Search found 100 matches
- Fri Mar 12, 2021 7:28 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 490
- Views: 513211
Re: Saying Thank You to Dr. Lavelle
Thank you for being my UCLA professor, Dr. Lavelle. You've made chemistry such an interesting subject for me to explore and you dedicate so much time into helping us do well. You're an inspiration for me to advance deeper into the fields of science. :)
- Fri Mar 12, 2021 7:23 pm
- Forum: Zero Order Reactions
- Topic: kind of reaction
- Replies: 25
- Views: 1085
Re: kind of reaction
Zero order means that even if you add more reactant, the rate will stay the same.
- Fri Mar 12, 2021 7:21 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Clarification on pKw
- Replies: 15
- Views: 3638
Re: Clarification on pKw
Speaking on STP, yes the Kw is always 14
- Fri Mar 12, 2021 7:20 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pka vs ka
- Replies: 28
- Views: 1255
Re: pka vs ka
Its basically the same as adding pH and pOH to get 14. The logarithmic properties allow you to add the pKa and pKb values to get pKw. But the concentrations themselves must be multiplied.
- Fri Mar 12, 2021 7:18 pm
- Forum: Ideal Gases
- Topic: R ideal gas constant
- Replies: 31
- Views: 1957
Re: R ideal gas constant
It all depends on what values are present in the problem. The constant aims to cancel out most of them
- Sun Mar 07, 2021 3:17 pm
- Forum: Student Social/Study Group
- Topic: Final Study Tips!
- Replies: 38
- Views: 2030
Re: Final Study Tips!
Outlines and sapling review problems are very useful
- Sun Mar 07, 2021 3:16 pm
- Forum: General Rate Laws
- Topic: Determining # order
- Replies: 5
- Views: 322
Re: Determining # order
Add the order numbers of the reactants to get the order of the reaction.
- Sun Mar 07, 2021 3:12 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated Systems
- Replies: 15
- Views: 775
Re: Isolated Systems
The bomb calorimeter is an example of a real isolated system. But I doubt it is a completely perfect system.
- Sun Mar 07, 2021 9:30 am
- Forum: General Rate Laws
- Topic: Order of a reaction
- Replies: 10
- Views: 609
Re: Order of a reaction
Like the previous reply mentioned, its based on experiments. If you refer back to Lavelle's monday week 9 lecture, he shows how experimentation determines the order of the reaction.
- Sun Mar 07, 2021 9:28 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Solids and Liquids?
- Replies: 26
- Views: 1300
Re: Solids and Liquids?
Gases are applied to this law only
- Sat Feb 27, 2021 8:10 pm
- Forum: Student Social/Study Group
- Topic: Final Jitters
- Replies: 457
- Views: 333923
Re: Final Jitters
Deep breaths. As long as you know you've done your best within the quarter to learn the material, you should be able to achieve peace of mind before, during, and after the exam.
- Sat Feb 27, 2021 8:06 pm
- Forum: Balancing Redox Reactions
- Topic: Week 7/8 Sapling PSA
- Replies: 4
- Views: 266
Re: Week 7/8 Sapling PSA
I've been having similar problems trying to complete it as well. Thanks for the tip!
- Sat Feb 27, 2021 8:02 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Bomb Calorimeter
- Replies: 14
- Views: 4544
Re: Bomb Calorimeter
It would be safe to assume that a bomb calorimeter is a near perfect system because of its incredibly insulated and protective mechanisms.
- Sat Feb 27, 2021 8:00 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Reversing Half Reactions
- Replies: 4
- Views: 213
Re: Reversing Half Reactions
Reverse the lesser value. Your overall voltage can never be negative.
- Sat Feb 27, 2021 7:57 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridges
- Replies: 41
- Views: 2921
Re: Salt Bridges
As the charge begins to build up, the cathode gets more negative and repulsion starts to take place when more electrons attempt to enter. By using a salt bridge, some ions can move from the cathode to the anode and allow for more electrons to be transferred.
