CHEMISTRY COMMUNITY

Casandra

adding a catalyst has no effect on the equilibrium, it just speeds up reaction.

Casandra

You determine the reaction is not at equilibrium and that Q<K, therefore there is too much reactant, meaning to reach equilibrium the reaction will need to produce more product, thus going in the forward reaction.

Casandra

They should give us the Ecell values needed like in test 2.

Casandra

They should tell you if it's acidic or basic.

Casandra

n is the moles of electrons, and to find n you should do the half reactions and determine how many electrons were exchanged in the half reactions.

Casandra

E^o is the standard reduction potential, which means under standard conditions: 1atm, 1M, and at 25 degrees Celsius
E is the cell potential, which changes.

Casandra

For a zero order rate the units are mol/L*s
For a 1st order rate the units are 1/s
For a 2nd order rate the units are L/mol*s

Casandra

The graph for a 2nd order reaction is a linear graph with a positive slope.

Casandra

For the Van Hoff equation you use units of K for temp, and if given in C, convert by adding 273.

Casandra

The 1/2 life for a first order does not depend on the initial concentration.

Casandra

Sometimes the question tells you which order it is, and from there you can determine the rate. Otherwise, there should be sufficient data given to dtermine which rate to use.

Casandra

K doesn't have any units, due to it being a ratio (in which the units cancel)

Casandra

delta U is equal to zero when the reaction is isothermal, meaning temperature is constant.

Casandra

Gibbs Free Energy is a state function, all the properties of the equation deltaG = deltaH - T(deltaS) are also state functions.

Casandra

Ka2 is the second deprotonation of phosphoric acid

Casandra

Most, if not all the equations and conversions we will need are on the constants and formulas page. Of course we do need to know how to rearrange the equations for certain problems.
https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf

Casandra

knowing the Lewis structure is helpful but the bond dissociation energies will be given which will also help you figure out how the bonds are formed or broken.

Casandra

The test should provide the chemical equations, but knowing the format of a combustion and how acids go from HA--> A- + H+

Casandra

Condensation releases energy.

Casandra

In a closed system matter can't exchange with the surroundings but energy can in forms of heat or work, a closed system can also have a fixed volume.
In an isolated system nothing exchanges with the surroundings .

Casandra

In an open system matter and energy can exchange with the surroundings, an example is a beaker of water. In a closed system energy can exchange with the system, an example is a sealed beaker of water. In a isolated system nothing exchanges with the surroundings, an example is a combustion of glucose...

Casandra

The question will ask you to solve for pH or pOH, and the problem will also give you sufficient information to be able to solve for this.

Casandra

Does anyone know of any tips or tricks that will allow you immediately to identify an acid or base as weak or strong? For strong bases and strong acids, it would help to memorize the list of strong acids and bases, because then you know anything that is not a strong base or acid, has to be weak. Al...

Casandra

How does ∆Hsub=∆Hfus+∆Hvap work? Thanks! Because Enthalpy is a state function, its properties can be added or subtracted. We know that ∆Hvap= Hvapor-Hliguid and that ∆Hfus=Hliquid-Hsolid. For sublimation we are going from a solid to a liquid and a liquid to a vapor, which is two steps, therefore we...

Casandra

How does a change in pressure affect the equilibrium in a reaction?

Casandra

Buffers can consist of a weak acid and its conjugate base, as well as the salt. Or vice-versa, a weak base and its conjugate base with the salt.

Casandra

Q alone tells you nothing, but once compared to K, it tells you where the reaction is in terms of reaching the equilibrium concentration.

Casandra

HF, hydrofluoric acid is a weak acid.

Casandra

Calculating the values of K and Q requires the same process of solving. The only difference is that K tells you the equilibrium of the reaction, whereas Q tells you where you are on the path to equilibrium. This is why Q is useful when comparing it to K.

Casandra

I know solids and liquids aren't included when calculating the equilibrium constant. Are aqueous solution included when calculating the equilibrium constant?

