Factors Affecting Chemical Equilibrium

Le Chfitelier s principle states that if a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress. For example, consider the equilibrium system in Example Problem 18-3. 

Note that changing the volume of the reaction vessel causes no shift in the equilibrium when the number of moles of product gas equals the number of moles of reactant gas an example is the equilibrium H2(g) + Br2(g) 2HBr(g) discussed in Section 18.1. 

Use Le ChStelier s principle to predict how each of the following changes would affect this equilibrium. 

How would decreasing the volume of the reaction vessel affect these equilibria  

The forward reaction releases heat, so you can consider heat as a product in the forward reaction and a reactant in the reverse reaction. 

I Describe how various factors affect chemical equilibrium. 

I Explain how Le Chatelier s principle applies to equilibrium systems. 

When changes are made to a system at equilibrium, the system shifts to a new equilibrium position. 

Real-World Reading Link When demand for a product equals the available supply, the price remains constant. If demand exceeds supply, the price of the product increases. The price becomes constant again when supply and demand regain a state of balance. Systems at equilibrium behave in a similar way. 

Suppose the by-products of an industrial process are the gases carbon monoxide and hydrogen, and a company chemist believes these gases can be combined to produce the fuel methane (CH4). When CO and H2 are placed in a closed vessel at 1200 K, this exothermic reaction (AH = —06.5 kj) establishes equilibrium (Equilibrium Position 1). 

When the industrial chemist places CO and H2 in a closed reaction vessel at 1200 K, the reaction establishes this equilibrium position (equilibrium position 1). 

Inserting these concentrations into the equilibrium expression gives an equilibrium constant equal to 3.933. 

Unfortunately, a methane concentration of 0.05900 mol/L in the equilibrium mixture is too low to be of any practical use. Can the chemist change the equilibrium position and thereby increase the amount of methane  

In 1888, the French chemist Henri-Louis Le ChStelier discovered that there are ways to control equilibria to make reactions, including this one, more productive. He proposed what is now called Le Chatelier s principle If a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress. A stress is any kind of change in a system at equilibrium that upsets the equilibrium. You can use Le Chatelier s principle to predict how changes in concentration, volume (pressure), and temperature affect equilibrium. Changes in volume and pressure are interrelated because decreasing the volume of a reaction vessel at constant temperature increases the pressure inside. Conversely, increasing the volume decreases the pressure. 

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In this paper we explore factors beyond the well known molecular weight and chemical effects on the dissolution kinetics of polymers. In our studies we show that factors controlling solvent mobility in polymeric matrices, such as stereo chemistry (tacticity), processing (heat treatment) and solvent molecular size may affect the dissolution kinetics of polymers far more strongly than factors affecting the equilibrium solubility, e.g. molecular weight of the polymer. 

Knowing the factors that affect chemical equilibrium has great practical value for industrial applications, such as the synthesis of ammonia. The Haber process for synthesizing ammonia from molecular hydrogen and nitrogen uses a heterogeneous catalyst to speed up the reaction (see p. 540). Let us look at the equilibrium reaction for ammonia synthesis to determine whether there are factors that could be manipulated to enhance the yield. 

The electrostatic part of these models comprises a Boltzmann-type factor affecting the equilibrium constants, as in chemical models for minerals (Equation 11.16) ... 

Factors That Affect Chemical Equilibrium Changes in concentration can affect the position of an equilibrium state—that is, the relative amounts of reactants and products. Changes in pressure and volume may have the same effect for gaseous systems at equilibrium. Only a change in temperature can alter the value of equilibrium constant. A catalyst can establish the equilibrium state faster by speeding the forward and reverse reactions, but it can change neither the equilibrium position nor the equilibrium constant. 

SECTION 1S.S Factors That Affect Chemical Equilibrium... 

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