Quiz_2A_tom_key

Quiz_2A_tom_key - Chem 124 Spring 2008 Quiz #2 Tom Dr....

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Chem 124 Quiz #2 Tom Dr. Retsek Spring 2008 NAME: _ KEY _____________________ Computer #: ________ 1. (12 points) a. What is the wavelength (in meters) of photons with an energy of 115 kJ/mole? 115 kJ x 1000 J x 1 mole = 1.91 x 10 -19 J per photon mole 1 kJ 6.022 x 10 23 photons E = h ν and c = λν , therefore E = hc/ λ 1.91 x 10 -19 J = (6.626 x 10 -34 J s)(3.00 x 10 8 m/s) λ λ = 1.04 x 10 -6 m b. If a sample of water absorbed two moles of photons emitted with the energy in part a, how many grams of water could be heated from 30.0°C to 90.0°C? q = 2 mole x 115 kJ x 1000 J = 230,000 J mole 1 kJ q = mc T 230,000 = (m)(4.184 J/g ⋅° C)(90.0-30.0 ⋅° C) m = 916 g 2. (12 points, 2 points each) Check ( 9 ) whether the statement is true or false. Statement True False a. If the intensity of the incident light on a metal surface is increased, the velocity of the ejected electron will increase. The number of photons striking the surface (and number of ejected electrons provided they have enough energy) will increase. 9
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Quiz_2A_tom_key - Chem 124 Spring 2008 Quiz #2 Tom Dr....

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