CHEMISTRY COMMUNITY

KatelinTanjuaquio 1L

Nope, only temperature can change equilibrium constant.

KatelinTanjuaquio 1L

Example 14.18 is the following: Screen Shot 2019-03-16 at 3.23.13 AM.png Why is the second half-reaction reversed? I thought that reduction reactions can be identified by the one having the least negative cell potential, and 0.80 is greater than 0.22. Is it because the picture shows that reaction on...

KatelinTanjuaquio 1L

I was having trouble with the question below: Screen Shot 2019-03-15 at 10.11.24 PM.png However, when I was computing it, I could not figure out how to cancel oxygen. When I looked at the solutions manual, I don't understand why they multiplied only oxygen by 3/2 in the second equation, but not the ...

KatelinTanjuaquio 1L

When I input the value of 8.314x10^-3, I get the same answer as the solution manual. However, the solution manual uses 8.314x10^-2 for some reason, and I don't know why. When I plug that value into my work, I get different answers for the whole thing.

KatelinTanjuaquio 1L

You separate them with a single vertical line when they cannot physically mix together. Because liquids are in contact with each other, they are separated by a comma instead. Solids cannot "mix."

KatelinTanjuaquio 1L

It's currently on the equation sheet posted on Dr. Lavelle's website, so I would think so.

KatelinTanjuaquio 1L

Congratulations Michelle on your hard work! Here are some pictures I took.

KatelinTanjuaquio 1L

I think it's supposed to be an equal sign, maybe? The equation for that doesn't involve subtraction.

KatelinTanjuaquio 1L

Question 15.63 of the sixth edition asks, "The rate constant of the reaction between CO2 and OH- in aqueous solution to give the HCO3- ion is 1.5*10^10 L*mol-1 at 25 degrees celsius. Determine the rate constant at blood temperature 37 degrees celsius, given that the activation energy for the re...

KatelinTanjuaquio 1L

The half life of a first order reaction is dependent only the rate constant, not the initial concentration.

KatelinTanjuaquio 1L

The final is cumulative, so it will cover material from all quarter. I recommend looking over the outlines & doing homework problems!

KatelinTanjuaquio 1L

The overall order for a reaction is determined by the combined order of the reactants. In essence, you add up the exponents. Given that rate=k[A]^N*[B]^M*[C]^L, to find the overall order, you add N+M+L. For example, given that rate=k[A]^2[B]^2[C]^-1, the overall order is found by adding up the expon...

KatelinTanjuaquio 1L

I like to go to office hours and workshops. I prefer Lyndon's workshops but it's usually full by 6:15.

KatelinTanjuaquio 1L

Question 14.11 of the sixth edition, part d states: Write the half-reactions and the balanced equation for the cell reaction for each of the following galvanic cells. Pt(s) | O2(g) | H+ (aq) || OH-(aq) | O2(g) | Pt(s). I understand how the anode reaction is derived, but how is the cathode reaction f...

KatelinTanjuaquio 1L

Porous disks are used when both electrodes are in the same cell, whereas a salt bridge is used when they are in two separate cells. Ions provided by the electrolyte solutions move between the two compartments to complete the electrical circuit.

KatelinTanjuaquio 1L

Why is it that we do not need to multiply the standard reduction potential by a coefficient even though the reaction is multiplied by a coefficient? How does this differ from multiplying the reaction by -1 when flipping the reaction?

KatelinTanjuaquio 1L

What is the purpose of platinum in the cell diagram Cu(s) | Cu 2+ || Fe3+ (aq), Fe2+ (aq) | Pt(s)? I understand that Pt works as an electrode, but is it the same as the reaction Fe3+ + Cu(s) --> Cu2+ (aq) + Fe2+ (aq), just the Pt is not shown?

KatelinTanjuaquio 1L

Something that helps me is being able to understand what equations are used for. When I am not familiar with equations yet, it is helpful to take an equations sheet and label all equations that I may need to know for that section. Then, when I begin to answer questions, I determine which equation to...

KatelinTanjuaquio 1L

During class, we began to learn about Gibb's Free Energy, specifically using the equation deltaG=H-T*deltaS.

KatelinTanjuaquio 1L

Here's another copy of the serenading last week!

https://drive.google.com/file/d/11NSJOI ... sp=sharing

KatelinTanjuaquio 1L

An isolated system is one in which neither matter nor energy can be exchanged with its surroundings. Delta U will be 0 because, no matter the amount of time, the change in internal energy cannot be changed in an isolated system.

KatelinTanjuaquio 1L

I am having trouble with problem 8.25 of the sixth edition. This is the question: A constant-volume calorimeter was calibrated by carrying out a reaction known to release 3.50 kJ of heat in 0.200 L of solution in the calorimeter (q =-3.50 kJ), resulting in a temperature rise of 7.32 C. In a subseque...

KatelinTanjuaquio 1L

Inert gases do not affect equilibrium so long as volume stays constant.

KatelinTanjuaquio 1L

I think it will probably go up to what the class website says, up to the end of entropy. Dr. Lavelle is usually pretty good about staying on time with the material and we have until next Wednesday.

