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Author Question: A substance has a melting point of 20C and a heat of fusion of 3.5 104 J/kg. The boiling point is ... (Read 55 times)

clmills979

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on: Jul 29, 2018
A substance has a melting point of 20C and a heat of fusion of 3.5  104 J/kg. The boiling point is 150C and the heat of vaporization is 7.0  104 J/kg at a pressure of 1.0 atm.
 
  The specific heats for the solid, liquid, and gaseous phases are 600 J/(kgK), 1000 J/(kgK), and 400 J/(kgK), respectively. The quantity of heat given up by 0.50 kg of the substance when it is cooled from 170C to 88C, at a pressure of 1.0 atmosphere, is closest to
  A) 30 kJ. B) 70 kJ. C) 44 kJ. D) 21 kJ. E) 14 kJ.

Question 2

A metal having a work function of 2.8 eV is illuminated with monochromatic light whose photon energy is 3.9 eV.
 
  What is the threshold frequency for photoelectron production? (h = 6.626  10-34 J  s, 1 eV = 1.60  10-19 J)
  A) 6.8  1014 Hz
  B) 2.7  1014 Hz
  C) 7.6  1014 Hz
  D) 8.5  1014 Hz
  E) 9.4  1014 Hz


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mariahkathleeen

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Reply #1 on: Jul 29, 2018
Answer to Question 1

B

Answer to Question 2

A


clmills979

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Reply 2 on: Jul 29, 2018
Great answer, keep it coming :)

laurnthompson

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Reply 3 on: Yesterday
Excellent

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