Calculate the pH of the solution that results from each mixture. a. 50.0 mL of 0.15 M HCHO₂ with 75.0 mL of 0.13 M NaCHO₂

검증된 단계별 안내

1. Identify the species in the solution. HCHO₂ is a weak acid and NaCHO₂ is the salt of its conjugate base, CHO₂^-. This is a buffer solution, so we can use the Henderson-Hasselbalch equation to calculate the pH.

2. Calculate the initial moles of HCHO₂ and CHO₂^- in the solution. This can be done by multiplying the volume (in liters) of each solution by its molarity. Remember that the volume of the solution is the sum of the volumes of the acid and the base.

3. Use the Henderson-Hasselbalch equation, pH = pKa + log([A^-]/[HA]), where [A^-] is the molar concentration of the base (CHO₂^-) and [HA] is the molar concentration of the acid (HCHO₂). The pKa value can be found in a table or given in the problem.

4. Substitute the values of pKa, [A^-] and [HA] into the Henderson-Hasselbalch equation to calculate the pH of the solution.

5. If the pH is less than 7, the solution is acidic. If the pH is greater than 7, the solution is basic. If the pH is 7, the solution is neutral.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Acid-Base Chemistry

Acid-base chemistry involves the study of substances that can donate protons (acids) or accept protons (bases). In this question, HCHO2 (formic acid) acts as the acid, while NaCHO2 (sodium formate) serves as its conjugate base. Understanding the properties of acids and bases, including their dissociation in water, is essential for calculating pH.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a formula used to calculate the pH of a buffer solution. It relates the pH to the pKa of the acid and the ratio of the concentrations of the conjugate base to the acid. This equation is particularly useful in this scenario, as the mixture of formic acid and sodium formate creates a buffer system.

Dilution and Concentration Calculations

Dilution and concentration calculations are crucial for determining the final concentrations of solutes in a solution after mixing. When two solutions are combined, the total volume changes, affecting the concentrations of the individual components. Accurately calculating the new concentrations of HCHO2 and NaCHO2 after mixing is necessary to apply the Henderson-Hasselbalch equation effectively.

Calculate the pH of the solution that results from each mixture. a. 50.0 mL of 0.15 M HCHO2 with 75.0 mL of 0.13 M NaCHO2