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University of Florida  CHM 3120 Exam 1(Form Code A September 15, 2011  1)In Analytical Chemistry, we often use calibration curves

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CHM 3120 Exam 1(Form Code A September 15, 2011 
1)In Analytical Chemistry, we often use calibration curves. Which of the following statements is true concerning calibration curves? 
(A)    Calibration curves require a minimum of three points for accurate results   
(B)    The slope of a calibration curve is a measure of a method’s sensitivity   
(C)    The y-intercept must be close to zero for reliable results from a calibration curve (D) Straight line calibration curves (R2 >0.995) are required for accurate results 
 
2.    The salinity of the Great Salt Lake was measured to be 19 parts per thousand sodium            chloride.  Calculate the molarity of the sodium ion in the Great Salt Lake. 
(A) 0.82 molar  (B)0.46 molar   (C) 2.3 x 10-2   molar  (D) 3.2 x 10-1 molar  (E) other 
 
3.    I indicated some outstanding Analytical Chemistry programs and scholars. Which of the following      does not combine a program and individual from the lists? 
     (A)  Michigan; Bob Kennedy  (B) Illinois; Sam McCoy  (C) Texas; Jenny Broadbelt      (D) Florida; Weihong Tan    
 
4.    An analytical procedure required the preparation of a solution containing 100 ppm chromium. How                many grams of potassium dichromate (K2Cr2O7) would be required to prepare 500 mL of this            solution?    
           (A) 0.2829 grams   (B) 0.1415 grams  (C) 0.5658 grams  (D) 0.4231 grams  (E)   other  
 
5.    How many grams of ethanol (CH3CH2OH) are contained in 0.100 L of 1.71 M aqueous ethanol             solution? 
(A)8.39g   (B) 7.87g   (C) 3.91g  (D) 5.48g  (E) other 
 
6.    Which of the following could be considered a matrix effect? 
(A)    Sample constituents that react with the analyte 
(B)    Effect of temperature changes on analytical results 
(C)    Changes in instrument sensitivity for the analyte 
(D)    Incorrect use of Confidence Intervals 
 
7.    Write the answer to the following, using the correct number of significant figures; 
                   6.345 x  2.2 = 13.959 
(A) 13.9  (B) 14.0  (C) 13.96  (D) 14  (E) other      
 
8.    Which of the following is a weak acid? 
(A)    HF 
(B)    HCl  
(C)    HBr 
(D)    HI 
 
9.    An accepted value for the ATP concentration of a certain cell type is 111µmol/100mL. A new      method you are exploring for this sample gave values of 117, 119, 111, 115, and 120 µM/100mL.      What conclusion can you draw in comparing your results with the accepted value at the 95%      confidence level? 
     (A) difference is not significant  (B) difference is significant  (C) need more trial values to know      (D) 90% confidence level would change the conclusion                                  
 
10.    To extract Al from glass, 100 mL of EDTA were mixed with 0.50g of glass particles and allowed to             equilibrate over time.    If the glass contained 0.80 wt% Al and 0.35% of the Al was extracted                           by the EDTA, what was the Al concentration of the equilibrated EDTA solution? 
 
(A) 2.70µM   (B) 3.85µM  (C) 5.25 µM  (D) 1.05µM  (E) other 
 
11.    An standard  sample was prepared to contain 10.0 ppm of an analyte and 15 ppm of an internal          standard.  Signals obtained for this mixture were 0.155 (analyte) and 0.233 (internal standard).  An      analytical sample of unknown analyte concentration was prepared to contain 15.0 ppm of the      internal standard, for which signals were obtained of 0.274 (analyte) and 0.198 (internal standard).      What was the analyte concentration (ppm) in the sample?  
 
     (A) 15.0 (B)  10.1  (C) 13.5  (D) 20.8  (E) other      
 
12.    Which of the following statements about the Confidence Interval (CI) is false?   
(A)    We can be 95% confident the true mean lies within the calculated 95% CI. 
(B)    The CI at 50% confidence level is narrower than that at 90% 
(C)    The CI relates the true mean to the measured mean 
(D)    The CI broadens as n (number of measurements) increases 
 
13.    Apply the Q- test to each set of data below and indicate in each case whether the outlier should be      retained or not. 
     (i)  41.27, 41.61, 41.84, 41.70           (ii) 7.295, 7.284, 7.388, 7.292 
            (A) retain outlier in both  (B) reject outlier in both  
            (C) retain outlier in (i), not in (ii)   (D) reject outlier in (i), not in (ii)                
           
 
14.    For the method of Standard Additions, which of the following is not true: 
(A)    Requires a linear response to the analyte 
(B)    Corrects for instrument response that varies from sample to sample 
(C)    Known quantities of analyte are added to the unknown solution 
(D)    Multiple analyte additions at different concentrations are a better check on linearity 
 
15.    An unknown sample of dopamine gave a current of 34.6 nA in an electrochemical analysis. Then 2.00               mL of solution containing 0.015 6 M dopamine was mixed with 90.0 mL of unknown, and the              mixture was diluted to 100.0 mL in a volumetric flask.   The signal from the new solution was 58.4               nA. What is the dopamine concentration in the unknown sample?  
 
(A)  0.312 mM  (B)  0.396 mM  (C)  0.151 mM   (D) 0.200 mM    (E) other   
  
16.    Which of the following statements is true? 
(A)    reaction is favored if ΔG is positive.   
(B)    A negative ΔS favors a reaction.   
(C)    If Q>K, the reaction must proceed to the left to reach equilibrium 
(D)    A reaction is spontaneous if ΔGo is positive. 
 
17.    Which statement is false concerning the use of an internal standard? 
(A)    An internal standard helps compensate for temperature changes during an analysis. 
(B)    An internal standard helps compensate for possible sample losses in the analysis. 
(C)    An internal standard is a different substance from the analyte. 
(D)    An internal standard is added at higher concentrations than the analyte. 
 
18.    Calculate the solubility of Ba(IO3)2 in a solution containing 200 mL of 0.010M Ba(NO3)2 and 100 mL         of 0.10M NaIO3.  Ksp of Ba(IO3)2  = 1.57 x 10-9  
 
     (A) 3.93 x 10-6M  (B) 1.57 x 10-7M  (C)  7.85 x 10-8M  (D) 7.32 x 10-5  (E) other   
 
19.    Results from a series of standard solutions and their associated absorbance values are used to produce          by a least squares method the following straight line response:  y = 0.0163x + 0.0047, where x is in µg        of the analyte.  What is the value in µg of an unknown sample that shows an absorbance of 0.364?    
     The blank absorbance is 0.095.   
     (A) 10.1 µg  (B) 16.2 µg  (C) 8.1 µg  (D) 13.3 µg  (E)  other    
 
20.    How many grams of 0.49% wt% aqueous HF are required to provide a 25% excess to react with 25         mL of 0.023 M Th+4 by the reaction Th+4  +  4F-1  à  ThF4(s)  ?   
 
(A)  14.4 g  (B) 10.6 g   (C) 12.0 g   (D) 7.31 g  (E) other