How do I work out what the Molarity and the pKa is for the solution. I started w

Question

How do I work out what the Molarity and the pKa is for the solution. I started with 15ml of NH4CL and added 15ml of NH3. When I tested the solution the pH was 10.33. Please explain how you did it so I can work out the Molarity and pKa for the diluted solution. I also attached a pic of the 4b equation it's asking to use. Na,CO ph Color For any two solutions having a pl lssham 6 or greater than 8, write a nersogic equation to explain qualita tively why the solution has that Solution Equation Equation wthy the color observed with bromcresol green for each of the four solutions is reasonable. given the pH C. Some Properties of Buffers HB is (name the acid) Buffer system selected 5Ml of . pt of buffer 10.33 H MpK, (by Eq. 4b) 2. pit of dileted bulfer 10.30 (H pk, PH after addition of 5 drops NaOH pli after addition of 5 drops HCI Comment on your observations in Parts 1 and 2 10.13 (continued on following page)

Explanation / Answer

The equation 4.b is general for buffer calculation.

pH = pKa + log ([NH3]/[NH4+])

Here NH3 is the base and NH4+ is the conjugate acid in the buffer.

[NH3] = [NH4+] = 0.1 M/2          (/2 for reciprocal dilution)

But the molarity of the undiluted buffer remains 0.1 M (the sum [NH3] + [NH4+] ).

and log 1 = 0

Thus pKa = pH = 10.3

The molarity of the diluted buffer is 0.1M divided by the dilution factor (you didn’t provided it).

[H+] = 10-pH by definition. Thus:

[H+] = 10-10.33 = 5.0 x10-11 M

[H+] = 10-10.30 = 4.7 x10-11 M

[H+] = 10-10.18 = 6.6x10-11 M

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.