Volumetric Analysis Flashcards
What are some systematic errors that occur during titration?
- Color changing indicators have a ‘lag’ to them in that they gradually change over time, as well as human reaction time
- End point of the reaction occurs after the equivalence point
- Calibration of equipment - rinsing the flask with water, pipette and burette with whatever is going in it
What is primary and secondary data
- Primary data is the first hand data gathered by the researcher himself
- Secondary data is data collected by someone else
Why phenolphthalein
As it has a pH range of 8.3 to 10.5, and the equivalence point is slightly basic, we used phenolphthalein
What are the steps to making a primary standard solution?
Step 1: calculate and weigh the correct quantity of the substance
Step 2: dissolve the solid
Step 3: transfer the standard solution to a volumetric flask
Step 4: add distilled water until required volume
Step 5: homogenise the solution - invert it
What are the steps to perform a titration?
- Fill up a burette with the titre
- Use a pipette to add the unknown solution to a conical flask
- Add an indicator to the conical flask - 2-3 drops
- Slowly add the titre to the unknown solution by turning the knob and constantly swirling
- Slow the adding of titre when the indicator goes slightly purple
- Stop adding titre when there is a permanent colour change.
How to calculate percentage uncertainty?
% uncertainty = uncertainty/measurement made on apparatus x 100
What are the common uncertainties on measuring apparatus?
What are the rules for using uncertainties?
- If adding or subtracting numbers with uncertainties, add or subtract the uncertainties together
- If you are multiplying or dividing two uncertain numbers, then the fractional uncertainty of the product or quotient is the sum of the fractional uncertainties of the two numbers
