CHEMISTRY COMMUNITY

Hannah Yates 1K

It’s just the amount of time it takes for the reactant to become half its original concentration. What’s interesting with half life is that this time never changes no matter the amount of concentration you start with.

Hannah Yates 1K

Lavelle just showed us how to do it becasue it will help you understand how the two equations are related, but you will most likely not be asked to integrate a rate law on a test. I believe that the integrated rate laws are all on the equation sheet.

Hannah Yates 1K

Even if someone is thermodynamically favored, the reaction may not occur becasue of the rate of reaction. For example, Graphite is more Thermodynamically favored than diamond, but the activation energy for that reaction is extremely high for some reason so Diamond will never spontaneously turn into ...

Hannah Yates 1K

The melting of ice on a hot summers day would be spontaneous, so delta g would be negative

Hannah Yates 1K

IsabelLight2H wrote:I think it's because the battery is absorbing energy. A favorable reaction releases energy.

Exactly. For example, we supply energy to our phone battery by plugging it in.

Hannah Yates 1K

Nope, unfortunately tests are not curved.

Hannah Yates 1K

What’s the difference between balancing is acid and base?

Hannah Yates 1K

Hello, as I was studying Redox reactions, I found an acronym that I found very helpful when thinking about the movement of electrons!
It’s OIL RIG!
Oxidation is Loss (of electrons)
Reduction is Gain (of electrons)
Hope this helps everyone!!!

Hannah Yates 1K

Hello, while I was procrastinating my studies, I drew Lavelle! Thought I would share this with all of you!! Thanks for being a great professor !

Hannah Yates 1K

@ the midterm thissss yearrrrrr

Hannah Yates 1K

Should number 4 on the midterm review be when delta T = 0?

Hannah Yates 1K

Can someone explain 5c?

Hannah Yates 1K

For #6, how do we know that work is equal to 0? I was wondering the same thing. What I came up with was that is you use pv=nrt to find deltaV then you can see that since pressure, temperature, and R are constant the change in volume will depend on the change in moles. The equation has a 1:1 ratio f...

Hannah Yates 1K

I believe that Troutons rule is just stating that many liquids have about the same enthalpy of vaporization. Which means that they all take about the same amount of energy to vaporize.

Hannah Yates 1K

If you are given (or took to look up) the bond enthalpies, you then just have to use the equation that someone put above.

Hannah Yates 1K

I keep seeing the equation -qcal = qrxn. Can someone explain what this means.

Hannah Yates 1K

I think work is negative when the system is doing work, and positive when the system is getting work done to it. So when a system expands, work is negative, and when a system is compressed, work is positive.
I might be wrong though

Hannah Yates 1K

What is the importance of an isolated system? It seems like they dont really do anything?

Hannah Yates 1K

What isn’t a state function? Can someone give an example?

Hannah Yates 1K

What is the difference between endothermic and exothermic?
Also, since we just started discussing this on Wednesday, will we need to understand how it applies to Le Chatelier’s Principle?

Hannah Yates 1K

When do you calculate Q? I am having some trouble understanding why you would need this and when to use it.

Hannah Yates 1K

I have written in my notes “ if [h3o+] is less than 10^-7, then the solution is considered neutral”.
Can some one explain what this means, and why it is neutral?

Hannah Yates 1K

Depends. The reason you use the quadratic is because that is the values that the ice table gives you, but is the Ka is less than 10^-3, you can assume that when you are subtracting x from the initial concentration of the weak acid, that x is negligible because it is so small. This assumptions gets r...

Hannah Yates 1K

K is big when it is greater than 10^3 and small when it is less than K^-3, but what is it when the K value is in between 10^3 and 10^-3

Hannah Yates 1K

What does a small Ka mean verses a large kb?

Hannah Yates 1K

When K is Larger than 1, the forward reaction is favored and more products are being produced.
When K is smaller than 1, the reverse reaction is favored and more reactants are being produced.

Hannah Yates 1K

No difference in the way you calculate Q and K, but there is a major difference in what they mean. Q means the ratio of Products and reactants at any given point of the reaction, but K is the ratio of Products and Reactants at equalibrium. When comparing Q and K, it can tell us which reaction rate i...

Hannah Yates 1K

Use Kelvin. In most equations with temperature, you always use Kelvin

Hannah Yates 1K

In the reactions HCL + H20 -> Cl- + H30+
HCl- is the acid with the conjugate base of Cl-
H20 is the base with the conjugate acid of H3O+

Hannah Yates 1K

A lot of these polyprotic substances are things that have an ion in them that he went over in class when discussing Lewis structures. It’s important to note that these ions are stabilized with resonance so they are good acids

Hannah Yates 1K

An example of something that is amphoteric is Water
An example of something that is amphiprotic is HSO4-

Hannah Yates 1K

I do believe we have to memorize them. It will probably be useful to know them so that you understand why a reaction with them may act a certian way

Hannah Yates 1K

Transition metals are good for electron transfer because they have multiple oxidation states.

Hannah Yates 1K

Can the term coordination number apply to all molecules? or only some? I’m pretty sure a coordination number can only apple to coordination compound, which is the product of a Lewis acid-base reaction in which neutral molecules or anions (called ligands) bond to a central metal atom (or ion) by coo...

Hannah Yates 1K

The numbers are just something extra he wrote out on the board, but they aren’t really talked about in the textbook. I would still recommend putting it on the test if asked.

