Which are two chemicals used to purify water? sulfur and oxygen fluorine and sodium bicarbonate and calcium ozone and chlorine

1. combine iron and copper (ii) sulfate solution. (hint: iron will form the iron (iii) ion) fe + cuso4 → 2. combine lead (ii) nitrate and potassium iodide solutions. pb(no3)2+ kl → 3. combine magnesium metal and hydrochloric acid solution. mg + hcl → 4. electrolysis (splitting) of water. h2o → 5. burning magnesium. mg + o2 →

Can someone me with these questions plz.

Fill in the coefficients that will balance the following reaction: a0cr2(so4)3 + a1agno3