Search found 33 matches
- Wed Jun 06, 2018 11:01 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: pH in changing temperature
- Replies: 4
- Views: 1142
Re: pH in changing temperature
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.
- Wed Jun 06, 2018 10:49 pm
- Forum: Amphoteric Compounds
- Topic: Identifying an amphoteric compound
- Replies: 3
- Views: 2932
Identifying an amphoteric compound
I know that an amphoteric compound has both acidic and basic characters, but can someone help me on how to identify them?
- Wed Jun 06, 2018 10:48 pm
- Forum: Lewis Acids & Bases
- Topic: Boron and the octet rule [ENDORSED]
- Replies: 7
- Views: 1530
Re: Boron and the octet rule [ENDORSED]
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...
- Thu May 31, 2018 10:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bent vs. Angular
- Replies: 11
- Views: 1165
Re: Bent vs. Angular
They are the same thing and can be used interchangeably.
- Thu May 31, 2018 10:32 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR Drawing
- Replies: 7
- Views: 809
Re: VSEPR Drawing
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.
- Thu May 31, 2018 10:29 pm
- Forum: Hybridization
- Topic: VSEPR
- Replies: 11
- Views: 1501
Re: VSEPR
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
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
- Thu May 24, 2018 12:31 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angle
- Replies: 10
- Views: 1139
Re: Bond Angle
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.
- Thu May 24, 2018 12:30 am
- Forum: Resonance Structures
- Topic: Resonance Structures
- Replies: 9
- Views: 1115
Re: Resonance Structures
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.
- Thu May 24, 2018 12:28 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: shape of water
- Replies: 8
- Views: 1165
Re: shape of water
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.
- Thu May 24, 2018 12:26 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR on test 3?
- Replies: 3
- Views: 481
Re: VSEPR on test 3?
Test 3 is on chapter 3 whilst VSEPR is Chap.4
- Fri May 18, 2018 3:36 pm
- Forum: Bond Lengths & Energies
- Topic: Bond Strength In Same Group
- Replies: 6
- Views: 2163
Re: Bond Strength In Same Group
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...
- Fri May 18, 2018 3:29 pm
- Forum: Coordinate Covalent Bonds
- Topic: Coordinate Covalent Bonds
- Replies: 4
- Views: 972
Re: Coordinate Covalent Bonds
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.
- Fri May 18, 2018 3:23 pm
- Forum: Ionic & Covalent Bonds
- Topic: Lewis Acids and Bases
- Replies: 4
- Views: 508
Re: Lewis Acids and Bases
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.
- Sun May 13, 2018 2:37 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal charges and full valence shells
- Replies: 3
- Views: 637
Re: Formal charges and full valence shells
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.
- Sun May 13, 2018 2:34 am
- Forum: Octet Exceptions
- Topic: expanded octet XeF4
- Replies: 8
- Views: 2158
Re: expanded octet XeF4
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...
- Sun May 13, 2018 2:31 am
- Forum: Octet Exceptions
- Topic: Exceptions [ENDORSED]
- Replies: 7
- Views: 1284
Re: Exceptions [ENDORSED]
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.
- Sun May 13, 2018 2:29 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal charge of ClO2- [ENDORSED]
- Replies: 4
- Views: 3168
Re: Formal charge of ClO2- [ENDORSED]
The least electronegative element is the central atom in the molecule. Cl is less electronegative than oxygen, therefore it will be the central atom.
- Thu May 10, 2018 12:24 am
- Forum: Ionic & Covalent Bonds
- Topic: Octet
- Replies: 7
- Views: 990
Re: Octet
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...
- Thu May 03, 2018 4:43 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Atom Size (Periodicity of Atomic properties)
- Replies: 2
- Views: 279
Re: Atom Size (Periodicity of Atomic properties)
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.
- Thu May 03, 2018 4:40 pm
- Forum: Trends in The Periodic Table
- Topic: electron affinity vs ionization energy
- Replies: 2
- Views: 1363
Re: electron affinity vs ionization energy
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...
- Thu May 03, 2018 4:28 pm
- Forum: Ionic & Covalent Bonds
- Topic: Octet
- Replies: 7
- Views: 990
Re: Octet
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...
- Wed Apr 25, 2018 8:28 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Negative signs
- Replies: 3
- Views: 397
Re: Negative signs
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.
- Wed Apr 25, 2018 8:07 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: d and s blocks
- Replies: 16
- Views: 2157
Re: d and s blocks
This is because we haven't found any new elements to fit levels after f.
- Wed Apr 25, 2018 8:03 pm
- Forum: DeBroglie Equation
- Topic: Calculating velocity
- Replies: 5
- Views: 585
Re: Calculating velocity
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.
- Wed Apr 18, 2018 8:11 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: The Negative Sign in En = -hR/n^2
- Replies: 5
- Views: 600
The Negative Sign in En = -hR/n^2
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?
- Wed Apr 18, 2018 8:07 pm
- Forum: Einstein Equation
- Topic: Combining E=hv and c=ƛv [ENDORSED]
- Replies: 7
- Views: 5302
Re: Combining E=hv and c=ƛv [ENDORSED]
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.
- Wed Apr 18, 2018 8:01 pm
- Forum: DeBroglie Equation
- Topic: 10^-18
- Replies: 3
- Views: 435
Re: 10^-18
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.
- Thu Apr 12, 2018 3:02 pm
- Forum: Properties of Light
- Topic: Clarification on Hz
- Replies: 5
- Views: 334
Re: Clarification on Hz
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)
- Thu Apr 12, 2018 2:48 pm
- Forum: Properties of Light
- Topic: Intensity in terms of Quantum Mechanics and Classical Mechanics
- Replies: 2
- Views: 1427
Intensity in terms of Quantum Mechanics and Classical Mechanics
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?
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?
- Thu Apr 12, 2018 2:40 pm
- Forum: Limiting Reactant Calculations
- Topic: Reactant vs. Reagent [ENDORSED]
- Replies: 23
- Views: 34555
Re: Reactant vs. Reagent [ENDORSED]
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...
- Fri Apr 06, 2018 9:36 pm
- Forum: Balancing Chemical Reactions
- Topic: How to know the state of the molecules [ENDORSED]
- Replies: 6
- Views: 815
Re: How to know the state of the molecules [ENDORSED]
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...
- Fri Apr 06, 2018 9:31 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Which mass of oxygen should be used? [ENDORSED]
- Replies: 23
- Views: 3248
Re: Which mass of oxygen should be used? [ENDORSED]
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...
- Fri Apr 06, 2018 9:24 pm
- Forum: Limiting Reactant Calculations
- Topic: Module 3: Limiting Reactant Calculations, Question 26 [ENDORSED]
- Replies: 4
- Views: 648
Re: Module 3: Limiting Reactant Calculations, Question 26 [ENDORSED]
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 ...