Move the apparatus back onto the table, and measure 25cm3 of methanoic acid 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 Methanoic acid run into the pink solution. Shake the flask constantly to evenly distribute the Methanoic acid 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 Methanoic acid 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.
then did the same, 5 times for the Methanoic acid solution.
Results Table
** Experiment no 1 was my trial 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 NaOH
NaOH + 2Methanoic acid → CaCl2 + 2H2O
1mol 2mol 1mol 2mol
Therefore the exact neutralisation reaction will require 1 mole of NaOH to react with 2 moles of Methanoic acid.
In the equation :-
Where V is Volume, c is Concentration and n is number of moles.
Let the Methanoic acid be solution A, and the Methanoic 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 Methanoic acid, nB:
22.62 cm3 = 22.62/1000 dm3
= 0.02262 dm3
No of Moles = Concentration x Volume (dm3)
= 0.05 x 0.02262
= 0.011308
= 1.13 x 10-3 mol
No of Moles of NaOH :-
Ratio of Solutions according to balanced equation = Methanoic acid : NaOH
= 2 : 1
Therefore number of moles in NaOH , nA, = 1.13 x 10-3 mol / 2
= 5.65 x 10-4 mol
Now I have all the other parts of the main equation apart from cA so I can work out cA.