1
JEE Main 2017 (Online) 8th April Morning Slot
+4
-1
An engine operates by taking n moles of an ideal gas through the cycle ABCDA shown in figure. The thermal efficiency of the engine is : (Take Cv = 1.5 R, where R is gas constant)

A
0.24
B
0.15
C
0.32
D
0.08
2
JEE Main 2017 (Online) 8th April Morning Slot
+4
-1
An ideal gas has molecules with 5 degrees of freedom. The ratio of specific heats at constant pressure (Cp ) and at constant volume (Cv) is :
A
6
B
$${7 \over 2}$$
C
$${5 \over 2}$$
D
$${7 \over 5}$$
3
JEE Main 2017 (Offline)
+4
-1
The temperature of an open room of volume 30 m3 increases from 17oC to 27oC due to the sunshine. The atmospheric pressure in the room remains 1 $$\times$$ 105 Pa. If Ni and Nf are the number of molecules in the room before and after heating, then Nf – Ni will be :
A
- 1.61 $$\times$$ 1023
B
1.38 $$\times$$ 1023
C
2.5 $$\times$$ 1025
D
- 2.5 $$\times$$ 1025
4
JEE Main 2017 (Offline)
+4
-1
CP and Cv are specific heats at constant pressure and constant volume respectively. It is observed that
CP – Cv = a for hydrogen gas
CP – Cv = b for nitrogen gas
The correct relation between a and b is
A
a = 28 b
B
a = 1/14 b
C
a = b
D
a = 14 b
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