chemistry

posted by .

COMMON ION EFFECT
1.) What is the pH of a solution that is 0.30M in HCOOH and 0.52M in HCOOK.
Ka of HCOOH=1.7x10^-4.
2.) Calculate the pH of a buffer system containing 1.0M CH3COOH and 1.0M CH3COONa. Ka of CH3COOH=1.8x10^-5.

  • chemistry -

    1)
    I notice that your value for Ka in the question is missing units, were these missing in the original question?

    Start from the equation for the equilibrium reaction

    HCOOH<->H+ + HCOO-

    at start
    0.30M

    at equilibrium if [H+]=x

    0.30-x x x

    there is also 0.52M HCOO-

    so at equilibrium

    0.30-x x x+0.52

    Ka=[H+][HCOO-]/[HCOOH]

    Ka=(x)(x+0.52)/(0.30-x)=1.7x10^-4

    (x)(x+0.52)/(0.30-x)=1.7x10^-4


    You can either solve the quadratic or we can say that if x is small with respect 0.52 abd 0.3, we can rewrite the expression as

    (x)(0.52)/(0.30)=1.7x10^-4

    and find x

    pH is then -log (x/mol litre^-1)

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. chemistry

    How many grams of potassium formate, KHCOO, must be added to 500 mL of a .07 M solution of HCOOH to produce a buffer solution with a pH of 3.50?
  2. chemistry

    A. Strong Base 1.) What is the concentration of a solution of KOH for which the pH is 11.89?
  3. Chemistry

    Find the pH of mixture of acids. 0.185 M in HCHO2 and 0.225 M in HC2H3O2 Im using an ice chart of weak acid and putting in strong acid in H+ initiAL concentration. I've done the problems many different ways but cannot seem to get the …
  4. chem 2

    a buffer is to be prepared by adding solid sodium acetate to 0.10M CH3COOH. Which othe following concentrations of sodium acetate will produce the most effective buffer?
  5. chemistry

    What mass of solid sodium formate (of MW 68.01) must be added to 115 mL of 0.57 mol/L formic acid (HCOOH) to make a buffer solution having a pH of 4.16?
  6. chemistry

    You have to prepare a pH 5.00 buffer, and you have the following 0.10M solutions available: HCOOH, HCOONa, CH3COOH, CH3COONa, HCN, and NaCN. Which solutions would you use?
  7. Chemistry

    calculate the initial concentration of HCOONa you would add to 0.10M HCOOH to make a buffer with a pH of 4.00 [Ka (HCOOH) = 1.8 x 10^-4]
  8. Chemistry

    Find the pH of a buffer solution with equimolar concentrations of: HCOOH and NaCOOH (Ka = 3.5 x 10-4 for HCOOH)a
  9. Chemistry Help

    The most effective buffer solutions have equal concentrations of salt and acid (or base). Find the pH of a buffer solution with equimolar concentrations of: (a) HCOOH and NaCOOH (Ka = 3.5 x 10-4 for HCOOH) (b)CH3NH2 and CH3NH3Cl (Kb …
  10. chemistry

    calculate tge pH of a buffer system containing 1.0M CH3COOH and 0.1M CH3COONa

More Similar Questions