CHEMISTRY COMMUNITY

Kavya Immadisetty 2B

Kelvin, just make sure all the units cancel

Kavya Immadisetty 2B

Jade Hinds 2B wrote:due to classes now being cancelled, will step-up/review sessions presume as scheduled or are those all cancelled as well?

I'm pretty sure all sessions will be cancelled

Kavya Immadisetty 2B

Congrats!!!

Kavya Immadisetty 2B

I think Lavelle or the ta's will send out more information about it soon

Kavya Immadisetty 2B

For my math take home final, he is going to upload a pdf of the exam, have us print it out and complete it and then upload it to ccle. He's giving us 24 hours to do so but Idk if we'll get that much time for Chem.

Kavya Immadisetty 2B

Without a salt bridge, the cell would stop working soon because the cathode would be too negative and would repulse the electrons which would stop working. If this were to occur, would the cathode begin releasing electrons back to the anode since it repulses the electrons? I think so. I'm pretty su...

Kavya Immadisetty 2B

I have tried part A several times but I keep coming up with K=1.096. How does the book manage to get 1.0 x 10^80. Does it have something to do with the 2 in front of H20 in the balanced equation? The only Standard Gibbs free energy of formation given by the appendix is -228.57 for H2O I believe. Ma...

Kavya Immadisetty 2B

gibbs free energy!!

Kavya Immadisetty 2B

Without a salt bridge, the cell would stop working soon because the cathode would be too negative and would repulse the electrons which would stop working.

Kavya Immadisetty 2B

I think that if there's no salt bridge, the cathode will become more negative and the anode will become more positive since electrons move from the anode to the cathode. However, the presence of a salt bridge prevents the buildup of charge.

Kavya Immadisetty 2B

Chemistry jokes are sodium funny, I slapped my neon this one!

Kavya Immadisetty 2B

The test will be on the second page of outline 4 and all of outline 5! In terms of lecture, it covers material from the friday after the midterm until Monday's (2/24) lecture.

Kavya Immadisetty 2B

Reducing agent: gets oxidized so it gains electrons

Oxidizing agent: gets reduced so it loses electrons

Kavya Immadisetty 2B

The oxidation number is the number of electrons that an element gains or loses when it makes a bond.

Kavya Immadisetty 2B

LEO the lion goes GER. LEO: lose electrons oxidation GER: gain electrons reduction.

The idea is that when an element's oxidation number (number of electrons) goes down, it's reduced. So gaining electrons will reduce the oxidation number.

Kavya Immadisetty 2B

The cathode should always be listed on the right I think it's the standard.

Kavya Immadisetty 2B

I just knew from AP Chem that neutralization reactions are exothermic. So for this question, I just determined which reaction had the most moles of reaction in the smallest amount of liquid. The more liquid there is, the more heat that can be absorbed without increasing the temperature much. In othe...

Kavya Immadisetty 2B

What sections of the book are going to be covered in test 2? I know Dr. Lavelle didn't get to all of outline 4. So does the material start with 5G?

Kavya Immadisetty 2B

No, they give us any needed entropy values but you should know how entropy will change in general. ex. entropy increases if a liquid becomes a gas

Kavya Immadisetty 2B

I think they're the same

https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=5048

Kavya Immadisetty 2B

He doesn't curve individual tests :( but the overall grade is adjusted at the end of the quarter. There's no hope til the end of the quarter :(((

Kavya Immadisetty 2B

LEO the lion goes GER. LEO: lose electrons oxidation GER: gain electrons reduction.

The idea is that when an element's oxidation number (number of electrons) goes down, it's reduced. So gaining electrons will reduce the oxidation number.

Kavya Immadisetty 2B

Matthew ILG 1L wrote:Will the conversion of 1atm=760 Torr be given to us at all? I have yet to find that on the equations sheet from test one. I could be looking in all the wrong places though.

It's on the constants and formula sheet

Kavya Immadisetty 2B

You should know how an equilibrium shifts when concentrations of species are changed, temperature is changed, or when pressure is changed

Kavya Immadisetty 2B

Enthalpy is equal to the heat of a system if there is no expansion work.

Kavya Immadisetty 2B

Enthalpy is the amount of heat absorbed or released by a reaction if there is no expansion work

Kavya Immadisetty 2B

Will the midterm have problems where we use derivatives and integrals? In what problems would these be used.

Kavya Immadisetty 2B

Internal energy is the sum of potential and kinetic energy.

