Thermodynamics Physics Edition Flashcards
In a new ITC experiment, the sample cell originally contains 20 μL of solution at 313K. When 2 μL of solution was added to the sample cell, the temperature changed to 311 K. If the density of the solution is 1 g/mL, the heat capacity of the solution is 5.1 J/kg•ºC, and the rate of heat transfer from the heater is 0.005 J/s, how long will it take the solution in the sample cell to return to its original temperature?
40 ms
This question requires us to use the equation for heat transfer with heat capacity: Q = mcp∆T (which is easy to remember since it looks like MCAT). We are given the cp of the solution and the ∆T, and we can determine the mass using the density and the volume. Be sure to watch units and remember that a 2 degree change in Celsius is equivalent to a 2 degree change in Kelvin!
The heat equation will tell us the total amount of heat that needs to be transferred to raise the temperature 2℃ back to the original temperature.
Finally, the rate of heat transfer can be used to calculate the amount of time required to transfer this amount of heat energy
