Physics-
General
Easy

Question

The temperature of a gas is -68℃. At what temperature will the average kinetic energy of its molecules be twice that of at -68℃?

  1. 137 ℃    
  2. 127℃    
  3. 100℃    
  4. 105℃    

The correct answer is: 137 ℃


    Average kinetic theory of one molecule is
    E equals fraction numerator 3 over denominator 2 end fraction k T
    where k is Boltzmann constant and T the absolute temperature.
    Given, T subscript 1 end subscript equals negative 68 ℃ equals 273 minus 68 equals 205 blank K comma
    E subscript 1 end subscript equals E comma blank E subscript 2 end subscript equals 2 E
    therefore blank fraction numerator E subscript 1 end subscript over denominator E subscript 2 end subscript end fraction equals fraction numerator T subscript 1 end subscript over denominator T subscript 2 end subscript end fraction
    rightwards double arrow blank T subscript 2 end subscript equals fraction numerator T subscript 1 end subscript E subscript 2 end subscript over denominator E subscript 1 end subscript end fraction
    therefore blank T subscript 2 end subscript equals fraction numerator 205 cross times 2 E over denominator E end fraction equals 410 blank K

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