Experiment determining concentrations of unknown substances. This quantitive analytical

Experiment 1: Determination of the Quantity of Aspirin in Powdered Tablets using an Acid-Base Titration AbstractThe percentage of Aspirin in the powdered tablets were determined by an acid-base titration experiment. This type of volumetric analysis consisted of a standardised solution of sodium hydroxide which was used to titrate the powdered Aspirin tablets. A physical observable colour change from colourless to pink is used to distinguish the end point from the phenolphthalein indicator. Thus, demonstrating a neutralisation reaction is occurred. A value of 0.10 mol/dm-3 concentration of NaOH in average is calculated with also an average percentage purity of Aspirin in powdered tablets of 88.5% being determined.Aim- To determine the quantity of aspirin (acetylsalicylic acid) in powdered tablets by titrating with standardised solution of sodium hydroxide using a burette and phenolphthalein as an indicator. Introduction -The laboratory method used in the experiment is Acid-base titration. It is a type of volumetric analysis which involves determining concentrations of unknown substances. This quantitive analytical method is when the titrant is added to a known quantity of analyte. The titrant (which is a known standard concentration of solution) are made of primary standards.Some of the properties to classify primary standards are:1)low reactivity2)high level of purity3)non-toxic4)readily soluble under the conditions of use5)not likely to absorb moisture from the air 6)not react with oxygen or carbon dioxide7) have high relative molecular mass to avoid significant weighing errorsThe sodium hydroxide is water soluble and reacts with carbon dioxide from the atmosphere therefore cannot be used as a primary standard. The primary standard used in the experiment is Potassium Hydrogen phthalate which is an organic acid that is a solid and acts as a substance which is used to standardise against the strong base. An indicator Phenolphthalein is used to determine the end point of the titration where a colour change from colourless to a light trace of pink should be observed. Asprin is also known as 2 -acetoxybenzoic acid, is often used to treat pain, reduce fever, treat or prevent heart attacks, strokes, and chest pain.Apparatus• 50cm3 burette• 50cm3 measuring cylinder• Clamp stand• 250ml conical flask X3• A Funnel• A pestle and Mortar• A pipette• A 4d.p. and 2.d.p top pan balance• Hot plate • A White tile• weighing boat x 6• Phenolphthalein indicator placed in the fume cardboard• Sodium hydroxide solution (NaOH)• Distilled water• Aspirin tablets X 2 the value determined or a systematic error of misreading the burette (not observing from bottom of the meniscus.) Establishing two samples of A and C allows an average concordant titre value to be calculated producing accurate, reproducible results.On the other hand, in experiment two the percentagecalculated above for sample A and sample B were within 10.68% range. However, Sample A and C of aspirin arechosen instead as in comparison the value calculated is closer to the 1% range formulating to 7.61%. The values are then incorporated when finding out the averages.From the gathered results, it can be deduced that PHP required a larger volume of 23.40 cm3 to neutralise with the NaOH compared to the aspirin only requiring 17.70 cm3. This could perhaps be due to the fact Aspirin powder had to be all dissolved with the use of a hot plate ,increasing in temperature. Hence, less volume required to neutralise with the sodium hydroxide.  The percentage purity of aspirin worked out to be 85.5% and not fully 100% due to the fact that commercial drugs do not only contain aspirin as the active ingredient but also contain (in this case) 14.5% excipients which is inert. An example are as fillers which interfere with the absorption of tetracycline from the gastrointestinal tract. ConclusionIt can be concluded that the aim to find the percentage of aspirin in powdered tablets by titrating with a standardised sodium hydroxide solution resulted to be 85.5% pure. To have figured the % purity beforehand in the first experiment samples A and C worked out as 2.53% closest value within 1% range amongst Sample B and C on the other hand equating to 11.24%. The average concentration of sodium hydroxide solution formulated to 0.10mol dm-3.A 1:1 ratio of sodium hydroxide and potassium hydrogen phthalate means 1 MOLE OF NaOH  1 MOLE OF C8H5KO4 According to the results gathered as the weight of PHPincreases the volume of sodium hydroxide used also increases which demonstrates a positive correlation.    Then the second part of the experiment was used to determine the percentage of Aspirin. Samples B and C were used as they had similar V/W values and similar weight of powdered tablet values. Sample A was not used as it was an anomaly in the practical.This resulted in the percentage purity decreasing and the data being less reliable. The average percentage purity of the aspirin tablet worked out to be 88.5%.    