19.已知φθ(Br2/Br-)=1.07 V,φθ(Cu2+/Cu)=0.34 V,则反应Br2 + Cu = 2Br- + Cu2+构成的原电池的标准电池电动势Eq 为1.0.73 V 2.1.80 V 3.-0.73 V 4.-0.39 V20.已知φθ(Sn2+/Sn) = -0.138 V,φθ(Cu2+/Cu) = 0.342 V,φθ(Fe2+/Fe) = -0.447 V,φθ(Ag+/Ag) = ...