CHEMISTRY COMMUNITY

Aria Soeprono 2F

The slow step is the rate-determining step because a reaction can only be as fast as the slowest part. I like to think of it like a factory, where each step in the assembly line helps put together a product. This isn't a perfect analogy, but the production is limited by the step that takes the longe...

Aria Soeprono 2F

I am unsure if there is an easier or shortcut way to do this, but I know that if you draw the lewis structure you will see if it is a radical or not.

Aria Soeprono 2F

Why do the units change depending on the order of the reaction?

Aria Soeprono 2F

I believe you can use them interchangeably, the only thing is I think that log is a more common version of the equation.

Aria Soeprono 2F

The order of a reaction also indicates to what extent the concentration has an effect on the rate, as well as which species has the greatest effect.

Aria Soeprono 2F

Activation energy can help explain why a reaction is thermodynamically favorable but still will not occur because it has a very high activation energy and is therefore not kinetically favorable.

Aria Soeprono 2F

You need to have one conductive metal on each side of the galvanic cell. Therefore, if one side only has aqueous solutions (and therefore non-conductive), you have to add platinum as an electrode to that side.

Aria Soeprono 2F

A lot of the time you can also look on the periodic table for charges. For example, elements in column one have 1+ charge, and elements in the halide column usually have a charge of 1-. As you go further in to the middle of the periodic table it becomes less predictable, but you can usually figure i...

Aria Soeprono 2F

Always assume oxygen has a negative 2 charge.

Aria Soeprono 2F

What would be the purpose of using a porous disk instead of a salt bridge?

Aria Soeprono 2F

Endothermic reactions need energy to be added to the system to occur, and you could think of that like it is not spontaneous because it needs energy to react. In contrast, if it does not need energy to react, it should be more spontaneous.

Aria Soeprono 2F

If it's not dependent on the path taken, then it is a state function.

Aria Soeprono 2F

Boltzmann's constant is used for calculating entropy. The R in the Van't Hoff equation is referring to the gas constant.

Aria Soeprono 2F

The third law states that entropy of a perfect crystal is zero at temperature absolute zero.

Aria Soeprono 2F

Sometimes it will tell you, but sometimes you have to assume based on definitions alone. For example, by definition of enthalpy, you would expect the pressure to remain the same.

Aria Soeprono 2F

What is the significance of knowing that it is isometric/isochoric? Is it just to know that there is no change for when you're doing calculations?

Aria Soeprono 2F

It's also important to note that enthalpy is additive because of Hess's Law. It is a state function, so the change in enthalpy (Delta H) at each step of a multistep reaction can be added to get the total enthalpy change.

Aria Soeprono 2F

This might be an obvious question, but will a problem always tell you explicitly if it is reversible or irreversible?

Aria Soeprono 2F

Wouldn't a regular polystyrene calorimeter be an approximation of a closed system, because heat can go out but volume remains the same?

Aria Soeprono 2F

The reason why it is 0.10-0.06 instead of just 0.10 is because Ka is the ratio of concentrations at equilibrium .To understand this better, you could use an ICE table and put the values in. It would show that [HClO2] at equilibrium is initial [HClO2] - X, where X is the equivalent to the [H3O+] conc...

Aria Soeprono 2F

The internal energy of a system does not necessarily mean heat, it can also be referring to work, because U= heat + work. Therefore, in 4A. 3 (c), delta U is equal to the amount of work done, which is 28 J.

Aria Soeprono 2F

When you decrease the volume at equilibrium, it will shift towards the side of the reaction with fewer moles.

Aria Soeprono 2F

First, you have to calculate Q. Then, compare Q to the K value. If Q<K, the reaction proceeds to products. If Q> K, the reaction favors the left.

Aria Soeprono 2F

Strong Bases: LiOH - lithium hydroxide NaOH - sodium hydroxide KOH - potassium hydroxide RbOH - rubidium hydroxide CsOH - cesium hydroxide Ca(OH)2 - calcium hydroxide Sr(OH)2 - strontium hydroxide Ba(OH)2 - barium hydroxide Strong Acids: HCl - hydrochloric acid HNO3 - nitric acid H2SO4 - sulfuric ac...