Kavya Immadisetty 2B

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 5 23.50 kJ), resulting in a temperature rise of 7.32 8C. In a subsequent experiment, 100.0 mL of 0.200 m HBr(aq) and 100.0 mL of 0.200 m KOH(aq) were ...

Kavya Immadisetty 2B

When the phosphate bond of ATP is broken, a small input of energy is required. However, the formation of new bonds (between OH and the last P in ADP) releases lots of energy so the net energy change is an increase in energy.

Kavya Immadisetty 2B

Steam, despite being at the same temperature as water, has more energy because during a phase change, a substance can absorb energy without increasing in temperature. This excess energy is transferred to your skin and causes burns

Kavya Immadisetty 2B

Heat capacities will generally be given on tests.

Kavya Immadisetty 2B

Heat capacities will generally be given on tests.

Kavya Immadisetty 2B

Autoprotolysis is when H+ ions are transferred from 2 molecules of the same species. When you write out the chemical equation for this transfer, you can write a K equation for it.

Kavya Immadisetty 2B

Autoprotolysis is when H+ ions are transferred from 2 molecules of the same species. When you write out the chemical equation for this transfer, you can write a K equation for it.

Kavya Immadisetty 2B

Lavelle said week 3 but I've heard that they will be available for most of this quarter

Kavya Immadisetty 2B

not all phase changes are exothermic, some are endothermic

Kavya Immadisetty 2B

yes, the reverse of endothermic reactions are exothermic and vice versa

Kavya Immadisetty 2B

High heat capacity means that more energy is taken to increase or decrease the overall temperature.

Kavya Immadisetty 2B

A state property doesn't depend on the path taken to get to that state but just the state itself.

Kavya Immadisetty 2B

Although it's not absolutely necessary, it can be helpful.

Kavya Immadisetty 2B

The reason why is because when you say you're using concentrations of partial pressures, you're actually using activities of each species. I think when you calculate the activity of each species, the units cancel out.

Kavya Immadisetty 2B

If pressure is increased, volume decreases. If volume decreases the reaction proceeds to the side with less moles of gas.

If pressure is decreased, volume increases. If volume increases the reaction proceeds to the side with more moles of gas.

Kavya Immadisetty 2B

The 5% rule is just a way of making sure that when you remove the x from the bottom of the fraction, you aren't affecting the answer. The idea is if x is less than 5% of the number its being subtracted from, it makes such a little difference that it is mathematically ok to assume x is 0 relative to ...

Kavya Immadisetty 2B

gabbymaraziti wrote:Can we just use K and not specify Kc or Kp? Or would we be marked down?

I feel like they won't care on the test. But it can't hurt to take a look at the units and add the C or P.

Kavya Immadisetty 2B

If the products require energy to be formed and the temperature increases, the forward reaction will be favored because the system will want to decrease the temperature. To do so, the reactants will react and absorb excess heat (because the forward reaction is endothermic). On the other hand, if the...

Kavya Immadisetty 2B

Although Q and K are calculated the same way, the difference is the state of the reaction at the time when this is calculated: Q can be any specific point of time while K must be when the reaction is at equilibrium.

Kavya Immadisetty 2B

The activity level for both solids and liquids are 1

Kavya Immadisetty 2B

When a mixture is compressed, there is less volume for gasses to exist so the system will shift towards the side with fewer moles of gas. In other words, gasses take up less space so when there is less space, the reaction will go more towards whatever side has fewer moles of gas.

Kavya Immadisetty 2B

Allow the change to be x (ie. on the reactants side, the change would be -2x if the stoichiometric coefficient is 2). Add the change to the initial value to get the equilibrium expression. Plug in the expressions into a K equation and if the value of K is given, algebra can be used to solve for x ak...

Kavya Immadisetty 2B

Although Q and K are calculated the same way, the difference is the state of the reaction at the time when this is calculated: Q can be any specific point of time while K must be when the reaction is at equilibrium.

Kavya Immadisetty 2B

If there are lone pairs, the molecule is probably bent

Kavya Immadisetty 2B

Spin up is +1/2
Spin down is -1/2

Kavya Immadisetty 2B

You use the number of electron densities (lone pairs and bonding pairs) to determine the number of orbitals required.

Kavya Immadisetty 2B

Just a note on this topic: blood usually has a ph of 7.35-7.45 so technically even 7 is acidic

Kavya Immadisetty 2B

Chantel_4B wrote:Does the CO2 make the body more acidic when it interacts with water? Or is it when it interacts with something else? Or by itself?

