Identify the double displacement reaction from the following.
(i) 2AgCl(s) → 2Ag(s) + Clâ‚‚(g)
(ii) Mg(s) + 2HCl(aq) → MgClâ‚‚(aq) + Hâ‚‚(g)
(iii) 2KBr(aq) + BaIâ‚‚(aq) → 2KI(aq) + BaBrâ‚‚(s)
(iv) Pb(s) + CuClâ‚‚(aq) → PbClâ‚‚(aq) + Cu(s)
The positive square root of (34² − 16²) is: