Predicting Whether a Reaction Will Occur

In this chapter we will study some common types of reactions that take place in water, and we will become familiar with some of the driving forces that make these reactions occur. We will also learn how to predict the products for these reactions and how to write various equations to describe them. 

Developing a photo involves several aqueous chemical reactions. 

I AIM To learn about some of the factors that cause reactions to occur. 

In this text we have already seen many chemical reactions. Now let s consider an important question Why does a chemical reaction occur What causes reactants to want to form products As chemists have studied reactions, they have recognized several tendencies in reactants that drive them to form products. That is, there are several driving forces that pull reactants toward products—changes that tend to make reactions go in the direction of the arrow. The most common of these driving forces are 

When two or more chemicals are brought together, if any of these things can occur, a chemical change (a reaction) is likely to take place. Accordingly, when we are confronted with a set of reactants and want to predict 

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Many times, we can use thermodynamics to predict whether a reaction will occur spontaneously, but it gives very little information about the speed at which a reaction occurs. Kinetics is the study of the speed of reactions. It is largely an experimental science. Some general qualitative ideas about reaction speed may be applied, but accurate quantitative relationships require that we collect experimental data. 

The standard free-energy change for a reaction is also useful for predicting whether a reaction will occur under standard conditions. If AG° < 0, the reaction will occur spontaneously provided standard conditions prevail if AG° > 0, the reaction will not occur by itself. It is AG, however, that determines whether or not a reaction will occur under conditions different from the standard state, such as those existing within a cell, for two reasons. 

The change in energy of a reaction system is one of two factors that allow chemists to predict whether a reaction will occur spontaneously and to explain how it occurs. The randomness of the particles in a system is the second factor affecting whether a reaction will occur spontaneously. 

Predict whether a reaction will occur in each of the following cases. If so, write a net ionic equation for the reaction. 

Given the relative strengths of Brpnsted-Lowry acids, predict whether a reaction will occur between one acid and the conjugate base of another. (Question 3.2)... 

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