CHEM 210 Final Exam Verified Questions and Answers

CHEM 210 Final Exam Verified Questions and Answers CHEM 210 Final Exam Verified Questions and Answers CHEM 210 Final Exam Verified Questions and Answers 1. if the p-value is greater than 0.1, we generally conclude the data are consis- tent with the null hypothesis: true 2. what is the best way to characterize the random error present in a mea- surement?: take replicate measurements of your analytes and using the standard deviation and a t-table specify an error bar with a confidence limit 3. statistical interference assesses whether an observed phenomenon in the data can reasonably be attributed to chance or not: true 4. suppose we collected a sample size n = 100 from some population and used the data to calculate a 95% confidence interval for the population mean. now suppose we are going to increase the sample size to n = 300. keeping all else constant, which of the following would we expect to occur as a result of increasing the sample size?: (1) the standard error would decrease, (2) the margin of error would decrease 5. in designing a clinical trial where each subject receives both a placebo and a proposed treatment, what statistical test would be most appropriate?: paired t-test 6. an atomic absorption analysis is to be done on the calcium in a sample of powdered milk. a 12.55 gram sample of the powder is wet ashed in nitric acid and diluted to 50.00 mL with distilled water. a 1.00 mL aliquot of this is transferred to a 50.00 mL solution using EDTA. using a wavelength of 422.6 nm in an atomic absorption experiment, this diluted sample showed an absorbance of 0.375. a standard calcium sample (treated the same way) with a known concentration of 20.0 ppm provided an absorbance of 0.859. what is the ppm of calcium in the powdered milk?: 437 ppm 7. in a 3 step serial dilution: the first dilution is 1/10, the second dilution is 1/5, and the third dilution is 1/4. what is the total dilution factor of this 3 step serial dilution procedure?: 200 8. a solution was prepared by mixing 10.00 mL of unknown (X) with 5.00 mL of standard (S) containing 8.24 ug/mL and diluting the mixture to 50.0 mL. the measured signal areas from an atomic absorption spectrometer of X:S was 1.690:1.000. in a separate experiment in which the concentrations of X and S were equal, the measured signal areas of X:S was 0.930:1.000. the concentration of X in the unknown is?: 7.49 ug/Ml 9. you set up a 10 tube Minimum Inhibitory Concentration test where the concentration of the antibiotic in each tube is a 1:2 dilution of the previous tube. if the concentration of the antibiotic tube 1 is 3200 ug/mL, what is the concentration of the antibiotic in tube 6?: 100 ug/mL solution: (1/2)^5 x 3200 = 100 10. to measure the Ca in breakfast cereal, 0.561 g of crushed Cheerios was digested at 600*C in air for 2 hours. the residue was dissolved in 6 M HCl, quantitatively transferred to a volumetric flask and dilution to 100.0 mL. then 5.00-mL aliquots were transferred to 50.0-mL volumetric flasks. each was treated with standard Ca2+ ion solution (20.0 ppm), diluted to volume with H2O, and analyzed by flame atomic absorption. a graph was constructed from the readings. use this graph to determine the wt% Ca in Cheerios.: 0.4% 11. the pH of the titration solution at the equivalence point is 9.45. this is consistent with titration of a weak acid with strong base.: true 12. how many liters of a 2 M Ba(OH)2 are needed to titrate a 4 L solution of 6 M H3PO4?: 18 L solution: (4 x X) = (4 x 18) 13. the charge balance equation for a solution containing H2O, H+, OH-, Ca2+, K+, C2H5OH, CrO4(2-), and Cl- is:: [H+] + 2[Ca2+] + [K+] = [OH-] + [Cl-] + 2[CrO4(2-)] 14. what is the [H3O+] of a 2 M aqueous solution of a weak acid HXO2 with Ka = 3.2 x 10^-5?: 8.0 x 10^-3 M 15. glutamic acid is an amino acid consisting of 2 carboxylic acid functional groups and an amine functional group. pKas are listed as 2.19, 4.25, and 9.67. at pH 7, the charge on the glutamic molecule is?: -1 16. which of the following is NOT a characteristic of an amphoteric species?- : amphoteric species are always nonpolar 17. all of the following are TRUE for activities and activity coefficients, ex- cept...: as ionic strength increases, the value of the activity coefficient increases 18. glutamic acid is an amino acid consisting of 2 carboxylic acid functional groups and an amine functional group. pkas are listed as 2.19, 4.25, and 9.67. the approximate pH of 0.025 M HL- is?: 6.96 solution: (1/2) x (4.25 + 9.67) 19. what is the pH of a solution with an ammonium concentration of 70 mM and an ammonia concentration of 712 mM? (pKb of ammonia is 3.45): 11.55 20. the amino acid valine has pKa1 = 2.29 and pKa2 = 9.72. what is the principal species at 6.00?: HA-