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I have to plan an experiment to find the solubility of calcium hydroxide, Ca(OH)2, in water. I have to make up a solution of calcium hydroxide and carry out a titration using hydrochloric acid solution of the chosen concentration

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Introduction

Determination of the solubility of calcium hydroxide I have to plan an experiment to find the solubility of calcium hydroxide, Ca(OH)2, in water. I have to make up a solution of calcium hydroxide and carry out a titration using hydrochloric acid solution of the chosen concentration. The equipment need is as below: * Solid calcium hydroxide * Methyl orange indicator * Volumetric flask (250cm3) * Clamp and boss * Clamp stand * Burette (50cm3) * Conical flask * Pipette (25cm3) * Pipette filler * Distilled water * White spotting tile * Hydrochloric acid of chosen concentration * Beaker x2 * Rubber bung * Funnel x2 * Electronic scale 'The maximum mass of calcium hydroxide needed to produce 1dm3 of saturated solution at room temperature is 1.5g.' I only want 250cm3 as I am using a 250cm3 volumetric flask. Therefore: 1dm3 / 4 = 250cm3 1.5g / 4 = 0.375g The number of moles in volumetric flask: 0.375 / 74 = 0.005 moles I need an excess of 0.5g to make sure that all the calcium hydroxide has been fully dissolved: 0.375g + 0.5g = 0.875g I have to now work out the concentration of hydrochloric acid I will be using. The molar mass of calcium hydroxide is: C = 40 O = 16 (x2) H = 1 (x2) R.A.M = 74 The concentration of calcium hydroxide at the beginning will be: 1.5 / 74 = 0.02 So, the concentration is 0.02 mol/dm3 In ...read more.

Middle

After being rinsed, take out 25cm3 of calcium hydroxide from the volumetric flask, using the pipette. 25cm3 is easily measured on the pipette, as there is a mark line. Be careful when doing this, as if you suck up the solution too quickly with the pipette, then air gaps form in the pipette, and this means you will not have a full 25cm3 of solution, making the experiment unreliable. After, release the solution of calcium hydroxide into the conical flask. Add four drops of methyl orange indicator to the conical flask, and the solution will now turn orange. Titration The burette will be rinsed out with 0.04 mol/dm3 hydrochloric acid, so during the experiment, the hydrochloric is not contaminated with solutions previously used in the burette. Before rising out the burette, make sure that the tap is closed in the horizontal position. Bring the burette down to a level where you can be pouring into it at your height level, so you do not have to reach up, otherwise this could be a hazard. Place a funnel inside the top of the burette, and carefully pour the hydrochloric acid into the burette via the funnel. Once full to the top, open the tap, and let the dirty hydrochloric drain into a beaker. Once the burette has been thoroughly rinsed, close the tap again, and pour in fresh 0.04 mol/dm3 of hydrochloric acid. Fill the burette to the top, where the reading will be 0cm3. ...read more.

Conclusion

Then follow the method used for the first titration. The results will be recorded in a table which has rows, with the initial volume reading of the burette, final volume on burette, and the volume of acid used. The columns will be the titration number, and the end column will be the mean volume used. Calculation of the solubility of calcium hydroxide * Moles of Hydrochloric acid: = concentration x volume = 0.04 mol/dm3 x mean volume * There is for every one moles of calcium hydroxide, two moles of hydrochloric acid, therefore we need to divide the amount of moles of hydrochloric acid by two, to get the number of moles of calcium hydroxide. The number of moles of Ca(OH)2 = mean x 0.04 in one solution of volume 25cm3 2 * We want the number of moles of calcium hydroxide in 1dm3 of water, therefore we need to work out its concentration. Moles of Ca(OH)2 in dm3 = mean (dm3) x 0.04 x 1000 2 x 25 * The molar mass of calcium hydroxide is 74. If we multiply the concentration of calcium hydroxide by the molar mass, then this will tell us the amount of solid calcium hydroxide which will dissolve in 1dm3 of water. 20 Solubility of Ca(OH)2 in g/dm3 = mean x 0.04 x 1000 x 74 2 x 25 = mean x 0.04 x 20 x 24 = mean x 59.2 g/dm3 ?? ?? ?? ?? Dipen Patel Chemistry Planning Page 1 ...read more.

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