Method
Starting with one of the known concentrations measure out 25cm3 of it for the titration using the volumetric pipette.
Assemble apparatus (as shown in diagram) after collecting goggles and lab coat for safety.
Move your apparatus to eve level (i.e. to a stool) and pour the HCl in till the meniscus rests on the 0 level exactly so that your results can be measured accurately from the same marker every time.
Move the apparatus back onto the table, and measure 25cm3 of calcium hydroxide accurately with the volumetric pipette (ensuring that it is clean, washed with distilled water then the solution you are using) and pour it into a conical flask.
Add a few drops of phenolphthalein indicator which will make the solution pink and you can tell when the end point is near so make it more accurate.
Turn on the tap from the burette and let the HCl run into the pink Ca(OH)2. Shake the flask constantly to evenly distribute the HCl in the solution for accuracy.
Keep the tap running until clear patches start to appear in the swirling solution in the flask then slow the tap down and let the HCl drip in one drop at a time, all the time mixing it in, until the solution goes completely colourless. This is the End Point and an equilibrium has been reached, as the solution is neutral.
Make a final reading by moving the burette and stand back onto a stool and reading it at eye level, from the bottom of the meniscus. Record the result to 2 decimal places for accuracy.
Results Based on Preliminary
I only had to titrate one of the provided solutions because the 0.1 solution equalised at 11.25 cm3. This is not within the specified range (15cm3 and 30 cm3) so I had to make up a weaker solution to get the titration within the specified range. I decided to make up a 0.05 moldm-3 solution by diluting the 0.1moldm-3 solution 50:50 with water. To do this I measured 125cm3 of water in 25cm3 amounts with the volumetric pipette and poured them into the volumetric flask then did the same, 5 times for the 0.1moldm-3 HCl solution. Now I had to titrate the 0.05 moldm-3 solution 3 times to get results for calculation later.
Method
Follow exactly the same method as above and repeat at least 3 times with results within 0.05cm3 of each other for accuracy.
Results Table
** Experiment no 1 was my trail using the 0.05moldm-3 solution, this was to make sure that it was in the range required and hasn’t been included in the average as it wasn’t so accurate.
Calculation for concentration of Ca(OH)2
Ca(OH)2 + 2HCl → CaCl2 + 2H2O
1mol 2mol 1mol 2mol
Therefore the exact neutralisation reaction will require 1 mole of Ca(OH)2 to react with 2 moles of HCl.
In the equation :-
Where V is Volume, c is Concentration and n is number of moles.
Let the Calcium Hydroxide be solution A, and the Hydrochloric Acid be solution B.
To work out the concentration of A, cA, we need to know all the other factors which make up the formula.
Number of Moles in HCl, nB:
