CHEMISTRY COMMUNITY

Victoria Draper 1G

In this homework problem why is the answer rate=k[NO][Br2] instead of rate=k[NO]^2[Br2]? Because in the end you are left with two NO molecules on the reactant side of the equation.

Victoria Draper 1G

Water will usually be in its liquid phase because it is occurring at room temperature. CO2 I believe is always in the gaseous state but I think that the problem will usually give you the phase of each of the substances.

Victoria Draper 1G

For this question you have to make sure that the sum of the two half reactions cancels out certain products and reactants in order to give you the original reaction equation. If both half reactions began with Au(+) then the sum of the two half reactions would not give you the reaction equation of Au...

Victoria Draper 1G

A pseudo first order reaction is when a reaction is a second order reaction but is treated as though it is a first order reaction. This occurs when the concentrations of one of the reactants is so large and remains constant throughout the reaction that it does not play a significant role in the rate...

Victoria Draper 1G

Enzymes are proteins functioning as catalysts that speed up reactions by lowering the activation energy. A simple and succinct definition of an enzyme is that it is a biological catalyst that accelerates a chemical reaction without altering its equilibrium. Amylase is an example of an enzyme that br...

Victoria Draper 1G

For two or more reactions of the same order, the reaction with the largest rate constant is the fastest. Because the units of the rate constants for zeroth-, first-, and second-order reactions are different, however, we cannot compare the magnitudes of rate constants for reactions that have differen...

Victoria Draper 1G

In my notes I wrote that a bimolecular reaction when two species collide. By species are they referring to two of the same type of molecule colliding or does it have to be two structurally different molecules colliding for it to be considered bimolecular?

Victoria Draper 1G

The collision theory primarily applies to gas phased particles because particles in the gaseous state have the proper structure needed for the right kind of collision to occur. Also, since the collision theory is based on the kinetic theory of gases it only deals with gas-phase chemical reactions.

Victoria Draper 1G

Is it possible for the value of k to be negative? Also, is there any direct relationship that can be seen between a change in temperature and a change in k?

Victoria Draper 1G

The log[Q] itself cannot be negative given the rules of logaritms and neither can Q due the fact that Q represents the concentration of products vs. reactants. So I'm not really sure what you are asking.

Victoria Draper 1G

My TA told me that the reason we do not switch the signs of the potential cell energy is because the equation Ecell=E(reduction)-E(oxidation) includes a negative sign next to the half reaction for the oxidation portion of the cell. The negative sign makes the value of the whole oxidation half reacti...

Victoria Draper 1G

The order does matter. The easiest way to put it is anode reactant|product|| cathode reactant|product. Therefore, anodes should go on the left while the cathode goes on the right.

Victoria Draper 1G

Enthalpy is a measure of heat content, so the greater the mass of any substance, the greater the amount of heat that it can hold at any particular temperature and pressure. Therefore, it is an extensive property I think.

Victoria Draper 1G

You can bring down the exponent of 6.02x10^23 and multiply it as a coefficient to (1.38x10^-23)(ln 3) so it will be (6.02x10^23)(1.38x10^-23)(ln 3).

Victoria Draper 1G

A temperature change occurs when temperature is increased or decreased by the flow of heat. This shifts chemical equilibria toward the products or reactants, which can be determined by studying the reaction and deciding whether it is endothermic or exothermic. This would therefore create a change in...

Victoria Draper 1G

If the external pressure is not constant, then you use the reversible reaction equation. When the external pressure is constant, you use the irreversible pathway equation. If the external pressure is less than the internal pressure, the gas will expand and do work. However, because this occurs in on...

Victoria Draper 1G

When comparing two different molecules, you have to look at the the total number of microstates that can be generated for each molecule along with the rigidity of the bonds within each molecule. A molecule with more bonds and more elements will usually have a higher entropy. If two molecules have th...

