CHEMISTRY COMMUNITY

Sabrina Fardeheb 2B

Will we ever be required to write and derive each step on our own? Because I am a bit lost on how to create these equations in order to solve what the intermediate is and use the pre-equilibrium approach.

Sabrina Fardeheb 2B

Because it is on either side of the equations, it is labeled as an intermediate and we want to avoid including them in the rate law. Therefore, it is not written in the rate law.

Sabrina Fardeheb 2B

We don't necessarily need to label it as a slow or fast step, but rather use only that equation in order to solve the rate law.

Sabrina Fardeheb 2B

Big K represents the equilbrium constant of an equation. Little k represents the rate constant of an equation. When you derive the equations for each, they contain concentrations of the same elements. Therefore, with substitution, you can conclude that the ratio of the forward and reverse rate const...

Sabrina Fardeheb 2B

I don't believe that we will ever have to determine which is the fastest, we most likely will be given information for that type of problem. If they give you multiple reactions, then we most likely will only have to determine the rate laws and compare it to the one given to us.

Sabrina Fardeheb 2B

If the first step is the slow step, then it is significantly easier to solve and determine the rate law as no intermediates appear. However, if the fast step precedes the slow step, then we use the pre-equilibrium approach, which has a more complex effect on the overall reaction as we have to find a...

Sabrina Fardeheb 2B

You can plot the concentration values and examine the straight (it should be straight if it's an order reaction I believe) line to see what the value of the slope is. In addition, you can derive the integrated rate laws and use the equation y = mx + b to look at the sign. For example, for the zero o...

Sabrina Fardeheb 2B

Can someone please explain the explanations on page 622 for me? I understand the definitions and the rate laws of each reaction order, but I don't know how to determine the order if given a table of concentration values.

Sabrina Fardeheb 2B

It can't be in terms of products because if you evaluate the course of the reaction later on, you won't be able to evaluate the presence of products that well because they are constantly changing. Therefore, we examine the reactants at the beginning of the reaction because it's much easier to look a...

Sabrina Fardeheb 2B

It is always used to separate the cathode and anode. It represents the salt bridge.

Sabrina Fardeheb 2B

So does the fact that aqueuous elements are closer than the gases to the salt bridge trump the fact that the reactants should be listed first, then the products?

Sabrina Fardeheb 2B

yes, an inert electrode always has to be a solid. We normally use Pt(s) for the cell diagrams we've been doing. An inert electrode is necessary were both oxidized and reduced species are in the same solution.

Sabrina Fardeheb 2B

If they give you a cell diagram, you should first identify the cathode (right) and the anode (left). Then, you can either create the half reactions yourself, or you can easily look at the Appendix of the Electrochemical series and search for those elements in the list of the reactions given. All of ...

Sabrina Fardeheb 2B

for an ACIDIC solution:
- balance the O by using H20
- balance the H by using H+ (you can also use H30+ but it's easier to do H+)

for a BASIC solution:
- balance O by using H2O
- balance H by adding H2O to the side of each half reaction that needs H & add OH- to the other side

Sabrina Fardeheb 2B

Yes, they won't require you to memorize anything. If anything, it will be on a separate sheet or given with the question.

Sabrina Fardeheb 2B

Even when you multiply the half reactions by a factor in order to balance the number of electrons, the overall change of E does not change, while the value of delta G does.

Sabrina Fardeheb 2B

In the textbook, section 9.10 (The Overall Change In Entropy), they explain that a process produces maximum work if it takes reversibly, which we learned in Chapter 8. However, I don't understand their explanations for this statement. They said that: w rev is more negative than w irrev and q rev is ...

Sabrina Fardeheb 2B

In the textbook, section 9.7, can someone please explain the formula they give us? I don't recognize it in the lectures and maybe it's a more conceptual formula.

S(T) = S(0) + deltaS(heating from 0 to T) = deltaS(heating from 0 to T)

Thank you!

Sabrina Fardeheb 2B

To the posts above, why does it mean that the forward reactions are favored? What does it have to do with forward vs reverse reactions?

Sabrina Fardeheb 2B

I don't think so, I think Lavelle just wanted to show us how we arrived at that equation, and we'll only have to use it for mathematical questions in the future.

Sabrina Fardeheb 2B

It measures the energy that is freely available to do work.

Sabrina Fardeheb 2B

^ Yes, when the Gibb's free energy of the reactants is not equal to the Gibb's free energy of the products, you would use Q because it is not at equilibrium.

You would use K when the reaction is at equilibrium because it is a standard energy change of a reaction.

Sabrina Fardeheb 2B

Entropy is the probability that the system will be in 1 particular state, while degeneracy is the number of ways you can achieve that energy state.

Sabrina Fardeheb 2B

Can someone please explain the diagram from Wednesday's lecture? It consisted of a vacuum, work being done, external pressure, and heat. Is this a container with a gas? I'm mostly confused as to what's happening and in what system. Thanks!

Sabrina Fardeheb 2B

What is the difference between the entropy we have been discussing in class and positional (residual) entropy? Lavelle briefly mentioned the latter in the first lecture of week 3 and was unsure if we should place any importance on it. Thanks!

Sabrina Fardeheb 2B

Another example besides a bomb calorimeter is coffee or any other drink in a high quality thermos bottle.

Sabrina Fardeheb 2B

Maybe if we are given the values of delta H and delta U, then we would be expected to solve for the rest of the problem, but not for those values particularly. In addition, I'm pretty sure we won't have to worry about which equations to use since they will be provided to us on his worksheet

Sabrina Fardeheb 2B

I would focus more on the concepts of work and internal energy as well as calculating enthalpy and heat. This includes: the different methods of solving for enthalpy, calorimeter calculations. Don't worry about the equations that you need to calculate the actual work and internal energy. Hope this h...

