CHEMISTRY COMMUNITY

Juana Abana 1G

Michael Nguyen 1E wrote:If you see a graph of [A] v. t and it is linear with a negative slope, you know that the reaction is zero-order with respect to that reactanct. The rate constant k is equal to the negative of the slope.

Thank you this is very helpful.

Juana Abana 1G

In a zero order reaction concentration of the reactants does not affect rate.

Juana Abana 1G

Brooke Yasuda 2J wrote:Yes, the anode is the product and the cathode is the reactant. This makes sense because in the anode the concentrations of reactant are decreasing as it forms product in the cathode.

So then the anode is always the product and the cathode is always the reactant?

Juana Abana 1G

If there isn't a solid electrode in the half reaction then you would add an inert electrode such as Pt.

Juana Abana 1G

Daniela Shatzki 2E wrote:if two are given you can't use the formula Ecell = Ecathode - Eanode and then decide which is which based on which arrangement will give you a positive overall value.

Does this work all the time?

Juana Abana 1G

Anode || Cathode
s | g | aq || aq | g | s

Juana Abana 1G

I find it very helpful to write out the half reactions to really gain an understanding of the redox reaction. To do this, you will have to determine the oxidation numbers of the elements being reduced and oxidized. Toolbox K.1 on page F80 is very useful to refresh on oxidation numbers. Thanks this ...

Juana Abana 1G

You would use H+ to balance out the hydrogens.

Juana Abana 1G

Simplifying can be done after adding both half reactions.

Juana Abana 1G

To balance acidic solutions you add H2O to balance the O's and then add H+ to balance the H's. Then you balance the electrons. However when balancing basic solutions you add H2O to balance the O's and then add H+ to balance the H's, but for every proton that you add you also add OH- to both sides of...

Juana Abana 1G

They are located in Appendix 2B in the textbook.

Juana Abana 1G

Your n value is found by balancing the equation and determining the number of electrons that it took to balance it. So basically your n value is the number of electrons that it took to balance the equation.

Juana Abana 1G

You would use Pt(S) in a cell diagram if there is no other metal present in the reaction that can be used as the conductor.

Juana Abana 1G

BAlvarado_1L wrote:galvanic cells are positive while electrolysis is negative a helpful way to remember this is by knowing that electrolysis requires electricity to occur

Thank you, this is a very helpful way to remember!

Juana Abana 1G

Yes, they most likely will provide those values on the formula sheet.

Juana Abana 1G

No, you do not need to include the coefficient of the molecules. You only include their states.

Juana Abana 1G

i get confused on how to figure out which one is being reduced and oxidized in redox rxns. Does anyone know how I can tell the difference for example MnO4^- to Mn^2+. Since it is going from a negative to positive charge in the end wouldn't it mean that it is being oxidized? Yes, I also get confused...

Juana Abana 1G

If the delta g value is negative then the reaction is considered spontaneous.

Juana Abana 1G

The value of a state function is only dependent on the initial value and the final value.

Juana Abana 1G

Delta U is zero when there is no change in temperature.

Juana Abana 1G

When a system does work then work is positive, but when work is being done on a system then work is negative.

Juana Abana 1G

Extensive properties depend on the amount of matter being measured meanwhile intensive properties don't.

Juana Abana 1G

You would use kelvin.

Juana Abana 1G

An insulated water bottle can be considered an isolated system because it can neither exchange any substances nor energy with its surrounding.

Juana Abana 1G

To determine when to use which it is best to look at the units to see which units will cancel out and also see what units you will be left with.

Juana Abana 1G

When the K value is less than 10^-3 then you can assume that the K value it is too small to affect the concentration.

Juana Abana 1G

Yes, you would include it if it was a gas.

Juana Abana 1G

A negative delta H is exothermic since energy is being released.

Juana Abana 1G

When bonds are formed they become more stable and therefore release energy.

Juana Abana 1G

Michael Du 1E wrote:Can anyone please clarify the differences between the reversible and irreversible process? thank you

Yes, I am confused on this as well.

Juana Abana 1G

If a bomb calorimeter is used then it is an isolated system

Juana Abana 1G

State functions are properties whose value does not depend on the path taken to reach that specific value. Some examples are internal energy, enthalpy, and entropy. However, things like heat and work aren't state functions, because they depend on the path taken from the initial to the final values....

