Lab # 1 Standardization of 0.1N sodium hydroxide (NaOH)

TA : Halah Almutairi

PURPOSE:

To standardize a solution of NaOH standard solution) (secondary 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 2 ry 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)