# Homework Help: Help -heat Of Vaporization

1. Mar 1, 2004

### nsw

Help!!---heat Of Vaporization

I could really use some help with this please!!!!!

125 grams of dry ice (solid CO2)is dropped into a beaker containg 500 grams of 66 degree celsius water. The dry ice converts directly to gas, leaving the solution. When the dry ice is gone, the final temperature of the water is 29 degrees celsius. What is the heat of vaporization of solid CO2?

2. Mar 1, 2004

### Bystander

Homework is handled on a "you show us what you've done, and we'll point you in the direction you need to go." Take a couple wild swings --- think about the initial state (dry ice + water) and the final state, and what has happened to get from initial to final.

3. Mar 1, 2004

### nsw

heat of vaporization

Doesn't it have to do with the Qlost=Qgain

4. Mar 1, 2004

### Bystander

I said, "...wild swing...." For a first guess, you're not doing too badly --- at the same time, very few things don't have anything to do with Ql and Qg.

You are evaporating carbon dioxide; the specific process is transition from solid phase to vapor ("sublimation" for the anal-retentive). This process requires heat, specifically, the "heat of vaporization" you used to title the thread. What do you have available as a heat source for this process in this problem?

5. Mar 1, 2004

### Loren Booda

Consider the dry ice and the water to comprise an adiabatic (closed with respect to heat) system, so that the loss of heat (defined in terms of calories) from the water equals the heat needed to sublimate the CO2 mass.

6. Mar 1, 2004

7. Mar 1, 2004

### himanshu121

ok what is Qlost & Qgain Write them in terms of mass. specific etc, Heat of sublimation etc

8. Mar 1, 2004

### nsw

Q=mass*specific heat*change in temp.

But how does this help me?

9. Mar 2, 2004

### Bystander

10. Mar 2, 2004

### nsw

yes it does talk about temperature change

11. Mar 2, 2004

### Bystander

What temperature change?

12. Mar 2, 2004

### nsw

The temperature change is of the fluid in the beaker which goes from 66 to 29 degrees celsius.

13. Mar 2, 2004

### Bystander

How much heat is required for this temperature change?