Which of the following mixtures, with each component present at a concentration of 0.1 M, has a pH closest to 7? O A. HCIO (aq) and NaCIO (aq) O B. HNO2 (aq) and NaNO2 (aq) O C. CH3COOH (aq) and NaCH3COO (aq) O D. HNO3 (aq) and NaNO3 (aq)

The answer is: A. HCIO (aq) and NaCIO (aq

Explanation:

From buffers, the pH is equal:

pH = pKa + log ([salt]/[acid])

[sal] = [acid] = 0.1 M

Replacing:

pH = pKa + log (0.1/0.1)

pH = pKa + 0

pH = pKa

According to this:

pKa of HClO ≅ 7.54

pKa of HNO₂ ≅ 3.15

pKa of CH₃COOH ≅ 4.74

Then, the mix that present a pH closest to 7 is HClO and NaClO

for HClO, pKa = 7.54

for HNO_2, pKa = 3.15

for CH3 COOH, pKa = 4.74

Explanation:

The concentration of the solution given is 0.1 M has a pH closest to 7

The mixtures are weak acids and their salts except

HNO_3 and NaNO_3 pH = pH is near to '1'

for buffers (acidic) pH = pKa + log [salt] / [acid]

therefore [salt] = [acid] = 0.1 pH = pKa + log 0.1 / 0.1 = pKa

pH = pKa

for HClO, pKa = 7.54

for HNO_2, pKa = 3.15 therefore HClO and NaclO

mixture hs a pH closest to '7'

for CH3 COOH, pKa = 4.74