Chapter 9: Q12P (page 208)

A $0.0450 M$ solution of HAis 0.60%dissociated. Calculate ${pK}_{a}$ for this acid.

Short Answer

Expert verified

The ${pK}_{a}$ for HA is $= 5.79$

Step by step solution

Define pKa

${pK}_{a}$ is the number that describes the acidity of a particular molecule. The formula to find the ${pK}_{a}$ is

role="math" localid="1654857717351" ${pK}_{a} = - {logK}_{a}$

Reaction of HA dissociation

$HA \overset{}{⇌} H^{+} + A^{-} [HA] = 0.0450 - x [H^{+}] = [A^{-}] = x$

Fraction of dissociation

Substituting the value of $a$ and F in equation

$a = \frac{x}{F} = 0.0060 \Rightarrow x = a \times F x = 0.0060 \times 0.0450$

Calculating the value of Ka

By using the formula $K_{a} = \frac{x^{2}}{F - x}$

Substituting the value ofxand F we get

$K_{a} = \frac{x^{2}}{F - x} K_{a} = \frac{{(0.0060 \times 0.0450)}^{2}}{0.0450 - (0.0060 \times 0.0450)} = 1.6 \times 10^{- 6}$

Step 5: Finding the value of pKa

Substituting the value of $K_{a}$ in the formula role="math" localid="1654858632522" ${pK}_{a}$ we get

${pK}_{a} = - {logK}_{a} = - \log (1.6 \times 10^{- 6}) = 5.79$

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A $0.0450 M$ solution of HAis 0.60%dissociated. Calculate ${pK}_{a}$ for this acid.

Short Answer

Step by step solution

Define pKa

Reaction of HA dissociation

Fraction of dissociation

Calculating the value of Ka

Step 5: Finding the value of pKa

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A 0.0450Msolution of HAis 0.60%dissociated. CalculatepKafor this acid.

Short Answer

Step by step solution

Define pKa

Reaction of HA dissociation

Fraction of dissociation

Calculating the value of Ka

Step 5: Finding the value of pKa

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Chemistry Textbooks

Chemistry Branches

Physical Chemistry

Nuclear Chemistry

The Earths Atmosphere

Chemical Reactions

Ionic and Molecular Compounds

Study anywhere. Anytime. Across all devices.

A $0.0450 M$ solution of HAis 0.60%dissociated. Calculate ${pK}_{a}$ for this acid.