Posted by **hannah** on Tuesday, March 19, 2013 at 7:59pm.

How many grams of NH4Cl must be added to 0.560 L of 1.90 M NH3 solution to yield a buffer solution with a pH of 8.50? Assume no volume change. Kb for NH3 = 1.8 10-5.

i am confused as how to find the grams?

- chem -
**Devron**, Tuesday, March 19, 2013 at 9:53pm
Let B= NH3 and BH=NH4Cl

pH+pOH=14

so, 14-8.50=pOH

and

pkb=-logkb

You will need to use a version of the henderson-hasselbalch equation.

pOH=pkb +log[BH/B]

Solve for the ratio,

So, [BH/B]= 0.755

0.560L*(1.90M)= moles of NH3

Substituting, you should have

0.775=BH/moles of NH3

Solve for BH

moles of BH*(53.49 g/mole)= mass of NH4Cl

- chem -
**DrBob222**, Tuesday, March 19, 2013 at 10:32pm
I should point out here that you do not need to modify the Henderson-Hasselbalch equation.

pH = pKa + log (base)/(acid) is valid for acids and bases. In this case we calculate pKb from Kb, then

14-pKb = pKa, then proceed with the HH equation as usual.

8.50 = 9.25 + log (1.90/x)

Solve for x which is molar NH4Cl and convert to grams in 0.560 L.

## Answer this Question

## Related Questions

- chemistry - How many grams of NH4Cl must be added to 0.490 L of 1.70 M NH3 ...
- Chemistry - A buffer solution is prepared by mixing 50.0 mL of 0.300 M NH3 with ...
- Chemistry - If some NH4Cl is added to an aqeous solution of NH3: A. pH of ...
- chemistry - A buffer solution is 1.00 M in NH3 and 1.10 M in NH4Cl. If 0.230 ...
- science - How many grams (to the nearest 0.01 g) of NH4Cl (Mm = 53.49 g/mol) ...
- Chemistry - A 100 milliliter sample of 0.100-molar NH4Cl solution was added to ...
- Chemistry - A 100 milliliter sample of 0.100-molar NH4Cl solution was added to ...
- college chem - The cation M2+ reacts with NH3 to form a series of complex ions ...
- CHEM 112 - A buffer solution is 1.40 M in NH3 and 1.00 M in NH4Cl. If 0.100 ...
- CHEM 112 - A buffer solution is 1.40 M in NH3 and 1.00 M in NH4Cl. If 0.100 ...

More Related Questions