Question

Calculate the ph of a solution obtained by mixing 400ml of 0.10M hydrochloric acid with 600ml of 0.10M sodium hydroxide. Assume the combined volume is the sum of the two original volumes

Answer 1

The pH of the solution obtained by mixing 400 ml of 0.10M HCl with 600 ml of 0.10M NaOH is neutral, as the strong acid and base neutralize each other, with excess NaOH determining the final pH.

Step-by-step explanation:

Calculating the pH of a Mixed Solution

To calculate the pH of a solution obtained by mixing 400 ml of 0.10M hydrochloric acid (HCl) with 600 ml of 0.10M sodium hydroxide (NaOH), we must first determine the moles of HCl and NaOH. Hydrochloric acid is a strong acid and sodium hydroxide is a strong base. When mixed, they will neutralize each other according to the reaction: HCl + NaOH → NaCl + H2O.

First, calculate the moles of HCl and NaOH:

• Moles of HCl = volume (L) × concentration (M) = 0.400 L × 0.10 M = 0.040 moles
• Moles of NaOH = volume (L) × concentration (M) = 0.600 L × 0.10 M = 0.060 moles

Since NaOH is in excess (0.060 moles - 0.040 moles), we have 0.020 moles of NaOH remaining. The total volume of the solution is 400 ml + 600 ml = 1000 ml or 1.0 L.

The concentration of NaOH in the new solution is 0.020 moles / 1.0 L = 0.020 M. The pOH of this solution can be found using the formula pOH = -log[OH-], and thus pOH = -log(0.020). The pH can then be found since pH + pOH = 14. Therefore, pH = 14 - pOH.