CHEMISTRY COMMUNITY

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for first order, M/s
for second order, 1/s
for third order, 1/Ms
in general: $M^{1-n}$ $time^{-1}$

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The Arrhenius equation can be used to find pre-exponential factor, the rate constant, activation energy, or temperature based on what information given in the question.

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A gas enclosed by a piston in a cylinder can do work on the piston, the work being the pressure multiplied by the change in volume. If the volume doesn't change, no work is done. If there is no change in volume ( $\Delta$ V=0), work will equal 0.

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An activation energy is a potential energy barrier that reactants have to get over in order to react. The higher this potential, the slower the reaction (the exact relationship is shown by the Arrhenius equation). It follows naturally that the step with the highest activation energy will be the slow...

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Catalysts increase the reaction rate without being consumed. A catalyst provides an alternative route for the reaction. That alternative route has a lower activation energy.

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An elementary reaction is a chemical reaction in which one or more chemical species react directly to form products in a single reaction step and with a single transition state. There are no intermediates and only one transition state. It can be unimolecular, bimolecular, or termolecular. With regar...

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Half-Life is the time it takes for one-half of the atoms of a radioactive material to disintegrate. The "half" is an arbitrary amount that represents the amount disintegrated; it can be a "quarter-life" or a "fifth-life". It is useful in dating artifacts, treating patie...

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Catalysts are not reactants; they just lower the activation energy. They are substances added to a chemical reaction to speed up the reaction rate without being consumed. Catalysts are not in the overall chemical reaction. For example, enzymes are catalyst in biochemical reactions.

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For zero-order reactions, the concentration of one of the reactants is independent to the reaction rate. For first-order reactions, the concentration of one of the reactants and reaction rate is directly proportional. So if the concentration of one of the reactants is doubled, the reaction rate is d...

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Moreover, free energy of activation includes both the standard enthalpy of activation and the standard entropy of activation; thus, it is more accurate than the activation energy, which only accounts for the standard enthalpy of activation. Although both free energy of activation and activation ener...

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Electrochemical series is a series of chemical elements arranged in order of their standard electrode potentials.

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A kinetic product is one that forms the fastest as the product is associated with the lowest energy barrier to its formation. At low temperatures, the reaction is under kinetic control (rate, irreversible conditions) and the major product is that from fastest reaction. A thermodynamic product is one...

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If the slope of the tangent line is positive, the forward reaction is favored. Because products are favored, the amount of products should be increasing. Thus, they have a positive rate of change. If the slope of the tangent line is negative, the reverse reaction is favored. More reactants will be p...

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An electrolytic cell is an electrochemical cell in which electrolysis takes place. Just like a galvanic cell, electrolytic cells have reduction occurring at the cathode and oxidation occurring at the anode. Unlike in a galvanic cell, however, in which the current is generated spontaneously, in an el...

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For Example 14.4, we know Hg2Cl2 is the element that gets reduced because the right side of the cell diagram corresponds to reduction.
H2 is getting oxidized because the left side of the cell diagram corresponds to oxidation.

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Potential difference is also known as voltage. It is the electron moving force in electricity and is responsible for the electric current through a circuit. This current is the pushing and pulling of electrons.

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For 9.27a, where the book is asking which substance has the higher molar entropy at 298K between HBr (g) and HF (g), HBr (g) has the higher molar entropy because it has a greater molar mass.

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\Delta G measures how much potential a reaction has left to do a net amount of something. If \Delta G is negative, the forward reaction is favored. If \Delta G is positive, the reaction is reactant favored. If the free energy is zero, the reaction is at equilibrium because there is no more net work...

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An easy way to remember this is LEO says GER. It stands for "lose electrons oxidation; gain electrons reduction"

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dS is the instantaneous rate of change at a specific point.
$\Delta s$ is the change in entropy.
So far, we just had to find $\Delta s$ .

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Use the equation nRln(V2/V1)= $\Delta s$
n= 4.80 moles
V2= 4.80 moles
V1= 12.86
Expect a decrease in entropy because the volume decreased.

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Standard pressure is 1 atm. 1 atm is equivalent to 1.01325 bar. Although they are close, 1 bar is not standard pressure.

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ΔHc is the enthalpy of combustion.
ΔHL is the lattice enthalpy (ions).
ΔHb is bond enthalpy.

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Thermal disorder is the disorder arising from the thermal motion of the molecules. Thermal disorder will increase if a system is heated up because the supply of energy increases the motion of the molecules. Positional disorder is the disorder arising from the location of the molecules. Entropy incre...

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The first law of thermodynamics is basically the conservation of energy. Energy can't be created or destroyed; however, it can change from more useful forms to less useful forms. Every energy transfer has some amount of less useful energy generated (usually in the form of heat). Heat that doesn't do...

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Use Cv when there's constant volume. This is the specific heat when there's constant volume.
Use Cp when there's constant pressure. This is the specific heat when there's constant pressure.

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At constant pressure, when the system expands, it loses energy. Thus, the internal energy of the system decreases. The negative sign means energy is losing the system when it expands.

