Experiment to determine the strength of the given solution ph-metrically
Answers
1. 0.1(M) NaOH solution is provided.
2. HCl solution of unknown strength is provided.
3. Calibrate the pH meter with the solutions of pH 4,7 and 10.
4. pH-metric Titration: Clean the electrode with distilled water and
wipe them with tissue paper or filter paper. Take 25mL of HCl
solution in a 50 mL beaker and immerse the electrode in it. Note
down the pH range.Rinse the burette with distilled water and then
with NaOH solution.After that fill the burette with NaOH solution.
The reading shown on the scale of pH meter is pH value of the HCl
solution. Add NaOH solution drop wise from the burette (maximum
0.5 mL at a time), shake the solution well with the help of glass rod
and note the corresponding pH values. Near the end point, volume of
NaOH added should be as small as possible (0.1 ml at a time, which is
the least count of an burette that we use in our laboratory) because the
acid is neutralized and there will a sharp increase in pH values.
Further addition of even 0.01 mL of NaOH, increase the pH value to
about 9–10. Put back the selector to zero position after each pH
measurement, and always keep the selector at zero position when it is
not in use.
Plot the graph of pH of solution v/s volume of NaOH added.
OBSERVATIONS AND CALCULATIONS
1. Preparation of 250 mL 0.05 Mstandard oxalic acid solution:
Mass, w of oxalic acid to be weighed for the preparation of
solution
w= .05×126×250= 1.5750 g
1000
Mass of empty weighing bottle = x =