CHEMISTRY COMMUNITY

Chantel_2I

No matter how quickly the fastest reaction occurs, the full reaction is not complete until the slowest one is done. Therefore, the rate of the full reaction is determined by the slowest step.

Chantel_2I

I think in deriving the equations, we use some basic integration rules, but for specific ones like the integral of ln, the rule is usually given.

Chantel_2I

Kinetics focuses on the process and speed of the reaction, while thermodynamics focuses on the beginning and end of the reaction, regardless of how the reaction got there.

Chantel_2I

Thermodynamics concerns the beginning and end states of a reaction, which delta G gives us information about. Delta G tells the difference between the free energy at the end of the reaction and at the beginning.

Chantel_2I

Kinetics describes the pathway of reactions, with an emphasis on the activation energy that signifies the energy difference between the free energy of reactants and the transition state. Kinetic analysis is about the speed or rate of reaction, using experimental techniques to observe reactant &...

Chantel_2I

It relates the equilibrium constant, k, to temperature, activation energy, and A. Given any 3 of these, you could find the other variable.

Chantel_2I

Yes, taking the natural log of both sides of the first equation would give you the second equation.

Chantel_2I

If the second step is the "slow step," there will be a buildup of the product of the first step, so the first reaction will tend to go in the reverse direction as well, creating an equilibrium scenario.

Chantel_2I

The way a catalyst lowers the activation energy is by creating a completely new path to get to the products, which has a lower activation energy.

Chantel_2I

Is a catalyst considered a type of intermediate?

Chantel_2I

The differential equation tells the change in concentration over time, but the integrated equation tells the specific concentration at any specific time.

Chantel_2I

Does anyone remember any specific ones that were mentioned in class?

Chantel_2I

A zero order equation integrated gives a first order equation, which when graphed, gives a straight line, as opposed to a second order equation, like something with x^2, that gives a parabola.

Chantel_2I

We use the rate to compare how it will change when concentration changes. To get the overall order of the equation, we add the orders of each reactant.

Chantel_2I

What makes something able to act as an electrode or not?

Chantel_2I

Could someone explain why Eo doesn't change when the amount of matter changes? Does this mean that the maximum potential of a battery stays the same no matter how much of the reduced and oxidized substances you have?

Chantel_2I

After balancing the redox reaction, you can see how many moles of electrons are transferred in the reaction. Use the coefficient of e- after simplifying the balanced reaction.

Chantel_2I

Also, how does the potential for work relate to E?

Chantel_2I

How is a battery doing work through the redox reaction? Is there a change in energy happening with this?

Chantel_2I

I believe the idea behind this expression is that the maximum potential change in voltage occurs before any change has occurred.

Chantel_2I

Would a battery technically never die if there is a salt bridge or porous film? It sounds like the salt bridge brings it back to equilibrium, so if so, why would the battery die?

Chantel_2I

Dr. Lavelle mentioned that this is the common arrangement, but it should be possible to tell based on other information given which one is the anode and which is the cathode. I wouldn't rely on it always being in this arrangement, though.

Chantel_2I

Overall, just be sure both the electrons gained or lost on the left are equal to those gained or lost on the right. Usually, the oxidation states are the most obvious sign to use to balance the reactions.

Chantel_2I

The salt bridge allows the electrons to continue to flow by replacing the charge that is transferred from the cathode to the anode. It allows the cycle to continue until the voltage reaches zero.

Chantel_2I

Yes, they should cancel out, which is why we must balance the reduction and oxidation reactions, to make sure the number of electrons on the left is equal to the number of electrons on the right.

Chantel_2I

We can find delta U by subtracting the Initial U from the final U. We simply look at the two states, not the process of getting from the initial to the final.

Chantel_2I

The integral represents the sum of all the changes over a certain change in volume. We take the negative integral of P with respect to the change in V, but since P is constant, we bring it out of the integral and multiply it by the integral of dV from v1 to v2. Evaluating the integral gives you V2-V...

Chantel_2I

An example for work of expansion is like the one we talked about in class today. A gas can push the piston to expand its volume. This is energy being given off as work.