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Heat and work are similar in that they both describe energy transfer.
I think of work as referring to something more mechanical, like pushing a piston.
I think of heat as referring to the thermal process thats responsible for temperature differences.

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The heat gained by the water in the ice cube will be equal to the heat lost by the initial sample of hot water. The change in enthalpy for the water surrounding the ice cube will have two parts: 1. the heat to melt the ice at 0 degrees 2. the heat required to raise the ice from 0 degrees to the fina...

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The standard state of an element is stated on the periodic table.
Liquid is the standard state for bromine and mercury. Gas is the standard state for the noble gases, hydrogen, helium, nitrogen, oxygen, fluorine, and chlorine. Solid is the standard state for all other elements.

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Enthalpy includes internal energy. Enthalpy is the sum of the internal energy and the product of the pressure and volume of the system.
Internal energy is the sum of the potential energy and the kinetic energy of the system.
The unit for both is joules.

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Yes, the for the change of internal energy is:
$\Delta U$ =q (heat) + w (work)

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Ka is the acid dissociation constant. pKa is the negative base-10 log of Ka. They both represent the strength of the acid in a solution; they are just expressed in different ways. The smaller the pKa, the stronger the acid. The larger the Ka, the stronger the acid. Likewise, Kb is the base dissociat...

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A localized bond pair travels between two atoms. A bond pair that moves between two different pairs of atoms is considered delocalized. You can identify delocalized bonds by checking the electron locations in two different resonance forms; if the pair changes location and form, it is delocalized.

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A pi bond happens when two sets of electron orbitals involved in the bond overlap. A common example occurs in benzene. They are seen in resonance structures with different locations of double and triple bonds.

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The diagrams depict the disassociation of the diatomic molecule, X2, over time. If by which state of the equation you mean equilibrium, the number of non-disassociated X2 molecules is the same for flask 3 and flask 4. Because the number did not change, equilibrium was reached in flask 3.

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You can determine that equilibrium was reached in flask 3 because there is no further disassociation from flask 3 to flask 4.

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S-character is the percentage of sigma bonds in the hybridization. For example, sp hybridization has 50% s-character, 50% p-character; sp2 has 33% s-character, 66% p-character; ect. The s-character coincides with the bond angle. sp is linear and has 180 degree bond angle. sp2 is 120 degrees. sp3 has...

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In problem 4.1, the ball-and-shape model b is 180 degrees. The answer says "may contain lone pairs". If lone pairs affect the shape of the molecule, how can a molecule with lone pairs be 180 degrees (linear)?

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All elements can hold an octet except for hydrogen. All of the d-block and above can have an expanded octet. For the Lewis dot diagram, all the orbitals do not need to be filled because atoms can have a formal charge.

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There are cases of quadruple bonds in the transition metals. Transition metals have d-orbital which is required to form a quadruple bond.

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Electron Affinities of:
Group IIA- around zero because filled s subshell discourages addition of an electron
Noble Gases- completely filled shell discourages addition of an electron; electron affinity values are positive, meaning it requires input of energy to add an electron

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Glycine is an amino acid so it has an amino group on one end (the NH2) and a carboxyl group (the COOH) on the other. For COOH, one O shares a double bond with C and the other O shares a bond with C and H. For NH2, the two Hs are bonded to N. The N should be bonded to the C in CH2. The C of COOH shou...

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Ga^3+: [Ar]3d10
1. Take Gallium's electron configuration [Ar]3d10 4s2 4p1
2. Remove 3 electrons (remove 4s2 4p1)

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Why do electrons with parallel spins tend to avoid each other and occupy different orbitals? Why would the direction of spin influence this repulsion? According to Hund's Rule, electrons always occupy an empty orbital before pairing up. Because electrons are negatively charge, paired electrons repel...

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Is there an explanation for the chromium and copper electron configuration exception? Do we have to memorize the electron configurations or is there a way to figure it out?

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How do you determine how many unpaired electrons an atom has? 1. Write the electron configuration 2. Find any incomplete orbitals, if any (s-orbitals with less than 2 electrons; p-orbitals with less than 6 electrons; d-orbitals with less than 10 electrons) 3. For the incomplete orbital, fill in the...

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According to De Broglie's equation, anything with mass and velocity has wavelike properties, including a baseball or a car. However, these larger items have too small of a wavelength to be considered "measurable".

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In this case, change in the electrical field means light emitted since its an electromagnetic wave. According to the equation E=hv, frequency is directly proportional to energy. So, when frequency decreases, the energy decreases (answer: C).

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The solutions manual wasn't very clear about this question... Question: The field of nanotechnology offers some intriguing possibilities, such as the creation of fibers one atom wide. Suppose you were able to string together 1.00 mol Ag atoms, each of radius 144 pm, into one of these fibers by enca...

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A solution is prepared by dissolving 55.1g of KCl in approximately 75mL of water and then adding water to a final volume of 125mL. What is the molarity of KCl(aq) in this solution? I know that Molarity equals: Molarity=moles of solute/ volume of the solution but in this case would we not use this f...

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