CHEMISTRY COMMUNITY

Myka G 1l

The rate constant k is similar to the equilibrium constant K in that it is only affected by a change in temperature.

Myka G 1l

The activation energy (Ea) for the forward reaction is the potential energy difference between the activated complex and the reactants. For the reverse reaction it is the potential energy difference between the activated complex and the products. If the forward reaction has a lower activation energy...

Myka G 1l

You could also use the equation [A]t= [A]o e^-kt

Myka G 1l

Yes, the rate determining step is the slowest step. You can think of it like the limiting reactant.

Myka G 1l

You use whatever two reactions will allow you to cancel the value of the other reactant, allowing you to find the order of the desired reactant.

Myka G 1l

T can be in either seconds, minutes, or hours depending on what the problem asks for. As before mentioned the same units must be used throughout the problem.

Myka G 1l

When using an ICE Table, can you ever have a starting value of products, or is it always 0? Sometimes you will have a starting value of products and you’ll have to add x to the value in the ice table, creating a more complex equation that is equal to k. Also don’t forget coefficients in the ice tab...

Myka G 1l

In a first order reaction, the rate of reaction is directly proportional to the concentration of a single reacting substance. Whereas in a 2nd order reaction the rate depends on the concentration of 2 reacting first order substances or a single reactant with a squared concentration. Because it depen...

Myka G 1l

In a first order reaction, the rate of reaction is directly proportional to the concentration of a single reacting substance. Whereas in a 2nd order reaction the rate depends on the concentration of 2 reacting first order substances or a single reactant with a squared concentration. Because it depen...

Myka G 1l

.0150 mol NH3 was formed, which means that half that amount of N2(.075) decreased. This occurs because the stoichiometric coefficient of NH3 is 2 and the coefficient for N2 is 1. The same goes for the H2 but it decreases by 1/3 of the amount of NH3 formed.

Myka G 1l

You would add an inert solid if there are no solids in the reaction that could be used as a conductor. Usually Pt is added as the electrode.

Myka G 1l

Short reaction times usually mean the reaction is kinetically controlled while longer reaction times usually suggest thermodynamic reaction control.

Myka G 1l

According to the question, the partial pressure of the reactants was equal to half the products so each reactant would be equivalent to x and the product would be 2x. When you multiply the reactants and do products over reactants you get 2x/x^2.

Myka G 1l

Short reaction times usually mean the reaction is kinetically controlled while longer reaction times usually suggest thermodynamic reaction control. A reaction that is thermodynamically favored but doesn't occur spontaneously because of a high activation energy is kinetically trapped.

Myka G 1l

K is the normal rate constant for a reaction, let's say for rate = k[A]N[B]M[C]L. However, if [B]0 and [C]0 >> [A]0, we can say that rate = k'[A]N, and that the reaction is a pseudo-first order reaction. Comparing the two, we can see differences in the units of k, with k' having units of L2*mol-2*s-...

Myka G 1l

Differential rate laws describe the change in reactant or product concentrations as a function of time. Integrated rate laws describe the actual concentrations of reactants or products as a function of time. The only 2k I can think of is for the half life equation of a zero order reaction which is [...

Myka G 1l

Even though BF3 and COF2 are both trigonal planar, COF2 has both oxygen and fluorine atoms occupying the same locations, as opposed to BF3 having only fluorine occupy these locations. It would be more likely for disorganization to occur within the COF2 molecule because of the different atoms rather ...

Myka G 1l

The collision model explains why most collisions between molecules do not result in a chemical reaction. Also, in a first order reaction there is one colliding species that influences the rate while in a second order reaction there are two species colliding and so on.

Myka G 1l

I would at least know the strong acids and bases, usually on the test they’ll give a formula for the more complex ones.

Myka G 1l

I think that you would have to determine the anode and cathode by looking up the reduction potentials for the half reactions. The more positive value is more likely to be the cathode because it is a better oxidizing agent and the less positive value will be the anode because it is a better reducing ...

Myka G 1l

There’s a solid line separating Ag(s) and AgBr(s) despite the fact that they are both in the same state because Ag(s) is the electrode whereas AgBr(s) is just a solid involved in the reaction.

Myka G 1l

The order in cell diagrams is based on phase so it should be s|g|aq||aq|g|s.

Myka G 1l

Both tests are worth 50 points.

Myka G 1l

Yes, even though iodine is a solid it cannot be used as a conductor, so Pt is needed as the electrode.

Myka G 1l

Platinum is only used as an electrode, it does not participate in the reaction; therefore, should not be included in the half reactions for the cell.