- Sat Feb 27, 2021 7:49 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Acidic Versus Basic Solutions
- Replies: 20
- Views: 859
Re: Balancing Acidic Versus Basic Solutions
The acidic solutions includes H+ in the equations to balance it, while basic solutions include OH-
- Sat Feb 27, 2021 7:47 pm
- Forum: Balancing Redox Reactions
- Topic: Determining which molecule is the oxidizing agent
- Replies: 49
- Views: 1758
Re: Determining which molecule is the oxidizing agent
The oxidizing agent is the one that is being reduced. It takes the electron and oxidizes the element, which makes it the oxidizing agent.
- Sat Feb 27, 2021 12:11 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: anode / Cathode
- Replies: 9
- Views: 570
Re: anode / Cathode
I think of the anode as negatively charged which is giving electrons to the more positively charged cathode. So the anode is becoming positive while the cathode is becoming negative with the movement of electrons, If that makes sense. Thats how I interpret it at least.
- Sat Feb 27, 2021 12:07 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation vs Reduction
- Replies: 30
- Views: 1256
Re: Oxidation vs Reduction
Oxidation is becoming positive by losing electrons, reduction is becoming negative by gaining electrons.
I use LeO says GeR like the previous post mentioned as well. All it comes down to is practice.
I use LeO says GeR like the previous post mentioned as well. All it comes down to is practice.
- Sat Feb 27, 2021 12:03 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation Numbers
- Replies: 30
- Views: 1226
Re: Oxidation Numbers
Knowing the oxidation numbers of common elements would be useful, but I don't think you'll need to know all of them
- Sat Feb 13, 2021 10:17 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Temperature and Volume
- Replies: 10
- Views: 508
Re: Temperature and Volume
Greater temperature and greater space allows more possibility for disorder, which increases entropy. The opposite of both of these states will decrease it.
- Sat Feb 13, 2021 12:14 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Entropy
- Replies: 27
- Views: 1046
Re: Entropy
Its classified as disorder regarding number of possible varying positions it can be in
- Sat Feb 13, 2021 12:11 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Bomb Calorimeter
- Replies: 17
- Views: 746
Re: Bomb Calorimeter
They are closed, insulated environments. I would say theyre always isolated.
- Sat Feb 13, 2021 12:08 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Free Energy
- Replies: 49
- Views: 1884
Re: Free Energy
State functions are primarily focused on start and end states. The "path" taken is irrelavent.
- Sat Feb 13, 2021 12:04 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Kelvin conversion
- Replies: 40
- Views: 2871
Re: Kelvin conversion
Kelvin and celcius are essentially the same in terms of their step size (+5 C° also means +5° K exactly). The only difference is that they are about 273 units apart. So to calculate from C to K, just add 273.
- Fri Feb 05, 2021 2:09 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Work Definition
- Replies: 33
- Views: 1031
Re: Work Definition
An easy way to distinguish these terms is by understanding what they represent. Enthalpy is a value which measures the energy in a system. That energy can be transferred to another system by means of 'heat' and/or 'work.' Energy transfer through means of heat is done where the system releases energy...
- Fri Feb 05, 2021 2:01 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Work
- Replies: 39
- Views: 1387
Re: Work
Negative means it 'releases' to its surroundings while positive means it 'absorbs' from its surroundings. That's how I try to remember these types of things in thermodynamics.
- Fri Feb 05, 2021 1:59 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed Systems
- Replies: 14
- Views: 567
Re: Closed Systems
Closed system means that you cannot add anything else in it, as in other chemicals. But I believe a piston adding pressure to a system still counts as a closed system since no other matter is being added.
- Fri Feb 05, 2021 1:57 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Heat Change conceptual question
- Replies: 9
- Views: 551
Re: Heat Change conceptual question
Yes, a negative change in heat (- delta H), means that heat is released from the system and into the environment. The opposite occurs when there is a positive change in heat. Enthalpy and change in heat generally mean the same thing.
- Fri Feb 05, 2021 1:54 pm
- Forum: Ideal Gases
- Topic: Gas Constant Value
- Replies: 43
- Views: 1424
Re: Gas Constant Value
It all depends on the problems. Some discuss certain units so you would use the constant that include those said units.
