Search found 64 matches
- Tue Mar 12, 2019 7:31 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow step in reaction mechanisms
- Replies: 1
- Views: 231
Re: Slow step in reaction mechanisms
The slow step is the rate-determining step because a reaction can only be as fast as the slowest part. I like to think of it like a factory, where each step in the assembly line helps put together a product. This isn't a perfect analogy, but the production is limited by the step that takes the longe...
- Tue Mar 12, 2019 7:28 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: identifying radicals
- Replies: 1
- Views: 228
Re: identifying radicals
I am unsure if there is an easier or shortcut way to do this, but I know that if you draw the lewis structure you will see if it is a radical or not.
- Tue Mar 12, 2019 7:26 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Units
- Replies: 3
- Views: 373
Re: Units
Why do the units change depending on the order of the reaction?
- Mon Mar 04, 2019 3:18 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst
- Replies: 6
- Views: 531
Re: Nernst
I believe you can use them interchangeably, the only thing is I think that log is a more common version of the equation.
- Mon Mar 04, 2019 3:13 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: "N" in Kinetics
- Replies: 4
- Views: 477
Re: "N" in Kinetics
The order of a reaction also indicates to what extent the concentration has an effect on the rate, as well as which species has the greatest effect.
- Mon Mar 04, 2019 3:06 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Activation energy
- Replies: 8
- Views: 812
Re: Activation energy
Activation energy can help explain why a reaction is thermodynamically favorable but still will not occur because it has a very high activation energy and is therefore not kinetically favorable.
- Mon Feb 25, 2019 10:56 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: When to use Platinum
- Replies: 5
- Views: 5765
Re: When to use Platinum
You need to have one conductive metal on each side of the galvanic cell. Therefore, if one side only has aqueous solutions (and therefore non-conductive), you have to add platinum as an electrode to that side.
- Mon Feb 25, 2019 10:52 am
- Forum: Balancing Redox Reactions
- Topic: Rules for redox reactions
- Replies: 3
- Views: 347
Re: Rules for redox reactions
A lot of the time you can also look on the periodic table for charges. For example, elements in column one have 1+ charge, and elements in the halide column usually have a charge of 1-. As you go further in to the middle of the periodic table it becomes less predictable, but you can usually figure i...
- Mon Feb 25, 2019 10:49 am
- Forum: Balancing Redox Reactions
- Topic: Balancing Charges
- Replies: 4
- Views: 347
Re: Balancing Charges
Always assume oxygen has a negative 2 charge.
- Fri Feb 22, 2019 8:50 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 5
- Views: 537
Re: Salt Bridge
What would be the purpose of using a porous disk instead of a salt bridge?
- Mon Feb 18, 2019 6:08 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneity and exothermic reactions
- Replies: 3
- Views: 376
Re: Spontaneity and exothermic reactions
Endothermic reactions need energy to be added to the system to occur, and you could think of that like it is not spontaneous because it needs energy to react. In contrast, if it does not need energy to react, it should be more spontaneous.
- Mon Feb 18, 2019 6:07 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G
- Replies: 4
- Views: 444
Re: Delta G
If it's not dependent on the path taken, then it is a state function.
- Mon Feb 18, 2019 6:04 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Equation
- Replies: 4
- Views: 428
Re: Van't Hoff Equation
Boltzmann's constant is used for calculating entropy. The R in the Van't Hoff equation is referring to the gas constant.
- Tue Feb 12, 2019 12:39 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Third Law
- Replies: 2
- Views: 319
Re: Third Law
The third law states that entropy of a perfect crystal is zero at temperature absolute zero.
- Tue Feb 12, 2019 12:35 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Determining of there is Change
- Replies: 2
- Views: 298
Re: Determining of there is Change
Sometimes it will tell you, but sometimes you have to assume based on definitions alone. For example, by definition of enthalpy, you would expect the pressure to remain the same.
- Tue Feb 12, 2019 12:32 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isochoric vs isometric
- Replies: 4
- Views: 2440
Re: Isochoric vs isometric
What is the significance of knowing that it is isometric/isochoric? Is it just to know that there is no change for when you're doing calculations?
- Fri Feb 08, 2019 12:29 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Delta H
- Replies: 7
- Views: 1177
Re: Delta H
It's also important to note that enthalpy is additive because of Hess's Law. It is a state function, so the change in enthalpy (Delta H) at each step of a multistep reaction can be added to get the total enthalpy change.
- Fri Feb 08, 2019 12:24 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible Expansion
- Replies: 3
- Views: 342
Re: Reversible Expansion
This might be an obvious question, but will a problem always tell you explicitly if it is reversible or irreversible?
- Fri Feb 08, 2019 12:14 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Bomb calorimeters vs polystyrene cup calorimeters
- Replies: 3
- Views: 582
Re: Bomb calorimeters vs polystyrene cup calorimeters
Wouldn't a regular polystyrene calorimeter be an approximation of a closed system, because heat can go out but volume remains the same?
- Wed Jan 30, 2019 6:19 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: 7th edition 6D.3
- Replies: 1
- Views: 481
Re: 7th edition 6D.3
The reason why it is 0.10-0.06 instead of just 0.10 is because Ka is the ratio of concentrations at equilibrium .To understand this better, you could use an ICE table and put the values in. It would show that [HClO2] at equilibrium is initial [HClO2] - X, where X is the equivalent to the [H3O+] conc...
- Wed Jan 30, 2019 6:11 pm
- Forum: Calculating Work of Expansion
- Topic: Change in internal energy
- Replies: 3
- Views: 321
Re: Change in internal energy
The internal energy of a system does not necessarily mean heat, it can also be referring to work, because U= heat + work. Therefore, in 4A. 3 (c), delta U is equal to the amount of work done, which is 28 J.
- Wed Jan 30, 2019 6:08 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Decreasing volume and chemical equilibrium
- Replies: 8
- Views: 864
Re: Decreasing volume and chemical equilibrium
When you decrease the volume at equilibrium, it will shift towards the side of the reaction with fewer moles.
- Wed Jan 23, 2019 7:52 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical equilibrium post assessment part q24
- Replies: 1
- Views: 178
Re: Chemical equilibrium post assessment part q24
First, you have to calculate Q. Then, compare Q to the K value. If Q<K, the reaction proceeds to products. If Q> K, the reaction favors the left.
- Wed Jan 23, 2019 7:48 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Strong acids and bases
- Replies: 6
- Views: 554
Re: Strong acids and bases
Strong Bases: LiOH - lithium hydroxide NaOH - sodium hydroxide KOH - potassium hydroxide RbOH - rubidium hydroxide CsOH - cesium hydroxide Ca(OH)2 - calcium hydroxide Sr(OH)2 - strontium hydroxide Ba(OH)2 - barium hydroxide Strong Acids: HCl - hydrochloric acid HNO3 - nitric acid H2SO4 - sulfuric ac...
- Wed Jan 23, 2019 7:42 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ice chart
- Replies: 7
- Views: 863
Re: ice chart
Technically you could solve a problem without using an ice chart, it's just an easier way to organize and understand the information you are given.
- Fri Jan 18, 2019 8:55 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Calculating PH of weak acids and bases
- Replies: 5
- Views: 361
Re: Calculating PH of weak acids and bases
As long as x is less than 5% of the initial value, than you know it is okay to approximate it to be 0 (in relation to the initial value, NOT the other values).
- Fri Jan 18, 2019 8:53 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Net Ionic Equations
- Replies: 3
- Views: 349
Re: Net Ionic Equations
That response is correct, but also for calculating K, you usually do not include H20 because it is in excess.
- Fri Jan 18, 2019 8:49 am
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: when is x negligible
- Replies: 7
- Views: 6654
Re: when is x negligible
Also, just something to keep in mind, is that if you have already solved the problem using the shortcut (when you assume x to negligible), Lavelle said that the general rule is anytime x is less than 5% of the initial value, then it is safe to assume an approximation to 0.
- Wed Jan 09, 2019 2:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium Constants Involving Spectator Ions
- Replies: 2
- Views: 116
Re: Equilibrium Constants Involving Spectator Ions
Spectator ions are present, but they are not part of the reactants because they do not react in solution. You do not include spectator ions in calculations because they do not affect the concentration of the products.
