CHEMISTRY COMMUNITY

Gillian Ward 1F

Use Cp when there is constant pressure and Cv when there is constant volume. The problem will specify if it is at constant pressure or volume.

Gillian Ward 1F

Since first order is ln[A]=-kt+ln[A]o it has a negative slope due to the -k.

Gillian Ward 1F

Bimolecularity refers to having two molecules colliding in a reaction.

Gillian Ward 1F

To have the greatest Wmax you want the greatest delta G

Gillian Ward 1F

Endergonic is a positive delta G while endothermic is a positive delta H

Gillian Ward 1F

The heating curve we were introduced to in class was one specific to water. All molecules have their own heating curves

Gillian Ward 1F

Intermediates are produced in one elementary step and consumed in the next. They are not part of the overall reaction so they will not appear in the rate law.

Gillian Ward 1F

Catalysts lower the activation so it will lower the curve of the reaction.

Gillian Ward 1F

Inert gases do not cause any shift in the system

Gillian Ward 1F

Unimolecular--1 reactant molecule
Bimolecular--2 reactant molecules
Termolecular--3 reactant molecules

Gillian Ward 1F

It does not matter which trial is used, they will all give you the correct value.

Gillian Ward 1F

Yes it would affect the molecules in the gas phase. More specifically, compression increases pressure which will cause the side with less moles to be favored.

Gillian Ward 1F

K and Kc are basically the same thing, except that Kc specifically means concentrations like Kp would refer to partial pressures.

Gillian Ward 1F

They do not need to be in standard conditions

Gillian Ward 1F

Work done on the system is positive while work done by the system is negative

Gillian Ward 1F

You exclude solids and liquids because they remain the same throughout the reaction

Gillian Ward 1F

Why does gas expansion in a reversible, isothermal process perform more work than irreversible?

Gillian Ward 1F

k is referring to the rate of the forward reaction while k' is referring to the rate of the reverse reaction

Gillian Ward 1F

Why for number ten is it that having a negative standard reaction potential mean that it will be non-spontaneous and therefore the coin will not dissolve?

Gillian Ward 1F

Possibly, it is in the curriculum.

Gillian Ward 1F

A tin electrode in 0.015M Sn(NO 3 ) 2 (aq) is connected to a hydrogen electrode in which the pressure of H 2 is 1.0 bar. If the cell potential is 0.061 V at 25 degrees Celsius, what is the pH of the electrolyte at the hydrogen electrode? How do you set up the cell equation with the given information...

Gillian Ward 1F

Are there any exceptions to this?

Gillian Ward 1F

In the solutions, they kept the partial pressures and concentrations in the calculations and proceeded to solve. Why are the concentrations not converted to partial pressures or vice versa so that all of the values are in the same form?

Gillian Ward 1F

When do we add Pt(s) to a cell diagram?

Gillian Ward 1F

How does the activation energies of reactions help determine if it is endothermic or exothermic? For example, in the 7th edition question 7D.7b asks if the reaction is endothermic or exothermic and the solution talks about the activation energies of the forward and reverse reaction.

Gillian Ward 1F

The rate constant of the reaction between CO 2 and OH - in aqueous solution to give the HCO 3 - ion is 1.5 x 10 10 L.mol -1 s -1 at 25 degrees Celsius. Determine the rate constant at human body temperature (37 degrees Celsius), given that the activation energy for the reaction is 38 kJ.mol -1 . In t...

Gillian Ward 1F

These are the scheduled Sunday sessions:
Ajith Raja 11am-1pm (Drop-In), Nathan Mallipeddi 1-3pm (Step-Up), Ryan Cerny 6-7pm (Drop-In), Karen Leung 7-9pm (Workshop), Ryan Cerny 9-10pm (Drop-In)

You can also find this information on Dr. Lavelle's website under "Important Midterm Information"

Gillian Ward 1F

If you search "hotdog" you'll be able to find his post.

Gillian Ward 1F

What is the difference between $q=mC\Delta T$ and $q=C\Delta T$ and in which situations would I use them?

Gillian Ward 1F

Looking at the equilibrium constants of each of the reactions at their respective temperatures, the equilibrium constant for the reaction at 700. K is smaller than the constant at 600. K. This tells us that the reactants are favored more in the higher temperature.

Gillian Ward 1F

Why do solutions of weak acids have higher pH values than solutions of strong acids at the
same concentration?

