Chemistry Titration Lab

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Table 1: Data Collection Table – Contains all of the primary data directly obtained from the lab. Indicator | Initial volume of NaOH in burette (ml) ±0.05| Final Volume of NaOH in burette (ml) ±0.05| Final – initial Burette Reading (Volume of NaOH used) (ml) ±0.1| Qualitative Observations | Phenolphthalein | 0.00 | 0.90| 0.9| At first when the base was being dropped into the vinegar there wasn’t a color change, however when the solutions came close to full titration, the solution would turn pink and once mixed would turn clear again| | 0.90| 2.30| 1.4| |

| 2.30| 3.20| 0.9| |
| 3.20| 4.10| 0.9| |
Bromothymol Blue | 8.00| 9.50| 1.5| Solution turned from yellow to light green | | 9.50| 11.10| 1.6| Solution turned from a bright yellow to bright blue rather than a light green indicating over-titration had occurred| | 11.10| 12.90| 1.8| |

| 12.90| 14.40| 1.5| |
| 14.40| 15.90| 1.5| |
Methyl Orange | 15.90| 16.90| 1.0| Reaction occurred quick, over-titration occurred and solution turned from red to orange | | 16.90| 17.20| 0.3| |
| 17.20| 17.40| 0.2| |
| 17.40| 17.60| 0.2| |
| 17.60| 17.80| 0.2| |
Methyl Red | 0.00| 5.00| 5.0| |
| 5.00| 7.80| 2.8| Solution turned from red to a light orange/yellow color| | 7.80| 10.70| 2.9| |
| 10.70| 13.60| 2.9| |
| 13.60| 16.50| 2.9| |
Bromocresol Green| 20.80| 21.20| 0.4| Solution turned from yellow to light green | | 21.20| 21.60| 0.4| |
| 21.60| 22.00| 0.4| |

Table 2: Data Processing Table displaying the volume of NaOH required to titrate 10ml of vinegar and their corresponding concentration of acetic acid Indicator | Volume of NaOH required to titrate 10mL of Vinegar (ml) (±0.1)| Concentration of Acetic Acid ±0.5 (mol/l) | Percent Uncertainty (%)| Percent Error (%) | Phenolphthalein| 0.9| 0.9mol/dm3| 11.1| 3.4|

Bromothymol Blue | 1.5 | 1.5mol/dm3| 6.7| 72.0|
Methyl Orange| 0.2| 0.2mol/dm3| 50.0| -77.0|
Methyl Red | 2.9| 2.9mol/dm3| 3.5| 233.0|
Bromocresol Green| 0.4| 0.4mol/dm3| 25.0| -54.0|

Sample Calculations:
Ex. The calculation of the concentration of acetic acid for phenolphthalein NaOH Volume: 0.9ml
NaOH Concentration: 1.00mol/dm3
1. Convert Volume to Litres

0.9 = 0.0009L
1000

1. Calculate the moles of NaOH (n=CV)
n= (1.00mol/dm3) (0.0009L)
= 0.0009mol
2. Calculate the concentration of the diluted acetic acid. Because acetic acid and sodium hydroxide have a 1:1 ratio, they have the same number of moles. C = 0.0009mol = 0.09
0.01L
3. Calculate the initial concentration of acetic acid pre-dilution C1V1 = C2V2
C1(0.01L) = (0.09mol/L)(0.1)
Concentration of Acetic Acid = 0.9mol/L
Sample Calculations Continued
4. Calculating percent uncertainty

= absolute uncertainty x 100
Measurement 1
Example: Calculating the percent uncertainty for the volume of NaOH required when methyl red is used

= 0.1 x 100
2.9 1
= 3.5%
Therefore, the volume of NaOH required when methyl red is used as the indicator is 2.9ml ± 3.5%

5. Uncertainty propagation for the volume of NaOH required for each indicator (0.9 ± 0.1) + (1.5 ± 0.1) + (0.2 ± 0.1) + (2.9 ± 0.1) + (0.4 ± 0.1) = 5.9ml ± 0.5

6. Calculating percent error
Percent error = Actual – accepted x 100
accepted
Example: Calculating percent error for phenolphthalein
Percent error = 0.9 – 0.87 x 100
0.87
= 3.4%
Methyl Red
Methyl Red
Bromothymol Blue
Bromothymol Blue
Bromocresol Green
Bromocresol Green
Methyl Orange
Methyl Orange
Phenolphthalein
Phenolphthalein

Graph 1: Titration curve representing the effect of the volume of NaOH on the pH of the titration solution at end point

Conclusion
This lab tested the effect of the use of different indicators on the...
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