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Valdosta State University
Experiment 5NaOH Standardization
Valdosta State University
Valdosta State University
Purpose
To accurately determine the concentration of a sodium hydroxide solution by titration.
Valdosta State University
Valdosta State University
Background
Base Standardization
Process of accurately determining the concentration of a base by reacting it with a known quantity of acid (KHP).
KHC8H4O4(aq) + NaOH(aq) KNaC8H4O4(aq) + H2O(l)
KHC8H4O4 - Potassium Hydrogen Phthalate (KHP)
Valdosta State University
Valdosta State University
Background
• In a titration, a known mass of KHP is reacted with just enough NaOH to neutralize it.
• The equivalence point occurs when just enough NaOH has been used to neutralize the KHP.
• The equivalence point is not always visible; so, an indicator is added.
Valdosta State University
Valdosta State University
Background
• The equivalence point and the endpoint are independent chemical reactions.– the equivalence point occurs at the neutralization of the acid.– the endpoint occurs at the neutralization of the indicator.
• A good standardization depends on the proper selection of an indicator.
• For this experiment (strong base, weak acid) phenolphthalein is a good selection.
Valdosta State University
IndicatorA substance, usually a weak acid, which changes color in response to pH.
Valdosta State University
Procedure – Experiment 5
- For this experiment, work individually (i.e. groups of one).
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Technique - Titration
Clean The Buret1. Rinse a buret twice with distilled water. 2. Rinse the buret twice with 10-mL portions of your
prepared NaOH solution. 3. Run some of your prepared NaOH solution through
the tip of the buret. 4. Drain the buret, then fill it with your prepared NaOH
solution. 5. Let some of your prepared NaOH solution run through
the tip of the buret so that all air bubbles are removed.
Valdosta State University
Technique - Titration
Clean The Buret
Valdosta State University
Technique - Titration
Prepare the KHP1. Weigh 0.4 g to 0.5 g of KHP to the nearest 0.001 g
into each of three 125-mL Erlenmeyer flasks. 2. Add approximately 30 mL of distilled water to each
flask and stir well until all KHP is dissolved. 3. Add three drops of phenolphthalein indicator to each
Erlenmeyer flask.
Valdosta State University
Technique - Titration
Performing The Experiment1. Record the volume of NaOH in the buret.
Valdosta State University
Technique - Titration
Performing The Experiment1. Record the volume of NaOH in the buret.2. Start adding NaOH, swirling the flask during the
addition.
Valdosta State University
Technique - Titration
Performing The Experiment1. Record the volume of NaOH in the buret.2. Start adding NaOH, swirling the flask during the
addition.3. As a pink color appears, the addition of NaOH is
slowed.4. As the pink color becomes more persistent, slow the
addition further.5. Stop the addition when the pink color persists for five
seconds.6. Record the volume of NaOH in the buret.
Valdosta State University
Technique - Titration
Performing The Experiment6. Record the volume of NaOH in the buret.
Valdosta State University
Technique - Titration
Valdosta State University
Technique - Titration
Valdosta State University
DataTrial 1 Trial 2 Trial 3
Mass KHP 0.433g 0.409g 0.406g
Moles KHP
Initial buret reading
1.42 mL 1.00 mL 1.25 mL
Final buret reading
19.40 mL 18.30 mL 18.45 mL
Volume NaOH used
Molarity NaOH
Average Molarity NaOH
Std. dev.
Percent relative std. dev.
Valdosta State University
DataTrial 1 Trial 2 Trial 3
Mass KHP 0.433g 0.409g 0.406g
Moles KHP
Initial buret reading
1.42 mL 1.00 mL 1.25 mL
Final buret reading
19.40 mL 18.30 mL 18.45 mL
Volume NaOH used
17.98mL 17.30mL 17.20mL
Molarity NaOH
Average Molarity NaOH
Std. dev.
Percent relative std. dev.
Valdosta State University
Data
KHPmolKHPg
KHPmolKHPg 00212.0
23.204
1433.0
Valdosta State University
DataTrial 1 Trial 2 Trial 3
Mass KHP 0.433g 0.409g 0.406g
Moles KHP 0.00212 mol 0.00200 mol 0.00199 mol
Initial buret reading
1.42 mL 1.00 mL 1.25 mL
Final buret reading
19.40 mL 18.30 mL 18.45 mL
Volume NaOH used
17.98mL 17.30mL 17.20mL
Molarity NaOH
Average Molarity NaOH
Std. dev.
