CHEMISTRY COMMUNITY

Max Madrzyk Dis 4G

Yeah, I'm pretty sure they will be given although there are some derivations that you should know how to use that may not be on the equation sheet. But now that the final is take home this should not be a problem.

Max Madrzyk Dis 4G

I'm pretty sure the problem will have to tell you if the step is fast or slow. All the practice problems I've done so far have specified.

Max Madrzyk Dis 4G

An intermediate shows up in the products of step one but the reactants of step two and therefore is used up in the second reaction so none will remain after the whole thing is over. The reason this does not affect the rate law is because the rate law is determined by the reactants of the slow step a...

Max Madrzyk Dis 4G

The stoichiometric coefficients are equal to the order for the reactants of the rater determining step or the slow step.

Max Madrzyk Dis 4G

k' is just for the reverse reaction and kr is for the forward reaction.

Max Madrzyk Dis 4G

You use lines when you have a state change an commas when you have a charge change I think.

Max Madrzyk Dis 4G

Isn't that already balanced?

Max Madrzyk Dis 4G

1. balance elements
2. balance oxygens (use h20)
3. balance hydrogens (use H+ for acidic and OH- for basic)
4. balance charge (with electrons)
5. multiply half reactions so the electrons cancel
6. combine half reactions

Max Madrzyk Dis 4G

I think the higher the value of K, the higher the value of Ecell.

Max Madrzyk Dis 4G

Yeah, I think my TA said that the anode should be on the left and the cathode should be on the right. To tell what's being oxidized and reduced I like to write out the skeletal equation and then just work out the half reactions from there.

Max Madrzyk Dis 4G

Make sure you have all of your elements balanced and then make sure you multiply any molecules with a charge by their coefficient and then you should be able to get the right number of electrons.

Max Madrzyk Dis 4G

From what I've seen from the homework problems I think they have to tell us if the solution is in an acidic or basic environment.

Max Madrzyk Dis 4G

The charge of Mn is 7+ because O has a charge of 2- and there are 4 of them making a total charge of 8-. We are then told that the overall charge of the molecule is 1- so we know that Mn must have a 7+ charge to get the total charge to equal 1-.

Max Madrzyk Dis 4G

Balancing the charge of a half reaction is the last step so once you have everything but the charge balanced you should sum up both sides and then add electrons to the side of the reaction that has the more positive charge.

Max Madrzyk Dis 4G

You would just use H+ for acidic conditions.

Max Madrzyk Dis 4G

A reaction will be spontaneous if the Gibbs free energy value is negative. So to find that point you would set the equation to zero to solve and then say that all values less that the one you find will make the reaction spontaneous.

Max Madrzyk Dis 4G

The electrons flow from the negatively charged anode to the positively charged cathode. So, overtime it makes sense that the electrodes would stop flowing because there would no longer be a difference in charge attracting electrons to either of the sides. Thats why the salt bridge is there, so that ...

Max Madrzyk Dis 4G

You would use the standard enthalpy of formation values when the question is asking for the standard enthalpy. If the question is not asking for standard enthalpy there will usually be other values given so that you can calculate the standard enthalpy in a different method.

Max Madrzyk Dis 4G

The Anode must be negative because electrons from the anode flow to the cathode and for this to continue to happen the anode must remain negative. This is made possible from the salt bridge that allows the charge difference to remain constant.

Max Madrzyk Dis 4G

I am pretty sure you don't flip the sign because it is already accounted for in the equation. I'm not positive though and I know he went over two different ways to get the same answer and the sign was changed in one of the ways but not the other.

Max Madrzyk Dis 4G

if you have a system that work is done on then the work of the system will be positive, if you have a system and work is done by it then work of the system will be negative. I think of it as the system is using energy to do some work on the outside so it is losing that energy.

Max Madrzyk Dis 4G

298 K is 25 C which is room temperature and not standard temperature.

Max Madrzyk Dis 4G

Adiabatic means that there was no heat transfer so q=0

Max Madrzyk Dis 4G

Yeah! under quick links click your posts and it should give you a number on the right side at the top of the list.

Max Madrzyk Dis 4G

Isobaric means constant pressure and when you have a system at constant pressure you can say that delta h=q.

Max Madrzyk Dis 4G

Entropy cannot reach equilibrium because it is the disorder of an ever expanding universe which has an increasing disorder so it will never reach equilibrium I think.

Max Madrzyk Dis 4G

In an open system both matter and energy can be transferred between the system and the surroundings.

Max Madrzyk Dis 4G

You can usually assume constant pressure because usually reactions arn't moved to different pressures throughout the course of the reaction. for example a chemist starting a reaction at sea level will probably let the reaction finish at sea level. This is true for most reactions with engines being a...

Max Madrzyk Dis 4G

Usually in a combustion reaction heat is released meaning that delta H will be negative.

