In electrochemical cell, would increasing the reactant increase the voltage?

[m25]

In electrochemical cell, would increasing the reactant increase the voltage?
Princeton review book says that in a battery, adding reagent such as Zn(s) does not increase the voltage at all, while TBR says that in galvanic cell, adding reactant such as Cu2+ would slightly increase the voltage.

So, is this discrepancy due to:

1) One of the book is wrong
2) adding reactant has no effect on battery(electrolytic) cell while adding reactant has effect on galvanic cell
3) adding a solid metal (that eventually gets oxidized) does not affect voltage whereas adding already oxidized metal(Cu2+) affects voltage ( perhaps because the oxidized metal is the limiting reagent in the reaction?)
4) because metal solid is not part of Nernst Equation: E=Estandard -(2.30RT/nF)logQ (solids are not included in quotient Q whereas oxidized metal such as(Cu2+) is included in Q)
5) something else that I am conceptually missing.

---

Members don't see this ad.

 

[davjan]

1) both book are right
2) it does according to Nernst equation: Ecell = Estanadard +RTln(Q)/nf
3) If you were to add a small block of solid Cu into the beaker of the electro-cell, it will not take part in reduction/oxidation. but if you were to attach the block to the Cu(s) electrode, it will participate in the reduction/oxidation since it will be connected to the readucing/oxidizing reagent.
4)you're right. Nernest tells you that Ecell depends on Q; and we don't include solids/liquids into Q since the activity is 1

5) it's just Nernest equation
Q=(non solid/liquid product)/(non solid/liquid reactant)
since, Cu(s) doesn't change Q, and Cu2+(aq) does, both books are right.