CHEMISTRY COMMUNITY

Isaac Wen

All Bronsted acids can be considered Lewis acids and all Bronsted bases can be considered Lewis bases. However, the opposite does not apply. Not all lewis acids and bases are Bronsted acids and bases. Basically, Lewis acids/bases are the more general terms.

Isaac Wen

I'm pretty sure BaO is a strong base. Can I ask where you saw that it was an acid?

Isaac Wen

I think pKa is a measurement that indicates the strength of an acid and is an inherent property (varies from compound to compound) while pH simply refers to the concentration of hydronium ions in a solution. When pH is less than pKa, the acid is protonated, meaning it's neutral. When pH is greater t...

Isaac Wen

Ahhh that makes a lot of sense. Thank you for your help!

Isaac Wen

Hi! In one of the lectures, Dr. Lavelle mentioned that Na+ and Cl- do not affect the pH of the solution they're in. Why is that? And if there's a rule that explains this phenomenon, can the same thing be applied to all Group 1 and Group 17 elements?

Isaac Wen

Is water always a product in neutralization? I'm looking at the answer key for textbook question J.9 part b and I'm really confused as to why there is no water on the right side of the chemical equation.

Isaac Wen

I look at the bond length between the atom connected to H. If it's longer then it that means the bond can be broken more easily, which means it's a stronger acid. I also look at the electronegativity of the atom connected to H.

Isaac Wen

I'm not entirely sure either, but I remember reading something about how if you're comparing elements down a column, bond length matters more whereas electronegativity matters more when comparing elements across a period.

Isaac Wen

Hello! Could someone please help explain to me the importance of delocalized bonds and how we are supposed to visually identify them in a given molecule? Delocalized bonds happen in resonance structures so if you know a compound/molecule has several possible structures, that might be an indication ...

Isaac Wen

If the pi bonds between the first two central carbon atoms are connected by two p orbitals in the x orientation, the pi bonds between the second and third central carbon atoms have to be connected by two p orbitals in either the y or z orientation. That is what accounts for the perpendicular plane. ...

Isaac Wen

For this question, I think you only have to address the pi and sigma bonds. But in other questions, the pi and sigma bonds might affect which plane the terminal atoms are in.

Isaac Wen

Compounds with 5 or 6 electron fields can be linear if they lose all the equatorial atoms! You can look at this diagram for reference!

Isaac Wen

I do not completely understand why the number is what it is on a hybridized orbital. For example, why is an sp3 hybridized orbital called an sp3 when it is made up of the 2s and 2p orbitals? An sp3 hybridized orbital only has one s orbital and 3p orbitals! So the numbers next to each orbital are ju...

Isaac Wen

The energy difference between the hybridized orbital and the unhybridized orbital explains why there isn't spin paired electrons. In the example, because the 2sp^2 hybridized orbital is closer in energy to the 2p orbital than the 2s is in that respect, there is going to be more electron repulsion, ...

Isaac Wen

Hi! I think you might be right in the sense that hybridization is indeed a mathematical model. However, it happens because, without it, a compound might have bonds of different energies. For instance, if we look at CCl4, carbon has 4 bonding electrons--2 from the 2s orbital and 2 from the 2p orbital...

Isaac Wen

I'm not entirely sure but I feel like the signs might be referring to the displacement of the electron waves. So when an electron in an orbital with a + sign meets another electron in an orbital with a + sign, constructive interference occurs. On the other hand, when an electron in an orbital with a...

Isaac Wen

Maybe he just accidentally wrote sp3 instead? I checked Google and also found that ethene has 2 sp2 orbitals.

Isaac Wen

Are all single bonds sigma bonds? If so, what is the difference between the two? Thanks!

Isaac Wen

Hi! If a compound has resonance (let's say it has bond lengths between a single bond and a double bond), would it have both a sigma bond and a pi bond just like a double bond would?

Isaac Wen

Yeah! Polarizability refers to the ability of an electron cloud to be distorted by an electric field. Elements with low electronegativity tend to "lose" their electrons, so it makes sense that they are more polarizable. Conversely, elements with high electronegativity tend to "hog&quo...

