The pair of compounds that can not exist together is(i) FeCl3, SnCl2(ii) HgCl2, SnCl2(iii) FeCl2, SnCl2(iv) FeCl3 , KI

(i) FeCl3, SnCl2  Fe+3     +    Sn+2  →  Fe+2 +Sn+4Oxidant    reductant FeCl2 & SnCl2 react with each other they cannot exist together(ii) HgCl2, SnCl2    Hg+2   +    Sn+2    →   Hg+ + Sn+4oxidant      reductant HgCl2 & SnCl2 react with each other they cannot exist together(iii) FeCl2, SnCl2Fe+2 + Sn+2 → no reaction(iv) FeCl3 , KI    Fe+3    +    I-       →   Fe+2 + I2Oxidant    reductant Fe+3 & I- react with each other they cannot exist together I,II,IV  cannot exist