A solution is prepared by mixing 100 mL of 0.3 M weak acid HA with 100 mL of 0.2 M NaOH . If the dissociation constant of the weak acid HA is 2 10⁻⁵ , the pH of the resulting solution is _______.

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The reaction between the weak acid HA and the strong base NaOH is: HA + NaOH NaA + H ₂ O Initial millimoles of HA = 100 0.3 = 30 mmol Initial millimoles of NaOH = 100 0.2 = 20 mmol Since NaOH is the limiting reagent, it will completely react to form 20 mmol of the salt NaA . Remaining millimoles of HA = 30 - 20 = 10 mmol The resulting solution is an acidic buffer containing HA and NaA . According to the Henderson-Hasselbalch equation: pH = p K_ a + ( [ Salt ] [ Acid ] ) Given K_ a = 2 10⁻⁵ , we have: p K_ a = - (2

A solution is prepared by mixing 100 mL of 0.3 M weak acid HA with 100 mL of 0.2 M NaOH . If the dissociation constant of the weak acid HA is 2 10⁻⁵ , the pH of the resulting solution is _______.

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