CHEMISTRY COMMUNITY

Madison Rhynhart 3H

This is based on the units. So for example, if you want your answer in terms of Joules I would use 8.314.

Madison Rhynhart 3H

Just use the slowest step, even if there seem to be multiple slow ones because the SLOWEST one overall will be the rate determining step.

Madison Rhynhart 3H

Intermediates are not present at the beginning of a reaction and are made, and consumed during the reaction while catalysts are not.

Madison Rhynhart 3H

pH is essentially the relative acidity of a solution based on H+ ions and pKa is the relative strength of an acid based on its dissociation constant. Therefore, the relationship between the two can be given using the equation pH = pKa + log([A-]/[HA]) where [A-] is the concentration of the conjugate...

Madison Rhynhart 3H

The rate determining step is going to be the slowest elementary step therefore, if you do come up with a situation with several slower steps just choose the slowest for this circumstance.

Madison Rhynhart 3H

You can either use the equation pH =pKa + log([A-]/[HA]) or you could use the pkA to find the Ka and then solve for H3O+ concentration using an ice table which would then be put into -log[H3O+] to find pH.

Madison Rhynhart 3H

These are essentially the same thing just in terms of the first equation you would have to reverse the sign of the anode thus it would be like adding it.

Madison Rhynhart 3H

When delta H is negative the system is losing heat and when it is positive the system is gaining heat.

Madison Rhynhart 3H

This is correct because if something has great reducing power than it is being oxidized and therefore providing the electrons for reduction, therefore is the reduction agent.

Madison Rhynhart 3H

To find reactants and products remember that everything on the left of the salt bridge or || is the anode and thus goes from reactants| products and the other side is for the cathode and goes from reactants to products as well. Those on the left are also being oxidized so should lose electrons and t...

Madison Rhynhart 3H

You would set G = 0 and then use the equation G = H - TS and then add in the H and S that you have calculated then solve for T to calculate the boiling point.

Madison Rhynhart 3H

If H+ is used in balancing the equation then it is an acidic reaction, and if OH- is used then it would be basic.

Madison Rhynhart 3H

It is a simple direct relationship, the greater the mass the greater the entropy.

Madison Rhynhart 3H

Because S = k*lnW if W = 1 then you would be multiplying the variable k by ln(1) which ln(1) = 0 therefore k * 0 = 0 and thus S =0 therefore there is no entropy.

Madison Rhynhart 3H

The changes in concentrations of pure substances are insignificant therefore we do not take them into account when solving for K as K relies of the changes in concentrations to be computed.

Madison Rhynhart 3H

This is the equation you would use to determine change in internal energy or when asked to solve for work of an irreversible system, when there is a constant pressure and changing volume.

Madison Rhynhart 3H

When covalent bonds form between hydroxide and hydrogen ions as a strong acid and strong base come in contact this causes heat to be released. Thus as heat is released it makes the reaction exothermic.

Madison Rhynhart 3H

You can truly use either in equations depending on the other constants given to you in the problem. However, as Kelvin is the standard unit for temperature this would be the more likely of the two to be used. Celsius may be used just you have to make sure to convert.

Madison Rhynhart 3H

This is related to the idea that the heat lost by a system in work (Q-system) is equal to the heat absorbed by the surroundings (Q-surroundings). Therefore q = -q represents this relationship with heat lost (-q) and heat gained or absorbed q.

Madison Rhynhart 3H

This equation is used when we are calculating initial energy when the volume remains constant, thus Cv versus Cp and is typically used for ideal gases.

Madison Rhynhart 3H

Isothermal merely refers to the the temperature being constant within a system, it does not change.

Madison Rhynhart 3H

A spontaneous reaction is one in which energy is released resulting in the movement from a higher energy level to a lower one. Therefore, this causes the system to have more entropy and aids in stability of the system.

Madison Rhynhart 3H

The formal equation would be U = q+w however, the negative sign in front of the w may have something to do with if the work is either negative or positive. However, if we want to denote the use of negative we can merely write, U = q + (-w) which would be the same as U = q- w. Therefore these are rel...

