CHEMISTRY COMMUNITY

Jasmine Chow 1F

I have asked some of the TA's and UA's this question and they said he has begun to stray away from asking for a straight up derivation but I would not totally cancel it out as a possible conceptual problem for the final. Honestly its not too hard to memorize the steps as there is a pattern you can f...

Jasmine Chow 1F

I believe you would use this equation to solve for the K rate coefficient. This will be used to see the effects of temperature dependence for reaction rates.

Jasmine Chow 1F

All the graphs will be linear however, the K sign for the slope will be different. Zero and first order graphs will have a negative slope while a second order graph will have a positive K slope.

Jasmine Chow 1F

A acidic solution had a greater abundance of hydrogen ions making the solution acidic while a basic solution will have a greater abundance of hydroxyl (OH-).

Jasmine Chow 1F

for a acidic solution you should begin by balancing the non hydrogen and oxygen elements. Once you have done this you should balance the oxygen by adding H2O to the side that is lacking oxygen. Then you would add H+ to the other side to balance the number of hydrogen molecules.

Jasmine Chow 1F

If there are no solid metals in the reaction then you would ad Pt (solid) as the reaction needs a solid metal to work therefore Pt (solid) or C(Gr) are often used to replace these needed elements.

Jasmine Chow 1F

Once the redox reaction is balanced you should have an equal number of electrons on both sides of the equation. That will be the n value. There can only be one value for n. If you think you have two then you did not balance your redox equations correctly.

Jasmine Chow 1F

On the side with no solid metal on it. The platinum will be used to replace the missing solid metal needed for the reaction to proceed.

Jasmine Chow 1F

After the excess H2O molecules are canceled out the H20 molecules must stay on the same side the excess was originally on. It can not be moved to the other side of the reaction.

Jasmine Chow 1F

Gabs free energy is the same thing as the amount of work a system can do. Therefore when gabs free energy us negative it is spontaneous as the system is doing work.

Jasmine Chow 1F

Not all isothermal reactions are reversible but if a reaction is said to be reversible it is usually isothermal. because there is no temperature change delta U is equal to zero according to the equation U= 3/2nRdeltaT.

Jasmine Chow 1F

yes you can assume that q is equal to zero. In this type of reaction, say a piston, the piston moves so quickly it does not allow an exchange of heat with the surroundings therefore there is no heat for an adiabatic system.

Jasmine Chow 1F

reversible expansion will allow you to use the isothermal equation w= nrtln(delta V) while reversible isothermal can only use W=-pdeltaV.

Jasmine Chow 1F

for a isobaric equation to find work you will want to use W= -p delta V.

Jasmine Chow 1F

Usually for isothermal delta U is zero. This is because if the equation from the first law of thermodynamics. 3/2nRT, when T equal zero delta U will be zero.

Jasmine Chow 1F

Enthalpy is kJ/ mol

Jasmine Chow 1F

I believe you should memorize it as it will help with bomb Calorimeter problems and other problems with various phase changes. Even if the curve is given I believe it would be helpful to memorize it anyways. It will save you time on the exam.

Jasmine Chow 1F

Yes you can have negative work on a system. An example of this would be the system doing work on its surroundings. Increasing the volume does count as negative work by the system.

Jasmine Chow 1F

An open system, like a cup of water, can exchange matter and energy with the environment. A closed system, like a closed water bottle, can only exchange energy. A isolated system like a sealed thermos can exchange neither.

Jasmine Chow 1F

It takes more energy; in the form of heat; to go from water to steam than it does to go from water to boiling water. Since it takes more energy to go through that phase change you would get a worse burn.

Jasmine Chow 1F

It depends on what the problem specifies. If it does not ask I usually keep the answer in the units the problem gave the values as.

Jasmine Chow 1F

you can use the 5% rule for a K value that is less than 10^-3 for acids and bases or equilibrium concentrations and pressures.

Jasmine Chow 1F

you will want to use the formula PV=nRT. if you just move the V to the other side you get P=nRT/v. But n/v is just concentration. So you replace n/v with your concentration for kc then you plug in your T and R constant to get P.

Jasmine Chow 1F

What is the unit for pressure concentration used in Chem? Is it still molarity?

Jasmine Chow 1F

Inert gases will not react with a reaction therefore it is not considered when calculating the equilibrium constant equation as nothing is changing for that gas and it is also not changing anything.

Jasmine Chow 1F

Temperature is the only modification that can affect the K value. Pressure, volume, and concentration does not affect the K value but it does affect which side of the reaction is favored more.

Jasmine Chow 1F

The Q is the same thing as the K value however it is the constant when the reaction is not in equilibrium. So you often compare K and Q to see which side of the reaction is favored when it is not in equilibrium.

Jasmine Chow 1F

I don't think we will be using it. He hasn't mentioned it in lecture yet.

Jasmine Chow 1F

yes it is in Kelvin. If you need to convert to K from C add 273.

Jasmine Chow 1F

There is no difference.

