Which of the following statements is false? OA A catalyst increases the rate of a reaction, but is not consumed. OB. A catalyts stay unchanged during a chemical reaction. oc A catalyst takes part in a reaction and undergoes chemical change. OD A catalyst alters the mechanism of reaction. OE. A catalyst alters the activation energy.

a What happens to a reaction rate as temperature drops? Give two explanations for the change. State which one is more important and explain why. b How does a catalyst affect reaction rates? c Compare reaction rates when a given reactant concentration is high with the rate when the concentration is low. Explain the difference.

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 is it possible for a catalyst to give products from a reaction mixture that are different from those obtained when no catalyst or a different catalyst is used? Give an example.

What is the role of the activated complex in a chemical reaction?

How does an increase in temperature affect rate of reaction? Explain this effect in terms of the collision theory of the reaction rate.

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.

If a textbook defined a catalyst as "a substance that increases the rate of a reaction," would that definition be adequate?

A reaction takes place between an acid and 0.5grams of solid magnesium ribbon. Another reaction takes place between an acid and 0.5grams of powdered magnesium. Which statement is true? a.The powdered magnesium reacts faster because the activation energy has been lowered. b.The magnesium strip reacts faster because it has a higher concentration of magnesium. c.The powdered magnesium reacts faster because it has a greater surface area. d.The magnesium strip reacts faster because it will create a higher temperature once the reaction starts.