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For nitrous acid, hno2, ka = 4.0 × 10–4. calculate the ph of 0.33 m hno2.

2 Answers

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Final answer:

To find the pH of a 0.33 M nitrous acid solution, we calculate the concentration of H⁺ ions using the given Ka value and the initial acid concentration. We find that the pH of the solution is approximately 1.96.

Step-by-step explanation:

To calculate the pH of a 0.33 M solution of nitrous acid (HNO2) with a given Ka of 4.0 × 10⁻⁴, we need to set up the dissociation equation for the weak acid:

HNO2 (aq) → H⁺ (aq) + NO2⁻ (aq)

At equilibrium, the concentrations of the products and reactants are related by the acid dissociation constant (Ka):

Ka = [H⁺][NO2⁻] / [HNO2]

Assuming x is the amount of HNO2 that dissociates, the concentration of H⁺ and NO2⁻ will both be x and the concentration of undissociated HNO2 will be 0.33 - x. Since HNO2 is a weak acid, x will be much smaller than 0.33 and can be ignored, simplifying the equation to:

Ka = x² / 0.33

Solving for x gives:

x = √(Ka × 0.33) = √(4.0 × 10⁻⁴ × 0.33) ≈ 1.1 × 10⁻²

The concentration of H⁺ (which is the same as [H3O⁺]) is approximately 1.1 × 10⁻² M. To find the pH, we take the negative logarithm:

pH = -log([H⁺]) = -log(1.1 × 10⁻²) ≈ 1.96

Thus, the pH of the 0.33 M HNO2 solution is approximately 1.96.

User Arnaud Grandville
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6 votes

Final answer:

The pH of a 0.33 M HNO₂ solution is approximately pH = 0.48.

Step-by-step explanation:

The pH of a solution can be calculated using the formula pH = -log[H+]. In this case, we are given the concentration of nitrous acid (HNO₂) as 0.33 M. To find the pH, we need to calculate the concentration of hydronium ions ([H₃O+]). Since nitrous acid is a weak acid, we can assume that the concentration of [H₃O+] is the same as the concentration of HNO₂₂. Therefore, the pH of the 0.33 M HNO₂ solution is approximately pH = -log(0.33) = 0.48.

User Mjandrews
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