Aria Soeprono 2F

Technically you could solve a problem without using an ice chart, it's just an easier way to organize and understand the information you are given.

Aria Soeprono 2F

As long as x is less than 5% of the initial value, than you know it is okay to approximate it to be 0 (in relation to the initial value, NOT the other values).

Aria Soeprono 2F

That response is correct, but also for calculating K, you usually do not include H20 because it is in excess.

Aria Soeprono 2F

Also, just something to keep in mind, is that if you have already solved the problem using the shortcut (when you assume x to negligible), Lavelle said that the general rule is anytime x is less than 5% of the initial value, then it is safe to assume an approximation to 0.

Aria Soeprono 2F

Spectator ions are present, but they are not part of the reactants because they do not react in solution. You do not include spectator ions in calculations because they do not affect the concentration of the products.

Aria Soeprono 2F

An ICE table is an easy way to organize the information needed to calculate equilibrium composition of a system. Start by identifying the components of the reaction (reactants and products) and list them. These will make up the columns of the ICE table. The rows are made up of initial molarity (I), ...

Aria Soeprono 2F

Once you convert to mol/L using the ideal gas law equation (as already mentioned), Kc indicates that the units used were in mol/L, rather than atm. Kp involves gasses that are not converted to moles, therefore it remains in units of atm.

Aria Soeprono 2F

An easy way to remember is Ka= [products]/[reactants]

Aria Soeprono 2F

Drawing the Lewis structure is probably the most accurate way to see how many and where the lone pairs will be located on the coordination compound.

Aria Soeprono 2F

H+ is a hydrogen ion by itself, while hydronium is a hydrogen ion bonded to a water molecule. When calculating pH, however, you can use [H+] and [H3O] interchangeably, and still get the right answer.

Aria Soeprono 2F

NaCl interacts with water, because the polar nature of water, however, it does not pull a hydrogen ion off of the water molecule, like an acidic salt would do.

Aria Soeprono 2F

Polydentate means that the ligands bind at multiple sites of the coordination compound.

Aria Soeprono 2F

Oh sorry I didn't mean remove the "-ide" just the "e" part.

Aria Soeprono 2F

When naming coordination compounds, you remove the "-ide" and add "o" to the end of the anion name. Therefore, I don't think there would be a place you would use cyanido, it would always be cyano. Somebody correct me if I'm wrong.

Aria Soeprono 2F

There is a coordination number of 6, due to the 6 Cn, and the overall charge is -4, so you take 6 + (-4) = 2, which is the oxidation state of Fe.

Aria Soeprono 2F

Dr. Lavelle mentioned that salt will completely dissolve so that each ion is surrounded by water molecules, but NiCl won't, and instead will become a coordination compound. Can someone explain why this happens?

Aria Soeprono 2F

A double bond is stronger than a single bond because of the presence of both a sigma and pi bond, but it is less than twice as strong as a single bond. Although I am unsure, using this line of reasoning it would make sense that a pi bond is weaker than a sigma bond. It makes a bond stronger in a dou...

Aria Soeprono 2F

A sigma bond is present anytime there is a single bond. A double bond is composed of one sigma bond and one pi bond.

Aria Soeprono 2F

When determining the bond angles for the VSEPR model, you could also think of electron density of the center atom in terms of the outer atoms. It may be easier to think of it like you are trying to make each atom as far apart as possible, and therefore creating the largest bond angles possible.

Aria Soeprono 2F

First, in order to find the VSEPR model for a molecule, you need to draw the Lewis structure. This is a 2D demonstration, and says nothing about the bond angles. To determine the shape, use 3 dimensions to find the angles that each atom (and therefore the electron densities) are as far apart as poss...

Aria Soeprono 2F

Yes, all molecules display van der waals forces, however, the most prominent example would be in non-polar, because polar and ionic bonds have stronger forces that are more characteristic of those bonds.