Max Madrzyk Dis 4G

When the work is negative that means that work was done by the system but when work is positive that means that the work was done on the system.

Max Madrzyk Dis 4G

You have the right equation but you need to figure out what delta V is. To do that use delta V= -pi*r^2*d, then plug it into the equation you have and use the pressure given.

Max Madrzyk Dis 4G

work= -Pext x delta V
delta V= -pi x r^2 x d
use delta V and the pressure given in atm multiploied by the conversion to joules to find the amount of work done.

Max Madrzyk Dis 4G

The standard state of a substance is the state that the substance is at under the conditions of 1 atmosphere of pressure and 25 degrees celsius.

Max Madrzyk Dis 4G

We can observe the changes within the isolated system, but an isolated system will have no effect on the outside world.

Max Madrzyk Dis 4G

I think the conversion from celsius to kelvin is 0 C= 273.15 K, and remembering this is easy but I am also pretty sure it will be provided on the equation sheet on the exam.

Max Madrzyk Dis 4G

I think the SI units for the standard enthalpy of formation is Kj/mol.

Max Madrzyk Dis 4G

Great question! I too was confused by this in lecture.

Max Madrzyk Dis 4G

The first midterm will include everything that we have learned before it, including the things that were on test one. That is at least the way that the midterm for chem 14a with Dr. Lavelle was.

Max Madrzyk Dis 4G

We don't include H2O (l) in our calculations of Ka and Kb because water is going to be present in so much excess in both the reactants and the products that if we plugged it into the equation the two numbers would just cancel each other out.

Max Madrzyk Dis 4G

If the reaction needs heat to be work then you can think of heat being considered as a reactant and therefore the reaction is endothermic because the products are using the heat to form. If the reaction produces heat then you can think of heat as a product and therefore it would an exothermic reacti...

Max Madrzyk Dis 4G

We subtract the enthalpy of the products from the reactants when we are calculating enthalpy using bond strengths because forming a bond in the products has a negative enthalpy while breaking one in the reactants has a positive enthalpy.

Max Madrzyk Dis 4G

Yes, temperature is the only factor that will change the K equilibrium.

Max Madrzyk Dis 4G

Both units have to deal with pressure so I think the only thing that matters is that you stay consistent throughout the problem that you are working.

Max Madrzyk Dis 4G

Kw is a constant and I believe and it is the equilibrium constant for water and it equals 1.0x10^-14.

Max Madrzyk Dis 4G

I think Kc can be used with both but I think usually the problem will specify whether to find Kc or Kp. :)

Max Madrzyk Dis 4G

I think the chances that you would get two positive values after using the quadratic equation are pretty low but if you do I would plug them back into the ICE table and see which value is more reasonable.

Max Madrzyk Dis 4G

The equilibrium constant does not have units because they cancel out when you are calculating it.

Max Madrzyk Dis 4G

Solids and liquids are not included because their concentrations stay the same throughout the reaction so there is no need to calculate the change.

Max Madrzyk Dis 4G

The first homework assignment is due in lecture Friday.

Max Madrzyk Dis 4G

The first homework assignment is due in lecture Friday.

Max Madrzyk Dis 4G

Yes, you would use H2O because you include all gases in the equation.

Max Madrzyk Dis 4G

K is the equilibrium constant and is used when the reaction is in equilibrium, Q is the reaction quotient and can be used whether or not the reaction is in equilibrium.

Max Madrzyk Dis 4G

I think that you should probably know the names of common ligands like CN, NH3, PSO4 and such.

Max Madrzyk Dis 4G

A lewis definition of a base is a proton donor so N, having a lone pair is likely to give that pair away therefore making it a base.

Max Madrzyk Dis 4G

Polydentate describes how many bonding sites a ligand can have to a transition metal.

Max Madrzyk Dis 4G

C6H6 is probably neither an acid or base because it is stable and nonpolar.

Max Madrzyk Dis 4G

Im pretty sure CaO is a strong base because it completely dissociates.

Max Madrzyk Dis 4G

I think strong acids and bases generally contain elements from groups 1 and 2 on the periodic table.

Max Madrzyk Dis 4G

I think they're are like 7 strong acids and 8 strong bases so if you memorize those then you should be fine.

Max Madrzyk Dis 4G

it is cumulative and I expect he will tell us more in the upcoming classes.

Max Madrzyk Dis 4G

it represents the charge of the element you are dealing with.

Max Madrzyk Dis 4G

yes, water can either act as an acid or base depending on what it is reacting with.

Max Madrzyk Dis 4G

Seesaw shape only has >90 and >120 bond angles.

Max Madrzyk Dis 4G

I believe so, I'm sure Dr. Lavelle will email if there isn't though.

Max Madrzyk Dis 4G

No, test 2 goes up to sigma and pi binds only.

Max Madrzyk Dis 4G

Based off the common vsper charts that I have viewed I would say no but it never hurts to know anyway!

