Determining the concentration of Vinegar
1. Place an electronic scale on a level surface and put a 50g weight on the scale and calibrate 2. Measure the weight of conical flask 3.
Accurately measure a mass of KH(C8H4O4) near to 5g, placing it in a 250ml conical flask 4. Record the reading from the scale, subtract the weight of conical flask measured in step 2 5. Dissolve KH(C8H4O4) in a conical flask with minimum volume of distilled water 6. Transfer the solution from the conical flask into Standard Solution 1. Use an electronic balance equal to three decimal places to accurately weigh out in a 250ml beaker a mass of KH(C8H4O4) approximately equal to 5. 005g. Record this mass. 2. Dissolve the KH(C8H4O4) in a minimum volume of distilled water in a beaker.
3. After washing the 250ml volumetric flask with distilled water, rinse with more distilled water. 4. Transfer the solution from the beaker to a volumetric flask using a funnel. 5. Wash all traces of the solution from the beaker and funnel by rinsing the beaker and funnel thoroughly with distilled water from a wash bottle into the volumetric flask. 6. Swirl the solution in the volumetric flask but do not invert. 7. Add more distilled water until the bottom of the meniscus is aligned with the calibration mark.
To ensure accuracy use a teat pipette to add the final few millilitres of distilled water. 8. Stopper the flask and invert several times to mix the contents and thereby ensure the solution is of uniform concentration throughout. Standardisation of Sodium Hydroxide 1. Prepare the burette and fill with the sodium hydroxide solution to 50ml. 2. Pipette the KH(C8H4O4) solution into a conical flask. Use three drops of phenolphthalein as the indicator. 3. Titrate carefully until a colour change from colourless to pink is observed. 4. Perform a rough titration first, then repeat until 3 concordant titres are obtained.