Procedural Error Titration Paper

Published: 2021-09-12 06:35:11
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The experiment practical I am going to do is all about the determination of the solubility of calcium hydroxide. This can be found by titrating the saturated solution against a solution of an acid whose concentration you know. The acid whose concentration we know is hydrochloric acid.The calcium hydroxide will be in limewater and this will have to be diluted before used. These two solutions will react together and a colour change will occur. Calcium hydroxide dissolves only slightly in water to form an alkali solution.IntroductionA titration is when two solutions react together. It is a technique to find the concentration of unknown solution. It is a method of quantitative analysis. One solution, which has a known concentration, is filled into a burette and the second solution is placed in a conical flask. A solution of known concentration or known morality is called a standard solution. In each titration the solution with the unknown concentration is filled in the burette is added in small measured quantities to the solution in the conical flask until just enough has been added for the reaction to be complete.The solution in the conical flask will have a fixed volume to start with until the solution in the burette is added to it and a visible colour change has occurred which means the two solutions have reacted together. Often an indicator is added to show when the reaction is finished to show the end point of a titration between an acid and an alkali an indicator can normally be used. The indicator can show when the base has been neutralised completely. Different indicators are suitable for different concentrations of strong and weak acids and alkali such as:* For a titration between a strong acid and a weak alkali = methyl orange is used as an indicator.* For a titration between a weak acid and strong alkali = phenolphthalein is used as an indicator.* For a titration between a strong acid and strong alkali = methyl orange or phenolphthalein is used.* For a titration between a weak acid and a weak alkali no indicator is suitable = a pH meter, conductivity meter or temperature probe has to be used.An analysis involving a titration is sometimes called a volumetric analysis. Titration’s have to be very accurate.A concentration is a measure of the amount of substance in a given volume of solution typically measured in mol dm.Calcium hydroxide (Ca(OH)In water calcium hydroxide form alkali solution, although they are not very soluble. Hydroxides can react with acids to form salts. A neutralising effect is used by farmers when they put lime- calcium hydroxide- on their field to neutralise soil acidity. This is done as if the soil is too acidic, most crops will not grow well.Hydrochloric acid (HCL)Hydrochloric acid is a strong acid. Hydrochloric acid is used to break our food into smaller molecules in our stomach. As it is a strong acid it has a much higher electrical conductivity then a weak acid, as more ions are present. It can react with metals, alkali, metal oxides, and metal carbonate and all of the reactions involve h ions. A 0.1 mol dm solution of strong acid such as hydrochloric acid has a pH value of 1.Method* Get all equipment ready to use, clean out all equipment with distilled water:- burette and burette stand- pipette and pipette filler- mini pipette’s- volumetric flask- conical flask- distilled water- hydrochloric acid- limewater- methyl orange indicator* Set up burette stand with burette.* Use a pipette filler and pipette to transfer 25cm of hydrochloric acid solution into a volumetric flask.* Once it has been transferred to the 250cm volumetric flask, add distilled water up to 250cm so that the hydrochloric acid is diluted. Then transfer this diluted solution via the funnel to fill up the burette to 50cm ready to use.* Then use pipette filler and pipette to transfer 25cm of limewater containing calcium hydroxide to a 250 conical flask.* Then using a mini pipette add 3 drops of methyl orange indicator to the conical flask containing the limewater.* Then place the conical flask with a glass tile underneath it to see visible colour change under the burette.* Then slowly add in small quantities or drop by drop from the burette the hydrochloric acid solution from the burette until the indicator shows a change to a permanent pink colour.* This is the end point of the titration.* Record your reading on the burette as a rough one, then repeat 3 times and record results in a table.How to dilute and why to dilute:The hydrochloric acid has to be diluted in order for it to react effectively with calcium hydroxide. This is due to the concentration and volume of hydrochloric acid being too much so has to be diluted to become less. This can be done by diluting it with distilled water in a volumetric flask as 25cm will be filled will HCL and the rest 225cm with distilled water up top the 250cm mark.Number of titration’s:First a rough titration will be done. The three more titrations will follow. These will be recorded in a table. The initial titration and average titration value will be calculated.Accuracy:When doing any titration you have to be very accurate in order to achieve the effective results. You must strictly follow out all instructions very carefully and measure all solutions out accurately. As if you make the hydrochloric acid too concentrated this can effect your titration results.Suitability:This is a very suitable and effective way to do and calculate a titration as is done this way all the time. It can show effective colour change.Risk assessment:Safety:Safety is very important when carrying out any practical experiment in the lab. Many general rules need to be followed in order to make sure we carry out our practical safelyGeneral rules:* Wear goggles at all time during the practical.* Wear lab coats to protect clothing.* If needed wear gloves.