CHEMISTRY COMMUNITY

Kaili Valenzuela 2B

I believe it is usually in seconds, but always double check if the questions asks for a specific unit!

Kaili Valenzuela 2B

I definitely agree with everyone else, organic chemistry tutor is extremely helpful!

Kaili Valenzuela 2B

A zero order reaction will not depend on on the concentration of the reactants. Its graph would show [A] vs t and would be a decreasing linear line.

Kaili Valenzuela 2B

K can only change by a change in temperature

Kaili Valenzuela 2B

Hi! So the rate law would just include the reactants of the slowest step so it would be rate=k[HClO][-I]. However, we can see that HClO is the intermediate value because it appears as a products in step 1 and a reactant in step 2, but it does not appear in the overall reaction. Since HClO is an inte...

Kaili Valenzuela 2B

The review session is on Saturday and the final exam is on Sunday at 9:30 and is 90 minutes long.

Kaili Valenzuela 2B

I definitely recommend the review sessions they are super helpful in refreshing your memory on topics you struggle with! I’m also planning on redoing the textbook problems!

Kaili Valenzuela 2B

Yes! The times that are bolded are the review sessions and the non bolded are just the TA’s office hours

Kaili Valenzuela 2B

I'm part of Kids Korner club right now, but I'm definitely looking forward to joining more organizations!

Kaili Valenzuela 2B

No you would not include the coefficients you would just include the phases

Kaili Valenzuela 2B

To add onto the above post, shorthand notation does not include any coefficients.

Kaili Valenzuela 2B

For acidic conditions you add H+ ions along with H2O and for basic solutions you add OH- and H2O

Kaili Valenzuela 2B

Its due this Sunday 2/28 at midnight!

Kaili Valenzuela 2B

As said above, one coulomb is the amount of electrical charge in 6.24x10^18 electrons. Also to add on, 1 joule of work per coulomb of charge transferred is equal to 1 volt: 1V=1J/C

Kaili Valenzuela 2B

The final is cumulative, but there should be plenty of review sessions to help with our studying!

Kaili Valenzuela 2B

ΔH = q when under constant pressure, or in other words in isobaric conditions

Kaili Valenzuela 2B

Justin Lin 1B wrote:I think it's helpful to take a few deep breaths before the exam. It helps me concentrate and gets rid of the butterflies in my stomach.

I definitely agree! Taking a moment to focus on my breathing before an exam has really helped me reduce my stress and clear my mind!

Kaili Valenzuela 2B

I believe the final will be proctored the same as the two midterms

Kaili Valenzuela 2B

The reaction is considered thermodynamically favorable when ΔG is negative

Kaili Valenzuela 2B

Does anyone know if chem 14bl usually accepts a good number of people from the waitlist?

Kaili Valenzuela 2B

Definitely pay close attention to the context of the question. We usually use Kelvin, but there are times when Celsius is the correct unit to use.

Kaili Valenzuela 2B

I feel the same as others, I found the final to be distinctly harder than the midterm mostly because it covered material from the entire quarter. But the many review session available are very helpful when reviewing!

Kaili Valenzuela 2B

I say stick to Kelvin since most of the constants we use are in Kelvin!

Kaili Valenzuela 2B

I also feel really uneasy about this midterm mostly because thermo is not the easiest topic for me, but I plan on utilizing all my resources to prepare well!

Kaili Valenzuela 2B

I'm currently obsessed with Criminal Minds!

Kaili Valenzuela 2B

When work is a negative value it means there is work being done on the surroundings and the larger the negative value the more work is being done

Kaili Valenzuela 2B

Yes Kp is calculated the same Kc is!

Kaili Valenzuela 2B

This was actually really good to hear. Thank you for sharing this! It made me feel a lot better!

Kaili Valenzuela 2B

ΔU is the change in internal energy of system. It is dependent upon a change in heat or work, thus giving us the equation ΔU= q+ w

Kaili Valenzuela 2B

External pressure is the pressure acting on the system. So in this case it would be the pressure pushing down on the piston.

Kaili Valenzuela 2B

Maddie Turk Disc 2J wrote:Hi! So going off of this standard form thing, when a molecule is in its standard form its enthalpy is 0 right? or is that just for specific molecules?

Hey! Yes, when an element is in its standard state the standard enthalpy will be 0!

Kaili Valenzuela 2B

No this information will probably be included the problem or we will be provided a table with the values.

Kaili Valenzuela 2B

The grades take usually about a week to come out especially because they have to go through the problems since there is an opportunity for us to get partial credit. But there is usually an email sent out when they are released!

Kaili Valenzuela 2B

I try to go to at least 3 or 4 UA sessions per week, and then sapling and textbook homework... So 10 -12 hours I would say? I also have other classes and I'm working so i understand the struggle. Going to UA sessions as study time, is very efficient and helpful cause they reinforce stuff we are sup...