Aria Soeprono 2F

The greater electronegativity of the hydrogen bond acceptor makes hydrogen bonds very strong. Hydrogen bonds are a form of dipole-dipole bonding, but it is stronger than other dipole-dipole interactions due to the electronegativity and the size is very small, allowing the H atoms to be closer to eac...

Aria Soeprono 2F

Because ionization energy and electronegativity follow the same periodic trend, you could look for the element with the lowest electronegativity to be in the center of the Lewis structure, and it would come with the same result. More electronegative elements are usually found towards the outside of ...

Aria Soeprono 2F

In addition to the patterns of decreasing bond length from single to double to triple bonds, there is also a pattern in which larger atoms have a larger distance between each other, resulting in a longer bond length.

Aria Soeprono 2F

In my section, we talked about a shortcut where you take the number of valence electrons the element has in it's normal state, and subtract the number of valence electrons it has when it is bonded.

Aria Soeprono 2F

When ionization energy and electron affinity are high, then the atom will also have a high electronegativity, and pull shared electrons toward it. This explains the periodic table trends, but we will not need to know actual values of electronegativity.

Aria Soeprono 2F

I am not sure whether it will show up on the exam, but you should know that the effective nuclear charge is often less than the full nuclear charge due to the shielding effect of electrons.

Aria Soeprono 2F

Schrodinger's equation provides the connection that wave functions are equivalent to orbitals. It states that the wave function can be described using quantum numbers n, l, and ml, in which a higher energy produces a larger orbital. These wave functions are associated with particular "shapes&qu...

Aria Soeprono 2F

I forgot to add that for multi-electron atoms that come after atomic number 20, the 4s state is higher in energy than the 3d orbital, as you would expect. The 3d orbital is lower than the 4s only on the condition that the 4s orbital is occupied.

Aria Soeprono 2F

According to Aufbau's principle, orbitals are filled in accordance to the lowest value of orbitals. For 4s, n+1=4+0=4, and for 3d, n+1=3+2=5
So, although 4s is higher in energy because it has a higher value of n, it is filled first because it has a lower value of orbitals.

Aria Soeprono 2F

Intensity is directly correlated with the number of photons. The more intense the light, the more photons it has.

Aria Soeprono 2F

How do you know which is the initial molarity, initial volume, final molarity, and/or final volume from a given problem? How do you figure it out? In a problem that involves M1V1=M2V2 you must first identify which you are trying to solve for. If you are solving for final molarity, you know that the...

Aria Soeprono 2F

My TA said that at the end of class today he would go over what we should know for the test, but I would get familiar with the Shrodinger equation and be comfortable solving problems using it.

Aria Soeprono 2F

Would it be correct to say that 4d could have n=4, l=2, ml=-1, and ms=+1/2? and if so, would it be correct to assume that each possible configuration of quantum numbers for 4d represents an electron, giving the total number of electrons in that shell? You are correct that 4d could have those quantu...

Aria Soeprono 2F

It would probably be helpful to know the ranges of UV, visible, and infrared light, since that is the extent of what is used in chem for the most part, but i wouldn't worry as much about radio waves or microwaves because it doesn't seem as relevant to this course.

Aria Soeprono 2F

In the equation E=hv, I understand that h is Planck's constant, but how was this derived and what exactly does it mean?

Aria Soeprono 2F

According to the lecture, the photoelectric experiment involved shining UV light on a metal surface to measure the required energy to remove electrons from different types of metals. Using the wave model for light, scientists expected that with increased intensity, the metal would emit more electron...

Aria Soeprono 2F

I think you may be slightly confusing percent yield with percent error, in which case percent error is usually "acceptable" at around 5% (but it varies depending on the lab). In contrast, percent yield, although it may be affected by certain lab errors, does not directly correlate to error...

Aria Soeprono 2F

Yes, due Friday at your discussion

Aria Soeprono 2F

Significant figures are important to use, even if it means reporting a less accurate number as your official answer, because a result can only be as accurate as the least accurate measure. You have to be honest so that it does not appear to be more accurate of an answer than the equipment used to ma...

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