CHEMISTRY COMMUNITY

Sejal Parsi 3K

As explained above, an intermediate is a molecule that is produced in a reaction, but is also consumed right after in the next step. So, there is no net increase or decrease of an intermediate.

Sejal Parsi 3K

An isolated system means that there is no matter or energy exchange, so w and q would be zero.

Sejal Parsi 3K

I believe that the side with the greater concentration is favored.

Sejal Parsi 3K

A zero order reaction graph of A concentration versus time would be a negative, linear line.

Sejal Parsi 3K

As everyone said above, it would be 1/K.

Sejal Parsi 3K

I think we would analyze a graph and identify the type of reaction from there, probably looking for a linear line and so on.

Sejal Parsi 3K

I don't think that can happen at the same time. However, it is possible for a reactant or element to get reduced and oxidized in the same reaction, just not at the same time.

Sejal Parsi 3K

As mentioned above, no the order doesn't matter and you use Pt(s) when you need to add an inert conductor in the electrode.

Sejal Parsi 3K

Yes, as they said above, it's important to keep in mind that the anode loses electrons, which go to the cathode. So as long as you know where the electrons are traveling to, you can identify the anode and cathode.

Sejal Parsi 3K

A spontaneous reaction will have a negative delta G so the final state has a lower free energy than the initial state. This means that the total energy released by the reaction is actually greater than the energy required to overcome the reaction energy barrier, so forming products is favorable, mak...

Sejal Parsi 3K

The naught just means it’s under standard conditions.

Sejal Parsi 3K

The potential outcome can be controlled by the rate of formation of the product which would be the kinetic factor.

Sejal Parsi 3K

Gibbs energy is a state function that determines whether or not a reaction is spontaneous in a reaction.

Sejal Parsi 3K

The salt bridge involves a transfer of electrons which causes each side to lose or gain charge.

Sejal Parsi 3K

Temperature is the only way to change K.

Sejal Parsi 3K

For sapling, you should include states of matter unless it says that they are optional.

Sejal Parsi 3K

I think n represents the number of moles of electrons, so it is the amount of electrons transferred in the equation.

Sejal Parsi 3K

They’ll usually tell you or you can tell by the species present.

Sejal Parsi 3K

As said above, it comes from ln(2).

Sejal Parsi 3K

I think the higher the density, the higher the capacity is.

Sejal Parsi 3K

They both are different and not interchangeable as said above.

Sejal Parsi 3K

E°cell is the standard cell potential at standard conditions (1 M solution, 1 atm, 298 K). Ecell is the cell potential at conditions that are not standard conditions.

Sejal Parsi 3K

Q is equal to K at equilibrium, and Q is when the reaction is not at equilibrium.

Sejal Parsi 3K

Like they all said above, order is the sum of the exponents of the reactants in the rate law. A first order reaction is dependent on one reactant, a second order reaction is dependent on two reactants, and so on.

Sejal Parsi 3K

The given rates are for the forward reaction. The initial rates are used so that the reverse reaction does not happen and so that there are only concentrations of the reactants.

Sejal Parsi 3K

As said above, U and E are extensive properties.

Sejal Parsi 3K

K essentially tells us the ratio of the products and reactants, so the units cancel out.

Sejal Parsi 3K

As said above, I believe Dr. Lavelle said that those terms are interchangeable.

Sejal Parsi 3K

I believe vapor and gas are in the same phase so they are interchangeable in this class.

Sejal Parsi 3K

A change in pressure (a change in volume) only affects gases. Solids and liquids are not affected because they are essentially incompressible.

Sejal Parsi 3K

If the reaction is endothermic, raising the temperature will make K increase. If the reaction is exothermic, raising the temperature will make K decrease.

Sejal Parsi 3K

I believe this is one of the 7 strong acids we need to remember!

Sejal Parsi 3K

You would do 10^(-pka)!

Sejal Parsi 3K

I believe you would use Kelvin as the constant R uses that unit as well.

Sejal Parsi 3K

I think that if the equilibrium constant is under 1x10^-3, you can assume that the change is insignificant, but I've seen that 1x10^-4 is more accurate. It can be assumed to be insignificant if it doesn't change the value you get after calculations.

Sejal Parsi 3K

ICE boxes are used to find unknown concentrations at equilibrium or initial ones when given the concentration of reactants or products. Finding equilibrium composition means the same as finding equilibrium concentrations.

Sejal Parsi 3K

I believe almost all equations work, but you would have to be aware of how an open system affects the variables.

Sejal Parsi 3K

Because it is a gas, you would include it.