Kaili Valenzuela 2B

Hello! I'm having trouble with this problem. I do not understand how to find the chemical equation if someone could please explain! Thanks!

Kaili Valenzuela 2B

A is simply the place holder for the acid and for a weak base that has not been specified it would be B + H20 yields OH- + HB+.

Kaili Valenzuela 2B

It is best to memorize the strong acids and bases and everything that is not considered a strong acid or base would be identified as a weak acid/base. Here's a list of the strong acids and bases sapling provides: Hope this helps! https://sites.google.com/site/chempendix/strong-acids-bases Hope this ...

Kaili Valenzuela 2B

Hi! Always remember that the “p” simply means the -log of what follows. So the pKa is the -log[Ka]. If you were trying to find the Ka from the pKa it would be like this Ka=10^-pKa

Kaili Valenzuela 2B

Hey! When Ka or Kb is less than 10^ -4 then the values are considered to be very small and we can approximate that x will equal to 0.

Kaili Valenzuela 2B

Doing the textbook problems are defiantly a must and definitely make sure you understand all the bulleted concepts on the outlines! If looking for youtube videos to watch for help the organic chemistry tutor is a great help!

Kaili Valenzuela 2B

We do not include any substance that is in a liquid or solid state. We only include gases and aqueous states, so in this case we would include H20 only if it was a gas.

Kaili Valenzuela 2B

Autoprotolysis is the proton transfer between two identical molecules. The reaction looks like this:
2H2O (l) —-> H30+(aq) + OH-(aq)

Kaili Valenzuela 2B

The acids and bases content from 14A basically is a foundation for what we are learning in 14B right now so it would just strengthen your knowledge if you knew the basics of acids and bases from 14A.

Kaili Valenzuela 2B

Hi! If the Ka value is large you have to remember that the pKa value is 10 raised to the power of the Ka value because p= -log. So, the larger the Ka value the stronger the acid and the lower its pKa value will be. The same goes for Kb and pKb values.

Kaili Valenzuela 2B

It's definitely helpful to begin studying a week or so before exams rather than trying to cram everything in two days before. You are more likely to remember what you studied opposed to what you study during a cramming session. I also found making a study guide is extremely helpful!

Kaili Valenzuela 2B

After completing the ICE table you basically just need to use algebra to for the rest of the problem. You take your values from the last row of the ICE table and plug them into the equation for K which is products/reactants and then proceed by using the quadratic formula to find the value of x. Then...

Kaili Valenzuela 2B

Hi guys can someone please help guide me through this problem because I cannot seem to get the correct answer, thanks! At a certain temperature, the given reaction has an equilibrium constant of Kp=425. PCl3(g)+Cl2(g)↽−−⇀PCl5(g) PCl5 is placed in a sealed container at an initial pressure of 0.0290 b...

Kaili Valenzuela 2B

What was Avogadro’s favorite sport? Golf, because he always got a mole-in-one!

Kaili Valenzuela 2B

Hey, I am trying to create a new post because I had a question about the Sapling HW. However, I do not see an option to create a new post for me. I can only reply to other posts. Could someone please tell me how to create a new topic? It would be nice if someone could upload a screenshot of their p...

Kaili Valenzuela 2B

So is R the same constant as the one we used before on the equation sheet? No the R constant on the equation sheet we have is in hertz which is not useful to us when using this equation so the R constant in this case could be 0.08205746 L⋅atm/mol⋅K but could be different depending what units you use.

Kaili Valenzuela 2B

Hi! I think this would be helpful to know
pH=14.00-pOH= -log[H+]
pOH=14.00-pH= -log[OH-]

Kaili Valenzuela 2B

By looking at the lewis structure you can see that NH3 has four regions of electron density. Each bond counts as one region so thus we have three regions plus one one pair on the nitrogen that also counts as a lone pair. Since we have four regions of electron density we know that is has a hybridizat...

Kaili Valenzuela 2B

Such as Fe is derived from greek to make Ferrate here are some other examples that might be useful to memorize! :)
Cu= Cuprate, Pb=Plumbate, Au= Aurate, Sn=Stannate, Ag=Argentate

Kaili Valenzuela 2B

Hi! So in order to find the pH we first must convert the give [OH-] to [H+]. In order to do this we must divide the value 1.0x10^-14 moles by the [OH-] which in this case is 3.50x10^-3. Then we take the result, which in this case is 2.86x10^-12, and take the -log of it. After doing this we get a pH ...

Kaili Valenzuela 2B

Claire_Kim_2F wrote:Is ha the base and a- the acid component of the equation?

Actually, HA is the acid and A- is the base

Kaili Valenzuela 2B

Hi! Metals are mostly located in groups 1-13 and nonmetals are mostly starting from group 14 to 18. Metalloids are located starting with Boron and are located in a ladder shape downward to Astatine! I attached an image for a better visualization! Hope this helps!

