Search found 82 matches
- Wed Mar 14, 2018 8:07 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Cell Concentration
- Replies: 3
- Views: 638
Re: Cell Concentration
I think Dr. Lavelle is talking about a cell that runs on the concentration difference between two chambers of the cell. He went over examples of these during lecture - different from a galvanic cell b/c doesn't depend on the oxidizing power / reducing power but instead on the conc. difference betwee...
- Wed Mar 14, 2018 8:05 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: adiabatic process
- Replies: 5
- Views: 800
Re: adiabatic process
In an adiabatic process it means that there is no net heat flow in or out of the system. You can change the pressure and this will result in a change in volume. This is why the adiabatic process line on a PV diagram is the shape it takes because the temperature does not change since there is no net ...
- Wed Mar 14, 2018 8:03 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2759142
Re: Post All Chemistry Jokes Here
If a King farts is it a Noble gas?
- Thu Mar 08, 2018 9:21 am
- Forum: General Rate Laws
- Topic: Reaction Rates
- Replies: 4
- Views: 780
Re: Reaction Rates
yes, the rate of the reaction is always positive. This can be confusing as the rate of disappearance can be negative (the rate at which the reactant is leaving). However, if you think about it, the rate of the reaction should never be negative because this is describing how fast the concentration ch...
- Mon Mar 05, 2018 1:51 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: k units [ENDORSED]
- Replies: 7
- Views: 1195
Re: k units [ENDORSED]
The units for k depend on what order the reaction is on. This is because the concentrations - which will be to the zero, first, or second order for this. So mol / L will be raised to some exponent. We know that the rate of the reaction is going to have units of mol / L * s, so we just have to make s...
- Mon Mar 05, 2018 1:48 pm
- Forum: General Rate Laws
- Topic: Half Life
- Replies: 6
- Views: 751
Re: Half Life
Also for medications. It could be useful to know how long a medicine is going to be active in a patient's body and how much is going to be present.
- Mon Mar 05, 2018 1:48 pm
- Forum: Zero Order Reactions
- Topic: Will we need to know how to derive equations? [ENDORSED]
- Replies: 9
- Views: 1184
Re: Will we need to know how to derive equations? [ENDORSED]
I'm sure Lavelle's exams don't have any sort of derivations on them. He could switch it up this year though
- Mon Feb 26, 2018 11:42 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: calculating n
- Replies: 9
- Views: 1161
Re: calculating n
You can look at your balanced half reactions and it will show you how many moles of electrons are going to be exchanged during the reaction.
- Mon Feb 26, 2018 11:41 am
- Forum: Balancing Redox Reactions
- Topic: Water in balancing reactions
- Replies: 4
- Views: 518
Re: Water in balancing reactions
Yes, you can use water to balance chemical reactions. Also a note .. make sure that the charges are balanced as well.
- Mon Feb 26, 2018 11:38 am
- Forum: First Order Reactions
- Topic: Order of a reaction
- Replies: 3
- Views: 466
Re: Order of a reaction
For kinetics, the order of the reaction with respect to some sort of substance (ex. reactant, product) is going to be the exponent to which it's concentration form is raised. We use this in the rate equation and we can see that the concentration of this substance is raised to some sort of power.
- Mon Feb 26, 2018 7:47 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation Energy???
- Replies: 7
- Views: 920
Re: Activation Energy???
I believe that if the activation energy is high then the rate of the reaction is going to be slower but if the reaction energy is low then the reaction rate is going to be faster.
- Thu Feb 22, 2018 12:46 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing H+
- Replies: 4
- Views: 484
Re: Balancing H+
I would think to do H+ since it was in the book and Dr. Lavelle said to do it as well. H3O makes it more complicated as well.
- Tue Feb 20, 2018 10:22 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cell Diagram
- Replies: 1
- Views: 263
Re: Galvanic Cell Diagram
I think it could be that they are in different phases. We are supposed to separate the objects that are in different phases when drawing the cell diagram and I'm assuming that the Cl - ions were in solution and the Cl2 was in a gaseous phase.
- Tue Feb 20, 2018 10:20 am
- Forum: Balancing Redox Reactions
- Topic: Anode vs Cathode and their Equations
- Replies: 2
- Views: 357
Re: Anode vs Cathode and their Equations
The cathode equations should have a more positive value of standard potential then the anode half reactions. This makes sense because when you go to determine the standard cell potential then you will arrive at the most energetically favorable number.
