Problem

Which of the following solid salt on heating with solid

\text{K}_2\text{Cr}_2\text{O}_7

and conc.

\text{H}_2\text{SO}_4

orange red vapours are evolved which turn aqueous

\text{NaOH}

solution yellow ? a.

\text{NaBr}

\text{NaCl}

\text{NaNO}_3

\text{NaI}