A 0.20 M solution of a weak acid has a pH of 2. What is the % dissociation? 1% 2

Question

A 0.20 M solution of a weak acid has a pH of 2. What is the % dissociation? 1% 2% 4% 5% 12.5% The K_a for hypochlorous acid (HCIO) is 3.5 times 10^-8. What is the pH of a 1.50M solution? 11.3 5.1 4.3 3.6 1.8 Use the following information for questions. A Weak acid (H_2A) has a K_a1 of 1.26 times 10^-6 and a K-a2 of 8.0 times 10^-9. What is the pH of a 0.20M solution? 4.13 4.5 5.6 2.1 3.3 What is the concentration of the A^2 ion in the 0.20M solution? 4.0 times l0^-9 3.7 times 10^-4 8.0 times 10^9 7.4 times 10^-4 1.9 times 10^-2 A weak acid HA has a K_a value of 5.0 times 10^-4. What is the K for the following reaction? A + H_2O doubleheadarrow OH + HA 2.0 times 10^-4 5.0 times 10^-11 5.0 times 10^-12 2.0 times 10^-11 1.0 times 10^-14 Determine the K_sp of BaSO_4 if it has a solubility of 0.778mg/L. MM(BaSO_4) = 233 4g/mol 1.5 times 10^-5 3.4 times 10^-7 1.1 times 10^-11 4.0 times 10^-11 3.6 times 10^-12. Determine the solubility (in g/L) of AgBr in a 0.30M solution of NaBr. (K_sp, (AgBr) = 5.0 times 10^-13, MM = 188g/mol) 1.2 times 10^-10 3.1 times 10^-10 1.3 times 10^-5 2.1 times 10^-5 3.3 times 10^-1 Mg(OH)_2 has a K_sp of 56 times 10^-12. What would be the pH of a saturated solution of this salt? 3.8 10.3 10.1 112 11.

Explanation / Answer

Question 19.

Solution of acid = 0.2 M

pH = 2

for dissociation %:

The formula we need is

% dissociation = [A-]/M * 100%

where [A-] = dissociated acid in equilibrium

M = initial concnetration of acid

then

[H+] = 10 ^ -pH = 10 ^-2 = 0.01

note that in equilbirium

[A-] = [H+] = 0.01

so

we can now substitute in equation

%dissociation = 0.01/0.2 * 100 = 5%

best answer is D

5%

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