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Thursday, 17 April 2014

PREPARATION OF 50% NaOH

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PREPARATION OF 50% NaOH

50% NaOH contains 50%w/w sodium hydroxide and for 50g of the compound is containd in every 100ml of its solution.

Sodium hydroxide are made as solid deliquescence  pellets.

Deliquescence substances are chemical compound that tend to absorb so much water from the atmosphere that they dissolve in it to form an aqueous solution of the compound.


50%w/w NaOH contains 12.5M NaOH

From

Molar Mass of each element Na=23, O=16, H=1

Molar Mass of NaOH= 23+16+1

                                      =40g

Number of Mole=       Mass

                                    Molar mass

From

50% NaOH

The mass of NaOH in 100ml of it solution is 50g

Thus

Number of Mole of NaOH =       Mass

                                                        Molar mass

Number of Mole of NaOH =       50

                                                         40

                                          =  1.25moles

In 1000ml or 1liter of the NaOH

Molar Concentration =              Mass                 X  1000

                                                       Molar mass         Volume

or

Molar Concentration =              Number of mole                    X  1000

                                                                                                             Volume

Molar Concentration =              50                      X  1000

                                                      40                           100

Molar Concentration =                 12.5M

Or

Since the number of mole of 50% NaOH in 100ml of the solution  is 1mole

Therefore

Molar Concentration =              1.25                  X  1000

                                                                                         100

Molar Concentration =              12.5M

Preparation Procedure

1.     Make available an accurate analytical weighing balance, clean dry 500ml beaker, distilled/deionized water, stirrer, 1000ml Volumetric flask and Spatula

2.     Place the beaker on the balance and tare/zero the reading

3.     With the aid of the spatula weigh 500g of the NaOH pellet into the clean beaker

4.     Add about 400ml of distilled/deionized water and stir to dissolve the pellets (Note: the reaction is exothermic because heat will be given up thereby causing increase in the temperature of the beaker, ensure you stir gently)

5.     When all the pellets have dissolved, transfer the solution into the 1000ml volumetric flask. Allow to cool

6.     Add distilled/deionized water to the mark, shake and allow to cool

7.     On cooling decrease in volume of the solution will be noticed, add distilled/deionized water again to the mark and shake.

Note:

1.     NaOH has high affinity for water thus this is why there is decrease in the solution after making up to the mark

2.     Due to the high affinity for moisture in the atmosphere the weighing should be done in vacuum or less aerated place at a fast speed.

3.     Deionized water is best for the preparation of this solution because of it lack of ions, which when present can interfere with the NaOH in the solution.

 

 

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