- Thu Jan 28, 2021 7:05 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Water as a Reactant
- Replies: 9
- Views: 355
Re: Water as a Reactant
When dealing with equilibrium equations, water is always the solvent, so H2O is always removed from the equilibrium equation. If you remember from one of Lavelle's lectures, the 'concentration of water in water' is 55.5 mol/L which is wayyy larger than any concentration of acid or base that we deal ...
- Thu Jan 28, 2021 6:55 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: x is less than 5% of initial concentration
- Replies: 4
- Views: 224
Re: x is less than 5% of initial concentration
You should check it everytime. It only takes a second to divide and find out. Better to be safe than sorry.
- Thu Jan 28, 2021 6:53 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook 5G.1
- Replies: 3
- Views: 96
Re: Textbook 5G.1
The main rule is that K can never be changed except for temperature, so that statement would certainly be false.
- Thu Jan 28, 2021 6:51 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Acids and Bases List
- Replies: 4
- Views: 141
Re: Acids and Bases List
Unfortunately you need to memorize the strong acids and bases. There is only several of each. Any other acid/base that you come across that isn't part of that 'strong' should automatically be deemed weak.
- Thu Jan 28, 2021 6:41 pm
- Forum: Ideal Gases
- Topic: pv=nRT
- Replies: 16
- Views: 510
Re: pv=nRT
It should be important to know the relationships between pressure, temperature, and volume as well as being able to find each variable (including moles) by using this equation.
- Sat Jan 23, 2021 9:34 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Telling Between Salts and Acids/Bases
- Replies: 3
- Views: 206
Re: Telling Between Salts and Acids/Bases
Simply put, an ionic compound (one with a cation and an anion) will be a salt. An acid usually begins with an H while a base usually ends with an OH. However sometimes it can be a little more complicated than that with certain compounds like NH3 (which is a base since it accepts a proton). I would r...
- Sat Jan 23, 2021 9:31 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Salts (Acid/Base)
- Replies: 3
- Views: 289
Re: Salts (Acid/Base)
Strong acids yield weak conjugate bases and vice versa. Strong bases yield weak conjugate acids and vice versa. A salt is comprised of a conjugate acid and conjugate base. If the two conjugates are the same strength, the salt is neutral, however if one is derived from a strong acid (it would be a we...
- Sat Jan 23, 2021 9:26 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pKa and Ka
- Replies: 27
- Views: 821
Re: pKa and Ka
Like the others have said, its the negative log of Ka. Whenever you see "p" behind a unit denomination (Im talking about ka, kb, H, OH) then it means youre taking the negative log of that original value.
- Sat Jan 23, 2021 9:22 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Tables
- Replies: 36
- Views: 1591
Re: ICE Tables
The coefficients determine how many x's are added or subtracted on each cooresponding side of the chemical equation.
- Fri Jan 22, 2021 1:32 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ka and Kb vs [H+] and [OH-] confusion
- Replies: 2
- Views: 773
Ka and Kb vs [H+] and [OH-] confusion
So my understanding is that Ka times Kb equals Kw (1*10^14), but [H+] times [OH-] also equals Kw. Yet [H+] and [OH-] don't mean the same as Ka and Kb respectively. How is it possible that each pair of values both equal Kw when multiplied, but Ka and [H+] aren't the same and Kb and [OH-] aren't the s...
- Sat Jan 16, 2021 9:20 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Concentration of the Reactants and Products based on the Value of K
- Replies: 4
- Views: 326
Re: Concentration of the Reactants and Products based on the Value of K
K is known as the equilibrium constant of products to reactants. This means that for the value of K, you have K times the concentration of reactants as you do products. For instance, lets say at equilibrium, you have 4 M of products and 2 M of reactants. Your K value in this instance would be 2 sinc...
