CHEMISTRY 133

Spring, 2017 Homework Set 1

Only Problems in Bold are Submitted for Grading

Set 1.1 - Complete for quiz on Feb. 2

From Rubinson and Rubinson:  6.1, 6.2, 6.3, 6.5, 6.6, 6.7 [not collected]

Homework Solutions to Set1.1 Text Problems

Go to SacCT for solutions

Homework Set 1.2

Complete for quiz on Feb. 16

R&R Problems:  17.2, 17.3, 17.4

Solutions to Set 1.2 non-collected problems

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

(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.

1.2.2.  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.  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.

1.2.4.  Convert the following numbers between binary and decimal (a and b to decimal, c and d to binary):

a) 100011              b) 1000100            c) 37                            d) 103

1.2.5

1.2.7.  A CO monitor with an analog signal of 0.050 V/ppm put is placed in a parking garage.  It is desired to be able to record "normal" garage air (concentration ranging between 1 and 10 ppm) as well as to measure high concentration periods when cars drive by (up to 100 ppm).  An analog to digital converter with 10 bits with an input range of 0 to 10V is used (0 corresponding to 10 0's and 10 corresponding to 10 1's).

a)      Calculate the voltage from the monitor and corresponding decimal and binary numbers from the digitizer given a CO concentration of 8.20 ppm.

b)      What is the maximum CO concentration that can be recorded (without exceeding the A/D board's limit)?

c)      It is desired to be able to record concentrations as low as 1 ppm with a relative uncertainty of 5% or less.  What is the minimum number of bits needed to accomplish this?

Homework Set 1.3

Complete by Mar. 2 (but no quiz planned)

Note: Not collecting ANY problems from this set

Solutions are here: link (for pdf)

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

1.3.2.  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.

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

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

R&R 6.13

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?

Harris Text: Ch. 13:    1, 5, 10, 16, 19, 28, 36