CHEM120 Lecture 11: c123-module1-w18

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indigoeel216

20 Mar 2018

School

University of Waterloo

Department

Chemistry

Course

CHEM120

Professor

Carey Bissonnette

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Document Summary

Module 1: energy, entropy, and spontaneous change page 1 of 62. In this module, we focus our attention on a system which undergoes some transformation between two states a and b: It may occur in one step or may involve many steps. In a physical change, there is no change in the chemical composition of the system. However, there may be changes in temperature, pressure, volume, density, or the phase (state of aggregation). Examples of physical transformations include heating, cooling, expansion, compression, and phase changes, such as vaporization, fusion (melting), and sublimation. In a chemical change, the chemical composition of the system is changed by a chemical reaction. Energy is conserved. (this is the first law of thermodynamics. ) Entropy increases. (this is the second law of thermodynamics. ) These statements illustrate that the concepts of energy and entropy are central to understanding or predicting physical and chemical changes.

Related Questions

*This is a Chemical Engineering question, that just inst a category choice**

A 831.0 g/hr stream of liquid methyl alcohol, also called methanol, (CH3OH) at 5.80 atm and 18.0Â°C was held at constant pressure, vaporized and brought to 236.0Â°C. Assume that methyl alcohol vapor behaves ideally for the temperature range and pressure given. FIND: The rate heat must be supplied to this system, Because this is an open system and there is no change in kinetic energy, potential energy, or shaft work, the rate of heat supplied to the system is equal to the rate of change in enthalpy of the process.

The change in enthalpy is a state property, meaning that it is path independent. Since table values for the specific enthalpy of methyl alcohol at the starting and final conditions are not available, you will have to calculate the change in enthalpy as the sum of a series of steps. Because the methyl alcohol is going from a liquid to a vapor, you know that you will need to utilize the heat of vaporization at some temperature, and the heat capacity equations of the liquid, the vapor, or both. You will also need the molar mass of methyl alcohol and its specific gravity. Choose the path that will allow you to calculate the total enthalpy change given these physical constants. Calculate the sum of each step\'s specific enthalpy, and multiply this value by the molar flow rate of methyl alcohol into the process.

STRATEGY: 1. Look up the relevant physical constants of methanol. 2. Determine the proper path to take. 3. Find ?H1. 4. Find ?H2. 5. Find ?H3. 6. Find ?Htot. 7. Find ?H. 8. Find Q.