CHEMISTRY COMMUNITY

Kassidy Tran 1E

There are two ways of calculating standard potential (E). You can either use E_cell = E_cathode - E_anode, in which you just take the standard reduction potentials from the chart and plug them into the equation as is, without changing the signs, or you can add up the half reactions and their standar...

Kassidy Tran 1E

My jokes are kinda boron.. but a lot of the good ones argon.

Kassidy Tran 1E

Are you made out of beryllium, uranium, and titanium ? Cause you're a BeUTi!

Kassidy Tran 1E

I'm having problems understanding what the correct answer for test 2 question 5 is. The question asks whether the pH of & is acidic/basic at 10C, and I have been told to do this problem multiple ways, both with differing answers. One way to solve the problem as I have been told is to find the [H...

Kassidy Tran 1E

The anode is the species giving up an electron (going from a lower to higher positive charge) and the cathode is the one accepting the electron (going from a higher to lower positive charge).

Kassidy Tran 1E

Thank you Dr. Lavelle for all the resources you provide us with to help us pass the class and all the care and concern you show for your students' learning! Your passion for teaching truly inspires me as a student to work hard and succeed.

Kassidy Tran 1E

I'm still a bit confused on how the concentration cell differs from the galvanic cell. How do we distinguish a concentration cell from a galvanic cell by definition, and why do we make the lower concentration the product for the concentration cell?

Kassidy Tran 1E

An example would be the reaction 2H2O --> H3O+ + OH-, where the conjugate base of H2O is OH- and the conjugate acid of H2O is H3O+. In the opposite reaction H3O+ + OH- --> 2H2O, the conjugate base of H3O+ would be H2O, and the conjugate acid of OH- would be H2O. You simply add a proton to find the c...

Kassidy Tran 1E

You need to first add H2O to balance the oxygen, then add more H2O to balance the hydrogens. For however many H2O you add in the second step to balance the hydrogens, you should add the same amount of OH- to the opposite side to ensure both sides are balanced.

Kassidy Tran 1E

I think it's supposed to be an equal sign, maybe? The equation for that doesn't involve subtraction. Okay thank you this makes a lot more sense now. When I enter the values into my calculator I get the same values as the solutions manual. Are you inputting the gas constant as 8.314x10^-3 kJ/(mol*K)...

Kassidy Tran 1E

I’m stuck on the same problem, where does it -0.59 come from?

Kassidy Tran 1E

How do you calculate the temperature a reaction changes from non-spontaneous to spontaneous? Is it at the point where the reaction reaches equilibrium?

Kassidy Tran 1E

How do you rank an element in order from increasing reducing power going from their neutral state to second oxidation state? For example, for the elements Pt, Pb, Cu.

Kassidy Tran 1E

Learning about electrons is exciting, they bring chemistry to a whole new level.

Kassidy Tran 1E

The best thing about learning about equilibrium is that nothing changes.

Kassidy Tran 1E

Two atoms are walking down a street.
One of them shouts, "Hey, I lost an electron!"
The other asks, "Are you sure?"
"Yes, I'm positive!"

Kassidy Tran 1E

In homework problem 15.3 in the 6th edition, the question asks for the unique rate of reaction for 2NO2 —> 2NO + O2. How do you calculate the unique rate of reaction? Is the unique rate of reaction the same as the differential rate law?

Kassidy Tran 1E

Why do chemists like to teach about ammonia? Because it's basic material.

Kassidy Tran 1E

Why are chemists good at solving problems? They have all the solutions.

Kassidy Tran 1E

Did you hear about the man who got cooled to absolute zero?
He's 0K now.

Kassidy Tran 1E

How can you tell when an element is an oxidizing or reducing agent? For example, in the balanced redox equation:
4OH- + 2Cr3+ + 3MnO2 —> 2(CrO4)2- + 2H2O + 3Mn2+

Kassidy Tran 1E

Why did the bear dissolve in water?
Because it was a polar bear.

Kassidy Tran 1E

Why does a pound of hamburger have less energy than a pound of steak?
Because it's in ground state.

Kassidy Tran 1E

Which element is a girl's best friend?
Carbon (diamond).

