# chemistry

posted by .

How many grams of NH4Cl must be added to 0.490 L of 1.70 M NH3 solution to yield a buffer solution with a pH of 9.40? Assume no volume change. Kb for NH3 = 1.8 10-5.

• chemistry -

pH = pKa + log[(base)/(acid)]
Convert Kb for NH3 into Ka and pKa, substitute into the H-H equation (1.70 for (base), and solve for (acid) in moles/L. Then convert to grams NH4Cl in 0.490 L. Post your work if you get stuck.

• chemistry -

I still have it wrong. I have pKa = 9.25. Solved for acid and got 2.39. Then I converted to grams and 62.25. Here's my work ka = 1.0e-14/1.8e-5 = 5.56e-10. solved for pKa -log(5.56e-10) = 9.25. H-H = 9.40=9.25 + log(1.70/acid). acid = 2.39. then, 2.39 x 0.490L = 1.17 M. then 1.17 x 53.4g = 62.65g

## Similar Questions

1. ### science

How many grams (to the nearest 0.01 g) of NH4Cl (Mm = 53.49 g/mol) must be added to 700. mL of 1.294-M solution of NH3 in order to prepare a pH = 9.70 buffer?
2. ### Chemistry

A 100 milliliter sample of 0.100-molar NH4Cl solution was added to 80 milliliters of a 0.200-molar solution of NH3. The value of Kb for ammonia is 1.79 x 10^-5. (a) What is the value of pKb for ammonia?
3. ### Chemistry

A 100 milliliter sample of 0.100-molar NH4Cl solution was added to 80 milliliters of a 0.200-molar solution of NH3. The value of Kb for ammonia is 1.79 x 10^-5. (a) What is the value of pKb for ammonia?
4. ### chemistry

A buffer solution is 1.00 M in NH3 and 1.10 M in NH4Cl. If 0.230 moles of NaOH are added to 1.00 L of the buffer, what is its pH?
5. ### chemistry

A buffer system is created by neutralizing the supernatant solution containing Pb^2+, Fe^3+, Al^3+, Ca^2+, Cu^2+, and K^+ ions with 6M NH3 solution and then adding an equal volume of 6M NH3 solution. Explain what forms of 6M NH3 were …

'A buffer is prepared by mixing a 100.omL of a 0.100 M NH3 solution with a 0.200M solution of NH4CL solution and making the total volume up to 1.000L of water. What is the volume of NH4Cl solution required to achieve a buffer at ph=9.5?
7. ### Chemistry

If some NH4Cl is added to an aqeous solution of NH3: A. pH of solution will decrease B. PH will not change C. pH will increase D. NH4Cl cannot be added to NH3 E. The solution will not have pH I think the answer is B, because if NH4Cl …
8. ### chem

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?
9. ### Chemistry

A buffer solution is prepared by mixing 50.0 mL of 0.300 M NH3 with 50 mL of 0.300 NH4Cl. The pKb of NH3 is 4.74. NH3 + H2O-> NH4+ +OH- 7.50 mL of 0.125 M HCl is added to the 100 mL of the buffer solution. Calculate the concentration …
10. ### Chemistry

A solution is 0.10M in aqueous NH3. Calculate (a) the number of moles and (b) the number of grams of NH4Cl that must be added to 500mL of this solution to prepare a buffer solution with pH=9.15. You may neglect the volume change due …

More Similar Questions