Myka G 1l

In a first order reaction, the rate of reaction is directly proportional to the concentration of a single reacting substance. Whereas in a 2nd order reaction the rate depends on the concentration of 2 reacting first order substances or a single reactant with a squared concentration. Because it depen...

Myka G 1l

A cell diagram is arranged with the electrode on the outside, then solid, gas, aqueous until the salt bridge. If you have a liquid my TA said you can add it either between the solid and gas or gas and aqueous because the book doesn’t explicitly tell you what to do when you have a liquid.

Myka G 1l

You first have to add H20 to balance the O’s. Then, in an acidic solution you just add H+ to balance the H’s . Whereas in a basic solution you either add H+ and balance it with OH- to create H20 or you add an H20 for every 2 OH- molecules on the other side in order to balance the hydrogens.

Myka G 1l

The salt bridge allows for ion transfer between the anode solution and the cathode solution. It maintains both solutions at a neutral state, allowing the the electron flow from anode to cathode to continue for an extended period of time.

Myka G 1l

The charges come from the periodic table. Elements in group 1 are typically denoted as having a +1 charge, which is why hydrogen has a +1 charge. While oxygen has a -2 charge because it is a part of group 16.

Myka G 1l

I think you separate Ag(s) and Br(s) with a line because Ag(s) is the electrode, whereas Br(s) is just a solid in the reaction.

Myka G 1l

A third order reaction is a chemical reaction in which the rate is proportional to the concentration of three reacting molecules. This type of reaction is very uncommon because all three reactants would have to simultaneously collide together, with sufficient energy and correct orientation, to produ...

Myka G 1l

Percent dissociation is the amount of H+ ions produced by an acid in solution divided by the amount of unreacted acid [HA].

Myka G 1l

Heat capacity is an intensive property because it depends on the amount of matter that you start with. Heat capacity is defined as the energy that it takes to raise 1mol of substance by 1 degree c, and it takes more energy to raise 1 mol of a complex molecule by 1 degree C than it does a simple one.

Myka G 1l

Mass is conserved in chemical reactions due to the law of conservation of mass which states that matter cannot be created or destroyed.

Myka G 1l

You would only use the Boltzmann equation if the reaction is at 0K and no other forms of entropy are occurring. This equation measures the residual/positional entropy of molecules.

Myka G 1l

Molar heat capacity is the heat required to raise the temperature of 1 mol of a substance by 1 degree Celsius.
Since NO2 is a larger molecule than NO, it would require more heat to raise the temperature of 1 mol of NO2 by 1 degree versus the heat required to raise the temp of NO by 1 degree.

Myka G 1l

Heat capacity is an extensive property because a large quantity of matter will have a proportionally large heat capacity. Specific heat capacity is an intensive property because it doesn't matter how much substance you start with, the specific heat capacity is always the amount of energy required to...

Myka G 1l

Yes, its the same equation just different notations.

Myka G 1l

The equilibrium constant for the overall reaction is equal to the product of the equilibrium constants for the individual reactions.

Myka G 1l

Hess's Law states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes. Therefore, you can use it to add enthalpy changes at each step of a multi step reaction to yield the total enthalpy change. To use Hess's law you hav...

Myka G 1l

A calorimeter is a device used to measure the amount of heat involved in a chemical reaction. It can determine heat content, latent heat, specific heat, and other thermal properties of substances.

Myka G 1l

Breaking bonds itself is an endothermic process because it requires energy to break any bond. However, whether a reaction is endothermic or exothermic depends on the difference between the energy needed to break bonds and the energy released when new bonds form. When ATP is converted into ADP it the...

Myka G 1l

Yes, if the x value divided by the initial value comes out to be more than 5% then you have to go back and do the quadratic formula to solve.

Myka G 1l

pKb is the -log(Kb) and pKa is the -log(Ka). pH is related to pKa through the Henderson Hasselbach equation -> pH= log[A-]/[HA] + pKa

Myka G 1l

Water as a liquid has such a high specific heat capacity compared to its solid and gaseous forms due to the hydrogen bonding between water molecules. When heat is absorbed by water, hydrogen bonds are broken(which requires energy) and the molecules move freely. When the temperature of water decrease...

Myka G 1l

Delta S is entropy- the measure of disorder in a system. Enthalpy is denoted as delta H.

Myka G 1l

The enthalpy of vaporization is greater than the enthalpy of fusion because during a phase change the molecules are separated and the energy required to completely separate the molecules from a liquid to gas is much greater that if you were just to reduce their separation when converting from solid ...

Myka G 1l

I believe aqueous solutions are included in equilibrium constant concentrations.

Myka G 1l

If products or reactants are strongly favored then it means there is a large disparity between products and reactants. If the products or reactants are simply less than or greater than 1 then they could be very close in concentration(there could also still be a large disparity).