Kassidy Tran 1E

The system starts at 85C, and since you are given the standard enthalpy at 100C, you have to use 3 different types of deltaS in this problem: the change in entropy when you go from 85C to 100C, the deltaS at 100C, and then the deltaS when you go from 100C to 85C. You have to go through all these ste...

Kassidy Tran 1E

“If SO2F2 adopts a positionally disordered arrangement in its crystal form, what might its molar residual entropy be?” I attemoted this problem by first solving for W so I could use it in S = kBlnW, in which there are 6 different microstates possible for the atoms, but got stuck on how many atoms I ...

Kassidy Tran 1E

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

Kassidy Tran 1E

What did the chemist say when he found two isotopes of helium?
HeHe

Kassidy Tran 1E

The question is “A constant-volume calorimeter was calibrated by carrying out a reaction known to release 3.50 kJ of heat in .200L of solution in the calorimeter (q = -3.50 kJ), resulting in a temperature rise of 7.32 C. In a subsequent experiment, 100.0 mL of .200 M HBr(aq) and 100.0 mL of KOH(aq) ...

Kassidy Tran 1E

What is Iron Man's gender?
Fe Male

Kassidy Tran 1E

Why did chlorine get in trouble for the acid attack?
It was guilt by dissociation.

Kassidy Tran 1E

What did the pregnant scientist say at the end of her electrolysis experiment?
"My water broke"

Kassidy Tran 1E

Hopefully we will have review sessions this quarter just like we did for Lavelle's 14A classes last quarter. If anything, he will announce it in the next class.

Kassidy Tran 1E

What is CH2O?
Seawater.

Kassidy Tran 1E

Whats the molecular formula for coffee?
CoFe2

Kassidy Tran 1E

Why was the mole of oxygen excited when he left the singles bar?
He got Avogadro's number.

Kassidy Tran 1E

When the volume is halved for a system at equilibrium that contains 1.85 M H2, 1.36 M N2, and 2.91e-3 M NH3 with an initial Kc at 9.83e-7, how can you determine the new concentrations for N2, H2, and NH3?

Kassidy Tran 1E

I'm a bit confused on when we need to apply the quadratic formula and use the ICE table. How can we tell when to use this?

Kassidy Tran 1E

Did you hear about the joke about Cobalt, Radon, and Yttrium? It was so CoRnY.

Kassidy Tran 1E

I tried writing a joke about the periodic table, but I wasn't in my element.

Kassidy Tran 1E

Two chemists walk into a bar. One says, "I'll have an H2O." The second one says "I'll have an H2O too." The second chemist dies.

Kassidy Tran 1E

When do you know whether to place the lone pairs on the equatorial axis instead of the axial axis? For example, for ICL3 which has the VSEPR formula AX3E2, why do we place the two lone pairs on the equatorial axis (resulting in T-shaped molecule) instead of placing them opposite of the other on the ...

Kassidy Tran 1E

You don’t need to use the prefix mono-,since the name of the molecule alone should imply that there is only one molecule. For example, if there was a one amine in the coordination complex, you would just say “amine-“ instead of “monoamine-“ as they both mean the same thing.

Kassidy Tran 1E

How do you determine which acids are stronger or weaker? For example, between CF3COOH, CH3COOH, and C(CH3)3COOH?

Kassidy Tran 1E

Using these rules, does that mean that BrO is a stronger acid than IO as well?

Kassidy Tran 1E

Due to the shape of oxalate, it can only bind in two places. Referring to the last image posted, its highly unlikely that the other two oxygens can bend to bind with the TM in the center.

Kassidy Tran 1E

I believe that a chelate is a coordination compound with a polydentate ligand.

Kassidy Tran 1E

How can you tell which compound will have a higher boiling point? For example, between the two molecules H2S and H2Se?

Kassidy Tran 1E

I think < 109.5 should be used, since its easier to make a mistake when memorizing all of those numbers, but in the end I don't think it actually matters.

Kassidy Tran 1E

In determining which molecules have higher polarizing power, what is more significant their charge or their size? For example what is the process we take to determine Rb+ has a higher polarizing power than Sr2+? Rb+ actually has a lower polarizing power than Sr2+. Since Sr2+ has a higher charge tha...

