CHEMISTRY COMMUNITY

Lauren Ho 2E

For part B. I got that the order of increasing oxidation power was Mg²⁺ < Ti²⁺ < Sn²⁺ because a more positive voltage means a stronger oxidizing agent. I don't know how to solve A and C, though :(

Lauren Ho 2E

Yes, because an inert electrode is needed whenever there is no conducting metal.

Lauren Ho 2E

Thank you!

Lauren Ho 2E

The answer is (D), and you can find it by process of elimination. (A) we know to be incorrect, and (B) is false because surface area is proportional to chemical reaction speed. (C) is incorrect because reactions between gases are not rapid in ALL cases (e.g. very very low temperature). (E) is incorr...

Lauren Ho 2E

The overall order is 2+1 = 3.
The order with respect to A is 2, and the order with respect to B is 1.

This makes (C) the answer

Lauren Ho 2E

My favorite way to study is by using The Organic Chemistry Tutor on Youtube! His videos with practice problems somehow always follow Dr. Lavelle's outlines perfectly, and Youtube is perfect for studying in the sense that explanations are clear if you are using a good channel to study and for the pau...

Lauren Ho 2E

Here is a visual that I hope helps:

Lauren Ho 2E

They are the same, but referred to with two different named because they are named after Luigi Galvani and Alessandro Volta.

Lauren Ho 2E

Completing 15.9 in the sixth edition should be very helpful in understanding this concept!

Lauren Ho 2E

The solution manual states that "a negatively charged electrolyte flows from the cathode to the anode."

Lauren Ho 2E

You can determine the cathode reaction and anode reaction by seeing which combination would cause you to end up with a greater voltage when the two reactions are combined

Lauren Ho 2E

Melody P 2B wrote:Would you add Pt(s) to both sides?

You would add Pt(s) to whichever side lacks solid metal.

Lauren Ho 2E

Standard corresponds with 1 mole/L, 1 atm, and 25 degrees C

Lauren Ho 2E

The Solution Manual Errors PDF on Professor Lavelle's website doesn't point to any errors in the solution manual for problem 14.5, so I would assume that the given answer is right

Lauren Ho 2E

From https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Electrochemistry/Redox_Chemistry/Balancing_Redox_reactions:

Lauren Ho 2E

HAHA thanks, I wish the 1 pm class got serenaded :(

Lauren Ho 2E

More specifically, we discussed the three different ways to find free energy:

1. Using standard enthalpy of formation and standard molar entropy
2. Hess-style approach of adding/subtracting delta G (rxn 1) and delta G (rxn 2)
3. Using G(products) - G(reactants)

Lauren Ho 2E

Interesting stuff for those interested in art history :)

https://phys.org/news/2019-02-art-acne-georgia-okeeffe.html

Lauren Ho 2E

If energy leaves a system, the system does work on its surroundings. If energy enters a system, work is done on the system.

Lauren Ho 2E

Dr. Lavelle also usually does midterm review during class in the days leading up to the midterm!

Lauren Ho 2E

From http://www.dynamicscience.com.au/tester/solutions1/chemistry/energy/calorimeter.htm : "Calibration of the calorimeter is the determination of how many joules of energy are required to raise the temperature of the contents by one degree Celsius. This is known as the calibration factor of th...

Lauren Ho 2E

You would look at the total of all of the bonds: the three C=C bonds and three C-C bonds, for instance.

Lauren Ho 2E

Closed systems cannot exchange matter with their surroundings, but can exchange energy.

If a sealed beaker is heated, for instance, nothing physically can leave or enter the beaker. However, there will be a heat energy transfer.

Lauren Ho 2E

Here is a visual I hope will help!

Lauren Ho 2E

If energy leaves a system, the system does work on its surroundings. If energy enters a system, work is done on the system.

Lauren Ho 2E

Do the modules tell you your score at the end? Or are they just for practice?

Lauren Ho 2E

Does anyone know of any tips or tricks that will allow you immediately to identify an acid or base as weak or strong?

Lauren Ho 2E

Do we need to write anything to indicate or explain why we have ignored x? Or can we just do it without indication if our problem passes the 5% test?

Lauren Ho 2E

here is a visual representation:

Lauren Ho 2E

This is not necessarily true. For instance, a weak acid/base will have a stronger conjugate base/acid.

Lauren Ho 2E

Yes! Here is a visual representation of that:

Lauren Ho 2E

You would use equilibrium concentrations

Lauren Ho 2E

You can compare the equilibrium constants for the dissociation of CL 2 versus the dissociation of F 2 to determine stability. Because the dissociation of F 2 has a larger equilibrium constant than that of CL 2 and a large equilibrium constant means that the equilibrium concentration of the products ...

Lauren Ho 2E

Yes, I believe it does!

Lauren Ho 2E

Claire Guo 1B wrote:TA's wont be checking if we did three posts every week right? Because I think I have the 30 posts we need but some weeks I forgot and then caught up later.

I think that should be fine!

Lauren Ho 2E

This part is a little confusing for me. If, basic solutions have less H3O+ than acids, and the pH log measures the amount of H3O+, then why do the larger numbers (8-14) correspond to bases? pH = -log 10 With this knowledge, the pH of a number like 10 -1 (pH = 1) would be lower than the pH of a numb...