Casandra

Just to be clear we only need to conceptually understand Ka and Kp values and equilibrium constants but we do not actually have to solve for this or use these factors for anything except determining which acid or base is stronger? Yes that's right, we only need to conceptually understand Ka and Kp....

Casandra

Anna O 1A wrote:Is the coordination number determined by the number of atoms attached to a central atom, the number of bonds (including double and triple) or the number of regions of electron density?

The coordination number is determined by the number of bonds.

Casandra

Isabel Nakoud 4D wrote:Why is Structure 2 a stronger acid than Structure 4?

Because the electron withdrawing ability of H is greater than CH3 and as there is more electron withdrawing ability, the acidity increases.

Casandra

jane_ni_3b wrote:For something with the formula AXE3, would the bond angles be 180 because the molecular shape is linear?

Yes the bond angles would be 180 because its shape is linear.

Casandra

I understand the electron/proton acceptor/donor concept, but how can you tell if a molecule is a Lewis acid/base or Bronsted acid/base? Examples would be much appreciated A molecule can be more than one type of acid or base, it just depends on which definition you apply. For most of the problems we...

Casandra

There's no easy way to know whether a coordination compound is polydentate, for this it is helpful to draw the lewis structure. But it is also good to know that bidentate ligands are ethylenediamine (en), and the oxalate ion (ox). Ethylenediaminetetraaceticacid acid (EDTA) is a hexadentate ligand an...

Casandra

For oxoacids, the more electronegative the central atom, the more acidic the molecule will become. For a binary acid, strong acids like HCl are always strong, but the weaker the bond between the nonmetallic and hydrogen bond, the esier it is for H2O to remove the H+

Casandra

To tell if an element is a lewis acid or base just remember that a lewis acid is a species that accepts an electron pair like BF3 and a lewis base is a species that donates an electron pair like NH3.

Casandra

The time given to us is 3 hours, and its just up to one to distribute the time between each question evenly or however one would like.

Casandra

905085650 wrote:Can someone explain to me the effect that salts have on acids and bases respectively?

Thank you!!

A salt containing an acid will lower the solutions pH whereas a salt containing a base will raise the solutions pH.

Casandra

A chelate is a coordination compound containing a ligand bonded to a central at two or more points, usucally froming a ring. so if a coordination compound contains at least one non-monodentate ligand it's considered a chelate. An exapmle is ironn in hemoglobin.

Casandra

905085650 wrote:Can someone explain the difference between amphoteric and amphiprotic and give me an example of each?

Thank you!!

Amphoteric is a compound that can act as a base and an acid, like H2O
Amphiprotic is a substance that can donate and accept protons or H+, like amino acids

Casandra

404905747 wrote:Is there any easy way to identify a strong acid or strong base besides just memorizing them?

No, just memorize them, and if you have memorized them, then anything that is not a strong acid, is a weak acid.

Casandra

Some basics are that there is a Lewis and a Bronsted definition to acids and bases. A lewis acid a species that accepts an electron pair(ex. BF3) and a lewis base is a species that donates and electron pair (ex. NH3). Whereas, a bronsted acid is a proton donor and donates a hydrogen ion (ex. HCl) an...

Casandra

What are polydentates and monodentates? Is there a certain list we should memorize? monodentate is a ligand that binds at 1 site and a polydentate is when a ligand binds to more than 1 site. I don't know of there is a list to memorize, but it would be helpful to know that some bidentate ligands are...

Casandra

Why would strong acids be conjugates of weak bases and vis versa? This concept escapes me. A conjugate base is the molecule that is formed after an acid loses a proton. An acid or base and its conjugate are inversely proportional in terms of strength. Therefore the stronger the acid the weaker its ...

Casandra

Strong Acids: HCl, HBr, HI, HNO3, HClO3, HClO4, and H2SO4
Stong Bses: LiOh, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Ba(OH02, and Sr(OH)2

Casandra

Bijan Mehdizadeh 1E wrote:Could someone please explain to me what en and edta are?

en and edta are ligands.
en is a neutral ligand named ethylenediamine
edta is an anionic ligand named ethylenediaminetetraacetato

Casandra

Will we be asked to name a compound in final? If so, do we have to memorize some of the ligand names? Yes you do have to memorize the ligand names. Lavelle has a link that leads to the name of the ligands on the class website. https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/Naming...

