RP1 - MAKING A STANDARD SOLUTION + TITRATIONS

• using pipette and pipette filler measure 25 cm^3 of alkali into the conical flask • add a few (5-10) drops of indicator (could be methyl orange/phenolphthalein) to the flask • place a white tile under the conical flask • use a funnel to fill burette with acid of known conc. remove funnel and record initial volume • add acid from the burette slowly and swirl the flask constantly • add acid drop wise towards the end • as soon as there is a colour change stop adding acid • calculate volume of acid added • repeat titration and calculate mean

so no additional drops fall into the burette whilst you’re doing the titration as this would affect the volume

• pipette and burette should be rinsed with the solution you will be using in each one • this is because rinsing them with water would affect the conc. of the solutions

so it doesn’t react with the solution in the flask which would affect the end point

results within 0.1 of each other

only use concordant results

• measure mass of Na2CO3 in a weighing boat using a mass balance • pour Na2CO3 into beaker • re-weigh empty weighing boat and subtract its mass from the mass of the weighing boat with NaCO3 and record this value • dissolve Na2CO3 in ~100cm^3 of distilled water and pour into volumetric flask • rinse beaker with distilled water and pour rinses into volumetric flask (repeat at least 3 times) • use pipette to add distilled water until meniscus reaches 250cm^3 • invert flask many times