Chemistry Unit 5 Practice Test

Which of the following equations is used to describe reaction rates? a. delta[reactant or product]/deltaTime b. Sproducts-Sreactants c. pV=nRT d. deltaH - T*deltaS

What is the equilibrium expression for 2NO + Br2 <--> 2NOBr? a. [NOBr]2/[NO]2[Br2] b. [NO]2[Br2]/[NOBr]2 c. [NOBr]2/[NO2][Br]2

Which of the following describes the effects of changes in concentration on a chemical system in equilibrium? a. Gibbs free energy b. chemical equilibrium c. reaction rate d. Le Chatelier's principle

A chemical reaction is at equilibrium. What will be the effect if more of the product is added? a. The reaction will shift to the right (toward the products). b. There will be no effect; the reaction will stay at equilibrium. c. The reaction will shift to the left (toward the reactants).

What kind of reaction occurs when the entropy change of an endothermic reaction is negative? a. reversible b. irreversible c. non-spontaneous at equilibrium d. spontaneous

Molecules involved in a chemical reaction must meet to react. What is this concept called? a. entropy b. collision theory c. reaction rate d. enthalpy

Which of the following is likely to occur if more reactants are added to a reaction that is at chemical equilibrium? a. The reaction will shift to the right (toward the products). b. There will be no effect; the reaction will stay at equilibrium. c. The reaction will shift to the left (toward the reactants).

Which of the following represents an increase in entropy? a. green food coloring diffusing through cookie dough b. people arranging 80 cans into a pyramid c. one end of a rod of steel getting warmer while the other end gets cooler d. someone arranging a deck of cards in order from aces (low) to kings (high)

What type of reaction is will occur if ∆H is negative and there are no significant entropy effects? a. endothermic reaction b. redox reaction c. spontaneous reaction d. acid-base reaction

What is a negative Gibbs free-energy value an indication of? a. an enzymatic reaction b. an equilibrium reaction c. a reversible reaction d. a spontaneous reaction

What term refers to the difference between the energy of the transition state and the energy of the reactants? a. energy of entropy b. energy of enthalpy c. reaction rate d. activation energy

What can you calculate if you know the concentration of a reaction's products and reactants, as well as the coefficients of each in the balanced equation? a. the rate of the reaction b. Gibbs free energy c. the entropy of the reaction d. the equilibrium constant

Adding an inhibitor to a chemical reaction will have which of the following effects on the reaction? a. The inhibitor will have no effect on the rate of the reaction. b. The inhibitor will increase the rate of reaction. c. The inhibitor will initially increase the rate of the reaction and then decrease it. d. The inibitor will decrease the rate of the reaction.

Consider the reaction 2NaN3 --> 2Na + 3N2, which is the first reaction that occurs when an air bag expands in a car undergoing a collision. This reaction happens very quickly, as you might suspect. A graph showing the amount of nitrogen gas (N2) could be best described as which of the following? a. The graph line's general trend is absolutely horizontal. b. The graph line's general trend is increasing from left to right. c. The graph line's general trend is nearly horizontal. d. The graph line's general trend is decreasing from left to right.

Changes in which of the following do not shift the equilibrium of a chemical system? a. temperature b. pressure c. time d. concentration

What does the formula ∆H - T∆S determine? a. Le Châtelier's principle b. Gibbs free energy c. entropy d. enthalpy

What happens to a catalyst as a result of its involvement in a chemical reaction? a. In is not consumed. b. It is consumed. c. It changes to something else. d. It slows a chemical reaction.

What is the equation for the equilibrium constant for this equation? CO + 3H2 <---> CH4 + H2O a. [CH4][H2O]/[CO][H2]3 b. [H2O][H2]/[CH4][CO] c. [CH]4[H2O]/[H2]3 d. [CO][H2]3/[CH4][H2O]

Which of the following factors does not increase the rate of a reaction? a. increasing the concentration of the reactants b. adding an effective catalyst to the system c. decreasing the temperature of the system d. increasing the surface area of the reactants

What happens in a reaction if it is at chemical equilibrium? a. The ration of the products to reactants remains constant over time. b. All of the products are used up. c. The amount of the reactant is constantly decreasing. d. There are no reactants in the system.