Isaac Wen

The favorable one will be the one lowest in energy and contributes the most to the resonance structure, but the other less-favorable arrangements do contribute as well (just not as much)!

Isaac Wen

I think it depends on the charge of the ion and dipole moment of the molecule involved in the ion-dipole interaction. So if an ion is highly charged and the net dipole moment of the molecule is also pretty significant, an ion-dipole might possibly be stronger than a hydrogen bond (and vice versa). I...

Isaac Wen

The dipole on the C atom points to Cl because Cl is much more electronegative!

Isaac Wen

Hi!

I'm a little confused about how bond strength relates to polarizability. Namely, if larger atoms have longer bonds and thus weaker bonds, how can they create larger London forces? Or am I confusing intramolecular and intermolecular bonds?

Isaac Wen

What makes BaBr2 have primarily ionic bonds and not the rest of them? Does the amount of Br have an effect on whether it has ionic or covalent bonds? I don't think the amount of Br matters, at least in this case. The bond between Ba and one Br should be the same as the bond between Ba and the other...

Isaac Wen

Hi! So problem 2c.3 part B wants us to draw Lewis structures for a hydrogen phosphate ion and the instruction manual shows four different structures (three with one double bond between O and P). My question is this: why can't we have three double bonds instead of only having one? The formal charges ...

Isaac Wen

Okay thanks!

Isaac Wen

So I know that elements from period 3 and beyond can have expanded octets, but how expanded can they be? Does it have to do with how many electrons are already in their d-orbital?

Isaac Wen

Quick question: does it matter if the H atom is above or below the N atom in the Lewis dot diagram for NHF2?

Isaac Wen

Hi!

Can someone explain why the electron configuration for Cu+ is [Ar]3d^10 instead of [Ar]3d^84s^2 and why for Ga3+ it's [Ar]3d^10 instead of [Ar]3d^84s^2? Thanks!

Isaac Wen

I also answered this on another person's post, but basically, Coulomb's equation measures the electrostatic force between two charged particles. The particles must be stationary for the equation to be accurate (that's why the measured force is called electroSTATIC). The greater the charge of the par...

Isaac Wen

It definitely helps to memorize them (honestly if you do a few problems, you'll remember it pretty easily). Note that the elements on the right side of the transition metals are missing fewer valence electrons to form a complete shell so they tend to gain electrons. The opposite can be said about el...

Isaac Wen

Coulomb's equation essentially measures the electrostatic force between two charged particles. It's called the electrostatic force because the equation only works if the two particles are stationary. The greater the charges, the greater the electrostatic force. The greater the distance between the t...

Isaac Wen

Normally for transition metals, you just have to look at the total charge of the anion and balance it out. For instance, le'ts look at Copper (II) Oxide. We know that the oxygen anion has a -2 charge, so in order to balance that out, Copper has to have a +2 charge.

Isaac Wen

Awesome thanks! And these are all based on experimental findings right?

Isaac Wen

Hi!

Can someone explain why 4s is sometimes written before 3d and why after Z=20, it's written after 3d?

Isaac Wen

Building off of what Siwa said, the electrons are actually losing energy while emitting light when they move down from a higher atomic level to a lower one. They are absorbing energy when they are moving from a lower level to a higher level. Also as a side note, when you're using the v= R (1/n1^2-1/...

Isaac Wen

To report the difference as a percentage of the wavelength of the neutron, use DeBroglie's λ=h/(mv) to first find the wavelength of the proton and neutron. Then, you want to subtract the wavelength of the neutron from the wavelength of the proton––and then divide that difference by the wavelength of...

Isaac Wen

We've been using grams in the previous chapter because molar mass is in g/mol. Now, since we're no longer dealing with molar mass, we use the standard SI unit, kg!

Isaac Wen

Hi!

I understand the nodal planes are regions where the likelihood of finding an electron is zero, but why is that important for us to know?

