CHEMISTRY COMMUNITY

Lara Kristine Bacasen 1L

Its good to know for which order what is on the axes

Lara Kristine Bacasen 1L

A good way to remember it is PANIC
Positive - Anode
Negative Is Cathode

Lara Kristine Bacasen 1L

Hello Dr. Lavelle, I want to thank you for all the work that you have put in for your classes, especially this quarter. This quarter's ending caught us all by surprise but you handled wonderfully. I hope you get a good night's rest now that finals are over and take care of yourself at this time. I w...

Lara Kristine Bacasen 1L

Was there a typo on the delta G problem for the final?

Lara Kristine Bacasen 1L

Hello Dr. Lavelle,

Thank you so much for your hard work this quarter. Your enthusiasm is inspiring and I hope you stay safe for these upcoming months.

All the best!

Lara Kristine Bacasen 1L

In lecture I think he derived the first, second, and zero rate laws. I think he said in lecture that he wasn't going to do it for the Arrhenius equation. I'm not entirely sure though.

Lara Kristine Bacasen 1L

How do you know which elementary step is the slow step and which one is the fast step?

Lara Kristine Bacasen 1L

For an elementary one step reaction, the coefficient of the the concentration can be used as an exponent but not an overall equation. But yeah the elementary coefficients don't equal the overall exponent that tells you the rate law.

Lara Kristine Bacasen 1L

The equation sheet is always the same. If anything they will also give you the thermodynamic values and E naught values like the midterm.

Lara Kristine Bacasen 1L

A in the Arrhenius Equation the frequency of collisions in the correct orientation.

Lara Kristine Bacasen 1L

And how do you determine if something is a product of the cathode and product of an anode in Electrolytic Cell problems?

Lara Kristine Bacasen 1L

So I was looking at the examples and self tests for these and I have no idea why they are doing what they are doing. Like for self test 6O.1B It asks you to "Predict the products resulting from the electrolysis of 1 M NaBr(aq). The answer takes the half reactions of elements Br, O2, and H. Why ...

Lara Kristine Bacasen 1L

2NO3-(aq) + 8H+(aq) + 6Hg(l) --> 3Hg2+(aq) + 2NO(g) + 4H2O(l) So first you have to figure out what is being oxidized and what is being reduced. We see that Hg goes from no charge to having a 2+ charge. It looses electrons so it is being oxidized. Now you know that is on the left side of the cell dia...

Lara Kristine Bacasen 1L

D. Pt(s)|O2(g)|H+(aq)||OH-(aq)|O2(g)|Pt(s) So to get the half reactions remember that the left side is always the anode which is oxidizing and the right side is the cathode which is reducing. When looking at the anode, the molecules O2 and H+ are interacting in oxidation. Since something should be l...

Lara Kristine Bacasen 1L

Umm. I'm not sure if you need to know this. He did say that graphite is less used than Platinum but both are the most commonly used. I think those are put in the cell diagram to see if you know that you don't need to use it. I believe the graphite acts better as a cathode electrode in electrolysis b...

Lara Kristine Bacasen 1L

The galvanic diagram should be always be shown with the anode on the left and cathode on the right.

Lara Kristine Bacasen 1L

It should be on the outermost part of the cell diagram. I think it useful that way too because sometimes the solid doesn't interact in the redox reaction like the Platinum electrode or the graphite electrode.

Lara Kristine Bacasen 1L

So Dr. Lavelle mentioned this in lecture. You need a solid electrode for the cell diagram and when there isn't for one side you need to have a element that wouldn't interact with the solution . An inert electrode such as Pt is necessary when both oxidized and reduced species are in the same solution...

Lara Kristine Bacasen 1L

The salt bridge is used to maintain charge balance because the electrons are moving from one-half cell to the other. The electrons flow from the anode to the cathode. The oxidation reaction that occurs at the anode generates electrons and positively charged ions. The electrons move through the wire,...

