CHEMISTRY COMMUNITY

Steven Luong 1E

The pH of pure water decreases with increasing temp. If the pH falls and the temp is increased, water is still not acidic as the concentrations of H+ and OH- are the same pH = pOH.

Steven Luong 1E

I know that an amphoteric compound has both acidic and basic characters, but can someone help me on how to identify them?

Steven Luong 1E

You should think of the octet rule as one of several rules of thumb that will help you predict the electronic structure of atoms and their behavior. Another such rule is that atoms are generally more stable when they possess little or no charge. In the case of boron, these rules make competing sugge...

Steven Luong 1E

They are the same thing and can be used interchangeably.

Steven Luong 1E

On tests and exams, my TA said that you will need to draw ONLY the Lewis Structure and infer geometric information based on the formula. Since VSEPR requires 3D drawings we do not need to do it on neither tests or exams.

Steven Luong 1E

Valence - Shell - Electron - Pair - Repulsion Model
The formula for VSEPR is: AXE
A stands for the central atom
X stands for number of electron regions
E stands for lone pairs of electrons

Steven Luong 1E

There are a few relative numbers set for each shape. However, the correct bond angle is determined experimentally, so we do not have to remember them.

Steven Luong 1E

Resonance structures when drawn are generally the same with the differences being the location of the bond (i.e. single/double/triple). Formal charges should correspond to the element depending on the bond connecting it to the central element.

Steven Luong 1E

No. The shape of water is bent due to the 2 lone pairs repelling one another, pushing the O-H bonds down to form a bent shape.

Steven Luong 1E

Test 3 is on chapter 3 whilst VSEPR is Chap.4

Steven Luong 1E

The stronger bond is in the molecule with the more electronegative atom involved. For instance, the bonds in CCl4 are stronger than those of the CBr4 because Cl has a higher electronegativity than Br due to Cl's smaller size. Electronegative atoms hold electrons more tightly, thus increasing the str...

Steven Luong 1E

A coordinate bond (also called a dative covalent bond) is a covalent bond (a shared pair of electrons) in which BOTH electrons in one of the shared bonds come from the same atom.

Steven Luong 1E

That does not seem to be the case because all compounds both have ionic and covalent properties. The main differences so far is that acids accept electrons and bases give up electrons.

Steven Luong 1E

Formal charge is the relative charge of an atom relative to other atoms within the same molecule. Valence electrons just resemble outer electrons and may or may not be used up as bonds in the molecule; it is used for calculation of the formal charge.

Steven Luong 1E

Assuming you found the formal charges of both the normal structure and one with double bonds, the structure with 2 lone pairs (normal) will have a lower energy state than the one with double bonds, which is more appropriate. However, you can also explain this with the fact that Fluorine is in the 2n...

Steven Luong 1E

An exception may or may not exist once you go past the 2nd energy level into the 3rd and beyond. Since there exists the d orbital in the 3rd energy level, the atom can get more electrons as needed.

Steven Luong 1E

The least electronegative element is the central atom in the molecule. Cl is less electronegative than oxygen, therefore it will be the central atom.

Steven Luong 1E

An Octet means 8 valence electrons ==> Oct = 8, like Octopus with 8 tentacles. An atom, in order to be more stable, can have up to eight electrons in its valence shell. Noble gases (Neon, Argon, etc) have full shells of eight valence electrons each. This complete configuration allows stable gases t...

Steven Luong 1E

Like you said, the nuclear charge becomes higher across the period from left to right. The nuclear pull will overcome the repelling force of electrons and keep it in the shell.

Steven Luong 1E

Electron affinity is defined as the change in energy (in kJ/mole) of a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion. In other words, the neutral atom's likelihood of gaining an electron. Ionization energy is defined as the energy needed to remove o...

Steven Luong 1E

An Octet means 8 valence electrons ==> Oct = 8, like Octopus with 8 tentacles. An atom, in order to be more stable, can have up to eight electrons in its valence shell. Noble gases (Neon, Argon, etc) have full shells of eight valence electrons each. This complete configuration allows stable gases to...