- Tue Feb 20, 2018 10:18 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Water in cell diagrams
- Replies: 1
- Views: 276
Re: Water in cell diagrams
You would never include H2O (s) because it is impossible to have the water electrode and just no reason to have it in the cell diagram. Also H2O (g) might sometimes be placed in the cell diagram if the pressure is large enough?
- Tue Feb 20, 2018 10:17 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Rule of Thumb for Cell Diagrams
- Replies: 3
- Views: 436
Re: Rule of Thumb for Cell Diagrams
When writing cell diagrams, we are supposed to have the anodic compartment on the left and the cathodic compartment on the right. To go more into detail about the anodic compartment, the far left side is supposed to have the metal or solid electrode, right side of the anodic compartment is supposed ...
- Tue Feb 13, 2018 7:42 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Standard Molar Entropy Question
- Replies: 3
- Views: 660
Standard Molar Entropy Question
Arrange the following in order of increasing standard molar entropy: CHF3, CF4, CH3F, CH2F2 (all are in the gaseous phase) The correct answer has CH3F < CH2F2 < CHF3 < CF4 but shouldn't have a higher standard molar entropy then since there are more ways to orientate the molecules?
- Tue Feb 13, 2018 4:56 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: enthalpy of surroundings
- Replies: 1
- Views: 249
Re: enthalpy of surroundings
The change in entropy of the surroundings is going to equal zero during an irreversible process. During an irreversible process, the change in entropy of the system is equal to the change in entropy total and the change in entropy of the surroundings is equal to zero. However, during a reversible pr...
- Tue Feb 13, 2018 4:54 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: ∆U equation
- Replies: 2
- Views: 422
Re: ∆U equation
I remember learning in physics this equation relates internal energy to temperature. I don't think we will have to use this equation on any test to calculate anything but we might have to understand what the equation. I generally think of this equation when an isothermal process comes into play ... ...
- Tue Feb 13, 2018 4:50 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Free energy
- Replies: 1
- Views: 295
Re: Free energy
I think you're talking about the equation where the free energy of the reaction is equal to the standard free energy plus RTlnQ. I think there was some derivation that was not covered that got the RTlnQ part but all we have to know is that we take the standard free energy and alter it in some way wh...
- Mon Feb 05, 2018 10:42 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Formula
- Replies: 2
- Views: 431
Re: Formula
The 3/2 is a number specific to monoatomic ideal gases. R, the ideal gas constant, is avogadro's number * Boltzmann's constant. This equation can be expressed in a different way as E = (3NK_{b}T)/2 , where N in the number of molecules. This shows that there is a direct relation between the n...
- Mon Feb 05, 2018 10:37 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: determining number of microstates
- Replies: 3
- Views: 431
Re: determining number of microstates
I'm not too certain that we will have to calculate the number of microstates for a specific molecule, but rather if the molecule can be in place A or place B. I think it'll more like probability in place A vs. place B and that is the number of microstates.
- Mon Feb 05, 2018 10:32 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: DG = 0 [ENDORSED]
- Replies: 3
- Views: 1071
Re: DG = 0 [ENDORSED]
We can also say that an endergonic process has a positive delta g and is non spontaneous, an exergonic process has a negative delta g and is spontaneous so it makes sense that a process at equilibrium has a delta g of zero.
- Mon Jan 29, 2018 6:44 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Calculating change in entropy for a process? (9.3)
- Replies: 2
- Views: 325
Re: Calculating change in entropy for a process? (9.3)
I think what the book is trying to say here is that the change in entropy (delta S) is going to be the same for an irreversible path or a reversible path. This is because they said entropy is a state function so all that matter is the final state minus the initial state and nothing in between.
- Mon Jan 29, 2018 6:37 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible vs Irreversible
- Replies: 4
- Views: 525
Re: Reversible vs Irreversible
A reversible reaction means that the system and the surroundings can be restored to the initial state from the final state without changing any thermodynamic properties. There are two main conditions for the reversible process to occur. 1) the process should occur in infinitesimally small increments...
- Mon Jan 29, 2018 6:30 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: entropy of heavy vs. light molecules
- Replies: 2
- Views: 816
Re: entropy of heavy vs. light molecules
I think a partial answer could stem from what Dr. Lavelle mentioned in class about the element with more electrons having greater entropy because there are more possible positions of the electrons. I think the same can be applied to your question ... if there is a heavy and light version of a simila...