- Sat Jan 16, 2021 9:10 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE table and Molarity units
- Replies: 18
- Views: 717
Re: ICE table and Molarity units
One of the sapling question feedbacks for week 1 said that you could even use moles for the ice box. It really doesn't matter but for simplicity's sake, if you can do everything in mol/liter, that would probably be best to save a lot of headaches :)
- Sat Jan 16, 2021 9:04 pm
- Forum: Student Social/Study Group
- Topic: Motivation
- Replies: 39
- Views: 1729
Re: Motivation
Always have something to look forward to. Encourage yourself to complete your work in pursuit of a reward afterwards (i.e. getting to watch a movie, play videogames, go out with friends, etc.)
- Sat Jan 16, 2021 9:01 pm
- Forum: Student Social/Study Group
- Topic: How to relax
- Replies: 168
- Views: 21113
Re: How to relax
If you're fidgety when you're stressed, try investing in a high-quality stress ball. You won't regret it :)
- Sat Jan 16, 2021 7:53 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pH of Weak Acids
- Replies: 11
- Views: 407
Re: pH of Weak Acids
The pH of a solution is determinant of the amount of H3O+ ions there are. A high concentration of a weak acid can outperform the acidity of a low concentration of a strong acid, simply because the former will protonate more water molecules simply due to its amounts, unlike the latter. So that's why ...
- Sat Jan 16, 2021 7:44 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE box for partial pressures
- Replies: 10
- Views: 353
Re: ICE box for partial pressures
You can look up the formula, it essentially can be looked at the same as a regular concentration ratio.
- Sat Jan 16, 2021 7:43 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 2 #6
- Replies: 4
- Views: 163
Re: Sapling Week 2 #6
So essentially, you have to look at each ion and reference what kind of conjugate acid/base is it from it's counterpart base/acid. If the ion comes from a strong acid, then that makes it a weak conjugate base. If it came from a weak acid, then it is a strong conjugate base. The same is said for base...
- Sat Jan 16, 2021 7:35 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Finding Equilibrium Concentrations
- Replies: 5
- Views: 301
Re: Finding Equilibrium Concentrations
At that point, you're going to need the equilibrium constant, K, and the reaction quotient, Q, and compare your scenario from there. If the reaction quotient is less than K, then that means the current ratio of products to reactants is too reactant favored and will shift to the right, and vice versa...
- Sat Jan 16, 2021 12:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: When x is negligible in Equilibrium constant
- Replies: 34
- Views: 1376
Re: When x is negligible in Equilibrium constant
Smaller than 10^-3 to be safe. A value that incredibly small will have pretty much zero effect on yoyr approximations
- Sat Jan 16, 2021 12:05 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homework Problem #3 7
- Replies: 3
- Views: 183
Re: Homework Problem #3 7
Like the others said, solving for x means finding the unknown changes to the concentrations. Remember that K will always stay the same, with the exception of temperature change. So by adding more product, some of that product will decompose/form to more reactants until it reaches the product/reactan...
- Wed Dec 16, 2020 12:41 am
- Forum: SI Units, Unit Conversions
- Topic: Avogadro's Number
- Replies: 12
- Views: 2148
Re: Avogadro's Number
I could be wrong but shouldn't you multiply by Avogadro's number if you're trying to go from moles to molecules/atoms (i.e. 5 moles of carbon * 6.022*10^23 = number of atoms of carbon).
- Wed Dec 16, 2020 12:33 am
- Forum: Empirical & Molecular Formulas
- Topic: Empirical Formulas
- Replies: 4
- Views: 1002
Re: Empirical Formulas
The empirical formula is the smallest whole number ratio of the atoms within the compound. When you solve for the chemical equation (or if you simply already have it), you can find the empirical formula by finding dividing by the lowest common multiple of each of the number of atoms in the compound.
- Wed Dec 16, 2020 12:29 am
- Forum: Dipole Moments
- Topic: Dipole Arrows & Electronegativity
- Replies: 6
- Views: 419
Re: Dipole Arrows & Electronegativity
Yeah, like the others have said, think of the arrow as the direction of pull. The arrow points towards the more electronegative atom, as it has the stronger negative charge.
- Wed Dec 16, 2020 12:25 am
- Forum: Octet Exceptions
- Topic: Exceptions outside the ones we memorized
- Replies: 6
- Views: 392
Re: Exceptions outside the ones we memorized
Expanded octets are the norm, not the exception. Mostly any atom past the third row can utilize expanded octets to create unique bonding shapes.
