CHEM 210 Final

if the p-value is greater than 0.1, we generally conclude the data are consistent with the null hypothesis - correct answer true what is the best way to characterize the random error present in a measurement? - correct answer take replicate measurements of your analytes and using the standard deviation and a t-table specify an error bar with a confidence limit statistical interference assesses whether an observed phenomenon in the data can reasonably be attributed to chance or not - correct answer true 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? - correct answer (1) the standard error would decrease, (2) the margin of error would decrease in designing a clinical trial where each subject receives both a placebo and a proposed treatment, what statistical test would be most appropriate? - correct answer paired t-test 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? - correct answer 437 ppm 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? - correct answer 200 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? - correct answer 7.49 ug/mL 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? - correct answer 100 ug/mL solution: (1/2)^5 x 3200 = 100 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. - correct answer 0.4% 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. - correct answer true how many liters of a 2 M Ba(OH)2 are needed to titrate a 4 L solution of 6 M H3PO4? - correct answer 18 L solution: (4 x X) = (4 x 18) the charge balance equation for a solution containing H2O, H+, OH-, Ca2+, K+, C2H5OH, CrO4(2-), and Cl- is: - correct answer [H+] + 2[Ca2+] + [K+] = [OH-] + [Cl-] + 2[CrO4(2-)] what is the [H3O+] of a 2 M aqueous solution of a weak acid HXO2 with Ka = 3.2 x 10^-5? - correct answer 8.0 x 10^-3 M 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? - correct answer -1 which of the following is NOT a characteristic of an amphoteric species? - correct answer amphoteric species are always nonpolar all of the following are TRUE for activities and activity coefficients, except... - correct answer as ionic strength increases, the value of the activity coefficient increases 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? - correct answer 6.96 solution: (1/2) x (4.25 + 9.67) 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) - correct answer 11.55 the amino acid valine has pKa1 = 2.29 and pKa2 = 9.72. what is the principal species at 6.00? - correct answer HA- the titration solution consists of essentially pure weak acid... - correct answer at the equivalence point of a weak acid/strong base titration find the pH of a solution prepared by dissolving 0.800 g of potassium hydrogen malonate (C3H3KO4, FM = 142.152 g/mol) and 1.50 g of dipotassium malonate (C3H2K2O4, FM = 180.242 g/mol) in 100 mL water. for malonic acid, pka1 = 2.847, pKa2 = 5.696. - correct answer 5.87 a solution is prepared with an unknown concentration of a theoretical compound with a Ka of exactly 1.0. what is the pH of this solution? - correct answer less than 7 the mass balance equation for F- in a 0.02 M aqueous solution of KF is... - correct answer [HF] + [F-] = 0.02 M what is the approximate pH of 1.2 x 10^-5 M aqueous solution of NaOH? - correct answer 9.08 the function of a buffer is to... - correct answer resist changes in pH when small amounts of acid and bases are added calculate the pH of a solution when 15.00 mL of 0.100 M NaOH is added to 30.00 mL of 0.150 M weak acid, HA. Ka = 4.75 x 10^-6 - correct answer 5.02