- Tue Jan 23, 2018 8:32 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Exothermic
- Replies: 7
- Views: 837
Re: Exothermic
When a reaction feels cold then it is endothermic since it is taking in heat for the reaction. When a reaction is exothermic then it feels hot because heat is being released from the reaction.
- Tue Jan 23, 2018 8:28 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 5
- Views: 600
Re: Bond Enthalpies
I believe that bond enthalpies are the most unreliable method for calculating reaction enthalpies because the bond enthalpies are not specific to the specific molecules in the reaction. Instead, the bond enthalpies are averaged over many different molecules. For example, a C-H bond in one molecule m...
- Mon Jan 22, 2018 12:53 pm
- Forum: Phase Changes & Related Calculations
- Topic: ΔU vs. ΔH
- Replies: 10
- Views: 3548
Re: ΔU vs. ΔH
It might also be helpful to know the relationship between the two::
Precisely enthalpy is obtained from internal energy when the variable entropy S is substituted by the variable temperature T.
Precisely enthalpy is obtained from internal energy when the variable entropy S is substituted by the variable temperature T.
- Mon Jan 22, 2018 12:47 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Difference between U and H? [ENDORSED]
- Replies: 3
- Views: 7407
Re: Difference between U and H? [ENDORSED]
It could also be helpful to know the relationship between the two::
Enthalpy is obtained from internal energy when the variable entropy S is substituted by the variable temperature T.
Enthalpy is obtained from internal energy when the variable entropy S is substituted by the variable temperature T.
- Mon Jan 22, 2018 12:44 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Homework Week 3
- Replies: 1
- Views: 224
Re: Homework Week 3
I've heard that some TAs are saying CH 9 but we have hardly touched that so it might be better to focus on CH 8 since we have an upcoming test on that material as well.
- Thu Jan 18, 2018 11:23 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: enthalpy
- Replies: 3
- Views: 435
Re: enthalpy
In addition to these two types of enthalpies you might want to be familiar with enthalpies of fusion, enthalpies of vaporization and when to use them. I'm sure you won't have to memorize any values but just be aware of when to use them as we might get a problem of melting ice or something along thos...
- Tue Jan 16, 2018 6:25 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heat and Enthalpy
- Replies: 3
- Views: 424
Re: Heat and Enthalpy
Both heat and work are not state functions. Work can't be a state function because it depends on the distance an object is moved, which depends on the pathway. If work is not a state function then heat can't be either based on the first law of thermodynamics. Heat is energy transferred between the s...
- Tue Jan 16, 2018 5:07 pm
- Forum: Calculating Work of Expansion
- Topic: Expansion/Contraction
- Replies: 2
- Views: 213
Re: Expansion/Contraction
Another way of thinking about this type of problem is from the perspective of work. If there is no expansion / contraction on the system then work must be zero since there is no work being done on the system and the system is not doing work. Looking back to the equation, Delta U = q + w, then if wor...
- Tue Jan 16, 2018 5:03 pm
- Forum: Phase Changes & Related Calculations
- Topic: Gas Law
- Replies: 2
- Views: 382
Re: Gas Law
I think a good way of seeing whether or not to use the ideal gas law is based on the information that the problem gives you. If the problem gives you temp info, volume info and info about moles. Then we can work this equation and solve for pressure. Also, there may be problems where we have to know ...
- Wed Jan 10, 2018 3:43 pm
- Forum: Phase Changes & Related Calculations
- Topic: Exothermic Rxn
- Replies: 6
- Views: 669
Exothermic Rxn
So the example at the end of class was using bond enthalpies to calculate the rxn enthalpy. The answer came out to -58kj which is exothermic. I was thinking about this ... in order for this reaction to occur, you would have to take out 58kj from the system. So would you ever naturally find the react...
- Wed Jan 10, 2018 3:32 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy is a state property
- Replies: 13
- Views: 1806
Re: Enthalpy is a state property
The definition of a state function i some property whose value doesn't depend on the path taken to get there. Enthalpy is a state function because it only depends on the initial and final conditions, and not the path to establish these conditions. We can also see this from the equation :: ΔH=Hfinal−...
- Tue Jan 09, 2018 10:25 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Bomb and Coffee Cup Calorimeter [ENDORSED]
- Replies: 3
- Views: 697
Re: Bomb and Coffee Cup Calorimeter [ENDORSED]
It might also be important to note that in a bomb calorimeter there can be change in pressure while in a coffee cup calorimeter there is no change in pressure. We would use coffee cup calorimeters to directly find enthalpies since pressure is not changing and we would use bomb calorimeters to direct...
