Math Problem Statement

Calculate the pH of a buffer system containing 1.5 M HClO and 1.7 M NaClO. Be sure your answer has the correct number of significant figures.

Solution

The problem asks to calculate the pH of a buffer system containing 1.5 M HClO\text{HClO} and 1.7 M NaClO\text{NaClO}, using the dissociation constant (KaK_a) of the acid HClO\text{HClO}.

This is a typical buffer problem, and the pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation:

[ \text{pH} = \text{p}K_a + \log \left( \frac{[\text{Base}]}{[\text{Acid}]} \right) ]

Where:

  • [Base][\text{Base}] is the concentration of ClO\text{ClO}^- from NaClO\text{NaClO},
  • [Acid][\text{Acid}] is the concentration of HClO\text{HClO},
  • pKa=log(Ka)\text{p}K_a = -\log(K_a).

From the problem, we know:

  • [HClO]=1.5M[\text{HClO}] = 1.5 \, \text{M},
  • [NaClO]=1.7M[\text{NaClO}] = 1.7 \, \text{M}.

We still need the KaK_a value for hypochlorous acid (HClO)(\text{HClO}) at 25°C. The typical value for KaK_a of HClO\text{HClO} is around 2.9×1082.9 \times 10^{-8}. Now, let's proceed with the calculation.

  1. Calculate pKa: pKa=log(2.9×108)7.54\text{p}K_a = -\log(2.9 \times 10^{-8}) \approx 7.54

  2. Apply the Henderson-Hasselbalch equation: pH=7.54+log(1.71.5)\text{pH} = 7.54 + \log \left( \frac{1.7}{1.5} \right) pH=7.54+log(1.133)7.54+0.054=7.59\text{pH} = 7.54 + \log(1.133) \approx 7.54 + 0.054 = 7.59

Therefore, the pH of the buffer system is approximately 7.59.

Would you like further details on this solution or any clarifications?

Related Questions:

  1. How does the Henderson-Hasselbalch equation apply to buffer systems?
  2. What factors influence the pH of a buffer solution?
  3. Why is it important to use significant figures when calculating pH?
  4. How does temperature affect the KaK_a value of acids like HClO\text{HClO}?
  5. Can you calculate the pH if only HClO\text{HClO} or NaClO\text{NaClO} was present?

Tip:

Always check the units and make sure concentrations are in molarity (M) when applying the Henderson-Hasselbalch equation.

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Math Problem Analysis

Mathematical Concepts

Acid-Base Equilibrium
Logarithms
Buffer Solutions

Formulas

Henderson-Hasselbalch equation: pH = pKa + log([Base]/[Acid])
pKa = -log(Ka)

Theorems

Henderson-Hasselbalch Equation

Suitable Grade Level

Grades 11-12, College-level Chemistry