CHEM 109
Introduction to Chemistry
Fall 2016
Problem Set 15
Reading for Today
Introduction to Chemical Principles Chapter 5.5, 5.9
Reading for Next Thursday
Introduction to Chemical Principles Chapter 5.6 - 5.9
Practice Problems
Chapter 5: 29, 30.
Additional Problems
1.
What was the major technical development required before Crooke’s Tubes could be
effectively constructed? Who made this technical break-through and what year did this
happen?
2.
What evidence do we have that Cathode Rays originate at the Cathode of a Crooke’s Tube
and are directed at the Anode?
3.
The deflection of a Cathode Ray can be calculated from the following relationship:
Deflection =
Approximate values for Each of these quantities are:
Force on Particle ~ 10-16 N
Dist. Over Which Force Acts ~ 0.05 m
Dist. of Drift ~ 1 m
Mass of Particle ~ 9 x 10-31 kg
Velocity ~ 3 x 107 m/s
a) Calculate the deflection for this case.
b) Suppose a beam of protons is directed through the same apparatus and that the force on
the beam is the same as that on the cathode ray in the example. What is the deflection
of the beam of protons? Is this result problematic? Explain.
4.
Thomson’s average value for the mass/charge ratio of the electron, using the deflected
cathode rays, was 1.3 x 10-11 kg/C. What is the percentage error in this result? (You will
need to look-up the currently accepted values of the electron’s mass and charge.)
5.
Suppose electrons always occurred in nature in pairs. Would Millikan have been able to
determine the charge of the electron using his experiment? Explain.
6.
What would you expect to happen to the oil drops in Millikan’s experiment if the charges
on the metal plates in his apparatus were reversed?