Identify the salt (X) which when treated with ${\mathrm{K}}_2{\mathrm{CrO}}_4$ in the presence of dil. acetic acid, a yellow ppt. is obtained. Salt (X) produces green flame in the flame test :

Barium chloride when treated with ${\mathrm{K}}_2{\mathrm{CrO}}_4$ in the presence of dilute acetic acid, a yellow precipitate is obtained additionally barium chloride produces a green flame in the flame test. Because barium emits light with a wavelength that corresponds to green, it emits that colour.