Chapter 7 Key

# Chapter 7 Key - Chapter 7 Homework Key 1 2 C-14 C-12 H-3...

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Chapter 7 Homework Key 1. 14 N has only 7 neutrons in the nucleus and a total mass of 14. 15 N has 8 neutrons in the nucleus and a total mass of 15. 2. # of protons # of neutrons C-14 6 8 C-12 6 6 H-3 1 2 Tc-99 43 56 3. Nuclear: n 3 Kr Ba U n 1 0 92 36 141 56 235 92 1 0 + + + (other examples possible) Chemical: CH 4 + 2 O 2 → CO 2 + 2H 2 O (other examples possible) Alike: Both must be balanced, the chemical reaction in terms of number and type of atoms, the nuclear reaction in terms of mass numbers and atomic numbers. Different: In chemical reactions the atoms don’t change type, they just rearrange by breaking and forming bonds. In nuclear reactions the nucleus is actually changed to form elements that weren’t present before. 4. Energy in nuclear reactions comes from mass from the nucleus converted to energy. 5. a. n He H H 1 0 3 2 2 1 2 1 + + b. Es Pu 5 N U 247 99 1 0 14 7 238 92 + + c. Kr Es n 3 n Pu 91 36 146 58 1 0 1 0 239 94 + + + 6. J 10 X 2.385 m/s) 10 x g)(3.00 (.0000265k mc E .0000265kg 1000g 1kg x .0265g 12 2 8 2 = = = = 7. Mass difference: .0196g

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Mass is lost in the reaction, so energy is given off. J 10 X 1.764 m/s) 10 x g)(3.00 (.0000196k mc E .0000196kg 1000g 1kg x .0196g 12 2 8 2 = = = = The heat of combustion for 1 mole of methane is 802.3 kJ, or 802,300 J. This is much less than the energy from the fusion reaction.
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Chapter 7 Key - Chapter 7 Homework Key 1 2 C-14 C-12 H-3...

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