CaF_2$: Ca = 40$Ca = 40$ F_2 = 2 times 19 = 38$$F_2 = 2 \times 19 = 38$$ textMolar mass = 40 + 38 = 78 text g/mol$$\text{Molar mass} = 40 + 38 = 78 \text{ g/mol}$$ ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Salt Analysis