CHEMISTRY COMMUNITY

Danny Elias Dis 1E

Another Quick Question: how do we determine the first order reaction/how is it correlated with y=mx+C For a first order reaction, you must look at the graph of ln[A] = -kt + ln[A]o. If this graph is a straight line with slope -k and y intercept ln[A]o, then you have a first order reaction. Typicall...

Danny Elias Dis 1E

Do catalysts always enter with the reactants of the first elementary step and end with the products in the last elementary step, or can it be the other way around?

Danny Elias Dis 1E

It is especially valid to substitute for k when you have a "bottle neck" effect. This means when the first elementary step of a reaction is fast but the second step is slow. When this happens, you must assume the first elementary reaction is at equilibrium and create an equilibrium constan...

Danny Elias Dis 1E

Is k only found experimentally (like order), or do we have to calculate k given reactant concentrations and a rate law?

Danny Elias Dis 1E

To add to the previous answer, if a reaction rate is not dependent on the concentration of a certain reactant, that means it is to the power 0. This, along with the fact that [A] and [B] can be to technically any power, means [A][B] is not necessarily second order.

Danny Elias Dis 1E

Look at it this way: if you were to graph the points without ln, the curve would be exponential. So, in order to make the graph linear, you must take the ln of the data. The ln is changing the curve into a line.

Danny Elias Dis 1E

Just to be sure, S on its own must always be positive, but deltaS can be positive or negative, right?

Danny Elias Dis 1E

It is important to keep in mind that n as the number of electrons only applies to the equation deltaG = -nFE, deltaG° = -nFE°, or Wmax = -nFE (these are the only equations from class). When using n in other equation such as the ideal gas law (PV = nRT), n is the number of moles.

Danny Elias Dis 1E

Van't Hoff is used when you are given two equilibrium constants and a temperature for one of them or, similarly, two temperatures and an equilibrium constant for one of them. From this information, you can calculate the missing value (which can be K1, K2, T1, or T2). Keep in mind, all of these value...

Danny Elias Dis 1E

Since deltaG can be measured in J as well as J/mol, is Gibbs free energy generally considered to be intensive or extensive?

Danny Elias Dis 1E

I believe the most common way to come up with Gibbs free energy is using the methods listed above. In other words, if there is a way to measure Gibbs free energy directly from an experiment, I don't think we need to know it.

Danny Elias Dis 1E

Can someone explain what is happening on a physical level when deltaG = 0 (the Gibbs free energy is at equilibrium)?

Danny Elias Dis 1E

Would individual organs in the human body be considered open, closed, or isolated systems? What about the human body as a whole? Just curious :)

Danny Elias Dis 1E

Can someone please explain the derivation of deltaS = nRlnV2/V1 ? I do not understand why this can be used.

Danny Elias Dis 1E

Is there an SI unit for the change in Gibbs free energy?

Danny Elias Dis 1E

Is this situation also the case where deltaU = q?

Danny Elias Dis 1E

While the conversion for units of pressure were not included on the last test, four different values for the gas constant (R) were provided: one includes joules, one includes atm, one includes bar, and one includes Torr. So, if your calculation involves the ideal gas law at all, chances are any pres...

Danny Elias Dis 1E

To add a chemistry example for spontaneity, imagine having one of those pumps Lavelle draws out. If the pressure inside the system is different from the pressure outside the system, the pump will move on its own to try to make the outside pressure equal to the system's pressure.

Danny Elias Dis 1E

If you are asking about calculating molar heat capacity at a constant pressure, use q = n(Cp)(deltaT), where n is the number of moles. Similarly, for a constant volume use Cv. Keep in mind that these can only be used for gases.

Danny Elias Dis 1E

Just to double check, when work is being done by the system the amount of energy is negative right? Similarly, is the energy positive when work is being done on the system?

Danny Elias Dis 1E

Is there a difference between the SI units of enthalpy and internal energy?

Danny Elias Dis 1E

What are the SI units for each of these (temperature, heat, and energy)?

Danny Elias Dis 1E

Simply put, steam transfers more energy to your skin than boiling water because of the excess energy the steam needs to release to turn back into a liquid.

Danny Elias Dis 1E

If we were to make a heating curve for some substance other than water, would the general shape of the curve resemble that of water?

Danny Elias Dis 1E

Just to clarify, are all polyprotic acids strong acids then? Since it is assumed the reactions go to completion?

Danny Elias Dis 1E

Can someone please explain how Le Chatelier's Principle applies to temperature changes when temperature changes affect K value?

Danny Elias Dis 1E

Also, you must keep in mind that we do not begin with any H3O+ or OH- in the solution. It starts out as 100% H2O. After that, as previously stated, note that H3O+ cannot be created without the formation of OH- in a pure water solution.

