ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: VCEMan94 on March 21, 2011, 09:09:41 pm
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How would you minimize the errors associated with the differences between endpoint/equivalence point in a titration, since the indicator used may sometimes have a broad range of pH values that it changes colour for
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Calculate it by stoic and then fake your prac results.
Nah, well really just get the list of common errors such as the one below (credits to thushan) and avoid those. Most of them are common sense with how to avoid them really... The main one I can think of with colour changes of indicators is to go slowly.
Anyway to other possible sources of error - i usually have:
- parallax
- in transferring solution into conical flask, not wiping outside of pipette after sucking up liquid (this causes more than the accurate amount of liquid to be transferred)
- not washing down conical flask after transferring solution from pipette and touching to side of flask to remove correct amount of liquid
- not leaving the correct amount of liquid in the pipette after transferring into flask
- not washing down flask with wash bottle just before endpoint (need to do this because you're swirling flask during titration)
- endpoint/equivalence point discrepancies (eg. incorrect indicator used, endpoint occurring only after excess reagent is added, etc.)
- not using half-drops in titrations
- careless errors (eg. washing volumetric glassware with wrong reagent, washing conical flasks with reagent, leaving funnel in burette during titration, etc.)
- washing storage beakers with water immediately before storing reagent in it (dilutes reagent)
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hmm okay
but if i was to write this in order to minimize:
Use a PH meter
Do a rough titration and see how far you can go before you overshoot
Add the acid solution drop by drop/go slowly
Use a reference sample to see what colour you need to achieve before stopping
would that be okay?
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hmm okay
but if i was to write this in order to minimize:
Use a PH meter
Do a rough titration and see how far you can go before you overshoot
Add the acid solution drop by drop/go slowly
Use a reference sample to see what colour you need to achieve before stopping
would that be okay?
Sounds good to me. Some of the Chem pros might have more to add though.
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in a back titration to find amount of nitrogen in fertiliser
would rinsing pipette with water
mean that your NaOH would become diluted and you would end up getting an overestimation?