CHEMISTRY COMMUNITY

MadisonFuentes1G

I also have this question and am not sure of what concept is being applied

MadisonFuentes1G

There are three molecules of reactants involved in the rate law.

MadisonFuentes1G

I have seen some problems worked out where neither moles nor mass are included in the equation involving heat capacity (q=nC(deltaT)). Can someone explain why that is?

MadisonFuentes1G

I don’t think the professor ranked how common the first three orders were, just that they are the most common and that anything above a third order reaction became rarer and rarer.

MadisonFuentes1G

Molecularity depends on the number of reactants in a reaction (including the number of moles of a reactant).

MadisonFuentes1G

The rate laws for the different orders and their half lives are on the constants and equations sheet

MadisonFuentes1G

How do we know which experiments to use in order to figure out a reactants rate order? I thought it was by choosing experiments where one reactant concentration changes while the other don't, but that doesn't seem to be the case for finding [B] (the solutions uses exp. 2 and 3, where there is also a...

MadisonFuentes1G

For the reactions in this problem, are we supposed to work out the half-reactions in order to figure out how many moles we use in the equation to find standard G, or is there a faster way to find it?

MadisonFuentes1G

What does it mean for something to be a pure conductor?

MadisonFuentes1G

In part a, the cell diagram includes Pt(s) on only the right side of the reaction (for the cathode). Why wouldn’t it be included on both sides?

MadisonFuentes1G

When do we use commas in a cell diagram as opposed to using a straight line?

MadisonFuentes1G

I checked the Errors PDF as well, but I still have no idea how they got 4P4 by multiplying by 3.

MadisonFuentes1G

In 14.11 part b, the final balanced reaction reverses the half-reaction of Cl- to Cl2. First of all, why does the standard cell potential not become negative when it’s flipped, and why are we able to flip the half-reaction for the final reaction? Is it because it’s in order to get the electrons on d...

MadisonFuentes1G

For letter d) in problem 14.5 (6th edition), the answe key says to multiply the first half-reaction by 3, but then the new reaction contains 4P4, not 3P4.

Is this a mistake in the answer key or the actual answer? If it’s correct, could someone explain why?

MadisonFuentes1G

The constants and equations sheet show that there are a couple of ways to write out the units.

MadisonFuentes1G

I am also curious about this regarding temperatures with negative values.

MadisonFuentes1G

I was wondering what the difference between Gibbs Free Energy vs. Standard Gibbs Free Energy is.

MadisonFuentes1G

How is the ln derived in the Boltzmann equation?

MadisonFuentes1G

I am also confused with this. I think it may be reversible systems that do more work but I am not sure.

MadisonFuentes1G

Did the method we learned in lecture about finding bond enthalpies relate to Hess’s Law, or was that just a different method?

MadisonFuentes1G

Why do molecules occupy more states in a gaseous compared to being in solid or liquid states?

MadisonFuentes1G

IN the equation, deltaU=deltaH-PdeltaV, why is PdeltaV insignificant with solids and liquids when there is a constant Pressure?

MadisonFuentes1G

What is the natural log supposed to represent in the equation?

MadisonFuentes1G

The first is just the measure of any kind of change in enthalpy in a reaction.

The second represents Standard Reaction Enthalpy, which is when reactants and products are in their standard state at 1 atm.

MadisonFuentes1G

The quadratic formula will naturally end up being used in ICE tables typically when the unknown concentrations for the products in equilibrium are the same and the reactant at equ. has the initial conc. minus the change in conc. This is because, when the K equation is written out with these values, ...

MadisonFuentes1G

When a new gas is added to the system (not including inert gases), the chemical reaction goes out of equilibrium. According to Le Chatelier's Principle, the reaction will adjust itself in order to restore itself back to equilibrium (its K value) by either increasing or decreasing gas pressures on ea...

MadisonFuentes1G

I don't know what would be exactly on exams, but it could be possible because the only additional work you would have to do is multiply the x (representing change of concentrations of products) in your ICE table by the coefficient of whichever product has a coefficient that's not 1.

MadisonFuentes1G

For problem d, the information given provides K2, while the rest of the problems give the values for K1. What does this exactly mean, and does it require solving the problem differently?

MadisonFuentes1G

When identifying the Kb values of these molecules, why can we use the same values if the molecule is not exactly the same? For example, question 2 is not exactly the same molecule as the one whose pB we use to find the Kb value.

