Determine the Concentration of Calcium Hydroxide

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Determine the Concentration of Calcium Hydroxide

2HCl (aq) + Ca (OH)2(aq) [IMAGE] 2H20(l) + CaCl2(s)

In this experiment I need to find out the concentration of calcium

hydroxide. I am provided with 250cm3 of limewater, which has been made

such that it contains 1g dm-3 of calcium hydroxide. To increase the

accuracy of the results it would be helpful if the volume of the

alkali equalled the volume of the acid used, and I know that the

concentration of the alkali is approximately 1gmdm-3 which is roughly

equal to 0.013mol by using the equation

Mole = Mass / Mass of one mole

=[IMAGE]

=0.013 moldm-3

Also I am provided with hydrochloric acid, which has a concentration

of exactly 2.00 moldm-3. The acid is too concentrated to be used, so I

need to dilute it. Using acid that is twice the molar of the alkali

should result in equal volumes of each being used. So

* 0.013 * 2 = 0.026 M

*and taking the molar of the acid down by a factor of one hundred

would work well.

Calcium hydroxide and hydrochloric acid are in the ratio 1:2.

For this, I will need the pipette and the pump to collect exactly 25cm3

taking into account parallax errors where the level of the 25cm3 line

is at the bottom of the meniscus. By placing this in a volumetric

flask and topping it up to 500cm3 with distilled water taking into

account the parallax error again. Stopper the flask and shake the

flask thoroughly (by inverting it a number of times) so that the

entire volume is of precisely the same concentration. This will have

taken the molar down to 0.2M so by repeating this process again the

molar will be taken down to 0.02M, which is now ready for the

titration. I performed the titration with the hydrochloric acid of

0.02 moldm-3 in a burette and 25cm3 calcium hydroxide in a conical

flask. I considered the first reading as a rough reading and took

another three readings, so that no anomalous result might occur.

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