Chapter 19: Problem 64
The oxidation of \(25.0 \mathrm{~mL}\) of a solution containing \(\mathrm{Fe}^{2+}\) requires \(26.0 \mathrm{~mL}\) of \(0.0250 \mathrm{M} \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) in acidic solution. Balance the following equation, and calculate the molar concentration of \(\mathrm{Fe}^{2+}\) : $$ \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+\mathrm{Fe}^{2+}+\mathrm{H}^{+} \longrightarrow \mathrm{Cr}^{3+}+\mathrm{Fe}^{3+} $$
Short Answer
Step by step solution
Determine the balanced chemical equation
Calculate moles of K₂Cr₂O₇
Relate moles of Cr₂O₇²⁻ to Fe²⁺
Calculate the molarity of Fe²⁺
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Molarity Calculation
To calculate molarity, follow these steps:
- Calculate the moles of solute using the relation: \( \text{Moles} = \text{molarity} \times \text{volume (in L)} \).
- Determine the volume of the solution in liters by converting mL to L. Remember: 1 mL = 0.001 L.
- Calculate molarity using \( \text{Molarity} = \frac{\text{moles of solute}}{\text{volume of solution in L}} \).
Balancing Chemical Equations
Here are steps to balance oxidation-reduction reactions:
- Separate the equation into two half-reactions: one for oxidation and one for reduction.
- For each half-reaction, balance the atoms other than O and H first.
- Then, balance oxygen atoms by adding water (\( \mathrm{H}_2\mathrm{O} \)).
- Balance hydrogen atoms by adding protons (\( \mathrm{H}^+ \)).
- Finally, balance the electrons by ensuring equal charge on both sides of the half-reactions.
Stoichiometry
To apply stoichiometry effectively:
- Use the balanced chemical equation to understand the mole ratio of each reactant and product.
- Convert all given information to moles (e.g., using molarity and volume).
- Apply the mole ratio from the balanced equation to find unknown quantities.
Acidic Solution
Key aspects of acidic solutions in reactions:
- The presence of \( \mathrm{H}^+ \) ions can help balance the reaction, especially for oxygen and hydrogen.
- Acidic environments can alter the rate and equilibrium of reactions, making certain reductions or oxidations possible.
- Understanding the role of \( \mathrm{H}^+ \) assists in balancing redox equations and predicting product formation in reactions.