CHEMISTRY COMMUNITY

Melody Haratian 1B

For acid/base equilibrium, do we only have to use ice tables to find the concentrations of the acid/base at equilibrium if the acid or base is weak? Why do we not use ICE tables if the acid or base is strong?
Thanks!

Melody Haratian 1B

When you’re finding equilibrium concentrations for an acid, do you always have to use Ka as its equilibrium quotient?

Melody Haratian 1B

Hi guys,
I’m having some trouble going through #5 on the acids/base sapling homework. The problem is:
The K_b for an amine is 1.118 * 10^-5. What percentage of the amine is protonated if the pH of a solution of the amine is 9.757? Assume that all OH^- came from the reaction of B with H₂O.

Melody Haratian 1B

If water was a liquid participating in a reaction but not the main solvent, would it still be included in the equilibrium equation for the equilibrium constant?

Melody Haratian 1B

Hi guys! When you’re calculating for equilibrium concentrations using ICE tables, when can you ignore the value of X in the denominator?

Melody Haratian 1B

When you add together two equilibrium equations, what happens to the equilibrium constants of the two equations?

Melody Haratian 1B

Can someone explain what happens when Q> K and Q< K?
I’m having a bit of trouble understanding the concept.
Thanks!

Melody Haratian 1B

Hi guys, I’m having trouble on the final part of #10 in the sapling homework. Can someone guide me through it? The problem is: The reaction N 2 O 4 <—> 2NO 2 is allowed to reach equilibrium in a chloroform solution at 25C. The equilibrium concentrations are 0.373 mol/L N 2 O 4 and 2.04 mol/L NO 2 . ...

Melody Haratian 1B

For endothermic reactions, how does K change when you add heat. How does K change when you add heat to exothermic reactions? Also, why does K change instead of Q when you add heat to the reaction.

Melody Haratian 1B

Hi guys! I’m having a lot of trouble getting started with the chemical equilibrium sapling HW, problem #4. The problem is: At a certain temperature, the given reaction has an equilibrium constant of K p = 329. PCl 3 + Cl 2 <—> PCl 5 PCl 5 is placed in a sealed container at an initial pressure of .07...

Melody Haratian 1B

Does changing pressure only cause a change in the reaction when the volume ( thus the concentration) is being changed?

Melody Haratian 1B

For the quick way shown in lecture #3, why does the reaction shift right when the volume decreases and there are more moles of gas on the left?

Melody Haratian 1B

If the value of K is in between 10^-3 and 10³ does equilibrium not sit towards the right or left? Where would we define equilibrium as going towards?

Melody Haratian 1B

Why doesn’t the value of K change when you change the concentration of the reactants or products?
Why does only temperature change K?

Melody Haratian 1B

Hi guys!
Do you use Q when you are unsure if the reactants/products are at equilibrium? Do you also use Q if the problem doesn’t explicitly state if the reactants and products have reached equilibrium?
Thanks!

Melody Haratian 1B

Hi guys!
I’ve been a little confused on this but for acids, are stronger acids more or less stable? Would electron withdrawing in an acid make it stable or not?
Thanks!

Melody Haratian 1B

Why is CH₂Cl₂ polar?
Can’t the C-Cl dipole bonds be opposite of each other and cancel each other out after having drawn the Lewis structure?

Melody Haratian 1B

Hi guys! While I was doing the homework I noticed some of the transition metals had different names than their chemical formula, like iron ( which was ferrate when written as part of the chemical formula of a coordination compound). Are there any specific metals we should know that will have differe...

Melody Haratian 1B

Hi guys!
Does anyone know what we should specifically know about acid rain? Do we have to understand the chemical formulas for different nonmetal oxides that react with H2O to produce acid rain?

Melody Haratian 1B

Since metal oxides ( with metals being from groups one and two) typically produce two moles of OH- for every oxygen atom they have in their chemical formula, would they be typically stronger than metal hydroxides?

Melody Haratian 1B

I was doing the sapling homework and was confused on why HCN is a weak acid instead of being a weak base. Since the nitrogen of HCN has a lone pair, I thought it would be a weak base since it can accept a proton from water. Can someone explain why it is a weak acid instead?
Thanks!

Melody Haratian 1B

For molecules with lone pairs of electrons on the central atoms, are they typically polar or nonpolar?
Is there a way to use the shape of molecules with lone pairs on the central atom to determine the polarity of the molecule?
Thanks!

Melody Haratian 1B

What ligands we should be familiar with or that we should memorize/ know the chemical formula for?
Thanks!

Melody Haratian 1B

Hi guys! I’ve been having trouble understanding this part of question 18 from the Week 7/8 homework. The question is “ A general formula for molecules of this type is H 2 C(C) x CH 2 , where x is a whole number.” Select the correct statement about the relationship of x to the orientations of the hyd...

