Laporan Praktikum Kimia Preparing Primary Standard Solution

PREPARING PRIMARY STANDARD SOLUTION

    A.    Date : March 15 2017

    B.     Objectives

1.      To prepare 100 mL of 1 N oxalic acid

2.      To dilute oxalic acid solution

3.      To determine concentration of diluted primary standard solution

    C.    Theoretical Background

   A chemical analysis that is performed primarily with the aid of volumetric glassware (e.g., pipettes, burets, volumetric flasks) is called volumetric analysis. For a volumetric analysis procedure, a known quantity or a carefully measured amount of the substance react with a tube-determined amount of another substance with the reaction occurring in aqueous solution. The volumes of all solutions are carefully measured with volumetric glassware. The known amount of the substance for an analysis is generally measured and available in two ways:

1.      As a primary standard: A precise mass (and thus, moles) of solid substance is measured on a balance, dissolved in water, an then reacted with the substance being analyzed example H₂C₂04.₂H₂0.

2.      As a standard solution: A measured number of moles of substance is present in a measured volume of solution-a solution of known concentration, generally expressed as the molar concentration (or molarity) of the substance. A measured volume of the standard solution then reacts with the substance being analyzed example NaOH.

    Primary standards are usually salts or acid salts of high purity that can be dried at some convenient temperature without decomposing and that can be weighed both at high degree of accuracy. A Primary standard solution has certain characteristics such as high purity, soluble in water, stable in air, high molar mass, etc.

(Prima, Eka Cahya & team, 2017).

(Faculty.kfupm.edu.sa)

   D.    Material and Apparatuses

Material:

1.      Oxalic acid (H₂C₂04.₂H₂0)

2.      Aquadest

Apparatuses:

1.      Beaker glass 100 mL (1)

2.      Volumetric flask 100 mL

3.      Stirring rod (1)

4.      Spatula (1)

5.      Volumetric pipette 10 mL(1)

6.      Bulb pipette (1)

7.      Watch glass (1)

8.      Drop pipette (1)

9.      Glass funnel (1)

10.  Aquadest bottle (1)

    E.     Procedure and Observation

No.	Procedure	Observation
1.	Preparing Primary Standard Solution of Oxalic Acid      ·         6,3grams of oxalic acid crystal is weighed by watch glass.      ·         The weighed oxalic acid crystal is placed in a beaker and solved with a small quantity of water.      ·         The oxalic acid solution transferred carefully to 100 mL volumetric flask by a funnel.      ·         Water is then added up to graduation line of volumetric flask.      ·         The solution shaken for at least 12 times.	·  In the term of the phase oxalic acid crystal is solid.      · The color is white.      ·  Has no smell     · When a small quantity of water is added, the temperature decrease and the color become cloudy. ,   · After they stirred with the stirring rod in the beaker glass, the oxalic acid crystal is totally dissolved.   · After water is added into 100 mL volumetric flask, the solution become colorless and there is no more crystal can be seen.
2.	Diluting Solution      ·  10 mL of oxalic acid is taken by using volumetric pipette.     · Then it is transferred into another 100 mL of volumetric flask.     · Water is added to volumetric flask up to the graduation line.	·   No change in color, smell, and temperature except change in volume.

    F.     Data Analysis

Known:

-          N : 1 N

-          Mr : 126 gr/mol

-          Gr : 6,3 gram

-          V₁ : 10 mL = 0,01 L

-          M₁ : 0,5 M

-          V₂ : 100mL = 0,1 L

                        Asked:

                        M₂: ……………?

                        Answer:

                                              n₁ = n₂

                                                  M₁ x V₁ = M₂ x V₂

                        0,5M x 0,01L = M₂ x 0,1L

        M₂ = 0,5M x 0,01L

                                                             0,1L

                                            M₂ = 0,05M

-          Gram after diluted

                                  Gr = n x Mr

                                       = 0,005 M x 126 gr/mol

                                       = 0,63gram

-          Gram of Oxalic Acid (H₂C₂0₄ . 2H₂O)

N₂ = M₂ x V₂

     = 0,05M x 0,1L

     = 0,005 mol

   G.    Discussion

Based on the theory, one of the characteristics of primary standard solution is soluble in water, which is also in line with the experiment where we can dissolve oxalic acid crystal into water. When the oxalic acid crystal solved with a small quantity of water, the color become cloudy, and the temperature decrease, because the oxalic acid crystal is totally dissolved. And when water added up to the graduation line of volumetric flask, the solution become colorless and there is no more crystal can be seen.

   H.    Conclusion

The experiment is line with the theory. Because, the oxalic acid crystal soluble in water. We can prepare

100 mL of 1 N oxalic acid. We can determine the concentration of diluted primary standard solution

using the formula M₁xV₁ = M₂ xV₂. So, we find the concentration is 0.05 M.

    I.       References

Prima, Eka Cahya & team (2017). Science Laboratory Experiment 1 First Edition. Bandung: Universitas Pendidikan Indonesia.

Faculty.kfupm.edu.sa

Share this post