Given the following standard reduction potentials at 25 °C, (a) balance the equation for the reaction of H2MoO4 with elemental arsenic in acidic solution to give Mo3+ and H3AsO4 and (b) calculate E° for this reaction.

Verified step by step guidance

Step 1: Identify the half-reactions involved.

Step 2: Write the reduction half-reaction for H2MoO4 to Mo^{3+}.

Step 3: Write the oxidation half-reaction for elemental arsenic to H3AsO4.

Step 4: Balance each half-reaction for mass and charge.

Step 5: Combine the balanced half-reactions and calculate the standard cell potential, E°.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Standard Reduction Potentials

Standard reduction potentials (E°) are measures of the tendency of a chemical species to gain electrons and be reduced. Each half-reaction has a specific E° value, which is determined under standard conditions (1 M concentration, 1 atm pressure, and 25 °C). These values are crucial for predicting the direction of redox reactions and calculating the overall cell potential.

Balancing Redox Reactions

Balancing redox reactions involves ensuring that both mass and charge are conserved. This typically requires separating the reaction into half-reactions for oxidation and reduction, balancing each for atoms and charges, and then combining them. In acidic solutions, protons (H⁺) and water (H₂O) are often used to achieve balance.

Electrochemical Cell Potential

The electrochemical cell potential (E°cell) is calculated by subtracting the standard reduction potential of the oxidation half-reaction from that of the reduction half-reaction. This value indicates the driving force of the reaction; a positive E°cell suggests that the reaction is spontaneous under standard conditions. Understanding how to calculate E°cell is essential for evaluating the feasibility of redox reactions.

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Textbook Question

The reaction of MnO₄^– with oxalic acid (H₂C₂O₄) in acidic solution, yielding Mn²⁺ and CO₂ gas, is widely used to determine the concentration of permanganate solutions. (d) A 1.200 g sample of sodium oxalate (Na₂C₂O₄) is dissolved in dilute H₂SO₄ and then titrated with a KMnO₄ solution. If 32.50 mL of the KMnO₄ solution is required to reach the equivalence point, what is the molarity of the KMnO₄ solution?