CHEMISTRY COMMUNITY

Madeline Phan 1E

Thank you for being such an incredible, patient, and dedicated UA. I wouldn't have understood most of the topics we went through in class without your help. Thank you again for spending your free time helping freshmen navigate general chemistry. Good luck with the rest of your adventures!

Madeline Phan 1E

Adriana_4F wrote:Will the final still be worth 180 points now that it is take home and open book?? I really hope so :/

The final will still be 180 points.

Madeline Phan 1E

k' is the rate of the reverse reaction.

Madeline Phan 1E

There is a take home final that is worth 180 points still.

Madeline Phan 1E

I love this thread! I want to say thank you to Dr. Lavelle as well for being an incredible professor and for making me realize that I actually really enjoy chemistry. I actually looked forward to studying for the class. I love how dedicated he was to teaching it and how dedicated he was to ensuring ...

Madeline Phan 1E

Balancing in acidic solutions means adding H+ and H2O while balancing in basic solutions means balancing with OH- and H2O

Madeline Phan 1E

You use Kelvin since the units of R include Kelvin.

Madeline Phan 1E

You add a conducting solid such as platinum when there is no conducting in solid in one of the half reactions.

Madeline Phan 1E

If the reaction is endothermic, adding temperature increases K. If the reaction is exothermic, adding temperature reduces K.

Madeline Phan 1E

The more negative cell potential has the most powerful reducing power and is therefore the anode.

Madeline Phan 1E

The oxidized molecules should be on the left and the reduced should be on the right because that is how the equation is set up for cell diagrams.

Madeline Phan 1E

Mn goes from +7 to +2 which means it gained electrons and diminishes its positive charge, indicating that it is reduced.

Madeline Phan 1E

Yes, Test 2 covers the second page of Thermodynamics which includes 5G and 5J.

Madeline Phan 1E

A negative delta G indicates a spontaneous reaction, and a positive delta G indicates a nonspontaneous reaction.

Madeline Phan 1E

Test 2 covers the second page of thermodynamics and the entirety of electrochem.

Madeline Phan 1E

It is okay to leave the temperature in Celsius or Kelvin when calculating delta T because the number of units that increase or decrease will remain the same no matter what.

Madeline Phan 1E

Pt stands for platinum and is used as an inert conductor in cell diagrams.

Madeline Phan 1E

NH4Cl can dissociate and donate a proton to the water, lowering the pH.

Madeline Phan 1E

Yes, we can assume the oxidation number of oxygen is -2 when it stands alone.

Madeline Phan 1E

Delta G0 is at standard conditions, while delta G is the G value of the reaction at any point in time.

Madeline Phan 1E

Na is the number of atoms and it is found using avogadro's number.

Madeline Phan 1E

Gibbs Free Energy is definitely the best indicator of spontaneity as it takes into account entropy and enthalpy.

Madeline Phan 1E

Cl- gains electrons and becomes reduced. As this happens, it oxidizes the H2S, making it lose electrons.

Madeline Phan 1E

Gibb's free energy is the amount of energy available to do work. It is also the prime indicator of whether a reaction is favorable (spontaneous) or not.

Madeline Phan 1E

Lavelle doesn't adjust overall grades until the end of the quarter, so no there is no curve for any individulal test.

Madeline Phan 1E

you can assume that when pressure is constant.

Madeline Phan 1E

a closed system has inflows and outflows of energy and that can be affected by temperature, pressure, and volume.

Madeline Phan 1E

you can use L atm and then convert that to joules. 1 L am is equal to 101.325J

Madeline Phan 1E

A negative value of q corresponds to an exothermic reaction, and thus a positive value would indicate an endothermic reaction.

Madeline Phan 1E

Combustion is an exothermic reaction, so delta H should be negative.

Madeline Phan 1E

A state property is a quantity of a substance that doesn't affect how the substance is made.

Madeline Phan 1E

You just need to know that the standard enthalpies of an element in its purest form is zero.

Madeline Phan 1E

Yes, pressure and volume are inversely related.

Madeline Phan 1E

I think it covers Outlines 1-4.

Madeline Phan 1E

Yes, they need to be on opposite sides of the reaction to cancel out.

Madeline Phan 1E

The chemical equations are usually given to you, but you should definitely know equations between acids and their conjugate bases and bases and their conjugate acids.

Madeline Phan 1E

Autoprotolysis occurs when a proton is transferred between two identical molecules.

