~Christiano's Inquisition into Chemistry Thread~

[Christiano]

Hi all, just creating my own personal thread for questions, hope it'll be of help to myself as well as others!

First up:
Aliquot of standard sodium cabonate solution is titrated with hydrochloric acid in a burette. State whether the concentration determined for the HCl would be likely to be higher than, lower than or unchanged from the actual value if the student had previously washed with water, but not dried, the apparatus:

Pipette used to deliver the aliquot of sodium carbonate solution

Answer says concentration of HCl would be higher, however I thought that because the solution of sodium carbonate is slightly more dilute (due to the water leftover in the pipette), it would result in less concentration of HCl to neutralize the sodium carbonate because the amount of moles/L of sodium carbonate is less, hence requiring less moles/L of HCl to neutralize it. Flaw in my thinking?

[Mao]

Almost there.

- Actual concentration of NaOH is lower. Concentration of NaOH is overestimated.
- Actual mol of NaOH is lower. mol of NaOH is overestimated.
- Volume of HCl is lower. Since mol is overestimated, we therefore compensate for this by overestimating the concentration of HCl.

[Christiano]

What do you do to the standards in AAS in order to construct a calibration curve? Do you spray the standards into the flame as well?

[vea]

What do you do to the standards in AAS in order to construct a calibration curve? Do you spray the standards into the flame as well?

You would have to test the standards for their absorption so yes, spray them into the flame.