CHEMISTRY COMMUNITY

Michelle Xie 2B

it changes with temperature.

Michelle Xie 2B

Probably just to derive/integrate the formulas.

Michelle Xie 2B

You can look at units of rate constant for the orders of each reactant and add them together.

Michelle Xie 2B

You can see the difference when you derive the half life formula from each rate law.

Michelle Xie 2B

Half lives are used more for real world applications.

Michelle Xie 2B

molecularity is the number of species that participate.

Michelle Xie 2B

thermo is used to determine how a reaction progressed while thermo is used to look at initial and final states.

Michelle Xie 2B

first determine orders of individual reactants and then add them together for the overall order.

Michelle Xie 2B

activation energy is not the same as change in enthalpy.

Michelle Xie 2B

it is trapped if it has high activation energy, even though it may be thermodynamically favorable.

Michelle Xie 2B

A concentration cell has different concentrations.

Michelle Xie 2B

It is for concentration cells and when the concentrations are not at the standard ones.

Michelle Xie 2B

If there's no solid, Pt is used.

Michelle Xie 2B

There are certain elements where we know their oxidation but for a molecule, the oxidation numbers of the atoms should add up to the total charge.

Michelle Xie 2B

Activation energy is the energy needed to a reaction to occur.

Michelle Xie 2B

You use the known oxidation numbers for some elements and fill in the rest. The sum of all the oxidation numbers should add up to the total charge of the molecule.

Michelle Xie 2B

I don't think it matters where the molecules are placed as long as they are balanced correctly and on the correct side.

Michelle Xie 2B

A decrease in number means a decrease in charge, which signifies reduction because it gains an electron and goes down in charge. vice versa for increase

Michelle Xie 2B

There's some rules to follow, such as oxygen is almost always 2-, fluorine is almost always 1-, etc. The oxidation numbers of all the elements should add up to the charge.

Michelle Xie 2B

H2 is an exception because it is a diatomic and in its most stable form.

Michelle Xie 2B

delta H is in kj/mol. if it was just kj, it would be q or just energy.

Michelle Xie 2B

it depends on the system.

Michelle Xie 2B

I think we just need to know the monoatomic ones.

Michelle Xie 2B

adiabatic means where there is no transfer of heat, so q is zero.

Michelle Xie 2B

only delta U, or change in internal energy is 0.

Michelle Xie 2B

If the system is doing work, or expanding, work would be negative. If it had work being done on it, or being compressed, it would be positive.

Michelle Xie 2B

both would be negative since the system is losing energy.

Michelle Xie 2B

Energy is released when bonds form, therefore making it exothermic and the enthalpy would be negative since the final molecule has less energy than the separate atoms.

Michelle Xie 2B

I think method one is the most accurate since the enthalpies are given as exact for each reaction.

Michelle Xie 2B

You add enthalpies together, reverse signs for reverse reactions, and multiply if you multiply the whole reaction.

Michelle Xie 2B

The bond enthalpies are averages of all the possible ones, so it is less accurate.

Michelle Xie 2B

You add the enthalpies and reverse signs when the reaction is reversed.

Michelle Xie 2B

If delta H is positive, it means the reaction is endothermic .

Michelle Xie 2B

If delta H is positive, it means the reaction is endothermic .

Michelle Xie 2B

pKa + pKb is pKw, which is 14.

Michelle Xie 2B

In an exothermic reaction, the heat is written as a product. Increasing a product would push the reaction to the left and favor the reactants.

Michelle Xie 2B

You use the principle when the reaction is no longer at equilibrium.

Michelle Xie 2B

Adding inert gases will not change concentration of anything and will just be present among both sides of the molecules. The inert gas does not react with anything.

Michelle Xie 2B

A left shift favors reactants and a right shift favors products.

Michelle Xie 2B

Usually, it will be given.

Michelle Xie 2B

When Q is less than K, more products tend to form.

Michelle Xie 2B

The greater the ksp, the greater the solubility.

Michelle Xie 2B

Take the least amount of sig figs.

Michelle Xie 2B

Px is used for gases to represent their partial pressure. In other cases, you would use concentration.

Michelle Xie 2B

Changing the equilibrium means you take the reaction out of the equilibrium by removing or adding reactant/product. Changing the constant would mean you have to change pressure and temperature.

Michelle Xie 2B

A large K would mean the product concentration in the equation is much greater than the reactant. Therefore, the reaction at equilibrium favors the products.

Michelle Xie 2B

Solids and liquids are not included in the equation.

Michelle Xie 2B

K can be represented with both Kp and Kc.

Michelle Xie 2B

Yes, sigma bonds are single bonds. Pi bonds are any bonds on top of the first one.

Michelle Xie 2B

Intermolecular is between molecules while intramolecular is within a molecule.

Michelle Xie 2B

Yes the higher the hydronium ion concentration, the lower the pH and the more acidic.

Michelle Xie 2B

I think we can assume it is zero since the pH scale is between 0 and 14.

Michelle Xie 2B

The proton combines with the hydroxide ion to make water and the two other ions made a salt.

Michelle Xie 2B

One proton gets transferred at a time.

Michelle Xie 2B

Water acts as the base. It can do this because it is an amphoteric molecule. I also think you meant the hydronium ion instead of the hydroxide ion.

