Question

fill in the blanks in the tables

	first run (100 mL water)	second run (70 mL water)	third run (50 mL water)
mass of MgSO4 (g)	8	8	8
volume of water (mL)	100	70	50
mass of final soln (g)	108.2553	77.9995	59.5059
TI, initial temperature of water (°C)	25	25	25
TF, final temperature of water (°C)	38.5	44.3	52.0
∆T (°C)	+13.5	+19.3	+27
heat absorbed by the solution (J)
heat produced by the reaction (J)
∆Hrxn (J g-1 MgSO4)
mass MgSO4 /mass of water	8/100 = .08	8/70 = .11	8/50 = .16

  

4. Fill in Table 3 in the Data Sheet in your notebook.  

5. In your calculations, you can assume that the heat absorbed by the solution to raise its temperature is equal to the amount of heat generated by the reaction. Also, assume that the specific heat of the solution is the same as that of pure water, 4.18 J g^-1 °C^-1.
   

6. Repeat the procedure two more times. For the second sample, use 70 mL tap water. For the third sample, use 50 mL tap water. You should use approximately the same mass of MgSO₄ each time.

Experiment III: Development of a Heat Pack

Follow the directions for

http://chemcollective.org/activities/autograded/118

Based on your results from part 1, design a hot pack using MgSO₄(s). The hot pack should have a total mass of 90.0 g (salt plus water) and be able to achieve a temperature of 43.0°C. Assume a specific heat for the solution of 4.184 J/g°K (same as for water) and an initial temperature of 25°C for the water in the hot pack. Just as you did for the first part, you will be using a coffee cup (the virtual lab describes using glassware).  

In your lab notebook show a detailed calculation which shows how you predict what you will need for your heat pack and record your information in Table 5.

Table 5. Proposed Heat Pack Recipe

mass of MgSO4
volume of water
Target temperature change
Evaluation of heat pack performance:

Answer 1