Question

The latent heat of vaporization of water is 540 calories/gram. How many calories are required to completely vaporize 500 grams of water? A. 1,040 cal B. 40 cal C. 270,000 cal D. 1.08 cal

Answer 1

The amount of heat needed to vaporize the given amount of water is the product of the amount in grams and the latent heat of vaporization in cal per gram. That is,
                              H = (540 calories / gram)( 500 grams) = 270,000 cal
Thus, the heat needed is 270, 000 calories. The answer is letter C. 

Answer 2

1 g = 540 calories 
500 g = ? calories 

Since the mass is 500 times 1 g, so the number of calories 
= 500*540 calories
=270,000 calories
Best Option is letter C.270,000 cal.