Chapter 11: QHE (page 258)

A $^{0.100 M}$ solution of the weak acid HA was titrated with $^{0.100 M}$ NaOH. The measured when $^{V_{b} = \frac{1}{2} V_{e}}$ was $^{4.62}$ . Using activity coefficients, calculate $^{{pK}_{a}}$ . The size of the $^{A^{-}}$ anion is $^{450 pm}$ .

Short Answer

Expert verified

The size of the $^{A^{-}}$ anion is $^{450 pm}$ , and a $^{0.100 M}$ weak acid HA solution was titrated with $^{0.100 M}$ NaOH utilising activity coefficients $^{{pK}_{a}}$ yielding a result of 4.69.

Step by step solution

Define the formula activity coefficients (Henderson-Hassel Balch) equation

The equation that calculates the $^{pH}$ as a measure of acidity in chemical and biological systems, as well as the $^{pH}$ of buffer solutions and the equilibrium in acid-base processes.

The equation for activity coefficients is as follows:

$pH = 4.62 - \log_{10} (\frac{{|A^{-}|}_{A^{-}}}{|HA| γ_{HA}})$

Here,

${Pk}_{a} = acid dissociation constant . [A^{-}] = concentration of base [{HA}^{-}] = concentration of conjugate acid .$

Calculate the value

The measured $^{pH}$ is 4.62 whenlocalid="1654861177319" $^{V_{b} = \frac{1}{2} V_{e}}$

The $^{pH}$ is equal to $^{{pK}_{a}}$ value when $^{V_{b} = \frac{1}{2} V_{c}}$ $^{V_{b} = \frac{1}{2} V_{c}}$ .

The concentration of $^{[HA] = [A^{-}] = 0.0333 M}$

Here $^{[{Na}^{+}] = 0.0333 M}$

Now, substitute the above values in the activity coefficients equation.

The activity coefficient of $^{γ_{A^{-}} = 0.854}$ and $^{γ_{HA} = 1.00}$

pH = 4.62 - \log_{10} (\frac{0.0003331 (0.854)}{|0.0333| (1.00)}) = 4.69

Therefore, $^{{pK}_{a}}$ is 4.69.

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A $^{0.100 M}$ solution of the weak acid HA was titrated with $^{0.100 M}$ NaOH. The measured when $^{V_{b} = \frac{1}{2} V_{e}}$ was $^{4.62}$ . Using activity coefficients, calculate $^{{pK}_{a}}$ . The size of the $^{A^{-}}$ anion is $^{450 pm}$ .

Short Answer

Step by step solution

Define the formula activity coefficients (Henderson-Hassel Balch) equation

Calculate the value

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A 0.100Msolution of the weak acid HA was titrated with 0.100MNaOH. The measured when Vb=12Vewas 4.62. Using activity coefficients, calculate pKa. The size of theA- anion is 450pm.

Short Answer

Step by step solution

Define the formula activity coefficients (Henderson-Hassel Balch) equation

Calculate the value

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Chemistry Textbooks

Chemical Reactions

Nuclear Chemistry

Chemical Analysis

Physical Chemistry

Chemistry Branches

Kinetics

Study anywhere. Anytime. Across all devices.

A $^{0.100 M}$ solution of the weak acid HA was titrated with $^{0.100 M}$ NaOH. The measured when $^{V_{b} = \frac{1}{2} V_{e}}$ was $^{4.62}$ . Using activity coefficients, calculate $^{{pK}_{a}}$ . The size of the $^{A^{-}}$ anion is $^{450 pm}$ .