Kaili Valenzuela 2B

Cobalt is found at the center of vitamin B12 and also a lot of other co-enzymes. Vitamin B12 is very important to the body for it assists in many functions such as in helping make DNA!

Kaili Valenzuela 2B

What do you call an acid with an attitude?
A-mean-oh acid

Kaili Valenzuela 2B

As said above sigma bonds allow for rotation due to their shape because the electron density lies around the internuclear axis with cylindrical symmetry so this allows for easier rotation that a pi bond cannot because pi bonds have electron density on each side of the internuclear axis so if there w...

Kaili Valenzuela 2B

Hi! I'm having trouble figuring out this question. I thought the coordination number corresponded to the subscripts within the brackets?
Classify each of the coordination compounds according to the coordination number.

Kaili Valenzuela 2B

The shape would be bent because there are the two hydrogens attached to the central oxygen atom, but there are 2 lone pairs of electrons also attached to the atom. Since the electron repulsion between two lone pairs is greater than the repulsion of two bonding pairs they will shift the two hydrogens...

Kaili Valenzuela 2B

The type of bond has no impact on the shape of the molecule because they all equate to one electron density. So the bonding electrons and the lone pair electrons repelling one another are the factors contributing to the shape of the molecule.

Kaili Valenzuela 2B

When determining hybridization the easiest way to think of it is simply by counting how many bonds and lone pairs an atom has. Each of these bonds and or lone pairs count as a region of electron density. Whether the bond is single, double, or triple does not matter in the case of determining hybridi...

Kaili Valenzuela 2B

I noticed this too! I am assuming he just made a mistake because the hybridization should be sp2 not sp3

Kaili Valenzuela 2B

Hello! I'm having trouble figuring out what the three structures are for C3H4 are if someone can please help. Thanks!

Kaili Valenzuela 2B

Hello! The other molecule besides BeCl2 that is linear is XeF2. Xe has 8 valence electrons and F has 7 so in total there are 22 electrons. You have the correct structure of AX2E3, but the structure is linear with Xe in the middle and an F on both sides along with two lone pairs above Xe and one addi...

Kaili Valenzuela 2B

I find it hard sometimes between classes and school work to make room in my schedule in get out and do some exercise so I've found it very help to keep yourself in a routine and have set times to do a workout or go out and get some air! It's a really nice way to clear your mind between all the study...

Kaili Valenzuela 2B

Oxygen, hydrogen, sulfur, sodium, and phosphorous walk into a bar.
"OH SNaP!" says the bartender.

Kaili Valenzuela 2B

Hi! Electron configuration is the number of electrons that are present in the atom and is repressed through the different sub-shells. So for example, the electron configuration for oxygen is 1s^2 2s^2 2p^4. While the valence electrons only refer to the electrons in the outermost shell of the atom. F...

Kaili Valenzuela 2B

Hi! A coordinate covalent bond is the bond between a Lewis acid and a base. It’s basically when the base donates the electrons needed and the acid accepts the electrons. Examples of Lewis bases are F- and OH- while examples of acids are BF3 and H+.

Kaili Valenzuela 2B

I asked the guy siting next to me if he had any Sodium Hypobromite...
He said NaBrO

Kaili Valenzuela 2B

When we have various resonance structures how do we determine which is the most stable/favorable structure? Thanks!

Kaili Valenzuela 2B

This link is super helpful for understanding and visualizing the periodic table trends. There are definitions as well as diagrams of periodic tables with arrows indicating the trends across the table. Hope this helps! https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Modules_and_Websites_...

Kaili Valenzuela 2B

Thank you so much for all your advice and sharing your story! As I was reading through the previous comments I know you said that you should get involved in research only if you are truly interested in it rather than making it something you force yourself to do. I know there are various research opp...

Kaili Valenzuela 2B

Kendall_Dewey_2D wrote:Grey's Anatomy is such a classic! You should also try Hawaii 5-O - never gets old

Yes Hawaii 5-O is my favorite and definitely a must! Would also recommend Haunting of Hill House if you're into suspense as well as Elite and Bates Motel on Netflix!

Kaili Valenzuela 2B

Hi! I've heard people say that it's better to take 14BL after 14B because 14B covers content that will be in 14BL, so that will be helpful. But I also heard it is doable to take both in the same quarter. Hope this helps!

Kaili Valenzuela 2B

Hi! The octet rule refers to the tendency of atoms to prefer to have 8 electrons in the valence shell. When atoms have fewer than 8 electrons, they tend to react and form more stable compounds. There are a few exceptions that Lavelle went over in previous lectures. Make sure to remember those! I ho...