Danny Elias Dis 1E

Brackets are used when you are calculating Kc and parentheses are used when you are calculating Kp. You also need to include a P next to each reactant and product when calculating Kp to indicate you are using the partial pressures of each compound. Brackets indicate concentrations.

Danny Elias Dis 1E

To expand and clarify, Q and K are calculated the same way. The only difference is the value found for K will be the constant value at equilibrium. Using the same math, you can calculate the reaction quotient (Q) but for any point in the reaction (not necessarily when the reaction is at equilibrium).

Danny Elias Dis 1E

Why do we need to ever convert between Kc and Kp in a problem? In other words, what is converting between Kc and Kp used for?

Danny Elias Dis 1E

Is iron the only transition metal that can be transported using hemoglobin?

Danny Elias Dis 1E

Can the ligands that count towards coordination number be cations?

Danny Elias Dis 1E

What properties of cyanide makes it poisonous to humans?

Danny Elias Dis 1E

In a strong acid, nearly all molecules of the acid are depronated, and in a strong base, nearly all molecules of the base are pronated. Pronated means having accepted a proton, and depronated means having lost a proton.

Danny Elias Dis 1E

Are any carboxylic acids polyprotic?

Danny Elias Dis 1E

Can strength be measured by dissociation in a solvent other than water?

Danny Elias Dis 1E

Can someone please explain the labeling on the lone pairs of electrons? How does that work for the oxygen for example?

Danny Elias Dis 1E

Are degrees (used to describe bond angles) an SI unit?

Danny Elias Dis 1E

Also, along with the above answers, keep in mind that the lone pairs usually affect bond angles in the VSEPR model (even if it’s only by a little).

Danny Elias Dis 1E

How many lone pairs are possible when the molecule is in the trigonal planar shape?

Danny Elias Dis 1E

Also, molecules will be nonpolar if they are diatomic, whether they are VSEPR or not.

Danny Elias Dis 1E

Do the bond angles of the octahedral shape (90 degrees) ever change (because of things like electron pairs)?

Danny Elias Dis 1E

Why do larger atoms with some bond to another atom not follow the same rule as larger size atoms using VDW forces (with regards to attraction and strength)?

Danny Elias Dis 1E

Do Van Der Waals forces act differently in different physical states (solid vs. liquid vs. gas)?

Danny Elias Dis 1E

The subjects we went over in the 10 am lecture were:
1. Strengths and lengths of bonds.
2. Interactions between ions and molecules (the attractive forces such as ion-ion, ion-dipole, etc.).
3. Polarizability
4. Van der Waals forces/London dispersion forces.

Danny Elias Dis 1E

Is there any sort of calculation/equation where we will have to use specific values of bond length?

Danny Elias Dis 1E

I believe it does not matter. However, it will matter when we start focusing on the geometric structure of atoms rather than their formal charges.

Danny Elias Dis 1E

Do dipole moments have characteristics of ionic bonds too?

Danny Elias Dis 1E

No, there are exceptions. For example, a hydrogen atom has only 1 electron, therefore the maximum number of electrons it can have is two (to fill the orbital).

Danny Elias Dis 1E

Can every atom have potentially 8 electrons in the Lewis Structure besides H and He?

Danny Elias Dis 1E

Why is removing a second electron from an atom in the gaseous state harder than removing the first electron?

Danny Elias Dis 1E

Do we need to know the geometric shapes of the 5 d-orbitals, or just of the s and p - orbitals?

Danny Elias Dis 1E

Can "l" be any number less than "n-1," or must it be n-1?

Danny Elias Dis 1E

The five names for the d-orbital are dxy, dyz, dzx, dz^2, and dx2-y2.

Danny Elias Dis 1E

The equation you are asking about is the classical mechanics description of light. So in a general sense it is tied to quantum mechanics.

Danny Elias Dis 1E

Our issue is we cannot see what light is really made up of. However, it displays properties that compare to those of waves in some instances and photons (packets of energy) in others. The struggle comes when trying to decide when it acts like a wave and when it acts like a photon.

Danny Elias Dis 1E

While I do not know any other specific resources to help you with the topic, I do know forming study groups will work wonders for your understanding of the subject. Discussing what you don't understand with students who have a clearer understanding of the material can sometimes be better than findin...

Danny Elias Dis 1E

Must we always show our work when converting units in problems, or can it be assumed by the grader?

Danny Elias Dis 1E

What was the unit of measurement only used by chemists, also known as 10 to the -10 power?

Danny Elias Dis 1E

If we were to post four times in one week, would the extra post roll over to next week's grading?

Search found 60 matches