Question

Rakhi took four different beakers I, II, III, and IV each containing 2 litre water. Also, she took four fuels A, B, C, and D. Then, she started heating the water in beakers I, II, III, and IV using 1 kg of each A, B, C, and D respectively. She found out that the heat produced by complete combustion of 2 kg of A, 4 kg of B, 6 kg of C, and 8 kg of D is 100000 kJ, 240000 kJ, 420000 kJ, and 320000 kJ respectively. Assume that all the heat released by burning the fuel is absorbed by water. In which beaker does the maximum evaporation take place?

• A. I
• B. II
• C. III
• D. IV

Answer 1

The correct option is C III

$\bullet$ The higher the calorific value of fuel, the higher is the amount of heat energy released on its combustion.
$\bullet$ The calorific value of fuel is the amount of heat energy produced by complete combustion of 1 kg of fuel.
$\bullet$ For fuel A: 2 kg of A produces 100000 kJ of heat. 1 Kg of A will produce $\frac{100000}{2}=50000KJofheat$
$\therefore$ Calorific value of A is 50000 KJ/Kg
$\bullet$ For fuel B: 4 kg of B produces 240000 kJ of heat. 1Kg of B will produce $\frac{240000}{4}=60000KJofheat$
$\therefore$ Calorific value of B is 60000 KJ/Kg
$\bullet$ For fuel C: 6 Kg of C produces 420000 kJ of heat. 1Kg of C will produce $\frac{420000}{6}=70000KJofheat$
$\therefore$ Calorific value of C is 70000 KJ/Kg
$\bullet$ For fuel D: 8 kg of A produces 320000 kJ of heat. 1 Kg of D will produce $\frac{320000}{8}=40000KJofheat$
$\therefore$ Calorific value of D is 40000 KJ/Kg
Since the calorific value of C is the highest, Hence, maximum evaporation takes place in beaker III. The correct answer is C.