Chemistry Energy Changes and Rates of Reaction Expectations

bonds broken -> bonds made energy absorbed < energy released

exothermic reaction - system releases energy

the further away the electrons are from the nucleus, what is the effect of the potential energy?

greater potential energy

this is the energy possessed while moving

kinetic energy

this refers to the number of reactant particles involved in an elementary reaction

molecularity

this is a type of kinetic energy; which is the energy required to protons and neutrons in a nucleus

nuclear bonding energy

this is a type of kinetic energy; which how energy can move from the source out; through electromagnetic waves

radiant energy

name and describe the 4 steps of a heterogeneous catalyst.

1. ADSORPTION AND ACTIVATION OF REACTANTS some reactant bonds broken, others weakened; weak covalent bonds form between catalyst and reactants 2. MIGRATION OF ADSORBED REACTANTS TOWARD EACH OTHER reduced energy of collision; better orientation of reactants 3. REACTION OF ADSORBED OF THE PRODUCTS 4. ESCAPE OR DESORPTION OF THE PRODUCTS product's bonding capacity no longer compatible with the catalyst.

describe the action of heterogeneous inorganic catalysts in a catalyzed reaction

a heterogeneous catalysts exists in a phase that's different from the phase of the reaction it catalyzes. the action involves 4 steps: adsorption and activation of reactants; migration of adsorbed reactants towards each other; reaction of adsorbed of the products; escape or desorption of the products

describe the action of homogeneous inorganic catalysts in a catalyzed reaction

a homogeneous catalyst exists in the same phase of the reactants. they are most often associated with reactions of gases and with reactions in solutions. they become part of a reaction intermediate, then are regenerated.

use the transition state theory to account for activation energy

activation energy of a reaction is the minimum collision energy that is required for a successful reaction. transition state theory is used to explain what happens when molecules collide in a reaction. it examines the transition, or change, from reactants to products. the kinetic energy of the reactants is transferred to potential energy as the reactants collide, due to the law of conservation of energy. the top of the activation energy barrier on a potential energy diagram represents the transition state of the reaction. the chemical species that exists at the transition state is the activated complex, which is a transitional species that's neither product nor reactant.

examples of controlled reactions (e.g. campfires)

add and remove wood, controlling rate of reaction, greater amount of wood slower reaction rate, less amount of wood faster reaction rate, also amount of surface area effects reaction rate - greater surface area - greater reaction rate

name 3 sources of error

adhesion to graduated cylinder during measure of solutions which were transferred into the beaker, reducing the actual amount of substance used, and thus less energy resulting from reaction. energy loss to thermometer, stirring rod, and to breaker, resulting in inaccurate temperature readings. ions not involved in reaction, resulting in lower temperature readings.

comparing conventional and alternative sources of energy with respect to efficiency and environmental impact (e.g. solar energy)

an energy source that is clearly renewable is solar energy. the sun will continue to radiate energy toward earth over its lifetime - many millions of years.

describe examples (2) of how the understanding of the collision theory's effect of temperature on reaction may be used "in the kitchen"

an example is to keep your food fresh; you store it in the refrigerator which decreases the rate of reaction that cause spoilage. another example is when you want your food to cook quickly, you increase the temperature of the stove, which increases the rate of reactions that take place as the food cooks

this is the average chain in the concentration of reactant or product per unit time over a give time interval

average rate of reaction

explain the role of catalysts

catalysts provide an alternative mechanism for a reaction and permits a larger fraction of reactants to have sufficient energy and to react and be properly oriented at collision. catalysts lower activation energy. they are not consumed in reaction and are put back into system available for use again and again.

this is a type of kinetic energy; which is the energy required to keep bonds between atoms together in a molecule; due to the nature of bonds

chemical energy

this is a type of a chemical system where heat and work can be exchanged in the system but matter cannot go in; and its energy can be transferred back and forth

closed system

describe characteristics of complex reactions

complex reactions form different molecules, atoms or ions; there's a change in energy of starting molecules; there's a change in geometry of starting molecules; they undergo reaction mechanisms

examples of rapid chemical reactions (e.g. explosions)

compounds are unstable, once activated it happens quickly, lower activation of energy

does a catalyst increase or decrease activation energy of reaction?