- Wed Dec 16, 2020 12:23 am
- Forum: Ionic & Covalent Bonds
- Topic: Stronger Melting Point
- Replies: 11
- Views: 527
Re: Stronger Melting Point
Ionic bonds are much stronger than any other force, which makes it more difficult to break apart, which in turn heightens the boiling point of the compound.
- Sun Dec 06, 2020 11:54 pm
- Forum: Octet Exceptions
- Topic: Clarification on Expanded Octets
- Replies: 3
- Views: 239
Re: Clarification on Expanded Octets
Instead of creating concentrated pairs of electrons, the atom instead spreads out its electrons over multiple orbitals in the d-subshell, creating multiple extra bonds to be used. More atoms are capable of expanded octets than those that aren't. It's the norm, not the exception. :)
- Sun Dec 06, 2020 11:48 pm
- Forum: Lewis Acids & Bases
- Topic: Water
- Replies: 63
- Views: 2681
Re: Water
It can be either or
- Sun Dec 06, 2020 11:41 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: acidic and basic salts
- Replies: 3
- Views: 231
Re: acidic and basic salts
If the salt in question was formed by a strong acid and strong base, then it will be a neutral salt (i.e. HCL + NaOH => H2O + NaCl), however if a weak acid or a weak base was used, then the resulting salt will be an acidic salt or a basic salt, respectively.
- Sun Dec 06, 2020 11:35 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Types of Salts
- Replies: 7
- Views: 584
Re: Types of Salts
A salt cannot be strong or weak
- Sun Dec 06, 2020 11:29 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Concept of pH
- Replies: 10
- Views: 548
Re: Concept of pH
pH is a form of reactivity for solutions. Different pHs cause for different reactions. pH means the log of H, meaning Hydrogen ions, on a scale of 1-14. As the others have said, more H ions means a more acidic solutions and vice versa.
- Wed Nov 25, 2020 12:13 am
- Forum: Quantum Numbers and The H-Atom
- Topic: Silver Electron Configuration
- Replies: 9
- Views: 2704
Re: Silver Electron Configuration
Know that the 5s orbital is of a higher energy level than the 4d level. If the lower levels aren't filled completely first, then the higher energy levels will not be able to carry electrons in a stable state, as they will want to fall to a tighter level.
- Wed Nov 25, 2020 12:05 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Determining an orbital
- Replies: 10
- Views: 557
Re: Determining an orbital
The l quantum number will determine the subshell. So n=3 l=0 is 3s while n=3 l=1 is 3p.
- Tue Nov 24, 2020 11:56 pm
- Forum: Limiting Reactant Calculations
- Topic: Combustion
- Replies: 10
- Views: 515
Re: Combustion
The problem should always tell you when an excess reactant is present in a reaction. So then you'll have to work with the limiting reactant to solve whatever it is the problem is asking. Oxygen will very typically always be in excess since it is unusual, in the real world, to run out of oxygen in an...
- Tue Nov 24, 2020 11:52 pm
- Forum: Significant Figures
- Topic: 40. versus 40
- Replies: 23
- Views: 1514
Re: 40. versus 40
Trailing zeroes are never significant unless a decimal is present. So yes you are correct since it is for 40.
- Tue Nov 24, 2020 11:48 pm
- Forum: Empirical & Molecular Formulas
- Topic: Molecular Formula and Empirical Formula Mass
- Replies: 6
- Views: 540
Re: Molecular Formula and Empirical Formula Mass
That's an interesting question. However the definition of the empirical formula is the whole number ratio of atoms within a molecular formula. So it would not make sense for an empirical formula to have more mass than its molecular formula.
- Sun Nov 22, 2020 11:55 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Best Formal Charge Equations
- Replies: 24
- Views: 1036
Re: Best Formal Charge Equations
A way to understand the concept of formal charge mentally is to comprehend whether an atom has gained or lost electrons. If you see an oxygen atom with 3 lone pairs and a single bond, for instance, you should be able to 'eyeball' that the atom has a formal charge of -1 because oxygen is supposed to ...