Melody Haratian 1B

Hi guys!
Why do lone pairs of electrons on molecules occupy more space than bonded electrons?

Melody Haratian 1B

Hi guys!
I was doing the sapling HW for week 9 and got stuck on #5. What does the “en” in [Cd(en)Br₂] mean? Also, how would you find the coordination number for this molecule?
Thanks

Melody Haratian 1B

Hi guys!
For a molecule, if it had a single electron unbounded instead of a lone pair of electrons being unbounded, how big of an effect would that have on the molecule’s bond angles.

Melody Haratian 1B

Hello!
I don’t think those assignments are worth extra credit. I did them a while back, and they’re just to help you with the basics and getting used to using Sapling.

Melody Haratian 1B

Hi guys!
I was going over lecture #23 and had something I was a little confused on.
For the molecule Benzene (C₆H₆)
where is the electron for the un-hybridized p-orbital located? Also, is it delocalized?
Thanks!

Melody Haratian 1B

Hi guys!
I’m still a bit confused on this but can someone explain what makes a delocalized pi bond and what makes it different from a regular pi bond?

Melody Haratian 1B

Hi guys! I was doing the sapling Homework for week 7/8 and had trouble on number 17. The question is draw the three possible structures of C3H4 and the follow up question to it is to select the choice that contains all of the bond angles that are represented in the structures of C3H4. I was able to ...

Melody Haratian 1B

Can someone explain why CH₂Cl₂ is a polar molecule based on its molecular shape?

Melody Haratian 1B

Do ion-ion interactions have LDF forces?

Melody Haratian 1B

Hi guys!
I’m having a lot of trouble understanding why SO2 is a Lewis acid. Sapling says that it’s a molecule with a polar double bond but how does that help it accept more electrons?
Thanks!

Melody Haratian 1B

Hello! The stronger the intermolecular forces between the molecules, the higher the melting and boiling points will be. Vapor pressure refers to the amount of vapor released when a liquid turns into a gas. The more vapor released, the higher the vapor pressure. Weaker intermolecular forces have a hi...

Melody Haratian 1B

Hello! Cu is part of the exceptions in electron configuration. So its configuration for a neutral atom of Cu is [Ar]3d 10 4s 1 , because it prefers a full d shell. When Cu loses an electron, it will lose its outermost electron. In this case, its outer most electron is in the 4s shell ( since 4s 1 is...

Melody Haratian 1B

Hi! It’s possible for there to be an unpaired electron in a Lewis structure. When it happens the molecule is called a radical, because one of its electrons are unpaired and it’s highly reactive. An unpaired electron in a Lewis structure happens when there is an odd number of valence electrons when y...

Melody Haratian 1B

If there are many LDF interactions, can they become stronger than a dipole-dipole interaction?

Melody Haratian 1B

Hi guys!
Can someone let me know the order of intermolecular interactions from weakest to strongest?
I get them confused a lot of times.
Thanks!

Melody Haratian 1B

Hi guys! So covalent bonds are polar when the electrons are shared unequally and they’re nonpolar when the electrons are shared equally. Usually, how close do the atoms have to be in electronegativity for a bond to be considered nonpolar.
Also, are C-H bonds considered nonpolar?
Thanks!

Melody Haratian 1B

Hi guys! I’ve seen a couple of homework problems on oxidation numbers. Can someone explain what the oxidation number is and how you find it.
Thanks!

Melody Haratian 1B

Hi guys!
For a hydrogen atom, if you were to excite the electron so that it would go from 2s to 2p, would the energy of the electron change?
Thanks!

Melody Haratian 1B

Hi everyone!
Can someone explain why resonance structures are usually more stable? I’ve been having some trouble understanding this.
Thanks!

Melody Haratian 1B

Hi guys!
Do we need to know m_s to specify an orbital or do we only need to use the first three quantum numbers to specify the orbital?
Thanks!!

Melody Haratian 1B

Ion ion interactions are stronger because ions are fully charged. An example is NaCl, Na has a full +1 charge, and Cl has a full -1 charge. Ions are fully charged because the cation loses its electrons, and the anion gains electrons. These large and opposite charge values create a big attraction. T...

Melody Haratian 1B

Hello! For a radical, if an atom has an unpaired valence electron (or 7 electrons instead of 8) then it is a radical. You can tell if the valence electron is unpaired if one of its electrons is alone. So if an atom has or is sharing ( through covalent bonds) 6 electrons and has one additional unpair...

