Standardization of 0.1N sodium hydroxide

(NaOH)TA : Halah Almutairi

Lab # 1

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:

PRINCIPLE: 

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.

 

Sodium hydroxide solution need standardization , why ??

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 

E.P

Use an acid-base indicator: phenolphthalein, which is colorless in acid solution and pink in basic solution

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)