Madison Rhynhart 3H

Yes they are opposites. This is because when work is being done to a system, the object other than the system itself is exerting force or energy which would add to the cumulative energy of the system. In contrast, when the system is doing work it is the object that exerts energy, not an external for...

Madison Rhynhart 3H

If a reaction requires heat to be added to it, then it is an endothermic reaction. If the reaction releases or expels energy as a result or during the reaction then it is exothermic.

Madison Rhynhart 3H

The first equation is used for irreversible systems while the second is used for reversible systems.

Madison Rhynhart 3H

Standard entropy is just when entropy is measure at the standard conditions of 25 degrees celsius and 1 bar of pressure. Reaction entropy is all other conditions or circumstances.

Madison Rhynhart 3H

When work is being done by the system this would cause the system as a whole to lose energy therefore work or w would be negative. However, if work is being done to a system, then it would be absorbing or taking in energy and thus work or w is positive.

Madison Rhynhart 3H

As far as I know only outlines 1-3 are on the 1st midterm!

Madison Rhynhart 3H

In most cases changes in pressure will not directly affect the solid or liquid enough to cause significant notice, however if the pressure is great enough it may cause that liquid to take a solid form. It is all relative to the system.

Madison Rhynhart 3H

it is the product/reactant ratio and can be used to determine how much reactant and product is needed at equilibrium.

Madison Rhynhart 3H

An isolated system is simply what it sounds like, isolated from its surroundings thus unable to share matter or energy. However, a closed system is not entirely isolated but limited to sharing energy with its surroundings, however matter in this case is still "isolated".

Madison Rhynhart 3H

For molar heat capacity you would use q = nCΔT and for specific heat capacity you need to use q = gCΔT where n is moles and g is grams.

Madison Rhynhart 3H

With a constant volume you run into the issue of the volume not being able to change due to the lack of ability to expand thus no work can be done and no energy will be expelled for that work. However under Cp, or constant pressure, there is the ability for expansion and thus volume change which cau...

Madison Rhynhart 3H

pH will decrease in value as the solution becomes more acidic, thus there is an increase in the number of hydrogen ions in a solution.

Madison Rhynhart 3H

Yes ! this is true because if Q is the ratio of products to reactants and K is the ratio of those at equilibrium and then Q =K then we can assume the reaction is at equilibrium.

Madison Rhynhart 3H

Yes this is true because a negative delta H would indicate a release of energy (exothermic) whereas a positive delta H would indicate taking in energy or an endothermic reaction.

Madison Rhynhart 3H

Because the heat is used to break bonds in the phase change it cannot be used to raise the temperature.

Madison Rhynhart 3H

This is just two ways of saying the same thing, as they are both in the gaseous phase!

Madison Rhynhart 3H

Solids and liquids are excluded because when they are pure, therefore they are effectively constant within the reaction and it would make no sense to include them as it would not change the system.

Madison Rhynhart 3H

This is because the temperature has not change and temperature is the only variable in this case that would change an equilibrium constant.

Madison Rhynhart 3H

When Q is equal to K it simply means that the reaction is at equilibrium because K is the ratio of products to reactants at equilibrium and Q is the ratio of products to reactants at an point in the reaction therefore for Q to equal K it would have to mean that the reaction at Q is at equilibrium.

Madison Rhynhart 3H

They have the same basic formula to solve them in which you put the products/reactants however for Kp you would have to use partial pressures and Kc you must use molar concentrations.

Madison Rhynhart 3H

They are fairly similar however, lying to the right indicates that the equation is already at equilibrium but has a preference (or indication) that it is product favored while shifting to the right indicates that the equation is not necessarily in equilibrium and an imbalance in products or reactant...

Madison Rhynhart 3H

If we are given the gases in terms of molarity then you would use Kc because this indicates concentration, whereas Kp would indicate the use of partial pressures. However, you can technically either, though to use Kp when given molar concentrations you would have to convert those concentrations to p...

