CHEMISTRY COMMUNITY

Inderpal Singh 2L

I personally convert everything to mol/L to simplify and organize the whole process better!

Inderpal Singh 2L

Make sure to include H2O if it is a gas!

Inderpal Singh 2L

We don't include water because it is available in such a large amount that very little is being put to use. Therefore, it is considered a constant and allows for water to be canceled out in the equation.

Inderpal Singh 2L

You usually wouldn't need to use an ICE box for strong acids/bases. However, I believe that there is no harm in doing so.

Inderpal Singh 2L

Since water does not ionize completely, it is considered both a weak acid and base.

If you would like a more in-depth description:

http://chemed.chem.purdue.edu/genchem/t ... nd%20bases.

Inderpal Singh 2L

I think you should have most of them memorized. However, when you do enough practice with these types of problems, they become increasingly easier to identify I've found!

Inderpal Singh 2L

I am pretty sure that they don't always have to be equal, and sometimes the [H30+] will be larger than [OH-] making it acidic, and the [OH-] can be larger than [H30+] making it basic. However, the Kw will always be equal to 10^-14.

Inderpal Singh 2L

Kw is the equilibrium constant for [H30+][OH-], not the equilibrium constant for the Ba equation.

Inderpal Singh 2L

Yes! Q is when the reaction is not at equilibrium.

Inderpal Singh 2L

Dr. Lavelle said that for this class we should assume that the gases given are ideal :) in reality, I don't think there are many ideal gases. Heres a website with some more info if ur curious: https://www.khanacademy.org/science/physics/thermodynamics/temp-kinetic-theory-ideal-gas-law/a/what-is-the-...

Inderpal Singh 2L

Molarity = mol/L
And n, in this case, represents mol
V would be liters(L)

Inderpal Singh 2L

You are essentially "flipping" the reactants and products of the forward reaction, and when you would "plug" this into the equation, you would end up with the reciprocal of the forward reaction. This applies in the other direction as well.

Inderpal Singh 2L

We have to use Kelvin, but we will have the conversion equation on the equation sheet I believe in case we are given celsius.

Inderpal Singh 2L

It K is less than one, it is favoring the reactants.

Inderpal Singh 2L

Why do cisplatin and transplatin behave differently?

Inderpal Singh 2L

What are the common characteristics of a strong versus weak Lewis base?

Inderpal Singh 2L

The biggest tip I can give you is to draw the lewis structures. It becomes much easier to identify if a compound if polydentate or not.

Inderpal Singh 2L

In one of the lectures, an "amphoteric line" was shown which was very similar to the metalloid line, are these all the possible amphoteric compounds or are their more than just these?

Inderpal Singh 2L

This is a super simple diagram, but it may help clear some minor details up:

https://lh3.googleusercontent.com/proxy ... gXwGPHRmvQ

Inderpal Singh 2L

HA is the acid and A- is the base!

Inderpal Singh 2L

Wedge = to you
Dash = away from u

This helps visualize it.

Inderpal Singh 2L

This is a life saver! Thank you.

Inderpal Singh 2L

I saw this too and I am not sure either.

Inderpal Singh 2L

Heres another great link!

https://courses.lumenlearning.com/bound ... ng%20water.

Inderpal Singh 2L

I don't think so!

Inderpal Singh 2L

I don't believe that resonant bonds can rotate.

Inderpal Singh 2L

I believe we will need to know a decent amount of it.

Inderpal Singh 2L

I believe the order does not matter.

Inderpal Singh 2L

^What is a hybridization scheme?

Inderpal Singh 2L

Why can Pi Bonds not Rotate? I cannot visualize it properly.

Inderpal Singh 2L

Make sure you always draw out the Lewis Structure!

Inderpal Singh 2L

I believe if the electronegativity of the central atom decreases, so will the bond angle.

Inderpal Singh 2L

I do not believe there would be any exceptions to this, however, I would seek further clarification.

Inderpal Singh 2L

I think we will have to memorize it but with enough practice, some of them should become very apparent to us.

Inderpal Singh 2L

These links may help provide some insight :) : https://www.dartmouth.edu/~genchem/0102/spring/6winn/VSEPR2.html#:~:text=The%20bond%20length%20is%20determined,apart%20the%20ligands%20themselves%20are. https://physics.stackexchange.com/questions/215405/how-are-bond-angles-determined#:~:text=The%20posi...

Inderpal Singh 2L

I believe resonance means there are delocalized pi bonds.

Inderpal Singh 2L

Lone pairs actually have the highest repulsion, meaning they push the bonds farther away compared to if they were not lone pairs. This causes the bond angles to decrease.

Inderpal Singh 2L

Essentially, you mix together orbitals to create a new orbital that is better suited to form chemical bonds. This is a really good video :) :

https://www.organicchemistrytutor.com/hybridization/

Inderpal Singh 2L

I used flashcards and drew out the structures myself multiple times.

