# Determining the Concentration of a Limewater Solution

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Introduction

Determining the Concentration of a Limewater Solution Introduction Previous to conducting my experiment, research was carried out and the results of it adapted to aid me in solving the problem set. In the Advanced Chemistry Student's Book by Nuffield, on page 86, I found a similar experiment to mine with a description of implementation, which aided me in the fact that I discovered the temperature of my solution did not need to be taken. This was because the solution of calcium hydroxide they used was saturated, and therefore they measured the temperature of the saturated solution along with its solubility, due to the fact that the solubility of saturated substances varies with temperature. This procedure will not be necessary in my particular experiment as the solution I will use will be far from saturated. Safety measures were observed and taken into account by looking at the hazard card for calcium hydroxide. I found the substance to have minimal hazards, especially when diluted in a non-saturated solution, and thus concluded the only precaution needed to be taken was to wear eye protection during handling of the solution. ...read more.

Middle

+ (2 x 1.0) = 74.1 Therefore number of moles present = 1/74.1 = 0.013495 mol To dilute the 2.0mol dm-3 solution to 0.01mol dm-3 deionised water will be used to eliminate the possibility of impurities being present within the solution, the probability of this increasing would have been increased if tap water had been used. An entire decimetre of solution was not required for this investigation, therefore only 500cm3 was made up. The dilution was carried out accordingly; 10.00cm3: 1000.00cm3 = 0.02mol dm-3. Therefore 5.00cm3: 1000.00cm3 = 0.01mol dm-3. Therefore 2.50cm3: 500.00cm3 = 0.01mol dm-3. For this dilution a graduated pipette will be used to accurately measure 2.50cm3 of acid, following this the deionised water will be added until the bottom of the meniscus rests on the 500cm3 mark. The lid will then be firmly placed on the volumetric flask and the solution will be shaken well, at least 20 shakes to ensure that the concentration of acid is equally distributed throughout the solution. Prior to pouring the acid into the burette a small funnel will be placed into the top to aid accurate pouring, ensuring none of the solution is wasted. ...read more.

Conclusion

24.20 48.50 24.25 Initial burette reading (cm3) 0.00 24.20 0.00 Titre (cm3) 24.20 24.30 24.25 Average titre = 24.25cm3 ((24.20 + 24.20 + 24.25) / 3) Analysis The balanced equation: 2HCl (aq) + Ca (OH) 2(aq) --> CaCl2 (aq) + 2H2O (l) Therefore to find the concentration of the limewater I obtained the average titre, and then worked out the number of moles of hydrochloric acid that were used using the equation: No. of moles (mol) = Concentration (mol dm-3) x Volume (dm3 Therefore 0.01 x 0.02425 = 0.0002425mol. To work out the number of moles of limewater used, the ratio of limewater to hydrochloric acid is 1:2, therefore 0.0002425/2 = 0.00012125. To work out the concentration of the limewater this figure is divided by the volume of limewater used using the equation: Concentration (mol dm-3) = No. of moles (mol) / Volume (dm3). Therefore 0.00012125/0.025 = 0.00485. To work out the concentration in g dm-3 we must first obtain the molar mass of calcium hydroxide which is 74.1. Using the equation: Mass (g) = Number of moles (mol) x Molar mass Therefore 0.00485 x 74.1 = 0.359385gdm-3. This being only accurate to approximately 0.36gdm3 due to the limited precision of the apparatus used. ...read more.

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