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JEE MainChemistryThermodynamics (C)

An electric heater of power 150 W is used to heat a gas enclosed in a constant volume container with adiabatic walls. If the heat capacity of the gas is 450 J K ⁻¹ , the time for which the heater must be operated to raise the temperature of the gas by 20^ C is _____ s.

Correct answer

60

Step-by-step solution

Heat required to raise the temperature of the gas is given by: q = C_v T Given: Heat capacity, C_v = 450 J K ⁻¹ Change in temperature, T = 20^ C = 20 K Therefore, the heat required is: q = 450 20 = 9000 J The heat is supplied by an electric heater of power P = 150 W (or 150 J s ⁻¹ ). Since q = P t , the time required is: t = q P = 9000 150 = 60 s Answer: 60

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