CHEMISTRY COMMUNITY

derickngo3d

The reaction graph helps a lot!
Hope this helps!

derickngo3d

The rev means that only the heat of a reversible reaction can be used in this equation when calculating delta S, the entropy change.
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derickngo3d

If the compound is an intermediate, it cannot be in the rate law.
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derickngo3d

If the compound is both a reactant and product in the individual steps of the reaction mechanism, it is an intermediate.
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derickngo3d

A bomb calorimeter is the best simulation of a perfect system.
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derickngo3d

Kinetically stable substances cannot overcome the activation energy and cannot react.
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derickngo3d

If delta G is negative, then the reaction is thermodynamically unstable.
Hope this helps!

derickngo3d

HClO is an intermediate reactant, so you can't have it in the rate law.
Hope this helps!

derickngo3d

That's a weird textbook question, but I think it's talking about temperature dependence in two ways. For Enaught, it's saying that it is only true at one temperature (STP), while for E, it's saying that it can change based on the temperature.
Hope this helps!

derickngo3d

You can either memorize or just mathematically calculate the units too!
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derickngo3d

A bomb calorimeter is an isolated system that cannot exchange matter or thermal energy with its surroundings!
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derickngo3d

I don't think either one is more preferred than the other!
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derickngo3d

Yes! The anode is always oxidized, and the cathode is always reduced!
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derickngo3d

Also, don't forget to cancel out intermediates by substituting equivalents reactants and products!
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derickngo3d

The slow step is rate-determining because it's like assembling a computer. If you need one screen and 40 keys for the keyboard, if the slowest step is producing the 40 keys for the keyboard, then that's as fast you can make computers.
Hope this helps!

derickngo3d

I don't think there are any other ways to impact the rate constant!
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derickngo3d

I second what the person above me said. And yes, stoichiometric coefficients are tempting to include in electromotive force calculations!
Hope this helps!

derickngo3d

The pseudo rate constant makes it easier to determine a rate constant or reaction rate, since one concentration changes so little that it is negligible.
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derickngo3d

Units for the rate constant should cancel with the units of molarity, so that the rate constant is in molar per second.
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derickngo3d

Platinum is the electrode when there is no metallic electrode present to conduct the electric current.
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derickngo3d

For strong acids, it's easiest to memorize the few strong acids, and assume all other acids are weak.
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derickngo3d

Be careful about the difference between k and K though.
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derickngo3d

If K is a large value, then products are favored.
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derickngo3d

The half-reaction that has a lower standard reduction potential will be oxidation, so that one should be on the left. The higher standard reduction reaction should be on the right, since it is reduction.
Hope this helps!

derickngo3d

For a and b, you can simply use the fact that they are exponentials of the half life, which is 1/2 of the value of the initial concentration. So 1/16 would be (1/2)^4. So multiply the half-life in seconds by 4.
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derickngo3d

Yep that answer is correct!

derickngo3d

It is really helpful to look at the reaction enthalpy graph. The activation energy is the height of the mountain, and the change in enthalpy is the difference between the starting and final enthalpy.

derickngo3d

Just remember what you're asked for, and in what units.

Hope this helps!

derickngo3d

Usually, look for whetehr Joules are used in the question, and that would mean that you would use 8.314 J/(K x mol.)

derickngo3d

This equation is for irreversible expansions only, which occurs at constant pressure.

derickngo3d

Usually, the rate law given would not match the elementary reaction, and this would indicate the presence of intermediate.

derickngo3d

It’s always positive, since if the reaction begins with only reactions, this is the only direction the reaction can go in.

derickngo3d

yes, the universe has such a massive volume that the change is negligible.

derickngo3d

When you hear weak something, think of an ICE table.

derickngo3d

Weak acids and bases do not completely dissociate, and ICE tables allow us to quantify just how much they do dissociate. Strong acids and bases dissociate completely, so while you could technically use an ICE table for them, it's not necessary and is overly tedious.

derickngo3d

I agree, use q=mcdeltaT.

derickngo3d

Work done by the system is exothermic, while work done ON the system is endothermic, from the system's perspective.

derickngo3d

Negative means exothermic, positive means endothermic.

derickngo3d

An inert gas is a member of the noble gases.

derickngo3d

for Kc or Kp, the values should all be concentrations or partial pressures, respectively.

derickngo3d

Based on the units, goose the appropriate gas constant-value.

derickngo3d

Also, reversible reactions can be reversed simply by undoing what was done to cause the initial change. So, like the other student’s example, if one pebble was removed to facilitate the change in equilibrium, one can simply put the pebble back to reverse the change in equilibrium.

derickngo3d

Also, my grade had been 5/5 as of yesterday, but it has since changed.

derickngo3d

Hey everyone, I was wondering if anyone has the same issue with grading on the Week 1 sapling assignment? Mine says that I have completed the assignment and denotes a 100% at the top left, but has for some reason cleared my submission for one of the questions. Despite the 100% grade on sapling, on m...

derickngo3d

The higher the Ka-value, the stronger the acid.

derickngo3d

The change in concentration which is the value of x is so minuscule that it can be approximated.

derickngo3d

The K-value is less than 1.0 x 10^-3.

derickngo3d

If the K value is less than 1.0 x 10^-3, then the x can be dropped.

derickngo3d

I also believe that density is just supposed to be positive, so the enthalpy would follow.

derickngo3d

6CO2(g) + 6H2O(l) -> C6H12O6(aq) + 6O2(g)

The question asks what happens when you add water. The textbook answer is that nothing changes - can anyone explain this please? Thank you!