Madison Rhynhart 3H

When you reverse a reaction just as the products will move to the denominator so will K because K represents products/reactants thus reactants/products would indicate 1/K.

Madison Rhynhart 3H

A good rule of thumb is that if the chemical equations has only gases it would be more prudent to use Kp as it is easier to use the partial pressures for gases then have to convert use PV = nRT and when you have both gases and other molecules of different states (ex. aqueous) you should use Kc to ta...

Madison Rhynhart 3H

Equilibrium constants are "unit-less" in a sense and do not get written with units, however when calculating them you just have to make sure that all of your values for partial pressure, concentrations, etc are in the same units. Therefore, you can use bars, atm, or Pa to your discretion b...

Madison Rhynhart 3H

While the values of Q and K are calculated the same way, [products]/[reactants], Q demonstrates the constant value derived from a reaction at any point in time whereas K represents the ratio of products to reacts when the chemical reaction is at equilibrium.

Madison Rhynhart 3H

To determine electrons spins you would look at what orbital they are in: thus if they occupy the same orbital they have to have opposite spins to cancel each other out however if they are in the same shell but different orbitals they will have the same spin direction.

Madison Rhynhart 3H

Yes! This is true because the sigma bond will always be the first bond in molecule thus a single bond is a sigma bond and then once you have a sigma bond you can make a double bond which would include one pi and one sigma bond.

Madison Rhynhart 3H

I have been finding it helpful to go through the achieve problems, and run through the concepts in each outline and see if I can explain the basis of the concepts in my own words before doing the practice problems provided! I also hired a tutor, honestly having someone who can help explain it to you...

Madison Rhynhart 3H

You just have to memorize the list of strong bases unfortunately, to calculate would require a lot more complicated chemistry that we haven't learned yet

Madison Rhynhart 3H

I would 100% make sure to go the syllabus and cover all the material listed. It is a final exam so you should have a good knowledge of all listed material. Textbook problems are helpful for math practice but would also suggest relooking at homework problems for conceptual practice!

Madison Rhynhart 3H

No they are the same thing! It is just easier to write H3O+ as H+ as a shorthand but both are the same as H3O+ is adding an extra H+ ion to a water molecule therefore denoted as the extra H+ ion.

Madison Rhynhart 3H

pKa is simply the acid dissociation constant so it is an easier way to see H+ concentration. Therefore, instead of looking at it like 10^-5 you can simply write it as 5. This makes pH easily readable.

Madison Rhynhart 3H

A chelate is quite simply a band of ligands bonded in a ring around transition metals.

Madison Rhynhart 3H

Bronsted and Lewis are differentiated by what type of subatomic particle they accept or donate. For lewis structures the focus is on electrons, therefore they are electron acceptors (base) or donors (acid). For the Bronsted definition, the structures are focused on protons and are either proton dono...

Madison Rhynhart 3H

Within structure sigma and pi bonds are fairly easy to differentiate. The sigma bonds is always going to be the first bond and is a single bond within structure, a double bond is a pi bond + a sigma bond.

Madison Rhynhart 3H

Yes, chelates are soluble. For example a in metal chelates, EDTA, is typically the agent that maintains this solubility.

Madison Rhynhart 3H

Like the anions that we went over in class, I assume we may just have to be familiar with or know the ones we discussed in lecture and that should be sufficient! However, it may be helpful for later classes to be familiar with as many as possible, so practice never hurts!

Madison Rhynhart 3H

If you are able to move the pi bond within a molecule to another location and it still remains equal to the other structure then yes, it can be delocalized like any other bond!

Madison Rhynhart 3H

For a trigonal planar geometry they will be 360 degrees/3 or 120 degrees each!

Madison Rhynhart 3H

VSEPR stands for valence shell electron repulsion theory which helps us to determine a molecules molecular geometry based on electron density regions.

Madison Rhynhart 3H

Despite the fact that single, double, and triple bonds al have different bond lengths they are each treated as one region of electron density in the VSEPR model and therefore it does matter which resonance model is used to determine shape and may have some effect but in terms of overall geometry is ...

