Question

1(b)(iii) A standard galvanic cell constructed with Ag⁺(aq)/Ag(s) and Zn²⁺(aq)/Zn(s) couple is discharged until 3.3g of Ag forms. I. Write the overall cell reaction and standard cell potential. II. How many moles of electrons flowed through the circuit during the discharge? III. How many coulombs of charges flowed through the circuit?
Ag⁺(aq)+e⁻⇌Ag(s); E°=+0.80V
Zn²⁺(aq)+2e⁻⇌Zn(s); E°=-0.76V [Ag=108]

Accepted Answer

I. Overall cell reaction: Zn+2Ag⁺→Zn²⁺+2Ag. Cell notation: Zn/Zn²⁺//Ag⁺/Ag. E°=E°red(right)-E°red(left) = (+0.80V)-(-0.76V) = +1.56V.
II. Ag⁺+e⁻→Ag(s): 1 mole of Ag (108g) requires 1 mole of electrons. Since mass produced = 3.3g, moles of electrons = (1/108) x 3.3 = 0.03 moles of electrons.
III. Amount of electricity: 1e⁻ = 1F = 96500C. Thus 0.03e⁻ = 0.03F = 0.03 x 96500 = 2895 C.

WAEC Chemistry 2011 Theory — Question 4

Sign up free to unlock