Madeline Phan 1E

A pH of 7 is neutral. Lower than that is acidic and higher than that is basic.

Madeline Phan 1E

you can approximate if k < 10^-3

Madeline Phan 1E

To find pka from pkb you can do 14-pka and vice versa.

Madeline Phan 1E

When your K value is smaller than 10^-3, you can ignore the minus x in the denominator and use an approximation to determine molar concentration. you can then make sure an approximation is allowed by seeing if your x is less than 5 percent of K.

Madeline Phan 1E

Kw is the equilibrium constant for water.

Madeline Phan 1E

Solids and liquids do not apply to Le Chatelier's principle as they do not affect the equilibrium constant.

Madeline Phan 1E

Adding an inert gas does not have an effect on the equilibrium constant.

Madeline Phan 1E

I would definitely do as many of the homework problems as you can, as the TA's make the tests and they model them after the homework problems.

Madeline Phan 1E

Q is the value of products over reactants at any given time in the equation. K is the value of products over reactants when the reaction has reached equilibrium.

Madeline Phan 1E

The equilibrium constant requires no units.

Madeline Phan 1E

The reverse reaction begins at the time when q is greater than k and there are more products than reactants.

Madeline Phan 1E

In the expression for k, the reactants are in the denominator. So when there is higher pressure of reactants, the equilibrium constant is actually smaller because you are dividing the pressure of the products by a larger number.

Madeline Phan 1E

when writing the expression for k, how do you know when to use brackets or to write p in front?

Madeline Phan 1E

I think the TA's will input the points at the very end.

Madeline Phan 1E

Lewis acids and bases focus on electron pairs. A Lewis acid is an electron pair acceptor and a Lewis electron pair donor. Bronsted focuses on protons. A bronsted acid is a proton donor and a Bronsted base is a proton acceptor.

Madeline Phan 1E

Also, why are there p orbitals that are filled along with the hybridized orbitals?

Madeline Phan 1E

How much of the acid-base section is going to be on the final? I'm not sure what to focus on.

Madeline Phan 1E

Are there going to be any final review sessions on coordination compounds because the one that was meant for coordination compounds ended up only being about intermolecular forces instead?

Madeline Phan 1E

pka is the negative log of Ka.

Madeline Phan 1E

Acid rain occurs when compounds like sulfur dioxide and nitrogen oxides are released in the air and react chemically with water, oxygen, and other pollutants in the air.

Madeline Phan 1E

The bond between H and Cl is stronger than the one between H and F due to the fact that fluorine is less stable than chlorine and more prone to dissociate.

Madeline Phan 1E

Strong acids do dissociate completely in water, whereas weak acids do not.

Madeline Phan 1E

The conjugate acid receives the proton, and the conjugate base donates the proton.

Madeline Phan 1E

You only need to know that a triple bond contains 1 sigma and 2 pi bonds.

Madeline Phan 1E

An oxidation number represents the number of electrons lost or gained by an electron in a redox reaction.

Madeline Phan 1E

In the VSEPR model, they are actually significantly far apart because the electrons are trying to get as far apart as possible.

Madeline Phan 1E

We will probably get them back in discussion this week.

Madeline Phan 1E

Week 9 and 10 homework will be turned in on Week 10

Madeline Phan 1E

you want to satisfy the octet rule first, and then check the formal charges on each atoms to see if there needs to be multiple bonds between atoms.

Madeline Phan 1E

You simply need to relate bond strength to melting point. For example, a molecule involved in hydrogen bonding would have a higher melting point than one with merely dispersion forces because hydrogen bonds are stronger than London dispersion forces.

Madeline Phan 1E

It is the symmetrical shape of carbon tetrachloride that allows its bond polarity to cancel out.

Madeline Phan 1E

You just need to memorize the bond angles for the basic molecular shapes without lone pairs, and understand that lone pairs make the angles slightly less than what they are.

Madeline Phan 1E

When drawing Lewis structures you should pay attention to number of electrons, and then the octet rule, and then formal charge in order of increasing importance.

Madeline Phan 1E

In order of increasing strength it would be dispersion forces, then dipole-dipole, then ion-dipole, and lastly hydrogen bonding (which are 10 percent the strength of covalent bonds)

Madeline Phan 1E

Lewis acids accept pairs of electrons, while Lewis bases donate entire pairs so they form coordinate covalent bonds since the bases are donating an entire pair of electrons.

