Problem 20 - Chemistry An Atoms First Approach

Question

Which of the following statements is(are) true? Correct the false statement(s). a. When a reactant is added to a system at equilibrium at a given temperature, the reaction will shift right to reestablish equilibrium. b. When a product is added to a system at equilibrium at a given temperature, the value of \(K\) for the reaction will increase when equilibrium is reestablished. c. When temperature is increased for a reaction at equilibrium, the value of \(K\) for the reaction will increase. d. When the volume of a reaction container is increased for a system at equilibrium at a given temperature, the reaction will shift left to reestablish equilibrium. e. Addition of a catalyst (a substance that increases the speed of the reaction) has no effect on the equilibrium position.

Step-by-Step Solution

Answer

The correct statements are: a. True - When a reactant is added, the reaction will shift right to reestablish equilibrium. b. False - The value of equilibrium constant K remains constant at a given temperature. c. Cannot classify - The effect on K depends on the nature of the reaction (exothermic or endothermic). d. False - The system will shift its position to the side with more moles of gas, not necessarily left. e. True - Addition of a catalyst has no effect on the equilibrium position.

Step 1: Statement a

When a reactant is added to a system at equilibrium, according to Le Châtelier's principle, the equilibrium will shift in the direction that consumes the added reactant. In this case, the equilibrium will shift to the right since the reaction moves forward consuming reactants and producing products. So, the statement is true.

Step 2: Statement b

Adding a product to a system at equilibrium will cause the system to respond according to Le Châtelier's principle. The system will shift its position in the direction where the product is consumed, in this case, by moving the reaction to the left (a reverse reaction). However, the value of the equilibrium constant K remains constant at a given temperature, so the statement is false.

Step 3: Statement c

The effect of temperature change on the equilibrium constant depends on the nature of the reaction (exothermic or endothermic). For an endothermic reaction, increasing the temperature will favor the forward reaction and hence increase the value of K. For an exothermic reaction, increasing the temperature will favor the reverse reaction and hence decrease the value of K. Since the statement does not specify the type of reaction, it is not possible to classify it as either true or false.

Step 4: Statement d

When the volume of the reaction container is increased, the system will respond by shifting the equilibrium position to the side with more moles of gas. It does not specify if more moles are on the left or right side of the reaction. So, we can't say whether the reaction necessarily shifts left or right. Thus, the statement is false.

Step 5: Statement e

The addition of a catalyst speeds up the reaction rate for both the forward and reverse reactions. A catalyst lowers the activation energy for the reaction, but it doesn't change the equilibrium constant or the equilibrium position for the reaction. Therefore, the statement is true.