At 73.0 ∘c, what is the maximum value of the reaction quotient, q, needed to produce a non-negative e value for the reaction so42 - (aq) + 4h + (aq) + 2br - (aq) ⇌br2 (aq) + so2 (g) + 2h2o (l) in other words, what is q when e=0 at this temperature?

Here we will use the general formula of Nernst equation:

Ecell = E°Cell - [ (RT/nF) ] * ㏑Q

when E cell is cell potential at non - standard state conditions

E°Cell is standard state cell potential = - 0.87 V

and R is a constant = 8.314 J/mol K

and T is the temperature in Kelvin = 73 + 273 = 346 K

and F is Faraday's constant = 96485 C/mole

and n is the number of moles of electron transferred in the reaction=2

and Q is the reaction quotient for the reaction

SO42-2 (aq) + 4H + (aq) + 2Br - (aq) ↔ Br2 (aq) + SO2 (g) + 2H2O (l)

so by substitution:

0 = - 0.87 - [ (8.314*346K) / (2 * 96485) * ㏑Q → solve for Q

∴ Q = 4.5 x 10^-26