Chantel_2I

Is W2/W1 always equal to V2/V1? The proportion between W2/W1 and V2/V1 will always be equal, although the value of W2 and V2 will be different. How can the proportions be the same but the values be different? Can someone please elaborate or give an example so I can further understand? (: W2 does no...

Chantel_2I

Which equations, if any, does each law correspond to?

Chantel_2I

We use w=-P(delta V) only when pressure is constant. Otherwise, we use the integral from v1 to v2 of -P(ex) times the change in V.

Chantel_2I

Is U a state property? Why or why not?

Chantel_2I

Isolated systems are insulated while closed systems are not. This means that while the amount of matter is constant in both, closed systems can exchange energy with their environment while insulated systems cannot.

Chantel_2I

MariaJohn1D wrote:Does the pressure change in a bomb calorimeter?

The pressure within the calorimeter can change when there is a reaction. However, the pressure inside is not changed by the external pressure because it is an isolated system.

Chantel_2I

Dr. Lavelle specified in class that there can still be a lot happening within the system, without it interacting with the surroundings. Everything within the calorimeter is part of the system, and reactions can still occur within the system. However, there will be no energy transfer with anything ou...

Chantel_2I

Is there a reason why the horizontal line for vaporizing water is so much longer than the one for melting ice?

Chantel_2I

When the vapor touches your hand, it undergoes a phase change to become liquid on your hand, therefore releasing even more energy in the form of heat. However, when boiling water touches your hand, it does not have that extra energy to release because it is already in the liquid phase.

Chantel_2I

It begins to vaporize when the temperature reaches the boiling point. It stays at that temperature until it's completely vaporized.

Chantel_2I

Often, if you know what kind of reaction it is, you can determine if it is endothermic or exothermic. For example, breaking a bond is usually endothermic.

Chantel_2I

Could someone also explain why heat is not a state property? Thanks!

Chantel_2I

I believe so. If the amount of H3O+ or OH- added is so small, the change in pH is negligible.

Chantel_2I

Q is used to determine whether the reaction is at equilibrium or not. The equation for Q is the same equation as the one for K. We compare Q to K to determine which way the reaction is shifted.

Chantel_2I

A strong acid wants to completely dissociate, so it makes sense that the conjugate base would be weak because it is unfavorable for it to form more of the strong acid. The same is true for strong bases. It would be unfavorable for the conjugate acid to form the strong base.

Chantel_2I

It is uncommon for the reactants and products to have the same stability, so the equilibrium lies toward the side that is more stable because a reaction in that direction will happen more readily.

Chantel_2I

When we create ICE charts and and solve for X, we often get in the denominator the initial concentration minus X. However, we use the 5% rule to determine whether it is valid to simply the denominator to simply the initial concentration to make it easier to solve for X. We can do this simplification...

Chantel_2I

We are essentially multiplying the concentrations of all the products. So if you have R1+R2 <-> 2P, it's like having P + P, so to find K, we multiply [P]x[P], so [P]^2.

Chantel_2I

I think the only place this would come into play is when writing the chemical equation. After we have the correct chemical equation, we treat the rest of the problem the same with any type of acid or base.

Chantel_2I

Because weak acids do not dissociate completely, some concentration of a weak acid would produce less H3O+ than the same concentration of a strong acid. Therefore, the concentration of H3O+ will be lower with the weak acid, so the pH will be higher.

Chantel_2I

It depends on what the question is asking. You would find Q to compare it to K to determine whether the reaction is at equilibrium, and if not, which way it leans toward.

Chantel_2I

The only factor we have learned that changes K is temperature. K is the ratio of P to R, so when although the concentration of R increases, P proportionally increases to keep the ratio constant. Their individual concentrations change, however their ratio remains.

Chantel_2I

Group 1 ions do not usually affect the pH of the solution. That is why K+ is left out.

Chantel_2I

Also, when it has more electronegative atoms, it pulls the electron density away from the OH bond, making the bond weaker, so it's easier for the H to be removed. Thus, it's a stronger acid.

