Scelta multipla
Which of the following is the conjugate acid of the base H2PO4⁻?
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17. Acid and Base Equilibrium
Acids Introduction
Scelta multipla
The titration of 80.0 mL of an unknown concentration H3PO4 solution requires 126.0 mL of 0.218 M KOH solution. What is the concentration of the H3PO4 solution (in M)?
A
0.114 M
B
0.229 M
C
0.343 M
D
0.457 M
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Write the balanced chemical equation for the reaction: \( \text{H}_3\text{PO}_4 + 3\text{KOH} \rightarrow \text{K}_3\text{PO}_4 + 3\text{H}_2\text{O} \). This shows that one mole of \( \text{H}_3\text{PO}_4 \) reacts with three moles of \( \text{KOH} \).
Calculate the moles of \( \text{KOH} \) used in the titration. Use the formula: \( \text{moles of KOH} = \text{volume (L)} \times \text{molarity (M)} \). Convert 126.0 mL to liters by dividing by 1000.
Determine the moles of \( \text{H}_3\text{PO}_4 \) that reacted. Since the stoichiometry of the reaction is 1:3, divide the moles of \( \text{KOH} \) by 3 to find the moles of \( \text{H}_3\text{PO}_4 \).
Calculate the concentration of the \( \text{H}_3\text{PO}_4 \) solution. Use the formula: \( \text{concentration (M)} = \frac{\text{moles of } \text{H}_3\text{PO}_4}{\text{volume of } \text{H}_3\text{PO}_4 \text{ in liters}} \). Convert 80.0 mL to liters by dividing by 1000.
Verify the calculation by checking the units and ensuring that the stoichiometry and volume conversions are correctly applied. This will confirm the concentration of the \( \text{H}_3\text{PO}_4 \) solution.
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