An increase in the concentration of a product will lead to a decrease in the amounts of all products and an increase in the amounts of all reactants. In both cases, there will be a net increase in the total amount of the added component, but the increase will be less than the amount added. The effect of changing the volume:. In considering volume changes, we must pay close attention to the phases that are affected by the change. If there are aqueous, solid, and gas phases in a container, changing the volume of the container only changes the volume of the gas phase.
Adding water to the container obviously increases the volume of the aqueous phase, but the effect on the gas phase depends on whether the addition is at constant volume or constant pressure. If the addition is at constant pressure the volume of the gas phase is not changed , but if the volume of the container is kept constant the volume of the gas phase decreases as the volume of the aqueous phase increases. Addition of an immiscible liquid such as mercury has no effect at constant pressure , but decreases the volume of the gas phase if the volume of the container is constant.
Addition of an inert gas has no effect if the volume of the container is constant, but increases the volume of the gas phase if the pressure is constant.
Changing the volume of a phase changes the concentrations of all components in that phase, reactants and products. The net effect is determined by the difference in the number of molecules of reactants and products from the balanced reaction in that phase. If the balanced reaction shows the same number of moles of reactants and products in the phase being changed, there is no effect on the equilibrium.
Heat of Reaction The Heat of Reaction is the change in the enthalpy of a chemical reaction. Problems If heat is added to a phase change equation at equilibrium from solid to liquid, which way will the reaction proceed? Explain how to determine if a reaction is exothermic or endothermic.
Solutions The reaction will proceed towards the liquid phase. Heat is on the reactant side of the equation. Heat is released in a combustion reaction. Lowering temperature will shift equilibrium left, creating more liquid water. The higher the temperature goes, the further the balance at equilibrium shifts back toward reactants. A famous example is the reaction between hydrogen and nitrogen to make ammonia.
The reaction is so slow at room temperature that nothing happens. If you increase the temperature to speed the reaction up, however, the balance at equilibrium shifts back towards reactants, and very little ammonia is produced. Based in San Diego, John Brennan has been writing about science and the environment since How to Calculate the Grams of Reactants in a Product.
How to Write a Chemical Formula. What Happens in Exergonic Chemical Reactions? How to Calculate an Isolated Yield. For the previous equation, does the equilibrium favor the products or the reactants? Is this an exothermic or endothermic reaction? Because the K value decreases with an increase in temperature, the reaction is an exothermic reaction. In the initial reaction, the energy given off is negative and thus the reaction is exothermic.
However, an increase in temperature allows the system to absorb energy and thus favor an endothermic reaction; the equilibrium will shift to the left.
0コメント