Jasmine Chow 1F

I would suggest waiting until the very end to round to the nearest sig fig. That way you still get the most accurate answer.

Jasmine Chow 1F

You should first convert all your elements into moles. you then divide by the smallest mole value to get your empirical equation values. Last multiply if needed to get whole numbers.

Jasmine Chow 1F

Cl will always have a negative 1- charge. So say you have something that says Cl2 then the overall charge will be 2-. In the case of [Fe Cl(OH2)5]^+ you will find the oxidation number of Fe. So Oh2 is a neutral ligand therefore there is no charge from this molecule. Since Cl is the only component th...

Jasmine Chow 1F

Intermolecular forces are weaker than intramolecular forces. Therefore it would be easier to break the bond between atoms that make up a molecule than to separate molecules. Intramolecular forces also consist of weak forces such as London dispersion and Van der Waals.

Jasmine Chow 1F

A delocalized pi bond is when electrons can freely move more that two nuclei. You will often see this in a lewis structure in carbon rings. Carbon rings often consist of double bonds. These pi bonds that are spread out over the lewis structure means the pi bonds are delocalized as they do not reside...

Jasmine Chow 1F

Thank you so much Dr. Lavelle for all the you do. Your lectures and all your resources have helped me do well and keep up with the class.

Jasmine Chow 1F

There is resonance therefore, you take the average of the two.

Jasmine Chow 1F

If you click on your account it should show you your post. Also if you had replied to someone there is a section that shows you how many times you have posted. If you click that it will should you all of your posts.

Jasmine Chow 1F

Thank you Dr. Lavelle for always keeping the class engaging. I also enjoy the fact that you have been using models in class to explain the molecular structure! Looking forward to your 14b lectures next quarter!

Jasmine Chow 1F

Electronegativity will increase upward and to the right of the periodic table. Some exceptions include noble gases, lanthanides, and actinides.

Jasmine Chow 1F

The formal charge is the best way to ensure your lewis structure is in the most stable state and to find its molecular shape via VSPER. Some ions may throw people off so formal charges are the best way to check your work.

Jasmine Chow 1F

I am currently trying to memorize all the VSPER models from the chart from the text book. What would be the best way to memorize all the information about the angles and what shapes belong with what?

Jasmine Chow 1F

A radical has lone pairs. Usually a single electron for example the element NH4+.

Jasmine Chow 1F

I usually check to see if a double bond is needed through the formal charges or through the pairs. If there is an odd number and there is a single lone electron I usually find a way to make it a double bond. Formal charges are the best way to check if another bond is needed.

Jasmine Chow 1F

Once I see every element has its respective electrons and all the needed bond have been inserted I use the formal charge to solidify the lewis structure is in its most stable form. Its a great way to check your work.

Jasmine Chow 1F

Electron affinity represents the energy spent or released when an electron is added to a gaseous molecule to create an ion. An example of this is the electron affinity of chlorine (-349 kJ mol-1) the negative sign represents a release in energy. Electronegativity is the tendency of atoms to attract ...

Jasmine Chow 1F

x,y, and z represent the different sections of an orbital each pair of elections can fill. These are just ways to distinguish between the different positions within the orbital.

Jasmine Chow 1F

You would only need to put [Xe] for the shorthand way as it is the closest Nobel gas.

Jasmine Chow 1F

You can just leave it in Joules.

Jasmine Chow 1F

The delta x in the equation is usually in meters and is often what is solved for or given. If it is in pm you would need to convert it to m so you can solve the problem.

Jasmine Chow 1F

The photoelectric effect is the emission of electrons caused by the threshold of the metal and the energy of the photon.

Jasmine Chow 1F

the Lyman series releases electrons to the n=1 level and is often associated with UV rays, while the Balmer series will release electrons to the n=2 energy level and is often associated with visible light.

Jasmine Chow 1F

yes! if the molecular formula can not be simplified it is the same as the molecular formula.

Jasmine Chow 1F

I have looked at a few sites and many have stated though the frequency and wavelength are inversely proportional to speed of light the wave length is often the indicator of what the color is.

Jasmine Chow 1F

Can the empirical and molecular formula be the same?

Jasmine Chow 1F

There really isn't a difference but I would get use to writing in scientific notation as Dr. Lavelle said scientific notation is often used is in the lab. there is no specific time to convert it to scientific notation. I would just automatically make it into scientific notation just in case. It is a...

Jasmine Chow 1F

When you are doing an exam should the final answer be in the lowest number or the highest number of sig figs from the problem?

Jasmine Chow 1F

Yes he said it is important to do during an exam and it is also good practice once you begin working in labs and doing research.

Jasmine Chow 1F

When I balance equations I like to write the number of elements on both sides so I can see everything visually.

B2O3+Mg ------> MgO+B

B:2 B:1
O:3 O:1
Mg:1 Mg:1

Then you can see where to balance everything out.

Jasmine Chow 1F

How do sig figs work?

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