decrease

this is each step in a reaction mechanism, involves a single molecular event, such as simple collision between atoms, molecules or ions

elementary reaction

when a reaction results in a net absorption of energy, what type of reaction is this?

endothermic reaction

bonds broken -> bonds made energy absorbed > energy released

endothermic reaction - system absorbs energy

this is the ability to do "work" and "work" will be done on an object and for "work" to be done force must displace an object in the direction of the net force

energy

the concepts of enthalpy and enthalpy change

enthalpy is the energy stored within that system or substance that's available for conversion of heat, and enthalpy change is the quantity of heat that's absorbed.

describe the action of enzymes in a catalyzed reaction

enzymes are biological catalysts, they are also known as "functional" proteins. the secondary, tertiary, and quaternary structure leads to the active sites - regions where reactants (substrates) may associate with the enzyme through intermolecular forces. for synthesis reactions, substrate molecules "fit" in close proximity to each other - suitable orientation of reactant particles. for decomposition reactions, substrate "fits" into active site - stress on substrate bonds. the products shape and binding capabilities differ from those of the reactants - products detach from the active site.

when a reaction results in a net release of energy, what type of reaction is this?

exothermic reaction

explain the collision theory

for a chemical reaction to occur, reacting particles must collide with each other (no collision, no reaction). the greater the number of collisions in a give time, the greater the chance of reaction - the greater the chance, the faster and greater reaction rate. the more particles, the greater the chance of particles colliding, therefore rates should go up. the increase in surface area; increase in concentration and increase in reaction rate.

distinguish between energy production in nuclear fission and nuclear fusion

fusion is a more desirable way to produce energy than fission. the main product of fusion, helium, is relatively harmless compared with the radioactive products of fission. unfortunately, fusion is proving more difficult

BLANK = change in thermal energy

heat

thermal energy = (blank) + (blank)

heat + work

this is the rate of reaction at a particular time, and to find this using a concentration-time graph, draw a tangent line to the curve and find slope of the tangent

instantaneous rate of reaction

examples of slow chemical reactions (e.g. rusting)

iron molecules are close together, takes time for oxygen to oxidize the metal

this is a type of a chemical system where its alone; it has not interaction with its surroundings; its energy and mass remains constant

isolated system

what can the energy that's released by a chemical reaction cause?

it can power a rocket (formation of H2O)

what can the energy that's released by a nuclear reaction cause?

it can provide enough heat to fry an egg on a sidewalk (nuclear reactions in the Sun)

what can the energy that's released by a physical change cause?

it can warm your hands

whats a complex reaction?

it has a number of elementary reactions or steps

stating and explaining Hess' law of heat summation

it states that the enthalpy change of a physical or chemical process depends only on the beginning conditions (reactants) and end conditions (products). the enthalpy change is independent of the pathway of the process and the number of intermediate steps in the process

what is the law of conservation of energy?

it states that the total energy of the universe is constant; so energy can neither be created nor destroyed

describe the lock and key model of enzyme activity in biological systems

it suggests that an enzyme is like a lock and its substrate is the key; the shape of the active site on the enzyme exactly fits the shape of the substrate

describe the induced fit model of enzyme activity in biological systems

it suggests that the active site of an enzyme changes its shape to fit its substrate

whats a simple reaction?

its a single elementary reaction or step

discussing the significance of collision geometry and collision energy in successful reactions

its important to note that not every collision between reactants results in a reaction. in order for a collision between reactants to result in a reaction, the collision must be effective. an effective collision - one that results in the formation of products - must satisfy the following 2 criteria. for a collision to be effective, it must satisfy both of these criteria: correct orientation of reactants and sufficient collision energy. reactants particles must collide with the proper orientation relative to one another, its also known as collision geometry. the reactants must collide with energy that's sufficient to begin to break the bonds in the reactants and to begin to form the bonds in the products.

use the collision theory and the concepts of collision geometry and collision energy to explain the effect of temperature on reaction rate.

