The \"steam\" above a freshly made cup of instant coffee is really water vapor d

Question

The "steam" above a freshly made cup of instant coffee is really water vapor droplets condensing after evaporating from the hot coffee. What is the final temperature of 205 g of hot coffee initially at 90.0°C if 3.18 g evaporates from it? The coffee is in a Styrofoam cup, and so other methods of heat transfer can be neglected. Assume that coffee has the same physical properties as water; its latent heat of vaporization is 539 kcal/kg and its specific heat is 1.00 kcal/(kg · °C). Incorrect: Your answer is incorrect. Where does the heat for the evaporation come from?°C

Explanation / Answer

cM[t(ini) –t(fin)] = mr
cMt = mr
t= mr/cM= (2*10^-3*2260*10^3)/(4183*0.250) = 8.38
T(fin) = 90-8.38 = 81.62

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