Madison Rhynhart 3H

You do not! Electronegativity can simply be determined based on the periodic table as it increases as you move up and to the right on the periodic table.

Madison Rhynhart 3H

The formal charge of the central atom should be as close to 0 as possible to allow for the most stable structure, however this does not necessarily mean that the formal charge is always zero. Therefore, in this situation one must look for the atom with the lowest ionization energy to be the central ...

Madison Rhynhart 3H

Stacking bonds really depends on the molecule and the most stable resonance structure in question. Sometimes, stacking bonds (ie. double or triple) results in a more neutral formal charge that balances itself out thus resulting in a more balanced structure or molecules while other times a single bon...

Madison Rhynhart 3H

Ion-dipole forces are going to be stronger than hydrogen bonds which are simply strong dipole-dipole interactions found between hydrogen atoms and strong electronegative atoms such as oxygen or fluorine. Despite this, ion-dipole interactions still remain stronger the fact they have the strongest int...

Madison Rhynhart 3H

The VSEPR model essentially takes the 2D lewis structure and applies the idea that areas of high electron density repel each other therefore, when we draw the models we must now take into account the lone pairs and areas of this density aim to be as far away from each other as possible resulting in ...

Madison Rhynhart 3H

Essentially, the goal is to have the lowest formal charge, hopefully zero, therefore this would be a minimized formal charge. To do this you can change the types of bonds as resonance structures may have both single and double bonds depending on the arrangement of atoms/electrons.

Madison Rhynhart 3H

To check for which structure would be best, you should calculate formal charges and see which one has the lowest amount ie. the most number of stable formal charge = 0. This indicates a more stable structure and therefore the better model.

Madison Rhynhart 3H

The G-C pairs are thought of as more stable because there are more hydrogen bonds present (3) vs. the A-T pairs only have two bonds. Furthermore, because there are more bonds present it would take more energy to break apart the G-C pair resulting in the idea that it is a more stable structure, becau...

Madison Rhynhart 3H

Water is polar because oxygen has a higher electronegativity than water therefore the oxygen atom will pull the electrons of hydrogen closer to it thus giving the oxygen a slightly negative charge and hydrogen will thus get a slightly positive charge as its electrons are attracted to the oxygen.

Madison Rhynhart 3H

The octet rule does not only apply to the central atoms instead it applies to both central, and surrounding atoms but can have exceptions including the expanded octet occurrence when an atom can have more than 8 valence electrons. Therefore, this is a case by case scenario and not defined by whether...

Madison Rhynhart 3H

Conceptually, the double bonds (covalent) are stronger than the single bonds (ionic) and therefore pull the electrons closer resulting in shorter bond lengths whereas the ionic bonds have less strength and cannot pull the electrons as close.

Madison Rhynhart 3H

A radical is a compound that has an odd number of electrons or rather has an unpaired electron which makes it more reactive. This is why free radicals in the body can cause excessive harm because they tend to react with our DNA causing mutation or damage.

Madison Rhynhart 3H

Yes! The atom with the lowest ionization energy goes in the center because it will need to share more electrons than that of other atoms in the structure.

Madison Rhynhart 3H

The average bond length has to do with resonance structure and when the molecule is delocalized therefore the length of the bond will not be as long as a double bond but not as short as a single bond due to it being averaged out across all bonds in the structure to create stability.

Madison Rhynhart 3H

The Lewis structure is most certainly not the most accurate representation of molecules, merely it is a 2D model that helps us to understand the bonding of electrons in the valence shell of the molecules. However, in reality, molecules are 3D structures that require much more complicated diagrams to...

Madison Rhynhart 3H

If the element is at an octet or has a full set of 8 valence electrons, then adding an extra electron would be unfavorable as it would create an unpaired set that would be more likely to bond or be lost to other molecules.

Madison Rhynhart 3H

This is merely a constant that can be found on a constants sheet and indicates that for 1 eV there are 1.602*10^-19 J

Madison Rhynhart 3H

Yes! this is ok as long as your recognize charge as an important factor in electron configurations and take into account that +1 charge is going to move the configuration down one electron and -1 charge is adding an electron thus adding to the electron configuration.

