Suppose that 21.85 g of ice at -14.8°C is placed in 65.08 g of water at 93.0°C in a perfectly insulated vessel?
Calculate the final temperature. (The molar heat capacity for ice is 37.5 J K-1 mol-1 and that for liquid water is 75.3 J K-1 mol-1. The molar enthalpy of fusion for ice is 6.01 kJ/mol.
This is an energy balance problem. With a perfectly insulated container, all you're doing is adding up the energy at the first state and setting it equal to the second state where all of your water is at a constant temperature.
Judging by the relative masses and temperatures of the ice and water, the end product will be in the liquid phase.
We can simply solve for the final temperature, T, by setting the heat lost from water to equal to the heat gained by the ice
Heat gained by ice = heat to bring ice to 0 C + heat to melt ice + heat to bring cold water to final temperature
Heat lost by water = heat to bring water to final temperature
First, calculate the heat required to bring the ice to 0 degrees C: q = m*cp*dT = (21.85 g ice/(18 g/mol water))*(37.5 J/K/mol)*(14.8 K) = 673.7 J
Then, the additional heat to melt it is q = m*dH = (21.85 g ice/(18 g/mol water))*(6010 J/mol) = 7295.5 J
{So the total energy to bring the ice to liquid water at 0 C is 7969.2 J
As a check of the assumption that the end product is liquid, subtract that energy from the liquid water:
q = -7969.2 J = m*cp*dT = (65.08 g / 18 g/mol)*(75.3 J/mol/K)*dT; dT = -29.27 K : it will be liquid}
For a final temperature of Tf, the heat to raise the cold water is q = m*cp*dT = (21.85 g ice/(18 g/mol water))*(75.3 J/K/mol)*(Tf - 0)
The heat lost by the warm water, in total, is q = m*cp*dT = (65.08 g / 18 g/mol)*(75.3 J/mol/K)*(93.0 - Tf)
Final equation is (21.85 g ice/(18 g/mol water))*(37.5 J/K/mol)*(14.8 K) +(21.85 g ice/(18 g/mol water))*(6010 J/mol) + (21.85 g ice/(18 g/mol water))*(75.3 J/K/mol)*(Tf - 0) = (65.08 g / 18 g/mol)*(75.3 J/mol/K)*(93.0 - Tf)
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Verified answer
This is an energy balance problem. With a perfectly insulated container, all you're doing is adding up the energy at the first state and setting it equal to the second state where all of your water is at a constant temperature.
Judging by the relative masses and temperatures of the ice and water, the end product will be in the liquid phase.
We can simply solve for the final temperature, T, by setting the heat lost from water to equal to the heat gained by the ice
Heat gained by ice = heat to bring ice to 0 C + heat to melt ice + heat to bring cold water to final temperature
Heat lost by water = heat to bring water to final temperature
First, calculate the heat required to bring the ice to 0 degrees C: q = m*cp*dT = (21.85 g ice/(18 g/mol water))*(37.5 J/K/mol)*(14.8 K) = 673.7 J
Then, the additional heat to melt it is q = m*dH = (21.85 g ice/(18 g/mol water))*(6010 J/mol) = 7295.5 J
{So the total energy to bring the ice to liquid water at 0 C is 7969.2 J
As a check of the assumption that the end product is liquid, subtract that energy from the liquid water:
q = -7969.2 J = m*cp*dT = (65.08 g / 18 g/mol)*(75.3 J/mol/K)*dT; dT = -29.27 K : it will be liquid}
For a final temperature of Tf, the heat to raise the cold water is q = m*cp*dT = (21.85 g ice/(18 g/mol water))*(75.3 J/K/mol)*(Tf - 0)
The heat lost by the warm water, in total, is q = m*cp*dT = (65.08 g / 18 g/mol)*(75.3 J/mol/K)*(93.0 - Tf)
Final equation is (21.85 g ice/(18 g/mol water))*(37.5 J/K/mol)*(14.8 K) +(21.85 g ice/(18 g/mol water))*(6010 J/mol) + (21.85 g ice/(18 g/mol water))*(75.3 J/K/mol)*(Tf - 0) = (65.08 g / 18 g/mol)*(75.3 J/mol/K)*(93.0 - Tf)
Substituting from above, 7969.2 J + 91.4*Tf = 25319.4 J - 272.25*Tf
Tf = 47.7 C
State 1) h = sum(mass*specific heat*temperature) = (21.85 g ice/(18 g/mol water))*(37.5 J/K/mol)*(273.15-14.8 K) + (65.08 g water/(18 g/mol water))*(75.3 J/K/mol)*(273.15 + 93.0)
h_1 = 11760 J + 99685 J =