Given an ice w/ a temp. of -10°c and mass of 245g. What is the enthalpy when it becomes steam at 120°c?
there are several stages , each with its own specific heat
... along with two phase changes ... fusion and vaporization
heat ice , melt ice , heat water , boil water , heat steam
Can you tell us what you think?
Im quite unsure of my answers because I find it hard t see the molar heat capacity of each water in different phases. Because we are required to use the latent heat of fusion and evaporation with units of KJ/mol
To calculate the enthalpy change when ice is heated to become steam, we need to account for the three phases involved: the heating of the ice from -10°C to 0°C (solid to liquid phase change), the heating of the water from 0°C to 100°C (liquid phase), and the heating of the steam from 100°C to 120°C (gas phase).
To calculate the enthalpy changes for each phase, we need the heat capacity and phase change enthalpy values.
1. Heating the ice from -10°C to 0°C (solid to liquid phase change):
The specific heat capacity of ice is 2.09 J/g·°C, and the heat required to raise the temperature can be calculated using the formula:
Q = mcΔT, where Q is the heat energy, m is the mass, c is the specific heat capacity, and ΔT is the temperature change.
For this phase, the temperature change is 0°C - (-10°C) = 10°C.
The heat energy is Q = (245 g) * (2.09 J/g·°C) * (10°C) = 5094.5 J
2. Heating the water from 0°C to 100°C (liquid phase):
The specific heat capacity of water is 4.18 J/g·°C.
The temperature change is 100°C - 0°C = 100°C.
The heat energy is Q = (245 g) * (4.18 J/g·°C) * (100°C) = 102235 J
3. Heating the steam from 100°C to 120°C (gas phase):
The specific heat capacity of steam is 2.03 J/g·°C.
The temperature change is 120°C - 100°C = 20°C.
The heat energy is Q = (245 g) * (2.03 J/g·°C) * (20°C) = 10037 J
To obtain the total enthalpy change, we sum the enthalpy changes for each phase:
Enthalpy change = Q1 + Q2 + Q3
= 5094.5 J + 102235 J + 10037 J
= 117366.5 J
Therefore, the enthalpy change when the ice becomes steam at 120°C is 117366.5 J.