- Mon Jan 08, 2018 4:31 pm
- Forum: Student Social/Study Group
- Topic: Discussion Section
- Replies: 2
- Views: 418
Re: Discussion Section
Thank you!!
- Mon Jan 08, 2018 12:28 pm
- Forum: Student Social/Study Group
- Topic: Discussion Section
- Replies: 2
- Views: 418
Discussion Section
Does anybody know if discussion starts this week?
- Fri Dec 08, 2017 1:16 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: pKw
- Replies: 1
- Views: 5331
Re: pKw
In a soln. of water, the hydroxide conc multiplied by the hydronium conc is going to equal 1 X 10^-14. If you take the negative log of both sides of this eqn it shows you that the pH added to the pOH is going to equal 14. [H+] [OH-] = Kw = 1 X 10-14 Take the -log of both sides of the equation - log ...
- Tue Dec 05, 2017 5:52 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: pH in changing temperature
- Replies: 4
- Views: 1124
Re: pH in changing temperature
The pH of pure water decreases with increasing temp. If the pH falls and the temp is increased, this does not mean that water becomes more acidic at higher temps. For pure water, there is always the same concentration of hydrogen ions and hydroxide ions so water is still neutral (pH = pOH) even if i...
- Tue Dec 05, 2017 5:48 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Superacids and Superbases
- Replies: 1
- Views: 620
Re: Superacids and Superbases
According to the classical definition, a super acid is an acid with an acidity greater than that of 100% pure sulfuric acid. A super base is an extremely basic compound that has a high affinity for protons. Don't know too much besides their definition but hopefully this cleared up some things!
- Mon Dec 04, 2017 11:33 am
- Forum: General Science Questions
- Topic: Acidity [ENDORSED]
- Replies: 1
- Views: 704
Re: Acidity [ENDORSED]
I don't know the entire reason but this may be part of the reason why: In a biological system like the stomach, there is a double mucus layer. The inner mucus layer acts as a diffusion barrier for HCL while the outer cells secrete bicarbonate which dumb the pH down to a neutral pH at the cells surfa...
- Tue Nov 28, 2017 8:57 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Drawing 3D structures
- Replies: 1
- Views: 301
Re: Drawing 3D structures
I remember Dr. Lavelle saying that we won't be tested on our drawing skills so I don't think that we are going to be tested on how well our 3d drawings look. I think that we are going to be expected to visualize different types of molecular structures in our head and then manipulate them as we add l...
- Tue Nov 28, 2017 8:56 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE Box
- Replies: 3
- Views: 630
Re: ICE Box
If the reaction is going to the right then the products will gain some partial pressure so it will be a positive x value for the product and a negative x value for the reactants. The same is true for the opposite in which a reaction going to the left should have a negative x value for the products a...
- Mon Nov 27, 2017 5:19 pm
- Forum: Naming
- Topic: Naming -ate
- Replies: 2
- Views: 373
Re: Naming -ate
Sometimes we use the "ate" suffix to differentiate between whether it is a cation or an anion. In this specific situation, the coordination sphere has an overall negative charge and therefore we should be indicating that this is an anion.
- Mon Nov 27, 2017 5:15 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Backward Reaction
- Replies: 2
- Views: 556
Re: Backward Reaction
We know that at equilibrium the forwards reaction rate and the backwards reaction rate are equal to each other. When the reaction is favoring the reactants and going backwards, then we know that Q > K. Q is going to become less and less until it equals K and then the two will be at equilibrium. An e...
- Wed Nov 22, 2017 10:14 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: "Phase"
- Replies: 5
- Views: 552
Re: "Phase"
I assume you're just talking about the different phase states of molecules. The reactants and products could be in a gaseous phase when they are in the gaseous state. They could be in aqueous phase when dissolved and present as ions. They could be in solid phase when in a solid state but we don't in...
- Mon Nov 20, 2017 6:47 pm
- Forum: Hybridization
- Topic: Pi orbital structure
- Replies: 2
- Views: 228
Re: Pi orbital structure
I am fairly sure that any type of molecule that is held together by pi bonds is unable to rotate and will create a rigid planar structure for that molecule. When there are two pi bonds in place, rotation will become irrelevant since the molecule is linear. What I'm getting at is that if you flip the...
