Q52 / 54 · JEE Advanced 2019 (Paper 1) · Physics
A liquid at is poured very slowly into a Calorimeter that is at temperature of The boiling temperature of the liquid is It is found that the first of the liquid completely evaporates. After pouring another of the liquid the equilibrium temperature is found to be The ratio of the Latent heat of the liquid to its specific heat will be ______
[Neglect the heat exchange with surrounding]
[Neglect the heat exchange with surrounding]
Correct answer: 270
Solution
Note: The information about condition of calorimeter is not given in question, so following two cases arise -
Case : If calorimeter is closed (vapour not allowed to escape)
Heat gain Heat loss
(as first liquid is evaporated)
Specific heat of liquid
Latent heat of liquid
W=Water equivalent of calorimeter
...(i)
Now liquid is poured,
Heat gain Heat loss
Here final temperature
...(ii)
From (i) and (ii)
Case : If calorimeter is open and after evaporation liquid escapes
...(i)
(as first liquid is evaporated)
...(ii)
(after pouring liquid, the equilibrium temperature is
(using (i) and (ii)
Case : If calorimeter is closed (vapour not allowed to escape)
Heat gain Heat loss
(as first liquid is evaporated)
Specific heat of liquid
Latent heat of liquid
W=Water equivalent of calorimeter
...(i)
Now liquid is poured,
Heat gain Heat loss
Here final temperature
...(ii)
From (i) and (ii)
Case : If calorimeter is open and after evaporation liquid escapes
...(i)
(as first liquid is evaporated)
...(ii)
(after pouring liquid, the equilibrium temperature is
(using (i) and (ii)
Hence, the correct answer is 270.