1. The heat of vaporization of water is 540 cal/g. What mass of water at 100°C c

Question

1. The heat of vaporization of water is 540 cal/g. What mass of water at 100°C can be vaporized by the addition of 45.0 kcal of heat? a. 0.0120 g b. 0.0833 g c. 12.0g d. 83.3 g TOPICS: 5.10 - WHAT IS A PHASE CHANGE AND WHAT ENERGIES ARE INVOLVED? 2. The specific heat of iron is 0.110 cal /g °C. The heat of fusion of iron is 63.7 cal/g. The melting point of iron is 1530°C. How much heat must be added to 10.0 g of iron at 25°C to completely melt it? a. 0.637 kcal c. 1.676 kcal b. 0.803 kcal d. 2.29 kcal 3. The specific heat of water is 1.0 cal/g C. The heat of vaporization of water is 540 calg. Which of the following is true? a. It takes less energy to evaporate one gram of water than it does to heat one gram of water from 0°C to 100°C b. It takes more energy to evaporate one gram of water than it does to heat one gram of water from 0°C to 100°C c. It takes the same amount of energy to evaporate one gram of water as it does to heat one gram of water from 0°C to 100°c d. There is insufficient information to answer the question. a. evaporation b. melting Csublimation d. None, they all involve a liquid. dvecity t ges stakedry t 4. Which of the following phase changes does not involve a liquid? Sd Sale sublimafon- Change Consider the following phase diagram of water. The temperature and pressure scales are greatly reduced (and are non linear) 458 5. Crossing the curve designated AC in the direction of high pressure to low pressure is associated with which of the following phase transitions? a. solid to liquid c. liquid to vapor b. solid to vapor d. vapor to liquid

Explanation / Answer

Ans 1)

Given heat of vaporization of water is 540cal/g i.e. 540 cal heat require to 1 g of water

1 kcal = 1000 cal so we have given amount of heat is 45.0 kcal

so we calculate mass of water i.e. vaporized at 45 kcal heat

540 cal haet require to vaporized 1 g water so at 45000 cal heat requires X g of wter

540 = 1

45000 = X

540 x = 1 x 45000 i.e. x = 45000/540 =83.3 g

So 83.3 g mass of water is vaporised at 45 kcal heat

So option D is correct

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