CHEMISTRY COMMUNITY

Aprice_1J

For mini marshmallows 2c, why is it cupperate instead of copper? Isn't it a +1 oxidation state?

Aprice_1J

For this problem it asks to identify what the reaction is and what the acid or base is for either the cation or anion. How am I supposed to determine what the cation or anion is? For example on of the compounds that reacts is KClO and water is present, how am I supposed to know to just use ClO?

Aprice_1J

Can someone explain the first step where they say HNO3=H3O+ please, thanks!

Aprice_1J

Is the coordination number the same thing as the oxidation number?

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How can you tell what is able to form a chelating complex? For example, in 9C.7, how does the different structure of diaminobenzene change the ability to form a chelating complex?

Aprice_1J

For part d, does anyone know why diagua translates to (OH2)2? What happens between OH and H20 in the naming process?

Aprice_1J

I think the reason that it has the three is because there is no indication that the complex has a charge and so in order to neutralize it, you would have three potassium ions for the first one (you know that chromate is +3 and that cyanido is -6 so you would need +3 to get it to 0.) The same logic a...

Aprice_1J

Why is it aqua instead of hydroxide? Where does the OH get the extra hydrogen from?

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I understand the definition of Bronsted and Lewis acids and bases but how do you identify if an acid or base is Lewis or Bronsted when it is in a reaction? Does this determine how you then deal with the reaction.

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If something is a chelate what does that tell us and how would we identify it? Is there more to know other than just the definition of it?

Aprice_1J

Why do some molecules have a stronger affect on pH than others? I know that all conjugate bases of a strong acid do not change the pH (from lecture on 12/2) but why is this and does it have to do with how much hydroxide or hydronium is produced and the amount of dissociation?

Aprice_1J

I was confused about this as well, is there a "correct" place to put the lone pair or do you just have to consider the effect it will having on shape and angles?

Aprice_1J

Can ionic bonds only happen between alkali metal and other nonmetals?

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Is there more to know about cis vs. trans other than knowing cis is non polar and trans is polar?

Aprice_1J

Are there any good ways to think about whether or not the dipoles cancel in a 3D model? Can it ever cancel if not all the atoms are the same?

Aprice_1J

Can anyone explain why double bonds are sigma plus pi and not just pi bonds? If a pi bond represents a double bond why is there a simga bond as well?

Aprice_1J

Can anyone explain why double bonds are sigma plus pi and not just pi bonds? If a pi bond represents a double bond why is there a simga bond as well?

Aprice_1J

For part C, why is it set up in such a way? Why can't you have a mixture of a and b where the lone pairs of the central atom are on the other side and the bonds are on the other side? What makes one more stable than the other and how do you tell the difference.

Aprice_1J

Can someone explain how they set up this problem? I set mine up so it was like a T with a lone pair on S but I'm not sure how that leads to a bond angle of 109.5. If it is trigonal pyramidal it has 3 bonds and 1 lone pair so I would think my set up is okay but the bond angle makes me think otherwise.

Aprice_1J

Can someone explain why you get angle degrees of 109.5 and 120? I understand 180 and 90 but I'm not sure what shape/measurement would lead to either 109.5 or 120.

Aprice_1J

The book refers to some of the answers as having a t-shape. Could someone explain the difference between a t-shape, trigonal planer, and trigonal pyramidal to me? In lecture we went over trigonal planer but I am not sure the difference between these other ones.

Aprice_1J

I was also confused by this. Why is it that the hydrogens are closer to each other rather than all of them being in two intersecting lines with the fluorine as far away and the hydrogen as far away from each other.

Aprice_1J

A good way that a TA explained this to me is that the nucleus is pulling the electrons in but if there is another electron in between the nucleus and the outer electron that is pushing it out. If you draw this as a picture the line between the nucleus and the outer electron is longer than the line b...

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As you are going towards the right the radius decreases and as you are going up it decreases as well. The reason that it decreases as you go across is because you are adding more protons and those are pulling the electrons in closer to the nucleus making it smaller. It decreases as you go up because...

Aprice_1J

Something that helped me to figure out where different types of bonds should go besides just guessing was to always start by giving oxygen two lone pairs and a double bond. It might not always work out but knowing this made it a lot faster for me.

Aprice_1J

The goal is to have the lowest formal charge for all of the atoms in the structure. Some rules to follow are that the charges of the atoms (if they have one) have to add up to the charge of the overall compound and if you have a negative charge it is better to put that on the more electronegative at...

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In the equation EP is inversely related to -(a1-a2/r^6), where do we find the values that we plug into this and why is it necessary to have a negative in the beginning?

Aprice_1J

How do you have two induced dipoles? If one dipole causes an induced dipole how do two occur at the same time?

Aprice_1J

When you have something with a 5d and 4s electron configuration, is the s orbital higher energy if there is an electron in the d orbital?

Aprice_1J

Is there an easy way to recognize if it is talking about light/photon properties or wavelength properties? What is usually given and what are you usually asked to find?

Aprice_1J

When do you know to put the hydrogen on the outside? Does this mean it is delocalized? Is there a rule for when this applies and when it doesn't? Can you only do this when you have one hydrogen atom?

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When you are finding the lewis structure with the least amount of energy, is the goal to minimize the formal energy of each of the different atoms or of the molecule as a whole. For example would you rather have three charges equal 0 and one equal 1 or would you rather have 2 charges equal 0, one eq...

Aprice_1J

Can someone explain the pauli exclusion principle? In my notes from lecture I have, "no more than 2 electrons per orbital state, if electrons are in the same orbital then spin paired." I am not exactly sure what this means, I understand spin states but the part with the amount of electrons...

Aprice_1J

When would you see them have parallel spins? If they are more stable with different spins, what would constitute them having the same spin?

Aprice_1J

Can someone explain how to set this up so that you can get to the electron configuration. I understand that you want to fill the shells so that they become more stable and how to put in the spin state but what is the order that you fill in the shells?

Aprice_1J

In my notes from lecture it says that "S electrons have a lower energy than P electrons in the same shell." How do you know whether or not it is the same shell and does this still hold true if it isn't?

Aprice_1J

What is the reasoning behind making sure every atom has 8 electrons attached? Is it because we are looking at the S and P orbitals and they can hold 8 electrons between the two of them? I understand that we are trying to maximize the stability but beyond that it is unclear to me.

Aprice_1J

In lecture when we talked about different Lewis Structures producing different formal charges, was the goal to minimize the formal charge overall or just for individual atoms?

Aprice_1J

Another important conceptual thing to think about is that the more you know about the position of an electron, the less we know about its velocity- they have an inverse relationship.

Aprice_1J

When first looking at this problem something that is important to note is the change in units. To make sure that this doesn't get you confused because that is a little thing that is easy to overlook, I like to set it up as a fraction and make sure that all of the units cancel out. Some of the conver...

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When would we use this in class? I understand the concept of it but when would we have to apply what we know about it or is it just a concept that we should understand?

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When the question says that it is ultraviolet, we know that the line is observed at n=1. If there is a final n value of 3, it is paschen series, if it is 2 it is balmer and if it is 1 it is lynman. Because n final is 1, we can then say that it is lynman series.

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You would use the E=hv equation. You want to take the frequency given to calculate the energy needed to eject the electron which is also the energy of the incoming light and equal to the threshold energy. It can also be helpful to draw a picture for this problem so you can visualize the unknowns.

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Could someone please explain how in step c of homework problem 1B.15 you get from E light equalling 2.25x10^-17J to the wavelength equalling 8.8x10^-9m. What is the equation to connect energy of light and wavelength?

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Something that one of the LA's taught me that is helpful if you're stumped on a balancing equations problem is to writing it as a system of equations. For Cu + SO2 --> CuO + S you would put a letter in front of each of the different parts and then write out an equation for every element. Cu would be...

Aprice_1J

The first thing that you want to do is convert the given amount to moles. When you have it in moles you can use the stoichiometric coefficients to set up ratios. For the ratios the best way to think of it is setting it up so that everything cancels. If you find the moles of CuBr and you want to get ...

Aprice_1J

I know that when you use Avogadro's number you are converting from moles but what unit are you converting to? A TA had told me that is depends on the context of the question but I am still unsure. Does anybody have any good examples/ways to interpret it? I am specifically struggling with whether or ...

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I had a question on part E of homework problem E21. This part asks what 4.37 grams of nitrogen is as N atoms and as N2 molecules. I divided by the molar mass and then multiplied by Avogadro's number but after that I am lost. When it explains atoms to molecules in the book it shows it as 1 H atom or ...

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When I solved for the moles of the diluted solution I got .005 (.05M/.1L) but I am confused as to why you multiply it by two. I know that it is the moles for NH4NO3 and that there are two nitrogen atoms but what is the reasoning for multiplying the moles by two. Is it that in the ratio there are 2N ...

Aprice_1J

When you are balancing an equation you are looking at the number of moles in each molecule and adjusting the coefficient. When you are manipulating chemical equation to find other information such as mass you would convert to grams.

Aprice_1J

Can a combustion ever produce anything in addition to CO2 and H2o?

Aprice_1J

For part a you're going to look at the equation they gave you first to establish what the limiting reactant is, what there is excess of and how much oxygen is left over for the next equation. You will start by diving 5.77 g P4 by the molar mass and then multiplying it by the ratio of O2 to P4 and th...

Aprice_1J

In terms of how the differ equation wise for formula units you are going to divide the grams of the compound by the molar mass of the compound and then multiply by Avogadro's number whereas if you were looking for how many atoms of lets say oxygen are in an ionic compound you would take the grams of...

Aprice_1J

What I would suggest doing is putting it as a fraction over 2 so then you can easily multiply everything by 2. For example, if you have O2 on the reactants side and you need 3 oxygen to match the 3O on the product side you could just multiply the O2 by 3/2. This way when you multiply the entire equa...

Aprice_1J

For this problem (During a summer camping weekend 4 moles of butane (C4H10) gas were used for cooking. Chose the right balanced equation for the combustion of 4 moles of butane gas. What is the net number of moles of gas produced?) which is located in the balancing chemical equations post-module, I ...

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