The color change accompanying the reaction of phenolphthalein with strong base is illustrated below. The change in concentration of the dye can be followed by spectrophotometry (Section 4.9), and some data collected by that approach are given below. The initial concentrations were [phenolphthalein] = 0.0050 mol/L and [OH ‒ ] = 0.61 mol/L. (Data are taken from review materials for kinetics at chemed.chem.purdue.edu.) (For more details on this reaction see L Nicholson, Journal of Chemical Education, Vol. 66, p. 725, 1989.) (a) Plot the data above as [phenolphthalein] versus time, and determine the average rate from t = 0 to t = 15 seconds and from t = 100 seconds to t = 125 seconds. Does the rate change? If so, why? (b) Use a graphical method to determine the order of the reaction with respect to phenolphthalein. Write the rate law, and determine the rate constant. (c) What is the half-life for the reaction?
The color change accompanying the reaction of phenolphthalein with strong base is illustrated below. The change in concentration of the dye can be followed by spectrophotometry (Section 4.9), and some data collected by that approach are given below. The initial concentrations were [phenolphthalein] = 0.0050 mol/L and [OH ‒ ] = 0.61 mol/L. (Data are taken from review materials for kinetics at chemed.chem.purdue.edu.) (For more details on this reaction see L Nicholson, Journal of Chemical Education, Vol. 66, p. 725, 1989.) (a) Plot the data above as [phenolphthalein] versus time, and determine the average rate from t = 0 to t = 15 seconds and from t = 100 seconds to t = 125 seconds. Does the rate change? If so, why? (b) Use a graphical method to determine the order of the reaction with respect to phenolphthalein. Write the rate law, and determine the rate constant. (c) What is the half-life for the reaction?
Solution Summary: The author analyzes the graph plotted between [Phenolphthalein] and time. The average rate of a reaction is defined by the change in concentration of substrate or target (product).
The color change accompanying the reaction of phenolphthalein with strong base is illustrated below. The change in concentration of the dye can be followed by spectrophotometry (Section 4.9), and some data collected by that approach are given below. The initial concentrations were [phenolphthalein] = 0.0050 mol/L and [OH‒] = 0.61 mol/L. (Data are taken from review materials for kinetics at chemed.chem.purdue.edu.) (For more details on this reaction see L Nicholson, Journal of Chemical Education, Vol. 66, p. 725, 1989.)
(a) Plot the data above as [phenolphthalein] versus time, and determine the average rate from t = 0 to t = 15 seconds and from t = 100 seconds to t = 125 seconds. Does the rate change? If so, why?
(b) Use a graphical method to determine the order of the reaction with respect to phenolphthalein. Write the rate law, and determine the rate constant.
1) Draw the structures of D-lysine and L-lysine and assign R/S configuration
(showing your workings).
2) Draw the predominant ionisation forms of the free amino acid lysine, at pH 1.0,
8.0, and 11.0. pKa values: 2.2 (-COOH), 9.0 (α-NH3+), 10.5 (side-chain).
3) Calculate (showing your workings) the % of the different ionized species that
are present in a 1.00 M solution of L-proline at pH = 10.0. pKa values: 1.95 (-
COOH), 10.64 (α-NH3*).
4)
a) Draw the tripeptide Tyr-Pro-Lys once with a trans peptide bond between Tyr
and Pro and once with a cis peptide bond between Tyr and Pro.
b) The electrospray ionization mass spectrum (ESI-MS) of the tripeptide you
designed in part (a) shows peaks indicative of mono-protonation and di-
protonation of the tripeptide. At what values of m/z would these peaks be
expected (no fragmentation)? Briefly explain your answer (showing your
workings).
5) How could the sequence of Ala-Met-Thr be distinguished from that of Thr-Ala-
Met by tandem ESI-MS-MS?…
LABORATORY REPORT FORM
Part I. Determination of the Formula of a Known Hydrate
1. Mass of empty evaporating dish
3. Mass of hydrate
Using subtraction
or mass by difference,
find the mass of
the hydrate
76.96
-75.40
75.40g
76.968
1.568
01.56
76.90 g
2. Mass of evaporating dish + hydrate
4. Mass of evaporating dish + hydrate (after heating)
First 76.98 g
Third 76.66g
Second
Fourth (if necessary) 76.60g
5. Mass of anhydrate
6. Mass of water lost by the hydrate
7. Percent of water of hydration
(Show Calculations)
8. Moles of water
(Show Calculations)
mol
mass of water
=
MM of water (g/m)
9. Moles of anhydrate
(Show Calculations)
10. Ratio of moles of water to moles of anhydrate
11 F(Show Calculations)
11. Formula of hydrate
- Mass of water (g) x 100
% water hydration
g
g
%
Mass of hydrate (9) x IC
% = (Mass of hydrate- mass of an)
mass of hydrate (g)
% = (1.569-
× 100=
mol
1.569
mol Mol Mass of
anhydrate/MM
of anhydrate
12. What was the color of the hydrate?
blue
What was the color of the…
compared t-critical with t-calculated and 95% confidence interval to answer this question
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