Answer:
40°C.
Step-by-step explanation:
A calorie is defined as the amount of energy needed to raise the temperature of 1 gram of water through 1 °C. In the same way, a kcal would be defined as the amount of energy needed to raise the temperature of 1 kilogram of water through 1 °C.
Based on this definition, 100kcal will increase the emperature of the water in:
100kcal / 2,5kg = 40°C
I hope it helps!