Titration Report

A titration is a method where a solution of known concentration is used to determine the concentration of an unknown solution. Typically, the known solution is added from a burette to a known amount of the unknown solution until the reaction is complete. Knowing the volume of the known solution added allows the determination of the concentration of the unknown. Often, an indicator is used to usually signal the end of the reaction, the endpoint. Concentration is the abundance of a constituent divided by the total volume of a mixture. Molarity is a concentration unit, defined to be the number of moles of solute divided by the number of litres of solution.
An acid has a pH of less than 7 and can range in colour from a weak acid of light green through to dark red for a strong acid according to the pH scale. Acids generally taste sour and react strongly with metals. Strong acids can be dangerous and burn your skin and give sharp stinging pain in a cut or wound. Weaker acids such as those found in vinegar are useful in cleaning and also neutralising a wasp or jellyfish sting.
In the neutralisation process acids become less acidic when mixed with bases. A neutralisation reaction is a chemical reaction in which the acidic and basic affinities of the reactants are cancelled out.
Aim
The aim of this practical is to identify which of the four unknown substances is the acid and what substances are the bases. After finding the acid and bases you will then need to find out how much acid is needed to neutralise each base to then calculate the concentration.
Hypothesis
By conducting the universal indicator test it will allow you to determine which of the four chemicals are the acid and bases. Different colours will let you know if it is a base or an acid. The acid will just stay a clear colour colour and the bases will turn a pink or purple colour.
Part A: An acid can be determined by Universal Indicator. If it changes to a reddish colour it means that the chemical is an acid and if it turns a blue or purple it is a base.
Part B: It is predicted that once the bases are neutralised they will turn green using the Universal Indicator.
Variables
An Independent variable is a factor that is changed in an experiment. A Dependent variable is a factor that can’t be changed such as the weather. Independent | Dependent | Over filling the burette | Amount of Hydrochloric acid | The concentration of the chemical | | How many drops of phenolphthalein indicator is used | |

Safety * Make sure that everyone in your group is wearing their safety glasses so if anything spits up nobody’s eyes will be harmed. * Be careful not to spill any acid on your skin or on the bench. * Make sure that there are no obstacles around the bench. * Clean up any spills. * If you spill any acid on your hands make sure you wash it off straight with water. * If glass ware is broken inform the teacher as soon as it happens. * Make sure to wear enclosed shoes just in case the acid solution spills onto your feet.
Materials
* Safety glasses * 50mL burette * Retort stand, boss head and clamp * 20mL pipette and pipette bulb * 100mL conical flask x 2 * Dropping bottle of phenolphthalein indicator * Small funnel * Hydrochloric acid solution (1.0M) * Sodium hydroxide with three unknown concentrations * Universal indicator in a dropping solution * Test tube rack with 6 test tubes. * White Tile
Method
Part A: Acid or base 1. Organise your equipment ensuring it is clean 2. Pour approximately 1-2 cm of each solution into the test tubes provided. Make sure you don’t mix the solutions together, pour them into separate test tubes. 3. Add a few drops of Phenolphthalein into each test tube (Note: make sure you know which test tube contains which applicable solution – you may wish to number them) 4. The solutions should change, if it is an acid it should stay clear and if it is a base it should turn a pink colour. 5. Record your results in the table to show which solution has acidic

Part B: Titration 1. Organise your equipment ensuring it is clean. 2. Take your pipette and your pipette filler, use your two thumbs on the end of each, push them together until your thumbs meet. Make sure it doesn’t wobble too much, if it does then push the pipette and pipette filler closer together. 3. Using your pipette, draw up 20mL of the base from either a bottle or a beaker and place into the conical flask (when using the pipette make sure there are no air bubbles as this could affect the correctness of the required amount) 4. Place a few drops of the universal indicator to the base which will trigger the pinkness 5. Pour at least 20mL of the provided acid into the burette using a funnel. 6. Record the measurement of the starting point that the acid has reached. 7. Turn the burette tap marginally so that the liquid is slowly releasing into the conical flask while at the same time swirling the flask to blend the solutions together. 8. Watch closely for the point at which the chemical neutralization reactions occur and are completed – this is when the pink colour turns clear. Make sure to turn off the burette earlier to avoid missing the end point. 9. Record the finishing point measurement where the acid has stopped. 10. To calculate the answer, subtract the recorded starting point from the finishing point. 11. Repeat this method twice over with the same base. 12. Repeat steps 2-9 with the remaining bases provided.