Myka G 1l

Hybridization depends on the number of regions of electron density so double and triple bonds would count as a single region.

Myka G 1l

In the marshmallow review session they said a way to find the oxidation state was to give the bonding electrons back to the ligand to find the formal charge, then use the formal charge of the ligands to find the oxidation state of the metal. So the nitrogens with the single bonds and lone pair will ...

Myka G 1l

For the ligand to be polydentate it needs to have more than one atom that is is highly electronegative and they need to be far enough apart that the molecule can bind in two places. For example cyanide CN- is only monodentate despite the negative charge on the carbon and lone pair on the nitrogen be...

Myka G 1l

A bidentate is a polydentate because it binds to the central metal atom at two sites. Polydentates also include ligands that bind to the central metal atom at more than two sites.

Myka G 1l

First you find the pOH by taking the -log of the OH concentration.
pOH= -log(1.2 x 10^-10)=9.92

Then you subtract the pOH from 14 to get the pH
pH= 14-9.92=4.08

Myka G 1l

K and Na aren't accounted for in the equilibrium solution because they form KOH and NaOH which are strong bases and wouldn't affect affect pH.

Myka G 1l

For the ligand to be polydentate it needs to have more than one atom that is is highly electronegative and they need to be far enough apart that the molecule can bind in two places. For example cyanide CN- is only monodentate despite the negative charge on the carbon and lone pair on the nitrogen be...

Myka G 1l

Oxalate is bidentate because only two of the oxygens have a minus 1 charge that they use to form a bond with the central metal atom. The other two oxygens form a double bond with the carbon so they have a neutral formal charge.

Myka G 1l

All molecules have London dispersion forces because all molecules have electrons that are constantly moving around the molecule and can temporarily congregate to one side, creating a temporary partial negative charge. The more electrons present and the larger an atom is, the stronger these forces wi...

Myka G 1l

When drawing the lewis structure of a radical you place the unpaired electron on the most electronegative atom.

Myka G 1l

The formula for tetraamminediaquacobalt(iii) bromide is [Co(NH3)4(OH2)2] Br3 because the given charge of Cobalt is 3+ and the ammines and aquas are neutral so in order to balance the coordination compound the anion must have a charge of 3-. Bromine has a charge of 1- so there must be three of them t...

Myka G 1l

Bis is used instead of bi when there are two chelating ligands. For example if there are two ethylenediamine ligands (bidentate and chelating) then you would say bis(ethylenediamine). If there are three chelating ligands it will be tris and if there are four it will be tetrakis.

Myka G 1l

A chelating ligand is any ligand that forms more than one bond with a central metal atom so bidentate ligands are included.

Myka G 1l

From looking at the coordination compound formula you can tell which ligands are polydentate by the number of highly electronegative atoms they contain. In this example there are three nitrogens with lone pairs that can bond to the central metal atom so the molecule would be tridentate.

Myka G 1l

Organometallic complexes only occur in transition metal complexes if the ligand is organic.

Myka G 1l

A stronger acid has a lower pka value opposed to a weaker acid because a lower pKa equals a higher Ka value. A higher Ka value means the acid dissociates more readily because it has a larger concentration of Hydronium ions.

Myka G 1l

Acids will donate a hydrogen ion and bases will accept a hydrogen ion. It is common but not necessary for bases to have Hydroxide or Oxygen as a part of their chemical formula.

Myka G 1l

An amphoteric compound is a compound that can act as both an acid and a base which means it can both accept and donate a proton. Yes, water is an amphoteric compound.

Myka G 1l

A conjugate base is what is formed after an acid donates a proton. A conjugate acid is what is formed when a base accepts a proton. An acid and a base which differ only by the presence or absence of a proton are called a conjugate acid-base pair.

Myka G 1l

All atoms have London dispersion forces because all atoms have electrons that are constantly moving around the atom and can temporarily congregate to one side. The more electrons present and the larger an atom is, the stronger these forces will be.

Myka G 1l

Molecular geometry is the 3-D arrangement of the atoms in a molecule, including the general shape of the molecule as well as bond lengths and bond angles.

Myka G 1l

A molecule is also considered non polar if it has polar bonds and is symmetrical because the charges "cancel out" because they are distributed evenly among the molecule.

Myka G 1l

A bond is polar if its difference in electronegativity is between 0.4 and 2. If the electronegativity between the two molecules is less than 0.4 then the molecule is considered non polar. You can usually tell whether or not a bond is polar by seeing how far apart the two elements are on the periodic...

Myka G 1l

Hybridization happens when atomic orbitals mix to form a new atomic orbital that can hold the same total number of electrons as the old ones.

