A 20.0-mL sample of 0.200 M HBr solution is titrated with 0.200 M NaOH solution. Calculate the pH of the solution after the following volumes of base have been added:
(a) 15.0 mL
(b) 19.9 mL.

검증된 단계별 안내

Calculate the initial moles of HBr in the solution using the formula: \( \text{moles} = \text{concentration} \times \text{volume} \).

Calculate the moles of NaOH added using the same formula: \( \text{moles} = \text{concentration} \times \text{volume} \).

Determine the moles of HBr remaining after the reaction by subtracting the moles of NaOH from the initial moles of HBr.

Since HBr is a strong acid and NaOH is a strong base, they react in a 1:1 ratio to form water and NaBr. Use the remaining moles of HBr to find the concentration of \( \text{H}^+ \) ions in the solution.

Calculate the pH of the solution using the formula: \( \text{pH} = -\log[\text{H}^+] \).

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주요 개념

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Titration

Titration is a quantitative analytical technique used to determine the concentration of a solute in a solution. It involves the gradual addition of a titrant (in this case, NaOH) to a solution containing the analyte (HBr) until the reaction reaches its equivalence point, where stoichiometrically equivalent amounts of acid and base have reacted.

pH Calculation

pH is a measure of the acidity or basicity of a solution, defined as the negative logarithm of the hydrogen ion concentration. In titration problems, pH can be calculated using the concentrations of the reactants and the volume of titrant added, especially before, at, and after the equivalence point, where the solution's composition changes significantly.

Equivalence Point

The equivalence point in a titration is the stage at which the amount of titrant added is stoichiometrically equivalent to the amount of substance present in the solution being titrated. For a strong acid-strong base titration, like HBr with NaOH, the pH at the equivalence point is typically around 7, as the resulting solution contains only water and a neutral salt.

A 20.0-mL sample of 0.200 M HBr solution is titrated with 0.200 M NaOH solution. Calculate the pH of the solution after the following volumes of base have been added:(a) 15.0 mL(b) 19.9 mL.