Victoria Draper 1G

Anodes are negatively charged because that is where oxidation occurs and therefore contains the atoms that lose electrons that eventually move towards the cathode. In the model we studied in class, which is known as a galvanic cell, it makes sense that the electrons would be flowing from a negativel...

Victoria Draper 1G

I believe so. When we are not given a specific temperature we just assume it is at standard room temperature.

Victoria Draper 1G

When the equation states "G = free energy of the gas at 1 atm + free energy difference due to different pressure" it is just verbalizing the equation of G=G°+RTln(P). If the RTln(P) part of the equation involves a pressure less than 1, then the whole value will be negative and will be subt...

Victoria Draper 1G

You use the Clausius Inequality equation to determine if a reaction is reversible or irreversible. In general, the equation is stating that the entropy cannot decrease in an isolated system because it will always be greater than the amount of heat given off over the temperature at which the reaction...

Victoria Draper 1G

An open system can exchange both matter and energy with its surroundings. A closed system can only exchange energy with its surrounding but not matter. An isolated system cannot exchange neither energy nor matter given the fact that it lacks any contact with its surroundings.

Victoria Draper 1G

What is meant by reversible and irreversible pathways and what are the basic ways to distinguish between the two?

Victoria Draper 1G

Degeneracy is the number of different ways energy can exist. Degeneracy and entropy are directly related and therefore the higher the entropy the more number of ways energy can exist which means a higher degeneracy.

Victoria Draper 1G

A diathermic wall is any wall that allows heat to be exchanged between a system and its surroundings.

Victoria Draper 1G

I think we will only need to know how to use the formulas but knowing how to derive them would definitely help in understanding them better.

Victoria Draper 1G

I was a little bit confused as well. I think for the most part this equation was shown in order to further explain how the -PdeltaV equation is derived but we would not necessarily need to use it in problem solving. The integral itself primarily shows how the change in volume (modeled by the integra...

Victoria Draper 1G

Molar heat capacity is a measure of the amount of heat necessary to raise the temperature of one mole of a pure substance by one degree K. Specific heat capacity is a measure of the amount of heat necessary to raise the temperature of one gram of a pure substance by one degree K.

Victoria Draper 1G

Enthalpy is the sum of internal energy and is the amount of energy released or absorbed during a reaction. Entropy, however, is the measurement of the disorder of a system. I don't think that there is any direct relationship between the two. Hope this helps!

Victoria Draper 1G

Molar heat capacity is often dependent on the structure of a molecule and also the intermolecular reactions that take place. Usually, larger and more complex molecules have higher molar heat capacities because they have more possible ways to vibrate, bend, and rotate. So in this case NO2 would have ...

Victoria Draper 1G

Yeah I am pretty sure that it is fine. I had a friend who was in a similar situation and is still enrolled in the course.

Victoria Draper 1G

Another general rule that will be helpful when given the pKa values of two molecules is that the lower the pKa the strong the acid is. Therefore, since the CCl3OOH has a significantly lower pKa value it is considered to be a stronger acid than CH3COOH.

Hope this helps!

Victoria Draper 1G

do we need to memorize what are strong/weak acids and bases? I don't think we need to memorize a list of strong/weak acids or bases but we should know the characteristics of what makes an acid or a base weak or strong. Knowing those characteristics will help in identifying a molecule as being an ac...

Victoria Draper 1G

For part c, the "en" signifies a bidentate and since the subscript is 2 it would mean there are two bidentates which allows for four ligands. And there is also 2 ligands from the Cl2 present in the compound so in total there is 6 potential ligands giving it a coordination compound of 6. Fo...

Victoria Draper 1G

I believe that if a compound is a tridentate it can act as a monodentate or a bidentate, but it has the option to form three up to three ligands and therefore is classified as a tridentate for that reason.

Victoria Draper 1G

In order to find the equilibrium constant, the equation does have to be written in terms of concentration or partial pressure but not both. In the answer that is given in the book, I believe they are taking into account Henry's Law which states that the concentration of a solute gas in a solution is...