Madison Rhynhart 3H

Hi! DeBroglie's equation is meant (and only meant) to be used when dealing with physical matter like electrons, basketballs, baseballs, anything of that sort where as the equation wavelength = c/v is used for photons or light waves! This is because with DeBroglie's equation we can take into account ...

Madison Rhynhart 3H

To answer the question: merely increasing the intensity for a frequency of light that doesn't eject electrons will not help because there is not enough energy despite increasing the intensity. This is due to the idea that frequency is in a direct relationship with energy and if frequency and wavelen...

Madison Rhynhart 3H

Yes! The spin of an electron merely refers to the idea of the inherent properties of electrons for which one is that the electrons spin around their axis which is denoted by the +1/2 or -1/2 in the quantum number s. These spins are important because they allow for two electrons to occupy the same or...

Madison Rhynhart 3H

Electromagnetic radiation refers to the waves of the electromagnetic field and includes gamma rays, x-rays, etc. Therefore, gamma rays are a part of electromagnetic radiation and are merely higher in frequency than other electromagnetic radiation such as x-rays. So, to clarify: electromagnetic radia...

Madison Rhynhart 3H

Lobes do just refer to the shape of the orbitals s, p, d, and f. However, each lobe is not necessarily in the shape that you may recognize as a lobe (like in a p-orbital), instead some are spherical because they have one love like s-orbitals and may also be donut shaped, etc.

Madison Rhynhart 3H

Yes! Threshold energy and the work function are the same thing they just indicate the minimum amount of energy needed to eject the electron from a metal.

Madison Rhynhart 3H

Dr. Lavelle discussed in lecture that the cut off point for viewing wavelength as detectable in a lab at wavelength = 10^-15. Does this mean that the fact that all particles have wave-like properties should be disregarded in experiments or should those wavelike properties still be taken into account...

Madison Rhynhart 3H

Discrete units of energy are only allowed to be whole integers such as n = 1, 2, 3 and so on. They cannot be decimals so you cannot have a quanta be n = 1.67, etc. Discrete units are also thought of as packets of energy.

Madison Rhynhart 3H

In a problem, when it states to the 'energy of the incident' will this always refer to the energy of one photon/the energy of the light source?

Madison Rhynhart 3H

While I understand the concept that lower frequency light has no photons with sufficient energy to eject an electron, is there a specific cut-off point for the frequency of light to be deemed as emitting photons that are not sufficient or does it depend on the element that the light is interacting w...

Madison Rhynhart 3H

Hi I typically use the data given by the periodic table, as they are the most precise and will lead to a more precise answer later on. However you have to based the values for molar mass off of the significant digits you would like to get.

Madison Rhynhart 3H

While coming up with fractions as stoichiometric coefficients may lead to a balanced equation in terms of the law of conservation of mass, you still do have to make sure that all stoichiometric coefficients are the lowest whole number for both formulas!

Madison Rhynhart 3H

Hi! I believe that in 14A we will be given the chemical equations to balance however I did notice that some book questions require we determine the chemical equation for ourselves before balancing, so it may be helpful to just do a quick review via Youtube or I am sure through our textbook!

Madison Rhynhart 3H

Dr. Lavelle indicated that due to the law of conservation of mass we had to make sure that the total number of atoms on the left = that on the right however, does this not apply to moles as well? I was confused just because in the example he said conceptually we could say that in the chemical equati...

Madison Rhynhart 3H

In several of the textbook practice problems there has been (for example) Cl and the anion CL^- presented as part of a chemical equation needing to be balanced. Because there is an extra electron in the anion should we balance this separate from Cl or make sure that Cl and Cl^- have the same number ...

Madison Rhynhart 3H

I do not have this issue... sorry for adding on but I cannot seem to figure out how to post a new question on the forum? I obviously seem to understand replying to other posts but wasn't sure if there was certain area or link you had to hit to post new questions?

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