Chemistry Chapter 13 Study Guide-Test 8

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The ________ of a chemical reaction depends on several factors, including temperature and reactant concentration. rate
Molecules undergoing chemical reactions pass through untsable, short-lived _____________ __________ before assuming their final forms. ttransition states
Molecules must possesss a certain amount of kinetic energy-___ _______________________ ____________- in order to undergo a chemical reaction. the activation energy
What increases the rate of a chemical reaction by lowering the energy required for molecules to react. catalyst
Reactions that seem similar from the balanced equation often take place through dramatically different ____________ _______________________. reaction mechanisms
Surprisingly, both actions release roughly the same amount of enregy; it is the different what of the cmeical reactions however that make the world safe for candy bar eaters. rates
What is the study of rates of reactions (their speeds) and the pathway taken during the reacton (the mechanism of the reaction) chemical kinetics
Reaction rate may be defined by what equation? reaction rate = change in molar concentration/time period for change
The rate is often measured over a relatively short time interval immediately after the reactans are combined; this is known as what? initial rate of reaction
The greater the frequency and the greater the energy of collision between reactant particles, the greater the rate of reaction; this concept is known as what? collision theory
On the basis of the collision theory, we would also expect the reaction rate for most reactions to depend on the positioning of the molecules-their what-when they collide? orientation
In cases where the reactants are not in the same phase--this system, the reaction rate depends on the area of contact between the phases. heterogeneous system
What is one important factor that affects the rate of chemical reactions? temperature
What is the general rule of thumb? For every 10 degree celsius rise in temperature, the reaction rate doubles.
Apparently, the higher temperature must result in a greater what of the collisions being effective to produce products? fraction
Since there is a minumum speed which will result in damage to the cars, there is also what if it is to react and do molecular change. a minimum energy that a molecule must possess
When their energy is high enough to chemically react and they are oriented properly, H2 and Br2 molecules are thought to form what and is known as this or this. short-lived, high-energy, unstable arrangement of atoms

activated complex
transition state
What is the minimum energy known as? activation energy
The type of process described above is often represented in what is known as.... reaction profile or potential energy diagram
What is a reaction in which the products are lower in energy than the reactants has a negative delta H? exothermic reaction
One in which the products are higher in energy than the reactants has a positive delta H is known as what? endothermic reaction
What is a substance that alters the rate of a chemical reaction without being consumed in the reaction. catalyst
But a catalyst cannot make an impossible reaction possible; it only does what? aids reactions that are already possible
Whereas increeasing the temperature increases the reaction rate by increasing the fraction of molecules with sufficient energy to react, a catalyst does what? increases the rate by providing an easier route which has a lower activation energy.
Since the change in heat content between reactants and products is unaffected, what is the same? delta H for catalyzed and uncatalyzed reactions
Catalysts that exist in the same phase as the reacts are known as what? homogenous catalysts
What is a catalyst that is not in the same phase as the reactants known as? heterogeneous catalyst
What means to attract one substance to the surface of a solid? adsorb
What is it called as a result? surface catalysts
What greatly reduces pollution by converting carbon monoxide, nitrogen oxides, and unburned hydrocarbons into harmless substances such as water vapor, nitrogen gas, and carbon dioxide? catalytic converters
Substances known as this are added to certain foods and medications to reduce spoilage. inhibitors
Name two effects of a catalyst on a reaction. reaction rate is more rapid
energies of products and reactants are unchanged.
A group of very important catalysts, known as this are found in living cells and organs; sometimes they are known as what? enzymes
biological catalysts

An understanding of chemistry is thus essential to the understanding of the fuctioning of a cell-an area known as what? biochemistry
To speed up reactions that are already thermodynamically favorable, the cell manufactures special protein molecules called this that serve as catalysts. enzymes
However, the presence of the enzyme catalase, the E (a) for the reaction is lowered to what, giving a rate of decomposition that is how many times greater than the uncatalyzed rate! 0.6

10 billion times
What is a series of steps which describes the way in which a reaction proceeds? reaction mechanism
Generally, one of the reactions in a proposed series will have a greater activation energy than the others and will thus occur more slowly than the others; this step is called what? rate determining step
The overall rate depends on what? on the slowest step in a series of steps
The rate depends _______ on the concetrations of 02 and HBr. only
Except in rare cases, the balanced net equation cannot be what? used to predict either the rate or the mechanism of a reaction
Collisions involving more than two particles simultaneously are not likely and the more particles involved, the less likely it is. This mechanism is not what? not very probable.
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