70 calories of heat are required to raise the temperature of 2 moles of an ideal gas at constant pressure from 30oC to 35oC. The amount of heat required to raise the temperature of the same gas through same range (30oC to 35oC) at constant volume is:


Correct option is

50 cal


Heat absorbed at constant pressure to increase the temperature by 


Heat required to raise the temperature of same gas by dT at constant volume is,






A reversible engine converts one-sixth of the heat input into work. When the temperature of the sink is reduced by 62oC, the efficiency of the engine is doubled. The temperatures of the source and sink are:


We consider a thermodynamic system. If  represents the increase in its internal energy and the work done by the system, which of the following statements is true?


If the ratio of specific heats of a gas at constant pressure to that at constant volume is , the change in internal energy of the given mass of gas, when the volume changes from to 2V at constant pressure P is:


A Carnot engine uses first an ideal mono-atomic gas () and then an ideal diatomic gas () as its working substance. The source and sink temperatures are 411oC and 69oC respectively and the engine extracts 1000 J of heat from the source in each cycle. Then:


If R is universal gas constant, the amount of heat needed to raise the temperature of 2 moles of an ideal mono-atomic gas from 273 K to 373 K when no work is done is:


The temperatures of inside and outside of a refrigerator are 273 K and 303 K respectively. Assuming that the refrigerator cycle is reversible, for every joule of work done, the heat delivered to the surroundings will be nearly:


In a thermodynamic process, pressure of a fixed mass of a gas is changed in such a manner that the gas releases 20 J of heat and 8 J of work is done on the gas. If initial internal energy of the gas was 30 J, what will be the final internal energy?



An ideal gas is taken through a cyclic thermo-dynamical process through four steps. The amounts of heat involved in these steps are:

    respectively. The corresponding works involved are:  respectively. The value of W4 is:


When an ideal diatomic gas is heated at constant pressure fraction of the heat energy supplied which increases the internal energy of the gas is:


A motor-car tyre has a pressure of 2 atmosphere at 27oC. It suddenly bursts. If (Cp/Cv) = 1.4 for air, find the resulting temperature: