CHEMISTRY COMMUNITY

SalmaQ

Hello I think it would just depend on the concentrations/amount of reactions and products that you are dealing with. Also another important factor would be if the conditions of the reverse reaction are the same as the forward reaction i.e. temperature.

SalmaQ

When setting up your ICE box, if the initial concentration of either the products or reactants is equal to zero, then the change in molarity would be positive. If the initial change has any given number other than zero, the change is then negative. I hope this helps.

SalmaQ

Hello, the way that I go about it is that if the initial change is not zero, then the change in molar concentration would have to be negative. If the initial change is zero when setting up the ICE box, then the change in their molar concentrations would be positive.

SalmaQ

Hello, by changing the temperature, you are able to speed up or slow down a reaction. So this does in fact change the value of K.

SalmaQ

Hello! Yes you are correct. You can use the ICE table whenever it asks you to calculate the equilibrium composition. Also just like Hana said, is to keep the initial, change, and the equilibrium molar concentrations all together and organized.

SalmaQ

And yes to clarity both have the same ratio [Products]/[Reactants].

SalmaQ

Hello Lilly!
The time when we would use the reaction quotient (Q) would be any time during the reaction and like you stated, the K constant is used for when at an equilibrium! Hope this helps!

SalmaQ

FionaHunter21 wrote:So is R the same constant as the one we used before on the equation sheet?

Hey Fiona, the R constant would be gas constant which is 0.082057 L atm mol^-1 K^-1.

Hope this helps!

SalmaQ

when do you know you are allowed to use this formula? Hey Leslie, Just like Alexandra said, you can use this idea gas formula to convert from the concentration Kc to the partial pressure Kp, and vise versa. In order to do that, you would divide V (the volume) by both sides to isolate the P (or Kp);...

SalmaQ

Hello Emma, Looks like you are on the right track to solve this problem since you do not need to convert the initial values of Cl2 and BCl because the problem is asking for the concentrations (Kc). Now if you wanted to convert it to the partial pressure (Kp), then for that instance, you would need t...

SalmaQ

Hey Anya, I believe that you can use both the partial pressure (Kp) in the equilibrium or the concentration (Kc) to solve for an equation composed of all gases. If you end up starting the problem with the partial pressure (Kp) you can always use the ideal gas law of PV=nRT to convert/ solve for the ...

SalmaQ

I believe that if you are asked to use K to calculate the concentration of a species at equilibrium, and if the reaction is in a gas phase, we would need to use its partial pressure (Kp). After this, we can use PV=nRT, or once solved P=n/V(RT) ---> P=conc(RT) to covert Kp to find the concentration Kc.

SalmaQ

The difference is that during a reversible process, the system will always be at equilibrium with its surroundings. For an irreversible process, there will always be an entropy change.

SalmaQ

I would know them just in case, especially since Dr. Lavelle did go over them during lecture. In the textbook, these graphs are found on page 631 in Chapter 15.6.

SalmaQ

I'm pretty sure that we will only have to use SI units, therefore, only mol, L, and s. But then again, I am not 100% sure.

SalmaQ

The rate constant (k) depends on the temperate and activation energy.

SalmaQ

For the graph of the second order reaction:
1/[A] concentrations increase over time and [A] concentrations decrease over time.
If you were to graph this, you would end up getting a positive slope, since the y-axis of the graph is 1/[A].

Hope this made sense!

SalmaQ

Will we be talking about negative order, mixed order, or fractional order?

SalmaQ

I believe that you should use the log or ln stated for each version of the equation given just to avoid an error but to be truthful I'm not entirely sure if there is a difference.

SalmaQ

I'm not completely sure what you mean by "which equation to use?" Maybe like Cassidy said, it would be best to provide a specific example.

SalmaQ

A salt bridge is an inverted U-tube that contains an electrolyte and it connects the two half-cells in a galvanic cell. The importance of the salt bridge is to maintain electrical neutrality.

SalmaQ

The Gibbs energy is defined solely in terms of state functions, and so G is a state function. The temperature and pressure are constant, and with that we can already predict using Gibbs free energy the spontaneity of a process sole in terms of the properties of a system.

SalmaQ

If you go onto the class website for Chem 14b, there are a few outlines for what we should be learning from each chapter and also what homework problems we should do. Since we are still reviewing the first law and the second law of thermodynamics in lectures, I would do homework problems from both c...

SalmaQ

Reversible expansion is one that can be reversed by an infinitely small change in a variable. An example of this at work would be when a gas expands reversibly, the pressure on the outside is matched to the pressure of the gas during the expansion. This example could be directed in either direction,...

SalmaQ

Liquids have more energy and entropy than solids. When there is an increased number of gas molecules, there is also an increase in entropy.

SalmaQ

The number of possible states for a system of given energy is called the degeneracy and it is denoted by g in the equation S=k ln (g). So when there is an increase in the degeneracy the energy level is higher versus when the degeneracy decreases, the energy level is lower.

SalmaQ

In this case, the q would be negative because the enthalpy (the amount of heat released or absorbed at a constant pressure) in this question is being released. The enthalpy value is equivalent to q= delta H and if the reaction is exothermic (which it is in this question because it is giving off heat...

SalmaQ

And the common polydentates include:
1)Bidentate: C2O4^2- and ethylenediamine (H2NCH2CH2NH2)
2) Tridentate: Diethylenetriamine
3) Hexadentate: edta

SalmaQ

Common monodentates include: H20, CN-, SCN-, X-, NH3, NO2-, OH-.

SalmaQ

Remember that the equilibrium constant Kc is defined as Kc= [C]^c[D]^d/[A]^a[B]^b

SalmaQ

In the example of water, (H2o) there are two dipole moments, a partial positive with both hydrogen atoms and a partial negative dipole over the Oxygen atom. This configuration overall is considered non-polar even know there is a dipole moment.

SalmaQ

I think that the only time we have write out this fully is when we are asked to write out the full and complete (extended) electron configuration rather than just the ground state electron.

SalmaQ

If that is what is easiest for you. Just remember that in the answer, the n number should be in increasing order of energy levels. By doing this, it will be easier to write out the electron configurations for cations and anions.

SalmaQ

The easiest way for me to count valence electrons is to count the group numbers instead of the period numbers.

SalmaQ

I do not think that we have to know the VSEPR formulas or shapes for this midterm because that is mainly in chapter 4 and the midterm will cover the fundamentals and chapters 1-3.

SalmaQ

If the lewis dot structure happens to be a square planar shape, you can place one pair of lone pairs on either ends of the central atom (top and bottom) but if the VSEPR shape is for instance T-shaped, then you can place the pairs of lone pairs both on the top of the central atom but as far away fro...

SalmaQ

The least electronegative element tends to be the central atom when creating the lewis dot structures because they tend to be more stable this way. However, there is an exception with H2O because oxygen is more electronegative than hydrogen but in this case, oxygen is still the central atom.

SalmaQ

What is a resonance hybrid?

SalmaQ

Fluorine on the periodic table is the first element in that group and it is pretty far to the right so it does still follow the electronegativity trend of increasing across the periods and up a group.

SalmaQ

Atomic radius is half the distance between centers of neighboring atoms and ionic radius is two ions that are joined by an ionic bond.

SalmaQ

https://goo.gl/images/1Emecf

More reasons to love trader joe's....."Avogadro makes mole and avocados make guacamole."

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