CHEMISTRY COMMUNITY

Fiona Latifi 1A

If [products] > [reactants], then K > 1. If [reactants] > [products], then K < 1.

Fiona Latifi 1A

I believe it's primarily Lavelle with some input from the TAs but I'm not certain.

Fiona Latifi 1A

I'm pretty sure those are all just names for the constant, K.

Fiona Latifi 1A

How do you determine the rate-limiting or slow step? Is it given in the problem which one is slow?

Fiona Latifi 1A

With the Arrhenius equation, we are trying to calculate K, the equilibrium constant.

Fiona Latifi 1A

You are usually told in the question whether it is in an acidic or basic solution.

Fiona Latifi 1A

I would go off of the topics listed in the outlines on Lavelle's website. These are the topics that may be tested on the exam.

Fiona Latifi 1A

The reaction of diamonds to graphite does occur, and it is spontaneous. It just occurs at an EXTREMELY slow rate.

Fiona Latifi 1A

Suggest two metals that could be used for the cathodic protection of a titanium pipeline. The answer is aluminum or magnesium because both are below titanium in the electrochemical series. My question is what is the result of being below titanium in the series? How does this mean that aluminum or ma...

Fiona Latifi 1A

Write the half-reactions and devise a galvanic cell (write a cell diagram) to study each of the following reactions: (a) AgBr(s) --> Ag1(aq) + Br2(aq), a solubility equilibrium (b) H+(aq) + OH-(aq) --> H2O(l), the neutralization reaction (c) Cd(s) + 2 Ni(OH)3 (s) --> Cd(OH)2 (s) + 2 Ni(OH)2 (s), the...

Fiona Latifi 1A

Yes, if there is no conducting solid an inert conductor must be added.

Fiona Latifi 1A

How does concentration affect cell potential?

Fiona Latifi 1A

The single line represents a porous disk or wall.

Fiona Latifi 1A

The learning objectives ask you to be able to derive this equation.

Fiona Latifi 1A

The Van't Hoff equation relates the change in K to change in temperature given delta H (the change in enthalpy).

Fiona Latifi 1A

Examples of state functions include density, internal energy, enthalpy, and entropy.

Fiona Latifi 1A

The Van't Hoff equation can be used to calculate K at a different temperature if delta H is known.

Fiona Latifi 1A

The Van't Hoff equation can be used to calculate K at a different temperature if delta H is known.

Fiona Latifi 1A

Cell potential is also known as cell voltage. It is used to measure the voltage difference in two halves of a cell.

Fiona Latifi 1A

1 dm = 0.1 m. A dm is a decimeter.

Fiona Latifi 1A

Gibbs free energy is a state function because it is determined by enthalpy and entropy, which are also state functions.

Fiona Latifi 1A

Because they have more positions or states that the molecule can be in. They have more atoms and are arranged in a more complicated way than less complex molecules.

Fiona Latifi 1A

Increasing the temperature increases the entropy of a system.

Fiona Latifi 1A

What are reversible and irreversible processes? What do reversible expansion and irreversible expansion mean?

Fiona Latifi 1A

This is usually done using the equation: delta G = delta H - T*delta S. Lavelle will likely cover this later.

Fiona Latifi 1A

Bond enthalpy is positive when bonds are being broken because this process requires energy. Bond enthalpy is negative when bonds are being formed because this process releases energy.

Fiona Latifi 1A

Endothermic reactions use heat as a reactant because they require energy. Exothermic reactions use heat as a product because they release energy.

Fiona Latifi 1A

Young Hall 3034

Fiona Latifi 1A

Ellen Amico 2L wrote:We have to pick them up ourselves in Young Hall 3034 between 9-5pm.

What day?

Fiona Latifi 1A

I believe we ran out of time and were unable to go over the last method.

Fiona Latifi 1A

If the coefficient of the reactant is a number other than 1.

Fiona Latifi 1A

Use Kp if the problem gives units of pressure. Otherwise, assume Kc.

Fiona Latifi 1A

A buffer solution is a composed of a weak acid and its conjugate base or a weak base and its conjugate acid. Buffers are used to maintain the pH of a solution at a consistent point.

Fiona Latifi 1A

If you are given pressure units, use Kp. Otherwise, assume Kc.

Fiona Latifi 1A

Is the solutions manual correct for this question? I am getting very different answers when completing the table. Thanks!

Fiona Latifi 1A

Yes, you can use it for partial pressures as well as concentrations and amount of moles.

Fiona Latifi 1A

Yes, if a solution is VERY acidic or VERY basic.

Fiona Latifi 1A

An explanation that I found online said that "the key difference between autoionization and autoprotolysis is that autoionization is the conversion of a neutral state of a chemical species into an ionized state whereas autoprotolysis is the transfer of a proton between two identical chemical sp...

Fiona Latifi 1A

The chemical reaction equation for ATP hydrolysis was in some of the textbook questions that were assigned but I don't think Lavelle ever specifically mentioned it in class.

Fiona Latifi 1A

The concentration of H3O+ is equal to that of OH- when the pH of the solution is 7. When the solution is neutral, the concentration of acid and base essentially cancel one another out.