Chantel_2I

Something can be a Lewis acid and Bronsted acid at the same time, but they don't always have to be both. However, they will never contradict each other.

Chantel_2I

When the anion is stable, the dissociation of the acid is more likely to happen because reactions favor stability. This makes it a stronger acid.

Chantel_2I

How would you do it for ammonia and phosphoric acid?

Chantel_2I

After taking out H2O because you know water and a salt are formed, try combining the anion of one molecule with the cation of the other to find the salt.

Chantel_2I

Where N has a lone pair, it can usually accept a proton.

Chantel_2I

Do leading zeros after the decimal count as significant figures in pH? for example, if there is a pH of 3.043, does the zero count as a sig fig?

Chantel_2I

H2SO4- and H2PO4- are anions that can act as acids, whereas most anions do not. Although they have an overall negative charge, they have more H atoms that they can give up.

Chantel_2I

In both molecules, the H are bonded to the O. So, we can't use that to differentiate the strength of the H bonds. However, since Cl is more electronegative, it pulls the electrons more toward itself and away from the O-H bond, so the O-H bond becomes weaker, which means the acid is stronger.

Chantel_2I

It depends on the salt. The salt will only affect the pH of the water if the dissociated ions are unstable and therefore react with the water. The product of the dissociation can either pull a H atom off of a water molecule, turning into -OH, or add a H atom, making it H3O+.

Chantel_2I

Does the CO2 make the body more acidic when it interacts with water? Or is it when it interacts with something else? Or by itself?

Chantel_2I

Why can strong acids not have a Ka value?

Chantel_2I

In the resulting anion, resonance makes the anion more stable because it delocalizes the charge of the electrons, so it's distributed more evenly across the molecule. this makes it less likely to react with other surrounding molecules.

Chantel_2I

The Lewis definition and Bronsted definition will never contradict each other, so either way, an acid is an acid and the way it reacts doesn't have to do with its definition.

Chantel_2I

Electronegativity is one of the ways by which the resulting anion of an acid losing a proton could be stable. When the resulting anion is more stable, the reaction is more likely to occur because reactions favor stability. Since the reaction is more likely to occur, more of the acid will dissociate,...

Chantel_2I

It would be best to memorize the common strong acids and bases we talked about.

Chantel_2I

When it comes to strong acids, what conceptually makes one stronger than the other? If a strong acid, by definition, dissociates completely in water, how can there be varying levels of dissociating completely?

Chantel_2I

Acid rain results from the sulfur that reacts with the water, so since clean coal has less sulfur, replacing it with "dirty" coal would be one way.

Chantel_2I

Although having more than one H proton doesn't always mean that it's polyprotic, it's a good sign that it might be because it has multiple protons in the form of H atoms that it can release.

Chantel_2I

The p in pH and pOH just means "take the -log of" so if you need the pOH, you do -log[-OH]. Sometimes, you only have enough information to calculate the pOH, but you can then use it to calculate the pH if necessary.

Chantel_2I

You can write the formula for conjugate acids and bases by adding the original compound to water, and then showing that the reaction yields OH- and the conjugate acid or H+ and the conjugate base. For acid dissociation: A + H2O -> A- + H30+ A- is the conjugate base For base dissociation: B + H2O -> ...

Chantel_2I

Organic molecules also contain a carbon atom.

Chantel_2I

When the anion is unstable, the salt changes the pH of the solution because the anion may pull a H proton off of a water molecule, turning it into -OH, making the solution more basic.

Chantel_2I

This molecule has three Nitrogen atoms, each with a lone pair. Each long pair can form a bond with a cation, so it is tridentate.

Chantel_2I

I believe it is because cisplatin has the chlorines pointing in the same general direction, so cisplatin can bond more strongly to DNA, whereas transplatin can only bind to the DNA on one site at a time and can easily be removed off of the DNA strand.

Chantel_2I

When naming molecules, you first state the name of the cation, then the anion. Place the name of the complex anion or cation in brackets. Within the brackets, you name the ligands first, in alphabetical order. If there is more than one of any ligand, write the corresponding prefix for the ligand. If...

