Experiment V01
Chemicals:
Standardization of NaOH and HCl solution
Oxalic acid dihydrate(H2C2O42H2O), (1.6 g)
approx. 0.1 M HCl, (100 cm3)
approx. 0.1 M NaOH, (100 cm3)
borax(Na2B4O710H2O), (4.9 g)
methyl orange indicator,
phenolphthalein indicator.
Apparatus:
Burette,
25 cm3 pipette,
250 cm3 conical flasks(2),
250 cm3 volumetric flask,
white tile,
250 cm3 beakers(2),
wash bottle,
glass rod,
weighing bottle,
clamp and stand.
Procedure:
A.
Standardization of NaOH solution
a.
Weigh out accurately about 1.60 g of oxalic acid dihydrate crystals (H2C2O42H2O) in a
weighing bottle. Using a 250 cm3 beaker, dissolve the acid in distilled water, then transfer
the solution completely to a 250 cm3 volumetric flask and make up to the mark with
distilled water, shake well.
b.
Fill a burette with the standard oxalic acid solution.
By pipette take 25.0 cm3 of the given alkali solution, run it into a conical flask, add two or
three drops of phenolphthalein solution. Make a note of the burette reading and run in the
acid from the burette. The first 15 to 20 cm3 of the acid may be run in 5 cm3 at a time
without fear of overshooting the end-point. Then run in 1 cm3 at a time, shaking after
each addition until the solution becomes colourless. Note the burette reading again. This
is a trial titration and its results is not used in the calculation.
c.
Now repeat the titration with further portions of 25.0 cm3 of the alkali solution until two
readings are obtained which agree to 0.10 cm3.
d.
Calculate the concentration of the oxalic acid solution that has been made up, then, using
the titration results, calculate the concentration of the alkali.
The reaction is as follow:
2NaOH(aq) + H2C2O4(aq)  Na2C2O4(aq) + 2H2O(l)
P.1
Experiment V01
Standardization of NaOH and HCl solution
B.
Standardization of HCl solution:
a.
Weigh out accurately about 4.8 g of pure borax (disodium tetraborate decahydrate,
Na2B4O710H2O) in a weighing bottle. Using a 250 cm3 beaker, dissolve the borax in
distilled water, transfer the solution, together with the rinsing, into a 250 cm3 volumetric
flask and then make up to the mark with distilled water, shake well.
b.
Fill a burette with the hydrochloric acid.
By pipette take 25.0 cm3 of the borax solution, run it into a conical flask, add two or three
drops of methyl orange indicator and titrate with the given hydrochloric acid solution.
The end-point is reached when the colour just changes from yellow to orange.
c.
Now repeat the titration with further portions of 25.0 cm3 of the borax solution until two
readings are obtained which agree to 0.10 cm3.
d.
Calculate the concentration of the borax solution that has been made up, then using the
titration results, calculate the concentration of the hydrochloric acid.
The reaction between borax and hydrochloric acid is as follows:
Na2B4O7(aq) + 5H2O(l) + 2HCl(aq)  2NaCl + 4H3BO3(aq)
P.2
Experiment V01
Standardization of NaOH and HCl solution
Name:
Seat No.:
Date:
Grade:
A.
1.
Standardization of NaOH solution
Mass of H2C2O42H2O used =
Molar mass of H2C2O42H2O =
Volume of H2C2O4 prepared =
[H2C2O4] =
=
2.
Titration results
Titration
1 (trial)
2
Final burette reading (cm3)
Initial burette reading (cm3)
Volume of acid used (cm3)
Average volume of oxalic acid used =
3.
2NaOH(aq) + H2C2O4(aq)  Na2C2O4(aq) + 2H2O(l)
[NaOH]
×
=
×
×
[NaOH] =
P.3
3
4
Experiment V01
Standardization of NaOH and HCl solution
Name:
Seat No.:
Date:
Grade:
B.
1.
Standardization of HCl solution
Mass of borax used =
Molar mass of borax =
Volume of borax solution prepared =
[Na2B4O7] =
=
2.
Titration results
Titration
1 (trial)
2
Final burette reading (cm3)
Initial burette reading (cm3)
Volume of acid used (cm3)
Average volume of HCl used =
3.
Na2B4O7(aq) + 5H2O(l)+ 2HCl(aq)  2NaCl(aq) + 4H3BO3
[HCl]
×
=
×
×
[HCl] =
P.4
3
4