Fiona Latifi 1A

No, you do not create an ICE table. You simply set K equal to (BrCl)^2/((Cl2)*(Br2)) and solve for the equilibrium concentration of Br2. This question just involves some simple algebra.

Fiona Latifi 1A

I believe that at least for this class, we will be told when a reaction is reversible. The double arrow is an easy way to determine this.

Fiona Latifi 1A

Solids and liquids are considered pure substances. Therefore they have an activity value of 1. So in equilibrium expressions, we do not include them because their value would just be 1.

Fiona Latifi 1A

Fiona Latifi 1A

For part b, you just substitute F for Cl into the chemical reaction equation from part a (Cl2 --> 2Cl). Using table 5G.2, you can obtain the value of Kc for the new equation. Next, you just make an ICE table and solve for X to find the equilibrium concentrations just like in part a. I'm not sure how...

Fiona Latifi 1A

This question asks whether Cl2 or F2 is thermodynamically more stable relative to its atoms at 1000 K. How would you determine this? Thanks!

Fiona Latifi 1A

According to the textbook, "activities are used to take into account deviations from ideal behavior". Since solids and liquids are considered to be completely pure substances, they do not deviate from ideal behavior. Therefore, their activity is equal to 1, not zero.

Fiona Latifi 1A

The ligand names in a coordination compound should be in alphabetical order.

Fiona Latifi 1A

205192823 wrote:Thank you, and also when the equation is pH=-log [H+] it is the same as pH=-log[H3O+]?

Yes

Fiona Latifi 1A

What exactly is an electron-withdrawing group? Can you give some examples? Thanks.

Fiona Latifi 1A

Lavelle posted this: https://lavelle.chem.ucla.edu/wp-conten ... pounds.pdf

Fiona Latifi 1A

First, alphabetize the ligands. Then, write the transition metal cation. Lastly, don't forget the roman numeral at the end of the name. If the complex has a negative charge, add -ate to the end of the metal name.

Fiona Latifi 1A

HF also has a relatively large pKa value and a small Ka value, which makes it a weak acid.

Fiona Latifi 1A

Arianna Perea 3H wrote:will we only have to calculate problems for strong acid/bases or weak ones as well for the final?

Only strong acids or bases

Fiona Latifi 1A

Question 6A.13 asks to identify whether certain compounds/molecules are Lewis acids or Lewis bases. How can you determine whether a substance is a Lewis acid or base? Thanks!

Fiona Latifi 1A

The test bank does not have any of Lavelle's previous exams. I checked.

Fiona Latifi 1A

Try to really focus on the content and not the fact that you are taking a test. Just treat the questions like regular practice problems that you have successfully completed in the past. I know this can be difficult but it helps me.

Fiona Latifi 1A

Emily_4B wrote:would we need to know this on the final?

Yes, you should know it for the final.

Fiona Latifi 1A

If a complex has a negative charge, we add -ate to the end of the metal name. However, I do not have anything in my notes about the -ite ending.

Fiona Latifi 1A

Amphoteric compounds are those that are able to either accept or donate a proton, depending on what other compounds they react with. For example, HCO3- can either accept a proton and become H2CO3 or donate a proton and become CO3 2-.

Fiona Latifi 1A

How do you determine whether a ligand is polydentate?

Fiona Latifi 1A

How do you identify the hybrid orbitals used by an atom? I am able to figure out the hybridization of an atom (as in question 2F.5) but am having trouble with this question. Thanks.

Fiona Latifi 1A

How exactly does cisplatin stop the DNA replication of cancerous cells?

Fiona Latifi 1A

What is the definition of a ligand?

Fiona Latifi 1A

My TA sent me this: Test 2 covers all material since midterm up to and including the list below: • Use the Valence-Shell Electron-Pair Repulsion Model (VSEPR) to determine the shape of inorganic, organic, and small biological molecules, cations, and anions. • Use bond dipole moments and shape to det...

Fiona Latifi 1A

How do you determine the direction in which a dipole moment points?

Fiona Latifi 1A

Ion-ion interactions are between two ionic molecules. Ion-dipole interactions are between an ion and a polar molecule. Dipole-dipole interactions are between two polar molecules. Dipole-induced dipole interactions are between a polar molecule and a non-polar molecule.

Fiona Latifi 1A

There is a peer learning session tomorrow night at Covel. I'm sure they'll provide some kind of practice problems there.

Fiona Latifi 1A

Did Dr. Lavelle ever talk about t-shape structures? I don't have it in my notes and a lot of questions include it. Can someone explain this shape?

Fiona Latifi 1A

It all seems to be mostly concept based. The only numerical content would be the strengths of bonds and bond angle degrees.

Fiona Latifi 1A

Referring to question 2E.5. Is ClO2+ trigonal planar or bent? The solution manual includes both in its answer.

Fiona Latifi 1A

Dispersion forces, induced dipole-induced dipole, LDFs, and Van der Waals forces are all equivalent. These interactions are always present and always attractive.

Fiona Latifi 1A

It's the energy required to break the bonds.

