Calculate the pH of a 0.018 , M sodium acetat | vedclass

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Question

(A) Sodium acetate $(CH_3COONa)$ is a salt of a weak acid $(CH_3COOH)$ and a strong base $(NaOH)$.For such salts,the $pH$ is given by the formula: $pH

Vedclass · Accepted Answer

$8$

Vedclass · Answer

(A) Sodium acetate $(CH_3COONa)$ is a salt of a weak acid $(CH_3COOH)$ and a strong base $(NaOH)$.For such salts,the $pH$ is given by the formula: $pH = 7 + \frac{1}{2}pK_a + \frac{1}{2}\log C$.Given: $C = 0.018 \, M = 1.8 	imes 10^{-2} \, M$ and $K_a = 1.8 	imes 10^{-5}$.First,calculate $pK_a$: $pK_a = -\log(K_a) = -\log(1.8 	imes 10^{-5}) = 5 - \log(1.8) \approx 5 - 0.255 = 4.745 \approx 4.75$.Now,substitute the values into the formula:$pH = 7 + \frac{1}{2}(4.75) + \frac{1}{2}\log(1.8 	imes 10^{-2})$$pH = 7 + 2.375 + \frac{1}{2}(\log 1.8 + \log 10^{-2})$$pH = 7 + 2.375 + \frac{1}{2}(0.255 - 2)$$pH = 7 + 2.375 + \frac{1}{2}(-1.745)$$pH = 7 + 2.375 - 0.8725 = 8.5025 \approx 8.5$.

Calculate the $pH$ of a $0.018 \, M$ sodium acetate solution,given its $K_a = 1.8 \times 10^{-5}$. (in $.5$)

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