Posted by **Elizabeth** on Wednesday, November 10, 2010 at 4:51pm.

Discuss how to prepare 250.0 ml of an ammonium-ammonia buffer (pkb = 4.70), ph = 9 and total concentration of 0.05M using 0.10 M ammonium chloride and 0.10M aqueous ammonia

- Please help -
**Elizabeth**, Wednesday, November 10, 2010 at 6:38pm
Need answer tomorrow for pre-lab Thanks

- Chemistry -
**DrBob222**, Wednesday, November 10, 2010 at 8:54pm
Use the Henderson-Hasselbalch equation.

pH = pKa + log (base/acid)

pKb = 4.70; therefore, pKa = 14.0-4.70 = 9.3

Solve two equations simultaneously.

Plug in 9.0 for pH and solve for (B/A) and I get 0.501 which you should confirm. If B/A = 0.501 then

(Base) = 0.501*(acid)

The second equation is

(base) + (acid) = 0.05

Solve for base and acid. I get something like

(acid) = 0.0333 M

(base) = 0.0167 M

We have two solutions, both 0.1 M with which to make this. Use a dilution process (formula) to determine how much of each should be taken.

0.1M x (x Liters/0.25 L) = 0.0333 M.

Solve for x = 0.08325 L or 83.25 mL acid.

0.1 M x (x liters/0.25) = 0.0167 M

Solve for x = 0.04175 L or 41.75 mL base.

Therefore, the instructions would be to measure 83.25 mL of NH4Cl and 41.75 mL NH3, place in a 250 mL volumetric flask and make to the mark with water. But you shouldn't stop there. You should go through and prove four things.

1. The final solution is 250 mL.

2. The final solution is 0.05 M.

3. The final (acid) is 0.0333 (or whatever value you find above) and the final (base) = 0.0167 (or whatever value you find above.)

4. The final pH is 9.0.

- Chemistry -
**Elizabeth**, Wednesday, November 10, 2010 at 10:14pm
Thanks!

## Answer This Question

## Related Questions

- Chemistry - A buffer solution of pH=9.24 can be prepared by dissolving ammonia ...
- Science - Hydrogen chloride is added to a buffer solution of ammonia, NH3, and ...
- chem - Calculate the ph of a buffer solution that is 0.10M in ammonia and 0.15M ...
- Chemistry - Calculate the pH of: a) ammonia, 0.1M, in water b) ammonium chloride...
- chem buffer - When the following solutions are mixed, which will act as a ...
- AP Chemistry - Consider ammonia, what is the pH of a buffer solution prepared by...
- chemistry - How many grams of solid ammonium chloride should be added to 1.50 L ...
- chemistry help - What mass of ammonium chloride must be added to a 0.500 L ...
- chemistry - What mass of ammonium chloride must be added to a 0.500 L solution ...
- chemistry - Concentrated ammonium hydroxide (aq ammonia) has a density of 0.90g/...

More Related Questions