In: Physics
A 190 g piece of ice at 0°C is placed in 400 g of water at 24°C. The system is in a container of negligible heat capacity and is insulated from its surroundings.
(a) What is the final equilibrium temperature of the
system?
°C
(b) How much of the ice melts?
g
Unless asked to solve using SI units, it is much easier tosolve in cgs units and calorie for heat.
If m gram of ice melts and Tf is the final temp the heatgained by ice & the melted water = Heat lost by the warmwater.
Then Q1 = Q2
gives, m.L + mct = Mc(24-t)
Two unknowns and one eqn only. Difficult to solve.
Let us see if all of the ice is melted.
Heat required to melt the 190 g of ice,
Q = mL = 190x76 = 14440 cal.
Heat available in all of the warm water cooling down to0oC,
Q' = 400x1x24 = 9600 cal
Since Q> Q' allof the ice cannot melt.
So, the warm water will cool down to 0oC melting some of theice, say m' gram.
Heat gained by the ice melted, Q" = m.L = 76 m cal.
Heat lost by the warm water, Q' = 400x24 = 9600 cal.
These are equal.Q'' = Q'
76 m = 9600
m = 9600/76 = 126.32 g
Final temp is ofcourse, 0oC, as some ice isstill not melted.