The ________ of a chemical reaction depends on several factors, including temperature and reactant concentration. |
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rate |
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Molecules undergoing chemical reactions pass through untsable, short-lived _____________ __________ before assuming their final forms. |
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ttransition states |
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Molecules must possesss a certain amount of kinetic energy-___ _______________________ ____________- in order to undergo a chemical reaction. |
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the activation energy |
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What increases the rate of a chemical reaction by lowering the energy required for molecules to react. |
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catalyst |
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Reactions that seem similar from the balanced equation often take place through dramatically different ____________ _______________________. |
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reaction mechanisms |
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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. |
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rates |
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What is the study of rates of reactions (their speeds) and the pathway taken during the reacton (the mechanism of the reaction) |
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chemical kinetics |
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Reaction rate may be defined by what equation? |
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reaction rate = change in molar concentration/time period for change |
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The rate is often measured over a relatively short time interval immediately after the reactans are combined; this is known as what? |
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initial rate of reaction |
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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? |
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collision theory |
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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? |
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orientation |
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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. |
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heterogeneous system |
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What is one important factor that affects the rate of chemical reactions? |
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temperature |
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What is the general rule of thumb? |
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For every 10 degree celsius rise in temperature, the reaction rate doubles. |
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Apparently, the higher temperature must result in a greater what of the collisions being effective to produce products? |
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fraction |
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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. |
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a minimum energy that a molecule must possess |
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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. |
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short-lived, high-energy, unstable arrangement of atoms
activated complex transition state |
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What is the minimum energy known as? |
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activation energy |
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The type of process described above is often represented in what is known as.... |
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reaction profile or potential energy diagram |
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What is a reaction in which the products are lower in energy than the reactants has a negative delta H? |
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exothermic reaction |
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One in which the products are higher in energy than the reactants has a positive delta H is known as what? |
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endothermic reaction |
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What is a substance that alters the rate of a chemical reaction without being consumed in the reaction. |
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catalyst |
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But a catalyst cannot make an impossible reaction possible; it only does what? |
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aids reactions that are already possible |
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Whereas increeasing the temperature increases the reaction rate by increasing the fraction of molecules with sufficient energy to react, a catalyst does what? |
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increases the rate by providing an easier route which has a lower activation energy. |
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Since the change in heat content between reactants and products is unaffected, what is the same? |
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delta H for catalyzed and uncatalyzed reactions |
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Catalysts that exist in the same phase as the reacts are known as what? |
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homogenous catalysts |
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What is a catalyst that is not in the same phase as the reactants known as? |
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heterogeneous catalyst |
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What means to attract one substance to the surface of a solid? |
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adsorb |
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What is it called as a result? |
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surface catalysts |
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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? |
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catalytic converters |
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Substances known as this are added to certain foods and medications to reduce spoilage. |
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inhibitors |
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Name two effects of a catalyst on a reaction. |
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reaction rate is more rapid energies of products and reactants are unchanged. |
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A group of very important catalysts, known as this are found in living cells and organs; sometimes they are known as what? |
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enzymes biological catalysts
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An understanding of chemistry is thus essential to the understanding of the fuctioning of a cell-an area known as what? |
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biochemistry |
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To speed up reactions that are already thermodynamically favorable, the cell manufactures special protein molecules called this that serve as catalysts. |
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enzymes |
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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! |
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0.6
10 billion times |
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What is a series of steps which describes the way in which a reaction proceeds? |
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reaction mechanism |
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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? |
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rate determining step |
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The overall rate depends on what? |
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on the slowest step in a series of steps |
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The rate depends _______ on the concetrations of 02 and HBr. |
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only |
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Except in rare cases, the balanced net equation cannot be what? |
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used to predict either the rate or the mechanism of a reaction |
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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? |
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not very probable. |
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