- Sun Nov 22, 2020 11:49 pm
- Forum: Sigma & Pi Bonds
- Topic: Pi Bond Name
- Replies: 5
- Views: 240
Re: Pi Bond Name
Pi and Sigma are greek symbols. Pi-bonds just share the same name as the mathematical pi value. It's simply a name.
- Sun Nov 22, 2020 11:46 pm
- Forum: Properties & Structures of Inorganic & Organic Bases
- Topic: Inorganic and Organic
- Replies: 7
- Views: 707
Re: Inorganic and Organic
In the science field, organic will 99% of the time refer to carbon, nitrogen, oxygen, and hydrogen (occasionally sulfur and phosphorus) and possess biological properties. And inorganic will typically refer to everything else with lack biological significance.
- Sun Nov 22, 2020 11:43 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Acids/Bases
- Replies: 7
- Views: 628
Re: Acids/Bases
Also, the presence of H+ ions within a given solution will reflect the strength of an acid. A higher concentration means a stronger Acid. The same goes for OH- ions in the case of the strength of a base.
- Sun Nov 22, 2020 11:38 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionization Energy
- Replies: 19
- Views: 729
Re: Ionization Energy
When energy is applied to the atom, the first electron that will be removed is always the outermost electron since they require the least amount of energy to take out.
- Sun Nov 22, 2020 11:36 pm
- Forum: Ionic & Covalent Bonds
- Topic: Polar Bonds [ENDORSED]
- Replies: 26
- Views: 1207
Re: Polar Bonds [ENDORSED]
By the looking at the structure, if the molecule is asymmetrical with bonding, electrons, etc, then it is always non-polar because that means that one side is slightly more positive/negative than the other.
- Mon Nov 16, 2020 12:05 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Ionic Bond vs. Hydrogen Bonding
- Replies: 10
- Views: 2694
Re: Ionic Bond vs. Hydrogen Bonding
Compounds with ionic bonds have a higher boiling point (meaning they are more difficult to boil) than molecules with h-bonds, or any other bonds for that matter.
- Sun Nov 15, 2020 11:59 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Sapling # 20
- Replies: 6
- Views: 651
Re: Sapling # 20
Remember that all molecules have London dispersion forces. This example has dipole-dipole forces as well because it is polar. A molecule is polar based on the uneven shape that it exhibits, which is seen in its lewis structure. The uneveness creates a slight positive side, as well as a negative side...
- Sun Nov 15, 2020 11:56 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Hydrogen Bonding Sites
- Replies: 4
- Views: 184
Re: Hydrogen Bonding Sites
Yes. Be sure to focus on electronegative atoms. Atoms like carbon aren't strong enough to create a hydrogen bond.
- Sun Nov 15, 2020 11:54 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Van der Waals vs London Dispersion
- Replies: 10
- Views: 596
Re: Van der Waals vs London Dispersion
Interchangeable terms. You can also say, dipole-induced-dipole interactions. All mean the same.
- Fri Nov 06, 2020 8:53 pm
- Forum: Properties of Light
- Topic: Photoelectric Effect
- Replies: 14
- Views: 808
Re: Photoelectric Effect
Yes the excess energy is still classified as kinetic energy. If the work function is less than the energy of a photon, then the 'excess' kinetic energy of the electron will result as the difference. Since electrons have mass, this energy would be kinetic.
- Fri Nov 06, 2020 8:40 pm
- Forum: Lewis Structures
- Topic: Difference in ionic and covalent Lewis structures
- Replies: 9
- Views: 2629
Re: Difference in ionic and covalent Lewis structures
Ionic bonds give and take electrons (cations give away electrons while anions take electrons) and are expressed in lewis structures using dots. Covalent bonds share electrons and are expressed in lewis structures using lines.
