Chem

posted by .

A) Calculate the pH of a buffer system that is 0.06 M HNO2 and 0.160 M NaNO2

B) What is the pH after 2.00 M NaOH are added to 1.00 L of this buffer

I can do part A but I don't know how to part B

  • Chem -

    The easiest way is to work up an ICE chart as below. I like to work in millimoles. For the original buffer, if we have 1L of the original buffer, we will have the following millimoles of HNO2 and NaNO2.
    mmoles HNO2 = 0.06M x 1000 mL = 60
    mmoles NaNO2 = 0.160M x 1000 mL = 160

    You don't say how much 2M NaOH is added to the buffer. I will use 1.0 mL of 2M = 2.0 mmoles.

    ..........HNO2 + OH^- ==> NO2^- + H2O
    initial...60......0........160
    added............2.0...........
    change...-2.0....-2.0......+2.0
    equil......58.....0.........162

    Then pH = pKa + log(base)/(acid)
    pH = pKa + log (162/58) = ??

  • Chem -

    By the way, the correct way is to work in M (and not millimoles) so that for (base) we substitute moles/L which will be 162 mmoles/1001 mL = ?? and for (acid) we substitute 58 mmoles/1001 mL. So the HH equation looks like this.
    pH = pKa + log (162/1001)/(58/1001) BUT you notice that the 1001 denominator in each cancels so we are left with 162/58. After working a few thousand of these problems I think in terms of millimoles because I know the volume part will ALWAYS cancel. I mention this because some profs count off for using millimoles and not the "real" concn term. (I did in my classes.) I tried to get the students into the habit of writing
    pH = pKa + log(162/V)/(58/V) and the Vs cancel no matter what V is. That way we don't need to do an extra division for the numerator and another division for the denominator before finding the fraction for mmols base/mmols acid.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. chemistry

    A buffer is prepared by dissolving .0250 mol of sodium nitrite, NaNO2, in 250.0 mL of .0410 M nitrous acid, HNO2. Assume no volume change after HNO2 is dissolved. Calculate the pH of this buffer. My book does a poor job of explaining …
  2. chem

    a buffer is made by adding 150 ml of .595M BaF2 and 0f .500M of HF solution. calculate the pH of this buffer system calculate the pH of this buffer after adding .100 mol Hcl calculate the pH of this buffer after adding .0750 mol Ca(OH)2 …
  3. chemistry AP

    You have to design a buffer based on one of the systems below System 1: HA1 and A1-1 K= 4 E-3 System 2: HA2 and A2-1 K= 5 E-4 System 3: HA3 and A3-1 K= 6 E-5 For the following parts assume that the buffer above in system2 has been …
  4. chemistry AP

    You have to design a buffer based on one of the systems below System 1: HA1 and A1-1 K= 4 E-3 System 2: HA2 and A2-1 K= 5 E-4 System 3: HA3 and A3-1 K= 6 E-5 For the following parts assume that the buffer above in system2 has been …
  5. Chemistry

    Calculate the pH of 1.00L of a buffer that is 0.120M HNO2 and 0.150M NaNO2 before and after the addition of 1.00mL of 12.0M HCl
  6. chem

    Which of the following solutions represent a buffer system?
  7. Chemistry

    500 ml of a buffer solution with ph=2.10 must be prepared using .4 M HNO2 and solid KNO2. The ka value of HNO2 is 4e-3. a.) What mass of KNO2 should be added to 3 L of the HNO2 to make the buffer?
  8. chemistry

    a 2.00l buffer contains 1.00 mol HNO3 mixed with 1.00mol NaNO2 a. write the relevant ionization equation for this buffer. b. determine its pH c. determine the new pH if 1.00g of NaOH is added to the buffer.
  9. chemistry

    a 2.00l buffer contains 1.00 mol HNO3 mixed with 1.00mol NaNO2 a. write the relevant ionization equation for this buffer. b. determine its pH c. determine the new pH if 1.00g of NaOH is added to the buffer
  10. Chemistry

    How many grams of NaNO2 must be added to 1 liter of 1.00 M HNO2 solution in order to prepare a buffer solution with pH = 4.14?

More Similar Questions