CHEMISTRY COMMUNITY

Samantha Toscano 2C

Thank you for the responses and for clarifying the question everyone!

Samantha Toscano 2C

It means that there is a constant rate.

Samantha Toscano 2C

The equation is t1/2=0.693/k for the half-life.

Samantha Toscano 2C

The half-life equation is t(1/2) = 1/ k[a]0 !

Samantha Toscano 2C

Yes, the catalyst will lower the activation energy for both reactions.

Samantha Toscano 2C

The catalyst will lower the activation energy, I remember this from the respondus question we got.

Samantha Toscano 2C

For this question, could someone explain why the mechanism makes a catalyzed reaction different from an uncatalyzed reaction?

Samantha Toscano 2C

Temperature and a catalyst impact the rate constant.

Samantha Toscano 2C

I remember this from a homework problem from this week, basically you add the order numbers up from the coefficients of the rates.

Samantha Toscano 2C

k1 and k2 are the rate constants for the forward reactions and k' is the rate constant for the reverse reaction.

Samantha Toscano 2C

Catalysts do speed up both of these reactions as they lower the activation energy.

Samantha Toscano 2C

The catalyst will cause the activation energy to be lowered, which will increase the reaction rates.

Samantha Toscano 2C

K is known as the rate constant.

Samantha Toscano 2C

Spontaneity refers to a natural process (something that just occurs naturally like something hot becoming something cold). In the case of speed (fast), the quickness of a process does not affect the spontaneous process.

Samantha Toscano 2C

Lower case k and upper case K are not related to each other.

Samantha Toscano 2C

Oxidation refers to the reducing agent where you lose electrons. Reduction refers to the oxidizing agent where you gain electrons. You can identify this from the change in the oxidation numbers.

Samantha Toscano 2C

The anode is oxidation which you can quickly identify since the electrons are on the right. The cathode is reduction and the electrons are on the left.

Samantha Toscano 2C

The anode will have the electrons on the right & the cathode will have the electrons on the left.

Samantha Toscano 2C

This can help you with determining spontaneity based on Delta G.

Samantha Toscano 2C

Delta S (system): solve for S the same way we have been solving it from Delta G = Delta H (T * Delta S)
Delta S (surroundings): solve using -Delta H/T
Delta S (universe): add solutions from system and surrounding

Samantha Toscano 2C

This image is an easy way to see spontaneity based on deltaG

Samantha Toscano 2C

Negative Delta G is spontaneous because K < 1 (product favored) and since no additional energy is required for the reaction to occur, it is a spontaneous reaction (occurs naturally).

Samantha Toscano 2C

You can determine on what side they go on if you know that Q>K favors reverse reaction and Q<K favors forward reaction. Based on this you determine on which side this occurs on the graph.

Samantha Toscano 2C

Work done on the system is positive.

Samantha Toscano 2C

Gibb's free energy is negative when spontaneous because it should be less than zero when a natural process occurs (spontaneous processes are negative). The system releases energy making the process a natural one.

Samantha Toscano 2C

This equation is used to find the work done by constant pressure.

Samantha Toscano 2C

The equation stands as U=q+w, but we need to determine if the work is + or -. Then if the work is either positive or negative, you input that value into the equation. For example, W= - 109 then you would write it out like this (U=q+ (-109)).

Samantha Toscano 2C

+ work = work is done on the system
- work = work is done by the system

Samantha Toscano 2C

Extensive properties focus on the amount of material present while intensive properties do not.

Samantha Toscano 2C

"q" represents heat, remember this when looking at equations working with heat and work

Samantha Toscano 2C

To see everything on the Midterm, check Dr. Lavelle's website and there he has a link to the Outlines 1-3 for the Midterm.

Samantha Toscano 2C

I know that Kelvin has to be used for the equation PV = nRT

Samantha Toscano 2C

Heat moves through a system
Enthalpy is the total energy of a system

Samantha Toscano 2C

Breaking bonds require energy so it is an endothermic process.

Samantha Toscano 2C

For an Endothermic reaction, heat will enter. Since a cake requires heat to bake it will be Endothermic.

Samantha Toscano 2C

Exothermic --> heat will Exit
Endothermic --> heat will ENter

Samantha Toscano 2C

State property refers to initial and final states.

Samantha Toscano 2C

Exothermic -> releases heat
Endothermic -> absorbs heat

Samantha Toscano 2C

The process of melting would be an endothermic process since heat is required to melt.

Samantha Toscano 2C

An open system allows for energy and matter to pass through
A closed system allows energy to pass, but not matter
And an isolated system does not let either pass

Samantha Toscano 2C

(Mono) meaning one, means that the weak acid can only donate one proton.

