Chapter 19: Q19.24P (page 873)

What is the component concentration ratio, $[N O_{2}^{-}] / [H N O_{2}]$ , of a buffer that has a pH of 2.95( $K_{a}$ of ${HNO}_{2} {= 7.1×10}^{- 4}$ )?

Short Answer

Expert verified

The component concentration ratio obtained is $\frac{[N {O_{2}}^{-}]}{{[HNO}_{2}]} = 0.63$ .

Step by step solution

Henderson-Hesselbalch Equation

The pH of a buffer solution can be determined by using theHenderson-Hesselbalchequation. The formula to calculate the pH of an acidic buffer solution is:

$pH = pKa + \log \frac{[salt]}{[acid]}$

Calculation

Write the ${HNO}_{2}$ dissociation reaction first.

${HNO}_{2} {+H}_{2} O ⇌ H_{3} O^{+} + N {O_{2}}^{-} .$

We must alter the Henderson-Hasselbalch equation to find $\frac{[N {O_{2}}^{-}]}{{[HNO}_{2}]}$ .

The pH and $K_{a}$ are given. Therefore, first solve for the ${pK}_{a}$ .

${pK}_{a} {= - logK}_{a} {= - log(7.1×10}^{- 4}) = 3.15$

Then, solve for $\frac{[N {O_{2}}^{-}]}{{[HNO}_{2}]}$ using the Henderson-Hasselbalch equation as:

role="math" localid="1663389158459" ${pH = pK}_{a} + log \frac{[N {O_{2}}^{-}]}{{[HNO}_{2}]} log \frac{[N {O_{2}}^{-}]}{{[HNO}_{2}]} {= pH - pK}_{a} \frac{[N {O_{2}}^{-}]}{{[HNO}_{2}]} {= 10}^{{pH - pK}_{a}} {= 10}^{2.95 - 3.15} = 0.63.$

Therefore, thecomponent concentration ratio obtained is $\frac{[N {O_{2}}^{-}]}{{[HNO}_{2}]} = 0.63$ .

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What is the component concentration ratio, $[N O_{2}^{-}] / [H N O_{2}]$ , of a buffer that has a pH of 2.95( $K_{a}$ of ${HNO}_{2} {= 7.1×10}^{- 4}$ )?

Short Answer

Step by step solution

Henderson-Hesselbalch Equation

Calculation

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What is the component concentration ratio, [NO2-]/[HNO2], of a buffer that has a pH of 2.95(Kaof HNO2= 7.1×10-4)?

Short Answer

Step by step solution

Henderson-Hesselbalch Equation

Calculation

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Chemistry Textbooks

Ionic and Molecular Compounds

The Earths Atmosphere

Chemistry Branches

Making Measurements

Kinetics

Chemical Analysis

Study anywhere. Anytime. Across all devices.

What is the component concentration ratio, $[N O_{2}^{-}] / [H N O_{2}]$ , of a buffer that has a pH of 2.95( $K_{a}$ of ${HNO}_{2} {= 7.1×10}^{- 4}$ )?