Equation for a solution of a weak acid, HA, and its salt NaA...?

derive the Henderson-Hasselbalch equation for a solution of
a weak acid, HA, and its salt NaA...

I have an answer for a solution of a weak acid HA:|
pH = pKa + log10([A-]/[HA])

But the problem is , when the salt NaA (sodium acid) is included, I don't know how to derive it...

Need help anyone? :(

Answer:
NaA is not sodium acid but is a salt
We consider the solution made by adding HA and NaA.
NaA is a strong electrolyte and it will be dissociated 100% into Na+ and A-
The equilibrium is
HA <> H+ + A-
at equilibrium
[HA] = initial molarity HA - x
[ H+] = x
[ A-] = x + initial molarity NaA
K = [H+] [A-] / [HA]
x is small enought to be neglected when added or subctracted from initial molarities
[H+] = K x [HA] / [A-]
log [H+] = log K + log [HA]/ [A-]
- log [H+] = - log K - log [HA]/[A-]
pH = pK + log [A-] / [HA]

The answers post by the user, for information only, FunQA.com does not guarantee the right.



More Questions and Answers:
  • Can someone help me get the chemical equations for the following?
  • Chemistry lab questions?
  • What is the product when 1 pentanol is oxidized? What about 2 pentanol?
  • Does anyone know an element that can help the sense of smell?
  • Is there any alternative to using helium to make balloons float?
  • What can be inferred about the chemical nature of of Nutrasweet/aspartame?
  • Distinguish between a water condenser and an air condenser. When may an air condenser be used?
  • Lewis Dot Structure for NO2-, Electron Geometry and Bond Angle?
  • What mass of nitrogen gas must be released into an 18 L automobile air bag if the pressure in the bag is to be