* Tie long hair back* Handle all glass equipment with care.Solutions:Calcium Hydroxide in lime waterCORROSIVE = causes burns. Irritating to eyes, skin and respiratory system so do not inhale.AcidIf:What to do:ProtectionCalcium HydroxideswallowedWash out mouth. Seek medical attention.DON’T BE SO STUPID!!!,, ,,Solution gets into eyesFlood the eye gently with water for 10 minutes. If needed seek medical attention.Be very careful when handling. Wear gloves.,, ,,If spilt on skin or clothesRemove contaminated clothing. If blistering or reddening occurs seek medical advice.Be very careful when changing. Wear gloves.,, ,,If spilt in laboratoryScoop up as much as you can into a bucket. Add water to contaminated area and add mineral absorbent.Stay well away from area where spilt. Wear eye protection and gloves.With water = the reaction with water is vigorous and generate heat.Hydrochloric AcidMay cause burns. The vapour is very irritating to the respiratory system.If:Protection:swallowedWash out mouth and take a glass of water.If vapour inhaledMove victim to fresh air to rest and seek medical attention if breathing is at all effected.If liquid gets into eyesFlood eyes with water for 10 minutes. Seek medical attention if needed.If liquid spilt on skin or clothes.Flood water to effective area. Remove contaminated clothing. If blistering occurs seek medical attention.IndicatorNot really as harmful as other solutions but if any of the above happen take the same protection advice as above.Less harmful when put into diluted solution.Indicator going to use is methyl orange.Equipment ListAll the equipment that will be needed to carry out this practical experiment.EquipmentWhat used for/choice?buretteTo dilute calcium hydroxide and fill with. Accurate to used and can let solution drip bit by bit.Burette holder with funnelTo hold burette securely and funnel to pour solution through.Pipette with pipette fillerTo accurately measure out 25cm of solution needed and transfer using pipette holder to volumetric flask.Mini pipette (a few)To transfer solutions (3 drops of indication – methyl orange) to where needed. Accurate and easy to use. Use a different pipette for each different solution.Conical flaskTo place under burette containing hydrochloric acid. Clear to easily see change of colour.Volumetric flaskTo dilute limewater in up to the mark.Indicator- methyl orangeTo add to hydrochloric acid. To show end point of titration.Distilled waterTo wash out equipment after every titration and to dilute limewater.Limewater containing calcium hydroxideAlkali solution in burette testing for it’s solubility and to find it’s concentration.Hydrochloric AcidTo place in conical flask and titrate against lime water containing calcium hydroxide.ANALYSISING EVIDENCE AND DRAWING CONCLUSION:RESULTS:titrationrough123Final burette reading19.0cm19.6cm20.0cm20.5 cmInitial burette reading0000titre19202021Average titration = 20+20+21=6161 by 3 = 20.3Calculating of diluted acidHydrochloric acid has to be diluted in order for it to react effectively with limewater.25cm = o.3 mol dmIt is diluted to 250 so then the concentration of the diluted hydrochloric acid becomes 0.03 mol dmCalculate the concentration of limewater solution:It takes 25cm of 0.03 of hydrochloric acid to nentralise 35 of calcium hydroxide.Step1Ca (OH) + 2HCL Cacl + 2H OShow how 1 mole of Ca(OH) reacts with 2 moles of hydrochloric acid.Step 2Find out how many moles of hydrochloric acid were used.We use 25cm of 0.03 mol dm of HCL.In 1cm of the solution we would have 0.031000 x 30 moles of HCLMOLES OF HCLNumber of moles in a solution = concentration x volume of solution in cm1000= 0.3 x 25cm1000 = 7.5 for 1 moleIn the balanced equation there is 4 moles of HCL which equals 7.5 x 4 = 30 molesstep 33025 x 30 moles = 0.36The concentration of calcium hydroxide is 0.36 mol dmEVALUATING EVIDENCE AND PROCESS ASSESMENTRELIABILTYOn general terms the experiment is reasonably reliable but in any titration there are errors or uncertainties related to the precision of the equipment used.The precision errors are as follows:- volumetric flaskWhen a 25o volumetric flask is filled correctly the bottom of the menicus rests on the calibration. The error is o.2 cm 0r 0.08%.Burette:One drop from the burette has a volume of approximately 0.05cm. an error in one drop of 50cm = 0.4%PipetteWhen a 25cm pipette is used correctly it is allowed ti drain and retain the last drop. The error is 0.06cm or 0.24%.Calculating the percentage errorPercentage error = error x 100ReadingVolumetric flask= 0.2 x 100250 =0.08Burette= 0.4 x 10050 = 0.8Pipette= o.o6 x 10025 = 0.24Procedural error can arise if your practical technique is not good. A good technique will involve:Method can be improved by:* the solution in the volumetric flask needs thorough mixing* all equipment should be washed out using distilled water* the end point of the titration can only be determined accurately if the solution from the burette is added drip by drop with swirling as the end point is reached.* When an indicator is used in a titration only the minimum number of drops is added each time.There was not really any anomalous result as all the 3 titration’s done has very close and similar readingsThe titration was done 3 times to improve the reading of the experiment.Any additional titration’s done after 3 times were not really necessary to ensure that the results were accurate.The overall accuracy and reliability of the evidence that the experiment supplied is reasonably accurate as the 2 solution did react together well and a noticeable colour change from a pale orange to a permanent pink was visible.Due to the percentage error in the experiment technique is could have resulted in maybe the readings being slightly lower then they really should have been.CourseworkSolubility of calcium hydroxideBy Sabina fareedReferencechemical ideas bookChemistry for you by lawrie ryanChemical ideas work sheets

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