Analysis and discussion "TITRATION EXPERIMENT"

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NURUL AINA PUTERI
113194033
PENDIDIKAN KIMIA INTERNASIONAL 2011
UNIVERSITAS NEGERI SURABAYA

G. ANALYSIS DATA

1.      Titration Weak Acid (C₂H₂O₄) and Stong Base (NaOH)

No	N of C2H2O4 (normal)	V of C2H2O4­ (mL)	mol eq of C2H2O4 (mol)	N of NaOH (normal)	V of NaOH­ (mL)	mol eq of NaOH (mol)
1	0,05	5,0	2,5 x 10-4	0,10	5,0	5,0 x 10-4
2	0,05	5,0	2,5 x 10-4	0,10	4,8	4,8 x 10-4
3	0,05	5,0	2,5 x 10-4	0,10	4,7	4,7 x 10-4

Titration weak acid (C₂H₂O₄) and stong base (NaOH) aim to determine the concentration of NaOH solution at the equivalence point of titration,

by using : M₁ x V₁ x e = M₂ x V₂ x e

            The reaction of C₂H₂O₄ and NaOH:

            C₂H₂O_{4 (aq)} + 2 NaOH _(aq) → Na₂C₂O_{4 (aq)} + 2 H₂O _(l)

            At that reaction, there are 2 moles of ion H⁺ which resulting from every moles of C₂H₂O₄ ­(because 1 mole of ion H⁺ used by 1 mole of NaOH). So that, we be able calculate the concentration of NaOH with a known volume of NaOH.

From the titration of weak acid (C₂H₂O₄) and strong base (NaOH) in this experiment, we get that the average concentration of strong base (NaOH) is 0,1 M.

2.      Titration Stong Acid (HCℓ) and Strong Base (NaOH)

No	N of HCℓ (normal)	V of HCℓ (mL)	N of NaOH (normal)	V of NaOH­ (mL)	Total Volume (ml)
1	0,090	5,0	0,100	4,5	9,5
2	0,112	5,0	0,100	5,6	10,6
3	0,088	5,0	0,100	4,4	9,4

The reaction between HCl and NaOH:

            HCl _(aq) + NaOH _(aq) → NaCl _(aq) + H₂O _(l)

Based on that reaction, HCl will have complete ionization in water. And the reaction will be like this:

            HCl _(aq) → H⁺ _(aq) + Cl^- _(aq)

The same thing happened to NaOH:

            NaOH _(aq) → Na⁺ _(aq) + OH^- _(aq)

The neutralization reaction

H⁺ _(aq) + OH^- _(aq)    H₂O_(ℓ)

After complete neutralization of HCℓ, the amount of NaOH left is 0. This is a simple calculation because it involves a complete neutralization reaction and the salt (NaCℓ) does not undergo hydrolysis. At the equivalence point, (H⁺) = (OH^-) and the pH solution is 7,00.

To calculate the concentration of HCl solution, we use:

M₁ x V₁ = M₂ x V₂

From the titration of strong acid (HCl) and strong base (NaOH) in this experiment, we get that the average concentration of strong acid (HCl) is 0,096 M.

3.      Titration Strong Acid (HCℓ) and Strong Base (NaOH) with Naturally Indicator

No	N of HCℓ (normal)	V of HCℓ (mL)	N of NaOH (normal)	V of NaOH­ (mL)	Total Volume (mL)
1	0,086	5,0	0,100	4,3	9,3
2	0,084	5,0	0,100	4,2	9,2
3	0,104	5,0	0,100	5,2	10,2

                       

                        In this last experiment, we use curcumin to be indicator. Curcumin is yellow in acidic and dark yellow in basic solution, but if strong base, it become dark brown. And, because the pH range of curcumic is >7 (more than 7), it’ll base indicator, and it can used as indicator of titration, and with it, we can determine the equivalent point when the end point finally reached. And so, we can concluded that when the colour of the solution change into dark yellow, that signing if the solution has reached the end point, and the pH of the solution after that is more than 7 but it didn’t reach 14 (become strong base).

From the titration of strong acid (HCl) and strong base (NaOH) in this experiment and using natural indicator, that is curcumin, then we get that the average concentration of strong acid (HCl) is 0,091 M.

H.  DISCUSSION

Ø  THE CHANGE COLOUR

            In our experiment, we used some solution, such as NaOH, HCl, C2H2O4, phenolphthalein indicator and plant extract. All solution, except plant extract at first time is colourless. So do when acid (C₂H₂O₄ and HCl) added with phenolphthalein. But, when acid added with indicator then dropped by base (NaOH), the colour of solution became pink. This occurs because phenolphthalein is indicator of base, if phenolphthalein dropped into acid, it’ll be colourless, but if dropped into base, the colour become red. And in this case, in our experiment, the changing of colour is signing that the solution in the equivalent point.

In plant extract (curcumic plant) the colour is yellow, but after dropped with NaOH, the colour became dark yellow. This occurs because curcumic extract when dropped with acid solution became bright yellow, and if dropped with base solution became dark yellow. So, the signing colour to knowing that the solution at equivalent point is if the solution change into dark yellow.

In our experiment, the entire change colour of all solution is suitable with the hypothesis.

Ø  THE CONCENTRATION OF ACID BASE SOLUTION

The aim of this experiment is to determine the concentration of acid base solution by neutralization reaction that is titration.

We can calculate or determine the concentration of NaOH solution and HCl solution, which first by knowing the volume of NaOH then we can determine the concentration of NaOH with oxalic acid (C₂H₂O₄), when the titration process between the equivalence point and at the end point, which is there’s changing colour of the solution became pink (because of there are phenolphthalein that be an indicator if the solution at the end point) like in the basic theory. But when we repeated in the third experiment (determining the concentration of HCl by using plant indicator), experiment for the second, we got different volume, that didn’t same with the first and the third. This occurs because maybe caused by our mistake when we adding HCl into the conical flask more than 5 mL, so it reached end point must with the large volume of NaOH too or maybe we get difficulties when determined the end point of the titration.

I.                   CONCLUSION

From the experiment we had done, first, we got the concentration of NaOH with C₂H₂O₄ solution using phenolphthalein indicator that is 0,1 M. Second, we got the concentration of HCl with NaOH solution using phenolphthalein indicator that is 0,096 M. And the third, we got the concentration of HCl with NaOH solution using plant extract that is 0,091 M. And as we had calculated, the concentration of HCl difference between using phenolphthalein and using plant extract is not far.

REFFERENCES

Brady, E.James.General Chemistry:Principle and Structure.5^th Ed.2006.USA:John Wiley&Sons Inc.

Chang, Raymond.2005. General Chemistry : The Essential Concepts.3^rd Ed. USA: Mc Graw Hill

ATTACHMENT

C2H2O4 added with phenolphthalein      →