- Wed Jan 09, 2019 2:09 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE Tables
- Replies: 3
- Views: 558
Re: ICE Tables
An ICE table is an easy way to organize the information needed to calculate equilibrium composition of a system. Start by identifying the components of the reaction (reactants and products) and list them. These will make up the columns of the ICE table. The rows are made up of initial molarity (I), ...
- Wed Jan 09, 2019 2:01 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc for Gases
- Replies: 2
- Views: 130
Re: Kc for Gases
Once you convert to mol/L using the ideal gas law equation (as already mentioned), Kc indicates that the units used were in mol/L, rather than atm. Kp involves gasses that are not converted to moles, therefore it remains in units of atm.
- Wed Dec 05, 2018 11:03 am
- Forum: Bronsted Acids & Bases
- Topic: Ka Formula
- Replies: 6
- Views: 885
Re: Ka Formula
An easy way to remember is Ka= [products]/[reactants]
- Mon Dec 03, 2018 4:54 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate
- Replies: 1
- Views: 209
Re: Polydentate
Drawing the Lewis structure is probably the most accurate way to see how many and where the lone pairs will be located on the coordination compound.
- Mon Dec 03, 2018 4:49 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Hydronium
- Replies: 4
- Views: 457
Re: Hydronium
H+ is a hydrogen ion by itself, while hydronium is a hydrogen ion bonded to a water molecule. When calculating pH, however, you can use [H+] and [H3O] interchangeably, and still get the right answer.
- Mon Dec 03, 2018 4:45 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Salts cause acidity
- Replies: 5
- Views: 381
Re: Salts cause acidity
NaCl interacts with water, because the polar nature of water, however, it does not pull a hydrogen ion off of the water molecule, like an acidic salt would do.
- Sat Dec 01, 2018 4:18 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate ligands
- Replies: 3
- Views: 287
Re: Polydentate ligands
Polydentate means that the ligands bind at multiple sites of the coordination compound.
- Sat Dec 01, 2018 4:10 pm
- Forum: Naming
- Topic: CN naming?
- Replies: 3
- Views: 268
Re: CN naming?
Oh sorry I didn't mean remove the "-ide" just the "e" part.
- Sat Dec 01, 2018 4:09 pm
- Forum: Naming
- Topic: CN naming?
- Replies: 3
- Views: 268
Re: CN naming?
When naming coordination compounds, you remove the "-ide" and add "o" to the end of the anion name. Therefore, I don't think there would be a place you would use cyanido, it would always be cyano. Somebody correct me if I'm wrong.
- Sat Dec 01, 2018 4:05 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Oxidation Number
- Replies: 2
- Views: 194
Re: Oxidation Number
There is a coordination number of 6, due to the 6 Cn, and the overall charge is -4, so you take 6 + (-4) = 2, which is the oxidation state of Fe.
- Mon Nov 26, 2018 3:18 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: NaCl vs. NiCl
- Replies: 3
- Views: 450
NaCl vs. NiCl
Dr. Lavelle mentioned that salt will completely dissolve so that each ion is surrounded by water molecules, but NiCl won't, and instead will become a coordination compound. Can someone explain why this happens?
- Mon Nov 26, 2018 3:08 pm
- Forum: Sigma & Pi Bonds
- Topic: Pi Strength
- Replies: 4
- Views: 411
Re: Pi Strength
A double bond is stronger than a single bond because of the presence of both a sigma and pi bond, but it is less than twice as strong as a single bond. Although I am unsure, using this line of reasoning it would make sense that a pi bond is weaker than a sigma bond. It makes a bond stronger in a dou...
- Mon Nov 26, 2018 3:05 pm
- Forum: Hybridization
- Topic: Hybridization & Types of Bonds [ENDORSED]
- Replies: 3
- Views: 369
Re: Hybridization & Types of Bonds [ENDORSED]
A sigma bond is present anytime there is a single bond. A double bond is composed of one sigma bond and one pi bond.
