CHEMISTRY COMMUNITY

Silvino Jimenez 1A

Is there a way to approach this problem conceptually and going around using differential equations? Lavelle actually posted this years ago but hopefully it helps (: G is actually defined as the maximum non-expansion work under constant T and P. Non-expansion means not related to a volume change, for...

Silvino Jimenez 1A

Delta G (dagger) is a way to distinguish the amount of free energy available to do work at the pseudo equilibrium of a TRANSITION STATE/INTERMEDIATE STEP

This value is different to the delta G (or free energy available) of the overall reaction.

I hope this helps (:

Silvino Jimenez 1A

We know that a negative delta G implies spontaneity but does the correlation where delta G equal max work only apply for standard conditions?

Silvino Jimenez 1A

When given a graph interpretation of a reaction, why does activation energy sometimes change in multi step chemical reaction?

Silvino Jimenez 1A

What is a leaving group?
For substitution reactions, I thought we only replaced the intermediates

Silvino Jimenez 1A

A poikilotherm is an animal whose internal temperature varies considerably. -Wikipedia Since temperature is one of the parameters that affects rate constant/law(s) an animal with the ability to vary their internal temperature means they have the ability to change the rate of the reaction mechanisms ...

Silvino Jimenez 1A

What is the question? (:

Silvino Jimenez 1A

If "the new pathway has a different pre-exponential factor"

then yes

A is a different value.

The problem usually directs what pre-exponential factor to use when solving, say for, rate law/constant.

Silvino Jimenez 1A

The reducing agent has the ability to oxidize.

Highest oxidizing power is determined by reducing agent.

Silvino Jimenez 1A

when identifying aldehyde

do you include both carbons or just the carbon bonded to the OH?

Thanks

Silvino Jimenez 1A

When determining the Rate Law of a multiple step Reaction, what is the best way to determine which is the slow step? How do you find out if the step before it is in equilibrium, does the problem have to state it or does it have to do with A Big K value of [P]/[R] ?

Silvino Jimenez 1A

Looking at an example problem: we are told we take out lab equipment to make galvanic cell which includes battery set up and 200ml of .008M CrCl3 200ml of .12M CuSO4 Copper wire Chrome platted wire How do we approach the problem to find which to use as the anode and which to use as the cathode. Do w...

Silvino Jimenez 1A

How do we determine when a reactant is an intermediate?

Silvino Jimenez 1A

Useful equation to predict the value of a rate constant at one temperature from its value at another temperature!

Silvino Jimenez 1A

From the problems I have worked on in the book, we are typically instructed which compound to use as the intermediate. Sidenote: I don't think this will be included in test 3.

Silvino Jimenez 1A

Will the problem typically tell us which step in the mechanism is the slow step? Are there clues in wording to look for that hint which step in mechanism is the slow step?

Silvino Jimenez 1A

I believe they made a very generous estimation and rounded the increase in rate between experiments 2 and 3. The change in [B] increased from 1.25 to 3.02 which is approx an increase of a multiple of 2. The change in the concentration is approx. an increase of a multiple of 3. Here is where I was co...

Silvino Jimenez 1A

Is it necessary to convert the units of a rate to metric units of time, seconds, when doing rate calculations in (mols/Ls)?

Silvino Jimenez 1A

What are some of the ways that the concentration of a reactant affects the rate of the reaction ?

Silvino Jimenez 1A

Bimolecular elementary reactions are second order reactions!

Silvino Jimenez 1A

Does this mean that both of the graphs ( Zero-order and First-order reactions) would be straight straight lines but that the only difference would be the labeling of the y-axis. [A] for Zero-Order and ln[A] on the y-axis of First Order reaction graph.

What exactly are the different axis implying?

Silvino Jimenez 1A

Any are okay to use, some may be easier to use than others especially if there are constants!

Silvino Jimenez 1A

The slow reaction determines the overall reaction rate.

Silvino Jimenez 1A

I believe there will be cases when both will be needed to solve problems
The first step of a problem could ask for us to use regular rate laws and given concentrations and a rate and to calculate k.

This k would be used with integrated rate laws to find the change in concentrations over time.

Silvino Jimenez 1A

To gain a better understanding of the concept behind half life, I am trying to get a sense of how the equations were derived.

Can anyone point me in the right direction to find the derivation of the half-life for zero order reaction

Zero order reaction: half-life= [A]o/2k

Silvino Jimenez 1A

Can Rate Constant of a reaction be determined by solely given order of the reaction and initial concentration of reactant(s)?

Silvino Jimenez 1A

if reaction rate ia to be found in a reaction with more than one reactant, than we must pay attention to what reactant the problem wants us to find the rate is respect of. If Initial rate of reactant given is not the reactant of interest than we must convert it in terms of the consumption of the oth...

Silvino Jimenez 1A

I am having a hard time identifying the order of a reaction given half life reaction time t1/2.

Are there key words or phrases that indicate a reaction is first order when determining half life reaction time?

Silvino Jimenez 1A

The half life of any reaction is the amount of time it takes to consume half of the initial material. For a second-order reaction, the half-life is inversely related to the initial concentration of the reactant (A). For a second-order reaction each half-life is twice as long as the life span of the ...

