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Unformatted text preview: homework 01 KIM, JI Due: Jan 20 2008, 4:00 am 1 Question 1, chap 22, sect 1. part 1 of 1 10 points You have 3 . 6 kg of water. One mole of water has a mass of 18 g / mol and each molecule of water contains 10 electrons since water is H 2 O. What is the total electron charge contained in this volume of water? Correct answer: 1 . 92708 10 8 C (tolerance 1 %). Explanation: Let : N A = 6 . 02214 10 23 molec / mol , q e = 1 . 6 10 19 C / electron , M = 18 g / mol = 0 . 018 kg / mol , m = 3 . 6 kg , and Z = 10 electrons / molec . The mass is proportional to the number of molecules, so for m grams in n molecules and M grams in N A molecules, m M = n N A n = m M N A . Since 10 electrons are in each molecule of water, then the total number of electrons n e in the coin is n e = Z n = Z m M N A and the total charge q for the n e electrons is q = n e q e = Z mN A q e M = (10 electrons / molec) 3 . 6 kg . 018 kg / mol (6 . 02214 10 23 molec / mol) ( 1 . 6 10 19 C / electron) = 1 . 92708 10 8 C . Question 2, chap 22, sect 1. part 1 of 3 10 points We want to find how much charge is on the electrons in a nickel coin. Follow this method. A nickel coin has a mass of about 5 . 2 g. Each mole (6 . 02 10 23 atoms) has a mass of about 58 g. Find the number of atoms in a nickel coin. Correct answer: 5 . 39724 10 22 atoms (toler ance 1 %). Explanation: Let : N a = 6 . 02 10 23 atoms , M = 58 g , and m = 5 . 2 g . Mass is proportional to the number of atoms in a substance, so for m grams in N atoms in the nickel coin and M grams in N a atoms in one mole, we have m M = N N a N = m M N a = 5 . 2 g 58 g (6 . 02 10 23 atoms) = 5 . 39724 10 22 atoms . Question 3, chap 22, sect 1. part 2 of 3 10 points Find the number of electrons in the coin. Each nickel atom has 28 electrons / atom. Correct answer: 1 . 51123 10 24 electrons (tol erance 1 %). Explanation: Let : n Ni = 28 electrons / atom . If n Ni electrons are in each Nickel atom, then the total number of electrons n e in the coin is n e = N n Ni = ( 5 . 39724 10 22 atoms ) (28 electrons / atom) = 1 . 51123 10 24 electrons . homework 01 KIM, JI Due: Jan 20 2008, 4:00 am 2 Question 4, chap 22, sect 1. part 3 of 3 10 points Find the magnitude of the charge of all these electrons. Correct answer: 242125 C (tolerance 1 %). Explanation: Let : q e = 1 . 60218 10 19 C / electron . The total charge q for the n e electrons is q = n e q e = (1 . 51123 10 24 electrons) ( 1 . 60218 10 19 C / electron ) = 242125 C , which has a magnitude of 242125 C . Question 5, chap 22, sect 2. part 1 of 1 10 points Two charges q 1 and q 2 are separated by a distance d and exert a force F on each other....
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This note was uploaded on 05/05/2008 for the course PHY 303L taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
 Spring '08
 Turner
 Physics, Mass, Work

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