CHEMISTRY COMMUNITY

Carissa Young 1K

How do you solve #8 on worksheet 9? How do you find the half-life given that 99% of the reactant decomposes in 137 min?

Carissa Young 1K

use comma when the the reactants are in the same state/phase and the line when they are not. so if you had Mn4+ (aq) and Mn2+ (aq) it would be a comma separating the two. If Mn2+ was a gas then use the line.

Carissa Young 1K

What is the difference between the rate and rate constants?

Carissa Young 1K

In a concentration cell, why does reduction take place on the electrode with a higher concentration? (w/same components)

Carissa Young 1K

What doesn't get put in the cell diagram? Is it just solids and H2O liquid? Does H+ get put in the cell diagram?

Carissa Young 1K

What happens if Gibbs free energy is zero exactly?

Carissa Young 1K

If you look on his website, it's under the header "Audio-Visual Focus-Topics, Assessments & Surveys". There's four of them to complete.

Carissa Young 1K

whichever half-rxn is oxidized (loses e-, oxidation number incr) is the anode and the half-rxn that is reduced (gain e-, oxidation number decr) is the cathode

Carissa Young 1K

For that problem I used deltaG= deltaGo + RTlnQ which further is deltaG=-RTlnK + RTlnQ. I don't know really what the applications of the Van't Hoff equation.

Carissa Young 1K

What does it mean if Gibbs free energy is 0 exactly?

Carissa Young 1K

Since the reaction is not at equilibrium, you need to use deltaG=deltaGo + RTlnQ which can be further written as deltaG=-RTlnK + RTlnQ

Carissa Young 1K

The units are either kJ or J due to the fact that delta G is deltaH- T*deltaS

Carissa Young 1K

Gibbs free energy can be used to determine the "spontaneity" of a reaction due to the fact Gibbs free energy change is the total energy change of the system.

Carissa Young 1K

It covers in chapter 14, everything up to but not including Nernst Equation which is section 14.9 in the 6th edition textbook.

Carissa Young 1K

I thought that the salt bridges have porous disks which allow only for the transfer of ions between solutions and keeps the solution inside the bridge completely separate. Correct me if I'm wrong.

Carissa Young 1K

I used C=5/2R and I got full credit, maybe it doesn't matter that much?

Carissa Young 1K

It covers Gibb Free Energy and Thermochemistry up until today's lecture.

Carissa Young 1K

Bomb calorimeters are insulated and essential makes the system isolated which is a reason that volume is fixed because if it weren't then an external force like a piston could compress the volume, but in an isolated system, nothing exchanges with the surroundings. using the equation q=-C(cal) x delt...

Carissa Young 1K

We get an equations sheet, so probably not? All the related and derived equations we need should be given to us.

Carissa Young 1K

The question asks to estimate the enthalpy of formation of compounds in the liquid state. After finding the deltaH of the gas, what equation are we supposed to use to find the deltaH of the liquid? In class we learned that the enthlapy of vaporization is the H(vapor)-H(liquid) to go from liquid to a...

Carissa Young 1K

We have a note taker for this class on studysoup.com, I think her name is Celine Hoh. She uploads the notes there if you need them.

Carissa Young 1K

Thanks for explaining this! I was also kind of confused about deltaH.

Carissa Young 1K

What does the R in this equation stand for?

Carissa Young 1K

No, they are not counted towards your grade at all. The modules are just for you to refer to if you need extra help or want to review basics. In my opinion, its good to do them, especially the quizzes for extra practice.

Carissa Young 1K

As stated before, don't use solid or pure liquid concentrations in the equilibrium constant equation. For water, you would only put it in the equation if it is in the gas phase.

Carissa Young 1K

In addition, the definition of state property is that its a value determined by its current state and is not dependent on the path taken to obtain that state. State property can be added and subtracted. Other state properties are energy, pressure, volume, temperature, density, and heat capacity.

Carissa Young 1K

In my solutions manual it says that Q<K. When you solve for Q, you should get 6.9 which is smaller than K of 1.7 x 10^6. Therefore, bc Q<K, the rxn will form more constants (favor forward rxn).

Carissa Young 1K

For part (C), can someone explain why Cl2 is thermodynamically more stable? Does the equilibrium constant have anything to do with determining wheter Cl2 rxn or F2 rxn is more stable?

Carissa Young 1K

To convert, use p=(conc)RT --> Conc=P/(RT). In Module 2, the PCl problem in the video, Lavelle talks about conversion there if you need more assistance.

Carissa Young 1K

Celine Hoh 4H wrote:Can we submit our hw during discussion?

I think for this week's homework only, everybody turns it in after lecture. But, for every other hw assignment, it will be due in discussion.

Carissa Young 1K

If you know what the equilibrium constant of the reaction is, you can use it (plus some extra given info), to figure out the individual equilibrium concentrations of products and reactants. Hope that answers your question!

Carissa Young 1K

will there be more worksheets for the recently covered material like acids and bases and coordination compounds ? Thanks

Carissa Young 1K

I would just remember both. What is the chemical formula for EN and EDTA?

Carissa Young 1K

what were the other names we had to remember besides bis when the other prefixes are already used in the name?

Carissa Young 1K

Hanniel U 1A wrote:Does that mean atoms after row three can? Does this relate to the atomic number?

Atoms after and in row three can have an expanded octet because of their d orbitals.

Carissa Young 1K

The hybridizations of sp of 2 of the 6 C atoms want to be in a linear arrangement with 180 degree angles but can't because of the constrainment of being in a 6-membered ring whose angles are close to 120 degrees. This makes benzyne highly reactive with these hybridzations.

