au The internal pressure of a gas, π = av), is a measure of intermolecular forces, because it indicates a change in internal energy as the molecules get closer or further apart, without temperature changing. au = a Calculate the change in internal Vm 2. T i) Using the van der Waals equation of state, T = energy, AU, when 1.5 mols of acetone (a 1 = 16 l²atm/mol²), expands from 2 liters to 5 liters at a constant temperature. ii) Would this change in internal energy be greater or smaller for an ideal gas? Why?
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
The internal pressure of a gas is expressed as:
For a real gas or van der Waals gas, the internal pressure is supposed to have the following expression:
In order to find the total internal energy change during a particular range of volume change, we need to integrate the expression.
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