EvaluationEven though there were results attained for the percentage purity of aspirin concluding to 88.5% there are few limitations which could be improved to eliminate minor errors affecting the accuracy, consistency of the results for next time.The factors that might be causing errors in titration findings:1) determination of end point = It is when neutralisation occurs and a observable colour change exists such as in this case colourless —> light pink. It is hard to identify when phenolphthalein turns a faint pink and precisely adding a drop of NaOH each time to prevent making the substance too acidic. However, a white tile was handed to make the physical observation of colour change easier to detect hence gathering better, accurate results. You could also reduce the rate flow from burette unto conical flask.2) Utilising the exact conical flasks by rinsing before next titration with tap water. This could have affected our results with contaminants before testing for a new trial. Therefore, to try minimise errors you could use distilled water instead between titrations as it does not add any moles of reagents leading to less systematic error.3) systematic error whilst measuring the sample boats on the top balance. In the first experiment the weights were recorded to 4 decimal places increasing the accuracy of the result whereas in experiment due to limited availability and a short time frame the records were recorded to two decimal places. 4) Collectively, from both experiments the burette reading seemed to have the highest percentage error in comparison to the other apparatus used displaying accurate readings due to low percentage errors in general.5) Misreading the volume on burettes = A common error is reading the volume at an angle resulting calculated errors therefore need to make sure you are facing horizontal and reading the bottom of the meniscus at eye level to avoid such miscalculations6) incorrectly handling the equipment =  e.g. using a beaker instead of a conical flask to swirl hence spilling all the solution out therefore inaccurate results. Another example is introducing air bubbles when filling the burette with NaOH which will affect the initial readings and final reading.7) Other errors= some examples are equipment errors where the burette has leaks affecting the results majorly or the balance does not weigh to four decimal places reducing the accuracy and precision of the results.  8) Only three titre readings were calculated= Could repeat the experiment a couple more times to gather more accurate, reproducible, consistent set off results if more time permits where you could have enough values to demonstrate a graph.                             coSHH Risk Assessment Form  Substances (ALL substances to be included)Chemical Hazards and Risk(High, Medium, or Low)(R-Risk Phrases)Measures to control Risk(S-Safety Phrases)AspirinR-22 Harmful if swallowed.R-36/37/38 Irritating to eyes, respiratory system and skin.Keep locked up and out of the reach of children.S-26 In case of contact with eyes, rinse immediately with plenty of water and seekmedical advice.S-46 If swallowed seek medical advice immediately and show this container label.Sodium HydroxideR11: Highly flammableR45: May cause cancer (Category 2)R68: Possible risk of irreversible effectsmay cause skin irritationmay be harmful is swallowedAvoid breathing vapours In case of contact with eyes, rinse immediately with plenty of water and seek medical adviceWear suitable protective clothing, gloves and eyewearIn case of accident or if you feel unwell, seek medical advice immediately Keep away from sources of ignition – No smokingWash hands throughly if come into contact  Phenolphthalein R11: Highly flammableR45: May cause cancer (Category 2)R68: Possible risk of irreversible effectsharmful if swallowedlow hazardAvoid exposure – obtain special instructions before useKeep container in a well-ventilated place.Use glovesmake sure no sparks exposedPotassium Hydrogen PhthalateMay be harmful if swallowed.May cause irritation to skin.Avoid contact with eyes and skin. Do not breathe dust.Avoid contact with skin and eyes.Wash hands throughly if come into contact.Distilled waterN/AN/A Spillage and disposal methods:Expected to clean up any spillages using absorbent paper towels and to dispose after.  Inform a member of staff or any helpful technician’s if any major spillages/ accidents occur.  First Aid/ Emergency Action:In case if skin;s been in contact with substances in the experiment wash affected area with plenty of water rapidly. e.g. if contact with eyes ensure to was thoroughly. Any cuts from the glass of the burette or severe burns from the hot plate. Need to ensure focused and handle the equipment with care.