Sabrina Fardeheb 2B

You can use prefixes!

ENdo = heat ENtering --> Because heat is coming in, then the outside will be colder.

EXo = heat EXiting --> Because heat is going out, then the outside will be warmer.

Sabrina Fardeheb 2B

An extensive property is something you can scale with system size, while an intensive property is something you cannot scale with quantity.

Also, extensive/extensive = intensive. For example: kJ/mol

Sabrina Fardeheb 2B

Can someone please explain how we calculated delta H in the first method we discussed in class? I don't understand how we arrived at the net reaction of the NO2 formation. Thanks!

Sabrina Fardeheb 2B

What are the measurable values for velocity in the DeBroglie equation? Because in lecture, it was said that it must be LESS than the speed of light, but then in the modules, there was a question where it was 10^5 and the answer was "NO, as it is significantly slower than c". What constitut...

Sabrina Fardeheb 2B

For Test #3 question #8, why are the possible quantum numbers both positive and negative 1/2? I put only positive 1/2 and got it wrong. I thought that unpaired electrons start off with positive 1/2 and then after the orbitals are half filled, then the electrons are spin down. Is this completely wron...

Sabrina Fardeheb 2B

What is the conceptual explanation behind ionization determining the strength of an acid/base? For example, why is it that an acid is weak because of incomplete ionization?

Sabrina Fardeheb 2B

If we were given 2 or more molecules and were asked which one is the strongest/weakest acid or base, what are the steps to determining that? How can you tell which one is more basic or acidic?

Sabrina Fardeheb 2B

Regions of electron density does have to do with bond angles. Some are easier to solve, like linear is 360 divided by 2 regions = 180 and tetrahedral is 360 divided by 3 regions = 120. However, others are not as easy like 109.5 (tetrahedral) and 106 (trigonal pyramidal). These angles differ because ...

Sabrina Fardeheb 2B

Well, you can memorize them, but I find it very helpful to look at visuals of molecules. Knowing why certain atoms are lower and closer together and understanding the effects of lone pairs on the shape can help if you look at examples. You can also make a chart of the number of regions of electron d...

Sabrina Fardeheb 2B

If it is a LIGAND , then you put the ligand names in alphabetical order + transition mental cation + roman numeral (indicating the oxidation state/charge) If it is an ANION , then anion name + -o ending + hydrate + -ate ending to the metal (if the complex has negative charge) If there is a CATION an...

Sabrina Fardeheb 2B

They are important because chelating ligands can bind cations tightly. An example of one is EDTA with a 4- charge, which is used to remove metals from solution.

Sabrina Fardeheb 2B

Lone-lone pair interactions are stronger because the electrons are closer together so they will repel the most. That's why when we're drawing Lewis structures, we want to put the lone pairs as far away from each other as possible because we want the least amount of repulsion. This causes the molecul...

Sabrina Fardeheb 2B

I believe that some molecules have 1 bond angle because the regions of electron density are symmetric around the central atom, while other molecules have different bond angles in order to maximize the distance between the number of spheres.

Sabrina Fardeheb 2B

A Lewis Acid is a molecule that accepts an electron pair.
A Lewis Base is a molecule that donates an electron pair.

Acids and bases can be considered in certain reactions to see how they form coordinate covalent bonds.

Sabrina Fardeheb 2B

You can tell if a bond is ionic and covalent by calculating their electronegativity. - A bond is ionic if the electronegativity difference is > 2 - A bond is covalent if the electronegativity is < 1.5 - If the electronegativity difference is between 1.5 and 2, then it will vary what the bond is. You...

Sabrina Fardeheb 2B

If a resonance structure is delocalized, it means that the electrons involved in these structures are involved in multiple bonds in different locations.

Sabrina Fardeheb 2B

Although it says on the syllabus that the test covers material up to October 27, Test 3 will only focus on the remainder of Chapter 1 (1.6 to the end) and all of chapter 2. You can review the Heisenberg Uncertainty Principle on his online modules. The post-assignment module questions are very helpfu...

Sabrina Fardeheb 2B

this equation tells us factors that have an impact on energy in multi electron atoms. It describes the relationships between charge, distance between charges, and how much the electron will attract. Because the distance is in the denominator, the farther away the electrons are, the less potential en...

Sabrina Fardeheb 2B

Well we write the x y z to indicate the orientation of the element. Writing 2p^1pp is technically correct but I'm assuming we write the x y and z to be more precise and tell us what axis it's on.

Sabrina Fardeheb 2B

The lines in the EM spectrum correspond to the Balmer series (visible light) and the Lymann series (UV light). If there is a drop in the energy level within a spectrum, think about the chain of electromagnetic radiation and whether energy/frequency/wavelength are increasing or decreasing.

Sabrina Fardeheb 2B

I have a question that relates to De Broeli. In chapter 1, for #33, why can't I combine and manipulate the equations for KE, E, and c in order to derive the wavelength? What's the difference between solving for the wavelength of light that ejects electrons and solving for the wavelength of the elect...

Sabrina Fardeheb 2B

How many sig figs is usually ideal for an answer? Should we truncate it to 3 digits or however many there are in the numbers given in the problem?

Sabrina Fardeheb 2B

Yes! When it is roughly a number. 8 or 9, you can round up to the next whole number. In other cases, you wouldn't round up/down if you have a number that can turn into a fraction, such as 1.33 moles. You can convert that number into a fraction: 1 1/3 = 4/3. Because this coefficient isn't a whole num...

Search found 51 matches