CHEMISTRY COMMUNITY

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At active sites, 1+ reactants are adsorbed on to the surface of the catalyst. Adsorption is where something sticks to a surface. Absorption is where one substance is taken up within the structure of another.

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Increasing the concentration of the reactant in a zero-order reaction will not speed up the rate of the reaction.
Zero-order reactions are typically found when a catalyst, is saturated by the reactants.

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The half-life of a first-order reaction is inversely proportional to the rate constant k. A fast reaction has a larger k and shorter half-life. A slow reaction has a smaller k and longer half-life.

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Activated Complex- collection of intermediate molecules that are created as a chemical reaction progresses
Transition state- intermediate of a chemical reaction that makes up the highest potential energy

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In a 1st order reaction, there is one reactant in the rate law. In a 2nd order reaction, there's either a rate law with one reactant to the second order, or two reactants to the first order.

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Free energy of activation has to do with Gibbs free energy. Activation energy is the energy that is needed to get over the energy barrier of each transition step.

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Pseudo-first order kinetics is when a reaction is 2nd order overall but is first order with respect to two reactants:
rate=k[A][B]
A and B are some reactants, and the initial rate depends on both A and B. As the reaction proceeds both A and B are changing in concentration and affecting the rate.

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For these second-order reactions, the integrated rate law is:

1/[A]=kt+1/[A]0
This equation relates the concentrations of reactants and the rate constant of second-order reactions.

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The integrated rate law links concentrations of reactants or products with time directly.

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Use the integrated rate law when you want to know the instantaneous rate (the slope of the curve) as a function of concentration.

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I believe the integrated rate Law tells us the instantaneous rate (the slope of the curve) as a function of concentration.

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A chemical reaction has kinetic and thermodynamic aspects. The kinetics rate constant is associated with the activation energy required for the reaction to proceed (reactivity of the reactants). The thermodynamic quantity is the energy difference that results from free energy given off during a chem...

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The initial rate is the instantaneous rate of reaction as it starts, so just as product just begins to form. The average reaction rate is the average of the instantaneous rates over a time period.

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A reaction is of third order if the rate is determined by the variation of three concentration terms. The minimum number of molecules necessary for a third order reaction to take place is three.

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The rate law is a differential equation. This means that it describes change in concentration of reactants per change in time. The rate law can be integrated to get an integrated rate equation that connects concentrations of reactants/products directly with time.

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I believe that only the rate constant changes with temperature. The form of the rate law is always the same and acts independently of temp change. Usually at higher temp, the rate constant increases.

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I believe that the rate of a chemical reaction at a constant temp depends only on the concentrations of the substances that influence the rate. The substances that influence the rate of reaction are usually one or more of the reactants, but can occasionally include products.

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Short reaction times usually suggest kinetic control, and longer reaction times usually suggest thermodynamic reaction control. If a reaction is under thermodynamic control at a certain temp, it will also be under thermodynamic control at a higher temp for the same reaction time. If a reaction is un...

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Some metals have stronger “replacing” power than other metals. Although H2 is not a metal, it can still be “replaced” by some strongly reducing metals. The tendency of a metal to “displace” H2 from acidic solution determines its solubility. If the metal cannot displace H, it wont be oxidized and wil...

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The Nernst equation can be used to find the cell potential at any moment during a reaction or at conditions other than standard-state.

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The Gibbs free energy is equal to the max amount of non-expansion work that comes from a closed system. When a system goes from its initial state to its final state, Gibbs free energy = (work exchanged by the system with its surroundings) - (work of the pressure force).

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A salt bridge connects the oxidation and reduction 1/2 cells of a galvanic cells. It works to maintain electrical neutrality w/in the internal circuit, and prevents the cell from rapidly reaching equilibrium. If no salt bridge were present, the solution in one 1/2 cell would accumulate negative char...

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The cell potential, is the measure of the potential difference between two electrochem 1/2 cells. Potential difference is caused by the ability of electrons to flow from one 1/2 cell to the other. Electrons have the ability to move between electrodes because the reaction occurring is a redox reaction.

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Temperature is held constant, therefore the change in energy is zero (U=0). So, the heat absorbed by the gas equals the work done by the ideal gas on its surroundings.

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A system either does work on it surroundings or has work done on it by its surroundings. This is modeled by: deltaEsys = q + w Reactions do work on their surroundings when the volume of the system increases. The amount of work of expansion done by the reaction = the product of the pressure against w...