Gillian Ward 1F

Exceptions being in the 3rd period since they can expand into their d orbital

Gillian Ward 1F

When looking at boiling point, you want to examine intermolecular forces. Since NH3 is going to have stronger intermolecular forces (N--H is hydrogen bonding which is the strongest IMF) the boiling point will be greater.

Gillian Ward 1F

We need to know how to name coordination compounds

Gillian Ward 1F

In the drawing of a coordination compound, some of the compounds were written in reverse to show which atom in that compound interacted with the central atom. How do we know when a different atom interacts with the central atom and to write the compound in reverse?

Gillian Ward 1F

Coordination number corresponds to the number of bonded atoms around the central atom

Gillian Ward 1F

Because dissociation energy is an addition of energy to break a bond it is going to be positive.

Gillian Ward 1F

What does it mean to say that highly distorted electrons are described as being highly polarizable?

Gillian Ward 1F

I like to think about a molecules shape to determine if there is symmetry or not in the polar bonds. If so, the dipoles cancel out meaning there is no net dipole.

Gillian Ward 1F

VSEPR stands for "valence shell electron pair repulsion" and we probably do not need to have it memorized

Gillian Ward 1F

A molecule with AX3E2 VSEPR formula is going to have an electron geometry of trigonal bipyramidal (this takes into account the lone pairs) and a molecular geometry of a T-shape (this takes into account only the atoms, excluding the lone pairs).

Gillian Ward 1F

I don't think it is possible to find an exact figure for the bond angles that are, for instance, less than 120 or 109.5. There are only estimates or a range that it could be in.

Gillian Ward 1F

I believe the reason is that lone pairs occupy more space, in other words they are more diffused. This causes them to push the other atoms closer together.

Gillian Ward 1F

I talked to my TA about this and even though it isn't an SI unit Dr. Lavelle wants us to know the conversion.

Gillian Ward 1F

^ Yes, the stronger the bond the more energy it will take to break it resulting in a higher boiling point.

Gillian Ward 1F

Compounds with stronger intermolecular forces have higher boiling points because it takes more energy to break their bonds (the energy is given in the form of heat).

Gillian Ward 1F

Dr. Lavelle mentioned in lecture today that we do not need to know nomenclature yet.

Gillian Ward 1F

Atoms want to have 8 electrons in their valence shell, so they seek to either gain or loose electrons. Having 8 valence electrons gives that atom a noble gas configuration which makes them the most stable.

Gillian Ward 1F

It is a lewis base if it donates its electron pair, and it is a lewis acid if it accepts an electron pair.

Gillian Ward 1F

It will most likely be given, but it can be helpful to familiarize yourself with the spectrum to check if your answers are reasonable.

Gillian Ward 1F

I thought of it as 1/100 having one sig fig

Gillian Ward 1F

I believe it's going to be more concept heavy than last test, so having a really good understanding all of the topics is going to be important.

Gillian Ward 1F

In class, we used the baseball as an example based off of the De Broglie equation (wavelength = h/p where p=mv). This equation can be used for anything that has a distinct resting mass, as does a baseball. The baseball example in particular shows that as momentum increases wavelength decreases, and ...

Gillian Ward 1F

Energy and frequency and directly proportional, because when the frequency increases so does the energy.

Gillian Ward 1F

On Dr. Lavelle's website there is a link that has the equation sheet he puts on the front of his tests. It's under the course materials section with the title "Constants and Equations." Hope this helps!

Gillian Ward 1F

I believe it is a metric ton, so the conversion would be 1 t = 1000 kg.

Gillian Ward 1F

In part c you are starting with mg instead of mmol. In parts a and b you were able to just use 0.07967 M as a conversion factor because you already started with moles. Part c makes you convert to the mg to g to mol and then mol to L using M. To help me keep the conversions straight, I split this up ...

Gillian Ward 1F

I believe it is like doing percent composition without multiplying by 100 to get a percent. (percent composition is part mass/whole mass x 100) In this case, part mass/whole mass = fraction The amount of oxygen is (16.00 x 4), the 16.00 being the molar mass and the four comes from the number of mole...

Gillian Ward 1F

Yes, you use Avogadro's number :)

Gillian Ward 1F

After I divided the three values by the smallest, I found the subscript of Na to be 2.9548, Al to be 1, and F to be 5.910. Since they're very close to a whole number, I just rounded up and got the empirical formula of Na3AlF6. It would be more obvious if the values needed to be multiplied to somethi...

Gillian Ward 1F

How should you round the atomic weights of the elements on the periodic table when using it for calculations and how many decimal places should you go out to?

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