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You and a friend are hiking the Appalachian Trail when a storm comes through. You stop to eat, but find that all available firewood is too wet to start a fire. From your chemistry class you remember that heat is given off by some chemical reactions; if you could mix two solutions together to produce an exothermic reaction, you might be able to cook the food you brought along for the hike. Luckily, being the dedicated chemist that you are, you never go anywhere without taking along a couple chemical solutions, just for times like this. The Virtual Lab contains solutions of compounds X and Y. These compounds react to produces a new compound, Z, according to the reaction:
X + Y --> Z
The following activities will guide you in using this reaction to produce the heat needed to warm up your food to 50ºC.
Note: In this activity, you will use the Virtual Lab to solve a problem that deals with heat transfer in solutions. In order to accurately measure temperature changes in the virtual lab, it is helpful to be able to insulate a piece of glassware from its surroundings. To do this in the Virtual Lab, use the "Thermal Properties" dialogue. Windows users should right click on the beaker or flask; Mac-users should command-click on the beaker or flask. From the menu that appears, choose "Thermal Properties." Check the box labeled "insulated from surroundings." The temperature of the solution in that beaker or flask will remain constant.
Experimental part: DONE
| What is the enthalpy of reaction for this reaction? |
| Well done! You did a good job! |
| To design the solutions you will need to heat your food, you can obtain valuable data by measuring the changes in temperature when mixing: |
| Explain the temperature changes you observe in terms of the various volumes and concentrations involved. |
| Let's go for the last one! |
| Design two solutions, initially at 25ºC, that, when mixed together in equal volumes, cause the temperature of the mixture to increase from 25ºC to 50ºC. |
| Great! You are done! |