Concentration of a Limewater Solution

assiduousness of a Lime piddle firmness of purposeTo determine the preoccupancy of a Limewater SolutionAimTo determine the preoccupation a 250 cm3 limewater solution, this contains approximately 1g dm-3 of calcium hydroxide. to a fault known is the concentration of HCL at 2.00mol dm-3.IntroductionA titration method result be used to head for the hills erupt the concentration of the limewaterBut in front the concentration of the limewater can be worked place, the correct concentration of HCL essential(prenominal) be worked out and an ideal index finger used in the titration method must be chosen.HCL Concentration The known concentration of limewater is 1g dm-3 and the concentration of the HCL is 2.00 mol dm-3. The concentration of HCL too high and must be reduced by dilution. index Indicators in titrations are used to determine the end elevation of the neutralisation of the reply of an analyte solution (unknown concentration) by the addition of a titrant solution (known concentration and intensiveness). The end-point is shown by the transmute in glossary of the indication present in the analyte solution.An ideal indicator shouldHave a sharp act upon change so that just 1 send packing of acid pass on causation the analyte solution to change glossiness instantly, rather than a gradual deform change from as more acid is added.A distinct colorise this makes it easier to spot the colour change, when the analyte has completely been neutralize.The colour change should happen at the equivalence point, which is the point that the number of groins of titrant solution is equal to number of moles of the analyte solution.The indicator Phenolphthalein has these ideal properties and will be sui tabulate for the titration. In this titration, the regent or titrant solution will be HCL and the analyte solution will be the limewater, the phenolphthalein indicator will be placed in the limewater Ca(OH)2(aq). In a base, phenolphthalein changes colour to pink and when in a neutral solution, it will become colourless. The reactionCa(OH)2(aq) + 2HCl(aq) CaCl2(aq) + 2H2O(l)Is primarily a base Ca(OH)2(aq) plus an acid 2HCl(aq) which produces water and a salt CaCl2(aq) (both together as a solution). Therefore in his titration, as HCL is added to Ca(OH)2(aq) the indicator should turn from pink to colourless upon the complete neutralization of Ca(OH)2(aq). provisionBefore the titration can begin, we must find the correct concentration of HCl worked out from the giving concentration of Ca(OH)2(aq). However the Ca(OH)2(aq) is giving ingrams dm-3 and HCL is giving in mol dm-3, thus cardinal of the concentration has to be commuteed to the said(prenominal) units as the other.Limewater Ca(OH)2(aq) converted from grams dm-3 to mol dm-3Ca(OH)2(aq) has a concentration of 1g dm-3, which way that 1 gram of Ca(OH)2(aq) is dissolved in 1 dm-3 of water or 1000cm-3. using the equation Moles = Mass/RMM we can convert the units. Moles = Mass/RMM Mass Ca(OH)2(aq) = 1 gram RMM Ca(OH)2(aq) = 40 + 2(16 + 1) = 74Moles = 1 / 74 = 0.0135 moldm-3 (3 sig)Concentration of HCLThe Limewater Ca(OH)2(aq) has now, the said(prenominal) units of concentration as HCL.Ca(OH)2(aq) + 2HCl(aq) CaCl2(aq) + 2H2O(l)This reaction shows that 2 moles of HCL are reacting with 1 moleLimewater Ca(OH)2(aq) . Therefore the concentration of HCL must be double that of Limewater Ca(OH)2(aq) at approx 0.0200 moldm-3, as it would be impractical to get it at exactly at 0.270 moldm-3. This means that the HCL must be boil downd by a factor of 100, once more this also impractical, so it will be twice by a factor of 10.Hazards and SafetyKey points on safety and hazards when performing the experiment.HazardsHCL is corrosive and toxic.Limewater Ca(OH) can have adverse affects with long-term exposure.SafetyEquipment must be washed before and after the experiment, to avoid every errors in equipment from chemical substance traces.Safety goggles and chemical resistant- clothing such as a lab coat must be worn at in all times around during the procedure due to high concentration of HCL.The work area must be kept safe and tidy, to avoid any practical hazardsMake sure that the burette tap is closed when fill it and use a funnel to avoid any spillages.The funnel must be removed from the burette after use to avoid errors in results from the regent (HCL) dripping into it from the funnel and would be a hazard. Method to dilute HCLEquipment and ChemicalsStandard flaskfulful (500cm3) pipette pumpGraduated pipette (50cm3)Beaker (500cm3)2.00 moldm-3 of HCL (50 cm3)Distilled water (900cm3)MethodUsing the gradatory pipette connected to the pipette pump, r distributively the 50cm3 of HCl and place into the measuring flask.. (Note the graduated pipette need to be washed after use).Then pour 450cm3 of distilled water in to the flask purport the stopper onto the stock flask, and shake the solution to mix it tho approximatelyly fetching care not to spill it.Pour the solution then from the standard flask into the beaker.Then using the graduated pipette connected to the pipette pump, obtain 50 cm3 of the solution and place in into the standard flask. stifle out the contents of the beakerThen pour 450cm3 of the distilled water into the standard flask a relieve step 3 to 4.Wash out the standard flask and graduated pipette.The 0.02 moldm-3 solution of HCl (500cm3) is now made.Method of TitrationFig.1Equipment and ChemicalsTest setoff Value (cm3) finale Value (cm3)Titration(cm3)1st (Rough)0.00second0.003rd0.00 fourth0.005th0.00Average0.00Burette stand.Burette (50cm3).Funnel.Graduated pipette (25cm3).Pipette pump.Conical flask (250cm3).Beaker containing the 250cm3 of the 0.002moldm-3 ofFig.2HCL from the dilution method.Beaker containing 250cm3 of the unknown limewater Ca(OH)2(aq) solution.White TilePhenolphthalein Indicator.A wasted table, as shown in Fig.1.MethodSet up the equipment as shown in the diagram to the right in Fig.2.Obtain an d transfer using the graduated pipette connected to the pipette pump up to the fill tie to the conical flask.add 5 drops of the phenolphthalein indicator (keep this number of drops the comparable for each of the titrations)Fill the burette with HCL up to 50cm3 and ensure the tap is closed.The First titration The prime(prenominal) titration is a rough titration, to show an indication at what rough volume of HCL the colour-change will be at. This anticipation of the rough volume allows the next titrations to be more accurate. Open the tap slowly and let the HCL drip into the conical flask at a consistent rate and at the same time swill the conical flask Continue this until there is a colour change from the limewater Ca(OH)2(aq) in the conical flask from pink to colourless, when this colour change happens, close the tap .Record on a table the volume of HCL at the point of the colour change in the End point column in the worn-out table. Wash out he conical flask and repeat steps 1 to 4 pass on titrationsOpen the tap slowly and let the HCL drip into the conical flask and higher rate than in the rough titration and swill the conical flask.Do this until the volume of HCL is 10 cm3 away from the rough end point volume.At this point reduce the rate of the drip, to at least 1 drop a second, and swill the conical flask more (be careful not to spill it), this will allow each drop to be neutralized and the limewater to show a colour change before the next one drips, ensuring more accurate results.Close the tap at the point of the colour change and record the end point volumes in the drawn table.Repeat steps 7 and 8 five times and records the results in the drawn table, ensure that at least 3 of the further titration end point prys are consistent within 0.2cm3 of each other.Wash out graduated pipette, beaker, burette, funnel and conical flask.ResultsThe results need to be processed. The titration column is digression between the start point value and the end point v alue The units of all the results need to be at 2 decimal places and the averages taken the start point value, the end point value and the titration value for excluding the rough titration results.TestStart Value (cm3)End Value (cm3)Titration(cm3)1st (Rough)0.002nd0.003rd0.004th0.005th0.00Average0.00AnalysisThe average titration (represented by X in the table below) will be in cm-3 and will need to be converted into dm3 to make its easier to use in calculations. To convert the value from cm3 to dm3, divide the value by 1000.Xcm3 / 1000 = Xdm3HClCa(OH)2Moles / moles??Volume / dm3X0.025Conc. moldm-30.02?Using the equation for a moles in a solutionMoles = Concentration x Volume The moles of HCL can now be worked out as the concentration is now known and the volume of HCL is