Lara Kristine Bacasen 1L

I think it is important to get the value Columbs cause the units for the constant is Columbs per mole

Lara Kristine Bacasen 1L

In acidic solutions, to balance the O's you have to use H2O on the half reactions. I suggest you look at Toolbox 6K.1 for the whole process.

Lara Kristine Bacasen 1L

The problem should usually tell you if it is in an acidic (H+) or basic (OH-) solution.

Lara Kristine Bacasen 1L

Can someone explain why the reaction free energy depend on pressure and the equilibrium constant?

Lara Kristine Bacasen 1L

Hey did Lavelle mention any biological applications in lecture concerning thermodynamics? I know the outline mentions ATP hydrolysis but I don't know if he mentions anything else.

Lara Kristine Bacasen 1L

He spent a lot of time in class explaining and deriving it so there is a good chance that it will. It is also in outline for Thermodynamics: The second and third laws.

Lara Kristine Bacasen 1L

So for an exothermic reaction, energy is given off and thus makes the value negative. When you increase the temperature it puts energy into the system causing it to favor an endothermic reaction which is the revers. Thus the equilibrium will shift left. It's the same thinking for Endothermic reactio...

Lara Kristine Bacasen 1L

The K value can tell you if it is spontaneous or not. A spontaneous reaction has a negative delta G and a large K value. A non-spontaneous reaction has a positive delta G and a small K value.

Lara Kristine Bacasen 1L

So the order of entropy in states are solids<liquids< aqueous solutions<gases. Solutions have a greater entropy than pure liquids as the particles in a solution are more separated and solvent molecules separate the solute particles. There are more molecular positions this solution can take as oppose...

Lara Kristine Bacasen 1L

It's probably good to remember the monoatomic ones. We were going over some practice with a TA and on her previous midterm she had one that used one of those values. We asked about the diatomic values and she said she wasn't sure.

Lara Kristine Bacasen 1L

For me I remember the graphs he showed us in lecture for the reversible and irreversible reactions. For the reversible reactions the curve is smooth while the irreversible reaction is like a step. You can roll a ball up and down the curve but if you try to roll a ball on the step its can't go back u...

Lara Kristine Bacasen 1L

Combustion is an exothermic reaction and gives off heat so the delta H should be negative.

Lara Kristine Bacasen 1L

So an isothermal process occurs under a constant temperature (so delta T/Change in temperature is 0) while an Adiabatic process occurs without any heat transfer between a system and its surrounding. In isothermal processes there is a heat transfer that is observable and work is done due to the chang...

Lara Kristine Bacasen 1L

Large volume change can increase entropy and this is mostly seen in systems with gas since they can undergo large volume changes.

Lara Kristine Bacasen 1L

Most of the examples we see in the book show water in the liquid state. The phase of water is determined by the temperature at which the reaction occurs. Most reactions occur at room temperature,25 degrees Celsius, at which water is a liquid. If the temperature is greater than the boiling point, the...

Lara Kristine Bacasen 1L

Just make sure all the units match up/cancel out correctly.

Lara Kristine Bacasen 1L

Yeah, I don't think we went over it yet but you need to know the change Entropy, Temperature, and change in Entropy. With this you use an equation to find the Gibbs Free Energy and the sign will tell you if it is spontaneous. I believe if it is negative it will be spontaneous.

Lara Kristine Bacasen 1L

Yeah, and if anything you should practice the problems with the derivatives to see how challenging it would be at your current knowledge.

Lara Kristine Bacasen 1L

There is a decrease in enthalpy and an increase in entropy of the system

Lara Kristine Bacasen 1L

Also, if you are not sure if you are able to approximate for the acid and base problem. You can employ the 5% rule which is look at the amount protonated/ionized. If the precent is over 5% you shouldn't have approximated for x.

Lara Kristine Bacasen 1L

Can someone explain the statement "Enthalpy is a state function and therefore must be additive"? It was in lecture.

Lara Kristine Bacasen 1L

Yeah, the path doesn't matter which is why he was able to show us different ways to get the answer that we need.