Casandra

Soyoung Park 1H wrote:How are hydrogen atoms and hydronium ions the same?

H+ and H3O+ are the same in that the hydronium ion is just the H+ attached to a water molecule.

Casandra

[quote="Daniela Alvarado 3B"]Does the bond length change depending on where the double bond is in the resonance structures?[/quot The bond lengths are the average all the bonds in the resonance structures , so where the double bond is in the resonance structure is already taken into consid...

Casandra

Are all molecules with four bonding pairs tetrahedral? What makes the difference if they are not? All molecules with four bonding pairs and no lone pairs are tetrahedral. But if there was a lone pair, then it would be a trigonal pyramid, and so on. If a molecule has more or less than four bonding p...

Casandra

Why is the dissociation energy of a covalent bond, like N2, 932 kJ/mol and an ionic bond's, like NaCl, is -250 kJ/mol? (I wrote these down on my notes from the lecture). Since ionic bonds are stronger, wouldn't it have a much higher dissociation energy than N2? Why is it's dissociation energy negat...

Casandra

What are some other examples of Lewis acids and bases other than the examples from lecture? A lewis base is a molecule that will donate a pair of electrons to another atom. Some examples are NH3 and F-. A lewis acid is a molecule that will accept a pair of electrons. Some examples are AlCl3 and BH3.

Casandra

claireg wrote:What are some examples of elements in compounds that exemplify exceptions to the octet rule and the reasons behind them?

Exceptions to the octet rule are atoms like, phosphorus, Sulfur, and Chlorine, this is because these elements have the d-orbital.

Casandra

how does increasing the intensity of the incoming photon affect the energy of the photon. Does it increase its energy, and if so, does that increase the number of electrons that will be emitted? Increasing the intensity increases the number of photons, because intensity and the number of photons ar...

Casandra

How are the exceptions to electron configuration determined? It explains in the textbook why they set up the configuration in certain elements this way but what differentiates copper and another metal? The exceptions to electron configuration are the groups of 6( chromium) and 11(copper). These two...

Casandra

How can you distinguish if an element has a full octet? Does each orbital have to have a full octet before moving to the next orbital? Only noble gasses in their natural state have an octet. However, there are two ways to figure out how many electrons an element needs to complete an octet. One, you...

Casandra

The radius increases you go down a group(column) and the radius decreases as you go from left to right of a period.

Casandra

Why are these important? What are they? The Balmer and Lyman series are important because they help determine the energy level of electrons, and this is important when using Rydberg's equation. The Balmer series is used when in the visible spectrum, with n1=2. The Lyman series is used in the UV spe...

Casandra

In Monday's notes we wrote that the description if light as photons explains the intensity profile of black body radiation but have yet to talk about it again. Are we supposed to know the concept/definition of black body radiation? Is there any importance or significance to black body radiation? Gr...

Casandra

I cannot conceptualize light being both photon (PACKETS) of energy and wavelengths. I find it difficult to exercise this into equations when I do not understand how it can be both and have one number. Please explain and possibly use equations in your explanation if possible. If not that is okay, an...

Casandra

When I solve problems I don’t round until the very end and keep all my sigfigs but sometimes the answer I get is 0.01-0.02 digits different from the one in the solution manual. Will this be a big problem on the homework/test? I would ask your TA, because they will be grading our homework and test, ...

Casandra

In the equation E= -hR/n^2 h, represent Plank's constant which is 6.626x10^-34J/s R, is Rydberg's constant which is 3.29x10^15 Hz n, is the number of the energy level of an electron (this is the quantized value) Overall, this contributes to finding the amount of energy contained in one electron whil...

Casandra

I would expect that he would want us to write our final answers in SI units unless otherwise stated, like if the final answer is looking for an answer in g as opposed to kg. I do know that our TA's are grading our exams, therefore it might vary per TA too.

Search found 65 matches