Choose the TRUE statement about the effect of the presence of a catalyst on reaction rate. In the presence of a catalyst, the reaction rate increases for exothermic reactions and decreases for endothermic reactions. In the presence of a catalyst, reaction rates increase for exothermic and endothermic reactions. In the presence of a catalyst, reaction rates decrease for exothermic and endothermic reactions. In the presence of a catalyst, the reaction rate decreases for exothermic reactions and increases for endothermic reactions.

Choose the TRUE statement about the effect of the presence of a catalyst on reaction rate. In the presence of a catalyst, the reaction rate increases for exothermic reactions and decreases for endothermic reactions. In the presence of a catalyst, reaction rates increase for exothermic and endothermic reactions. In the presence of a catalyst, reaction rates decrease for exothermic and endothermic reactions. In the presence of a catalyst, the reaction rate decreases for exothermic reactions and increases for endothermic reactions.

Chemistry: Matter and Change

1st Edition

ISBN:9780078746376

Author:Dinah Zike, Laurel Dingrando, Nicholas Hainen, Cheryl Wistrom

Publisher:Dinah Zike, Laurel Dingrando, Nicholas Hainen, Cheryl Wistrom

Chapter17: Chemical Equilibrium

Section: Chapter Questions

Problem 1STP

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. Explain what it means that a reaction has reached a state of chemical equilibrium. Explain why equilibrium is a dynamic state: Does a reaction really “stop” when the system reaches a state of equilibrium? Explain why, once a chemical system has reached equilibrium, the concentrations of all reactants remain constant with time. Why does this constancy of concentration not contradict our picture of equilibrium as being dynamic? What happens to the rates of the forward and reverse reactions as a system proceeds to equilibrium from a starting point where only reactants are present?
For each of the changes listed will the rate of the following chemical reaction increase, decrease, or remain the same? Fe(s)+2HCl(aq)FeCl2(aq)+H2(g) a. the concentration of HCl is decreased b. the iron is ground into a powder c. a catalyst is added to the reaction mixture d. the temperature of the solution is decreased
Will each of the changes listed increase or decrease the rate of the following chemical reaction? N2+3H22NH3 a. Adding some N2 to the reaction mixture b. Raising the temperature of the reaction mixture c. Removing a catalyst present in the reaction mixture d. Removing some H2 from the reaction mixture
Classify each of the following statements as true or false. aSome equilibria depend on a steady supply of a reactant in order to maintain the equilibrium. bBoth forward and reverse reactions continue after equilibrium is reached. cEvery time reactant molecules collide, there is a reaction. dPotential energy during a collision is greater than potential energy before or after the collision. eThe properties of a transition state are between those of the reactants and products. fActivation energy is positive for both the forward and reverse reactions. gKinetic energy is changed to potential energy during a collision. hAn increase in temperature speeds the forward reaction but slows the reverse reaction. iA catalyst changes the steps by which a reaction is completed. jAn increase in concentration of a substance on the right-hand side of an equation speeds the reverse reaction rate. kAn increase in the concentration of a substance in an equilibrium increases the reaction rate in which the substance is a product. lReducing the volume of a gaseous equilibrium shifts the equilibrium in the direction of fewer gaseous molecules. mRaising temperature results in a shift in the forward direction of an endothermic equilibrium. nThe value of an equilibrium constant depends on temperature. oA large K indicates that an equilibrium is favored in the reverse direction.
Apply collision theory to explain why increasing the concentration of a reactant usually increases the reaction rate.
Indicate whether or not each of the following changes would affect the value of a systems equilibrium constant. a. Removal of a reactant from the equilibrium mixture b. Decrease in the systems total pressure c. Decrease in the systems temperature d. Addition of a catalyst to the equilibrium mixture
Write equilibrium constant expressions for the following generalized reactions. a. 2X(g)+3Y(g)2Z(g) b. 2X(g)+3Y(s)2Z(g) c. 2X(s)+3Y(s)2Z(g) d. 2X(g)+3Y(g)2Z(s)
Substances that poison a catalyst pose a major concern for many engineering designs, including those for catalytic converters. One design option is to add materials that react with potential poisons before they reach the catalyst. Among the commonly encountered catalyst poisons are silicon and phosphorus, which typically form phosphate or silicate ions in the oxidizing environment of an engine. Group 2 elements are added to the catalyst to react with these contaminants before they reach the working portion of the catalytic converter. If estimates show that a catalytic converter will be exposed to 625 g of silicon during its lifetime, what mass of beryllium would need to be included in the design?
How do chemists envision reactions taking place in terms of the collision model for reactions? Give an example of a simple reaction and how you might envision the reaction’s taking place by means of a collision between the molecules.
Indicate whether or not each of the following changes would affect the value of a systems equilibrium constant. a. Addition of a product to the equilibrium mixture b. Increase in the systems total pressure c. Increase in the systems temperature d. Addition of both a reactant and a product to the equilibrium mixture
For each of the changes listed will the rate of the following chemical reaction increase, decrease, or remain the same? Cu(s)+H2SO4(aq)CuSO4(aq)+H2(g) a. the concentration of H2SO4 is increased b. the copper is ground into a powder c. the mixture is stirred rapidly d. the temperature of the solution is increased
Apply collision theory to explain why powdered zinc reacts to form hydrogen gas faster than large pieces of zinc when both are placed in hydrochloric acid solution.