Instructions 1. Re-read experiment 10 in your lab manual. 2. Read the following
ID: 879095 • Letter: I
Question
Instructions 1. Re-read experiment 10 in your lab manual. 2. Read the following scenario. 3. Using the data given in the scenario and the attached titration curve, complete and show any 4. Using the data and results for the scenario, identify the unknown acid from the table given on 5. On a separate sheet of paper, neatly and legibly write a conclusion paragraph that identifies necessary calculations in the space provided on the back of this sheet the back of this sheet. your unknown acid and clearly explains how you used your data and results to identify your how you excluded other possible compounds. It should not include calculations and it should not include lab procedures. Remember that a well-supported conclusion should compound. This paragraph should repeat important results/data for your unknown and discuss include the following .An introductory sentence that explains what you were trying to accomplish and how you achieved it. One or two sentences that describe how one data point for your unknown was used to narrow down the list of possible acids. These sentences should give the experimental value for the unknown as well as the names and accepted values for the possible acids that have made it to the-short list" of compounds to consider. You may report 96 differences if you choose to do so, but it is not mandatory in most cases. One or two sentences that describe how you used each subsequent experimental value for your unknown to identify it. You should report the value and describe how it compares to the accepted values for the possible acids from your "short list." Make sure you give those accepted values. You may report 96 differences if you choose to do so, but it is not mandatory in most cases. You should always use and discuss all relevant experimental data to which you have . access in your conclusion. .A conclusion sentence that clearly identifies your unknown. 6. I should be able to read this paragraph without looking at any other part of the assignment and be convinced that your conclusion is correct Scenario: A student titrated a 0.576 g sample of an unknown acid using 0.100 M NaOH. The following titration curve was generated using data from the titration. Using this information, i the unknown acid from the table of possible unknown acids. (Note: This acid is NOT necessarily the same as the one you used in experiment 10.)Explanation / Answer
Solution :-
Volume of NaOH used to reach the equivalence point = 60.0 ml = 0.060 L
Molarity of NaOH = 0.100 M
Need to calculate the moles of the NaOH using its molairty and volume
Moles of NaOH = molarity * volume in liter
= 0.100 mol per L * 0.060 L
Moles of NaOH = 0.006 moles
From the titration curve we get the idea that acid is the monoprotic acid
Therefore the moles of the acid titrated are same moles of NaOH
So moles of acid at equivalence point = 0.006 mol acid
Now we know the mass of the acid used and we also know the moles of the acid , therefore lets calculate molar mass of the acid using the moles and mass
Molar mass = mass in gram / moles
Molar mass of acid = 0.576 g / 0.006 mol = 96 g per mol
Therefore the possible acid with this molar mass is chloroacetic acid. Also the pka value of the chloroacetic acid is 2.85
In the titriation at the half equivalence point pH = pka
In the titration curve pH is around 2.9 when 30.0 ml NaOH was used this means the pH at half equivalence point was around 2.9 that means pka of the acid is around 2.9.
This factor also matches with the chloroacetic acid therefore the acid used in the titration was the chloroacetic acid.