3. Calculate the percent yield if you started with 1.56 g of copper wire and recovered 0.88 g of copper. 4. What was the color of CuO?

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1 Quiz Study Guide CHEM 109 Copper, Titration, Kinetics, Equilibrium, Enzyme Kinetics, DNA I A. Review all prelab questions, reports and postlab questions. B. Work the sample questions. Remember that all possible types of questions may not be represented. SHOW ALL WORK! Remember to use proper s.f. and units. Chemistry of Copper Lab In general: Be able to identify the type of reaction, predict products, write correct formulas, and balance equations. You should know the colors of all the copper containing products. Review the experiment and your results. Make sure you understand each step that you performed. For example, why was reaction 1 performed in the hood? 1. Classify the reaction type and balance the following equation: Cu + O 2 CuO 2. Classify the reaction type, predict the products, balance the equation and write the net ionic equation for Cu (s) + AgNO 3 (aq) 3. Calculate the percent yield if you started with 1.56 g of copper wire and recovered 0.88 g of copper. 4. What was the color of CuO? Titration of Fake Vinegar In general: Be able to perform the four steps for the calculation of a titration. Review the experiment and your results. Know what was in the buret, what was in the titrating flask and in general how the titration was performed. 1. During a titration of a ml sample of acetic acid (CH 3COOH), the endpoint was reached after adding ml of M NaOH. A) Write a balanced equation for this titration B) How many moles of NaOH were added? C) How many moles of CH 3COOH were present in the sample? D) What was the concentration of the CH 3COOH in the sample? Kinetics: Review your experimental methods. Note that we looked at effects of reactant concentration and temperature on rate. There were some postlab questions that asked you to explain these effects based on collision theory. 1. Based on the following results for the reaction between reactants A and B: A + 2B C a) Kinetics experiment Concentration of Product C Produced at Various Times Trial Reactant 20. s 40. s 60. s 80. s 100. s A conc 1 20 mm 3.21 x x x x x mm 5.50 x x x x x 10 3 Calculate the rate of trial 1 based on the two points for 20 s and 80 s shown in the table above. b) Assuming the numerical value for the rate for trial 2 was 2.82 x 10 5, what can you say about the relationship between the rate of this reaction and the concentration of reactant A? 2. For the reaction we studied: 6H + + IO 3 + 8I 3 I 3 + 3H 2O a) Which was the species used to follow the progress of the reaction? Why? b) Using Beer s Law (A = a b c) calc. the concentration, c, (in M) for a sample reading A 353 = (a = 26,400 cm 1 M 1, b = 1.08 cm)

2 3. Given the following plot of concentration of I 3 versus reaction time, determine the rate of the reaction. 1.80E04 Production of I 3 versus Time 1.60E E04 y = 1.48E06x E06 R 2 = 9.96E E E04 [I 3 ] 8.00E E E E E Time (s) 4. What is the concentration of I, if 7.50 ml of a M solution of KI was diluted to a final volume of ml? Equilibrium: Review all the equilibria studied. Remember that heating and cooling can affect an equilibrium. Do you remember what exothermic and endothermic mean? 1. Given the following equilibrium: 2CrO 4 + 2H + Cr 2O 7 + H 2O a) Adding sulfuric acid (H 2SO 4) to the yellow chromate solution (CrO 4 ) results in a persisting orange color; explain the observed change. b) Write the equilibrium constant expression in terms of concentration of reactants and products. 2. Given the following data for the equilibrium: Fe 3+ + SCN Fe(SCN) 2+ tube A 456 [Fe(SCN) 2+ ] Total [Fe 3+ ] Free [Fe 3+ ] Free [SCN ] K eq E E E E04 NA E06 5.0E05 4.8E E04 a) Write the expression for the equilibrium constant K eq b) Find the values for the equilibrium constant for tube 2. Enzyme Kinetics Given information: A = abc b = 1.08 cm a =10,300 M 1 cm 1 (for benzoq. ) A = abc Student data for enzymatic conversion of catechol to benzoquinone by catechol oxidase. A, Absorbance values for given time Rate Tube Catechol Conc. 30 s 60 s 90 s 120 s (M/s) 1 10 mm mm E mm, no enzyme E mm, boiled enzyme E mm, with inhibitor E08 1. For the 10 mm sample, calculate the concentration of benzoquinone for each of the four time points.

