Electrochemistry and Electrolysis

Chapter 25: 4-9 Homework

• Reading Preparation
• WebLecture
• Study Activity
• Preparation work for chat
• Online Quiz
• Lab Instructions

Reading Preparation

Textbook assignment: Read Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 25: 4-9.

Study Notes

• 25.4 Nuclear decay rates are used to characterize decay activity. If we start with N₀ nuclei in which ΔN nuclei experience a disintegration in time t, the rate depends on the total nuclei we have to start:
  ΔN/Δt - -kN, or ln (N/N₀) = -kt.

  Here k is the decay rate of the isotope involved.

  If half the nuclei have decayed in time t, this half-life t_½ = 0.693/k.

• 25.5 Most of the several thousand unstable isotopes known today are actually artifically produced during nuclei bombardment in accelerators; they do not occur in nature. All elements beyond uranium-92 are also artificial.
• 25.6 In nuclear fission, the nucleus is split into major fraction parts (not alpha ejection) by bombarding it with neutrons. This reaction will itself produce free, high energy neutrons that bombard other nuclei, creating a chain reaction that ends only when the number of available nuclei becomes too small to sustain the reaction. Nuclear fission power plants supply much of the electrical power in Europe.
• 25.7 Nuclear fusion, the combination of nuclei with free protons or neutrons to form new elements and isotopes, requires high temperatures and pressures such as those in the cores of stars. Current human technology has not been able to control fusion reactions for practical use.
• 25.8 Nuclear decay radiation is extremely dangerous to cell structure in living organisms of any kind. Measuring radiation in Curies (Ci) and Bequerel (Bq) and energy absorbed in rads is used to determine the level of exposure from radioactive sources, and the likelihood of tissue damage.
• 25.9 In some circumstances, low levels of radioactive substances can be used as tracers to monitor chemical processes in tissues. Patient dosages are too small to cause damage, but technicians must employ safety practices to limit total cumulative exposure.

Read the following weblecture before chat: Decay Rates

Study Activity

Chat Preparation Activities

• Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
• Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

Chapter Quiz

• Required: Complete the Mastery exercise with a passing score of 85% or better.
• Go to the Moodle and take the quiz for this chapter.

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There is no lab for this chapter.

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