Madeline Phan 1E

Usually, ionic bonds are stronger because of the higher difference in electronegativity. However, ionic bonds in aqueous solution are actually weaker than covalent bonds because the electronegative regions of the water are attracted to the positive and negative ions in the ionic compound.

Madeline Phan 1E

Yes, elements from period 3 and onward have a d shell that can still add on extra electrons.

Madeline Phan 1E

I just went to discussion today and my TA said that they will be given out in discussion next week, or at least by next Wednesday.

Madeline Phan 1E

So for our midterm, we will just get a raw score for now?

Madeline Phan 1E

I'm a little confused on how Lewis acids and bases form coordinate covalent bonds. Can someone explain this to me?

Madeline Phan 1E

Do resonance structures have to optimum formal charge when we are drawing them? Also, how does one draw a resonance hybrid?

Madeline Phan 1E

What is the difference between molecular spectroscopy and atomic spectroscopy?

Madeline Phan 1E

I don't really understand the Schrodinger Equation and how it relates to wave function and orbitals. I know we don't need to know how to use it, but can someone explain to me the significance of it?

Madeline Phan 1E

On Outline 2 it says we need to know how to derive the de Broglie equation. Can someone explain to me how to do this?

Madeline Phan 1E

I didn’t understand why oxygen received a negative charge instead of silver. Can someone please explain this to me? Oxygen gets the negative charge because it has a higher electronegativity than sulfur. If you look at the periodic table, oxygen and sulfur are in the same group but oxygen is above s...

Madeline Phan 1E

How do you know which elements are able to have an expanded octet?

Madeline Phan 1E

Cations are atoms that lose electrons in order to achieve a full valence shell. They tend to be metals. Anions gain electrons in order to complete their valence shell and tend to be non-metals. Cations lose electrons because they tend to have 3 or less valence electrons in their last shell, and it i...

Madeline Phan 1E

When a molecule has resonance structures, its bond lengths don't actually look like any one resonance structure. It is actually has an average bond length of all the resonance structures.

Madeline Phan 1E

Covalent bonds form between non-metal atoms as they are more similar in electronegativity, while ionic bonds form between non-metals and metals as they have extremely different levels of electronegativity.

Madeline Phan 1E

A wave function is a mathematical equation that tells us the shape of an area in which an electron might be.

Madeline Phan 1E

Planck's constant is a significant one you need to remember. The value is 6.262 * 10^-34 J*s.

Madeline Phan 1E

Usually, the masses that are required for a calculation are given in the problem or on the formula sheet.

Madeline Phan 1E

Momentum refers to the quantity of motion an object has and is equal to mass times velocity.

Madeline Phan 1E

You probably need to know the wavelength times frequency = speed of light equation, the E= hv equation, the Schrodinger equation, and the photoelectric effect equation with kinetic energy, the energy absorbed and the work function.

Madeline Phan 1E

Electron mass is usually given in the question or the formula sheet.

Madeline Phan 1E

Is the workshop the "Step-Up" type?

Madeline Phan 1E

As a premed student, I found your story refreshing and inspiring. Sometimes it's hard to remember why I chose the path that I did, but hearing your story made me want to push on and work as hard as I can to reach my goals. Thank you for taking your time to share your experiences and be open about yo...

Madeline Phan 1E

The Rydberg equation is found in our textbook and is used to calculate the wavelength of any spectral line in many chemical elements. However, Dr. Lavelle taught us a different approach in class because the Rydberg equation does not really show us why everything is solved the way it is.

Madeline Phan 1E

According to the syllabus, Test 1 and Test 2 are both worth fifty points each. Although there were 7 questions on Test 1, I'm sure partial credit will be given for each question.

Madeline Phan 1E

For Week 2, I did problems on Fundamentals as a practice for Test 1. But for Week 3, we definitely have to do problems from the Quantum World.

Madeline Phan 1E

I think that you definitely need to show the mole to mole rations for limiting reactant problems on the tests, as those are the key parts of the problem that Dr. Lavelle wants you to understand.

Madeline Phan 1E

The number of sig figs you use should depend on the number with the least number of sigfigs given in the question. For example, if the problem gives you an amount like 3.2 grams and 4.56 grams, your answer should have 2 sigfigs since 3.2 grams only has 2 sigfigs.

Madeline Phan 1E

In the lecture, Dr. Lavelle says that we won't really be working with Giga, Mega, or Deci very much. I think the main ones are definitely kilo, centi, milli, and pico.

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