Question

At 63.0 C , what is the maximum value of the reaction quotient, Q, needed to produce a non-negative Ecell value for the reaction

SO₄²⁻(aq)+4H⁺(aq)+2Br⁻(aq)⇌Br₂(l)+SO₂(g)+2H₂O(l)

In other words, what is Q when Ecell=0 at this temperature?

Answer 1

The maximum value of the reaction quotient, Q, that results in a non-negative Ecell value occurs when Ecell=0, which indicates equilibrium. At this point, Q equals the equilibrium constant K, calculated using the Nernst equation modified to reflect equilibrium conditions.

Step-by-step explanation:

You are asking what the maximum value of the reaction quotient, Q, is needed to produce a non-negative Ecell value for a given reaction at 63.0 °C, in other words, what is Q when Ecell=0 at this temperature. To determine this value, we need to apply the Nernst equation where Ecell is given by:

Ecell = E°cell - (RT/nF)lnQ

At the point where Ecell equals zero, Q equals the equilibrium constant K, because, at Ecell = 0, no net reaction is occurring, and the system is at equilibrium. The Nernst equation at this point simplifies to:

0 = E°cell - (RT/nF)lnK

Solving for K (and therefore Q when Ecell = 0), we rearrange the equation to get:

lnK = (nFE°cell)/(RT)

Given that 'n' is the number of electrons transferred in the reaction, 'F' is Faraday's constant (96485 C/mol), 'R' is the universal gas constant (8.314 J/mol·K), 'T' is the temperature in Kelvin, and E°cell is the standard electromotive force of the cell. To solve for Q at 63.0 °C, we need the E°cell value for the specific reaction, convert the temperature to Kelvin, and then apply the equation.