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15240672380's Question
Chemistry
Posted 10 months ago

A sample of iron ore weighing 0.2692 g0.2692 \mathrm{~g} was dissolved in an excess of a dilute acid solution. All the iron was first converted to Fe2+\mathrm{Fe}^{2+} ions. The solution then required 22.10 mL22.10 \mathrm{~mL} of 0.0184MKMnO40.0184 \mathrm{M} \mathrm{KMnO}_{4} for oxidation to Fe3+\mathrm{Fe}^{3+} ions. Calculate the percent by mass of iron in the ore. Round your answer to 3 significant digi
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Answer from Sia
Posted 10 months ago
Solution
1
Write the balanced chemical equation for the reaction: The reaction between Fe2+\mathrm{Fe}^{2+} ions and KMnO4\mathrm{KMnO}_4 in acidic solution is as follows: 5Fe2++MnO4−+8H+→5Fe3++Mn2++4H2O5 \mathrm{Fe}^{2+} + \mathrm{MnO}_4^- + 8H^+ \rightarrow 5 \mathrm{Fe}^{3+} + \mathrm{Mn}^{2+} + 4H_2O
2
Calculate moles of $\mathrm{KMnO}_4$ used: Use the molarity and volume of KMnO4\mathrm{KMnO}_4 to find the moles. Moles of KMnO4\mathrm{KMnO}_4 = Molarity ×\times Volume (in liters) = 0.0184M×0.02210L=4.0664×10−40.0184 \mathrm{M} \times 0.02210 \mathrm{L} = 4.0664 \times 10^{-4} moles
3
Determine moles of $\mathrm{Fe}^{2+}$ using stoichiometry: From the balanced equation, 1 mole of KMnO4\mathrm{KMnO}_4 reacts with 5 moles of Fe2+\mathrm{Fe}^{2+}. Therefore, moles of Fe2+\mathrm{Fe}^{2+} = 5×5 \times moles of KMnO4\mathrm{KMnO}_4 = 5×4.0664×10−45 \times 4.0664 \times 10^{-4} moles = 2.0332×10−32.0332 \times 10^{-3} moles
4
Calculate mass of iron: The molar mass of iron (Fe) is 55.845g/mol55.845 \mathrm{g/mol}. Mass of iron = moles of Fe2+×\mathrm{Fe}^{2+} \times molar mass of Fe = 2.0332×10−3mol×55.845g/mol=0.1135g2.0332 \times 10^{-3} \mathrm{mol} \times 55.845 \mathrm{g/mol} = 0.1135 \mathrm{g}
5
Calculate the percent by mass of iron in the ore: Percent by mass = mass of ironmass of ore sample×100%=0.1135g0.2692g×100%=42.17%\frac{\text{mass of iron}}{\text{mass of ore sample}} \times 100\% = \frac{0.1135 \mathrm{g}}{0.2692 \mathrm{g}} \times 100\% = 42.17\%
Answer
42.17%
Key Concept
Stoichiometry and molarity in redox reactions
Explanation
The percent by mass of iron in the ore is calculated using stoichiometry to relate moles of KMnO4\mathrm{KMnO}_4 to moles of Fe2+\mathrm{Fe}^{2+}, and then converting moles of iron to mass.

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