- Mon Nov 20, 2017 6:35 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 2
- Views: 244
Re: Bond Angles
We should know the bond angles of the ones that Dr. Lavelle went over in lecture. I think that most of them are fairly easy to figure out in that it is just basic geometry. Like if two atoms are in a line then you know that they are 180 degrees apart from one another just like 3 atoms would be 120 d...
- Fri Nov 17, 2017 1:05 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: General Understanding of Coordination Sphere
- Replies: 2
- Views: 499
Re: General Understanding of Coordination Sphere
A coordination sphere is the central metal ion plus the attached ligands of a coordination compound. There is a difference between the first and second coordination spheres which I don't think we are going to go into depth about ... but the first sphere refers to the molecules that are attached dire...
- Tue Nov 14, 2017 12:49 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 109.5 degrees
- Replies: 3
- Views: 906
Re: 109.5 degrees
You can also calculate the exact value of this tetrahedral angle using a cube and it's vertices. The exact value comes out to be \arccos (-1/3) = 109.4712206 I've attached the link below but I think for the purposes of this class, we should know that if there is a central molecule with 4 bon...
- Tue Nov 14, 2017 12:40 pm
- Forum: Hybridization
- Topic: How does hybridization arise?
- Replies: 1
- Views: 213
Re: How does hybridization arise?
Hybridization was brought about to explain molecular structure when the valence bond theory failed to correctly predict. According to our knowledge of valence bonding, carbon should form two covalent bonds, resulting in a CH2, because it has two unpaired electrons in its electronic configuration. Ho...
- Tue Nov 14, 2017 12:16 pm
- Forum: Hybridization
- Topic: Electrostatic potential
- Replies: 1
- Views: 295
Re: Electrostatic potential
Electrostatic potential has everything to do with dipole moments, electronegativity, and partial charge. Electrostatic potential helps us to know the relative polarity of a molecule. Negative electrostatic potential corresponds to a attraction of a proton by the concentrated electron density in the ...
- Wed Nov 08, 2017 1:44 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Materials [ENDORSED]
- Replies: 7
- Views: 803
Re: Midterm Materials [ENDORSED]
It's going to be given to us on the list of constants and equations so no need to memorize it!
- Mon Nov 06, 2017 12:35 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Materials [ENDORSED]
- Replies: 7
- Views: 803
Re: Midterm Materials [ENDORSED]
The definition of effective nuclear charge is the net charge that an electron experiences in an atom with multiple electrons. Basically as the number of electrons increases in an atom, the effective nuclear charge that the outermost electron feels is lowered. The effective nuclear charge can be calc...
- Mon Nov 06, 2017 12:30 pm
- Forum: Ionic & Covalent Bonds
- Topic: 3.25 d
- Replies: 3
- Views: 544
Re: 3.25 d
In the 1900's a man named Edwin Hill came up with a system of writing chemical formulas that is still used widely today. His system states that carbon atoms are listed first, hydrogen atoms next and then the number of all other elements in alphabetical order. There are many exceptions to his system ...
- Mon Nov 06, 2017 12:26 pm
- Forum: Lewis Structures
- Topic: When to use a double bond or triple bond [ENDORSED]
- Replies: 6
- Views: 47334
Re: When to use a double bond or triple bond [ENDORSED]
When figuring out whether to place a double or triple bond you should always look at the number of valence electrons present as well as the number of bonds a central atom is likely to form. Another good way to know whether to use double or single bonds is to calculate the formal charge on each atom ...
- Sun Nov 05, 2017 5:13 pm
- Forum: Lewis Structures
- Topic: Expanded Octets
- Replies: 2
- Views: 322
Re: Expanded Octets
Main group elements that form more bonds than what would be predicted by the normal octet rule are called hypervalent compounds. These compounds have an expanded octet meaning that there are more than eight electrons around one atom. The octet can be expanded by some elements by utilizing the empty ...
- Fri Nov 03, 2017 9:59 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbitals
- Replies: 2
- Views: 384
Re: Orbitals
I would go with the more specific answer with the principle quantum number in front of the letter.
- Wed Nov 01, 2017 11:12 am
- Forum: Trends in The Periodic Table
- Topic: Homework Problem 2.93
- Replies: 1
- Views: 338
Re: Homework Problem 2.93
Solutions Manual Error! I copied this from the link on Dr. Lavelle's website titled Solution Manual Errors :: In the picture, it shows A (smaller atom) + B (larger atom) --> C (larger ion) + D (smaller ion) The solution manual says that A=Na and B=Cl, and it references Figure 2.20 which explicitly l...
