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What is the potential for the cell Cr|...

What is the potential for the cell
`Cr|Cr^(3+)(0.1M)||Fe^(2+)(0.01M)|Fe`
`E^(@)Cr^(3+)// Cr=-0.74V`,
`E^(@)Fe^(2+)//Fe=-0.44V`

A

`+0.2606V`

B

`+0.5212V`

C

`+0.1303V`

D

`-0.2606V`.

Text Solution

AI Generated Solution

The correct Answer is:
To find the potential for the cell given by the notation `Cr|Cr^(3+)(0.1M)||Fe^(2+)(0.01M)|Fe`, we will follow these steps: ### Step 1: Identify the half-reactions and their standard potentials The cell notation indicates that chromium is being oxidized and iron is being reduced. The standard reduction potentials are given as: - For Chromium: \( E^\circ_{Cr^{3+}/Cr} = -0.74 \, V \) - For Iron: \( E^\circ_{Fe^{2+}/Fe} = -0.44 \, V \) ### Step 2: Determine the oxidation potential for chromium Since the reduction potential for chromium is given, we need to convert it to oxidation potential: - Oxidation potential for \( Cr \): \[ E^\circ_{oxidation} = -E^\circ_{reduction} = +0.74 \, V \] ### Step 3: Write the half-reactions The half-reactions can be written as follows: - Anode (oxidation): \[ Cr \rightarrow Cr^{3+} + 3e^- \] - Cathode (reduction): \[ Fe^{2+} + 2e^- \rightarrow Fe \] ### Step 4: Balance the electrons To balance the number of electrons transferred, we need to multiply the half-reactions: - Multiply the chromium half-reaction by 2: \[ 2Cr \rightarrow 2Cr^{3+} + 6e^- \] - Multiply the iron half-reaction by 3: \[ 3Fe^{2+} + 6e^- \rightarrow 3Fe \] ### Step 5: Write the overall cell reaction Combining the balanced half-reactions gives us the overall cell reaction: \[ 2Cr + 3Fe^{2+} \rightarrow 2Cr^{3+} + 3Fe \] ### Step 6: Calculate the standard EMF of the cell The standard EMF of the cell can be calculated using: \[ E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode} \] Substituting the values: \[ E^\circ_{cell} = (-0.44 \, V) - (-0.74 \, V) = 0.30 \, V \] ### Step 7: Apply the Nernst equation The Nernst equation is given by: \[ E = E^\circ - \frac{0.0591}{n} \log Q \] Where: - \( n = 6 \) (total electrons transferred) - \( Q = \frac{[Cr^{3+}]^2}{[Fe^{2+}]^3} = \frac{(0.1)^2}{(0.01)^3} = \frac{0.01}{0.000001} = 10000 \) ### Step 8: Calculate the logarithm and substitute into the Nernst equation Calculating \( \log Q \): \[ \log(10000) = 4 \] Now substituting into the Nernst equation: \[ E = 0.30 \, V - \frac{0.0591}{6} \cdot 4 \] Calculating: \[ E = 0.30 \, V - \frac{0.0591 \cdot 4}{6} = 0.30 \, V - 0.0394 \, V = 0.2606 \, V \] ### Final Answer The potential for the cell is: \[ E \approx 0.2606 \, V \]

To find the potential for the cell given by the notation `Cr|Cr^(3+)(0.1M)||Fe^(2+)(0.01M)|Fe`, we will follow these steps: ### Step 1: Identify the half-reactions and their standard potentials The cell notation indicates that chromium is being oxidized and iron is being reduced. The standard reduction potentials are given as: - For Chromium: \( E^\circ_{Cr^{3+}/Cr} = -0.74 \, V \) - For Iron: \( E^\circ_{Fe^{2+}/Fe} = -0.44 \, V \) ### Step 2: Determine the oxidation potential for chromium ...
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