CHEMISTRY 133

Spring, 2014 Homework Set 1

Only Problems in Bold are Submitted for Grading

Set 1.1 - Complete for quiz on Feb. 6

 

Statistics Calculations (See Chem. 133 Lab Manual pages 3-4):

1.  Download the file HW11.txt. (this gives the time in minutes and the signal in fluorescence units) and transfer to an Excel File.  Print a table from Excel showing two columns collected over the first 30 s period.

 

2.  Make a plot of the raw data from above and also data processed with a 2 s moving average over both the first 30 s and over the first 4 min.  This can be done by either using Excel's Plotting routines or by creating a 2 s moving average using a new column in Excel.

 

3.  Given the following data, determine the concentration of chloride in an unknown and the standard deviation in its concentration.

Calibration Data......................................................... Unknown Data

Cl Conc.

Peak Area

Cl Conc.

 

mg/mL

 

mg/mL

Peak Area

2

0.4516

unknown

9.2133

10

2.4344

 

 

20

5.3388

 

50

15.4836

 

Statistical Calculations - SOLUTIONS (updated part 2. 2/11 10:30 since original answer used 1.2 s moving average)

 

From Rubinson and Rubinson:  6.1, 6.2, 6.3, 6.5, 6.6, 6.7

text problem solutions

Additional Problems:

PDF link to rest of problems

 

Solutions to other problems (circuit problems not in text)

 

 

 

Homework Set 1.2

Complete for quiz on Feb. 20

 

From Rubinson and Rubinson:  6.19

Additional Problems:  PDF link

 

  Solutions to graded problems

Homework Set 1.3

Complete by Feb. 27 (but no quiz planned)

 

From Rubinson and Rubinson:  6.13, 6.15

Additional Problems:

 

1.  Which type of noise is best reduced by shielding the critical electronics?

 

2.  An instrument measures the concentration of a compound in a river that varies on the order of minutes.  Most of the noise associated with the measurement occurs at frequencies greater than 1 Hz.  Suggest a method (analog or digital) to increase the signal to noise ratio.

 

3.  What type of noise can be reduced by using internal amplification in a transducer?

 

4.  What type of noise can be reduced by cooling electrical components?

 

5.  A sample is measured 12 times by a spectroscopic method.  The average concentration and standard deviation in the average are found to be 5.2+0.7 μM.  With the assumptions made below answer the following questions:

Assume: 1) noise is purely random, 2) the noise is defined as the standard deviation, and 3) that the standard deviation is well-represented.  (The third assumption allows you to avoid using t-factors in signal averaging)

a)  What signal to noise ratio would be expected in a single measurement?

b)  What is the signal to noise in the average value for the twelve measurements?

c)  A researcher needs to have the noise be less than 2% of the value in a particular experiment.  How many measurements should she make?

 

Solutions to problems  

 

Harris Text: Ch. 13:      1, 5, 10, 16, 19, 28, 36 [THESE ARE POSTPONED]