chem

posted by .

what is the pH change after the addition of 10mL of 1.0M sodium hydroxide to 90mL of a 1.0M NH3/1.0M NH4^+ buffer? Kb ammonia= 1.8 x 10^-5

i found the pH for the original buffer to be 9.255, but i'm not sure how to go about the rest of the question, please, someone help me.

  • chem -

    I would do this.
    I assume you used the HH equation to arrive at the answer of 9.255 (with which I agree). At that time you substituted 1M each for base and acid and log 1 = 0 which makes pH = pKa. When you do that base/acid = 1 which means (base) = (acid) and the total is 1M.
    90mL x 1M = 90 millimoles total or
    45 mmols base and 45 mmoles acid.
    The equation for the addition of NaOH is
    ............NH4+ + OH^- ==> NH3 + H2O
    initial.....45.....0........45......0
    add OH-............10...............
    change.....-10....-10.....+10......+10
    equil.......35.....0........55......10

    pH = 9.255 + log(55/35) = ??
    I would round the final answer to 2 places.

  • chem -

    oh! i get it now, thank you very much =)

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. college chemistry

    How do you calculate the pH difference when the following substances are added to a buffer.(all of the solutions are at .10M conc.) The buffer: 50mL NH3 + 50mL NH4NO3 1) 10mL buffer + 6mL water 2)10mL buffer + 5mL water +1mL HCl 3)10mL …
  2. college chemistry

    How do you calculate the pH when the following substances are added to a buffer.(all of the solutions are at .10M conc.) The buffer: 50mL NH3 + 50mL NH4NO3 1) 10mL buffer + 6mL water 2)10mL buffer + 5mL water +1mL HCl 3)10mL buffer …
  3. chemistry

    How do you calculate the pH when the following substances are added to a buffer.(all of the solutions are at .10M conc.) The buffer: 50mL NH3 + 50mL NH4NO3 1) 10mL buffer + 6mL water 2)10mL buffer + 5mL water +1mL HCl 3)10mL buffer …
  4. chem buffer

    When the following solutions are mixed, which will act as a buffer?
  5. chem

    The pH of the nitrite buffer has changed from 3.00 to 2.80 by adding 11.0mL of 12.0M HCL. How many grams of solid sodium Hydroxide would the chemist add to the buffer to change the pH from 3.00 to 3.80?
  6. chemistry

    1L of a buffer composed of NaHC2O4 and Na2C2O4 has a pHof 4.0 and a total molarity of 1. a). what would the effect on the pH be of adding 1 gram of sodium hydrogen oxalate to this buffer?
  7. chemistry

    1L of a buffer composed of acetic acid and sodium acetate has a pH of 4.3. Adding 10mL of 2M sodium hydroxide solution to 100mL of this buffer causes the pH to rise to 4.87. what is the total molarity of the original buffer?
  8. Chemistry

    Calculate the pH of the 0.20 M NH3/0.25 M NH4Cl buffer. I calculated the pH to be 9.15 What is the pH of the buffer after the addition of 10.0 mL of 0.10 M HCl to 72.5 mL of the buffer?
  9. Chemistry

    20 ml of 0.1 M acetic acid was mixed with 25 ml of 0.1 M Sodium Acetate. The pH was measured to be 4.43. 5 ml of 0.1 M Sodium Hydroxide was added to the buffer and the pH was measured to be 4.60. Calculate the pH of the buffer before …
  10. chemistry

    What is the change in ph after addition of 10.0 ml of 1.0 m sodium hydroxide to 90.0 ml of a 1.0 m nh3/1.0 m nh4+ buffer?

More Similar Questions