Steven Luong 1E

Negative sign means that energy is being released. If you recall, if the change in energy is negative, that means energy is being released as photons, which is why when calculating wavelength and frequency you ignore the negative sign and utilize the positive value of delta e instead.

Steven Luong 1E

This is because we haven't found any new elements to fit levels after f.

Steven Luong 1E

Given the wavelength, this might be a De Broglie problem. Since Lambda-max = h/(mass x velocity), you should convert Lambda into meters and you are probably given a mass. The Planck's constant is h. Then just plug all the values in and solve for velocity.

Steven Luong 1E

Hello, the professor mentioned the negative sign in the aforementioned formula is due to the falling of the electron from a higher energy to a lower energy level in which energy is released as photons. Is this correct, or am I missing something as to why there exists a negative sign?

Steven Luong 1E

So we have E = hv, where h is Planck's constant and v is the frequency. We have c = ƛv where ƛ is the wavelength, c is the speed of light while v is also frequency. If we solve for v in c = ƛv we will get v = c/ƛ. Now we can plug that into E = hv where we will get E = hc/ƛ.

Steven Luong 1E

From my understanding, when the wavelength is smaller than 10^-18, it is so undetectable that the object should be considered a classical particle instead. For example, the car he mentioned cannot have wavelike properties whilst an electron can due to its minuscule size.

Steven Luong 1E

Yeah!! Hertz is the number of cycles per second. It is a cycle once a point repeats itself. (You can count the troughs and peaks but it is safer to use the start of the starting point of the cycle itself to count)

Steven Luong 1E

Hi everyone,

Professor Lavelle mentioned both intensity of light in terms of quantum mechanics and classical mechanics. I was not so sure how both of these are different from one another. Can somebody elaborate on their differences?

Steven Luong 1E

Hello, reagent is anything that can be used as a reactant. However, a reagent is not a reactant unless you choose to use it to create a reaction. A reagent is a reactant only when that reagent is being used to create the chemical reaction. For instance, c6h12o6 + o2 --> co2 + h2o(Not balanced). C6h1...

Steven Luong 1E

For these types of problems, you do not really need to know the states as the problems will have provided them to you and you do not need them to balance equations. If there is a solute in water solvent, that means it is aqueous (aq). If it is a solid (table salt NaCl) it will be (s). If it is gas l...

Steven Luong 1E

There are no differences, really. There are many versions of the periodic table; however, it is best to just follow the periodic table in our book, which is 16.00 g/mol, and Professor Lavelle uses that as well. Besides, after we take significant figures into account, the answer will most likely be t...

Steven Luong 1E

Hello, since you are given the moles and the molar mass which is g/mol or g mol^-1, you have to cancel units out using stochiometric ratios. In this case, it is 0.20 mols times 81 g/mol in which the mols will cancel out and you will be left with grams. The product of the two will be the theoretical ...

CHEMISTRY COMMUNITY

Search found 33 matches

Re: pH in changing temperature

Identifying an amphoteric compound

Re: Boron and the octet rule [ENDORSED]

Re: Bent vs. Angular

Re: VSEPR Drawing

Re: VSEPR

Re: Bond Angle

Re: Resonance Structures

Re: shape of water

Re: VSEPR on test 3?

Re: Bond Strength In Same Group

Re: Coordinate Covalent Bonds

Re: Lewis Acids and Bases

Re: Formal charges and full valence shells

Re: expanded octet XeF4

Re: Exceptions [ENDORSED]

Re: Formal charge of ClO2- [ENDORSED]

Re: Octet

Re: Atom Size (Periodicity of Atomic properties)

Re: electron affinity vs ionization energy

Re: Octet

Re: Negative signs

Re: d and s blocks

Re: Calculating velocity

The Negative Sign in En = -hR/n^2

Re: Combining E=hv and c=ƛv [ENDORSED]

Re: 10^-18

Re: Clarification on Hz

Intensity in terms of Quantum Mechanics and Classical Mechanics

Re: Reactant vs. Reagent [ENDORSED]

Re: How to know the state of the molecules [ENDORSED]

Re: Which mass of oxygen should be used? [ENDORSED]

Re: Module 3: Limiting Reactant Calculations, Question 26 [ENDORSED]