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Chapter 17. Part 2. Saharan Desert. Saharan Oasis. Sahara was once fertile grasslands. Reversible Reactions . Most chemical reactions are reversible. Depending on conditions. H 2 O(l) H 2 O(g) . Evaporation and condensation are reversible processes.
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Chapter 17 Part 2
Reversible Reactions • Most chemical reactions are reversible. • Depending on conditions.
H2O(l) H2O(g) • Evaporation and condensation are reversible processes. • An equilibrium occurs when two opposing processes occur at the same rate.
H2O(l) H2O(g) • Evaporation and condensation are reversible processes. • An equilibrium occurs when two opposing processes occur at the same rate. • At equilibrium the concentrations of the substances involved in the reaction will remain constant. • [ ] = concentration.
Vapor Pressure • Suppose we conduct an experiment in which we place a quantity of ethanol (C2H5OH) in an evacuated, closed container (a). • The ethanol will quickly begin to evaporate. • The pressure exerted by the vapor will begin to increase. • After a short time the pressure will attain a constant value, called the vapor pressure of ethanol (b).
Vapor Pressure • At any given temperature, for a particular substance, there is a pressure at which the gas of that substance is in equilibrium with its liquid or solid form. This is the vapor pressure of that substance at that temperature. • The equilibrium vapor pressure is an indication of a liquid's evaporation rate. • A substance with a high vapor pressure at normal temperatures has a high rate of evaporation and is often referred to as volatile.
Attractive Forces Two types of attractive forces are: • Intramolecular forces • Intermolecular forces
Intramolecular Forces • Intramolecular forces = attractive forces that hold particles together using ionic, covalent, or metallic bonds • Intra means “within” • Intramolecular forces = bonds
Intermolecular Forces(Van der Waals forces) • Inter means “between” • Intermolecular forces are forces between molecules • Larger polar molecules have greater Van der Waals forces.