Acid and Base Titration

Title: Acid and Base Titration

Objectives:

1. To determine the concentration of sodium hydroxide solution through titration technique using hydrochloric acid and sulfuric acid.
2. To apply the correct technique in titration.
3. To carry out acid base titration using phenolphthalein.

Data and Result:

a) Dilution

M1V1 = M2V2

b) Titration

1. Using HCl

Reading	1	2	3
Volume of HCl used (ml)	44.70	43.80	42.30

Average volume of HCl used = 43.80ml + 42.30

2

= 43.05ml

Equation:

HCl (aq) + NaOH (aq) à NaCl (aq) + H2O (l)

V HCl = 43.05 ×10^-3 L V NaOH = 25 ×10^-3 L

M HCl = 1.000×10^-2M M NaOH =?

Titration:

MaVa = a

MbVb b

(1.000×10^-2M)( 43.05 ×10^-3 L) = 1

Mb (25ml ×10^-3 L) 1

Mb = 1.72×10^-2M

Thus, the concentration of dilute C solution (NaOH) is used to neutralize is1.72×10^-2M.

To get the concentration of the C solution before dilution :

Using M1V1 = M2V2

M1=Mc= ? M2=1.72×10^-2M

V1=Vc = 10ml V2 = 250 ml

Note that M1V1 is the information of C solution before dilution, n M2V2 is after dilution.

M1V1 = M2V2

(M1)(10ml)=( 1.72×10^-2M)( 250 ml)

M1= 0.43 M

Thus, the concentration of C solution before dilution is 0.43M.

2. Using H₂SO₄

Reading	1	2	3
Volume of H2SO4 used (ml)	22.60	22.90	22.20

Average volume of H₂SO₄ used = 22.90 + 22.20

2

= 22.55ml

Equation:

H₂SO₄ (aq) + 2NaOH (aq) à 2H₂O (l) + Na₂SO₄ (aq)

V H₂SO₄ = 22.55 ×10^-3 L V NaOH = 25 ×10^-3 L

M H₂SO₄= 1.000×10^-2M M NaOH =?

Titration:

MaVa = a

MbVb b

(1.000×10^-2M)(22.55 ×10^-3 L) = 1

Mb (25 ×10^-3 L) 2

Mb = 1.80×10^-2M

Thus, the concentration of NaOH is used to neutralize is 1.80×10^-2M.

Discussion

From this experiment, we have undergone 2 process, which is dilution and titration process. Before titration, the original C solution had been dilute. The dilution must be done to know the original concentration of C solution by comparing between the data of original C solution and the data from dilute C solution.

Then, this experiment also shows the distinct results by using different type of acid to neutralize with NaOH solution. Even the concentration of NaOH is approximately same through the neutralization process between 2 different acids, the volume is very different. Thus, H2SO4 is more acidic compared to HCl. This is due to the usage of volume of acid that is used to neutralize the base solution. H2SO4 only required in small amount compared to the volume of HCl used to neutralize NaOH. H2SO4 contain 2 atoms of hydrogen in each H2SO4 molecules which help to increase the rate of neutralization while HCl contain only 1 atom of hydrogen per molecule.

Moreover, the safety must be noticed to get the more precise, accurate and constant result. The burette and pipette must be rinse with HCl or H2SO4 respectively because we don’t want water inside the apparatus will affect the concentration of acids used. Furthermore, the repeated reading must be done and the first reading act as trial reading. Only the second and third reading had been used to obtain the average data. These will make the result more accurate.

From the titration, we had used the phenolphthalein solution as indicator to show the salt formed. When the equilibrium formed, the magenta color will change dramatically to colorless. From that, we will obtain the end point of acid used and could get the volume of acid solution to neutralize the basic solution, NaOH (aq).

Conclusion

We should do the correct titration process in determining the concentration of unknown concentration either acid or base. Phenolphthalein is the indicator in these neutralization processes by titration.