3 Rate (M/s) Reaction Rate (M/s) 2. Using the 30 s and 90 s data from the 10 mm catechol assay, calculate the approximate Rate (or [benzoquinone]/ t). Express your rate in [benzoquinone]/sec. 3. Calculate the relative % activity of your boiled enzyme. 4. Explain the results of question 3 in terms of protein structure. 5(a) Determine the maximum velocity of the enzyme from the graph. (b) At what catechol concentration was halfmaximal activity obtained? Show the lines on graph that help in this determination. Enzyme Activity vs Catechol Concentration 3.50E E E E E E E E Catechol Concentration (mm) 6. Using the data from the accompanying graph, approximately how long of a boiling time was required to reduce enzyme activity to 20% of its original value? Show the lines on graph that help in this determination. 3.5E07 3.0E07 2.5E07 2.0E07 1.5E07 1.0E07 5.0E08 0.0E+00 Effect of Boiling on Enzyme Activity Time (s) DNA I 1. You should be able to draw or interpret a pedigree (family tree), especially as related to hemophilia. For example: what shape is used to represent a female? A male? A individual affected by a disease? 2. What places in a cell contain DNA? In each case, from whom is that DNA inherited? 3. What disease did Alexei of the Romanovs suffer from? What kind of protein does not function properly in individuals with this disease? 4. You should be able to determine some aspects of family relationships by comparing sets of sequences. For example, the table below contains bases from specific regions of mitochondrial DNA from Fred Genetico and four other people. Which people shown do not share the same maternal ancestor with Fred (a grandmother of Fred s)? Explain. Comparing Bases Present in Particular Locations sample location 1 location 2 location 3 location 4 location 5 Fred T C C A T person 1 T C C A T person 2 T A G T C person 3 A G G C T person 4 T C C A T

4 Selected Answers! Chemistry of Copper Lab 1. Classify the type of reaction and balance the equation: Combination or synthesis 2 Cu + O 2 2 CuO 2. Classify the reaction, predict the products, balance the equation and write the net ionic equation for Single replacement Cu (s) + 2 AgNO 3 (aq) 2 Ag + Cu(NO 3) 2 (This reaction proceeds because copper is more active than silver.) NIE Cu (s) + 2 Ag + (aq) 2 Ag + Cu Calculate the percent yield if you started with 1.56 g of copper wire and recovered 0.88 g of copper x 100% = 56.4% rounds to 56% Titration of Fake Vinegar In general: Be able to perform the four steps for the calculation of a titration. Review the experiment and your results. Know what was in the buret, what was in the titrating flask and in general how the titration was performed. 1. During a titration of a ml sample of acetic acid (CH 3COOH), the endpoint was reached after adding ml of M NaOH. a) Write a balanced equation for this titration CH 3COOH + NaOH CH 3COO Na + + H 2O Note: ratio or reactants is 1:1. b) How many moles of NaOH were added? (0.100 moles/l )( ml) ( 1 L 1000 ml c) How many moles of CH 3COOH were present in the sample? mol NaOH) ( 1 mol acid 1 mol NaOH ) = mol, rounds to mol NaOH ) = mol, rounds to mol CH3COOH d) What was the concentration of the CH 3COOH in the sample? ( mol) / L = M, rounds to M CH 3COOH Kinetics: 1. Based on the following results for the reaction between reactants A and B: A + 2B C a) Calculate the rate of trial 1 based on the two points for 20 s and 80 s shown in the table above. Rate = (1.28 x x 10 4 ) / (80 s 20 s) = 1.6 x 10 5 M/s b) Assuming the numerical value for the rate for trial 2 was 2.82 x 10 5, what can you say about the relationship between the rate of this reaction and the concentration of reactant A? The difference between trial 1 and trial 2 is the concentration of reactant A. When the concentration increased (from 20 mm to 40 mm), the rate of the reaction increased as well (from 1.6 x 10 5 M/s to 2.82 x 10 5 M/s. 2. b) Using Beer s Law (A = a b c) calc. the concen., c, (in M) for a sample reading A 353 = 0.042