Lara Kristine Bacasen 1L

When you look at the heating curve of water it shows you the phase changes and the amount of energy it takes to get it to that phase. When the line increases in temperature the increasing line is when they are in their states (solid, liquid, gas) and the plateaus are where there is phase change. In ...

Lara Kristine Bacasen 1L

The Heating curve he showed in lecture only pertains to water since each element has different boiling points. When the line increases in temperature the increasing line is when they are in their states (solid, liquid, gas) and the plateaus are where there is phase change. In lecture he asks steam b...

Lara Kristine Bacasen 1L

In context with gases, yes the above response about volume and pressure being inversely related is correct according the Boyle's law. However, the effect of volume changes on equilibria(gas) is different. If there is a change in temp., volume, or concentrations the system will respond to reach equil...

Lara Kristine Bacasen 1L

I'm not sure if this answers your question but if the temperature is the same the concentration does not change the equilibrium constant (k). However, if you change the temperature it does change the equilibrium constant. So temperature is the only thing that can affect the the equilibrium constant...

Lara Kristine Bacasen 1L

I believe we approximate because the value is so small that it is insignificant when calculating the amount.

Lara Kristine Bacasen 1L

It should say it on the equation sheet.

Lara Kristine Bacasen 1L

I'm not exactly sure but I believe a buffer has an either a weak acid with its conjugate base in form of a salt or a weak base with its conjugate acid in salt form. As we see, if we add either an acid or a base with the buffer, it is able to neutralize both ways.

Lara Kristine Bacasen 1L

I'm not sure if this answers your question but if the temperature is the same the concentration does not change the equilibrium constant (k). However, if you change the temperature it does change the equilibrium constant.

Lara Kristine Bacasen 1L

It's not the same because that isn't the correct k ratio for equilibrium.

Lara Kristine Bacasen 1L

I believe you're correct considering it's the inverse. Just look at the ideal gas law PV = nRT

Lara Kristine Bacasen 1L

It would be good to look through the given questions from the textbook to see if they ask for any of the other rules. It will probably give you a good idea of how in depth of what you need to know.

Lara Kristine Bacasen 1L

If K is 1 the amount of products and reactants are roughly the same at equilibrium. It is rare to have a situation in which energy of the product and reactant are equal.

Lara Kristine Bacasen 1L

I'm pretty sure we don't have to do anything. Some people have a different number of posts because that is how many times they interacted here on chemistry community. You can ask your TA if you are still concerned, as they are the ones who will be checking for your responses. Oof also change your se...

Lara Kristine Bacasen 1L

We should be able to identify them since they behave differently when they dissociate in water. Strong acids are completely deprotonated while weak acids are incompletely deprotonated. It will probs be easier if you do so there is less doubt in what are a strong acid is.

Lara Kristine Bacasen 1L

All polydentates can form Chelates, yes.

Lara Kristine Bacasen 1L

I believe you would know because the atom has a lone pair that enables it to bind to the central atom. For example, H2O is written as OH2 in the ligand molecule to show that the O binds the ligand to central atom. I believe the book also said if there is any ambiguity the linking atom can be underli...

Lara Kristine Bacasen 1L

TA's should be checking after every Sunday to see if you interacted at least five times in the previous week.

Lara Kristine Bacasen 1L

It's the number of points at which ligands are attached to the central atom. Remember some ligands can connect to the central atom twice (polydentate) so it's not exactly the number of ligands.

Lara Kristine Bacasen 1L

So when trying to find the oxidation number, the way the solutions manual did it was that they essentially did a find x problem. So for the complex they should give you the overall charge and by looking at the individual ligands we will know what charge they have. The book has a table that gives the...

Lara Kristine Bacasen 1L

The whole process he explained for naming is in the text book under Tool box 9C.1 page 723. I suggest you take notes how have it as reference. Underneath should be examples of how to name. Essentially, 1) Ligands named first in alphabetical order (ignoring any greek prefixes) - some neutral ligands ...

Lara Kristine Bacasen 1L

Yes but the book says in some cases the order of ligands in the name is not the same order in formula. The question asks us to write the formula for sodium bisoxalato(diaqua) furrate(III). The molecules for the ligands are C204 and OH2. When writing the formula it says to write chem symbols in alpha...

