Given that the heat of fusion of water is -6.02 kJ>mol, the...

Name: Problem 94, Chapter 11: Chemistry: Structure and Properties
Uploaded: 2021-08-26T01:19:56-08:00
Duration: 6 min 42 s
Channel: Tianyu Li
Description: Given that the heat of fusion of water is -6.02 kJ>mol, the heat capacity of H2O(l) is 75.2 J>mol # K, and the heat capacity of H2O(s) is 37.7 J>mol # K, calculate the heat of fusion of water at -10 C.

Given that the heat of fusion of water is -6.02 kJ>mol, the heat capacity of H2O(l) is 75.2 J>mol # K, and the heat capacity of H2O(s) is 37.7 J>mol # K, calculate the heat of fusion of water at -10 C.

Key Concepts

Heat of Fusion

The heat of fusion is the energy required to change a substance from a solid to a liquid at its melting point. It quantifies the latent heat absorbed during the phase change without a change in temperature and is a crucial parameter in understanding phase transitions.

Heat Capacity

Heat capacity is a measure of the amount of energy needed to raise the temperature of a substance by one degree. For molar heat capacity, it is expressed per mole, and different phases of a substance (such as solid and liquid) have distinct heat capacities that affect how their enthalpies change with temperature.

Kirchhoff’s Law

Kirchhoff’s Law in thermochemistry describes how the enthalpy change of a reaction or phase transition can be adjusted between different temperatures by accounting for the difference in heat capacities of the reactants and products. This law is essential when calculating enthalpy changes at temperatures other than the standard reference temperature.

Temperature Dependence of Enthalpy

The enthalpy change of a process is not constant but varies with temperature. To determine the enthalpy at a temperature different from the standard, it is necessary to integrate the difference in heat capacities over the temperature range, thereby capturing the temperature dependence of the reaction or phase transition enthalpy.

Transcript

00:03 Okay, so this is a question about the heat of furin.

00:08 So it actually gives the heat of the fueling is water, and it didn't give the temperature, but we already know that for water, it actually melt at zero degree c.

00:21 So we actually can write down that at zero degree c, the heat of the fueling is actually basically the water, which is a solid phase at 0 degree c and forms the water as a liquid phase, but also at 0 degree c.

00:50 And we know the heat of urine given here, we use hf1 to indicate equals to minus.

01:01 This is not minus right it's actually 6 .02 kilojou per more.

01:15 I don't think that's a minor sign because for water to become liquid water it actually is an anothermic reaction so the heat furean should be a positive sign.

01:32 And also this question asks us to calculate the heat of fulium of water and minus degree c.

01:46 So we can also write down the reactions.

01:49 It's a solid phase, the minus degree c, and converts into the water, liquid phase, and the minus 10 degree c.

02:05 And actually wants us to calculate the heat of fuel.

02:13 How can we do that? so you can see for both states, the water, solid phase, decrease, the temperature and liquid phase also decrease the temperature.

02:27 So then we can actually make two artificial equations.

02:31 So let's just write down this as equation one, the equation two.

02:36 How about equation three, right? when we have a water from s equal to zero degrees c becomes a solid water but becomes minus degree c...

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