CH 302 1st EditionExam 3 Study Guide: Lectures 15 - 21Lectures 15-16Nuclear ChemistryChernobyl-What Happened: April 26, 1986- Operator error – cooling water mistake- Explosion- 9 tons of nuclear material blown into sky 100 times normal background radiation- Was not a nuclear explosion- Chemical explosion occurredWhat is the difference between nuclear and chemical changes?- Compare energy release upon change- Compare what is conserved across the change- Types of change and how to recognize type of changeChemical Change:- Atoms rearrange- Atomic identity does not changeNuclear Change:- Mass is not conserved - Nuclear changes- Change in atomic identity is likely to occur- Matter is converted to energy- Energy can be converted into matter Fission Reactions:- Nucleus splits up- Number of protons are conserved- Neutrons are conserved- Chain reaction occurs- Neutrons are conservedHow does fission produce energy?- Products have lower energy- Real mass of reactants and products- Mass is lostWhat is fusion?- When nuclei fuse together - Examples are the sun and starsBeta Decay:- If a problem says beta, assume its negative (or an electron)- There are two types of beta though, a positron (positive beta) and an electron (negative beta)Band of Stability:- The further away something is from the band of stability, the less stable it is and the smaller its half life is- Band of stability plots neutrons vs protons- Isotopes want to get to a stable state so they will go through the process of alpha decay, positron, etc to reach that stable stateWorksheet:1. Write a balanced nuclear equation for the alpha decay of Po-210.210Po → 4He + 206Pb2. Experiment involving each student flipping a coin (heads = standing, tails = sitting)Interpreting the Graph:- Not linear- No constant slope- The first event shows the most Po losto There was the most Po at this time, sowhen you have the most to begin with you also have the most to lose - The Po initially and finally is related - As the change in number of Po goes down, the amount of Pb increases by that same amountHalf Life Questions:1. Imagine we started with 96 student isotopes. How many 1⁄2 lives would have to pass to get to 6 student isotopes left?4 events because…96/2 =4848/2 = 2424/2 = 1212/2 = 62. If you had 960 student isotopes, how many 1⁄2 lives would have to pass to get 60 student isotopes left?4 events because… 960/2 = 480480/2 = 240240/2 = 120120/2 = 603. P-32 has a half-life of 14 days. After 3 months what would be the residual radioactivity of1 millicurie of ATP labeled with P-32?15.625 microcuries because 3 months is about 6 half lives. Types of Nuclear Changes:- Fission Reactionso Nucleus splits into smaller masseso Big tiny + tinyo Nuclide larger and much more heavyo Releases energy- Fusion Reactionso Nucleus combines into a larger mass o Tiny + tiny big o Light to heavy, they fuse together o Releases energy- Decay Reactionso Big big + tinyo Happens spontaneouslyo Natural occurrenceo Usually left off of balanced equation since it has no mass and no charge (just electromagnetic radiation)- Transmutationo NOT spontaneouso Bombarded with alpha particleso Need particle acceleratoro Used in medicine and cancer researchChemical Change vs. Nuclear Change:- Nuclear changes conserve mass numbers- Atomic numbers are conserved on the right and left hand side of the reactionBinding Energy:- This is where energy comes from- Analogous to the breaking and forming of bonds in change of enthalpy- E = mc^2- Difference in masses = mIsotopic Stability:- Fusion: Bigger charges in energyo High energyo Wants to go down in energyo Exothermico Much better way to produce energy- Decay Fissiono Exothermico Wants to go to the lowest energy state (which is the element iron)Ionizing Radiation:- Alpha radiation: positive and massiveo Harmful inside the bodyo Bare helium nucleus will rip electrons off moleculeso Ionization of biomolecules are very unhealthyo Generally not harmful as they are absorbed by the outer layer of dead skin- Beta radiation: negative and low mass- Gamma radiation: uncharged and no mass- Radiation comes from unstable radioisotopeso Naturally found in the environmento Made by humans for medical, energy, defense purposes- Isotopic Stability depends on neutron to proton ratioLectures 17Rate of DecayBeta Decay:- If a problem says beta, assume its negative (or an electron)- There are two types of beta though, a positron (positive beta) and an electron (negative beta)Band of Stability:- The further away something is from the band of stability, the less stable it is and the smaller its half life is- Band of stability plots neutrons vs protons- Isotopes want to get to a stable state so they will go through the process of alpha decay, positron, etc to reach that stable stateWorksheet:3. Write a balanced nuclear equation for the alpha decay of Po-210.210Po → 4He + 206Pb4. Experiment involving each student flipping a coin (heads = standing, tails = sitting)Interpreting the Graph:- Not linear- No constant slope- The first event shows the most Po losto There was the most Po at this time, sowhen you have the most to begin with you also have the most to lose - The Po initially and finally is related - As the change in number of Po goes down, the amount of Pb increases by that same amountHalf Life Questions:4. Imagine we started with 96 student isotopes. How many 1⁄2 lives would have to pass to get to 6 student isotopes left?4 events because…96/2 =4848/2 = 2424/2 = 1212/2 = 65. If you had 960 student isotopes, how many 1⁄2 lives would have to pass to get 60 student isotopes left?4 events because… 960/2 = 480480/2 = 240240/2 = 120120/2 = 606. P-32 has a half-life of 14 days. After 3 months what would be the residual radioactivity of1 millicurie of ATP labeled with P-32?15.625 microcuries because 3 months is about 6 half lives. Lecture 18-21KineticsClicker Question:1. Hydrogen-3 (tritium, H-3) is sometimes formed in the primary coolant water of a nuclearreactor. Tritium is a beta emitter with a t1/2 = 12. 3 years. For a given sample containing tritium, after how many years will only about 12% of the sample remain?A) 12.3 years B) 24.6 years C) 36.9 years D) 49.2 years E) 61.5 yearsKinetics:- How fast chemical reactions occur- Measure the rates of reactions (macroscopic) gives us insight into the way
View Full Document
Unlocking...