Juana Abana 1G

Steam causes severe burns since it experiences a phase change and releases a big amount of heat when it comes into contact with skin

Juana Abana 1G

Because of the fact that the beaker is open and exposed to the atmosphere that is very large in comparison to the beaker, the pressure within the beaker remains constant.

Juana Abana 1G

An open system can exchange matter and energy with its environment, a closed system can exchange only energy with its environment, and an isolated can not exchanged anything with its environment.

Juana Abana 1G

Sofia Barker 2C wrote:I believe Dr. Lavelle covered autoprotolysis as a way of explaining how 10^-14 = Kw = Ka * Kb, an equation crucial to calculating equilibrium constants and pH / pOH. Other than that, I don't think there's anything else important to know about autoprotolysis.

Oh okay this makes sense...thank you.

Juana Abana 1G

Temperature changes the equilibrium constant (K).

Juana Abana 1G

Yes, as long as the percent Ionization is less than 5% we don't have to do the quadratic equation.

Juana Abana 1G

For the pH value only the numbers after the decimal point count as significant figures.

Juana Abana 1G

I believe that based on the information you are given, like whether the products or the reactants are increasing or decreasing, would determine whether the change is positive or negative. Something to keep in mind: -If you are given initial concentrations and all of them are nonzero, calculate the ...

Juana Abana 1G

K only changes when the temperature changes.

Juana Abana 1G

Yes, H20 is included in the K and the Q equation when it is a gas. The only things that you do not include in these equations are solids and liquids.

Juana Abana 1G

PV=nRT is used to convert between Kc and Kp.

Juana Abana 1G

No, the order that the reactants and products are written should not matter as long as the products are in the numerator and the reactants are in the denominator.

Juana Abana 1G

All the conjugate base/acid of a strong acid or base will not affect the pH of the solution because they are the extremely weak conjugate base and acid of strong acid and base and therefore will not play a role in changing the pH level. Oh okay... this makes sense as to why strong acids and bases w...

Juana Abana 1G

Natalie Benitez 1C wrote:What is the difference between the bar unit and the atm unit for pressure?

Yes, I have the same question.

Juana Abana 1G

Q and K are calculated using the same equation however, K calculates the reaction at equilibrium meanwhile Q can calculate a particular point in a reaction.

Juana Abana 1G

Yes, you solve for Q the same way you would solve for K.

Juana Abana 1G

Yes you would leave out solids and liquids.

Juana Abana 1G

Use K when the reaction is at equilibrium.
Use Q at any point in the reaction (when the reaction is not at equilibrium).

Juana Abana 1G

oh okay, so the more electronegative the more stable the anion?

Juana Abana 1G

so is it fine to just know the pH formula?

Juana Abana 1G

Yes, water is an amphoteric compound because it can act as a base or as an acid.

Juana Abana 1G

A Bronsted Acid is a proton donor, a Lewis Acid accepts an electron pair. These are interchangeable because they are saying the same thing. When a proton is donated, the molecule becomes more negative, which is like accepting an electron pair. Bronsted and Lewis acids are the same thing, just a dif...

Juana Abana 1G

Yes, we have to turn in homework for last week and this week.

Juana Abana 1G

Acids are proton donors and bases are proton acceptors.

Juana Abana 1G

Yes, I feel like most of the final will consist more on what we covered more recently.

Juana Abana 1G

Clean coal has less sulfur which contributes less to acid rain.

Juana Abana 1G

I think the important thing about cisplatin is the way its structure affects its biological function. Because the two chlorine atoms are next to each other instead of across, they can bond to both sides of DNA's double helix, preventing it from "unzipping" and therefore stopping replicati...

Juana Abana 1G

Yeah, the final exam is cumulative.

Juana Abana 1G

You don't have to write a subscript if it is just 1 but you can if you want.

Juana Abana 1G

If a molecule has dipole moments that do not cancel, then it is polar. If the dipole moments do cancel, then it is non-polar. One general rule to know is that molecules with a tetrahedral shape generally are non-polar unless the the outer atoms are not identical. Also while linear shaped molecules ...

Juana Abana 1G

Yeah, you maybe able to get the test back during office hours but I'm not sure.

Juana Abana 1G

Yes, it should be less than 90 or 120 because of the lone pair repulsion.

Juana Abana 1G

Yes, hydrogen bonding can only occur if an H atom is bonded with a N, O, or F atom.

Juana Abana 1G

We would have to be able to identify the shape as well as the angles between the atoms.