Samantha Toscano 2C

Yes! Ka is for the pH and Kb would be for pOH

Samantha Toscano 2C

K would be the rate at equilibrium and Q is the reaction quotient.

Samantha Toscano 2C

R is constant and cannot be changed. However, it depends on which units are being used.

Samantha Toscano 2C

Yes if Q and K are equal to each other then they are at equilibrium.

Samantha Toscano 2C

Yes, the coefficient will give you the number you will need to put before x.

Samantha Toscano 2C

Yes I believe so, the only thing to make sure about is what the questions is asking you to solve, either pressure (Kp) or concentration (Kc).

Samantha Toscano 2C

The pressure will decrease if volume increases since they have an inverse relationship.

Samantha Toscano 2C

I see 25 degrees very often in problems and its basically room temperature and we have it as a reference temperature.

Samantha Toscano 2C

Q is defined as the ratio of products to reactants when the reaction is not at equilibrium and it can be solved for in the same way as K is!

Samantha Toscano 2C

We take them online on CCLE, usually between 15-20 multiple choice questions on concepts and math problems. We can use a periodic table and equation sheet which he provides.

Samantha Toscano 2C

In lecture, Dr. Lavelle described a quick way to tell if a reaction would shift left or right based in the decrease in volume and more moles of gas either left or right of the reaction. Would there be an increase in volume that can be applied ?

Samantha Toscano 2C

Yes, you need to balance it in order to have an accurate number of moles on each side, that will give you the accurate K.

Samantha Toscano 2C

Besides it just applying to the changing of physical parameters (P&T), is their other definition for this principle to have some more clarification?

Samantha Toscano 2C

Could someone briefly explain how to use the ICE table necessary to solving this problem ?

Samantha Toscano 2C

Yes! Acidic (1-6), Neutral (7), Bases (8-14)

Samantha Toscano 2C

These are some problems from the homework that can help you out!

Samantha Toscano 2C

Use [H+] = 10^-pH.
Use [OH-] = 10^-pOH. To find pOH -> pOH = 14 - pH

Samantha Toscano 2C

Do we always use 1.0 x 10^-14 as the numerator to solve for [H+]. Is this just part of the formula?

Samantha Toscano 2C

For this question, you can pretty much follow along to what you have done in previous, achieve questions like in #5. Best ways to solve for the pH are to first solve for [H+] using pH = -log[H+] or using [OH-] to solve for [H+] = 1.0 x 10^-14 / [OH-] and then solving for pH using pH = -log[H+]. Then...

Samantha Toscano 2C

Hi! To tell apart the strong acids from the weak acids, I looked at the list strong acids. What would be the easiest way to tell apart weak acids from weak bases?

Samantha Toscano 2C

What is the difference when finding the coordination number for a coordination compound vs. finding the coordination number for a metal complex?

Samantha Toscano 2C

I believe it's just good to remember that tetrahedral and square planar will always have a coordination number of 4.

Samantha Toscano 2C

hi ! the homework week 9 definition of a complex ion (a charged species consisting of a metal ion surrounded by ligands) is another simplistic way of seeing it.

Samantha Toscano 2C

Tetrahedral and Square Planar will always go with the coordination number of 4 !

Samantha Toscano 2C

hi ! I had some trouble solving some problems from the week 9 homework, and I get confused on which number is the coordination number since some have numbers inside and outside the brackets...

Samantha Toscano 2C

Hi ! Can anyone give some tips on how to name these coordination compounds? I understand that the prefix will be based on the coordination number... (ex. penta = coordination number #5)

Samantha Toscano 2C

How exactly can we determine the relative position of the hydrogens in the structures when the 3 structures are similar? How do we single out the two structures which have them in the same place?

Samantha Toscano 2C

Hi, for the last part of this question, why would the structures of C3H4 not be resonance structures of one another? Would it be because of the different bonds used?

Samantha Toscano 2C

What main angles do we have to know for sure? The ones which I saw come up a lot on this week's homework was 109.5, 90, and 180.

Samantha Toscano 2C

For this question, by finding the hybridization, we can determine the number of hybrid orbitals?

Samantha Toscano 2C

Just to clarify, when counting for sigma bonds, we only count the bonds shared with other molecules but never include the lone pairs?

Samantha Toscano 2C

Can someone please simply explain the seesaw shape ?

Samantha Toscano 2C

When building lewis structures, could we say that carbon likes to have 4 bonds, nitrogen likes to have 3, oxygen likes to have 2, and fluorine likes to have 1? Can we use this to follow the building of the lewis structure?

