CHEMISTRY COMMUNITY

Wenxin Fan 1J

Yes, you need to identify the slow step to see if it fits the experimentally observed rate law. However, you may not always be told which step is the slow step so you should try to see which step would work as the slow step if you apply what you know about the characteristics of a slow step and if y...

Wenxin Fan 1J

In most cases, catalysts will not be included in the rate law since it is not usually involved in the slow, rate determining step.

Wenxin Fan 1J

Integrated rate laws applies to reactions other than first order reactions as well. The ln[A] vs t, 1/[A] vs T are both from integrated rate laws.

Wenxin Fan 1J

To show the mechanism you just need to write and identify the slow step and ensure thsn the series of steps results in the overall equation and supports the experimentally determined rate law.

Wenxin Fan 1J

In problems where the experimental results are given, the k value calculated should be the same for each trial, but in actual experimentation the results will not be as accurate and precise so you would average them.

Wenxin Fan 1J

The coefficients are helpful when using elementary steps to try to determine the reaction mechanism, but the actual rate law can only be determined through experimentation.

Wenxin Fan 1J

The order of the reaction is the addition of the exponents in the rate law equation. The different orders help you to determine the rate of the reactions in reference to the consumption of reactants. The order is an important aspect in the rate law.

Wenxin Fan 1J

The primary difference is that the integrated rate law utilizes the initial rate and is a function of time.

Wenxin Fan 1J

Use reactants when dealing with reaction rate problems for this class.

Wenxin Fan 1J

You must use experimental data to calculate n and m. All the necessary information should be given to you so that you can ultimately calculate n and m.

Wenxin Fan 1J

They are the same. They are only written using different variables but they ultimately represent the same thing.

Wenxin Fan 1J

For right now the tangent line will be positive since we are primarily looking at forward reactions as reactants proceed to products.

Wenxin Fan 1J

That is one way to tell. You can look at the standard reduction potentials for the two half reactions to see what the sign of E˚ would be to determine if the reaction is spontaneous in one direction or the other.

Wenxin Fan 1J

Yeah, you aren't going to be required to memorize standard reduction potentials or other values found in the appendix.

Wenxin Fan 1J

Usually, the molecule/atom that has been reduced (gains electrons) is the oxidizing agent and the molecules that has been oxidized (loses electrons) is the reducing agent. This makes sense since redox-reactions involve an exchange of electrons between different atoms/compounds.

Wenxin Fan 1J

Yes, since entropy is a state function the two types of reactions would result in the same answer.

Wenxin Fan 1J

Use dimensional analysis to track your units and see which ones cancel out in your problem.

Wenxin Fan 1J

An oxidation equation is when an element has a lower oxidation number in the reactants compared to the products and/or when there are electrons in the products side of the equation. A reduction equation is when the electrons are found on the left side of the equation and/or when the oxidation number...

Wenxin Fan 1J

Molar entropy is the amount of entropy change resulting from the formation of one mol of its substance from its simplest/purest components. It can be calculated using the molar entropy values of other components in an equation. The more disordered a phase is the more entropy. Gasses have the most an...

Wenxin Fan 1J

Thermal motion and positional disorder are aspects of entropy that can be used to describe the amount of entropy or be used to compare the entropy that an object has.

Wenxin Fan 1J

Questions will normally specify if pressure has changed or if a reaction is not at standard conditions. That is when you would use that version of the gibbs free energy equation.

Wenxin Fan 1J

Systems can only be completely isolated in theory. Most "isolated" systems are more similar to closed systems in real life.

Wenxin Fan 1J

Work is the ability to move/push against an external force/pressure, which is why P external is used. In chemistry we view work from the point of view of the system.

Wenxin Fan 1J

It depends on the context of the problem but water is considered the surroundings if something is placed in the water. However, the amount of energy absorbed by a calorimeter can be used to calculate heat released to the surroundings as well.

Wenxin Fan 1J

Questions should specify but most combustion reactions where heat is calculated should occur in a bomb calorimeter.

Wenxin Fan 1J

More stable bonds have more negative (less) potential energies, which means more energy is required to break the bonds. Therefore bonds with greater potential energy (less negative) are less stable and require less energy to break.

Wenxin Fan 1J

When temperature changes for a substance use the equation q=mCdeltaT and when the desired or required temperature is met and the substance changes phase use the values for delta H of vaporization or melting to find the heat . Add all the values together

Wenxin Fan 1J

What do chemists call a benzene ring with iron atoms replacing the carbon atoms?

A ferrous wheel.

Wenxin Fan 1J

When the internal heat of the system decreases because work is done on the surroundings by the system (heat released), the molecules in the system has less kinetic energy, resulting in less movement and less pressure. Volume and pressure are inversely related if heat is not a factor.

