Question

i have no clue what amino acid this unknown is . maybe serine ?? pleade help! i also need to locate the eq points it can be from 1-3 points but atleasy 2 , the pka2 location , and the expermental molecular weight value. if you can label it on one of the graphs ( they are the same) the chocies are below ( it most likely will not be glycine ) .

other data:

unknown weight obtained was = .315g

the NaOh M= .4853

the formula given to us for molar mass = #g obtained / ( v2-v1) which is final eq point - first equivalant point , multipled by mol/L ( .4853M naoh)

P L M H pH vs NaOH 10 9.2 8.89 8.61 8.3 7.72 6.65 6.39 7.29 6.09 5.8 6.98 5.26- 5.55 4.97 4.68 4.4 4.05 3.61 2.78 2 3.07 2.46 2.17 1.83 1 0 10 12 en 10 7 6 품 5 4 10 12 14 4 Volume NaoH Below are theoretical molecul . The key to identifying the unknown will be the experimental molecular weight value, and also the number of oka values on the unknown titration curve. your unknown. However, the experimental pKa values may not help in identifying the unknown. This difficulty is because some pKa values for different amino acids are very close together. Also, this is because experimental pKa's in general (especially the higher pH pKa's) often have greater experimental error with our lab setup. Table of potential unknown amino acids: R group pK carboxy pK. amine MW (g/mole) Amino Acid pK 9.78 75.07 2.34 Glycine Alanine 89.09 2.35 9.87 13 105.09 2.21 Serine 9.15 (not alwaysdetected) Valine 117.15 2.29 9.72 Leucine 131.17 2.33 9.74 Histidine 155.16 1.80 9.33 6.05 This R-group deprotonates prior Note: in some text books, the values for the pKa's may be slightly different that to the amine group deprotenation the values given above. This could be because the values in other tables may be of different experimental conditions. Note: Use the above list for potential unknowns; do not use any other listing of AAs as your potential unknown amino acid.

Answer 1

According to graph,

First Equivalence point is occurred at pH value of 4.05 . Here, First reaction is completed.

Second Equivalence point is occurred at pH value of 8 . Here, Second reaction is completed.

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