The quick production of energy creates an explosion. A single neutron can thus begin a process that grows exponentially in a phenomenon called a chain reaction An exponential growth in a process.: 1 → 2 → 4 → 8 → 16 → 32 → 64 → 128 → 256 → 512 → 1,024 → 2,048 → 4,096 → 8,192 → 16,384 →…īecause energy is produced with each fission event, energy is also produced exponentially and in an uncontrolled fashion. These neutrons can themselves stimulate other uranium nuclei to undergo fission, releasing yet more energy and even more neutrons, which can in turn induce even more uranium fission. Notice that the fission of uranium produces two more free neutrons than were present to begin with. The two main components of the power plant are the nuclear reactor itself and the steam-driven turbine and electricity generator. We predict that the overall process will give off five neutrons.įigure 11.5 A Diagram of a Nuclear Power Plant for Generating Electricity (Because the atomic number of a neutron is zero, including five neutrons on the right does not change the overall sum of the subscripts.) Thus, the balanced nuclear equation is as follows: n 0 1 + P 94 239 u → A 79 204 u + P 15 31 + 5 n 0 1 Five neutrons should be the products of the process for the mass numbers to balance. We need five more mass number units on the right. The superscripts on the left equal 240 (1 + 239) but equal 235 (204 + 31) on the right. The subscripts are already balanced: 0 + 94 = 94 and 79 + 15 = 94. In balanced nuclear equations, the sums of the subscripts on each sides of the equation are the same, as are the sums of the superscripts. Using the data given, we can write the following initial equation: n 0 1 + P 94 239 u → A 79 204 u + P 15 31 + ? n 0 1 Write the balanced nuclear equation for the process and determine the number of neutrons given off as part of the reaction. Plutonium-239 can absorb a neutron and undergo a fission reaction to produce an atom of gold-204 and an atom of phosphorus-31. Thus, by the careful addition of extra neutrons into a sample of uranium, we can control the fission process and obtain energy that can be used for other purposes. The overall nuclear equation, with energy included as a product, is then as follows: 235U + 1n → 139Ba + 94Kr + 3 1n + energy The reaction can be controlled because the fission of uranium-235 (and a few other isotopes, such as plutonium-239) can be artificially initiated by injecting a neutron into a uranium nucleus. involves the controlled harvesting of energy from fission reactions. Nuclear energy The controlled harvesting of energy from fission reactions. If this energy could be properly harvested, it would be a significant source of energy for our society. Nuclear reactions give off billions of kilojoules per mole. Compare it to combustion reactions of hydrocarbons, which give off about 650 kJ/mol of energy for every CH 2 unit in the hydrocarbon-on the order of hundreds of kilojoules per mole. This is an extraordinary amount of energy. That is, 16.5 billion kJ of energy are given off every time 1 mol of uranium-235 undergoes this nuclear reaction. In the course of the uranium nuclear chemical reaction, the mass difference is converted to energy, which is given off by the reaction: E = (−0.0001834 kg)(3.00 × 10 8 m/s) 2 = −1.65 × 10 13 J = −1.65 × 10 10 kJ Where c is the speed of light, or 3.00 × 10 8 m/s. Where did this mass go?Īccording to Albert Einstein’s theory of relativity, energy ( E) and mass ( m) are related by the following equation: E = mc 2 If we compare the mass of the reactant (235.0439) to the masses of the products (sum = 234.8605), we notice a mass difference of −0.1834 g, or −0.0001834 kg. Consider the following nuclear reaction, in which the molar mass of each species is indicated to four decimal places: U 235 235.0439 → B 139 a 138.9088 + K 94 r 93.9343 + 2 n 1 2 × 1.0087 Where does this energy come from? If we could precisely measure the masses of the reactants and the products of a nuclear reaction, we would notice that the amount of mass drops slightly in the conversion from reactants to products. Nuclear changes occur with a simultaneous release of energy. Describe the difference between fission and fusion.Explain where nuclear energy comes from.
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