The best way to attack each problem is to read it carefully, and identify the fi

Question

The best way to attack each problem is to read it carefully, and identify the first-law formulation that you will use to solve it. Then you should carefully apply that first-law formulation In the desert, a 1-liter container of Gatorade is initially at 42 degree C. It is put into a cooler that initially contains ice at -3 degree C (and no liquid water), which is closed and maintained with perfect insulation. Assuming that the Gatorade has a temperature- and pressure-independent specific heat of 4.3 kJ/(kgK), what is the minimum amount of ice required to cool the Gatorade to 2 degree C? Neglect the presence of any air in the cooler and the mass of the container A thin-walled container with perfect thermal insulation holds 2.0 kg of an aqueous salt solution, which is at an initial temperature of 18 degree C. A 120 V DC current is applied, and Joulean dissipation in the liquid heats the contents of the container to an average temperature of 27 degree C in three minutes. If the specific heat of the liquid is [4.2 +0.3(T-18 degree C) kJ/(kgK), determine the overall resistance (in ohms of the salt solution and its container. During the heating process, vapor pressure is negligible. You should assume that the resistance is independent of temperature, neglect the mass of the container, and assume that the contents are well mixed (i.e., uniform) during the process.

Explanation / Answer

Solving first question

Using

heat given=heat taken

Let the mass of ice be m

m*2100*3 + m*336000 + m*4200*2=2*4300*40

m=344000/350700=0.98 kg

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