CO2 reacts with water to form carbonic acid (H2CO3) which is a weak acid that increases the acidity of blood

Kavya Immadisetty 2B

If it contains carbon it is organic ! Actually there are a few molecules that have carbon but are inorganic: CO2, CO, carbonates, carbides, cyanides, cyanates, and thiocyanates. But most bigger molecules that contain carbon are organic so its a good rule of thumb but just keep in mind that that isn...

Kavya Immadisetty 2B

These are the strong acids:
HCl, HBr, HI,
HNO3, H2SO4, HClO4, HClO3

These are the strong bases:
LiOH, NaOH, KOH, RbOH, CsOH
Ca(OH)2, Sr(OH)2, Ba(OH)2

Kavya Immadisetty 2B

A Lewis acid and base accept and donate electrons respectively. Make sure you know the difference between that and Bronsted-Lowry acid and base which donate and accept protons respectively.

Kavya Immadisetty 2B

A Lewis acid and base accept and donate electrons respectively. Make sure you know the difference between that and Bronsted-Lowry acid and base which donate and accept protons respectively.

Kavya Immadisetty 2B

A Lewis acid and base accept and donate electrons respectively. Make sure you know the difference between that and Bronsted-Lowry acid and base which donate and accept protons respectively.

Kavya Immadisetty 2B

I think its asking where the orbitals are pointing. For example, sp² orbitals are pointing towards the corners of an equilateral triangle and form bond angles of 120.

Kavya Immadisetty 2B

Because in biology, the form of a molecule is vital for its function. The fact that pi bonds don't allow for rotation locks the molecule into a certain shape at double and triple bonds which allow molecules to do its function. Also, the fact that pi bonds don't allow for rotation leads to cis and tr...

Kavya Immadisetty 2B

The bond angles in a square pyramidal are slightly less than 90 degrees because of the extra repulsion of the lone pair. The electron geometry is a octahedral so all the bond angles are the same (the term equatorial atom is used for trigonal bipyramidal). For T-shape, the bond angles will always be ...

Kavya Immadisetty 2B

What do we need to know for "lone pairs and the reason for their locations"? I'm not sure what this is referring to I think its talking about molecules with the formula AX4E because the electron geometry is trigonal bipyramidal and the lone pair can be on either the axial or the equatoria...

Kavya Immadisetty 2B

Also for the specific formulas you're asking about, there's only 2 atoms so they can only form 180 degree angles. Just cuz any two points can make a straight line.

Kavya Immadisetty 2B

If the two dipole moments cancel out (ex. CO2), the molecule is considered non-polar and doesn't have dipole-dipole interactions.

Kavya Immadisetty 2B

I doubt it since we didn't really go over it in class/discussion

Kavya Immadisetty 2B

You figure that out by drawing the Lewis structure. You should follow all the rules that we learned the past few weeks (most atoms must have complete octets, you want the lowest possible formal charge, etc)

Kavya Immadisetty 2B

Ionization energy is the energy needed to remove electrons from atoms. Electronegativity is how much an atom attracts electrons.

Kavya Immadisetty 2B

A bigger atomic radii increases the polarizability of the molecule which increases the amount of induced dipole- induced dipole forces in a body of that molecule. More intermolecular forces will lead to a higher boiling point. In short, bigger atomic size leads to a higher boiling point.

Kavya Immadisetty 2B

For a 4p electron, n=4 and l=1. A 4d electron would be l=2.

Kavya Immadisetty 2B

It doesn't really matter how you draw lewis structures (in the sense that it doesn't matter if a certain atom is attached horizontally or vertically to the central atom). Lewis structures are mainly just meant to show which atoms are bonded to which, the number of bonds between two atoms, the number...

Kavya Immadisetty 2B

The first step is to draw the lewis structure https://img1.daumcdn.net/thumb/R800x0/?scode=mtistory2&fname=https%3A%2F%2Ft1.daumcdn.net%2Fcfile%2Ftistory%2F2506B63D57609A5621 Because there are H, O and N, this molecule forms hydrogen bonds. Also, every molecule has london forces.

Kavya Immadisetty 2B

Autoprotolysis is when a proton (H+) is transferred from 1 molecule to another molecule that is identical to the first. For example: 2 H2O --> H3O + +OH - in that reaction, a proton is transferred from 1 water to another, making 1 a bronsted base and the other a bronsted acid. The autoprotolysis con...

Kavya Immadisetty 2B

Will the midterm test on people/experiments? (like Thomson or Millikan)

Kavya Immadisetty 2B

I really doubt you need to know line structures tbh.

Kavya Immadisetty 2B

Stated another way, the question is just asking which structure is more stable and thus more common. So you should check the structure to make sure that all the elements with expanded/incomplete octets are correct, that formal charges are as low as possible, that the number of valence electrons is c...

Kavya Immadisetty 2B

The figure shows a periodic table with the common bond lengths of some elements. So for CF4, each bond is a single bond between C and F (draw the lewis structure to know that). You just go to the table, find the values for a single bond C and for F, and add the numbers together. The length of a sing...

Kavya Immadisetty 2B

Yes because the total possible uncertainty in position is +5 AND -5. So if the position is 10m +/-5m. The position can be anywhere from 5m to 15 m so the uncertainty is 10 m. But you do have to be careful because if the position of a thrown ball is 3m to the left +/- 5m, the uncertainty is not 10 m ...

Kavya Immadisetty 2B

If you find the difference in electronegativity between Be and Br, it's 1.39. Generally, if the difference is less than about 1.5, it will show covalent character.

Kavya Immadisetty 2B

I know for sure that H, Li, Be, and B generally form a duplet instead of an octet. Also, once the elements pass the 3p block, it can have an expanded valence electron shell and form more than an octet.

Kavya Immadisetty 2B

Elements are generally likely to try and form an octet with the valence electrons (exceptions include H, Li, Be, and B who want to create a duplet). So S needs 2 electrons to form a full valence shell so the most likely ion is S 2- . Te is also 2 electrons so it will form Te 2- . Rb is 1 electron aw...

Kavya Immadisetty 2B

I genuinely don't think the TA cares what questions you do as long as they are somewhat current. I say do it on whatever you want to review.

Kavya Immadisetty 2B

Some people write the d-block before the s-block because when an element is losing electrons, it'll lose them from the s-block first. However, my TA said that it's more common for people to write the s-block before the d-block because when electrons are being placed into an element, electrons are ad...

Kavya Immadisetty 2B

The answer at the back of the book says that it wouldn't matter if the element is H or Li.

Kavya Immadisetty 2B

The work function is used to calculate the energy required to remove an electron from a metal.

Kavya Immadisetty 2B

Yes, the answer is D. The first three are all variations of the energy change between a photon and the electron/metal.

Kavya Immadisetty 2B

You remove an electron from the highest energy level (furthest from the nucleus). You can figure out the relative energy levels of orbitals using a periodic table and moving across each row from left to right.

Kavya Immadisetty 2B

This picture shows the energy levels of all the orbitals:

Kavya Immadisetty 2B

The easiest way is to use the periodic table but you can also use this chat:

Kavya Immadisetty 2B

A lobe is a section of an orbital bordered by one or more orbital nodes.

Kavya Immadisetty 2B

N(1) is the final energy level and N(2) is the initial energy level.

Kavya Immadisetty 2B

I think in general you don't include the x, y, z. I know for sure that you don't use it for d orbitals.

Kavya Immadisetty 2B

When and what time is the midterm? (Chem 14a)

Kavya Immadisetty 2B

After the energy of the photon surpasses the minimum energy, increasing the frequency of the photon would not increase the number of electrons ejected because each photon interacts with 1 electron, not multiple. A higher frequency correlates to a higher kinetic energy of the ejected electron. Increa...

Kavya Immadisetty 2B

I study best by doing all the problems in the syllabus (or at least run through them so I know how to do them). I also suggest going through the book or watching the modules and taking the most important notes (like a 1 page cram sheet).

Kavya Immadisetty 2B

If the particle has a de Broglie wavelength of less than 10^-15, it doesn't have detectable wavelike properties.

Kavya Immadisetty 2B

Schrodinger's equation: a very complicated equation that describes the wave function of an atom and thus created quantum mechanics. De Broglie's wave equation: tells you the wavelength given off by any moving particle with momentum (mass and velocity). Heisenberg's indeterminacy equation: says that ...

Kavya Immadisetty 2B

As the others said, the Lyman series is for electrons that end at n=1 and the Balmer series is for electrons that end at n=2. But the main reason why these two regions are highlighted is just because they involve the 2 biggest "jumps" or energy differences. There are other series for other...

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