Soda Ash Flashcards
Soda ash is:
IMPURE sodium bicarbonate
What is the chemical name for sodium bicarbonate
Na2CO3
What technique is used in this experiment?
Back titration
What is a back titration? (2 stages, 4 bullet points)
- An excess of acid is added.
- The acid reacts completely with the carbonate
- solution boiled to remove CO2
- Excess acid is titrated with NaOH
What is the first stage of a back titration? (formula)
CO3^2- + H^+ HCO3^- + H^+
What is the second stage of a back titration? (formula)
H2CO3 H2O + CO2 .
What error would be introduced if you forgot to boil off the CO2?
The %Na2CO3 would be lower than expected because the NaOH would then react with the excess HCL + CO2. Then we would think the Na2CO3 took less HCL to titrate than expected, so the % purity would be lower
How much acid did we add?
2x+10 (mL)
The amount of HCL it took to titrate the soda ash is =
mol HCL added - mole NaOH added. (NaOH reacts away all the excess HCL)
mol Na2CO3 titrated =
mol HCL to titrate soda ash * (1/2)
If you had to leave lab and left before doing the back titration?
CO2 would dissolve back into the solution
Soda ash is used in…
flat glass for car manufacturers and building construction. plus other glass, chemicals and other detergents
The ____ in impure soda ash can be titrated using a _____ solution.
CO3^———-strong acid
At the half equivalence point….
moles acid [HA] = moles conjugate base [F-]
pink –> clear
After adding ‘x’ amount of acid, you’ve….
taken the CO3^2- —> HCO3^- (pink –> clear)