Inderpal Singh 2L

The two lone pairs repel each other, making them move away!

Inderpal Singh 2L

The best bet would probably to use flashcards. I would also look at some YouTube videos, their might be some nice tips and tricks.

Inderpal Singh 2L

Would we have to memorize the bond angles as well?

Inderpal Singh 2L

The more stable the better :)

Inderpal Singh 2L

I believe that it can

Inderpal Singh 2L

Why is Flourine considered the most electronegative element and not Helium? I know that the trend increases from bottom left to top right, so I was curious.

Inderpal Singh 2L

I have already read that ionic bonds are stronger than covalent. I am not sure if their are exceptions.

Inderpal Singh 2L

CHI3 has a higher melting point because it is bigger.

Inderpal Singh 2L

Will there ever be exceptions to the rule that H-bonding only occurs between H and N, O, or F?

Inderpal Singh 2L

How many unpaired electrons are predicted for the ground-state configuration of each of the following atoms: (a) Bi; (b) Si; (c) Ta; (d) Ni?

Please help :)

Inderpal Singh 2L

Covalent bonds are usually formed between two nonmetals while ionic bonds are between a metal and nonmetal. Ionic bonds are also considered to be stronger than covalent bonds, due to the attraction between positives and negatives.

Inderpal Singh 2L

Is there a such thing as a quadruple bond by chance? So far I have only heard of single, double, and triple bonds. Even if we won't be reviewing it in this class, will be ever come across a quadruple bond in chemistry?

Inderpal Singh 2L

You would base it off the one that has the higher electronegativity! Also, remember that induced dipole moments can cause compounds such as N2 to have one nitrogen slightly more electronegative than the other.

Inderpal Singh 2L

As far as I know, it is because sulfate has d-orbitals. However, I am also still confused on why it is allowed an expanded octet. However, I think it may have something to do with the post being directly above mine ^ (-2,-1,0,1,2)

Inderpal Singh 2L

How does the professor calculate the number of valence electrons in an element so quickly? Does it have something to do with its position in a column of the periodic table? (Oxygen has 6 VE)

Inderpal Singh 2L

Double bonds have a higher number of electrons than single bonds, therefore being pulled closer to the nucleus of the atom. The nucleus of the atom is positively charged while the electrons are negative, opposites attract :)

Inderpal Singh 2L

I agree with everyone else that group 13 elements do not require an octet.

Inderpal Singh 2L

I also agree, I would like to go over what I got wrong and right, or else I will never know what to improve on.

Inderpal Singh 2L

Triple bonds are the strongest bond so they would indeed require more energy than single and double bonds to break.

Inderpal Singh 2L

I am also unaware of this effect. It would be nice if someone could explain it :)

Inderpal Singh 2L

Increase across a period and decrease down a group :)

Inderpal Singh 2L

Does anyone know an acronym for remembering periodic trends? For instance, for the different wavelengths, there was Rauls Mother is Visiting Uncle Xaviers Garden. (Radio, Microwave, Infrared, Visible, UV, X-ray, Gamma).

Inderpal Singh 2L

You would get 1- for this.

Inderpal Singh 2L

Equivalent to it's atomic number.

Inderpal Singh 2L

I would stick to the previous noble gas or just writing out the whole configuration to be safe.

Inderpal Singh 2L

Na is to the left side of Cl on the periodic table. By making Na into Na+, you are losing an electron. Since the outermost electron was in the 3 state, by taking it away, the radius drops down to the 2 state/shell. Na was normally larger than Cl but by making it into an ion, it got smaller.

Inderpal Singh 2L

Hello, if a midterm question had an error in the actual question or answers, how would these be graded? One of my midterm questions had two of the same answers and it made me curious. Thank youuu

Inderpal Singh 2L

How many electrons in an atom could have these sets of quantum numbers?
n=3
n=5,ℓ=0
n=6,ℓ=2,mℓ=−1

Can someone explain how this is done/how to start it? I am very confused about orbitals and quantum numbers at the moment.

Inderpal Singh 2L

They have to be "uniform" throughout the whole wave. (same length wavelengths and amplitude). They also have to end where the beginning of the wave begins. Visualize it as putting multiple of these waves together, would they fit together like a puzzle piece? This was very hard to describe ...

Inderpal Singh 2L

Yes, I believe they are the same thing. Use kg for mass and m/s for velocity. Make sure to convert if not! :)

Inderpal Singh 2L

C will be equal to 3*10^8.

Inderpal Singh 2L

I believe that it only does apply to metal surfaces :) but I would double-check.

Inderpal Singh 2L

I've always rounded at the end. This is what my teacher in high school did as well.

Inderpal Singh 2L

I am personally going to familiarize myself with the spectrum. I feel like it will come in handy after the midterm as well :)

Inderpal Singh 2L

I had trouble with this as well, all you have to do is divide the total energy by the work function. Take into account what the problem might have already given you.