KatelinTanjuaquio 1L

As others have stated, this equation applies to all phases but the change in liquids and solids are so small that the value is essentially 0.

KatelinTanjuaquio 1L

To start this problem, you would need to convert the pH into molarity by using 10^-4.60. Then, set up an ICE table with the molarity found as the H3O+ equilibrium concentration. Set the initial condition of HClO to x then subtract the molarity found from that, which will be the final equilibrium of ...

KatelinTanjuaquio 1L

I am working on Module #1 and came across this problem: For the unbalanced reaction, CO (g) + H2 (g) ⇌ CH3OH (g), the equilibrium concentrations are [CO] = 0.0911 M, [H2 ] = 0.0822 M, [CH3OH] = 0.00892 M. What is the value of the equilibrium constant? Does the equilibrium favor reactants or products...

KatelinTanjuaquio 1L

What is pKa exactly? This is a problem I was working on:

When the pH of 0.10 m HClO2(aq) was measured,
it was found to be 1.2. What are the values of Ka and pKa of chlorous acid?

Why is it that sometimes pKa is equal to pH and other times it is not?

KatelinTanjuaquio 1L

Yes, you need to make three posts (questions, posts, and replies all count!) a week to get your three posts. However, I think if you have 30 posts at the end of the quarter, it should be fine. It all depends on your TA and how they count the posts. To stay safe, I would just make the three posts a w...

KatelinTanjuaquio 1L

Both K and Q use the formula [Products]/[Reactants]. However, K is used only when the reaction is at equilibrium. This means that the concentrations of the products and reactants must be at equilibrium (but not necessarily equal to each other!). Q on the other hand can be found at any time of the re...

KatelinTanjuaquio 1L

I got the same answer as you, 6.83 and I am unsure why the book says 6.80.I think it is a calculation error. In the solutions manual, it states that square root of 2.1x10^-14 is 1.4x10^-7, when I calculated 1.45x10^7. Just to test their answer, I plugged in their value, 1.4x10^-7, to the pH formula....

KatelinTanjuaquio 1L

Q is calculated at any time during the reaction while K is only calculated at equilibrium. This means that Q and K would be equal if the point at which Q was measured was at equilibrium. Q is not limited to the concentration or partial pressures values at equilibrium, while K is.

KatelinTanjuaquio 1L

Solids and liquids are not used in equilibrium constants. Kc is used for concentrations while Kp is used for partial pressures. However, these can be converted between each other using the ideal gas law, PV=nRT.

KatelinTanjuaquio 1L

A net ionic equation is used to determine what has changed in a reaction. If the net ionic equation was not used, spectator ions would be there and have no effect on the reaction; ions would just be "floating around." In essence, you should always strive to use the net ionic equation when ...

KatelinTanjuaquio 1L

A compound can be amphoteric when it can be an acid or a base. An example of this would be water.

KatelinTanjuaquio 1L

Will someone please explain question 40 part B and C For part B: We would expect ozone to have two bond lengths are the same. This is because it is a resonance structure. In resonance structures, the bond lengths are the same--the average of its bond lengths. For part C: O2 would have the strongest...

KatelinTanjuaquio 1L

On question 38, how come the LDF’s are the determining factor instead of dipole-dipole in determining the boiling point? H2Se has stronger London dispersion forces, while H2S has stronger dipole-dipole forces. However, because we are given that H2Se has a higher boiling point, all we know that is t...

KatelinTanjuaquio 1L

The properties that make an acid strong are weak are the following: 1. Weaker (longer) A-H bond makes it easier to remove H+. 2. Oxoacids more readily lose H+ if resulting anion is stabilized by electron withdrawing atoms which delocalize and stabilized the negative charge.(Delocalized charge makes ...

KatelinTanjuaquio 1L

The formula on the inside of the brackets refers to atoms that are within the coordination sphere and connected to the central atom. Those outside are not.

KatelinTanjuaquio 1L

Polarizability is the characteristic of atoms and ions with electron clouds that readily undergo a large distortion. An anion is highly polarizable if it is large because the nucleus exerts weak control over outermost electrons as they are farther. This makes electron clouds easily distorted.

KatelinTanjuaquio 1L

When referring to hybridization notation, it does not matter whether it is written 2sp2 or sp2. You would only use 2sp2 when writing the composition of each bond.

KatelinTanjuaquio 1L

When we are considering bond angles, we do not take into account bond length. We consider bond length when determining dissociation energy.

KatelinTanjuaquio 1L

In the sixth edition, chapter six, question five part c asks, "Suggest, giving reasons, which substance in each of the following pairs is likely to have the higher normal melting point: CHI3 or CHF3." The answer is CHI3 because it has stronger london dispersion forces. Why is it that it is...

KatelinTanjuaquio 1L

Formal charge is an atom's number of valence electrons minus number of dots and lines, which can more easily be seen in the following equation: an atom's number of valence electron - (number of lone pairs + (number of shared electrons/number of bonds). It is used when drawing Lewis Structures to ens...

