You drop a 297-g silver figure of a polar bear into the 205-g aluminum cup of a well-insulated calorimeter containing 277 g of liquid water at 24.5°C. The bear\'s initial temperature is 95.5°C. What is the final temperature of the water, cup, and bear when they reach thermal equilibrium? The specific heats of silver, aluminum, and liquid water are, respectively, 234 J/(kg·K), 910 J/(kg·K), and 4190 J/(kg·K).
Answer – We are given, mass of silver = 297 g , mass of Al cup = 205 g, mass of water = 277 g , ti = 24.5 o C , initial temp bears = 95.5oC
Specific heat of silver = 0.234 J/goC , Al = 0.910 J/goC , Water = 4.190 J/goC
We know,
Heat loss of silver figure of a polar bear = Heat gain by water + Al
For silver figure of a polar bear, q= - m1*CAg*∆t
For water , q = m2*Cwater*∆t
For aluminum, q = m3*CAl*∆t
We know,
- m1*CAg*∆t = m2*Cwater*∆t + m3*CAl*∆t
-297 g * 0.234 J/goC*(tf-95.5oC) = 277 g * 4.190 J/goC * (tf-24.5o)+ 205 g * 0.910 J/goC*(tf-24.5oC)
-69.498 tf + 6637.06 = 1160.63tf-28435.44 + 186.55tf - 4570.5
-69.498 tf – 1160.6 tf – 186.55 tf = -6637.06 -28435.44 - 4570.5
-1416.6 tf = -39643
So, tf = 27.98 oC
final temperature of the water, cup, and bear when they reach thermal equilibrium is 27.98 oC
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