Lara Kristine Bacasen 1L

Polydentate Ligands are ligands that can attach at several bonding site (book definition). It has more than one donor atom. So that means they most likely have multiple lone pairs to bind to central atom. So yes if it has two lone pairs it is polydentate. The ring is formed with the ligands and the ...

Lara Kristine Bacasen 1L

I'll get some of that H20, too.

Lara Kristine Bacasen 1L

Why is diaqua written first in the formula? Shouldn't it be C204 first since it should be alphabetical order?

Lara Kristine Bacasen 1L

Yes, just remember that dipoles are the partial charges that arise in polar molecules and these dipoles interact with each other. Thus the name dipole dipole.

Lara Kristine Bacasen 1L

I think it doesn't form hydrogen bonds due to the charges on the atoms. We know hydrogen bonds form because the positive charge of the H is attracted to the negative charge of the small and highly electronegative atom. When I was looking at the formal charges of CHF3 I saw that there was no real pos...

Lara Kristine Bacasen 1L

So generally for Ion dipole interactions, they are strong for small highly charged ions. They often hydrate in compounds. So we see in the periodic table that Be2+ is smaller than Al3+. However we also know that the charge makes a difference and Al has more charge. But since the distance for Be2+ is...

Lara Kristine Bacasen 1L

I don't think we need to know the exact angle. But we should know that it will be a smaller angle due to the lone pair.

Lara Kristine Bacasen 1L

I think you're referring to the general formula for classifying the shapes. The general formula is AX(subscript n)+E. A is the central atom X is atoms surrounding central atom and the n is the number of those X atoms. Molecules w/ the same formula have the same general shape. So CH4 and CH3Cl are AX...

Lara Kristine Bacasen 1L

I'm taking the class. I asked my sister about taking the lab (she attends the school) and she recommends to hold of on taking the lab till you're done with the 14b class. She said latter on it's actually a struggle to take classes you like if you pack your classes early on. Also if you're taking a c...

Lara Kristine Bacasen 1L

I did the brackets around the molecule to indicate charge. But I also did the formal charge calculations of each atom and listed them next to each individual atom to make sure.

Lara Kristine Bacasen 1L

I believe it's still valid to do these problems since he was talking about it during the previous lectures recently. At least I did the problems for 2D.

Lara Kristine Bacasen 1L

He said we didn't need to. We should know the general trends like how bond is most likely ionic if the difference in electronegativity between the two is greater than 2. For covalent, less than 1.5 I believe. Just remember that depending on the bonded pair the bond can be more covalent or ionic. I s...

Lara Kristine Bacasen 1L

I'm not sure how strict they are gonna be if they are gonna ask about angles. I think they are gonna ask just for what shape is called and why arises. Maybe give you a molecule and ask what shape it takes and why. My best suggestion is practice problems and flashcards/quizlet.

Lara Kristine Bacasen 1L

I agree, if the molecule is the same the sharing of electrons should be the same and will induce a partial charge due to their electronegativity.

Lara Kristine Bacasen 1L

Yeah, the only orbitals are s, p, d, and f. We can also see this visibly in the periodic table.

Lara Kristine Bacasen 1L

To add on, how I understand it is that one atom is more greedy than the other. One of the atoms needs the electron more than the other and this causes it to pull the electron closer to itself and farther from the other atom it is getting the electron from. This induces a partial charge, a negative c...

Lara Kristine Bacasen 1L

Yes, sometimes one of the atoms need the electron more than the other and it creates a partial charge among the atoms.

Lara Kristine Bacasen 1L

So when it says all ionic bonds have some covalent character it is just talking about how covalent bonds are less soluble right? And the higher the distortions/polarization the more covalent character means it becomes less soluble compared to other salts?

Lara Kristine Bacasen 1L

It should be since we are going over them. The midterm is up to Concept 2D in the textbook which is Properties of Bonds.

