# 10 - fryer (vdf96) Assignment 7 Static Charge and Electric...

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fryer (vdf96) – Assignment 7 Static Charge and Electric Force – graves – (6) 1 This print-out should have 22 questions. Multiple-choice questions may continue on the next column or page – ±nd all choices before answering. 001 (part 1 of 2) 10.0 points A strong lightning bolt transfers an electric charge of about 31 C to Earth (or vice versa ). How many electrons are transferred? Avo- gadro’s number is 6 . 02214 × 10 23 / mol. Correct answer: 1 . 93487 × 10 20 . Explanation: Let : q = 31 C and q e = 1 . 60218 × 10 - 19 C . The charge is proportional to the number of electrons, so q = n | q e | n = q | q e | = 31 C |− 1 . 60218 × 10 - 19 C | = 1 . 93487 × 10 20 . 002 (part 2 of 2) 10.0 points If each water molecule donates one electron, how much water is ionized in the lightning? One mole of water has a mass of 17 . 9 g / mol. Correct answer: 0 . 00575113 g. Explanation: Let : M = 17 . 9 g / mol and N a = 6 . 02214 × 10 23 / mol . Mass is proportional to the number of atoms in a substance, so for m grams in N atoms in the water and M grams in N a atoms in one mole, we have m M = N N a N = m M N a Since every water molecule donates one electron to the discharge, the total number of transferred electrons n e equals the total number n H 2 O of ionized water molecules, so the total mass of the water ionized by the lightning bolt is M total = n H 2 O m H 2 O = n e M H 2 O N A = ( 1 . 93487 × 10 20 ) (17 . 9 g / mol) 6 . 02214 × 10 23 / mol = 0 . 00575113 g . 003 (part 1 of 3) 10.0 points We want to ±nd how much charge is on the electrons in a nickel coin. Follow this method. A nickel coin has a mass of about 4 . 2 g. Each mole (6 . 02 × 10 23 atoms) has a mass of about 57 . 9 g. Find the number of atoms in a nickel coin. Correct answer: 4 . 36684 × 10 22 atoms. Explanation: Let : N a = 6 . 02 × 10 23 atoms , M = 57 . 9 g , and m = 4 . 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 = (4 . 2 g) (57 . 9 g) (6 . 02 × 10 23 atoms) = 4 . 36684 × 10 22 atoms . 004 (part 2 of 3) 10.0 points Find the number of electrons in the coin. Each nickel atom has 28 electrons / atom. Correct answer: 1 . 22272 × 10 24 electrons.

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fryer (vdf96) – Assignment 7 Static Charge and Electric Force – graves – (6) 2 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 = ( 4 . 36684 × 10 22 atoms ) × (28 electrons / atom) = 1 . 22272 × 10 24 electrons . 005 (part 3 of 3) 10.0 points Find the magnitude of the charge of all these electrons. Correct answer: 1
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## This note was uploaded on 12/11/2011 for the course PHYSICS 101 taught by Professor Graves during the Fall '10 term at San Jose City College.

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10 - fryer (vdf96) Assignment 7 Static Charge and Electric...

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