5 (a = cm 1 M 1, b = 1.08 cm) A = abc so c = A/(a x b) c = 0.042/ (26,400 x 1.08) = 1.5 x 10 6 M 4. What is the concentration of I, if 7.50 ml of a M solution of KI was diluted to a final volume of ml? Use M 1V 1= M 2V 2 Show work. Answer is M Equilibrium: 1. Given the following equilibrium: 2CrO 4 + 2H + Cr 2O 7 + H 2O a) Adding sulfuric acid (H 2SO 4) to the yellow chromate solution (CrO 4 ) results in a persisting orange color; explain the observed change. H 2SO 4 H + + HSO 4 This increases the concentration of H +. The collision rate between H + and CrO 4 increases. The rate of the forward reaction increases and the reaction shifts to the right. 2. Given the following data for the equilibrium: Fe 3+ + SCN Fe(SCN) 2+ a) Write the expression for the equilibrium constant K eq K eq = [Fe(SCN) 2+ ] / ([Fe 3+ ][SCN ]) b) Find the values for the equilibrium constant for tube 2. K eq = [1.97x10 6 ] / ([4.8x10 5 ][1.98x10 4 ]) = (or 2.1x10 2 ) Enzyme Kinetics 1. For the 10 mm sample, calculate the concentration of benzoquinone for each of the four time points. For the 30 s point, c =A/(ab) = 0.172/(10,300*1.08) = 1.55E05 M For the 90 s point, c =A/(ab) = 0.564/(10,300*1.08) = 5.07E05 M 2. Using the 30 s and 90 s data from the 10 mm catechol assay, calculate the approximate Rate (or [benzoquinone]/ t). Express your rate in [benzoquinone]/sec. Rate = (5.07E05 M 1.55E05 M)/(90 s 30 s) = 3.52E05 M/60 s = 5.87E07 M/s 3. Calculate the relative % activity of your boiled enzyme. Part/whole x100% 1.31E07/7.22E07 x 100% = 18.1% 4. Explain the results of question 3 in terms of protein structure. See answers to Enz. Kinetics postlab question Using the data from the accompanying graph, approximately how long of a boiling time was required to reduce enzyme activity to 20% of its original value? Show the lines on graph that help in this determination. Take the unboiled sample activity, 2.94E07 and find 20% of that value or 5.88E08. Locate that value on the yaxis and draw a horizontal line over to the graph line, then drop a vertical line to the xaxis and read the value. Should be ~14 seconds. DNA I 1. For example, what shape is used to represent a female? Circle 2. DNA is located in the nucleus and mitochondria.

6 3. What disease did Alexei of the Romanovs suffer from? hemophilia What kind of protein does not function properly in individuals with this disease? clotting factors 4. The table below contains bases from specific regions of mitochondrial DNA from Fred Genetico and four other people. Which people shown do not share the same maternal ancestor with Fred (a grandmother of Fred s)? Explain. Comparing Bases Present in Particular Locations sample location 1 location 2 location 3 location 4 location 5 Fred T C C A T person 1 T C C A T person 2 T A G T C person 3 A G G C T person 4 T C C A T Persons 2 and 3 are not related to Fred Genetico. Their sequence differs from his at 4 locations. It would be unlikely to have mutations at so many locations in a short stretch of mitochondrial DNA over a few generations time.