CHEMISTRY COMMUNITY

FionaHunter21

Likewise, a denotes that it is an acid, and b denotes that it is a base.

FionaHunter21

They are all the equilibrium constants, but the different subscripts can denote differences in what the equilibrium constant is for. For example, Kw is for water, so the w is for water, Kp is for when there are gases, and their measurements are in pressures, so p=pressure, and Kc is when we are deal...

FionaHunter21

I think he wants us to know the strong acids and bases that are listed in the book. In an equation, the conjugate base/acid is the base/acid once it has lost or gained a proton.

FionaHunter21

Sometimes it helps to double check your math in a computer system that solves quadratics so you can see if the math is the problem or the set up.

FionaHunter21

In terms of comparing Q and K, I use that if Q<K, I think of it as K moved left to get to Q, following the arrow of the sign, so to go back, it needs to go right, so the reaction favors the products and vice versa.

FionaHunter21

I'm confused on whether to use 1/kc or just kc. If I use the original kc, I get 2 positive answers for x, and when I use the reverse quotient, I get the incorrect answer for the problem. Can anyone walk me through which values they used? I used the forward reaction, and the kc value that I found fr...

FionaHunter21

Can we find x using either kc or 1/kc? As long as we put the respective products and reactants in their correct position depending on whether the reaction is reversed or forward?

FionaHunter21

So is R the same constant as the one we used before on the equation sheet?

FionaHunter21

I used the same steps, but when I put the numbers in my calculator I got 0.0223

FionaHunter21

So only the conjugate acids or bases of weak acids or bases will affect the pH?

FionaHunter21

Yes, so the common ones have anions with a charge of -2 or more, such as sulfate and phosphate, and these can have either one, two, or sometimes three hydrogens.

FionaHunter21

The structure of the molecule won't change the overall charge of the molecule (formal charges must add to same overall charge), so typically if you take the acid or base, and either add a proton or remove one, it will either gain a charge or lose a charge to form the conjugate acid or base.

FionaHunter21

It's just the difference between specifying if the H+ ion is bonded to the water or not. I think Dr. Lavelle wants us to practice using the full hydronium ion since the proton would be binding to a water molecule.

FionaHunter21

I was confused about some of the salt stuff too. In this case, isn't NH3 a weak base, and the resulting acid is just a conjugate acid?

FionaHunter21

I notice that all the problems above are labeled to be at 25 degrees Celsius. How would the temperature affect the pH of substances? I think that when the temperature changes, it can change the rate of reaction, but I think 25 degrees Celsius is about room temperature, so it is specifying that. Som...

FionaHunter21

So pKa is the -log(Ka)?, which dictates what the pH is? Or is there a different equation for pKa?

FionaHunter21

How can we identify if a molecule is amphoteric or not? Other than water being a common one?

FionaHunter21

So the acid gives a proton and the base accepts it, so the conjugate base of an acid would lose an H+ ion, and the conjugate acid of a base would gain an H+ ion?

FionaHunter21

Is the acid itself being more electronegative make it a stronger acid or is it the conjugate base ?

FionaHunter21

I always make sure that the number of regions of electron density match up with the number of hybridized orbitals. Sometimes I try to read the hybridized orbitals as s1p1, s1p2, s1p3... etc rather than just sp or sp2. This makes it clearer when I add it up so that I don't miss that s counts as one o...

FionaHunter21

Always check to see if there are unnecessary formal charges on atoms, and if there are any that can be zero by adding or removing a bond in place of a lone pair!

FionaHunter21

Are electrons only delocalized when the shape is a ring or can it happen with any molecules that have resonance structures?

FionaHunter21

I believe this is figured out by looking at pi bonding. whenever you have an even number there are enough pi bonds to lock the carbon into a single plane. This is because the pi bond does not allow for rotation. Every pi bond is formed at a 90 degree Angle to the other, so even numbers would go bac...

FionaHunter21

Do pi bonds only occur in double and triple bonds? Or can be somewhere else where there are orbitals side by side?

FionaHunter21

Since each carbon atom has four bonded regions, that would make it tetrahedral!

FionaHunter21

Another common example is nitrogen triple bonded to a central atom, having two lone pairs on the opposite end of the atom. I think if there are two regions of electron density (whether bonded or lone pairs), it can be linear

FionaHunter21

When the formal charges are added, they should equal the overall charge of the molecule, and they favor the structure that has the most atoms with a formal charge of 0.

FionaHunter21

Are there dipole moments between all atoms with a difference in electronegativity or just the polar bonds?

FionaHunter21

For larger molecules like these, is the order that the formula is written in the same order of the molecules in its structure? At least for the most part?

FionaHunter21

How do we tell which way the internuclear axis is lined up?