Michelle Xie 2B

The lewis definition involves the transfer of a pair of electrons. The bronsted definition involves transfer of a proton.

Michelle Xie 2B

Both are ok.

Michelle Xie 2B

Amphoteric compounds can both donate and accept a proton.

Michelle Xie 2B

A bronsted acid is one that can give up a proton. A lewis acid is one that can accept a pair of electrons.

Michelle Xie 2B

Bronsted acids involving the donating and accepting of a proton while lewis acids involve donating and accepting of a pair of electrons.

Michelle Xie 2B

There is usually one d metal atom.

Michelle Xie 2B

Cisplatin can bind to DNA molecules and prevent cells from dividing. It is used as a treatment for cancer.

Michelle Xie 2B

Coordinate covalent bonds form when the ligand donates both electrons in the electron pair.

Michelle Xie 2B

In a coordinate covalent bond, the nonmetal has a lone pair and donates both electrons to the bond.

Michelle Xie 2B

It's the number of bonds on the central atom.

Michelle Xie 2B

Ligands are not the central atom. They bond to the central atom.

Michelle Xie 2B

Electrons naturally repel each other so having a greater distance between them would lower these repulsion forces.

Michelle Xie 2B

H2O is bent because of the two lone pairs on the oxygen.

Michelle Xie 2B

Trigonal planar is in one plane and has three areas of e density while trigonal pyramidal is 3d and has 4 areas.

Michelle Xie 2B

I think we will need to know most of the names.

Michelle Xie 2B

The solid triangle represents the atom coming out of the page towards you. The dashed lines represent the atom going away from you into the page. Lines are used to draw atoms that are on the same plane as the paper. The other two symbols are when the atoms come out of the plane.

Michelle Xie 2B

Atoms with n=3 and greater can accommodate more than 8 electrons in its valence shell.

Michelle Xie 2B

A lewis base would donate a pair of electrons and a lewis acid would accept a pair of electrons.

Michelle Xie 2B

They are able to use their 3d orbital. They are just normally not filled.

Michelle Xie 2B

The most stable would be the one in which the most atoms have the lowest formal charges.

Michelle Xie 2B

It depends on the atom radii. If the atoms are larger, the bond is weaker because the pull of the nucleus weaker due to how far apart they are from the electrons.

Michelle Xie 2B

The numbers are the bond length between the carbon atoms.

Michelle Xie 2B

The element needs to have a d orbital, so only those from n=3 and greater.

Michelle Xie 2B

As you go down a period, there is more and more shielding, making the nuclear charge weaker. Therefore, it is harder to pull an electron in, decreasing the electronegativity.

Michelle Xie 2B

Use the element with the lowest electronegativity.

Michelle Xie 2B

Double bonds are used to satisfy the octet rule, which lowers the energy of the molecule, making it more stable.

Michelle Xie 2B

NH4 does not have resonance but some molecules that do are the nitrate and carbonate ions.

Michelle Xie 2B

It is with a metal and nonmetal since a metal tends to give electrons away to the nonmetal.

Michelle Xie 2B

Covalent bonds are just between two nonmetals.

Michelle Xie 2B

The ground state is when the atom is at the lowest possible energy. It corresponds to the electron configuration.

Michelle Xie 2B

There are electron repulsions with paired electrons, therefore it is not favorable to have paired electrons before parallel ones.

Michelle Xie 2B

If an electron isn't following one of the rules, it is in an excited state. Atoms fill their orbitals with electrons starting from the lowest energy levels and with parallel spin. If an electron skips one of these levels, it is in an excited state.

Michelle Xie 2B

Some ions have only one electron, such as He 1+ or Li 2+.

Michelle Xie 2B

ml can only range from -l to +l. So for example, if l=2, ml can be -2, -1, 0, 1, or 2. Therefore if l=0, ml can only be 0.

Michelle Xie 2B

The photon will be emitted again once the electron falls back down from the excited level. The photon has to have the exact amount of energy needed in order for the electron to absorb it and move to a higher energy level.

Michelle Xie 2B

As the electrons get farther from the nucleus, the pull of the nucleus becomes weaker. Therefore, it takes less energy to remove that electron from that level.

Michelle Xie 2B

It represents the energy of a photon, but can be used to find energy needed.

Michelle Xie 2B

The higher intensity in terms of wave properties would just mean a larger amplitude.

Michelle Xie 2B

I usually just use 3.00 unless theres like another value with a crazy amount of sig figs. It should be fine since Prof. Lavelle also used it.

Michelle Xie 2B

Points probably won't be taken off for the correct number of sigfigs. I save all my decimals till the very end and then round where I need to so I'm not off by a few decimals.

Michelle Xie 2B

You would probably lose points. Also even though the equation is balanced without whole numbers, it doesn't make sense for there to be half of a molecule. It would not only make more sense but also make solving problems later on easier with whole number coefficients.

Michelle Xie 2B

The amount of solute doesn't change, only the solvent. So when you are calculating dilutions, you only need to account for the added solvent since you already know the amount of solute already.

Michelle Xie 2B

Dilution is when you add more solvent, decreasing the concentration of the overall solution since the amount of solute remains the same.

Michelle Xie 2B

I used 6.022 x 10^23 in all the problems and I've gotten the right answer so I would say use that, especially if Dr. Lavelle uses it too.

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