MadisonFuentes1G

The quadratic formula ends up being used most often when we use ICE tables. While we place the concentrations of the products over the concentrations of the reactants at equilibrium over each other, we do not know the change in concentration from their initial molarities. Ultimately, the quadratic f...

MadisonFuentes1G

For question b, the solution explains that the compressing the system would lead to no change to the equilibrium equation because the number of moles are equal on either side. However, it looks like there are 12 moles on the left side and 7 on the other. Can someone explain how they came to this con...

MadisonFuentes1G

The correct answer to Q 11.43 in the book is c) K=x^2/(1.0-2x)^2. I was wondering why this is the case. I understand why the numerator is x^2, and I understand that the denominator has to do with the difference in stoichiometric coefficients, but I do not understand why 1.0-2x is squared or why ther...

MadisonFuentes1G

Why do we divide the concentration by .250 in the pH calculation?

MadisonFuentes1G

What difference does it make if an acid is strong or weak when calculating its pH?

MadisonFuentes1G

When is a case where pi bonds would be delocalized?

MadisonFuentes1G

When determining the coordination number for compounds, I’ve heard two ways of figuring it out but am confused. Do we look at the number of nitrogen atoms or the most electronegative atoms?

MadisonFuentes1G

Study the VSEPR shapes that Dr. Lavelle taught in lecture, which can all be found in the beginning of Chapter 4.

MadisonFuentes1G

Study the VSEPR shapes that Dr. Lavelle taught in lecture, which can all be found in the beginning of Chapter 4.

MadisonFuentes1G

To have a pi bond present means that there is already a sigma bond present, thus making the bond strength much stronger. Additionally, pi bonds will bond side by side, so if the atoms rotate, then the pi bonds will be broken.

MadisonFuentes1G

It’s not the addition of orbitals but rather of a merging of the two. If you look at the amount of energy of the hybrized orbital, it will fall in between the two original ones. There is a conservation in the number of electrons for hybridization, it’s just their placement that changes.

MadisonFuentes1G

With all of the VSEPR names of the shapes that we have to memorize, does anyone have any ways of memorizing the number of the types and the names of the shapes we need to know?

MadisonFuentes1G

Use the formula M=n/L and manipulate the equation to where the number of moles equals the molarity times the volume.

MadisonFuentes1G

After determining formal charge, how do you identify the Lewis structure of lower energy?

MadisonFuentes1G

When would the VSEPR shape be trigonal planar as opposed to trigonal bipyramidal, and vice versa?

MadisonFuentes1G

Ms represents the direction and magnitude of an electron in an orbital. It is not a positive or negative value but rather something more like clockwise or counterclockwise rotation on an axis. Two electrons cannot spin in the same direction in an orbital, and this is why no two electrons will have t...

MadisonFuentes1G

Why do we only use the noble gas elements for core electrons and not others?

MadisonFuentes1G

You can also look at n—>infinity as a limit in calculus. We also know that the larger the number in the denominator, the smaller the answer becomes, and when the number in the denominator is getting nearer to infinity’s, the energy becomes so small that it eventually becomes negligible.

MadisonFuentes1G

Professor Lavelle teaches from the notes, and the book is used to supplement his lectures and give the homework problems. A lot of the time, the book will correspond with his lectures and notes, but not always. In those cases, it’s probably best to ask your TA or Lavelle himself to make sure, but lo...

MadisonFuentes1G

We know that the electrical field (as opposed to the magnetic field) corresponds to the amplitude of a wave. Because the frequency is decreasing, this means that there are less cycles being completed per second, meaning that the waves must be getting longer since it will take a longer duration of ti...

MadisonFuentes1G

Q 1.23 “The y-ray photons emitted by the nuclear decay of a technetium-99 atom used in radiopharmaceuticals have an energy of 140.511 keV. Calculate the wavelength of these y-rays.”

I‘m not sure how to begin this problem. What measurement is keV exactly, and how do you convert it to joules?

MadisonFuentes1G

In order to have the most precise and accurate answer, it is best to not round sig figs until the end once you have finished the problem. To figure out the number of sig figs you use, look at the number of sig figs used in the original problem.

MadisonFuentes1G

In order to convert the grams of KCl to m/L (Mi), you should first find the molar mass of KCl and divide the mass of KCl given (55.1 g) by its molar mass. This finds the number of KCl moles, and since M=n/V, you just divide the number of moles by the volume given (75 mL, or .075 L). This finds Mi (t...

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