FionaHunter21

Give the ground-state electron configuration expected for each of the following ions: (a) Cu+

I was doing this problem and was confused as to why the answer was [Ar]3d10 instead of [Ar]4s2 3d8? Does it fill up the 3d block before the 4s block?

FionaHunter21

If Lewis acids are always electron deficient, can they always form coordinate covalent bonds? Or is that only in certain cases where the base has a lone pair to contribute?

FionaHunter21

Is an anion always the atom that is polarizable and the cation is what can have high polarizing ability?

FionaHunter21

Between two anions in the same row, would an anion with a -2 charge be more or less polarizable than an anion with a -1 charge?

FionaHunter21

Are london dispersion forces present in all nonpolar molecules?

FionaHunter21

So other hydrogen atoms can form hydrogen bonds to any N,O, or F molecule that has unpaired electrons in the valence shell? Or do they need to be N,O, and F atoms that are already bonded with a hydrogen?

FionaHunter21

So shorter bond lengths have higher energies right? Since they are stronger the energy of the bond is more negative, but is it still considered higher energy?

FionaHunter21

I know that the elements in the 3d block and also the 3p block can have expanded octets, but how many additional electrons can they fit? Is it only one more orbital (making 10) for p-block, and more for d block?

FionaHunter21

What types of molecules are capable of inducing a dipole moment?

FionaHunter21

Does it matter if the covalent bond is polar or nonpolar in terms of its strength?

FionaHunter21

Are we supposed to know all of the exceptions to the periodic trends, or is it sufficient to understand the trends and why there are a few atoms that don't follow these rules?

FionaHunter21

So there are only 4 possible subshells, which would be s, p, d, and f?

FionaHunter21

Hi. I am still a bit confused about this. Is it correct to say that the Hamiltonian value represents the probability of finding the electron while the energy wave function represents the orbital itself? It would be great if someone could explain what exactly the equation is representing with the tw...

FionaHunter21

I was under the impression we would only have to know the first part (H times the wave function = E times the wave function), however I was also curious if we needed to know the other pieces that are on the equation sheet.

FionaHunter21

Right now, can we consider the wave function to just be simplified to the version where we treat it like a sine function?

FionaHunter21

So just to clarify: an increase in frequency increases the energy of the wave and the number of photons, but not the energy per photon? And this is what the photoelectric effect is? That the waves have particle like properties where only one photon interacts with an electron, and therefore changing ...

FionaHunter21

What is the difference between the question asking what the maximum wavelength is and just simply the wavelength? Does it change how we need to solve it?

FionaHunter21

I think Dr. Lavelle specifically changed the order of questions on the Sapling homework so that problems 1-19 were wat would be on the midterm, so I would study those topics to the extent they are talked about in the homework.

FionaHunter21

If we manipulate other equations based on the values given, and we set the two equal to each other, does it matter that the one equation has a greater than or equal to symbol? For example, if we have delta p = m(delta v), and delta p is greater than or equal to h/(delta x)(4pi), can we still substit...

FionaHunter21

I also get confused about the n1 and n2 terms. Is n1 the final energy level and n2 is the initial? I thought it was the other way around but problem 8 on the sapling homework has it that way.

FionaHunter21

I think that Dr. Lavelle said we wouldn't be working with the equations that are used for other atoms that aren't hydrogen, but it is possible to tweak the equation so that it would work in other scenarios.

FionaHunter21

Can't we also just look at the figure that shows the wavelengths and series? Since it is in the UV series, the final energy level =1, and since it is the second line in the series, it goes from level 3 to 1? The first line represents it going from 2 to 1, so just add one each time?

FionaHunter21

Oh wait I meant shorter wavelength, but thank you!

FionaHunter21

When Dr. Lavelle was explaining that each atom will only absorb/emit a specific frequency of light, does this also mean that each atom requires a different amount of energy to excite an electron from its ground state to the next level?

FionaHunter21

Adding on to memorizing the wavelengths, are we also supposed to know things like the frequencies or energy of each one, or can we just understand that higher frequency correlates with longer wavelength and more energy?

FionaHunter21

If you had the perfect amount of two reactants for them to react with one another and there to be no excess of anything after, would you say this equation has two limiting reactants or none?

FionaHunter21

For formulas with C,H, and O, I think they follow that order, but outside of carbon being first and hydrogen second, I've never seen a formal description of what order to write them in.

FionaHunter21

For the textbook readings and exercises: we do these for practice, but we don't turn it in online? Or is there somewhere we are supposed to upload our work to?

FionaHunter21

So are we supposed to know how to write a formula for a given molecule based on its prefixes and ending? Should I review the difference between endings such as -ide vs -ate, and things like that?

FionaHunter21

I agree with all of these! I've always done it at the end, as long as you note at the beginning what number of sig figs you should round to at the end. I find it easier to do that when I first read the problem so that I don't get confused later on.

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