Titration Objectives: Make up a standard sodium carbonate solution, whose concentration you know. Perform an acid/base titration to find the unknown concentration of HCl and NaOH. Acid Base

Step 1: Calibrate the balance

Titration Calibration of balance You follow the manufacturers instructions from the user manual provided with the balance.

Making a standard Na2CO3 solution Step 2: Making a standard Na2CO3 solution

Titration Weighing by difference Weigh ~1g of Na2CO3, add the powder to a beaker and dissolve in 100cm3 water. e.g. Mass of weighing boat + base Mass of empty weighing boat Mass of base used 13.35 12.41 0.94

Titration Standard solution Transfer solution to a volumetric flask and add more distilled water until the meniscus sits on the graduation line.

Titration Standard solution Transfer solution to a volumetric flask and add more distilled water until the meniscus sits on the graduation line.

Step 3: Calibrate the pipette

Titration Calibration of a pipette Measure out 25cm3 of water using the pipette and weigh the 25cm3 of water. Record the room temperature Look up the density of water at this temperature. Use the equation mass/density = volume to calculate the actual volume delivered. Ensure that the volume you calculate is within ± 0.06 cm3 of 25 cm3. If you look closely at your pipette, it tells you that the manufacturer has already calibrated the pipette and it should deliver 25cm3 ± 0.06 cm3 of liquid. If your calculated volume is outside this range then you may have done something wrong e.g. there is an issue with your volumetric technique. Mass of empty beaker (g)   Mass of beaker + 25cm3 water (g) Mass of 25cm3 water (g) Temperature (0C) Density of water at this temperature Actual volume delivered

Step 4: The titration

Titration Performing the titration You can calculate the concentration of base (you know the mass of base and volume of water used). But you do not know the concentration of acid… Determine the volume of acid needed to neutralise 25cm3 of base. From this volume you can determine the unknown concentration of the acid. Acid Base

Titration Performing the titration Transfer25cm3 of base to a conical flask using a pipette and pipette filler. Add indicator. Add acid from the burette until a colour change is seen. S E

Titration Performing the titration Transfer25cm3 of base to a conical flask using a pipette and pipette filler. Add indicator. Add acid from the burette until a colour change is seen. Methyl orange Phenolphthalein

Read the Meniscus 20.00 cm3

21.30cm3

15.45cm3

Titration Do a trial titration first. Concordant! Two values within 0.1 cm3 Stop your titration. Trial Run 1 Run 2 Run 3 Final burette reading / cm3 Initial burette reading / cm3 Titre / cm3 Mean titre to one decimal place 6.80 13.20 19.85 26.35 0.00 6.80 13.20 19.85 6.80 6.40 6.65 6.50 6.5 Do a trial titration first. Continue until you get two concordant results (not including the trial). Calculate the mean to one deimal place using the two closest titres.