Assuming standard states for all reactants and products, determine the spontaneo

Question

Assuming standard states for all reactants and products, determine the spontaneous direction of each of the reactions below. Then, write the half-cell reactions at the anode and cathode, clearly label each: a. Cu + 2HCl = CuCl_2 + H_2 b. Fe + 2HCl = FeCl_2 + H_2 c. 2Zn + O_2 + 2H_2 O = 2Zn (OH)_2 Calculate the penetration rate in mpy equivalent to 1 uA/cm^2 for a Ti(+2, 47.8 g/mole) alloy containing 5% Al(+3, 27.0 g/mole) and 2.5% Sn(+2, 119 g/mole). Note, alloy density and EW are calculated in a similar manner as we discussed in class, e.g. 1/EW(alloy) = x1/EW(1) + x2/EW(2) + x3/EW(3) ... where x(i) is the mass fraction of each component.

Explanation / Answer

(a) Spontaneous in backward direction.

Anode half reaction is : H2 (g) ----------> 2 H+ (aq.) + 2e

Cathode Half Reaction: CuCl2 (aq.) ----------> Cu (s) + 2 Cl- (aq.)

(b) Spontaneous in forward direction

Anode Half Reaction: Fe (s) -------------> Fe2+ (aq.) + 2 e

Cathode Half Reaction: 2 HCl (aq.) + 2 e --------------> H2 (g) + 2 Cl- (aq.)

(c) Spontaneous in forward direction

Anode Half Reaction: Zn (s) -----------> Zn2+ (aq.) + 2 e

Cathode Half Reaction: O2 + 2H2O + 4 e ----------> 4 OH- (aq.)

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