Melody Haratian 1B

Ion ion interactions are stronger because ions are fully charged. An example is NaCl, Na has a full +1 charge and Cl has a full -1 charge. Ions are fully charged because the cation loses its electrons and the anion gains electrons. These large and opposite charge values create a big attraction. The ...

Melody Haratian 1B

Hi guys! I was working on some formal charge problems and had a quick question. When calculating formal charge, would an molecule with a charge of +2 be more stable if all of that charge was on one atom of the molecule, or would it be more stable if the charge was separated on two atoms, each with a...

Melody Haratian 1B

I was watching Dr.Lavelle’s lecture from last Friday. What does polarizable mean and what does it mean for something to be highly polarizable?
Thank you!

Melody Haratian 1B

Hi guys! For problem 2B.part (c) I was wondering how you would know the order of the atoms when drawing the Lewis structure of the molecule. There’s a lot of different atoms in this molecule, and I’m a little confused on how to order them. Here’s the problem: “ Draw the complete Lewis structure of t...

Melody Haratian 1B

Hi everyone! For question 2B.5 part b from the textbook, which is “ Draw the Lewis structure of (b) hypobromite ion BrO-“ I was wondering why the structure doesn’t have a double bond instead of the single bond it’s shown to have in the answer key.

Melody Haratian 1B

Does the atomic radius increase when you go from 2s to 2p?

Melody Haratian 1B

I was working on the homework and some electron configurations had electrons in the f state. Do we have to know how to write electron configurations using the f- orbitals?

Melody Haratian 1B

Hi guys!
I was watching lecture #14 and I noticed that nitrogen was used as the central atom. I thought oxygen was an exception in ionization energies, so it would have a lower ionization energy than nitrogen due to its electron-electron repulsions. Why is nitrogen used as the central atom?

Melody Haratian 1B

Hello! Oxygen will also have a lower first ionization energy than fluorine because of fluorine’s higher atomic number. Because fluorine has a higher atomic number, it has more protons, thus a higher effective nuclear charge. This positive nuclear charge will attract electrons more, and result in a h...

Melody Haratian 1B

Hello! When there are zero electrons occupying the 3d orbitals, 4s will have a lower energy than 3d. This means that 4s will go after 2p when writing electron configurations. However, when electrons begin to fill the 3d orbitals, then 4s will have the higher energy than 3d. Therefore, 4s will be wri...

Melody Haratian 1B

Hello! The second ionization energy is higher than the first one because it becomes harder to remove a second electron from an atom after you have already removed the first one. You will need more energy to remove a second electron, thus resulting in a higher second ionization energy. Atoms do not w...

Melody Haratian 1B

Hi guys! I have a couple of questions about ionization energies. Would there be any other exceptions that we have to know other than oxygen for ionization energy trends? Are there any other exceptions due to electron repulsions for the typical ionization energy trend?
Thanks

Melody Haratian 1B

Hi!! Happy Halloween!!
My family and I dressed up and are watching some Halloween themed movies together. We also ordered food tonight and bought some candy!

Melody Haratian 1B

Hi everyone!
The atomic radii increases down a group and decreases across a period. I was wondering, which one has a greater effect on the atomic radii? Does going down a group increase the atomic radii more than going across a period would decrease the atomic radii?
Thanks!

Melody Haratian 1B

Hi everyone!
Just to clarify, is the 4s higher than energy than the 3d orbital? It’s energy was mentioned in lecture a couple of times, but I’m a little confused.
Thanks

Melody Haratian 1B

Hi everyone! I need a bit of help on 1D.13 part (a) and part (b). The problem states “(a) How many values of the quantum number l are possible when n=7? (b) How many values of m l are allowed for an electron in a 6d-subshell?”. Does anyone know how to get started on this problem, or any strategies o...

Melody Haratian 1B

Hi everyone! We use De Broglie’s equation to find the wavelength of an object with mass. After finding that wavelength, is there any way to convert it into frequency. Can the E = hv equation be used or not since its an equation only for electromagnetic radiation? Is there any other equation that can...

Melody Haratian 1B

Hi! For the elimination process, the answer cannot be A since the speed of radiation will always be equal to the speed of light ( 3 * 10 8 m/s ). The answer cannot be B since wavelength and frequency are inversely proportional, so wavelength will increase when frequency decreases. The answer cannot ...

Melody Haratian 1B

Hi! They derived that equation by using these two equations: 1. E= hv 2. c = λv you can find what frequency is equal to from the speed of light equation. Rearrange c = λv so that it becomes v = c/λ . Then, you can plug this into the v of the energy of a photon equation. So E = hv will become E = hc/...

Melody Haratian 1B

Hi! You can convert MHz to Hz by multiplying MHz by 10⁶. So 300 MHz * 10⁶ would be the amount of MHz in Hz.