- Wed Nov 14, 2018 1:50 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Electron density
- Replies: 6
- Views: 613
Re: Electron density
When determining the bond angles for the VSEPR model, you could also think of electron density of the center atom in terms of the outer atoms. It may be easier to think of it like you are trying to make each atom as far apart as possible, and therefore creating the largest bond angles possible.
- Wed Nov 14, 2018 1:48 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR
- Replies: 3
- Views: 385
Re: VSEPR
First, in order to find the VSEPR model for a molecule, you need to draw the Lewis structure. This is a 2D demonstration, and says nothing about the bond angles. To determine the shape, use 3 dimensions to find the angles that each atom (and therefore the electron densities) are as far apart as poss...
- Tue Nov 13, 2018 12:20 pm
- Forum: Dipole Moments
- Topic: Van der Waals
- Replies: 4
- Views: 391
Re: Van der Waals
Yes, all molecules display van der waals forces, however, the most prominent example would be in non-polar, because polar and ionic bonds have stronger forces that are more characteristic of those bonds.
- Thu Nov 08, 2018 3:20 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 Bonds vs. Ion-Dipole Bonds
- Replies: 5
- Views: 2556
Re: Hydrogen Bonds vs. Ion-Dipole Bonds
The greater electronegativity of the hydrogen bond acceptor makes hydrogen bonds very strong. Hydrogen bonds are a form of dipole-dipole bonding, but it is stronger than other dipole-dipole interactions due to the electronegativity and the size is very small, allowing the H atoms to be closer to eac...
- Thu Nov 08, 2018 3:09 pm
- Forum: Electronegativity
- Topic: Ionization Energy over Electronegativity?
- Replies: 4
- Views: 510
Re: Ionization Energy over Electronegativity?
Because ionization energy and electronegativity follow the same periodic trend, you could look for the element with the lowest electronegativity to be in the center of the Lewis structure, and it would come with the same result. More electronegative elements are usually found towards the outside of ...
- Thu Nov 08, 2018 3:00 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bond Length
- Replies: 8
- Views: 582
Re: Bond Length
In addition to the patterns of decreasing bond length from single to double to triple bonds, there is also a pattern in which larger atoms have a larger distance between each other, resulting in a longer bond length.
- Fri Nov 02, 2018 2:19 pm
- Forum: Lewis Structures
- Topic: Formal Charge Tricks
- Replies: 5
- Views: 3531
Re: Formal Charge Tricks
In my section, we talked about a shortcut where you take the number of valence electrons the element has in it's normal state, and subtract the number of valence electrons it has when it is bonded.
- Fri Nov 02, 2018 2:09 pm
- Forum: Coordinate Covalent Bonds
- Topic: Electronegativity
- Replies: 12
- Views: 1680
Re: Electronegativity
When ionization energy and electron affinity are high, then the atom will also have a high electronegativity, and pull shared electrons toward it. This explains the periodic table trends, but we will not need to know actual values of electronegativity.
- Wed Oct 31, 2018 2:59 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Effective Nuclear Charge
- Replies: 1
- Views: 124
Re: Effective Nuclear Charge
I am not sure whether it will show up on the exam, but you should know that the effective nuclear charge is often less than the full nuclear charge due to the shielding effect of electrons.
- Mon Oct 22, 2018 3:11 pm
- Forum: *Shrodinger Equation
- Topic: How Schrodinger Equation Relates to Atomic Orbitals
- Replies: 1
- Views: 451
Re: How Schrodinger Equation Relates to Atomic Orbitals
Schrodinger's equation provides the connection that wave functions are equivalent to orbitals. It states that the wave function can be described using quantum numbers n, l, and ml, in which a higher energy produces a larger orbital. These wave functions are associated with particular "shapes&qu...
- Mon Oct 22, 2018 3:05 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 4s and 3d Orbitals [ENDORSED]
- Replies: 3
- Views: 282
Re: 4s and 3d Orbitals [ENDORSED]
I forgot to add that for multi-electron atoms that come after atomic number 20, the 4s state is higher in energy than the 3d orbital, as you would expect. The 3d orbital is lower than the 4s only on the condition that the 4s orbital is occupied.