Results A (pH9) | B (pH9) | C (pH3) | D (pH9) | Base | Base | Acid | Base |
Experiment 1: Solution | A | B | C | D | Starting Point | 30mL | 29mL | N/A | 39mL | Finishing Point | 47mL | 35mL | N/A | 50mL | Difference | 17mL | 7mL | N/A | 11mL |
Experiment 2: Solution | A | B | C | D | Starting Point | 18.3mL | 20mL | N/A | 19mL | Finishing Point | 36.5mL | 27mL | N/A | 26.4mL | Difference | 18.2mL | 7mL | N/A | 7.4mL |

Experiment 3: Solution | A | B | C | D | Starting Point | 27mL | 25mL | N/A | 18mL | Finishing Point | 39.5mL | 28.5mL | N/A | 27.5mL | Difference | 12.5mL | 3.5mL | N/A | 9.5mL |

Average | 15.9mL | 5.83mL | N/A | 9.3mL |

Observations
Part A * When phenolphthalein was placed into each of the test tubes Solutions A, B and D went a bright hot pink in colour and solution C did not change colour but instead stayed clear. This showed that Solution C is the acid. * When the universal indicator was placed into each of the solutions the three bases all went a dark purple while the acid went red. This showed the pH of each of the solutions which was a pH of 9 for each of the bases and a pH of 3 for the acid.
Part B
Solutions A, B, D (Bases) * Phenolphthalein was added to the Solutions and they turned a bright hot pink just as it did in Part A. When Solution C – the acid – was released slowly from the burette the Solutions slowly started to go clear as they neutralised. The pink slowly faded from the solutions.
Solution C (Acid) * When the Phenolphthalein was added no change occurred to the chemical just as in Part A. When Solution C was released slowly from the burette no change occurred as the same solution was added
Calculations
| A | B | C | D | Acid | C1 x V1 1.0 x 15.9mL15.920 | C1 x V1 1.0 x 5.83mL5.8320 | N/A | C1 x V1 1.0 x 9.3mL9.320 | Base | C 2 + V2 C2 + 20mL | C 2 + V2 C2 + 20mL | N/A | C 2 + V2 C2 + 20mL | Answer | C2 = 0.795 molar | C2 = 0.291 molar | N/A | C2 = 0.465 molar |

Discussion
According to the results table, substances A, B, and D were clear liquids until the indicator was added and it changed to a purple coloured liquid. According to the pH scale these chemicals are bases. Substance D started as a clear liquid, and once the universal indicator was added it changed to a red liquid indicating it is an acid. No problems came across while conducting this chemical test.
After completing the titration, we noticed that all the bases used had different concentration levels and varied in results. The base with the highest concentration level was Base A, and the base with the lowest concentration level was Base B. When we added the acid to base A, it took a longer time for the substances to turn clear, the reason for this was because we had to use more acid as it had a higher concentration level. Base B had the lowest concentration level as it only took a short amount of time for the acid to turn it clear and used a low amount of acid. Therefore, leaving Base D to be in the middle as it was in between for time taken and amount of acid used. In terms of expecting this to happen, I did expect it as I knew if the base had a higher concentration level then it would take a longer time to neutralise, and if it had a lower concentration level then it would take a shorter amount of time to neutralise. Once we had finished the titration we relied on our results as we didn’t get to compare them with any other groups. Each time we filled the burette we poured some of the Hydrochloric acid into it through a funnel, we then recorded the measurements. The variable that stayed the same was the amount of base used. Every time we performed a titration we used 20mL of a base in each conical flask. The variables that we were unable to control were the change of colour. When enough acid was added to the base to neutralise it, the base turned from a pink colour to a clear, although it didn’t make a difference in the results as all of the bases turned clear. I believe that our investigation was a fair test because we performed the titration three times. The reason we performed it three times was because we could work out an average so that we knew the results were close to being accurate and meant that it would be a fair test.
The titration is performed by slowly dripping the basic solution from the burette into a beaker or flask containing a measured amount of the acidic solution and several drops of a chemical indicator. An indicator is a chemical that will respond to changes in its environment. In the case of an acid-base titration, the experimenter will most often use an indicator that will change color when the endpoint of the titration is reached. In an acid-base titration the experimenter is trying to determine the equivalence point of the reaction, which is the point when the amount of base added was exactly the correct amount to have the moles of base completely react with the moles of acid. If the experimenter chooses the correct indicator, the endpoint of the reaction will be as close as possible to the actual equivalence point.
Conclusion
The aim of this experiment was to identify which of the four unknown substances was the acid and which substances were the bases using the universal indicator. The results meet the hypothesis because with the Universal Indicator test, it determined the acid to be a red colour and the bases to be a purple colour. This is concluded that this test is a fair test with only the chemical being changed.
Improvements can be made to the method by measuring the number of drops of each solution added to each test tubes ensuring that the same number of drops is added to each test tube. Also if a pH scale was provided the pH level could have been recorded to determine the strength of the acid and bases.