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Towson University
John R.
Chemistry 101
4 months, 1 week ago
Joanna S. How many calories does it take to heat 10 grams of 16 degree C water to a vapor?
1 Expert Answer
John K. answered • 07/12/19
Personal Tutor for Organic Chemistry and General Chemistry
There are two parts to this problem.
- calculating the calories needed to heat the water to boiling (100oC).
- calculating the calories needed to vaporize the boiling water.
Part 1. It takes 1 calorie to increase the temperature of 1 gram of water one degree centigrade. There are 84 degrees to heat the water from 16oC to 100o Centigrade. Therefore, 84 calories are needed to heat 1 gram of water to 100oC; for 10 grams of water, ten times that amount of calories are needed: 10 x 84 calories = 840 calories.
Part 2. The Heat of Vaporization of water is 540 calories per gram;since we have 10 grams of water to vaporize, we need 5,400 calories for vaporization.
The answer to the problem is the sum of Part 1 and Part 2 = 840 calories + 5,400 calories = 6,240 calories.
A quart of water is 946.35 cubic centimeters and since density of water is 1 gram per cubic centimeter the weight of a quart of water is 946.35 grams. Heat required = (mass) x (specific heat of substance) x (temperature differential) In our case it would be 946.35 x 1 x 38(assumed degrees centigrade) = 35961.3 cals