- Fri Nov 06, 2020 8:36 pm
- Forum: Ionic & Covalent Bonds
- Topic: Homework due date
- Replies: 49
- Views: 2045
Re: Homework due date
I've always been turning in the homework Sunday evening (usually 8-10pm) and it's shown as graded. So yes, the date means Sunday night :)
- Fri Nov 06, 2020 8:34 pm
- Forum: Ionic & Covalent Bonds
- Topic: Formal Charge Equation
- Replies: 10
- Views: 440
Re: Formal Charge Equation
A bond consists of two electrons, one from each of the bonded atoms. When you are discussing formal charge, the reason why you only count a bond as one electron is because you are only focused on a single atom, and only one electron in a bond belongs to that said atom. Hopefully that makes more sense.
- Fri Nov 06, 2020 8:27 pm
- Forum: Ionic & Covalent Bonds
- Topic: Problem 2A.23
- Replies: 4
- Views: 306
Re: Problem 2A.23
Aluminum has a charge of +3. This means that in order for the formal charge to be zero, it needs to lose three electrons. Hydrogen has a charge of +1. It can either lose or gain an electron to be stable. In this scenario, it is best for the Aluminum to bond with three hydrogens as it will satisfy it...
- Sun Nov 01, 2020 11:29 pm
- Forum: DeBroglie Equation
- Topic: Sapling #25
- Replies: 4
- Views: 366
Re: Sapling #25
For the photon, you would calculate the energy using e=hv. For the electron, use e=1/2mv^2. The reason why you use two different equations is because one involves mass while the other involves simply frequency. The photon's energy is calculated by converting it's frequency to the corresponding energ...
- Sun Nov 01, 2020 11:23 pm
- Forum: Einstein Equation
- Topic: Sapling #1
- Replies: 6
- Views: 1216
Re: Sapling #1
Remember that the wavelength and the corresponding frequency is a characteristic of the photon, and that having more of these photons will not affect this individual aspect. Think of it like horses pulling a wagon. If you add more horses, the 'intensity' of the wagon being pulled increases, but the ...
- Sun Nov 01, 2020 11:16 pm
- Forum: Properties of Light
- Topic: Wavelength
- Replies: 26
- Views: 1204
Re: Wavelength
All wavelength equations would require you to convert to meters since that is an S.I. unit.
- Sun Nov 01, 2020 11:13 pm
- Forum: Properties of Light
- Topic: Wavelenght
- Replies: 17
- Views: 666
Re: Wavelenght
They have the shortest frequency of all waves. Which means they have the highest frequency of all waves as well. Remember that they are inversely related to each other.
- Sun Nov 01, 2020 11:12 pm
- Forum: Significant Figures
- Topic: 0's
- Replies: 32
- Views: 1287
Re: 0's
Trailing zeroes are not significant unless there is a decimal place. Otherwise, yes they are.
- Wed Oct 21, 2020 6:46 pm
- Forum: Properties of Electrons
- Topic: 1A.1 part a
- Replies: 4
- Views: 150
Re: 1A.1 part a
The ability to pass through metal is a property that waves possess. So it would support the wave argument.
- Wed Oct 21, 2020 6:36 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Calculating Velocity
- Replies: 5
- Views: 242
Re: Calculating Velocity
Anything that has mass must be less than the speed of light, otherwise it theoretically requires an infinite amount of energy for it to get it up to exactly the speed of light.
- Wed Oct 21, 2020 6:15 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Electron Example from Lecture 9
- Replies: 4
- Views: 151
Re: Electron Example from Lecture 9
It is impossible for anything to surpass the speed of light. The speed of light is approximately 3.0*10^8 meters per second, so just remember this and you'll be good. :)
- Wed Oct 21, 2020 6:10 pm
- Forum: DeBroglie Equation
- Topic: Sapling question 25
- Replies: 5
- Views: 371
Re: Sapling question 25
You have everything you need to plug it into the De Broglie equation and solve for the velocity, (Wavelength, planck's constant, mass of electron). Solve for the velocity and use E=0.5mv^2 to get the energy.
- Wed Oct 21, 2020 5:56 pm
- Forum: Properties of Light
- Topic: Homework Problem 3
- Replies: 4
- Views: 192
Re: Homework Problem 3
So remember that the wavelength and frequency is a characteristic of the photons. However, the energy emitted is based on the intensity/amount of photons. So the energy is the only factor that is affected in this scenario.