Chantel_2I

The total charge of the whole anion is -3, so the charge of the cation must be +3 in order to neutralize the compound. Since the charge of potassium is +1, there must be three of them to reach a +3 charge.

Chantel_2I

There isn't really a formula for it. Instead, you use the charge of the whole ion, when given, and the charge of the ligands with a known charge. The total charge of all the ligands and the metal must equal the total charge of the ion, so you figure out what charge the metal must have in order to ma...

Chantel_2I

The more valence electrons there are, the more electron-electron repulsion there is. The electrons repel each other, so they aren't pulled toward the nucleus as strongly.

Chantel_2I

Bonds are longer or shorter depending on the distance between the two atoms. If there are multiple bonds, there are more shared electrons, so the atoms are more closely held together and the bonds are shorter. Also, if the atoms are smaller they can be closer together, so smaller atoms also make sho...

Chantel_2I

You can use the trends on the periodic table we learned to determine which ions have the smallest size. The cations with the smallest size and highest charge have the most polarizing power.

Chantel_2I

Forces that affect boiling point are based on the strength of the intermolecular forces, so the ones that would most affect BP are the ones that are the strongest. So ionic interactions would have the highest effect, followed by hydrogen bonding, then ion-dipole interactions, and the last few all b...

Chantel_2I

Which type of intermolecular interaction is strongest and why?

Chantel_2I

The s and p orbitals are the most outer orbitals. An octet fils the s, px, py, and pz. When more electrons are added to the d orbital, they go in the d orbital of the lower energy level. For example, once you have 4s, the next electrons go to 3d. Therefore, since the 3d are not in the 4th energy lev...

Chantel_2I

When calculating the formal charge, we want the outer elements to carry the negative charge as opposed to the middle element right? If so, can someone explain why? The element with the lowest ionization energy goes in the middle, which means the middle one is less electronegative than the outer one...

Chantel_2I

Electronegativity is how strongly an atom will attract electrons. Generally, as atoms get closer to having a full valence shell, they are more and more likely to gain an electron, which is why electronegativity increases as you go further right on the periodic table.

Chantel_2I

Resonance structures still do follow the octet rule because they are just different possible structures for the molecule. Either way, to be stable, most atoms do follow the octet rule.

Chantel_2I

Electronegativity is a calculated value, but for the test, we will not need to calculate or memorize the values.

Chantel_2I

If the energy of the photon exceeds the energy absorbed, the extra energy will be given off as light.

Chantel_2I

Why do these series start at n=1 and not n=0 even though n=0 represents the s orbital?

Chantel_2I

The speed of light can be used in regard to all types of electromagnetic radiation.

Chantel_2I

Moving from left to right, the electrons added are in the same energy level. Therefore, the effect of shielding does not increase drastically with the addition of each one in a single period.

Chantel_2I

The effective nuclear charge is the less intense attraction that the electron feels when it is shielded by other electrons. Because the full charge of the nucleus does not reach the electron, it is not pulled to the center of the atom as strongly, so this results in a bigger atomic radius.

Chantel_2I

The G orbital does exist, but in their ground state, electrons are not in the G orbital, so it is therefore not represented on the periodic table.

Chantel_2I

The equations on the sheet in that link are everything that will be given during a test as well.

Chantel_2I

Another note that might help is that ultraviolet is always next to violet, and infrared is always next to red. So, when trying to figure out what order the colors of the visible spectrum are in (starting with violet or red), remember this and the colors should be in order of energy level with the ot...

Chantel_2I

So what distance does Δx represent on the electron level? The change in position between the first energy state and the second? Delta X is the distance in which the electron can be found. For example, in the particle in a box problem, delta x would be the diameter of the box. In atoms, we usually u...

Chantel_2I

A +1/2 electron and a -1/2 electron would react differently when exposed to a magnetic field. This number differentiates between the two electrons, but it doesn't literally mean that they are moving in a specific direction.

Chantel_2I

Wavelike properties mean that light travels like the ripples of water; it spreads in diffractions. Particle-like behavior means that each photon of light is a single object the travels like a bullet would. Light has both types of properties.

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