its important to note that not every collision between reactants results in a reaction. in order for a collision between reactants to result in a reaction, the collision must be effective. an effective collision - one that results in the formation of products - must satisfy the following 2 criteria. for a collision to be effective, it must satisfy both of these criteria: correct orientation of reactants and sufficient collision energy. reactants particles must collide with the proper orientation relative to one another, its also known as collision geometry. the reactants must collide with energy that's sufficient to begin to break the bonds in the reactants and to begin to form the bonds in the products. when reactions occur at higher temperatures, the percent of particles that have sufficient kinetic energy to react (activation energy) increases. since a greater percent of reactant particles have enough energy to react, the rate of reaction increases.

what's the rate law and molecularity of the following elementary reaction: A = products

k[A], unimolecular

what's the rate law and molecularity of the following elementary reaction: A + B = products

k[A][B], bimolecular

what's the rate law and molecularity of the following elementary reaction: 2A = products

k[A]^2, bimolecular

what's the rate law and molecularity of the following elementary reaction: 2A + B = products

k[A]^2[B], termolecular

the closer electrons are to the nucleus, what is the effect of the potential energy?

less potential energy

compare the energy changes resulting from physical change, chemical reactions and nuclear reactions (fission and fusion)

like physical changes and chemical reactions, nuclear reactions are accompanied by energy changes. however, produce significantly more energy than physical and chemical processes.

describing examples of technologies that depend on exothermic or endothermic changes (e.g. hot and cold packs)

manufacturers take advantage of endothermic dissolution to produce coldpacks athletes can use to treat injuries. one type of cold pack contains water and a salt, such as ammonium nitrate, in separate compartments breaks and the salt dissolves, which is endothermic. it absorbs heat for a short period of time, so the cold pack feels cold. some types of cold packs have 2 compartments. one compartment contains a salt, such as calcium chloride. the other compartment contains water. in hot packs, however the dissolution process is exothermic. it releases heat to the surroundings. also, not all hot packs use dissolution processes. for example, one kind of hot pack exploits the crystallization of sodium thiosulfate or sodium acetate. another kind uses the oxidation iron (rusting).

comparing conventional and alternative sources of energy with respect to efficiency and environmental impact (e.g. burning fossil fuels)

methane hydrates form when methane molecule becomes trapped within an ice lattice as water freezes. they can form in very cold conditions or under high-pressure conditions. using methane in place of other fossil fuels is very desirable. methane hydrates seem to be an ideal and plentiful "pre-packaged" source of natural gas. estimates of the exact amount of methane stored in hydrates suggest there could be enough to serve our energy needs anywhere from 350 years to 3500 years. this would constitute a significant source of fossil fuels, if we could find a way to extract the gas safely and economically.

explain kinetic molecular theory (5 characteristics)

molecules are moving at random (always); molecules in motion must possess kinetic energy; the phases - solid (slow particle motion), liquid (faster), gas (fastest); molecules separate from each other possess electric potential energy; collisions between moving particles transfer energy between them

name the 6 techniques tat may be used to monitor concentration during a chemical reaction

monitoring mass, pH and conductivity; pressure; colour; volume

comparing conventional and alternative sources of energy with respect to efficiency and environmental impact (e.g. nuclear fission, nuclear fusion)

one energy source that engineers are trying to harness is nuclear fusion. nuclear fusion provides a great deal of energy from readily available fuel. in addition, nuclear fusion produces a more benign waste product than nuclear fission (helium). unfortunately, fusion is not yet practical and controllable on a large scale because of the enormous temperatures involved.

this is a type of a chemical system where it has interaction with its surroundings; matter can go in and out of the system; its energy can be transferred back and forth

open system

this is energy possessed by an object or body because of its position

potential energy

these are series of proposed elementary reactions that make up overall reactions

reaction mechanisms

this is the change in the amount of reactants or products over time, these are always positive by convention.

reaction rate

chemical reactions are either...

simple or complex

this is a measure of the average kinetic energy of the particles that make up a substance or system

temperature

the first law of thermodynamics

the first law of thermodynamics is that the energy of the universe is constant; energy cannot be converted from one form to another.

this is a type of kinetic energy; which is the sum of electric potential energy (position of eletrons)

thermal energy

name the various types of kinetic energy (4 types)

thermal, radiant, chemical, and nuclear bonding

what happens when work (W) is positive and when its negative?

when W is positive the system doesn't work. when W is negative - work is done and its in the system

what happens when heat (Q) is positive and when its negative?

when its positive - heat is transferred to system; when heat is negative - it left the system