Wenxin Fan 1J

Work done on the system results in a positive value for joules while work done by the system results in a loss of heat of the system (negative) and into the surroundings.

Wenxin Fan 1J

I passed out of 31A and 31B because of AP exams. However, I have decided to take the LS 30 series for math. Do I still meet the pre-reqs for the course if I am not taking 30B but have passed out of 31B?

Wenxin Fan 1J

Is there a difference between changing volume and changing pressure? Changing pressure does not always result in a shift because the addition of an inert gas has no effect, but does changing volume always result in a shift in the system?

Wenxin Fan 1J

I am confused by the notation when you determine the hybridization of bonds and lone pairs
an example was this: sigma(C2sp2, C2sp2) <=from the practice final exam on chem community
How would you write the notation if a double bond existed in the same place? Why is there a 2 in front of sp2?

Wenxin Fan 1J

If a question contains a chemical formula that only consists of gasses, will it be acceptable to write the equilibrium constant or expression as either Kc or Kp if it does not specify. The book had examples of both. Is there a go-to if the question does not specify? For example, chapter 11 question ...

Wenxin Fan 1J

Why is [Fe(CN)6]-4 hexacyanoferrate(II) instead of hexacyanidoferrate(II)? Shouldn't it be cyanido instead of cyano? are both correct? Table 17.4 says CN- is cyanido but can also be iso-cyano.

Please help!

Wenxin Fan 1J

The Roman numeral represents the oxidation number for a transition metal and should go right after the name of the metal.

Wenxin Fan 1J

A ligand is a Lewis base that bonds to a transition metal central atom. It doesn't refer to the entire compound.

Wenxin Fan 1J

Sigma bonds are the single bonds shared between two atoms. Pi bonds are the additional bond in double bonds. A double bond has 1 sigma and 1 pi bond. The distinction is how the orbitals are oriented in relation to another.

Wenxin Fan 1J

Hybridization is basically the fusion of two orbitals to to form a new set of orbitals to hold electrons.

Wenxin Fan 1J

After the initial electron is removed, the nuclear attraction on the electrons of the atom increases due to decreased electron electron repulsion. Making it more difficult to remove another electron.

Wenxin Fan 1J

You need to follow the Pauley exclusion principle and hund's rule. Electrons must fill all the orbitals in a sub shell once before pairing up with an electron the orbitals. Knowing this rule will help you to determine how many electrons are unpaired.

Wenxin Fan 1J

Based on Lewis structures you can see the arrangement if atoms in reference to each other. Looking at the bonding between atoms in the structure can also be used to determine the 3d structure of the molecule. These characteristics can be used to determine polarity by using the VSEPR theory in conjun...

Wenxin Fan 1J

Any element in and past the 3rd period has hybridizable d orbitals that can form a new set of orbitals to hold more than 8 valence electrons.

Wenxin Fan 1J

D block elements are transition metals which do not always have the same oxidation number. The oxidation number will usually be specified. Sometimes +2 or +1 will be written, but the oxidation number can also be shown in a compound name, usually in Roman numerals. There are a few exceptions that alw...

Wenxin Fan 1J

You write the electron configuration in the order of the principle quantum number "n". The n value of the d sub shell is n-1 compared to the s and the p subshell. Therefore, d is written first.

Wenxin Fan 1J

The XYZ system just helps to categorize the different electrons into their respective subsets in the p-orbital.
Wenxin Fan-1H

Wenxin Fan 1J

The answer is D because the uncertainty principle refers to objects with momentum (m x v). Therefore, the answers involving stationary objects are not applicable.

Wenxin Fan- 1H

Wenxin Fan 1J

Since both h and c are constants, you can use the equation to either find E, energy or lambda, wavelength.
-Wenxin Fan 1H

Wenxin Fan 1J

In chemistry the delta sign usually symbolizes change (in chemical equations it can show the application of heat). Therefore ΔE=hv is the equation for the change in energy while E=hv is just an energy calculation.
-Wenxin Fan 1H

Wenxin Fan 1J

The reason the spectrum lines are put in those categories or groups is because they share the same lower principle energy level (n=).
-Wenxin Fan 1H

Wenxin Fan 1J

A high percent yield means that there were fewer outside errors in the application of a chemical reaction. You want the actual yield to be as close to the theoretical yield as possible to allow for more accurate predictions and calculations. High yield may indicate that there are fewer impurities in...

Wenxin Fan 1J

There are 2 moles of Cl- for every mole of CuCl2. Therefore you just multiply the moles of CuCl2 from part A by 2. You yet 8.34x10^-2 moles Cl-

-Wenxin Fan 1H

Wenxin Fan 1J

Problems might ask for a reactant that is in excess. Also, when working a problem with a given amount (either in moles or in grams) of each reactant, you should always check to see which is limiting in order to determine the theoretical yield. Many problems won't explicitly ask you to identify a lim...

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