The electrochemical cell described by the balanced chemical equation has a standard emf (electromotive force) of -0.35 V. Calculate the value (J) for the Wmax that the cell can do under standard conditions. Round your answer to 3 significant figures.
2MnO4-(aq) + Hg22+(aq) → 2MnO42-(aq) + 2Hg2+(aq)
To calculate the maximum work (Wmax) that an electrochemical cell can do under standard conditions, you can use the equation:
Wmax = -nFEcell
Where:
- Wmax is the maximum work done by the cell (in Joules)
- n is the number of moles of electrons transferred in the balanced equation (from the stoichiometric coefficients)
- F is the Faraday constant, which is 96,485 C/mol (coulombs per mole)
- Ecell is the cell potential (in volts)
First, let's find the number of moles of electrons transferred (n) in the balanced equation:
2MnO4-(aq) + Hg22+(aq) → 2MnO42-(aq) + 2Hg2+(aq)
From the equation, we can see that 2 moles of electrons are transferred per balanced equation. Therefore, n = 2.
Now, we need to convert the standard emf (Ecell) from volts to joules. The conversion factor is 1 J/C, which means we need to multiply Ecell by this factor:
Ecell = -0.35 V × 1 J/C = -0.35 J/C
Finally, we can calculate Wmax using the equation:
Wmax = -nFEcell = -(2)(96,485 C/mol)(-0.35 J/C)
Now we can substitute the values and calculate Wmax:
Wmax = (2)(96,485)(0.35) ≈ 67,940 J
Rounding to 3 significant figures, the value of Wmax is approximately 67,900 J.