If you dissolved a segment of weak acid in water, only a small amount of weak acid would dissolve into Hydrogen+ ions and negative- ions and the rest of the weak acid would remain un-dissolved in the solution. Experiment Begin: 1. Measure out 25 ml of black current juice by using a pipette 2. Pour it into a 10 cm3 beaker 3. Fill 50 cm3 burette with sodium hydroxide (make sure the tap is tight before pouring anything into it and use a funnel to avoid spillage) 4. Add 1. 0cm3 of sodium hydroxide into the solution and shake it 5. Measure the pH and take a reading 6. Continue procedure 4 & 5 7. Until the pH gradually changes slowly add 0. 1cm3.
8. Take a reading Equipments needed Equipment Usage Goggles To protect the eyes from sodium hydroxide Gloves To protect the hands from sodium hydroxide Beaker (100 cm3) Container Burette (50cm3) Control measure Pipette (25 cm3) Measure out 25 cm3 of black current juice Black current juice Fixed volume of water Funnel Prevent any spillages Clamp Hold the burette tight in place pH meter Measure the pH in black current juice Average Results Analysis 1dm3 = 1000cm3 NaOH Calculation 1. No. moles (Acid) = Concentration (NaOH) x Volume of titre required/ 1000 2. Concentration of acid = moles x 1000/ volume (dm-3) Concentration of NaOH to use:
Colourimetry The technique /science The techniques for this experiment are Colour matching, Colourimetry and Calibration graph. Colour matching Colour matching is a method relies on a person’s eyes to determine the intensity/ the wavelength of light of a coloured solution with the nearest colour from a set of coloured standard solution. This method however is not accurate as human errors can be made because it relies on the judgment of the person’s eyes. Colorimetry: Colorimetry involves using light to work out the concentration of an unknown coloured solution. Colourimetry uses a device called the colourimeter.
It is more accurate than Colorimetry as it is measured by machinery. The colour is measured using a spectrophotometer in the machine. Colourimeter obtains 3 wideband of readings in within the visible spectrum boundary to obtain an estimate of a colour sample. The reading determines how concentrated the solution is. The greater the concentration, the lower the reading. The lower the concentration, the greater the reading. Calibration graph: By plotting a Calibration graph using the Colourimetry results, we can easily compare the data and determine the absorbance of both known and unknown concentration.
Calibration curve: Calibration curve is a method to identify the concentration of a substance in an unknown sample solution. This is done by comparing the unknown to a set of standard samples of known concentration. Colours: Different colours have different wavelength and frequency. Colours are refractions of light. By using a prism, we can split the colours from the light into seven different colours to create a colour spectrum. The colourimeter uses the similar method to find out the concentration of a solution.
These are the following equipments needed to begin colourimetry experiment: Colourimeter Test tubes Samples of different concentrated solutions The experiment begins: 1. Prepare 2 test tube racks 2. Place 11 test tube into the racks 3. Label them from 0% to 100% concentration (up in tens) 4. Follow the table below and measure out the amount of solution and substance for each test tube Concentration% .Experiment 1However, I think my experiment it’s not as good as I expected to be. The results I’ve got for my first experiment have some slight anomalous values, which will impact on my final results. These are the possible reasons: 1.
Volume control: extra solution (NaOH) can be accidentally added into the substance during the titration. A small amount of extra solution can have a big impact on the pH 2. Room temperature: Room temperature rise can speed up the collision between particles and therefore increase the chances of reactions between citric acid and sodium hydroxide 3. Time limit: If we have given more time to complete our experiments more repeated of experiments can be done. This will increase the accuracy for my final result and more chance of avoiding biases 4. Equipments: equipments can be improve therefore the results would be xmore accurate.