Carissa Young 1K

Delocalization means that the electron pair is distributed over several pairs of atoms and can't be identified with just one pair of atoms.

Carissa Young 1K

Why does the bond angle between two hybrid orbital increase
as the s-character of the hybrids is increased?

Carissa Young 1K

Hybridization is the concept of mixing atomic orbitals into new hybrid orbitals (with different energies, shapes, etc., than the component atomic orbitals) suitable for the pairing of electrons to form chemical bonds in valence bond theory. Like Lavelle said in class, its easier to start by figuring...

Carissa Young 1K

First, realize that nitrate's lewis structure has resonance and is the reason why the bond lengths are averaged. This blend of single and double bond lengths accounts for this averaged length.

Carissa Young 1K

Ionization energy is energy required to remove an electron off an isolated atom or molecule. Threshold energy is basically same thing but its the minimum energy required to remove an electron and is the work function (in photoelectric effect).

Carissa Young 1K

In one of his posts, he said "Test 3 covers: End of bonding from 3.12 (6 Ed.) and from 2D (7 Ed.); and all of Molecular Shape and Structure (see syllabus and outlines for details). Hope that helps!

Carissa Young 1K

They are synonymous, our TA said if you write either one it will be counted correct although they are using the term angular for the most part.

Carissa Young 1K

Can someone explain why electron diffraction by a crystal supports de Broglie's hypothesis of the wave nature of matter? Thanks!

Carissa Young 1K

Actually, I have a question for you. What are coordination compounds and what is one example do you know of? This is the first I've ever heard of that term so I'm curious.

Carissa Young 1K

Luc Galaif wrote:What exactly does the term "dipole" mean?

A dipole is a separation of electrical charges and these molecular dipoles occur due to the unequal sharing of electrons between atoms in a molecule.

Carissa Young 1K

This equation uses the wave function to describe valence electrons in an atom and uses the concept that valence electrons with wavelike properties and indeterminacy in momentum and position, can be described by wave function.

Carissa Young 1K

Once you total the number of valence electrons and distribute them, you will find a Lewis structure with triple-single-single-triple bonds between the N, another Lewis structure with double-double-single-triple bond, and a triple-single-double-double bond. There are 4 lone pairs as well on each of t...

Carissa Young 1K

Make sure that the atoms are also balanced on opposing sides of the central atom and as said above, calculate the total number of valence electrons and don't forget to follow octet rule.

Carissa Young 1K

part (C): For the Lewis structure of glycine, H2C(NH2)COOH, does it matter where (the position) the Hydrogens attached to the N are?

Carissa Young 1K

I think you can write both out because they are the same configurations.

Carissa Young 1K

Thank you! I've been looking for people to study with!

Carissa Young 1K

I don't know how this formula is derived but I think R and r stand for the radii of each of the particles.

Carissa Young 1K

I hope they are updated too, but khan academy and other sites have great videos to look at as well.

Carissa Young 1K

I think it will cover all those topics up to how far we get in lecture. I would just start reviewing everything we've covered so far.

Carissa Young 1K

Vanessa Reyes_4C wrote:For problem 1.69b do you have to convert electron volts to joules, and then use the E=hc/frequency equation?

Yes, you have to make sure all your SI units are correct before doing the problem.
1eV=1.602 x 10^-19 J

Carissa Young 1K

The extent of change refers to the slope of the wave; so think about what happens to the amplitude of the waves if frequency(the number of cycles/Hertz per sec) decreases. Does the extent of change (slope of the wave) increase or decrease?

Carissa Young 1K

In lecture, someone asked the same question and Professor Lavelle said it can happen where two photons combine to eject an electron but it's SUPER rare for this to happen which is why we use 1 photon to eject 1 electron as it happens most commonly.

I hope this helps.

Carissa Young 1K

It is advisable to know the general idea and the main categories such as UV, visible, and infrared.

Carissa Young 1K

Do all our final answers need to be converted to the base SI unit (ex:meter, kilogram, mole) or do we just use the closest prefix to it? And if we leave our answer in the base SI unit and do not use a prefix simplifying the value would our answer be wrong even if both answers would be mathematicall...

Carissa Young 1K

Of course!
Today's topics included the quantum mechanics description of light, the photoelectric effect, and the experiments leading to the discovery of the photoelectric effect.

Carissa Young 1K

Where are the posted answers for this worksheet?
Thanks

Carissa Young 1K

Here is some we have to know: Mass (kg) Length(m) Time(s)
Giga - 10^9
mega- 10^6
kilo - 10^3
deci- 10^-1
centi- 10^-2
milli- 10^-3
micro- 10^-6
nano- 10^-9
pico-10^-12

We went over these in lecture; hope that this list is helpful

Carissa Young 1K

use molar mass to find out the moles of the Epsom salts 5.15 g H14MgO11S / 246.466 g*mol^-1 = .02089 mol H14MgO11S use the ratio of 11 mols oxygen to 1 mol of Epsom salts and then multiply by Avogadro's number to find how many atoms of oxygen .02089 mol H14MgO11S * (11 mol O / 1 mol H14MgO11S) *(6.0...

Carissa Young 1K

Another thing to note is hydrate refers to water, so it's formula is simply H20. It helps to break down the name into parts and figure out what they mean individually and then put it all together at the end.

Ex. hepta/ hydrate
Hepta means 7
Hydrate refers to water

Therefore heptahydrate is 7H20

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