CPAC 02 Flashcards
Outline the method to make a standard solution of sulfamic acid
- add between 2.3 and 2.4g of sulfamic acid to weighing boat and weigh
- transfer as much of the acid as possible of to clean beaker and reweigh weighing boat
- add 100cm3 of deionised water to beaker and stir until all sulfamic acid has dissolved
- remove stirring rod and wash any remaining contents on stirring rod with wash bottle
- place funnel on volumetric flask and pour solution in
- rinse beaker several times with wash bottle and transfer rinsings to flask
- add deionised water to the flask and make it up to the 250cm3 graduation mark exactly- measuring at bottom of meniscus
- stopper flask and invert it several times to make uniform solution
What is the weighing by difference technique?
- method to weigh substances accurately
- mass of substance= mass of weighing dish and substance- mass of weighing dish after substance has been transferred
What is the procedure for the titration?
- rinse conical flask with deionised water and place on white tile
- using pipette filler, rinse pipette with deionised water and then with sodium hydroxide solution
- use pipette to transfer 25cm3 of sodium hydroxide solution to the conical flask
- add around 3 drops of methyl indicator
- rinse burette with deionised water and then some sulfamic acid solution
- fill burette with sulfamic acid solution and set up in stand above conical flask
- record burette reading
- add sulfamic acid to conical flask until it just changes colour and record burette reading
- empty and rinse conical flask with deionised water and repeat titration until concordant results obtained
What are concordant results?
within 0.1cm3 of each other
What should the burette readings be measured to?
0.05cm3
Why should the pipette be rinsed with sodium hydroxide solution after washing it with water?
water left in the pipette will dilute the sodium hydroxide used so changing the moles
Why is it not necessary to dry out the conical flask after washing it between trials?
the water will not change the number of moles of sodium hydroxide as its volume is measured before it is put in the flask
What colour change takes place in this titration for methyl orange?
methyl orange goes from yellow to red
What other indicator could be used?
phenolphthalein goes from pink to colourless
What are the hazards with sulfamic acid?
can be toxic if ingested
