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Lab # 1
Standardization of 0.1N
sodium hydroxide (NaOH)
TA : Halah Almutairi
PURPOSE:
To standardize a solution of NaOH (secondary
standard solution)
by titration with (a primary standard) potassium
hydrogen phthalate( KHP).
Type of chemical reaction :
Direct Acid-Base Titration
What are we doing in this experiments?
To determine the
Conc of 2ry st.soln
(NaOH) by
Finding e.p
PRINCIPLE:
Sodium hydroxide solution need
standardization , why ??
A solution of NaOH is secondary standard
solution because its tends to absorb atmospheric
carbon dioxide which is weakly acidic. The
reaction between the CO2 and NaOH partially
neutralizes the NaOH solution, which means that
the 0.100 M solution of NaOH you think you're
preparing today will NOT be 0.100 M tomorrow
(concentration will change). For this reason it is
necessary to standardize NaOH solutions to be
used in titrations.
PRINCIPLE:
Standardization is typically carried out by titrating
the NaOH solution with a primary standard acid
such as potassium hydrogen phthalate (KHP)
KHP + NaOH ---------->>KNaP + H2O
Use an acid-base
indicator:
phenolphthalein,
which is colorless in
acid solution and
pink in basic solution
E.P
Safety Precautions in handling Sodium
Hydroxide:


Sodium hydroxide Corrosive ,, in high
concentration Causes eye damage and severe skin
burns
If contact the eye,,Immediately flush eyes with
water ,Remove any contact lenses and continue to
flush eyes with water
If contact the skin,, Flush skin with water , then
wash thoroughly with soap and water
(( Contact a physician if need ))

Procedure:
1-Pipette 10 ml of 0.1N KHP into conical flask
2- Add 10 drops of phenolphthalein indicator
3- Titrate with 0.1N NaOH
The end point: when the solution change from
colorless to faint pink color
Calculation :
At the end point

N.V = N''.V'‘
N= unknown conc of 2ry st.soln (NaOH)
V=End point in mls of 2ry st.soln (NaOH)
N” = known conc of analyte (KHP)
V’’ = known volume of analyte (pipette 10mls)