Sejal Parsi 3K

I memorized the list of strong acids and bases and if an acid or base is not listed on that, I classify it as weak!

Sejal Parsi 3K

Water has a higher enthalpy of vaporization because of its hydrogen bonds, so when these bonds re-form, they release heat, creating the burns.

Sejal Parsi 3K

Reactions that release heat are exothermic. Reactions that take in energy while forming products are endothermic.

Sejal Parsi 3K

The conjugate base of a weak acid will be a strong base.

Sejal Parsi 3K

We would need to know if the reaction is endothermic or exothermic. Then, we could determine which it favors based on the change in temperature.

Sejal Parsi 3K

The total pressure is all the pressures combined at equilibrium, found by adding up the partial pressures of all the compounds in a reaction.

Sejal Parsi 3K

Inert gas is not reactive, so it will not react with any of the reactants or products and not change their concentrations.

Sejal Parsi 3K

Ka is the equilibrium constant for acids and Kb is the equilibrium constant for bases. You can solve for them by doing [P]/[R].

Sejal Parsi 3K

Yes, Q is the reaction quotient and can be found at any time, but K can only be found at equilibrium.

Sejal Parsi 3K

K becomes the inverse: 1/K.

Sejal Parsi 3K

K only changes with a temperature change.

Sejal Parsi 3K

I normally use molar concentration because it keeps everything consistent and saves a step at the end.

Sejal Parsi 3K

I believe they would show up as being acidic.

Sejal Parsi 3K

You would do 10^(-pH) to get the H+ concentration.

Sejal Parsi 3K

It’s because fluorine is so electronegative that in a solution, it won’t give up its hydrogen easily, and strong acids tend to dissociate easier in solutions.

Sejal Parsi 3K

I think it is normally based on significant figures, but I typically keep between 4-5.

Sejal Parsi 3K

Pi bonds only apply to covalent bonds!

Sejal Parsi 3K

Nickel can hold up to 10 total valence electrons because of its 3d and 4s subshells.

Sejal Parsi 3K

Water is amphoteric so it can act as both!

Sejal Parsi 3K

Organic molecules have carbon-hydrogen bonds while inorganic molecules don’t have carbon-hydrogen bonds.

Sejal Parsi 3K

pH= -log[H+] and you don’t need to know how to derive it.

Sejal Parsi 3K

Hard water contains more mineral ions like Ca2+ and Mg2+, soft water is less alkaline.

Sejal Parsi 3K

As everyone has said, pH and pOH are the H+ and OH- concentrations. Kb is the base dissociation constant, so the larger the Kb the stronger the bases and pKb is also just another way to write Kb.

Sejal Parsi 3K

I think that is almost everything you need to know. You should probably also know that pi bonds form when orbitals overlap side-to-side and sigma bonds form when orbitals overlap end-to-end.

Sejal Parsi 3K

Hi! As stated above, generally all sigma bonds are in hybridized orbitals.

Sejal Parsi 3K

Hi! As they said above, I think the order of the ligands doesn't matter so long as the cation is the first one.

Sejal Parsi 3K

Sigma bonds are single bonds and pi bonds are in double and triple bonds. In a double bond, one bond will be a sigma bond and the other a pi bond, and for triple bonds, there is one sigma bond and two pi bonds.

Sejal Parsi 3K

To determine hybridization, you count the number of atoms that are bonded to the atom and add this number to the number of lone pairs there are around the atom. sp goes with 2, sp2 goes with 3, etc.

Sejal Parsi 3K

Because Hydrogen only likes to form one bond, it can’t be the central atom. They are normally added to the end of Lewis structures because of this.

Sejal Parsi 3K

Yes, as stated above, I think we always consider the most stable structure while determining the shapes of molecules.

Sejal Parsi 3K

The higher the boiling point or melting point is, it takes more energy to break the bonds, which would be the intermolecular forces.

Sejal Parsi 3K

Yes, it can be called bent or angular!

Sejal Parsi 3K

A pi bond is created when two p orbitals overlap side by side, with electron density concentrated above and below the plane of the bonding atoms.

Sejal Parsi 3K

Yes, lone pair electrons do count and will affect the shape because of their strong repulsion.

Sejal Parsi 3K

Yes, I agree with the post above. I remember Lavelle saying that the smaller the electronegativity between the atoms, the more covalent they are.

Sejal Parsi 3K

Thought there are dipole moments happening between atoms in a molecule, they can cancel out, making the molecule non polar.

Sejal Parsi 3K

I agree with the dots and lines method as well. It seems easier to understand and do as well, counting each dot and line as 1.