Juana Abana 1G

Andrew Liang 4G wrote:Another tip that I learned from my TA today was that most of the time when the central atom has lone pairs then the molecule is most likely to be polar.

Thanks for the tip this is really helpful.

Juana Abana 1G

Atomic radius increases as you move down a group as well as when you move from right to left on a period. It is basically the opposite of electronegativity.

Juana Abana 1G

I think you can in questions from the chemical bonds section or the molecular shape and structure section.

Juana Abana 1G

Yes, the most electronegative atom should be the one to carry the negative charge since it has a stronger pull of electrons.

Juana Abana 1G

On the periodic table electronegativity increases from left to right and decreases from top to bottom.

Juana Abana 1G

Double bonds are shorter and stronger since the electrons between the two elements are pulled closer together.

Juana Abana 1G

The midterm should be graded by next week.

Juana Abana 1G

Anything from the third row the periodic table and the rows that follow can have expanded octets.

Juana Abana 1G

Jorge Ramirez_4H wrote:What week is this test?

Test 2 will be given on week 8.

Juana Abana 1G

Unfortunately the final will be have to be written in pen just like the midterm and the tests.

Juana Abana 1G

You add double bonds to a lewis structure in order to satisfy the octet rule and make the molecule more stable. You would also add double bonds in order to decrease the formal charges of the molecule.

Juana Abana 1G

Kennedi3K wrote:Does anyone know if Sapling is mandatory?

No you don't have to buy it. It is another additional resource that you can use.

Juana Abana 1G

Yes, the midterm will include everything up to week five.

Juana Abana 1G

Yeah, most likely since that is what we are going over in lecture.

Juana Abana 1G

If I understood correctly the 4s sublevel is lower in energy and that is why it is filled before the 3d sublevel because the 4s is lower in energy. However, after the 4s state is occupied the 3rd state becomes lower in energy. Because the 4s orbital then behaves as the outermost, highest energy orb...

Juana Abana 1G

JohannaPerezH3D wrote:I've also been struggling a lot with keeping up with the material, so if anyone wants to study together and prepare lemme know but I think something that is definitely important is to prepare before the week starts

Yes, me too.

Juana Abana 1G

Yess Bozeman science does really help.

Juana Abana 1G

You can generally memorize the number of orbitals, but if you want to be technical... You can figure out the number of orbitals per sub shell through the quantum numbers! The subshells are depicted by l = 0,1,2,3 (which is s,p,d, and f, respectively). The magnetic quantum number m represents the in...

Juana Abana 1G

jeffreygong1I wrote:It just means that most atoms prefer to have(are most stable with) eight valence electrons, although there are exceptions...

Yup, I agree.

Juana Abana 1G

Only test 2 will be given in discussion. The midterm and final will be given outside of discussion at different locations and at different times.

Juana Abana 1G

The equation sheet we got on the first test will be given to us for all the other tests.

Juana Abana 1G

You would use the equation: E = hv

Juana Abana 1G

The units for hertz is one cycle per second (s^-1)

Juana Abana 1G

Drake Choi_1I wrote:Is there going to be a curve for the midterm? Or is grade based on raw score?

The syllabus mentions that the tests aren't curved.

Juana Abana 1G

There is no course reader for the class.

Juana Abana 1G

In order to find the empirical formula, you should first turn the grams given into a percentage. Then divide by the molar mass, and then divide by the smallest value.

Juana Abana 1G

I think it would be better to multiply the faction in order to get an integer.

Juana Abana 1G

I think if after dividing you get .9 then it is okay to round up in order to get the empirical formula.

Juana Abana 1G

The number of sig figs depends on the lowest number that they give you in the problem.

Juana Abana 1G

magaliolide1D wrote:Do the moles of a solute change when being diluted at all, in any instance? If not, why?

Yes I was confused on this as well.

Juana Abana 1G

Does anyone know if the homework needs to be written in pen or is it fine to write it in pencil?

Juana Abana 1G

Yes, you have to multiply both sides of the equation by the smallest factor in order to get rid of the fraction.

Juana Abana 1G

"Sig figs" is a shorthand term for "significant figures," a term in chemistry used to help gauge level of accuracy as well as error. The general rule is that your answer should contain the same number of significant figures as the term in the problem with the lowest number. Exam...

Juana Abana 1G

I definitely suggest showing your work because it's easier to go back and see what you did step by step when you need to study for the test/midterm/final.

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