1.) In Experiment 1: Melting point and IR, a student measured the spectra below

Question

1.) In Experiment 1: Melting point and IR, a student measured the spectra below with their unknown sample. The melting point was 68-70 C. From your list of choices in Table 1.1 of your lab manual, what is the identity of the unknown? 2.) During Experiment 2: Recrystallization, a student performed the solubility test and determined that heptane was the suitable solvent for their unknown. After the unknown was recrystallized, the student filtered the unknown and washed the filter cake with ethanol. What do you think would happen to the percent yield of the unknown? .) During Experiment 3: Acid/Base Extraction, two aqueous bases were used. What would happen to your experiment if only sodium hydroxide was used during the extraction? 4.) Calculate the volume of 6M HCl you would need to neutralize 20mL of 1.25M sodium carbonate. 5.) Benzoic acid has a pKa of 4.2. Will benzoic acid dissolve

Explanation / Answer

4) Given that the molarity of HCl, M1 = 6 M = 6 mole/L

Volume of HCl, V1 = ?

Molarity of sodium carbonate, M2 = 1.25 M = 1.25 mole/L

Volume of sodium carbonate, V2 = 20 mL = 0.02 L

We know that M1V1 = M2V2

V1 = (1.25 mol/L)x(0.02 L)/(6 mole/L) = 0.00416 L = 4.16 mL

Volume of 6 M HCl needed to neutralize 20 mL of 1.25 M sodium carbonate is 4.16 mL.

5) Benzoic acid with a pKa of 4.2 is insoluble in water. Benzoic acid will not dissolve in an aqueous solution if the pH is 5.

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