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Introduction

Analysing Soft Drinks Introduction Soft drinks contain acid and sugar. These substances contribute to tooth decay and therefore are a cause for concern. In the first part of the investigation we'll measure the acidity in blackcurrant juice. Labels on black currant juice drinks usually state citric acid is present in the drink, but it doesn't give you the amount of how much it contains. Dilutable soft drinks contain between 0.15 - 2.5% of citric acid research by The British Drinks Association and therefore the second part of the experiment would be to determine the concentrations of blackcurrant juice in the diluted samples. Investigation 1: Measure the acidity of the blackcurrant juice drink In order to measure the acidity of the blackcurrant juice, I'll titrate black current juice with 0.1mol of sodium hydroxide and use a pH meter to measure its pH. Technique The technique of this experiment is titration. It is a method of chemical analysis, which is used to determine the volume of concentration needed to react with an unknown solution. Equipments needed for titration: * Burette * Conical Flask * Clamp Technique of using titration method: The measurement on the burette (cm3) tells you how much solution you have poured into the substance. ...read more.

Middle

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: No mol NaOH = No. mol citric acid /3 = 0.001 Conc. NaOH= No. of mol Citric acid x 1000/Vol = 0.001 x 1000/10 =0.1 Formula: C6H8O7+3NaO4 --> C6H8O7Na3+3H2O 3:1 NaOH C6H8O7 Volume (cm3) ...read more.

Conclusion

21 27 27 35 42 47 55 71 82 100 Experiment 2 19 21 26 27 34 42 47 54 69 78 100 Experiment 3 20 22 26 26 36 41 48 58 72 83 100 Average 19 21.3 26.3 26.7 35 41.7 47.3 55.7 70.7 81 100 Concentration 1 2 3 Experiment 1 36% 32% 34% Experiment 2 36% 30% 30% Experiment 3 36% 33% 32% Average 36% 31.7% 32% Evaluation: Through out the experiment, I've completed most of the tasks. However, 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 ...read more.

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