- Wed Oct 14, 2020 12:48 pm
- Forum: Properties of Light
- Topic: Bohr model and frequency equation
- Replies: 4
- Views: 169
Re: Bohr model and frequency equation
Yeah but it's not exactly how an atom looks visually (no one knows exactly how an atom looks, to my knowledge) but the model essentially simplifies atoms and their electron levels to work with on paper. It's still very usable, it's just not a model to represent visually how an atom looks in real life.
- Wed Oct 14, 2020 12:41 pm
- Forum: Properties of Light
- Topic: Light intensity for electron ejection
- Replies: 7
- Views: 296
Re: Light intensity for electron ejection
Question... I thought before we saw in the Photoelectric Effect that increasing intensity does not work to eject electrons because it is not acting like a wave model. Here, are we talking about the intensity of a wavelength then? Because in the most recent lecture, we see that increasing light inte...
- Wed Oct 14, 2020 12:36 pm
- Forum: Einstein Equation
- Topic: Energy of Photons
- Replies: 2
- Views: 185
Re: Energy of Photons
In the ideal scenario (i.e. the problems in the homework), then yes, a singular wave of light of a particular frequency will have the exact same energy for all photons.
- Wed Oct 14, 2020 12:20 pm
- Forum: Properties of Light
- Topic: Light intensity for electron ejection
- Replies: 7
- Views: 296
Re: Light intensity for electron ejection
Assuming that the wave has enough energy, then yes. A higher intensity light would yield more photons, therefore more electrons being released.
- Wed Oct 14, 2020 12:16 pm
- Forum: Significant Figures
- Topic: Sig Fig Process
- Replies: 13
- Views: 618
Re: Sig Fig Process
If you do it at the end, it'll be easier for you because you'll be closer to the true answer. Otherwise, you could be quite far off and have to make estimations, especially when doing empirical formula problems.
- Fri Oct 09, 2020 11:56 am
- Forum: SI Units, Unit Conversions
- Topic: Rounding
- Replies: 20
- Views: 587
Re: Rounding
If it's not too confusing, try to use the most exact values as you possibly can and round at the end. This way, you won't have much dispairity to the actual answer. If you round your values throughout the problem, as you work through it, you may expect a solid whole number at some point but actually...
- Fri Oct 09, 2020 11:52 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Moles vs molecules
- Replies: 14
- Views: 841
Re: Moles vs molecules
A simple way to think about it is that a molecule is one unit, and a mole is 6.02*10^23 units. A molecule of water is H2O (two hydrogen atoms and one oxygen atom). It is unreasonably small to weigh and measure for most of our calculations, so we use the mole. A mole of water (6.02*10^23 atoms of wat...
- Fri Oct 09, 2020 11:46 am
- Forum: Balancing Chemical Reactions
- Topic: How moles should be balanced on each side
- Replies: 11
- Views: 788
Re: How moles should be balanced on each side
Remember that one mole of two reactants will not always equal one mole of two products. You may be confused with comparing mass on both sides. The mass on both sides of the equation must always be the same because of the law of conservation of mass, but the moles can be completely different. One mol...
- Fri Oct 09, 2020 10:51 am
- Forum: Ionic & Covalent Bonds
- Topic: Determining Empirical Formula (HW Question)
- Replies: 6
- Views: 842
Re: Determining Empirical Formula (HW Question)
Hey, I actually just came from my discussion doing this question so I'll try my best to explain it. Hopefully others can fill in any gaps I leave out :) Note that I'll be using exact numbers from the periodic table, while solving this, to get as close to the approximate answer as possible. So the fa...
- Fri Oct 09, 2020 10:10 am
- Forum: SI Units, Unit Conversions
- Topic: Sig figs and molar mass
- Replies: 18
- Views: 517
Re: Sig figs and molar mass
I find, especially when I'm trying to figure out the empirical formula, that using the entire value makes finding the approximate mole ratio a lot easier. For instance, I was in my discussion earlier and I found that if I used the entire mass without rounding, the mole ratio for the elements in the ...