Percent relative std. dev.
Valdosta State University
Data
KHPmolKHPg
KHPmolKHPg 00212.0
23.204
1433.0
NaOHmolKHPmol
NaOHmolKHPmol 00212.0
1
100212.0
Valdosta State University
Data
KHPmolKHPg
KHPmolKHPg 00212.0
23.204
1433.0
NaOHmolKHPmol
NaOHmolKHPmol 00212.0
1
100212.0
MsolutionNaOHL
NaOHmol
solutionNaOHL
NaOHmolMolarity 109.0
01798.0
00212.0
Valdosta State University
DataTrial 1 Trial 2 Trial 3
Mass KHP 0.433g 0.409g 0.406g
Moles KHP 0.00212 mol 0.00200 mol 0.00199 mol
Initial buret reading
1.42 mL 1.00 mL 1.25 mL
Final buret reading
19.40 mL 18.30 mL 18.45 mL
Volume NaOH used
17.98mL 17.30mL 17.20mL
Molarity NaOH 0.109M 0.116M 0.116M
Average Molarity NaOH
Std. dev.
Percent relative std. dev.
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Data
100
116.0
109.0116.0%
agreement
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Data
%03.6
100116.0
109.0116.0%
agreement
Valdosta State University
Data
Trial 1 Trial 2 Trial 3 Trial 4
Mass KHP 0.433 0.409 0.406 0.449
Moles KHP 0.00212 mol 0.00200 mol 0.00199 mol
Initial buret reading
1.42 mL 1.00 mL 1.25 mL 18.45 mL
Final buret reading
19.40 mL 18.30 mL 18.45 mL 37.30 mL
Volume NaOH used
17.98mL 17.30mL 17.20mL
Molarity NaOH 0.109M 0.116M 0.116M
Average Molarity NaOH
Std. dev.
Percent relative std. dev.
Valdosta State University
Data
Trial 1 Trial 2 Trial 3 Trial 4
Mass KHP 0.433g 0.409g 0.406g 0.449g
Moles KHP 0.00212 mol 0.00200 mol 0.00199 mol 0.00220
Initial buret reading
1.42 mL 1.00 mL 1.25 mL 18.45 mL
Final buret reading
19.40 mL 18.30 mL 18.45 mL 37.30 mL
Volume NaOH used
17.98mL 17.30mL 17.20mL 18.85mL
Molarity NaOH 0.109M 0.116M 0.116M 0.117M
Average Molarity NaOH
Std. dev.
Percent relative std. dev.
Valdosta State University
Data
Trial 1 Trial 2 Trial 3 Trial 4
Mass KHP 0.433g 0.409g 0.406g 0.449g
Moles KHP 0.00212 mol 0.00200 mol 0.00199 mol 0.00220
Initial buret reading
1.42 mL 1.00 mL 1.25 mL 18.45 mL
Final buret reading
19.40 mL 18.30 mL 18.45 mL 37.30 mL
Volume NaOH used
17.98mL 17.30mL 17.20mL 18.85mL
Molarity NaOH 0.109M 0.116M 0.116M 0.117M
Average Molarity NaOH
0.116M
Std. dev.
Percent relative std. dev.
Valdosta State University
Data
100
117.0
116.0117.0%
agreement
Valdosta State University
Data
%855.0
100117.0
116.0117.0%
agreement
Valdosta State University
Data
00071.013
001.00)0(
1DeviationStandard
222
1
2
n
xxn
ii
Valdosta State University
Data
%61.0
100116.0
00071.0
100DeviationStandard
Dev.Std. RelativePercent
x
Valdosta State University
IMPORTANT REMINDER
• Label NaOH bottle with your name, solution concentration and section number.
• Save the unused solution in a location identified by your laboratory instructor.
Valdosta State University
Valdosta State University
Safety
• The NaOH solutions are corrosive. If you get some on your skin, wash with water for at least five minutes. If any NaOH solution gets in the eyes IMMEDIATELY wash with water for at least fifteen minutes. Call for medical assistance!
Valdosta State University
Valdosta State University
Waste Disposal
All wastes from this experiment can be flushed down the drain with plenty of running water, except your unused NaOH.
Valdosta State University