A system absorbs 300 cal of heat, its volume doubles and temperature rises from 273 to 298 k, the work done on the surrounding is 200 cal. ΔE for the above reaction is :
A
100 cal
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B
500 cal
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C
-500 cal
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D
-100 cal
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Solution
The correct option is D 100 cal As per the sign convention, the heat absorbed by the system has positive sign. Hence, q=+300cal When work is done by the system on the surroundings, it has negative sign. Thus w=−200cal. The expression for the change in the internal energy is ΔE=q+w=+300cal−200cal=100cal Thus, the net internal energy of the system increases by 100 cal.