Kassidy Tran 1E

You can generally determine the bond angles if you know the shape too. For example if you know the shape is trigonal planar, then you can just divide 360 by 3 and get 120 degrees. This also applies to the trigonal bipyramidal, as that is essentially a trigonal planar shape intersected with a linear ...

Kassidy Tran 1E

There is less overlap in a pi bond than a sigma bond, since the orbitals are parallel to each other. Since there is more overlap in a sigma bond, sigma bonds are stronger than pi bonds.

Kassidy Tran 1E

What kind of fish is made up of sodium?
2 Na.

Kassidy Tran 1E

What kind of dogs do chemists have?
Laboratory Retrievers.

Kassidy Tran 1E

Due to the resonance structures, the average of the bond lengths of the different structures should have blended together, so you estimate the bond length between 120 and 140, and that's how you get around 130.

Kassidy Tran 1E

^Exactly. Higher melting points indicate more stability so this explains the example given in class: GC base pairs in DNA are more stable than AT base pairs. So does this mean GC base pairs have stronger bonds than AT base pairs? Yes, because G-C base pairs have three hydrogen bonds rather than two...

Kassidy Tran 1E

For a hydrogen bond to form a hydrogen must have a partial positive charge from being bonded to a atom with higher electronegativity (like N, O, or F). The partially positive hydrogen is then attracted to a partially charged negative atom. For example in the case of water, since H is bonded to O whi...

Kassidy Tran 1E

What causes an induced-dipole? What is an example of an induced-dipole between two molecules?

Kassidy Tran 1E

Silver walks up to Gold in a bar and says, “AU, get out of here!”

Kassidy Tran 1E

Whats the chemical formula for banana?
BaNa2.

Kassidy Tran 1E

On the midterm review worksheet, could someone explain how to draw the lewis structure for XeO2F2? Xe should be the center atom, with 2 F's and 2 O's attached to it. The total number of electrons should be 34e-, so there should be one bond between Xe and the F's, and each F should have 3 lone pairs...

Kassidy Tran 1E

Whats the difference between chemistry and cooking? In chemistry you never lick the spoon.

Kassidy Tran 1E

Why did the white bear dissolve in water? Because it was polar.

Kassidy Tran 1E

What is a cation scared of? A dogion.

Kassidy Tran 1E

I don't think it matters, it just symbolizes the direction of the electron's spin. The +/- of the 1/2 denotes the direction of the spin of the electron, and has no relation to the energy level of it.

Kassidy Tran 1E

How do you determine the value for repulsion between the two electrons in the expression for the colombic potential energy of an atom?

Kassidy Tran 1E

which version of textbook do you have? I have the 6th edition and 2.19b asks for "How many values of m are allowed for an electron in a 6d-subshell?" to which the answer would be m= -2, -1, 0, 1, 2 since l=3 as the electron is in a d-orbital.

Kassidy Tran 1E

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

Kassidy Tran 1E

What did the scientist say when she found two isotopes of helium?
HeHe.

Kassidy Tran 1E

One guacamole is 6.022x10^23 guaca; also known as Avacado's constant.

Kassidy Tran 1E

Will we be given the molar mass of elements on the exam? or will we have to memorize the molar masses of the elements? I noticed that in the module assessments we were given the molar mass for some of the elements, but not all.

Kassidy Tran 1E

I'm a bit confused on this problem:
Use the Rydberg formula for atomic hydrogen to calculate the wavelength of radiation generated by the transition from n = 4 to n = 2.
In this problem, would 4 be considered n1 and 2 be n2? Or should it be the other way around to avoid any negative values?

Kassidy Tran 1E

This is the formula for the kinetic energy of an electron. m(e-) is the mass of the electron, and v(e-) stands for the velocity of the electron.

Kassidy Tran 1E

You might have to, since it appears in some of the homework questions from week 1. Calculating the percent yield is simple, you just need to divide the actual yield over the theoretical yield and multiply that by 100%.

Kassidy Tran 1E

In the textbook it states that reagents are the chemicals available in a laboratory. When a reagent is being used in a particular reaction it is called a reactant.

Kassidy Tran 1E

You need three posts per week, not one post per week.

Kassidy Tran 1E

Q: What do you call a clown in prison?
A: A silicon.

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