Predict from Table 17.1 whether each of the following...

Predict from Table 17.1 whether each of the following reactions canoccur under standard-state conditions: (a) $2 \mathrm{Fe}^{3+}(a q)+2 \mathrm{I}^{-}(a q) \longrightarrow 2 \mathrm{Fe}^{2+}(a q)+\mathrm{I}_{2}(s)$ (b) $3 \mathrm{Ni}(s)+2 \mathrm{Al}^{3+}(a q) \longrightarrow 3 \mathrm{Ni}^{2+}(a q)+2 \mathrm{Al}(s)$ Confirm your predictions by calculating the value of $E^{\circ}$ for each reaction. Which reaction(s) can occur in the reverse direction under standard-state conditions?

Predict from Table 17.1 whether each of the following reactions canoccur under standard-state
conditions:
(a) $2 \mathrm{Fe}^{3+}(a q)+2 \mathrm{I}^{-}(a q) \longrightarrow 2 \mathrm{Fe}^{2+}(a q)+\mathrm{I}_{2}(s)$
(b) $3 \mathrm{Ni}(s)+2 \mathrm{Al}^{3+}(a q) \longrightarrow 3 \mathrm{Ni}^{2+}(a q)+2 \mathrm{Al}(s)$
Confirm your predictions by calculating the value of $E^{\circ}$ for each reaction. Which reaction(s) can occur in the reverse direction under standard-state conditions?

Key Concepts

Standard Reduction Potentials

Standard reduction potentials represent the inherent tendency for a chemical species to gain electrons (be reduced) under standard conditions. These potentials are measured versus the standard hydrogen electrode and tabulated in reference tables, making them a fundamental tool in predicting the direction of redox reactions.

Calculating E° for Redox Reactions

The overall cell potential (E°cell) for a redox reaction is determined by combining the standard reduction potentials of the half-reactions. By identifying and correctly pairing the oxidation and reduction half-reactions, and then applying the equation E°cell = E°cathode - E°anode, one can compute the net cell potential, which provides insight into the reaction’s spontaneity.

Reaction Spontaneity

The sign of the overall cell potential indicates whether a redox reaction is spontaneous under standard-state conditions. A positive E°cell implies the reaction is thermodynamically favorable (spontaneous) in the written direction, while a negative E°cell suggests that the reaction would be spontaneous if it proceeded in the reverse direction.

Reversibility Under Standard-State Conditions

Evaluating whether a reaction can occur in the reverse direction under standard-state conditions involves examining the calculated E°cell. If the forward reaction yields a negative E°cell, the reaction, as written, is non-spontaneous and the reverse reaction will be spontaneous. This principle is essential for understanding the dynamics of chemical equilibria and reaction feasibility.

Transcript

00:01 So in this problem we are given with two reaction equation and we are asked to find out if these reactions will occur spontaneously under standard state conditions.

00:12 We have to confirm our prediction by calculating the value of the standard cell potential and from the value of standard cell potential we will be able to say that whether a reaction is spontaneous or not as we know that if the standard potential is positive value that means the reaction will be spontaneous and if the standard partition value is negative that means the reaction or the forward reaction will not be spontaneous so let's first solve the problem for the first reaction equation which is 2 f e 3 plus react to it to iodide to give us 2 f e2 plus plus iodine so to find out if this reaction will be spontaneous or not first we have to write down their half cell reactions so the half cell reaction for the f e 3 plus 2 if e 2 plus will be if 3 plus will take up one electron to become f f2 plus and in case of the iodine the hopsceleration will be the iodide ion will give up or it will give up an electron to become iodine but since iodin is a diatomic molecule in that case each time 2 a ions will be reduced to give us iron in molecule and it will produce two electrons and these two electrons will be consumed by this fe3 plus ions so to cancel out the electrons in both the half cells we have to multiply this equation by two so it will be 2 f e3 plus plus will be 2 f e minus will be 2 f e 2 plus so now we have same number of electrons in both the half reactions now let's write down there's standard half cell potentials because that's the value we will need to determine whether this reaction will be spontaneous or not so the standard reduction potential for these half cell reaction is 0 .77 volt and the standard oxidation potential for this half cell will be minus 0 .54 volt and now if you sum up these two reactions we cancel out the electrons and the final reaction will be 2 f3 plus plus 2 iodide and this will give us 2 a few plus aridin and the overall cell potential will be um.....

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