Find the final equilibrium temperature when 20.0 g of milk at 10.0°C is added to 160 g of coffee at 90.0°C.(Assume the specific heats of coffee and milk are the same as water and neglect the heat capacity of the container,and c_water = 1.00 cal/g·°C = 4186 J/kg·°C) A) 85.3°C B) 81.1°C C) 71.4°C D) 66.7°C

Question

Quizplus · Accepted Answer

Q1 = m1cΔT1 = 20.0 g × 4.186 J/g°C × (Tf - 10.0°C)
Q2 = m2cΔT2 = 160 g × 4.186 J/g°C × (Tf - 90.0°C)
Since the heat lost by hot coffee equals the heat gained by cold milk, we have:
Q1 = Q2
20.0 g × 4.186 J/g°C × (Tf - 10.0°C) = 160 g × 4.186 J/g°C × (Tf - 90.0°C)
Solving for Tf gives: Tf = 81.1°C. 
Therefore, the answer is B.

Find the Final Equilibrium Temperature When 20