PAG 2.1 determination of concentration of hydrochloric acid Flashcards
method part 1 making a standard 0.100 mol dm-3 aq NaHCO3 solution
1) use a weighing boat and accurately weigh 2.10 g of solid sodium hydrogen carbonate
2) transfer the solid to a clean, dry 100 cm3 beaker and rinse the weighing boat with distilled water
3) add enough distilled water to dissolve the solid and stir with a glass rod
4) transfer the solution to a clean 250 cm3 volumetric flask using a funnel and rinse the beaker, glass rod and funnel with distilled water into the volumetric flask
5) make up just below the mark with distilled water insert the stopper and slowly invert several times to mix throughly
6) make up the solution to the mark and insert stopper and invert several times to mix throughly
method part 2 titrating to find conc of HCl
1) transfer standard solution to a beaker
2) use a pipette and pipette filler to transfer 25.0 cm3 of solution to a 250 cm3 conical flask
3) add a few drops of methyl orange to the flask
4) using the funnel, fill the burette with HCl
5) titrate the sodium hydrogencarbonate with the HCl while swirling until the solution turns from yellow to orange. trial titration.
6) repeat until you have concordant results
7) take burette readings to 0.05 cm3
how do you calculate percentage uncertainty?
error/ measurement x 100
why are hydrated sodium carbonate and sodium hydroxide not appropriate bases for making up a standard solution?
substance must have an accurate molar mass for us to work out the moles. sodium hydroxide absorbs water from the air and sodium carbonate loses water of crystallisation giving it a variable molar mass