- Mon Oct 22, 2018 2:02 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 4s and 3d Orbitals [ENDORSED]
- Replies: 3
- Views: 282
Re: 4s and 3d Orbitals [ENDORSED]
According to Aufbau's principle, orbitals are filled in accordance to the lowest value of orbitals. For 4s, n+1=4+0=4, and for 3d, n+1=3+2=5
So, although 4s is higher in energy because it has a higher value of n, it is filled first because it has a lower value of orbitals.
So, although 4s is higher in energy because it has a higher value of n, it is filled first because it has a lower value of orbitals.
- Mon Oct 22, 2018 1:55 pm
- Forum: Properties of Light
- Topic: Light Intensity
- Replies: 2
- Views: 148
Re: Light Intensity
Intensity is directly correlated with the number of photons. The more intense the light, the more photons it has.
- Fri Oct 19, 2018 1:55 pm
- Forum: SI Units, Unit Conversions
- Topic: formula units [ENDORSED]
- Replies: 69
- Views: 32354
Re: Solution Concentration [ENDORSED]
How do you know which is the initial molarity, initial volume, final molarity, and/or final volume from a given problem? How do you figure it out? In a problem that involves M1V1=M2V2 you must first identify which you are trying to solve for. If you are solving for final molarity, you know that the...
- Fri Oct 19, 2018 1:27 pm
- Forum: *Shrodinger Equation
- Topic: Shrodinger Equation on Test
- Replies: 5
- Views: 383
Re: Shrodinger Equation on Test
My TA said that at the end of class today he would go over what we should know for the test, but I would get familiar with the Shrodinger equation and be comfortable solving problems using it.
- Fri Oct 19, 2018 1:16 pm
- Forum: Trends in The Periodic Table
- Topic: s, p, d, f
- Replies: 16
- Views: 4254
Re: s, p, d, f
Would it be correct to say that 4d could have n=4, l=2, ml=-1, and ms=+1/2? and if so, would it be correct to assume that each possible configuration of quantum numbers for 4d represents an electron, giving the total number of electrons in that shell? You are correct that 4d could have those quantu...
- Tue Oct 09, 2018 9:27 pm
- Forum: Properties of Light
- Topic: Do I need to memorize the Light Spectrum? [ENDORSED]
- Replies: 13
- Views: 898
Re: Do I need to memorize the Light Spectrum? [ENDORSED]
It would probably be helpful to know the ranges of UV, visible, and infrared light, since that is the extent of what is used in chem for the most part, but i wouldn't worry as much about radio waves or microwaves because it doesn't seem as relevant to this course.
- Tue Oct 09, 2018 9:21 pm
- Forum: Properties of Light
- Topic: Planck's constant
- Replies: 5
- Views: 481
Planck's constant
In the equation E=hv, I understand that h is Planck's constant, but how was this derived and what exactly does it mean?
- Tue Oct 09, 2018 9:11 pm
- Forum: Properties of Light
- Topic: Photoelectric Effect
- Replies: 2
- Views: 104
Re: Photoelectric Effect
According to the lecture, the photoelectric experiment involved shining UV light on a metal surface to measure the required energy to remove electrons from different types of metals. Using the wave model for light, scientists expected that with increased intensity, the metal would emit more electron...
- Fri Oct 05, 2018 4:08 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: % Yield
- Replies: 8
- Views: 1579
Re: % Yield
I think you may be slightly confusing percent yield with percent error, in which case percent error is usually "acceptable" at around 5% (but it varies depending on the lab). In contrast, percent yield, although it may be affected by certain lab errors, does not directly correlate to error...
- Mon Oct 01, 2018 1:04 pm
- Forum: SI Units, Unit Conversions
- Topic: Week 1 Homework Assignment [ENDORSED]
- Replies: 16
- Views: 1196
Re: Week 1 Homework Assignment [ENDORSED]
Yes, due Friday at your discussion
- Mon Oct 01, 2018 1:02 pm
- Forum: Significant Figures
- Topic: Significant Figures [ENDORSED]
- Replies: 6
- Views: 425
Re: Significant Figures [ENDORSED]
Significant figures are important to use, even if it means reporting a less accurate number as your official answer, because a result can only be as accurate as the least accurate measure. You have to be honest so that it does not appear to be more accurate of an answer than the equipment used to ma...