Title: Acid Base TitrationAurel Lazar
Introduction:
Titration is a process by which a certain compound is poured slowly into another to determine a point of neutralization. Most often, titration is used to find the point where a base just counteracts an acid so that there are no excess H+ ions in a solution. This can in turn be used to determine the concentration of a solution, provided the titrant was standardized prior to experimentation. A base (NaOH) was standardized against KHP, and using its known concentration was used to determine the molarity and eventual GFM.
Data: Qualitative
When the solution was mostly acidic, the indicator color made it appear clear, however, the instance it became more basic than acid, the solution became a clear pink.
Data: Quantitative:
Sample 1 / Sample 2 / Sample 3Mass of KHP (g) / .17 / .18 / .18
Initial NaOH reading (mL) / 0 / 7.75 / 16.78
Final NaOH reading (mL) / 9.70 / 16.78 / 25.72
Volume of NaOH (mL) / 9.70 / 9.03 / 8.94
Moles of KHP / 0.000832 / 0.000881 / 0.000881
Molarity of NaOH (M) / 0.0858 / 0.0975 / 0.0985
Mean Molarity of NaOH (M) / 0.0939
Mass of unknown (g)
Initial NaOH reading (mL)
Final NaOH reading (mL)
Volume of NaOH (mL)
Moles of NaOH
GFM of unknown solid (g)
Mean GFM (g/mol)
Calculations:
Data/Statistics
GFM / Deviance49.33 / 10.104 / Thrown Out / Initial Data:
50.54 / 8.894 / Thrown Out / Average / 61.81415
55.2978 / 4.136 / Thrown Out / Deviation / 4.914756
57.184 / 2.5 Deviations / 12.28689
57.32
57.407
57.429 / Statistics
57.4349 / Deviation / 1.536913
57.67 / 2.5 Deviations / 3.842282
57.89 / Average / 59.4348
58.35
58.41
58.9836
59.018
59.2748
59.375
59.566
60.227
61.2041
61.257
61.3781
61.897
61.92
62.18
62.19
64.4508 / 5.016 / Thrown Out
65.24 / 5.805 / Thrown Out
66.042 / 6.607 / Thrown Out
67.95 / 8.515 / Thrown Out
68.94 / 9.505 / Thrown Out
71.103 / 11.668 / Thrown Out
74.161 / 14.726 / Thrown Out
74.967 / 15.532 / Thrown Out
86.094 / 26.659 / Thrown Out
Statistical Analysis was conducted on the multiple GFMs to conclude which ones were valid and which were not, leading to the throwing out of a lot of data, the moving of the average closer to the accepted value.
Chemical Equations:
KC8H5O4 (s) + NaOH (aq) NaKC8H4O4 (aq) + H2O (l)
(Assuming KHP is a monoprotic donor)
Discussion: General
Discussion: Error
Conclusion:
Questions:
Questions:
Pre lab:
1. KC8H5O4: (39.098) + 8(12.01) + 5(1.008) + 4(15.99) = 204.178 g/mol. KHP has a tetrahedral structure.
2. An acid base indicator is a chemical compound that can be added to solutions in order to differentiate the pH of the substance. The indicator usually causes a change of color in the solution once the pH has been altered.
3. 0.4538/204.2= 0.00222
0.00222/.04412 = .05037 M
Post lab:
2. Bases such as NaOH are able to easily strip the hydrogen ion from monoprotic acids such as NaHSO4. Such acids when placed in aqueous solutions can separate from the hydrogen ion making it easy for the NaOH to absorb the hydrogen ion.
3. The equivalence point occurs when equal amounts of acidic and basic substances have reacted. The end point on the other hand represents when a dramatic change in pH occurs. The end point is often signified by a color change in the solution due to a presence of an indicator. The equivalence point on the other hand, identifies the solution as being perfectly neutral due to a balance in acidic and basic substances
pre lab:
1. calc molar mass of KHP and describe structure
2. define aid base indicator
3. if .4358 g of KHP requires 44.12 mL of NaOH to reach endpoint whats the molarity of NaOH
post lab:
1.commerical vinegar is 5 plus or minus .5% acetic acid by weight. assume this to be the true value for your unkown by how much were you in erorr in your analysis
2. why do monorportic acidic salts behave as strong enough acids to be titratable with NaOH using phen. as indicator
3. whats the diff btw endpoint for a titration analysis and true equivalence point for titration
General:
At room temperature of about 25° C, the pH of KHP is about 4, meaning the substance is acidic. The addition of NaOH causes an acid-base reaction to take place in the beaker. As Brownstead Lowry stated, the acid acts as a proton donor to the NaOH. The addition of the NaOH also makes the substance basic, which is supported by the change in color caused by the pH indicator. The indicator signifies the endpoint of the substance, which indicates when there is an equal amount of acidic and basic solution in the mixture. The equivalence point indicates when the substance has become neutral; however, the phenolphthalein is not able to indicate when this point is reached but instead indicates the endpoint of the mixture.
Error Analysis:
The phenolphthalein could have been contaminated causing it to miss the endpoint of the reaction. The KHP may also have reacted with the air during massing causing contamination in the solid before the solution was created. In addition, since the lab simply required calculating the endpoint, perhaps an excess of NaOH was used since the end point does not necessarily occur at the exact moment as the equivalence point. By adding NaOH till the end point was reached, perhaps more NaOH was used then was necessary, which would effect the molar mass of the unknown substance. If the appropriate amount of NaOH was supposed to be less than what was actually used, the denominator in the final equation would be smaller; thereby, increasing the molar mass.
Conclusion: The molar mass of an unknown substance can be determined through the grams of substance, concentration of the titrant, and the volume used to titrate the unknown substance. The average molar mass for my three trials was 60.0043 g/mol compared to the class average of 59.2435 g/mol. This experiment demonstrated another way to discover the molar mass of an unknown substance through the chemical process of titration.