Chapter 4: Problem 104
A solid sample of \(\mathrm{Fe}(\mathrm{OH})_{3}\) is added to \(0.500 \mathrm{~L}\) of \(0.250 \mathrm{M}\) aqueous \(\mathrm{H}_{2} \mathrm{SO}_{4}\). The solution that remains is still acidic. It is then titrated with \(0.500 \mathrm{M} \mathrm{NaOH}\) solution, and it takes \(12.5 \mathrm{~mL}\) of the NaOH solution to reach the equivalence point. What mass of \(\mathrm{Fe}(\mathrm{OH})_{3}\) was added to the \(\mathrm{H}_{2} \mathrm{SO}_{4}\) solution?
Short Answer
Step by step solution
Determine Initial Moles of Acid
Find Moles of Base Used in Titration
Calculate Moles of Excess Acid
Calculate Moles of Acid Reacted with \(\mathrm{Fe(OH)}_3\)
Calculate Moles of \(\mathrm{Fe(OH)}_3\) Reacted
Calculate Mass of \(\mathrm{Fe(OH)}_3\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Stoichiometry
This allows us to calculate the amounts involved in the reaction.
- Through balanced equations, we find the mole-to-mole relationships.
- Using these ratios, we convert between moles of different substances.
- For example, 1 mole of \( \mathrm{Fe(OH)}_3 \) needs 3 moles of \( \mathrm{H}^+ \) ions for the reaction.
Molarity
- The formula for molarity is: \[ \text{Molarity} = \frac{\text{Moles of solute}}{\text{Liters of solution}} \]
- Using this, we calculated that the \( \mathrm{H}_2\mathrm{SO}_4 \) solution had 0.125 moles.
- It also confirmed that 0.00625 moles of \( \mathrm{NaOH} \) was used.
Chemical Reactions
- The original reaction: \( \mathrm{Fe(OH)}_3 + 3 \mathrm{H}^+ \rightarrow \mathrm{Fe}^{3+} + 3 \mathrm{H}_2\mathrm{O} \).
- Shows that 1 mole of \( \mathrm{Fe(OH)}_3 \) reacts with 3 moles of \( \mathrm{H}^+ \).
- Through titration, we determine how much \( \mathrm{H}^+ \) was neutralized by \( \mathrm{NaOH} \).
Diprotic Acids
- Initial calculation for \( \mathrm{H}_2\mathrm{SO}_4 \): \[ 0.125 \, \text{mol} \, \mathrm{H}_2\mathrm{SO}_4 \times 2 = 0.250 \, \text{mol} \, \mathrm{H}^+ \]
- This informs us of the total acidic potential of the solution.
- This concept feeds into the stoichiometric calculations that follow.