Max Madrzyk Dis 4G

Pi bonds are rigid because of their orientation around the axis being across it rather that along it therefore not allowing for the movement observed in sigma bonds.

Max Madrzyk Dis 4G

Yes, it has to do with lone pairs and polarity, so if these charges are present they will repel other elements and cause the bent shape that is observed in water rather than the linear shape present in co2 when there are 2 lone pairs that repel the other elements equally.

Max Madrzyk Dis 4G

The test will cover all the material from the midterm to lecture on Friday including one slide that will be in tomorrows lecture.

Max Madrzyk Dis 4G

Hybridization occurs because electrons and are always moving around the central atom and so are the elements that are bonded so any molecule could be in any of its possible shapes at any given time.

Max Madrzyk Dis 4G

according to the syllabus it is worth 50.

Max Madrzyk Dis 4G

Lone pairs help when determining the general shape but when it comes to molecular shape lone Pairs only influence the shape through repulsion and therefore only bonded atoms effect shape.

Max Madrzyk Dis 4G

No formal charges help find the most stable structure of the compound but don't really tell you anything about resonance.

Max Madrzyk Dis 4G

The higher the viscosity the smoother the liquid flows so like honey would have lower viscosity than water.

Max Madrzyk Dis 4G

Yes, you always want the most formal charges to be zero in any way that is possible.

Max Madrzyk Dis 4G

I think it would be helpful for understanding if you knew how to draw the orbitals.

Max Madrzyk Dis 4G

The shape matters with bond strength because the smaller a bond is between two elements the stronger it will be because the effective charge is stronger.

Max Madrzyk Dis 4G

Yes, Lavelle talked about dipole moments before he said that was the end of the information that was to be present on the test.

Max Madrzyk Dis 4G

Yes, theoretically the amount found in grams should be the same amount present in the products because of the law of conservation of mass.

Max Madrzyk Dis 4G

Yes, I think the most stable form of an electron is when it has no charge so you will always try and recreate that state for the element or get as close as possible.

Max Madrzyk Dis 4G

When drawing a lewis structure I think the goal is to have the most elements with a formal charge of zero rather than trying to make the formal charge of the central element zero.

Max Madrzyk Dis 4G

Isoelectronic means that different ion combinations of the elements have the same number of electrons and therefore the same configuration.

Max Madrzyk Dis 4G

I doubt that we need to angle the elements perfectly, I think the main thing is just that you have the configuration with the electrons right.

Max Madrzyk Dis 4G

I think this unbalanced slanted structure is due to the fact that some elements have a higher binding affinity to electrons and pull them closer to their nucleus, creating partial charges that still repel other elements a little bit so that the structure is not perfect.

Max Madrzyk Dis 4G

Resonance is basically when there are multiple right lewis configurations to describe a molecule and that not every molecule is going to be fixed in one of the states so resonance is the ability for the correct model for to exist in multiple ways and the molecule can be expected to be in any one of ...

Max Madrzyk Dis 4G

Yeah you would remove the electron from the farthest orbital because it is the farthest distance from the positively charged nucleus and therefore is easiest to remove.

Max Madrzyk Dis 4G

Valence electrons for the non metals can basically be counted just by going across the periodic table, for example; Li:1, Be:2, B:3, C:4, N:5, O:6, F:7, and Ne:8. And that pattern follows down the columns.

Max Madrzyk Dis 4G

The quantum number Z represents the angular component to the momentum of the orbital.

Max Madrzyk Dis 4G

It tells us that the electron cannot be bound to the center of an atom.

Max Madrzyk Dis 4G

I think those experiments stand for more of a conceptual understanding of why the calculations that we are doing work.

Max Madrzyk Dis 4G

The Pauli Exclusion Principle states that no one orbital can have more than 2 electrons and that those two electrons cannot have the same quantum number.

Max Madrzyk Dis 4G

The negative sign in the Bohr equation is there because it represents the energy the electron must overcome so when the electron and neutron are completely separated, the energy will equal 0.

Max Madrzyk Dis 4G

The T stands for tons.

Max Madrzyk Dis 4G

Under quick links there is a post that shows your posts so if you have 5 for the week I think you should be good.

Max Madrzyk Dis 4G

Yes because the intensity of the light on changes the amplitude of the waves but does not give it enough energy to eject electrons.

Max Madrzyk Dis 4G

Yes, I think that we get an equation sheet for every test.

Max Madrzyk Dis 4G

I think the only way to make balancing chemical equations easier is to balance the element that you have the least of first and see how that upsets the balance of other elements and slowly just keep working until the while equation is balanced.

Max Madrzyk Dis 4G

you should be as accurate as possible when doing you calculations and then round at the very end to accommodate for sig figs.

Max Madrzyk Dis 4G

No, you should only round for sig figs the you have your final answer.

Max Madrzyk Dis 4G

Yes, a combustion reaction always results in products of H2O and CO2.

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