Sejal Parsi 3K

Hi! Like they said above, the C-Cl bond is polar while the C-H bond is non-polar, so the dipoles won’t cancel out.

Sejal Parsi 3K

Ionic bonds are formed when a metal transfers its electron to a nonmetal to form an electrostatic attraction between them, while covalent bonds are from the sharing of electrons between nonmetals.

Sejal Parsi 3K

Hi! An element with a negatively charged ion will have a larger radius because it has additional electrons than one that's positively charged. It's good to check the periodic table and follow trends if it is not for the same element though.

Sejal Parsi 3K

Double bonds are shorter because they have two more electrons than single bonds, so their attraction to the nucleus is stronger, pulling them closer and making the bond shorter.

Sejal Parsi 3K

This because it only needs one electron to complete its shell, so it is highly reactive.

Sejal Parsi 3K

Electronegativity describes how well an atom attracts electrons while electron affinity shows the amount of energy released when an electron is added to make it negative. Electronegativity is also a calculated value.

Sejal Parsi 3K

Gamma rays have the shortest wavelength, but the highest energy or frequency.

Sejal Parsi 3K

Yes, I believe it does not matter what side you put it.

Sejal Parsi 3K

Hi! The number of electrons would be the same as the atomic number and if you are referring to the valence electrons, it would be the amount of electrons in the incomplete shell of the element.

Sejal Parsi 3K

Regardless of the fact that it is an electron, it will be 1-.

Sejal Parsi 3K

Hi! The sign corresponds to the charge of the molecule since the structure itself may not show it. If the ion is positive, there will be a positive sign outside the bracket; if the ion is negative, there will be a negative sign outside the bracket.

Sejal Parsi 3K

As stated above, typically you use the same units across the problem, but if the answer is in another unit, you can simply convert your answer! Also, out of practicality in labs, they may use mL instead of L if that seems more reasonable to use for the measurement.

Sejal Parsi 3K

Hi! I don’t think we will need to memorize those, and mostly everything needed will be on the reference sheet, periodic table, or given in the problem!

Sejal Parsi 3K

Hi! I believe Dr. Lavelle mentioned in a lecture that we would not have to memorize polyatomic ions and that if there is something we have not covered, he would provide us with any needed information!

Sejal Parsi 3K

Hi, until the 4s level is completely filled, the electrons won’t go into the 3d level. But once electrons go into 3d, that will be the level with lower energy, so 3d is written first.

Sejal Parsi 3K

I think we use E=hv to find the energy of a photon using Plank's constant and the frequency of light, so most of the times when we are dealing with frequency. While E=pc also finds the energy of a photon, it uses the speed of light and momentum of the photon, so it's important for De Broglie's equat...

Sejal Parsi 3K

As said, frequency plays a role in characteristics of waves because if the frequency is higher, then the wave will be shorter. And if the frequency is lower, the wave will be higher because frequency and wavelength are inversely proportional as shown by the equation.

Sejal Parsi 3K

I think it’s best to use the amount of sig figs given in the problem, and to not round your answer until the very end to keep it accurate. I believe my TA said we could be partially penalized if our sig figs are way off.

Sejal Parsi 3K

I believe the simple explanation is that excited electrons are electrons with energy that move up energy levels within an atom, while ejected electrons are electrons that have been removed from the atom itself.

Sejal Parsi 3K

Hey! I think this is because the closer you are to the nucleus, the harder it is to go up energy levels because of the positive pull from the nucleus. But as you get further away from the nucleus, the pull is less so the energy levels are smaller and take less energy to get to.

Sejal Parsi 3K

Hey! That’s correct, increasing the intensity of the light meant increasing the brightness which is more photons. Had they increased the frequency/changed the wavelength, the experiment would have worked.

Sejal Parsi 3K

Hi, as said by everyone above, it is best to use as many sig figs as given on the periodic table, and then to round your final answer appropriately to the sig figs given within the problem.

Sejal Parsi 3K

I don’t think we have to memorize just yet how to name compounds according to what Dr. Lavelle said during a lecture. I assume we may have to know basic ones in the future though.

Sejal Parsi 3K

I think it is preferred that moles always be in the nearest whole number. If you get moles as a fraction, you could multiply it with the closest number in order to get a whole number and do so to the rest of the equation if applicable.

Sejal Parsi 3K

I think sig figs are typically important to keep in mind as it gives accuracy to the problem based on the numbers given. If you are rounding, you should probably round to a reasonable number or round in order to get the right amount of sig figs. I also saw someone ask about when to use scientific no...

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