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Get Full Access to Chemistry: A Molecular Approach - 3 Edition - Chapter 6 - Problem 27e
Get Full Access to Chemistry: A Molecular Approach - 3 Edition - Chapter 6 - Problem 27e

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# What is a standard state? What is the standard enthalpy ISBN: 9780321809247 1

## Solution for problem 27E Chapter 6

Chemistry: A Molecular Approach | 3rd Edition

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Problem 27E

Problem 27E

What is a standard state? What is the standard enthalpy change for a reaction?

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Step 1 of 3

Solution: According to Planck’s quantum theory of radiation, the amount of energy associated with a quantum(in case of light, the quantum of energy is often called photon) of radiation is proportional to the frequency of light, E = h ---(1), where h is a universal constant called Planck’s constant. is the frequency and E is the energy of a photon. Or, E = hc/ -------(2), where, is the wavelength of light and c is the velocity. Step1: Given, wavelength of the light = 3.3 m -6 -6 = 3.3 x 10 m[1 m = 10 m] M Planck's constant, h = 6.626 x 10 J.s -34 8 Velocity of light, c = 3 x 10 m/sec Substituting the values in equation (2), we get, E = [(6.626 x 10 J.s) x (3 x 10 m/sec)] / (3.3 x 10 m) -6 -20 = 6.02 x 10 J Thus, energy of one photon of the radiation is 6.02 x 10 J. -20 Step2: Again, wavelength of the light = 0.154 nm = 0.154 x 10 m -9 [1 nm = 10 m]-9 -10 = 1.54 x 10 m M Planck's constant, h = 6.626 x 10 J.s -34 8 Velocity of light, c = 3 x 10 m/sec Substituting the values in equation (2), we get, E = [(6.626 x 10 J.s) x (3 x 10 m/sec)] / (1.54 x 10 -10m) -16 = 12.91 x 10 J = 1.291 x 10 J -15 -15 Thus, energy of one photon of the radiation is 1.291 x 10 J. Step3: Since, wavelength is inversely proportional to energy of the photon, therefore, energy of the photon with wavelength 0.154 nm is higher. Step4: The photon with 3.3 m wavelength lies in the infrared region of the electromagnetic spectrum and the photon with 0.154 nm wavelength lies in the x-ray region of the electromagnetic spectrum. ---------------

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##### ISBN: 9780321809247

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