Inderpal Singh 2L

I personally am going to memorize a few of the common ones. However, I think it is best to check with the professor or TA just in case to make sure.

Inderpal Singh 2L

8.0 and 5.0. Remember that any zero's at the end of a number after a decimal point count as a significant figure :)

Inderpal Singh 2L

The equation applies to protons and neutrons as well I believe. Pretty much anything that is super small on a subatomic scale I believe.

Inderpal Singh 2L

I think Dr. Lavelle also mentioned in the lectures multiple times that we would not have to memorize any constants or equations. So I think we should focus more on the conceptual aspect of the material rather than actually memorizing anything.

Inderpal Singh 2L

He was trying to show all the other equations you could derive from E=m*c^2. This is similar to the equations we used in the photoelectric effect and how we would use what is given to us to answer a problem. Depending on what we are given, we can form different types of equations.

Inderpal Singh 2L

I believe you cannot see wavelengths that are smaller than about 10^-15 m.

Inderpal Singh 2L

This is the equation for the speed of light. It is used a lot in the equations revolving around the photoelectric effect :)

Inderpal Singh 2L

When a metal was exposed to photons at a frequency of 1.40×1015 s−1, electrons were emitted with a maximum kinetic energy of 3.30×10−19 J. Calculate the work function, Φ, of this metal. Φ =5.97×10^−19 J/photon What is the maximum number of electrons that could be ejected from this metal by a burst o...

Inderpal Singh 2L

Can someone explain where h (Plancks constant) comes from? I want to have a better understanding of why it is in the equation :)

Inderpal Singh 2L

Yes. When the amplitude increases, so does the number of photons.

Inderpal Singh 2L

Do we need to memorize the order of electromagnetic radiation in order of increasing energy?

Like placing the following in order: γ-rays, visible light, ultraviolet radiation, microwaves, x-rays.

Inderpal Singh 2L

Yes, that is correct. Since the interaction between photons and electrons is one on one, increasing the intensity will not affect whether or not the electrons would be ejected as only the number of photons is increased. In order for electrons to be ejected, it depends on the energy of the individual...

Inderpal Singh 2L

Yup, you are good. The stoichiometric coefficients are just there to create a balance between the two sides and don't actually go into the calculation.

Inderpal Singh 2L

I personally use the exact values provided on the periodic table and do not round until the very end of the problem. A scientific calculator should save all of your decimal points and use it later.

Inderpal Singh 2L

Based on what I learned from my chem teacher in highschool, we usually just went with the smallest number given to us in the actual problem.

Inderpal Singh 2L

A 1.50-g sample of metallic tin was placed in a 26.45-g crucible and heated until all the tin had reacted with the oxygen in air to form an oxide. The crucible and product together were found to weigh 28.35 g. (a) What is the empirical formula of the oxide? (b) Write the name of the oxide. Can someo...

Inderpal Singh 2L

I believe he was trying to make a point that not only do combustion, burning and oxidation have to do with the addition of O2 gas but that these types of reactions are exothermic. Exothermic means that the reaction is releasing energy.

Inderpal Singh 2L

If significant numbers are an issue for anyone, I studied the topic using mainly this image:

https://getstartedinscience.weebly.com/ ... orig.jpg?1

I think it really sums up everything simply and clearly :)

Inderpal Singh 2L

Similar to the other responses above, I use the largest amount of numbers to increase my accuracy. But then I would round down to the smallest amount of sig figs given within the actual problem. This may require you to use scientific notation to clean up the numbers. I am not sure how important sig ...

Inderpal Singh 2L

For anyone having trouble with significant figures, the following link is what I use if I ever get confused.

https://getstartedinscience.weebly.com/ ... orig.jpg?1

This summarizes the rules of significant figures pretty well :)

Inderpal Singh 2L

A good way to think of it is that the atoms of the products are created from the atoms of the reactants. They didn't just pop out of nowhere. (the atoms of the reactants are rearranged, bonded, etc. to become the products)

Inderpal Singh 2L

I started out with balancing the Fe, giving me: Fe3O4 + CO -> 3Fe + CO2. In an attempt to balance out the oxygens on both sides, I will add a 2 in front of carbon monoxide on the reactant side. This will give me: Fe3O4 + 2CO -> 3Fe + CO2. I will also add a 3 in front of the CO2 on the right in an at...

Inderpal Singh 2L

Can somehow please explain how the following is done: Practitioners of the branch of alternative medicine known as homeopathy claim that very dilute solutions of substances can have an effect. Is the claim plausible? To explore this question, suppose that you prepare a solution of a supposedly activ...

Inderpal Singh 2L

Since Empirical Formulas are ratios. Can empirical formulas ever be larger than the molecular formula? For instance, Glucose C6H12O6. Can the empirical formula be C12H24O6? I am guessing you would just simplify it down to C3H6O3.

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