- Wed Nov 01, 2017 11:10 am
- Forum: Trends in The Periodic Table
- Topic: Noble Gas Electron Affinity
- Replies: 3
- Views: 1763
Re: Noble Gas Electron Affinity
I think that a trend still does hold true for the noble gases. You are right that it would require energy put into the system in order to attach another electron because the atoms already have a full octet. All of the halogens as well as the elements Beryllium and Magnesium have electron affinities ...
- Fri Oct 27, 2017 10:57 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Ti e- Configuration
- Replies: 1
- Views: 297
Re: Ti e- Configuration
The electron configuration for Titanium should be [Ar] 3d^2 4s^2 because the 3d orbital has a lower energy level when the electrons enter the 3d orbital so the 3d would be written before the 4s in this situation.
- Wed Oct 25, 2017 3:15 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Relation of radius/diameter size to precision
- Replies: 3
- Views: 551
Re: Relation of radius/diameter size to precision
The Heisenberg Uncertainty Equation can be stated as following:: \Delta p \Delta x \geq \frac{h}{4\pi } We can either know momentum to extreme precision or position to extreme precision but either way it has to be greater than or equal to Planck's Constant divided by 4pi. So in the problem, as the u...
- Wed Oct 25, 2017 12:23 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 3d and 4s orbitals
- Replies: 1
- Views: 266
Re: 3d and 4s orbitals
When we begin to enter the 4s orbital with the elements potassium and calcium, the 4s orbital has a lower energy than the 3d orbital which is why the 4s orbital is filled first. Then as we enter the 3d orbitals, for reasons which I believe we have not been taught or reasons too complicated, the ener...
- Wed Oct 25, 2017 12:12 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Helium block
- Replies: 2
- Views: 712
Re: Helium block
I think to answer this question a distinction needs to be made between blocks and groups. The reason why Helium is considered a noble gas is because it's outermost shell is fully occupied by its 2 electrons. However, when you look at the electron configuration of Helium on the Periodic Table, you ca...
- Tue Oct 24, 2017 11:23 am
- Forum: Trends in The Periodic Table
- Topic: 2.93
- Replies: 1
- Views: 332
Re: 2.93
Solutions Manual Error! I copied this from the link on Dr. Lavelle's website titled Solution Manual Errors :: In the picture, it shows A (smaller atom) + B (larger atom) --> C (larger ion) + D (smaller ion) The solution manual says that A=Na and B=Cl, and it references Figure 2.20 which explicitly l...
- Tue Oct 24, 2017 11:19 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: principal quantum numbers
- Replies: 2
- Views: 575
Re: principal quantum numbers
The most important factor which influences the energy of an orbital is the size which is related to the principal quantum number. For an atom that contains just 1 electron there is no difference between the energies in the different subshells. As soon as an atom contains more than 1 electron, the di...
- Mon Oct 16, 2017 9:46 pm
- Forum: DeBroglie Equation
- Topic: Post Module #34
- Replies: 1
- Views: 360
Re: Post Module #34
Well for this problem right off the bat I believe the correct answer is C. We can obtain the first value by manipulating the de broglie equation and solving for speed like so :: v = \frac{h}{\lambda m} Now to figure out what makes this a reasonable speed ... Dr. Lavelle told us in lecture today that...
- Mon Oct 16, 2017 9:37 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Really confused on some multiple choice questions. Please Help!
- Replies: 1
- Views: 4469
Re: Really confused on some multiple choice questions. Please Help!
15. C - Only specific wavelengths of light are absorbed or emitted. Spectrum consists of lines. This is because only certain wavelengths (and therefore frequencies) match the energy difference from one energy level to the next. So only certain wavelengths of light could possibly be absorbed / emitt...
- Mon Oct 16, 2017 6:09 pm
- Forum: Photoelectric Effect
- Topic: Post Module #25
- Replies: 2
- Views: 304
Re: Post Module #25
The correct answer is D for this question. The results of the photoelectric experiments came as a surprise to scientists because light was not acting like a typical wave in that when intensity was increased, energy was increased. Instead the photoelectric experiments showed that when the frequency o...