Fiona Latifi 1A

Larger electron-rich atoms are more polarizable. Usually, on the periodic table, polarizability decreases from left to right increases down a column.

Fiona Latifi 1A

Dissociation energy refers to the amount of energy required to break down a molecule into singular atoms.

Fiona Latifi 1A

How can you easily determine whether a compound contains ion-dipole forces? Is there some kind of rule to go off of? Thanks!

Fiona Latifi 1A

Weakest --> Strongest: London dispersion forces, dipole-dipole forces, hydrogen bonding

Fiona Latifi 1A

It's important that you understand how to calculate and use formal charge when drawing resonance structures. This will allow you to select the primary resonance structure of the molecule.

Fiona Latifi 1A

Radicals also only exist for a short amount of time because they are so reactive. Food supplements can react with radicals in the body before they cause damage to DNA, which is why it's important to eat plenty of vitamins and nutrients!

Fiona Latifi 1A

A coordinate covalent bond occurs when the shared electrons all come from the same atom. In a simple covalent bond, each atom supplies one electron. Coordinate covalent bonds are common between metals and ligands.

Fiona Latifi 1A

Generally, you would want to place the atom with the lowest electronegativity in the center of your lewis structure. Hydrogen can never be the central atom. To start your diagram, you should count the number of valence electrons for each atom so that you can determine how many electrons you need in ...

Fiona Latifi 1A

Could someone please explain the conceptual difference between electronegativity and electron affinity? Thanks!

Fiona Latifi 1A

Resonance structures are alternate structures of the same molecule so basically yes, your definition is correct.

Fiona Latifi 1A

Does anyone know if there will be videos and modules posted for the new content on Lavelle's website? Was this just for the introductory material? I found the videos and modules very helpful! Thanks.

Fiona Latifi 1A

It depends on what values you are given in the problem. If you are given the momentum, then use De Broglie's equation but if you are only given the frequency and asked to find the wavelength, then use c=lambda*v. It helps if you start out by writing the values that you have. This way, you can easily...

Fiona Latifi 1A

I would say that if the textbook specifically tells you to write the +, then you should write it.

Fiona Latifi 1A

This question asks us to explain why the ionization energy for oxygen is lower than that of either nitrogen and fluorine. I do not understand the explanation that the solution manual provides. Can someone explain this anomaly in a different way? Thanks!

Fiona Latifi 1A

The higher the effective nuclear charge of an atom, the atom can attract electrons more closely to its nucleus. The tighter an atom's hold is on its electrons, the smaller its atomic radius. In conclusion, a higher effective nuclear charge causes a lower atomic radius.

Fiona Latifi 1A

I have been watching the videos posted on Lavelle's website and completing the modules. Then throughout the week, I will read the sections in the textbook and complete all of the homework problems. Good luck!

Fiona Latifi 1A

The number of orbitals is based on the subshell. The s-subshell corresponds to 1 orbital, the p-subshell has 3, d-subshell has 5, and f-subshell has 7. I hope this was helpful!

Fiona Latifi 1A

1D.23 How many orbitals can have the following quantum numbers in an atom? (a)n=2, l=1 (b)n=4, l=2, ml=-2 (c)n=2 (d)n=3, l=2, ml=+1 I understand that the answer to B and D is 1 because they both have 3 quantum numbers that identify a single orbital. Could someone please explain how the answer to A i...

Fiona Latifi 1A

#38 on the Atomic Spectra Post-Module Assessment asks us to calculate the frequency of a photon emitted by a hydrogen atom when an electron makes a transition from the fourth to the second principal quantum level. A. -6.17 x 10^14 Hz B. 1.62 x 10^-15 Hz C. 6.17 x 10^14 Hz D. 2.71 x 10^-52 Hz I keep ...

Fiona Latifi 1A

To add on to the previous reply, increasing the intensity of light increases the number of photons, not the energy of the photons. One photon can eject one electron to do so, the photon must have either a short wavelength or high frequency so that the photons have enough energy.

Fiona Latifi 1A

Although it was once thought otherwise, the Bohr Model can only be used for the element of hydrogen, which has only one electron.

Fiona Latifi 1A

The equations used to derive the De Broglie wavelength equation cannot be used for electrons. Lavelle just demonstrated the way that the equation was originally derived so that we would understand where the equation comes from.

Fiona Latifi 1A

The equations that we learned on Monday that pertain to light and electromagnetic radiation cannot be used for electrons. They were just used today to demonstrate how De Broglie derived his wavelength equation.

Fiona Latifi 1A

If the De Broglie wavelength value is greater than 10^-15, it is measurable.

Fiona Latifi 1A

For parts A and C, you basically do it the same way. You just have to determine the number of ions in the compound. In part A, there is only 1 Cu2+ ion. In part C, there are 6 F- ions because it has a subscript of 6. So you would have to first divide by the molar mass for both parts A and C. Then, m...

Fiona Latifi 1A

For question E15, would OH be the sulfide of the metal? Or would it be (OH)2? Thanks.

Fiona Latifi 1A

In this question, you just add to find the molar mass. For Na2CO3 * 10H2O, you would compute 2(22.99) + 12.01 + 3(16) +10(18.02) = 286.19.

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