Calories required to boil 1 gm of water at 99°C
To calculate the calories required to boil 1 gm of water at 99°C, we need to consider the specific heat of water and the heat of vaporization.

Specific Heat of Water:
Water has a specific heat of 1 calorie/gram °C. This means that it takes 1 calorie to raise the temperature of 1 gram of water by 1°C.

Heat required to raise the temperature of water from 99°C to 100°C:
Since water's specific heat is 1 calorie/gram °C, it would take 1 calorie to raise the temperature of 1 gram of water from 99°C to 100°C.

Heat of Vaporization of Water:
The heat of vaporization of water is 540 calories/gram. This means that it takes 540 calories to convert 1 gram of water at 100°C to steam at 100°C.

Total calories required:
To boil 1 gram of water at 99°C, we need to first raise its temperature from 99°C to 100°C, which requires 1 calorie. Then, we need to vaporize it, which requires an additional 540 calories. Therefore, the total calories required to boil 1 gram of water at 99°C is 541 calories.
In conclusion, it takes a total of 541 calories to boil 1 gram of water at 99°C.

tell me if d ans. is 1 calorie...