Kaili Valenzuela 2B

Hi! I'm slightly confused as to what exactly delocalized electrons are and how to identify them. If someone can please explain, thanks!

Kaili Valenzuela 2B

Lone pairs are the pairs of electrons that are not shared with another atom during bonding. For example the oxygen atom has 2 lone pairs of electrons. Hope this helps!

Kaili Valenzuela 2B

Molecules with several resonance structures are more stable because the variety of structures allows for the overall energy of the molecule to be lower due to the fact that electrons occupy a greater volume. Hope this helps!

Kaili Valenzuela 2B

Javier Perez M 2J wrote:By what day do we have to post every week?

The last day to post per week is Sunday

Kaili Valenzuela 2B

As said above "ground state" means the lowest energy state that an atom can have and an excited state is when the atom of molecule reaches a higher energy state than its original ground state. Hope this helps!

Kaili Valenzuela 2B

Hi! He got 6e- from the number of valence electrons sulfur has. You can find this number on the periodic table hone locating sulfur you can count it is the 6th element across the row meaning it has 6 valence electrons. He got the number 32e- when he added the 6e- from sulfur, the 24e- from oxygen an...

Kaili Valenzuela 2B

Hello! Identify the reasons why oxygen has a lower first ionization energy than both nitrogen and fluorine. -The 2p electrons in fluorine experience a higher effective nuclear charge than the 2p electrons in oxygen -Upon ionization, oxygen is relieved of electron-electron repulsion I'm having troubl...

Kaili Valenzuela 2B

Hi! The electron configuration is actually [Kr] 4d^10 5s^2 5p^5. When using the shorthand method you take the Nobel gas prior to the element and to find what comes next, which in this case would be the 4d, you just simply start counting the orbitals on the following line of the periodic table. So yo...

Kaili Valenzuela 2B

Hi! I'm having trouble with this problem from the sapling hw The E.coli bacterium is about 1.9 μm long. Suppose you want to study it using photons of that wavelength or electrons having that de Broglie wavelength. What is the energy of the photon? What is the energy of the electron? I've already fou...

Kaili Valenzuela 2B

Hello! I'm having difficultly figuring out how to solve this question on sapling if someone could please help! A blue line is observed at 486.1 nm in the spectrum of atomic hydrogen. Determine the values of n for the beginning and ending energy levels of the electron during the emission of energy th...

Kaili Valenzuela 2B

Hello! I'm having trouble figuring out how to start this problem, could someone please explain it? What is the minimum uncertainty in the speed of an electron confined within a lead atom of diameter 350. pm? Model the atom as a one-dimensional box with a length equal to the diameter of the actual at...

Kaili Valenzuela 2B

Hi! I also saw that the solution manual didn't have the percent difference, but I'm assuming you don'y need to find the percent difference because both the proton and the neutron come out to having the same wavelength.

Kaili Valenzuela 2B

Hello! N represents the energy level. So if an electron is on energy level 4 then n=4 and if the electron drops to a different energy level lets say 2, then n will equal 2. The different between the Lyman and Balmer series is that in the Lyman series an electron either starts or ends on the ground s...

Kaili Valenzuela 2B

Hello!

I'm slightly confused about the rydberg equation and empirical equation. So these equations can only be used when dealing with a hydrogen atom? And so we must use a separate equation if we are dealing with an atom other than a hydrogen atom? Can someone please clear that up?

Thanks!

Kaili Valenzuela 2B

Hello! I am confused on how to go about solving this problem, could someone please explain it to me? In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that le...

Kaili Valenzuela 2B

There is in fact a sheet on the Chem 14A website that includes conversation factors, it's titled constants and equations!
Hope that helps!

Kaili Valenzuela 2B

For your first example of 2kg when you convert to grams you would keep your answer as 2000g because 2000 only has one sig fig since the zeros after the 2 do no count since there is no decimal point after the zeros. If you wrote the answer as 2000. g then that would have 4 significant figures because...

Kaili Valenzuela 2B

Hello! So in order to find the mass of CaCl2 you are going to have to multiply the 36.5% of calcium chloride by the total mass of the mixture, 903.4 g: mass CaCl2= 903.4g x 36.5% = 329.74 g CaCl2 Second, in order to find the mass of water used you are going to have to subtract the mass of CaCl2 from...

Kaili Valenzuela 2B

Hello! I'm having trouble figuring out how to answer this question if someone can please walk me through it? The field of nanotechnology offers some intriguing possibilities, such as the creation of fibers one atom wide. Suppose you were able to string together 1.00 mol Ag atoms, each of radius 144 ...

Kaili Valenzuela 2B

Hello! So you start out answering the problem by writing out the chemical equation for the combustion reaction. When writing an equation for a combustion reaction you have to remember that combustion is just any substance that combines with oxygen to produce carbon dioxide and water. Thus, the equat...

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