Figure shows an indicator diagram. During path 1-2-3, 100 cal is given to the system and 40 cal worth work is done. During pat 1-2-3, the work done is 10 cal . Then

Options

A. heat given to the system during path 1-2-3 is 70 cal
B. if the systems is brought from 3 to 1 along straight line path 3-1, work done is worth 25 cal
C. along straight line path 3-1, the heat ejected by the system is `85 J`
D. the internal energy of the system in state 3 is 140 cal above that in state 1

Answer

A, B, C

Explanation

The critical step is that work in path `1-3` is mean of that for `1-2-3` and `1-4-3(` considering areas `)`
For `(a)` `100-40=x-10`
or , `x=70 cal`
For `(b)` , It is also correct as half of `(40+10)` is 25 cal
For `(c), dU ` is `-60`, work `-25`
So ` -60=dQ-(-25)`
or `dQ=-85 cal`
For `(d)` `dU= 100 - 40= 60 cal`
Hence, option `(d)` is not correct.