Weak acid and base equilibria

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HNO_{2} (a q) + H_{2} O (l) ⇌ H_{3} O^{+} (a q) + NO_{2}^{-} (a q)

The ionization of the weak acid

HNO_{2}

in water is represented by the equation above.

What is the percent ionization of $HNO_{2}$ ‍ in $1.5 M HNO_{2} (a q)$ ‍? (For $HNO_{2} (a q)$ ‍, $K_{a} = 5.6 \times 10^{- 4}$ ‍.)
Write your answer using two significant figures.

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The AP Chemistry exam includes a section of equations and constants that you can reference during the exam. A subset of this reference is shown below.

Acids and bases equations:

\begin{aligned} K_{a} & = \frac{[H_{3} O^{+}] [A^{-}]}{[HA]} \\ K_{b} & = \frac{[HB^{+}] [OH^{-}]}{[B]} \\ K_{w} & = [H_{3} O^{+}] [OH^{-}] = 1.0 \times 10^{- 14} at 25 ° C \\ = K_{a} \times K_{b} \\ pH & = - \log [H_{3} O^{+}], pOH = - \log [OH^{-}] \\ 14.00 & = pH + pOH \\ p K_{a} & = - \log K_{a}, p K_{b} = - log K_{b} \end{aligned}

Acids and bases constants:

\begin{aligned} K_{a} (weak acid) \\ K_{b} (weak base) \\ K_{w} (water) \end{aligned}

AP®︎/College Chemistry

Course: AP®︎/College Chemistry > Unit 8

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