The titration of a 20.0 mL sample of an H2SO4 solution of unknown concentration requires 22.51 mL of a 0.154 M KOH solution to reach the equivalence point. What is the concentration of the unknown H2SO4 solution? Express your answer to three significant figures.

• A. 0.0865 M
• B. 0.173 M
• C. 0.0770 M
• D. 0.154 M

Answer: (A)

Verified step by step guidance

1. Start by writing the balanced chemical equation for the reaction between sulfuric acid (H2SO4) and potassium hydroxide (KOH). The balanced equation is: ${H2\mathrm{SO}4}_{\mathrm{aq}}+2{\mathrm{KOH}}_{\mathrm{aq}}\to {K2\mathrm{SO}4}_{\mathrm{aq}}+2{H2O}_{\mathrm{l}}$.
2. Determine the moles of KOH used in the titration. Use the formula: $\mathrm{moles}=\mathrm{volume}\times \mathrm{molarity}$. Convert the volume from mL to L by dividing by 1000: $22.51\times 0.154$.
3. Use the stoichiometry of the balanced equation to find the moles of H2SO4. According to the equation, 2 moles of KOH react with 1 mole of H2SO4. Therefore, divide the moles of KOH by 2 to find the moles of H2SO4.
4. Calculate the concentration of the H2SO4 solution using the formula: $\mathrm{Concentration}=\frac{\mathrm{moles}}{\mathrm{volume}}$. Use the moles of H2SO4 calculated in the previous step and the initial volume of the H2SO4 solution (20.0 mL converted to L).
5. Express the final concentration of the H2SO4 solution to three significant figures, as required by the problem.