Name the anion

You will write three functions that name an anion from what is seen. The observations are stored in a dictionary with three keys. The key "dilute" holds the gas with dilute sulphuric acid ("CO2", "H2S", "SO2", "NO2", "vinegar") or None. The key "conc" holds the vapour with concentrated sulphuric acid ("HCl", "brown", "violet") or None. The key "bacl2_in_hcl" is True when barium chloride gives a white precipitate that stays in dilute hydrochloric acid.

The idea. First try the dilute acid test. If it gives nothing, try the concentrated acid test. Sulphate is last, because it gives no gas.

Your tasks.

1. Complete dilute_acid(gas). It returns the anion from the table DILUTE, or None.
2. Complete conc_acid(vapour). It returns the anion from the table CONC, or None.
3. Complete anion(obs). It tries the dilute acid, then the concentrated acid, then the sulphate test, and returns "unknown" if nothing fits.