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 34):
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
Additional 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
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 wellrepresented. (The third assumption allows you to avoid using tfactors 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?
Harris Text: Ch. 13: 1, 5, 10, 16, 19, 28, 36 [THESE ARE POSTPONED]