KatelinTanjuaquio 1L

Yes, all types of molecules have London Dispersion forces.

KatelinTanjuaquio 1L

Why is CH2Cl2 polar? When I drew the Lewis structure, I put Cl opposite from each other and I thought that the dipole moments would cancel out, but it is normally drawn with the Cls next to each other. Is there something other than the drawing that makes it polar? How do I know to put them next to e...

KatelinTanjuaquio 1L

I was doing a problem in which it asks to write the bond angles for C2H4. How do we know which atoms to look at? I understand how we look at H-C-H but how do we know to do H-C-C instead of, say C-C?

KatelinTanjuaquio 1L

Why is it that molecules with an AX2E3 VSEPR name have bond angles of 180 rather than less than 180? I thought that the three lone pairs would cause it to be slightly less than 180.

KatelinTanjuaquio 1L

For a molecule with 4 regions of electron density, you would write the hybridization as sp3. After that, it would be 5=sp3d, 6=sp3d2, etc. Each region can be counted off using one letter.

KatelinTanjuaquio 1L

When drawing Lewis structures, should we be taking the molecular shapes into consideration?

KatelinTanjuaquio 1L

Hello!

How would one write the VSEPR formula for (CH3)2Be? I have drawn the Lewis structure but I just wanted to check. Would it be broken down for each of the central atoms, or do we consider Beryllium to be the only central atom? Thank you.

KatelinTanjuaquio 1L

What is polarizability and what is its significance to interactions between ions and molecules?

KatelinTanjuaquio 1L

A covalent bond is a bond between two atoms in which they share an electron. A coordinate covalent bond is a bond in which an atom provides both electrons.

KatelinTanjuaquio 1L

We should be given the electronegativities as we are usually not asked to memorize values.

KatelinTanjuaquio 1L

So long as you understand the general trends of ionization energy, I think you should be fine. Though it is not necessary to know the measurements, I believe you can find them in the Appendix.

KatelinTanjuaquio 1L

Hello, Question 2.47 of the sixth edition asks, "For each of the following ground-state atoms, predict the type of orbital (1s, 2p, 3d, 4f, etc.) from which an electron will be removed to form the +1 ion." Part B asks about Manganese and part D asks about Gold. I was wondering, why it is r...

KatelinTanjuaquio 1L

Yes, as stated above, while a everything, including a car, has wavelength properties, a car's wavelengths are too small to be detected. The threshold for being detected, as Dr. Lavelle said in class, is about 10^-18 m.

KatelinTanjuaquio 1L

Use kg as that is the SI unit. Fun fact: the reason kg the SI unit and not g is simply because a king wanted it that way! Here's the link if you'd like to learn more: https://physics.stackexchange.com/quest ... ic-si-unit

KatelinTanjuaquio 1L

Hello! On the formula/constant sheet, speed of light is given as 2.99792*10^8, so I would use that. I don't think it makes that much of a difference but it ensures your answer is precise as possible before rounding off using sig figs.

KatelinTanjuaquio 1L

I wouldn't think so just because most of our tests are usually on application of content rather than memorization.

KatelinTanjuaquio 1L

As with all problems, it is best to use the number of figures given on the formula sheet. Then round off your sig figs as given in the question to ensure the most accurate answer.

KatelinTanjuaquio 1L

I was told by my TA that you just have to make three posts. I asked when the end of the week is considered and he told me to have the posts done before Friday's lecture.

KatelinTanjuaquio 1L

I think it is best to use the number of sig figs found in the question. However, when performing the calculations, you should be as exact as possible and use however many figures given on the periodic table. Then, put your answer in sig figs that match the answer.

KatelinTanjuaquio 1L

I'm not sure if points will be taken down but, personally, it helps me make sure that I am not using incorrect units in a given area. Also, I do believe we get partial credit in places and I think that having units all the way through would ensure you get all the points you deserve.

KatelinTanjuaquio 1L

Yes, as stated above, the midterm is November 5th, while the following test happens the week after Thanksgiving.

KatelinTanjuaquio 1L

Hi!

I was wondering the same thing. The question said it reacted with oxygen in the air and, as oxygen is a diatomic molecule, I assumed we would be using O2 rather than O. I also got the answer of 1:1 ratio. How do we know when to use O2 and when to use O in stoichometry questions?

KatelinTanjuaquio 1L

Yes, I believe you would have to use scientific notation, so in this case, 100 with two sig figs would be 1.0 x 10^2. I believe this is the only way because three sig figs would be 100. (note the period after) or 1.00 x 10^2.

KatelinTanjuaquio 1L

Though we sometimes need them for review problems, I believe he will be giving us the formulas as he told us we would not need to memorize any names. Later on, however, he said we would learn it as we use them more frequently.

KatelinTanjuaquio 1L

Extensive properties are based on the amount whereas intensive properties do not change with the amount. For example, volume is an extensive property, whereas density is an intensive property. The amount of water does not change the density of water, but the amount of water does change its volume.

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