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pH of a Solution

Carbonic acid...

Question

Carbonic acid, $H_{2} C O_{3}$ , is a diprotic acid for which $K_{1} = 10^{- 7}$ and $K_{2} = 10^{- 11}$ . Which solution will produce a pH closet to $9$ ?

0.1

H_{2} C O_{3}

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0.1

N a_{2} C O_{3}

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0.1

N a H C O_{3}

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0.1

N a H C O_{3}

and

0.1

N a_{2} C O_{3}

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Solution

The correct option is A $0.1$ M $H_{2} C O_{3}$
$H_{2} C O_{3} ⇌ {H C O_{3}}^{-} + H^{+}$ $K_{1} = 10^{- 7}$
${H C O_{3}}^{-} ⇌ C O_{3}^{-} + H^{+}$ $K_{2} = 10^{- 11}$
For $0.1 M$ $H_{2} C O_{3}$ ,
$p H = \frac{p k_{1} + p k_{2}}{2} = \frac{- log 10^{- 7} - log 10^{- 11}}{2} = \frac{7 + 11}{2} = 9$

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Similar questions

0.1

N a H C O_{3}

K_{1}

5

\times

10^{- 7}

K_{2}

5

\times

10^{- 11}

N a H C O_{3}

K_{1} = 4.5 \times 10^{- 7}, K_{2} = 4.5 \times 10^{- 11}

H^{+}

H_{2} C O_{3}

(K_{1} = 4 \times 10^{- 7}, K_{2} = 4 \times 10^{- 11}) :

Δ p H

N a H C O_{3}

(i n i t i a l p H = 9, K a_{1} = 10^{- 7}, K a_{2} = 10^{- 11}

H_{2} C O_{3})

Δ p H

N a H C O_{3}

p H = 9, K a_{1} = 10^{- 7}, K a_{2} = 10^{- 11}

H_{2} C O_{3}

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