derickngo3d

The ratio is always 1:1, so exponents are not needed in the Kw problems!

derickngo3d

Yep, that’s correct! That analysis works for all equilibrium reactions!

derickngo3d

In equilibrium reactions, there’s so much of these pure substances that their concentration doesn’t really change.

derickngo3d

I think that’s a typo in the book, it’s impossible to get a positive pH if the H3O+ concentration is greater than 1.

derickngo3d

The concentration of water is negligible because there’s so much of it. Picture it this way: there’s a sandbox filled with sand, and you drop a few marbles into it. The concentration of marbles has changed significantly, so it should be considered mathematically. The concentration of the sand really...

derickngo3d

Q is where the reaction is right now (not necessarily at equilibrium) whereas the K value is always the ratio of products divided by reactants at equilibrium. If Q is greater than K, than think of it like this: K is the ideal ratio, but since Q is to large, this means that there are to many products...

derickngo3d

The aqueous substances have significant and measurable changes in concentration, whereas the solvent water is present in such a high amount that the change is negligible.

derickngo3d

Think of it like this: if a reaction is endothermic, meaning it absorbs energy (so energy is a reactant), the reaction shifts as follows: if the temperature increases, the reaction shifts away from the energy “reactant”, so it shifts towards the products and to the right. Vice versa if the temperatu...

derickngo3d

Another thing to notice is that if you begin a reaction with only products, then the reaction must proceed towards the reactants. So, the reactant(s) should get a +x.

derickngo3d

Pure substances and solvents are not included in ICE tables.

Hope this helps!

derickngo3d

A coordination compound can have several types of ligands.

derickngo3d

Polydentate ligands can use several atoms to bond to a central transition metal atom.

derickngo3d

I wouldn’t think it’s necessary to memorize en and dien.

derickngo3d

An amphoteric substance must be able to act as an acid and a base.

derickngo3d

90 degrees between the atoms.

derickngo3d

pH goes from 0-14.

derickngo3d

The Roman numeral is the oxidation state and the charge of the transition metal. This charge, when added to the charges of the ligands, should cancel out with the anionic charges, or make the entire molecule the correct charge.

derickngo3d

En is short for ethylenediamine, a bidentate molecule.

derickngo3d

The oxidation state of an ion is the charge of that ion. Hope this helps!

derickngo3d

The ligands go in alphabetical order.

derickngo3d

Br3- is bromide.

derickngo3d

Yes, the interaction of the polar bonds determines the polarity of the molecule. Hope this helps!

derickngo3d

In CO2, the dipoles are directly opposite of each, so they cancel out, so the molecule is nonpolar.

derickngo3d

Dr. Lavelle said either one is okay. Hope this helps!

derickngo3d

Regardless of bond order, all covalent bond are one region of electron density. Lone pairs also count as regions of electron density.

derickngo3d

That is a bent shape.

derickngo3d

This depends on the intermolecular forces or IMFs.

derickngo3d

Chromium and copper are the typical exceptions to the the general electron configuration rules.

derickngo3d

Either sp3d or dsp3 is correct.

derickngo3d

In a bent molecule like water, the molecule is bent. So, the dipoles don’t cancel out, since the molecule is asymmetric. Hope this helps!

derickngo3d

For this problem, it says to find the metal ion M3+ that has the ground-state electron configuration [Ar] 3d6. isn't it an oxymoron to discuss the ground-state electron configuration of an ion? According to the textbook answers, the element is Co3+, which implies that this answer choice is the confi...

derickngo3d

A triple is one sigma and two pi bonds.

derickngo3d

Octet rule comes first.

derickngo3d

Oh I see, thank you!

derickngo3d

I forgot to note that the textbook says the answer is 6 valence electrons.

derickngo3d

So for the ion Co+3, one would "remove" the 4s2 electrons, then remove one from the 3d orbital, leaving you with 3d6. It asks for the number of valence electrons, but since there are no longer any electrons in the 4th shell, does that mean the number of valence electrons is now 14? (3s2 + ...

derickngo3d

Polyatomic ions are molecules whose atoms give the entire molecule a charge.

derickngo3d

I don't think we can see our answer choices, unfortunately!

derickngo3d

Yeah, I think this is the case for Group 13 elements.

derickngo3d

I would say it'd be reasonable to have to know this. Just in case this is what you're confused about, the Roman numeral signifies the charge of the metal, since they are transition metals that can often have different charges. If the transition metal is +4, and your anion is chlorine, then you would...

derickngo3d

I think oxygen can have up to four bonds, since it is not an exception to the octet rule.

derickngo3d

I think Dr. Lavelle told us he'd accept both, but the long-hand version is preferred.

derickngo3d

I like to sit in my backyard and play Clash Royale lol.

derickngo3d

I can't offer much as to the mechanics behind it, but I can discuss what it is. The Pauli Exclusion Principle states that no two electrons can have the same set of 4 quantum numbers. It comes down to m s , the spin of the electron. They can have the same n (same energy level), the same l (relates to...

derickngo3d

That noble gas configuration starts with [Kr], which is up to the 4th period. Then, following the convention that the d-orbital in the next period comes before the s-orbital (4d10 5s2), you just work your way across the next period.

derickngo3d

Hopefully Friday (today)!

derickngo3d

I usually apply sig figs at the end of the problem.

derickngo3d

Intensity of light is the number of photons. Frequency relates to a single photon, and whether it can eject electrons off of metal.

derickngo3d

Yep, 10^-15 meters is what Dr. Lavelle said.

derickngo3d

It provides the noble gas configuration.

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