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Specific heat shows the amount of energy as heat needed to be provide to a system for the temperature of the system to have a unit rise. The value of it varies depending on the process providing this energy. Cv for a gas is the change in internal energy (U) of a system with respect to change in temp...

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Intensive/extensive properties are physical properties of matter. Intensive properties don't depend on the quantity of matter, and are considered bulk properties (Ex: density, state of matter, and temperature). On the other hand, extensive properties depend on sample size, and are considered additiv...

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The combustion reaction inside the bomb occurs at constant volume and there is no work. This means that the change in internal energy for the calorimeter is zero. Since the change in internal energy is 0, the calorimeter is isolated from the rest of the universe. deltaU(calorimeter) = q(calorimeter)...

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There is a larger change at lower temperatures since the change in entropy is QT. This makes the decrease in entropy of the hot object less than the increase in entropy of the cold object. This results in the production of an overall increase.

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If the temp of the gas decreases, the gas molecules slow down, and the internal energy of the gas decreases. This means that ΔU is negative.

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More work can be obtained by increasing the number of stages of a process(allowing the gas to expand against multiple successively lower external pressures). To get the maximum possible work from the process, the expansion should be carried out in an infinite sequence of infinitessimal steps.

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In an isothermal process the temperature does not change, and in an adiabatic process there is no heat added or removed. (It's possible for temperature change to occur without the involvement of heat.)

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Exothermic reactions- release energy, usually in the form of heat because the total energy of the products is less than the total energy of the reactants. This means that the change in enthalpy for an exothermic reaction will always be negative. Endothermic reactions- require external energy in the ...

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Reversible expansion: The state starts off where gas pressure = external pressure. Then, an external force decreases the outside pressure, making the gas slightly before reaching a new equilibrium state. This procedure is repeated as many times as needed to reach the desired pressure. Irreversible e...

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In irreversible reactions, the reactants react to form products which can't form back into reactants. In reversible reactions, reactants react with other reactants to form products and products react with other products to form reactants at the same time.

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Reversible expansion occurs when the expansion has no spontaneous direction of change because there is no net force pushing the gas to seek a larger or smaller volume. This takes place when the pressure of the expanding gas = the external pressure resisting the expansion. It is said to be reversible...

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Internal energy is an extensive property, so internal energy depends on the size of the system (amount of substance it contains).

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For constant pressure and constant volume, the heat exchanged is proportional to the difference in temperature and the amount of gas. The proportionality constant is Cp for the process at constant pressure and Cv for the process at constant volume. The major difference between the two is that work i...

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Internal energy is the potential energy of the system + the kinetic energy of the system. A reactions change in internal energy = heat gained/lost (enthalpy change) in the reaction when it is at a constant pressure.

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Enthalpy is considered a state function because it only depends on two thermodynamic properties which describe the state of a substance at the moment (ex:temperature and pressure, temperature and entropy). It doesn't depend on the path the substance followed to get there.

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When a substance's phase changes, its temperature remains constant until the phase change completes. For example, when ice is heated, its temperature increases until it reaches 0 C. At 0 C, it starts melting and the solid water is turned to liquid water.

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There's more energy in the steam, so to raise the temperature of one gram of water to 100'C requires less energy than it takes to convert that same gram of water to steam. The energy in the steam is greater than the energy in the same weight of water at the boiling point, and this heat is released w...

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“Heat capacity” refers to the amount of heat required to heat a certain object by 1ºC. “Specific heat capacity” refers to the amount of heat required to heat 1 g of a ceratin substance by 1ºC. “Molar heat capacity” refers to the amount of heat required to heat 1 mol of a certain substance by 1ºC.

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Solubility equilibrium is based on solids dissolving in water to produce the basic particles that form them. Molecular solids dissolve into individual aqueous molecules, and Ionic solids dissociate into their respective cations and anions. The solubility equilibrium constant (Ksp) is the product of ...

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Adding an inert gas to a system in equilibrium at constant volume doesn't effect the equilibrium. However, when adding an inert gas to a system in equilibrium at constant pressure the the total volume will increase.

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The more stable a system is, the lower the potential energy of it is. Chemical processes usually occur because they are thermodynamically favorable, meaning they go from high energy(less stable) to low energy(more stable).

