How much water should be added to 10.0 mL of 12.0 M HCl so that it has the same pH as 0.90 M acetic acid (K_a = 1.8 × 10^-5)? (Assume the volumes are additive.) A) 30 mL B) 3 L C) 30 L D) 300 L E) 300 mL

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Quizplus · Accepted Answer

To find the pH of 0.90 M acetic acid, use the formula for weak acids: pH = -log(√(Ka * [HA])). For 0.90 M acetic acid, pH ≈ 2.52. To dilute 12.0 M HCl to the same pH, it must be diluted to approximately 0.003 M. Using the dilution formula (C1V1 = C2V2), solve for V2: (12.0 M)(10.0 mL) = (0.003 M)(V2), giving V2 ≈ 40,000 mL or 40 L. Therefore, 40 L - 10 mL ≈ 30 L of water is needed.

How Much Water Should Be Added to 10