Samantha Toscano 2C

What would be the easiest way to distinguish a polar bond from a non polar bond? Like from using this example: C-H (a nonmetal bonded with a nonmetal) vs. C-O (again a nonmetal bonded with another nonmetal)?

Samantha Toscano 2C

When finding the electron configuration for ions, is the highest energy level always removed if there is a positive charge?

Samantha Toscano 2C

Just to clarify, when looking at a dipole and an induced dipole created by the original dipole, the connection between the partially charged negative of one dipole and positively charged of the other dipole would be defined as the temporary London Force between these dipoles?

Samantha Toscano 2C

hi ! this question is simply asking about the previous questions, by finding the answer which does not match the previous ones, you can find that using formal charge to determine the plausible structure is the answer.

Samantha Toscano 2C

Can someone explain how we can identify when a molecule shows ONLY London (dispersion) Forces? I was confused from a problem on the homework on how to find only these forces impacting the molecule.

Samantha Toscano 2C

Hi! I'm still pretty confused on how to identify elements as acids or bases. If anyone could please simply describe the two that would be very helpful thank you !

Samantha Toscano 2C

Hi! I'm pretty confused on how exactly to build multiple resonance structures. Usually, I can figure out the first one but when asked to figure out two or more, it gets challenging. Could anyone please explain the overall method of how to figure out the resonance structure? Such as, the general step...

Samantha Toscano 2C

Thank you very much for these responses !

Samantha Toscano 2C

For this problem, when finding the Formal Charge of N, why is the lone pair 2?

Samantha Toscano 2C

For Midterm 2, just focus on the material we have learned from after Midterm 1 until the day we take Midterm 2. It will not be cumulative, that's only on the final.

Samantha Toscano 2C

If we do get another practice question, it will probably be worth less points than the previous one

Samantha Toscano 2C

thank u so much for catching that ! it worked now !

Samantha Toscano 2C

For #13, I thought I followed the correct steps to find the E(electron), but for this second part of the problem, my answer is wrong again and again. I've gone back many times but I am not sure what I am doing wrong, can someone please check to see any error in my calculations?

Samantha Toscano 2C

For the third row on this problem, I have 300 MHz and solved for the wavelength perfectly up until the final answer. I got 0.01 * 10^2 m and in the odd-answer index, the answer is 1 nm. How is the answer 1 nm when I converted 0.01 * 10^2 to nm and got something different?

Samantha Toscano 2C

Thank you! So in that case, would it be that when I use plank's constant, I use 6.63 instead of 6.626 ?

Samantha Toscano 2C

I'm solving some of the homework problems, but my answers are a little off from the one given in the odd-number answer key. For example, I get 344 nm instead of 340 nm, even though I'm doing the question properly. Is this alright, since my answer is very close?

Samantha Toscano 2C

I believe your TA will go over the question with you to ensure that everyone understands how respondus is going to work!

Samantha Toscano 2C

Wavelength and frequency are inversely related. For instance, a wavelength with a higher number of (nm) will have a smaller frequency than that of a wavelength which has a lower number of (nm). This wavelength will have a larger frequency!

Samantha Toscano 2C

Wavelength and frequency share an inverse relationship; they are inversely related. Therefore, a wavelength of a high number of nm will have a smaller frequency than that of a wavelength with a lower number of nm.

Samantha Toscano 2C

Yes ! You can print the equation sheet to have it available from Dr. Lavelle's website

Samantha Toscano 2C

The material on the test will be from Week 1 to the end of Week 3's lecture from Friday !

Samantha Toscano 2C

thank you that helped a lot (:

Samantha Toscano 2C

These are some examples of significant figures ! 3.73 would be 3 significant figures & 5.7 would be 2 significant figures. As long as you remember the rules, you'll have no problem with identifying them (:

Samantha Toscano 2C

Kinda basic, but can anyone explain how to solve for units like let's say 3 * 10^-8 m/s divided by 6.2 * 10^-7 m ? Or is there a section I can look at? The exponents throw me off...

Samantha Toscano 2C

One of the best study tips that I learned from my psych class: DISTRIBUTE YOUR STUDY SESSIONS ! Always schedule a consistent time where you can review topics with time ! It will be one the the best ways to learn in the long-run (:

Samantha Toscano 2C

Yeah, sometimes when you're not sure if you should round or not, I guess it depends on looking at the numbers. Since, Oxygen is 15.999 and all the 9s are the highest number, it would just be best to round up and use 16. Hope this helps ! (:

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