- Mon Oct 16, 2017 1:07 pm
- Forum: Properties of Light
- Topic: Homework Week of 10/16 [ENDORSED]
- Replies: 2
- Views: 419
Re: Homework Week of 10/16 [ENDORSED]
I believe that since we have only covered up to de broglie in lecture we should only be expected to cover homework up to that point. Dr. Lavelle has told us that the test on Wednesday will only cover assigned homework problems 3 to 41 from Chapter 1 so these are the types of problems we are currentl...
- Mon Oct 16, 2017 1:02 pm
- Forum: DeBroglie Equation
- Topic: Large Objects and Wavelike Properties [ENDORSED]
- Replies: 1
- Views: 640
Re: Large Objects and Wavelike Properties [ENDORSED]
Yes all matter exhibits wave particle duality. This means that matter is best described not only as a wave or not only as a particle but as both. These large object have wavelike properties according to de broglie even though these wavelengths are too small to detect. Let us just say that we can onl...
- Fri Oct 13, 2017 1:11 pm
- Forum: Photoelectric Effect
- Topic: hw problem 1.33 c
- Replies: 3
- Views: 1195
Re: hw problem 1.33 c
For part C, the question is asking for the wavelength of the electromagnetic radiation that hit the metallic surface. We also know that the energy of a singular incoming photon, E, is equal to the work function added to the kinetic energy of the electron. This is because the energy that was put into...
- Wed Oct 11, 2017 12:40 pm
- Forum: Properties of Light
- Topic: 1.13
- Replies: 2
- Views: 411
Re: 1.13
You can also think of the equation to be \nu = -R((1/n(final)^2)- 1/n(initial)^2)) . This might make things a little bit clearer because the change in energy levels is going from 4, which is the initial state, and ending at 2, which is the finial state, because th...
- Wed Oct 11, 2017 12:35 pm
- Forum: Properties of Light
- Topic: Rydberg's Formula
- Replies: 4
- Views: 574
Re: Rydberg's Formula
By looking at all of the lines in the spectrum of hydrogen atoms, an empirical model was derived that explains emission patterns of hydrogen atoms. The frequencies (or wavelength or energy) could be predicted based upon the Rydberg constant and two integers. One integer is meant to represent the ini...
- Wed Oct 11, 2017 12:29 pm
- Forum: Properties of Light
- Topic: 1.15 Homework Question
- Replies: 2
- Views: 365
Re: 1.15 Homework Question
The question states that the emission given off is in the ultraviolet so we know that it is in the Lyman Series. From this we know that n1 = 1. I think any problem has to give us some clue as to which energy level it is referring to or else we would have to resort to guess and check methods. From th...
- Tue Oct 10, 2017 2:45 pm
- Forum: Properties of Electrons
- Topic: Energy Levels [ENDORSED]
- Replies: 1
- Views: 426
Re: Energy Levels [ENDORSED]
The question states that the emission given off is in the ultraviolet so we know that it is in the Lyman Series. From this we know that n2 = 1. I think any problem has to give us some clue as to which energy level it is referring to or else we would have to resort to guess and check methods. From th...
- Wed Oct 04, 2017 5:17 pm
- Forum: Limiting Reactant Calculations
- Topic: Net Ionic Equation
- Replies: 4
- Views: 3791
Re: Net Ionic Equation
So the net ionic equation from my understanding is basically getting rid of anything that didn't participate in the reaction. A net ionic equation gets rid of all spectator ions. So our equation is :: Cu(NO3)2 (aq) + 2 NaOH (aq) --> Cu(OH)2 (s) + 2NaNO3 (aq) We then write out the total ionic equatio...
- Tue Oct 03, 2017 1:13 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Help with G9 [ENDORSED]
- Replies: 2
- Views: 583
Re: Help with G9 [ENDORSED]
For question G9 you don't actually use the M[i]V[i] = M[f]V[f]. Instead we'll be using the M = n/V. In this problem they are asking for the mass of silver nitrate which needs to be added into the 500.0 ml flask for the molarity to equal 0.179 M. The way we'll find mass from the information given is ...
- Tue Oct 03, 2017 11:58 am
- Forum: Limiting Reactant Calculations
- Topic: help with question
- Replies: 2
- Views: 875
Re: help with question
To find the limiting reagent you need to convert both grams of C6H9Cl3 and AgNO3 to moles. So you take the 0.750g C6H9Cl3 and divide it by its molar mass of 187.50 g/mol and you'll have 0.004 mol C6H9Cl3. Do the same for AgNO3 which will be 1000. g AgNO3 divided by its molar mass of 169.88 g/mol and...