Silvino Jimenez 1A

The answer I'm getting is approx:

40.2 C for initial Temp. of Cu

This makes sense b/c in order for the water to increase temp, it had to transfer from a hotter object (2nd Law of Thermo)

Silvino Jimenez 1A

Yes, when a system does work, work leaves the system -- resulting in a net loss of work from the "perspective of the system."

Silvino Jimenez 1A

To answer the latest question: "If w decreases, will the internal energy increases or decreases" It depends if w is positive or negative - if the work done on the system decreases (+w) The change in internal energy of the system (deltaU) decreases Or - if the work done by the system decrea...

Silvino Jimenez 1A

The amount of an acid does not effect strength/ pH,

the concentration of H3O+

that an acid produces
when deprotanized

is directly related to the strength

Silvino Jimenez 1A

If you notice the units on the y-axis of graph are in

kPa

We calculate equilibrium constants in

atm (atmospheres)

I am assuming a unit conversion was made when dividing by 100 since

1 atm = 101.3 kPa ~ 100 kPa

:)

Silvino Jimenez 1A

(A) The H+ in lactic acid can interact w HbO2- to produce HHb and release oxygen, which means concentartion of HbO2- will be lower in the tissue

(B) Since more Hb- will return to the lung, more oxygen will be bound to Hb-, to produce HbO2- which will increase the concentartion of HbO2-

Silvino Jimenez 1A

Atoms that include the 3d orbital can have expanded octets.

The Xe in XeF4 breaks the octet rule and can have expanded octet since Xe includes 3d orbital

Hope this helps!

Silvino Jimenez 1A

Find the concentration of [H3O+] to determine strength or ph of any acid:

pH = - log ([H3O+])

We will be provided w an equilibrium constant Ka to determine whether given amounts of acid are in equilibrium.

Silvino Jimenez 1A

Water has no effect on the reaction of aqueous solutions since they are in fact surrounded by water.

Adding water allows us to visually see the protonation or deprotonation of an acid or a base:

Base + H2O <---> OH- + conjugate acid
Acid + H2O <---> H3O+ + conjugate base

Silvino Jimenez 1A

In order to find oxidation number you must pay attention to the following: - Overall charge of the ion - The number of ligands and each ligand's charge - Number of metal atoms The oxidation number of the Iron (Fe) in the picture below is 3+. I determined the oxidation number by paying attention to t...

Silvino Jimenez 1A

In a Homogeneous Reaction is one that includes only one phase - i.e. if all the products and reactants are in the gas phase, then the reaction is homogeneous

Silvino Jimenez 1A

The way I like to remeber it is that, Empirical formulas Are based on real experimental results For example the equation that gives us the change in energy levels of electrons in hydrogen atoms: -hR/(n^2) Was derived by observing and finding a relationship between the changes in energy of these elec...

Silvino Jimenez 1A

When in comes to coordination compounds: the dotted lines represent denticity, sites where the ligand can bind to the transitional metal If a ligand shows two dotted lines extending from it, this indicates that the ligand is a bidentate Usually these dotted lines extend from N and O because of their...

Silvino Jimenez 1A

Protonation tells how much of a given base has had protons added to reach equilibrium. The x value we determine at the end of ICE tables is the amount of product or reactant that has had protons added [Base]+H2O <--> [BaseH^+]+[OH^-] I can def see this show up on the test. This has to do w Acids and...

Silvino Jimenez 1A

The reaction quotient Qc is the ratio between the [P] and [R] at their current/provided values. Here you are given number of moles. In order to determine concentration from number of moles: Divide number of moles / by volume (L) Use these molarities as your concentartion amounts to determine Qc by p...

Silvino Jimenez 1A

SiO2 is Polar because the dipole moments do not cancel each other. If the dipole momements cancel it is non-polar.

Silvino Jimenez 1A

I believe resonance indicates delocalization.

If a structure like

a benzene ring (C6H6)

shows resonance in the double bonds,

meaning the double bonds can be drawn in an alternating pattern without effecting overall charge

then the structure also shows delocalized bonding !

Silvino Jimenez 1A

Value of R is the Gas Constant

Silvino Jimenez 1A

If the formal charge is the same in two Lewis Structures how do you determine which is more stable? I have attached an image of two Lewis Structures for NCO^- The solution I am provided states that the structure with the triple bond is the most stable. Although they cancel, this structure shows form...

Silvino Jimenez 1A

Hi

Would you expect Ka (Acidity Constant) of

[Fe(H20)6]^2+

to be bigger or smaller than

[Fe(H20)6]^3+

?

I understand that the iron cation w 3+ has a higher positive charge. What does that tell us about Ka?

Ty!

Silvino Jimenez 1A

Hi

How can pH or pOH be found
given % protonation/deprotanation and molarity?

Ty!

Silvino Jimenez 1A

Hi,

If an increases in temperature increases the value of equilibrium constant K, does that mean the reaction is exothermic/endothermic?

My understanding is that it takes in more heat. Then not sure how to determine reaction type (endo/exothermic).

Ty!

Silvino Jimenez 1A

How do we know when to use "di-" , "tri-" etc. as the prefix of a ligand compared to "bis-" , "tris-", etc. ?

ty!

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