Isaac Wen

Hi Everyone! In the textbook, there was this analogy comparing Schrodinger's equation to a guitar string...I don't really understand it haha. Does anyone mind explaining? "Think of a guitar string: because it is tied down at each end, it can support only shapes like the ones shown in Fig. 1C.3,...

Isaac Wen

For a wave, the intensity is the amplitude (how tall the crest is). Frequency, as you described is the number of cycles per second. For a photon/particle, the intensity is the number of photons passing an area in a certain amount of time. Normally, increasing the intensity (amplitude) of a wave woul...

Isaac Wen

My TA said that we might have to know the shapes of each of the orbital? Don't know if that's true but I don't think it'll hurt to memorize the shapes of each orbital. That being said, it definitely won't be a focus of the midterm!

Isaac Wen

Hi!

I'm a little confused about Schrodinger's equation. Namely, how do we use it? Also, is it related to the 4 types of orbitals we learned yesterday?

Isaac Wen

Just out of curiosity, if the question were to replace 1s with another quantity of time, we just have to multiply the velocity we get by the quantity asked to find the wavelength right?

Isaac Wen

Hi everyone, What's considered the smallest measurable wavelength that would give wavelike characteristics to an object? I came across this question in one of the module assessments. 29. Calculate the de Broglie wavelength of a 0.155 kg ball travelling at 85.0 m.s-1. Can we detect this wavelength or...

Isaac Wen

A lamp rated at 32 W (1W = 1 J?*s^-1) emits violet light of wavelength 420 nm. How many photons of violet light can the lamp generate in 2.0 s? How many moles of photons are emitted in that time interval? I'm not completely sure how to do this problem. I'd greatly appreciate it if someone could ple...

Isaac Wen

We can translate the question into an equation: E (incoming photon) - Φ (Work Function) = Ek (outgoing). Basically, the E for incoming must be larger than the Φ in order for the electron to be ejected.

Isaac Wen

Hola Uyenvy hehe

It's C. Incoming, Large!

Isaac Wen

Hi! Here's the question: What is the minimum uncertainty in the speed of an electron confined within a lead atom of diameter 350. pm? Model the atom as a one-dimensional box with a length equal to the diameter of the actual atom. I was just wondering why 350.pm is the uncertainty in the position. I ...

Isaac Wen

Hi!

I was just wondering what exactly is the unit eV and why it's being used in many of the problems we see (instead of the SI unit J). How is it related to J and do we have to convert it to J every time we have to calculate something energy-related?

Isaac Wen

In question 3 of focus topic IA, I understand why options A,B, and D are wrong. However, I do not understand why C is correct. I am confused about how the extent of change in the electrical field relates to EM radiation. What is the "extent of change" referring to in the question? The wor...

Isaac Wen

Hi! This was a problem from one of the modules we completed before class started. I was just curious about how we should approach problems that involve first dissolving a solution and then diluting only a part of it. 5.00 g of KMnO4 is dissolved in a 150mL flask of water. If 20mL of this solution is...

Isaac Wen

I was confused on this one as well haha! I'm pretty sure the M in M(OH)2 just stands for the unknown metal, so essentially you can look at the formula as ?(OH)2. After that, it's like what they said, just find the molar mass of (OH)2 and subtract it from the given molar mass. Then you look at the pe...

Isaac Wen

Hi!

I think I've heard somewhere that formula units usually refer to ionic compounds while molecules refer to elements that are covalently bonded, if that helps.

Isaac Wen

ahh that makes a lot more sense bahaha. Thank you so much for the clarification!

Isaac Wen

Hi! The question goes like this:
The molar mass of the metal hydroxide M(OH)2 is 74.10g/mol. What is the molar mass of the sulfide of this metal?

Where did the sulfide come from? There's sulfide in M(OH)2???

Isaac Wen

Hi! I was working on E.9 from the fundamentals section and was just wondering if there's any way to remember how to convert compound names to their empirical formulas. The question asks you to write magnesium sulfate heptahydrate (Epsom salt) as a formula, but I unfortunately don't know how to do th...

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