Victoria Draper 1G

Kc or Kp are constant at constant temperature, but they vary as the temperature changes. As the temperature increases, the average kinetic energy increases as does the velocity of the gas particles hitting the walls of the container. The force exerted by the particles per unit of area on the contain...

Victoria Draper 1G

If you are trying to determine the oxidation number of a metal in a complex ion you can find it with this equation:

(# of Metal Atoms)x(oxidation number of each metal) + the sum of (the number of each ligand)x(charge of each ligand)= charge of the ion

Victoria Draper 1G

When looking at a lewis structure to determine the oxidation state, you can calculate it by taking the number of valence electrons in a free atom and subtracting it by the number of valence electrons in the bonded atom. (oxidation state= (# of valence electrons in a free atom)-(# of valence electron...

Victoria Draper 1G

When I first read the textbook I was a bit confused as well with regards to what those equations meant and how they related to hybrid orbitals. After reading it a few times, I think the textbook uses those equations better explain how they derive a hybridized molecule. The signs of each of the orbit...

Victoria Draper 1G

One of the main ways in which bonds within molecules are classified is based on the difference in electronegativity between two atoms. If the difference in electronegativity between the two atoms is greater than 2.0 it is considered to be ionic. Ionic bonds usually occur with elements that are oppos...

Victoria Draper 1G

Bond dissociation energy is the energy required to break apart a bond. In different molecules there are different types of bonds present such as single, double, and triple bonds. The bigger the multiplicity of the bond, the greater the dissociation energy will need to be in order to break the bond. ...

Victoria Draper 1G

Valence electrons are found in the outermost subshell of an atom. To put it simply, you can tell how many valence electrons an atom has by seeing which group on the periodic table the atom comes from. For example, the elements in groups 1 and 2 both have 1 and two valence electrons respectively. Onc...

Victoria Draper 1G

When referring to orbitals of electrons surrounding a nucleus, the word penetration describes the ability of an electron to get close to the nucleus. Therefore, s-orbitals do have an advantage over higher energy orbitals because of their proximity to the nucleus in comparison to others. This further...

Victoria Draper 1G

My TA told me that you must write the electron configuration in order of increasing energy levels and orbitals. Therefore, since 3d is a lower energy level compared to 4s you need to write that one first making [Ar]3d^24s^2 the correct annotation for Titanium even though the d orbital is not entirel...

Victoria Draper 1G

Hi! In most of the problems that we do for homework, l will not go greater than 3 but I do know that l can be equal to higher values such as 4 and 5 (and probably higher) which correlate to the g and h orbitals. These values I believe have been proven through experiments but I am unsure as to whethe...

Victoria Draper 1G

Hi! The magnetic quantum number is important because it tells us about the orbital that an electron occupies and also identifies the total number of orbitals there are along with their position within a subshell. For example, the p-subshell, whose angular momentum number (l) is 1, has three possible...

Victoria Draper 1G

Hi! So in part A I noticed that you plugged in the value that they gave you for velocity in the E=hv equation. The v in the E=hv actually stands for frequency and so therefore you cannot plug the value of (6.61x10^15) into that equation because that number is actually the velocity of the ejected ele...

Victoria Draper 1G

Hi! The primary purpose of the Bohr Frequency Equation is to model the law that states the frequency of the radiation absorbed (or emitted) during the transition from one energy level to another must equal the difference in energy divided by planck's constant. I'm not sure if that answers your quest...

Victoria Draper 1G

Hi! So for part a instead of finding energy using two separate equations, you can combine the two equations as E=hc/lambda which would be the same thing as solving for v first and then plugging it into the E=hv equation. The problem initially gives you the wavelength in nanometers so be sure to conv...

Victoria Draper 1G

Since nitrogen is a diatomic particle, it can always be assumed that when it is produced (especially under extremely high temperatures) it usually consists of 2. An easy acronym to remember which elements appear in twos is BrINClHOF.

Hope this helps!

Victoria Draper 1G

Since O is not an original reactant by itself, it cannot be added on as a product.

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