Chapter 10: Q27P (page 232)

The acid HA has ${pK}_{a}$ = 4.00. Find the fraction in the form HA and the fraction in the form A^- at pH = 5.00. Does your answer agree with what you
expect for the quotient [A2]/[HA] at pH 5.00?

Short Answer

Expert verified

The answer would agree with expected for the quotient at pH 5.00.

Step by step solution

Step 1: Henderson Hasselbalch Equation

One way to determine the pH of a buffer is by using the Henderson–Hasselbalch equation, which is pH = pKₐ + log([A⁻]/[HA]). In this equation, [HA] and [A⁻] refer to the equilibrium concentrations of the conjugate acid–base pair used to create the buffer solution.

Calculating fraction in the form HA and the fraction in theform A- at pH = 5.00;

Fraction in the form of HA,

$HA = α (HA) = \frac{[H^{+}]}{[H^{+}] + K_{a}} α (HA) = \frac{10^{- 5}}{10^{- 5} + 10^{- 4}} α (HA) = 0.0909$

Fraction in the form of A^-,

$A^{-} = α (A^{-}) = \frac{K_{a}}{[H^{+}] + K_{a}} α (A -) = \frac{10^{- 4}}{10^{- 5} + 10^{- 4}} α (A -) = 0.909$

From Henderson Hasselbalch Equation;

$pH = {pK}_{a} + \log (\frac{[A^{-}]}{[HA]}) 5.00 = 4.00 + \log (\frac{0.909}{0.0909}) 10 = 10$

Hence, our answer would agree with expected for the quotient $\frac{[A^{-}]}{[HA]}$ at Ph 5.00.

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The acid HA has ${pK}_{a}$ = 4.00. Find the fraction in the form HA and the fraction in the form A^- at pH = 5.00. Does your answer agree with what you
expect for the quotient [A2]/[HA] at pH 5.00?

Short Answer

Step by step solution

Step 1: Henderson Hasselbalch Equation

Calculating fraction in the form HA and the fraction in theform A- at pH = 5.00;

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The acid HA has pKa= 4.00. Find the fraction in the form HA and the fraction in the form A- at pH = 5.00. Does your answer agree with what youexpect for the quotient [A2]/[HA] at pH 5.00?

Short Answer

Step by step solution

Step 1: Henderson Hasselbalch Equation

Calculating fraction in the form HA and the fraction in theform A- at pH = 5.00;

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Chemistry Textbooks

Inorganic Chemistry

Chemical Analysis

Chemical Reactions

The Earths Atmosphere

Kinetics

Ionic and Molecular Compounds

Study anywhere. Anytime. Across all devices.

The acid HA has ${pK}_{a}$ = 4.00. Find the fraction in the form HA and the fraction in the form A^- at pH = 5.00. Does your answer agree with what you
expect for the quotient [A2]/[HA] at pH 5.00?