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I would say not to use the assumption for 10^-4, just to be safe.

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Protonation occurs when a proton is added to an atom, molecule, or ion. Protonation and deprotonation occur in most acid-base reaction. A species' mass and charge change, and its chemical properties are altered when it is either protonated or deprotonated. For example, water can be protonated by sul...

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All chemical reactions are reversible. Both the forward and reverse reaction occurs depending on conditions. In a chemical equilibrium, these forward and reverse reactions just occur at equal rates. The concentrations of products and reactants remain constant.

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It might be helpful to pay close attention to the chemical equation and see if the molecules being used are identified as (l),(g),(aq).

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Plug in the concentration NH3 and the given value of Kc into the equation Kc = [NH3][H2S] and just simply use algebra to solve for the value of H2S, which would be its concentration.

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If K = 1, the reaction will reach equilibrium as an intermediate mixture. This means the amount of products and reactants will be about the same. The value of K is dependent on the chemical reaction, so if the chemical equation is manipulated in any way, the value of K will change.

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Gases such as nitrogen, oxygen, hydrogen, noble gases, and some heavier gases like CO2 can be treated like ideal gases w/in reasonable tolerances.

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Monoprotic acids contain just one hydrogen ion whereas polyprotic acids contain two or three hydrogen ions. This makes many assume that polyprotic acids are stronger than monoprotic acids because they contain more hydrogen ions, but that's not necessarily true. Polyprotic acids only let go of one hy...

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It's definitely possible to find a negative pH value. Many acids with a concentration of hydrogen ions greater than a molarity of 1 will be calculated to have a negative pH.

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Amphoteric compounds can act as acids by donating their proton to the base to become its conjugate acid. They can also act as a base by accepting a proton from an acid to become its conjugate base. The degree to which a molecule acts depends on the medium in which the molecule has been placed in.

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A Lewis acid is a compound or ionic species which accepts an electron pair from another, donor compound. A Lewis base s any substance that can donate a pair of nonbonding electrons, making it an electron-pair donor.

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Carboxylic acids have a lot of electron cloud density and a strong bond due to the O-H group. Because of this it becomes difficult for the carboxylic acid to furnish the H+ ions and dissociate.

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A coordination compound is a class of compounds in which a central metal atom is surrounded by a group of ions or molecules called ligands.

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I believe its a complex where a metal ion is bound to 2+ atoms of the chelant

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A Lewis acid is any substance that can accept a pair of nonbonding electrons, making it an electron-pair acceptor. (ex: H+ ion)

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Latin names are used for some metals in the complex anions:
Iron-->Ferrate
Copper-->Cuprate
Lead-->Plumbate
Silver -->Argenate
Gold -->Aurate
Tin-->Stannate

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A polydentate ligand is a type of ligand that is attached to a central ion(metal ion) by bonds from 2+ donor atoms.

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My TA said that the test is most likely going to be from section 2D through to hybridization in the outlines.

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IF4 is square planar because I(the central atom) is bonded to only 4 outside atoms. Its lone pairs do not count when it comes to its shape. An octahedral shape would suggest that the central atom is bound to 6 outside atoms.

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The shape of a molecule shows how atoms are arranged around the central atom. The lone pairs of electrons affect this arrangement, however they are not part of it. If there are no lone pairs of electrons, the arrangement of groups of electrons and the arrangement of atoms around the central atom wil...

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Lone pairs tend to be in unhybridized p orbitals when they are adjacent to pi-bonds. For example, when a nitrogen expected to be sp3 is adjacent to a pi bond, its hybridization is actually sp2.

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You add up all the lone pairs and bonds around the central atom and make sure the total adds up the total of the "exponents" of each s and p in your hybridization.

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Usually a question will indicate if a full configuration is needed, but other than that a noble gas configuration is very commonly used and should do.

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Pi bonds are weaker than sigma bonds, because according to Quantum mechanics, its orbital paths are parallel so there is a significant amount of less overlap between the p-orbitals.

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The shape the electrons take around the central atom is what is considered electron geometry. Molecular Geometry however, is the shape the actual connections between atoms have in a compound, which is dictated by the compounds electron geometry.

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I believe we will have to memorize bond angles for the most common structures. However, many times you can tell some of the angles of the structure (like when its 90 or 180 degrees) by looking at the VSEPR structure itself which can make the process easier.