Myka G 1l

I think the first equation where Ep is proportional to a1a2/r^6 is the real equation and the second equation where 1/r^6 was used to demonstrate the inverse effect that distance has on interaction potential energy.

Myka G 1l

The larger a molecule is, the more electrons it has to participate in induced dipoles and also has a greater surface area for these interactions to occur.

Myka G 1l

Bond angles have to do with the molecular geometry of a molecule which is influenced by the number of bonds and unshared pairs a molecule has.

Myka G 1l

Polarizability is influenced by the number of electrons and the size of the atom or molecule. The more polarizable an atom or molecule is, the stronger its intermolecular forces will be.

Myka G 1l

Induced dipoles are temporary interactions. A molecule with a permanent dipole would be considered polar.

Myka G 1l

Al doesn't achieve a full octet because it only has 3 valence electrons and would need to gain five electrons to have a full valence shell which is difficult.

Myka G 1l

Yes, atoms that have a d orbital can use it to expand their octet.

Myka G 1l

To find formal charge you use the equation FC= valence electrons-(lone pairs + number of bonds)

Myka G 1l

You just have to use the expected charges of the individual ions to figure out the chemical formula. For a the charge of Mg is 2+ and As is 3- so the chemical formula would be Mg3As2 because you want the charges to cancel out. For b the charge of In is 3+ as indicated by the Roman numerals and the c...

Myka G 1l

The atom that goes in the middle is the one with the lowest ionization energy; in this case it would be Nitrogen.

Myka G 1l

The higher the effective nuclear charge, the greater the pull of electrons to the nucleus. Therefore, the electrons will be harder to remove when the ENC is higher and the ionization energy will be higher.

Myka G 1l

The quantum numbers tell us exactly where an electron is and its spin state in an atom.

Myka G 1l

The 4s sublevel is filled before the 3d sublevel because the 4s is slightly lower in energy; therefore, easier to fill. An easy way to remember this is by looking from left to right on the periodic table.

Myka G 1l

As mentioned already, I don't believe we'll need to know this for the test but the particle in a box model is typically used as hypothetical example to show the differences between classical and quantum systems. It details a particle free to move in a small space completely surrounded by barriers.

Myka G 1l

H bar is equal to h/2pi, while h by itself just represents Planck's constant.

Myka G 1l

This question is asking which subshell the electron belongs to based on the first two quantum numbers. For example in part a where n=5 and l=2, the sub shell is 5d. the second part of the question is asking how many orbitals could share those first two quantum numbers.

Myka G 1l

In the photoelectric effect, the photons behave as particles because they experience 1:1 interactions with the electrons in the metal. Increasing the intensity of the light does not result in more energy in this experiment(as it would if light was behaving as a wave) because increasing the intensity...

Myka G 1l

Electrons in the outermost shell have the greatest amount of energy because they are the farthest from the nucleus. These electrons are experiencing less of a pull to the positive nucleus; therefore, have more energy.

Myka G 1l

Wavelength is a measure of distance, so it measured in meters (usually smaller measurements of meters like nm)

Myka G 1l

Increasing the intensity of the wave increases the amplitude, and thus increases the amount of energy the wave has if light is behaving as a wave. For example, large waves in the ocean(higher amplitude) are stronger and have more energy than small waves(lower amplitude).

Myka G 1l

I'm pretty sure we just use the lowest amount of significant figures found in the numbers that are given to you already in the problem.

Myka G 1l

Yes, zeroes in between two numbers and any final or trailing zeroes(occurring at the end of the decimal) are also significant.

Myka G 1l

The CaC2 is limiting the amount of product formed. 100g of CaC2 produces 40.6 g of the product C2H2, while 100g of H20 produces 72.3g of the product C2H2. CaC2 limits the entire reaction, causing the theoretical yield to be 40.6g of C2H2.

Myka G 1l

From the formula there are 2 moles of M to every mole of O. The relative number of moles of O = 11.2 % /16 (Molar mass oxygen) The relative number of moles of M = 88.8% / Molar mass of M But you know that 88.9/Molar mass M = 2 x 11.2/16 rearrange to give Molar mass M = 88.9/ (2 x 11.2 / 16) = 88.9 x...

Myka G 1l

No, in this case you first subtract 4.14 g of P by 27.8g of the solid compound to find the mass of Cl. 27.8g compound - 4.14g P + 23.66 g Cl then you divide both elements by their molar masses 4.14g P(1/30.97g) = 0.1337 mol P 23.66g Cl(1/35.45g)=0.6674 mol Cl finally you divide both moles by the sma...

Myka G 1l

There are 30 moles of gas for the reactants and 36 moles of gas for the products so the net moles of gas would be 36-30= 6

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