Question

what will the ph be for solution Q??

PROCEDURE The pH meter should already be calibrated at pH 4, 7 and 10. If your pH meter appears not to be operating properly, notify your TA and they will recalibrate the meter. Please handle the pH probe carefully; the tip is made of a fragile glass membrane. Be sure to rinse the probe with DI water and blot it dry with a Kimwipe whenever it is transferred from one solution to another. Part 1: Mixing Ratios 1. Set up two burets, one for acetic acid (HC,H,O,) and one for sodium acetate (NaC,H,O,). Obtain about 100 mL of 0.5 M acetic acid and 100 mL of 0.5 M sodium acetate from the stock bottles 2. Make the following mixtures and record the pH of the resulting solutions. Solution ID Volume of 0.5 M acetic acid (mL) Volume of 0.5 M sodium acetate (mL) Volume of DI water (mL) 15.0 15.0 0.0 15.0 3.0 12.0 3.0 15.0 12.0 15.0 1.5 13.5 1.5 15.0 13.5 3. Keep solution A for use in Part II and Part III. Keep solution for use in Part III

Answer 1

Solution C:

Millimoles of acetic acid = 3 mL * 0.5 mmol/mL = 1.5 mmol

Millimoles of sodium acetate = 15 mL * 0.5 mmol/mL = 7.5 mmol

Total volume = 3+15+12 = 30 mL

Solution Q:

10 mL of solution C contains 1.5/3 = 0.5 mmol of acetic acid, 7.5/3 = 2.5 mmol of sodium acetate.

Millimoles of NaOH = 10 mL * 0.1 mmol/mL = 1 mmol

The resulting millimoles of NaOH = 1-0.5 = 0.5 mmol

The resulting millimoles of sodium acetate = 2.5 + 0.5 = 3 mmol

Total volume = 10+10 = 20 mL

Now, [NaOH] = [OH^-] = 0.5 mmol/20 mL = 0.025 M

Now, pOH = -Log[OH^-] = -Log(0.025) = 1.6

Hence, pH = 14 - pOH = 14 - 1.6 = 12.4