Standard reduction potentials (V): Mg^2+/Mg = -2.37, Al^3+/Al = -1.66, Zn^2+/Zn = -0.76, Fe^2+/Fe = -0.44, Ni^2+/Ni = -0.25, Cu^2+/Cu = +0.34, Ag+/Ag = +0.80, Hg^2+/Hg = +0.85, Pt^2+/Pt = +1.20, Au^3+/Au = +1.50. The number of metals from the list Mg, Al, Zn, Fe, Ni, Ag, Hg, Pt, Au that can displace copper from aqueous CuSO4 under standard conditions is

JEE Main levelNumerical answerDifficulty 2 of 3ec042

Standard reduction potentials (V): $Mg X^{2 +} / Mg = - 2.37$ , $Al X^{3 +} / Al = - 1.66$ , $Zn X^{2 +} / Zn = - 0.76$ , $Fe X^{2 +} / Fe = - 0.44$ , $Ni X^{2 +} / Ni = - 0.25$ , $Cu X^{2 +} / Cu = + 0.34$ , $Ag X^{+} / Ag = + 0.80$ , $Hg X^{2 +} / Hg = + 0.85$ , $Pt X^{2 +} / Pt = + 1.20$ , $Au X^{3 +} / Au = + 1.50$ . The number of metals from the list Mg, Al, Zn, Fe, Ni, Ag, Hg, Pt, Au that can displace copper from aqueous $CuSO X_{4}$ under standard conditions is

Numerical answer type.

A metal M displaces Cu if

E^{\circ} (M X^{n +} / M) < E^{\circ} (Cu X^{2 +} / Cu) = 0.34 V

, i.e. M lies below Cu in the electrochemical series. Mg, Al, Zn, Fe and Ni satisfy this. Ag, Hg, Pt and Au have higher potentials and cannot reduce

Cu X^{2 +}

. The count is 5.