Melody Haratian 1B

Hi everyone! I’m having trouble with problem 1 B.27 in the textbook. The problem is “ A bowling ball with a mass 8.00 kg is rolled down a bowling alley lane at 5.00 ± 5.0 m/s . What is the minimum uncertainty in its position?” Can someone help me with the first step of getting started with this prob...

Melody Haratian 1B

Hi everyone!
I have a couple of questions about light and De Broglie.
How does light have a momentum if it doesn’t have a mass? Can light be used in the De Broglie equation if its momentum is given, or can it not be used because light doesn’t have a mass?
Thank you!

Melody Haratian 1B

I think knowing the SI unit conversions of:
Kilo= 10³
Centi=10^-2
Milli=10^-3
Micro=10^-6
Nano=10^-9
Angstrom=10^-10
Will be very useful for the exam. The other conversions needed ( from eV to Joules, etc..) are on the formula sheet.

Melody Haratian 1B

Hi everyone!
I‘m reviewing schrodinger’s equation but I’m having trouble understanding some key parts of the equation What is a wave function and how does it relate to the electron? Also, what does Dr. Lavelle mean by a change in the wave function?

Melody Haratian 1B

Hi everyone!
In the audio visual about the wave properties of electrons, diffraction is mentioned multiple times. I’m a little confused about what diffraction means. What is diffraction and how does it relate to the properties of electrons?
Thank you!

Melody Haratian 1B

It’s on CCLE. Go to site info and scroll all the way down to the bottom of the page. There will be a link there allowing you to download respondus.

Melody Haratian 1B

Thank you so much! Everything’s a lot clearer now for me.

Melody Haratian 1B

Hello! The line will fall into the UV radiation spectrum making it a part of the Lyman series.The wavelengths of the Balmer series are much larger ( around 400-700 nm). What you should do next is find the frequency of atomic hydrogen by plugging in the wavelength into the c = λν. After finding the f...

Melody Haratian 1B

Hi everyone! I was reading the textbook Focus 1. A and looking at the definitions of the Balmer series and Lyman series. The textbook says that the “Balmer series consists of the lines with n 1 =2 (and n 2 =3,4,...). The Lyman series is a set of lines in the ultraviolet region of the spectrum with n...

Melody Haratian 1B

Can someone explain what electron diffraction ( option B) is from Problem 1B.3? Problem 1B.3 in the textbook: From the following list of observations, select the one that best supports the idea that electromagnetic radiation has the properties of particles. Explain your reasoning. A. Black-body radi...

Melody Haratian 1B

The extent of change refers to the wave’s steepness, or slope. It portrays how much a wave changes over time. The steeper, the higher the extent of change. When you reduce the frequency of a wave, you’re increasing its wavelength. Increasing the wavelength decreases the slope of the wave. Thus, you’...

Melody Haratian 1B

I’m having a lot of trouble getting started with problem 1A.15 from the textbook. The problem is: “ In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that lea...

Melody Haratian 1B

When you divide the speed of light which has units of meters per second (m/s), by hertz which has units of 1/seconds (s^-1 or 1/s), the seconds will cancel out and you’ll be left with meters. To convert the number you have in meters to nanometers, multiply by 10^9.

Melody Haratian 1B

Hello everyone! I was watching the photoelectric effect video module and had some questions after watching it.
What’s the difference the intensity of light and its frequency? Also, what happens when you change the intensity of light vs. when you change its frequency? Thank you!

Melody Haratian 1B

Hi! There are different approaches you can take when balancing a chemical equation. There cannot be different answers to a balanced chemical equation. The most simplified form of the balanced chemical equation is its correct form. To balance a chemical equation I first count the number of atoms of e...

Melody Haratian 1B

After you find the mass of the 2-butanone, find the number of moles of the 2-butanone by dividing the mass by its molar mass. The molar mass of 2-butanone is 72.1 g/mol. The number of moles of 3-methyl-3-hexanone is equal to the number of moles of the 2-butanone. Using the molar mass of the 3-methyl...

Melody Haratian 1B

Hi! Oxide is usually used to name a compound that has an oxygen in it. Since the compound is boron oxide, it has both boron and oxygen in it. Using the periodic table, we see that boron has a charge of 3+ while oxygen has a charge of 2-, so we need 2 borons and 3 oxygens to have a balanced compound....

Melody Haratian 1B

I watched the additional videos they were helpful in preparing me for the photoelectric effect and atomic spectra video modules. They review the different properties light has and help transition me into the next topic.

Melody Haratian 1B

I also got 4 sig figs which counts the 3204.

Melody Haratian 1B

^^ I also used N2 gas while doing my calculations. N2 is likely the product since it is diatomic and the form typically found in nature.

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