Lara Kristine Bacasen 1L

You usually see it with nonmetals and metals as they exchange elections. Usually the nonmetals take elections from the metals so both can become more stable.

Lara Kristine Bacasen 1L

I believe they bend away from each other because as the atoms are connected together in the molecule they continue to interact. Meaning, the non-central atoms of the molecule are trying to stay away from each other/ repel each other making the structure more angular. He used water as an example in l...

Lara Kristine Bacasen 1L

Everything that will be on the midterm will be from the first lecture to the lecture on Friday. So fundamentals to Chapter 2D.

Lara Kristine Bacasen 1L

Yes, everything from the beginning to 2D in the text book will be on the test.

Lara Kristine Bacasen 1L

Nope we don't sadly. It's good to make a friend so you can get notes or at least the topics of what was in lecture. You can also go to the study programs he offers to catchup.

Lara Kristine Bacasen 1L

He hasn't said anything about uploading any new ones. You should email him. Or he will eventually see this.

Lara Kristine Bacasen 1L

When interpreting some chemical reactions it would be good to know which one is which because it tells you what types of bonds are formed or what their properties are. The periodic table is organized in a way where you would know which is a metal, nonmetal, or metalloid. The metalloids are kinds pos...

Lara Kristine Bacasen 1L

Generally no, you should try find someone who can tell you the topics and try to read through what he went over. Like today Lavelle went over trends. Online there are documents that tells you the main topics we should understand. The video modules also help. If you still don't understand after tryin...

Lara Kristine Bacasen 1L

Yes that is correct but is that the correct question for 1B-3?

Lara Kristine Bacasen 1L

I believe it is under Atomic spectra. My notes says e- in atoms (and molecules) also absorb/emit quanta of energy which gives atomic (and molecular spectra. Atoms and molecules only absorb or emit unique frequencies that are allowed by their unique electronic structure. The exception is 'black bodie...

Lara Kristine Bacasen 1L

Don't think so. They are probably on the equations sheet or given. When you're trying to predict something thought, just remember that the electron is the lightest out of the three for the masses or essentially the electron doesn't influence mass of an atom.

Lara Kristine Bacasen 1L

So in lecture he used cation as an example. Cations are positive charged atoms because an e- is removed. The configuration is the same except a e- on the furthest/weakest orbital is removed. For anions you add an election to the furthest orbital.

Lara Kristine Bacasen 1L

Like he says, there is always step up programs, office hours, etc. He has loads of resources like physical visits and videos online you can do to review on your own time. They said some of the homework problems are on tests but I'm not sure if they are on the midterms. However, constant practice wit...

Lara Kristine Bacasen 1L

The Equation sheet is always given I believe. The same one that they gave us on the first test is on the website under the title constants and equations.

Lara Kristine Bacasen 1L

I'm not sure myself. I think you should be able to ask your RA since they are recording their section's activity. But it's best for you to keep track of how many posts you have. Usually it says it under your name how many posts you made whether it be a question or comment. But sometime it adds one t...

Lara Kristine Bacasen 1L

Another way of thinking of the thresh hold energy is hearing. We can only hear something if it reaches a certain amount of Hz, any thing lower than that amount we can't hear it (of course there is also too high we wouldn't be able to hear it but that is beside the point). Also like moving a heavy ob...

Lara Kristine Bacasen 1L

Agree with everyone. They are kind enough to provide the equations and constants for us and it is easier to memorize them so you don't have to look over it constantly. But really you should make sure how to use the constants and equations. The equations will show the variables but not what they repr...

Lara Kristine Bacasen 1L

C is a constant but of course although it is widely accepted this constant assumes particular conditions like how light particles has no resting mass. There is also quantum field theory that argues the vacuum isn't always empty and has elementary particles that pop in and out if existence which can ...

Lara Kristine Bacasen 1L

The variable E denotes that a photon/energy particle of light is proportional to its frequency (v). Variable h relates the energy in one photon of electromagnetic radiation to the frequency of that radiation. It links the particle's frequency with its energy. So essentially, I believe that this equa...

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