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Bond angles change from their ideal values because lone pairs repel other electrons stronger than bonding pairs do. Although lone pairs are smaller than atoms, they are closer to the nucleus of an atom than a bonding pair is. Their closer proximity to the central atom causes lone-pairs take up more ...

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Neutral nonpolar atoms have electron clouds with spherically symmetrical electron arrangements. These electron clouds can be distorted if in the presence of an electric field, and I believe this distortion is defined as the polarizability of the atom or molecule. This distortion allows originally no...

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The type and strength of covalent bonds between atoms is indicated by their bond order and bond length. The two properties are inversely proportional to each other, so, when bond order is increased, bond length is decreased.

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Dipole moments occur when there is a separation of charge, and they arise from differences in electronegativity. The larger the difference in electronegativity, the larger the dipole moment.

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Electronegativity is a measures how strongly atoms attract bonding electrons to themselves, whereas electron affinity is the amount of energy released or spent when an electron is added to a neutral atom or molecule.

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A coordinate covalent bond is formed when one atom provides both electrons in a shared pair.

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Radicals are very reactive. They form new bonds with other molecules that have unpaired electrons very quickly.

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When filling an orbital you must fill all orbitals possible with one electron spin(spin up) before assigning the opposite spin(spin down). If the last electron that is filled into the orbital is spin up then the ms quantum # is + 1/2, but if the last electron is spin down then the ms quantum # is -1...

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I believe the least electronegative element generally becomes the central atom.

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A single bond is a sigma bond, whereas a double bond is a sigma bond and a pi bond. A sigma bond is a basic covalent bond, with the bond in line with the bonding orbitals. Only one sigma bond can exist between any two atoms. A pi bond is a covalent bond between orbitals that are perpendicular to bon...

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Electronegativity measures how strongly atoms attract electrons to themselves whereas electron affinity is the amount of energy released by a neutral atom or molecule when an electron is added to it.

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Nonmetals have 5, 6, or 7 electrons in their valence shells, so it takes less energy for them to form anions by just gaining the necessary electrons.

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If you plug in all the variables the equation: delta x= (1/2)(h/(m*delta v)) should provide the answer straight away.

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First use the E=hc/wavelength formula to find the energy. Then, multiply that my the mols of Na and avagadros number to get the energy for 5g of Na. After that, multiple avagadros number to the number you calculated in part a to find the energy for 1mol of Na.

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The principal quantum number "n", describes the electron shell. It increases as the electron energy increases. For example, n = 3 indicates the 3rd shell, and n = 4 indicates the 4th shell. The value of "l" depends on "n". It cannot be larger than one less than "n&...

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Simply just use the E=hc/(wavelength) formula to get the energy per photon and multiply that by (32*2), because 32W is given as the amount emitted in 1 second but its asking for the amount emitted in 2 seconds. Then, once you have the number of photons, divide by avagadros number to convert to moles...

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Its very usefully to have the photons of electromagnetic radiation memorized in order of increasing energy and frequency. These concepts come up in various other topics as well so it will be very applicable.

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When particles are in their ground state, atomic radius generally increases top to bottom and decreases from left to right. I believe that atomic radius is always measured when all of an elements electrons are in their ground state.

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I believe that quantum mechanics(and quantum theory) is a fundamental theory in describing the smallest scales of atoms/subatomic particles.

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I believe that a photon does not have a specific size. It carries energy, momentum,and frequency, but is simultaneously a particle and a wave.

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I believe that the more energy levels an electron drops, the greater the change in the kinetic energy is. I does not have to drop one energy level at a time.

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Light exhibits particle properties when it interacts with matter. This can be seen in the photoelectric effect. Electrons, however, show wave properties of interference and diffraction when they near obstacles.

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A combustion reaction generally indicates that the products of the reaction will be CO2 and H20.

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I was also confused as to why the dilution formula could not be applied to this example!

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The dot actually doesn't stand for multiplication. It just indicates that the compound is a specific type of compound called a hydrate. The dot shows that the two compounds are bound together.

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As a general rule with sigfigs: non-zero numbers are always significant, zeros between two significant numbers are significant, and trailing zeros are significant only in the decimal portion.

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Dimensional analysis is essentially just a method to convert one type of unit to another type. To convert from one unit to another a conversion factor is used, which is a numerical quantity that we can multiply or divide to the number we want to convert.

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