Hannah Yates 1K

I am also not too sure on my answer, but I am pretty sure that a sigma bond has just hybridized orbitals, but the reason a pi bond can form is because of an extra (not hybridized) p orbital. This allows for a double and triple bond to form.

Hannah Yates 1K

I think the most important thing to know is to understand what makes something a sigma bond and what makes something a pi bond. I don’t think he would directly ask us to draw how they are bonded, more like ask us to explain how they are bonded. In order to explain, it could help to draw a picture.

Hannah Yates 1K

The completely dark wedge represents the atom coming towards you, and the dashed wedge represents the atom going away. I’m not quite sure why, but I also don’t think it matters that much as long as you know that they are on a diferent plane.

Hannah Yates 1K

A molecule can always be slightly distorted. This can happen because of what atoms are attached to central atom. If all 4 of the attached atoms are the same, then you will have a normal tetrahedral shape, but the second that one of the atoms are different, there will be a slight distortion to the mo...

Hannah Yates 1K

There are 6 areas of electron density, but only 4 bonding regions. This is because there are two electron pairs. The molecular geometry of the molecule is only dependent on the bonding regions. While the number of areas of electron density says thats the shape is octahedral, the actual shape is squa...

Hannah Yates 1K

Rod and spherical shaped were just an example of two possible shapes. He then used pentane and 2,2-dimethylpropane as two examples of those shapes. Pentane is rod shaped and 2,2-dimethylpropane is spherical. Pentane has a higher boiling point because the intermolecular forces are stronger because th...

Hannah Yates 1K

Formal charge is usually what I check last. It’s a good way to check that you didn’t do something completely wrong because if you had a formal charge of like -4 somewhere, thats a big clue that there is a big mistake. If the formal charges all make sense and are where they should be (negative on mos...

Hannah Yates 1K

H-Bonding isn’t actually a type of bond. A lot of people get this confused because of the word bonding in it. H-Bonding is another type of Intermolecular force (or interaction). Compared to Ionic and Covalent bonds, H-bonding is very weak, but it is definitely stronger than Dipole-Dipole.

Hannah Yates 1K

Any atom in the 3 orbital or lower can have an expanded octet. It is very common to see it on S, P, and Cl. A good example is PCl5. Phosphorus has an expanded octet with all 5 chlorine’s bonded to it.

Hannah Yates 1K

505168807 wrote:Is there a possible way to determine whether the spin is +1/2 or -1/2?

No, I dont think that there is any way determine this, and if there is, we haven’t learned it.

Hannah Yates 1K

Effective Nuclear Charge increases when the number of protons increases, and the number of protons increases as you go across a table

Hannah Yates 1K

I had a few questions about the grading of this course. 1) how do I check my grade? 2) Is their any curve applied to the Tests? And 3) Is their any way to make up points lost on Tests?

Hannah Yates 1K

L just refers to what sub shell the electron is in. The point of L=n-1 is to show the max value of L that it could be. So the value of L is not always going to be n-1.

Hannah Yates 1K

there’s no rule that I know of, but I do know that when we do nomenclature of molecules, the name gives the number of valence electrons that the atom is loosing. For example, Copper (II) Oxide is the nomenclature for CuO. The nomenclature gives that Copper looses 2 electron.

Hannah Yates 1K

This question isn’t related to properties of light but I didn’t know where to put it. Does anyone know where to go to check our grades in the class?

Hannah Yates 1K

H bar will not be given, which just means you need to do one more step when using Heisenberg indeterminacy equation. But, h will definitely be given.

Hannah Yates 1K

When electromagnetic radiation is emitted from an atom, I believe it means that the electron is dropping from a high energy level, to a low energy level. This means that the statement is false because when an electron does make that drop, energy is being emitted from the atom, therefor it is loosing...

Hannah Yates 1K

Technically the 2s and 2p are the same orbital, but they have different suborbital. S is the closest suborbital to the nucleus, then P, then D, and so on.

Hannah Yates 1K

The reason he gave us something with an unmeasurable wavelike property is so that we could understand that no matter what the velocity of that object is, if the mass is too big, it wont act like a wave. Like he said, a baseball, no matter how fast it is traveling, will never act like a wave. Only sm...

Hannah Yates 1K

In order to find the velocity, you would need the Energy of the ejected election. That means that you would either need the given the energy of the ejected electron or have a way to calculate it with the given information using the equation E(photon) - Threshold energy = E(electron).

Hannah Yates 1K

He basically said that it could be used but he doesn’t recommend it. I learned it in high school and it always confused me (even thought it is just plugging numbers into an equation). I didnt get it because I didnt get the basic understanding of what was happening. The way Levelle teaches this secti...

Hannah Yates 1K

I have always struggled on knowing the state of a given molecule so I am hoping that they will be given until we go over it in class.

As far as if it affects calculations, it doesn’t. All it does is help us visualize the reaction.

Hannah Yates 1K

I don’t know if this will help anyone, but every time I balance a combustion reaction, I am always thinking in even numbers. The reason for this is that if there is an odd number of oxygen on the product side of the reaction, the coefficient will end up being a number and a half. If I am always thin...

Hannah Yates 1K

I have once been told that if the number were something like 2.652 and I had to round to the 1st decimal place, it would be rounded to 2.6, but I have never really payed attention to that rule. Typically, I would still round to 2.7.

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