Lauren Ho 2E

a) says [Fe(CN)6]^4- however the answer is tetracholoroferrate (II) why is iron called ferrate and why is the charge (II) and not (IV) Each CN contributes to a -1 charge, meaning (CN) 6 has a total charge of -6. If [Fe(CN)6]^4- has a net charge of -4 and (CN)6 contributes to -6 of that charge, Fe m...

Lauren Ho 2E

Will our TAs give us points for chem community just by looking up our names and seeing how many posts we have?

Lauren Ho 2E

From https://courses.lumenlearning.com/introchem/chapter/naming-acids-and-bases/ - Acids are named based on their anion — the ion attached to the hydrogen. In simple binary acids, one ion is attached to hydrogen. Names for such acids consist of the prefix “hydro-“, the first syllable of the anion, a...

Lauren Ho 2E

IF₇ is an example of a molecule with this shape!

Lauren Ho 2E

Here's a visual that I hope helps!

Lauren Ho 2E

Adrian C 1D wrote:If a molecule's molecular geometry is linear, is it a good indicator of the molecule being nonpolar?

Not necessarily, e.g. HCN is linear, but polar

Lauren Ho 2E

Andrew Sun 1I wrote:if a question asks what is the hybridization around the central atom, does it need a coefficient to specify which energy level?

My TA said that we don't need to specify which energy level

Lauren Ho 2E

Thank you so much!!

Lauren Ho 2E

I think I remember my TA saying that the numbers denoting row are unnecessary (though correct) when writing hybridizations. So in your case, writing them either way would probably be alright!

Lauren Ho 2E

I3- ions have three lone pairs around the central I atom, meaning the molecule as a whole has an electron geometry of trigonal bipyramidal and a linear molecular geometry.

Lauren Ho 2E

As far as our class is concerned, bond lengths affect bond angles to such a small extent that this effect can be ignored.

Lauren Ho 2E

cara_cavarretta_3F wrote:Even though we still have discussion for Mon-Wed is our homework still due the next week as well? Sorry, just to be sure.

For my discussion, we could either turn in 7 homework problems this week or both sets (14 problems) the following week

Lauren Ho 2E

I think bond angles are the same for molecules of the same shape (at least the ones we've learned about so far)

Lauren Ho 2E

Is this helpful in visualizing the molecular geometry?

Lauren Ho 2E

SCl4 has a seesaw molecular geometry because you must take into account the effect that the lone pair on S has on shape; if there was no lone pair on SCl4, the shape would be tetrahedral. If there was no lone pair it would just be SCl4. Would it not be square planar? To be square planar, a molecule...

Lauren Ho 2E

SCl4 has a seesaw molecular geometry because you must take into account the effect that the lone pair on S has on shape; if there was no lone pair on SCl4, the shape would be tetrahedral.

Lauren Ho 2E

From http://wwwchem.uwimona.edu.jm/courses/CHEM1902/IC10K_MG_Fajans.html : "The ability of a cation to distort an anion is known as its polarization power and the tendency of the anion to become polarized by the cation is known as its polarizability."

Lauren Ho 2E

Combustion reactions always have oxygen and a hydrocarbon as reactants and will always produce CO2 and H2O.

Lauren Ho 2E

If an element is more electronegative than another atom, it will attract electrons more strongly.

Lauren Ho 2E

I usually study by looking up "[topic] practice problems" on youtube and following along. The Organic Chemistry Tutor's videos have been really helpful for me!

Lauren Ho 2E

Javier_Ochoa_DIS_3J wrote:This is the equation to find the formal charge.

Valance electrons - (lone pair electrons + number of bonds) = Formal charge.

I like using this equation more than the FC = V - (L + S/2) one because there is less room for error!

Lauren Ho 2E

To convert from meters to picometers, you multiply the length value by 1e+12

Lauren Ho 2E

This diagram is super helpful for me!

Lauren Ho 2E

Orbitals that have the same energy levels are called degenerate (same n and l quantum numbers)

Lauren Ho 2E

I'm not really sure myself, but here is a link that might help:

https://www.quora.com/How-do-molecular-and-atomic-spectroscopy-differ

Lauren Ho 2E

I think our grades will be based off of the class average out of 500 points

Lauren Ho 2E

For example, Potassium can be written as 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 or [Ar] 4s^1; it is part of the S block

Lauren Ho 2E

Yes, each metal has a unique threshold energy

Lauren Ho 2E

I worked without stopping the entire way through and was probably able to finish with 5 minutes left to check my work.

Lauren Ho 2E

The first step is knowing that this transition is in the Lyman series, but I'm also not sure where to go after this.

Lauren Ho 2E

Hannah Padilla 1H wrote:For the first test, will we need to be able to identify molecular formulas from their written name? For example in problem F3.) “Write the formula for nitric acid”

Molecular formulas will be given!

Lauren Ho 2E

200.0 offers more precision than 200., so it follows that 200.0 has one more significant figure than 200.

Lauren Ho 2E

I agree that the answer should be C; light with a frequency higher than the threshold energy should be able to remove electrons

Lauren Ho 2E

Thank you for this advice; I switched into this class and was having doubts about which chemistry series would be best for me to take part in, and this makes me feel much more confident!

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