Search found 103 matches
- Thu Mar 12, 2020 10:49 am
- Forum: Student Social/Study Group
- Topic: Thoughtful Poetry Time
- Replies: 3
- Views: 543
Thoughtful Poetry Time
Post all thoughtful poetry here!
- Wed Mar 11, 2020 1:43 pm
- Forum: *Enzyme Kinetics
- Topic: Do we need to know enzyme kinetics for the final? [ENDORSED]
- Replies: 4
- Views: 911
Re: Do we need to know enzyme kinetics for the final? [ENDORSED]
On the chemical kinetics outline, it does not mention anything specifically about enzymes. But I would know how enzymes work as catalysts.
- Wed Mar 11, 2020 1:42 pm
- Forum: *Enzyme Kinetics
- Topic: Elementary Steps
- Replies: 2
- Views: 649
Re: Elementary Steps
Also, cell potential only refers to electrochemistry, more specifically redox reactions. In kinetics, elementary steps are used to find the reaction mechanism that matches the rate law... they usually wont have a given cell potential as these are usually not reduction or oxidation reactions.
- Wed Mar 11, 2020 12:51 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation Energy vs. Free Energy of Activation
- Replies: 3
- Views: 327
Re: Activation Energy vs. Free Energy of Activation
^^^ does this mean that it is literally Gibbs free energy??
- Wed Mar 11, 2020 12:50 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: adsorption
- Replies: 2
- Views: 273
Re: adsorption
^^^ like they said, most heterogenous catalysts work by simply giving the reactants more surface area to react on. I believe that is all you will need to know about adsorption!
- Wed Mar 11, 2020 12:49 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius Equation A variable
- Replies: 2
- Views: 192
Re: Arrhenius Equation A variable
Since A has to be solved for experimentally, we should be given it if it is needed in the equation. I think we will mostly be using the Arrhenius equation to solve for different values of k
- Wed Mar 11, 2020 12:48 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius Equation A variable
- Replies: 3
- Views: 260
Re: Arrhenius Equation A variable
Since A must be solved for experimentally, I don't think we will have to know how to find it.
- Wed Mar 04, 2020 6:36 pm
- Forum: First Order Reactions
- Topic: definition of first order
- Replies: 2
- Views: 273
Re: definition of first order
You can also tell by looking at the graphs of the reactions concentration over time. For a zero order reaction, the graph will be linear if you plot concentration over time. For first order, the graph will be linear if you plot ln(concentration) over time, implying an exponential relationship. For 2...
- Wed Mar 04, 2020 6:33 pm
- Forum: First Order Reactions
- Topic: Order of the Reaction
- Replies: 2
- Views: 237
Re: Order of the Reaction
As for the slow part in your notes, Lavelle was trying to emphasize that the rate is only dependent on the slowest step in the reaction mechanism. Think of his brownie analogy, if a group is making brownies and it takes 5 minutes to make the batter but 25 minutes to bake the brownies, then it no mat...
- Wed Mar 04, 2020 6:24 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: reactant vs product
- Replies: 4
- Views: 435
Re: reactant vs product
^^what they said, and I also think Lavelle mentioned that the rate of products formed is the same as the rate for reactants but with the opposite sign. Can someone confirm that I am remembering correctly?
- Wed Mar 04, 2020 6:22 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Overall reaction order
- Replies: 3
- Views: 310
Re: Overall reaction order
if it helps to visualize, if the reaction is expressed by k[A}^2[B]^3, then the overall reaction order would be 2+3, so 5.
- Wed Mar 04, 2020 6:20 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: observing initial rates
- Replies: 3
- Views: 296
Re: observing initial rates
It is good to measure at close to t=0 because there will only be reactants present and no products formed. If there are products present then there is a high chance that the reverse reaction is occurring simultaneously so it will be hard to determine the rate.
- Wed Mar 04, 2020 6:16 pm
- Forum: General Rate Laws
- Topic: Determining Order
- Replies: 6
- Views: 479
Re: Determining Order
^^ like they said, and how you determine the m and n is the coefficients of the reactants in the overall reaction
- Tue Feb 25, 2020 12:32 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy and K
- Replies: 5
- Views: 448
Re: Gibbs Free Energy and K
You can relate Gibbs free energy to K using the following equation: ∆Gº = -RTlnK As you can see, this is not dependent on pressure or temperature. However, the max work that can be done is given by ∆G at constant pressure and temperature. Hope this helped! You said that this isnt dependent on tempe...
- Tue Feb 25, 2020 12:26 pm
- Forum: Balancing Redox Reactions
- Topic: 6K1
- Replies: 3
- Views: 275
Re: 6K1
^^ because this reaction is in acidic solution, for each half reaction balance excess oxygen with H2O and then add H+ to the other side to balance excess H+. Then use electrons to make sure the charges are balanced.
- Tue Feb 25, 2020 12:22 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Max Cell Potential and Free Energy Difference
- Replies: 2
- Views: 244
Re: Max Cell Potential and Free Energy Difference
deltaG and E can be related by the equation: deltaG = -nFE
- Tue Feb 25, 2020 12:19 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Concentration Cells
- Replies: 2
- Views: 206
Re: Concentration Cells
I believe we use a porous disk so that ions can move through to either side until their concentrations reach equilibrium. I don't think this would happen if a salt bridge was used
- Tue Feb 25, 2020 12:17 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: standard potential of a redox reaction
- Replies: 3
- Views: 304
Re: standard potential of a redox reaction
I have written down that standard energy potential is an intensive property and so it doesn't depend on how many times the reaction occurs, it is always the same. However, reaction potentials are only given for reduction reactions so if your half reaction is an oxidation then you must flip the sign ...
- Tue Feb 25, 2020 12:13 pm
- Forum: Balancing Redox Reactions
- Topic: Acid and Bases in Redox Reaction
- Replies: 4
- Views: 400
Re: Acid and Bases in Redox Reaction
The question will usually state if the reaction is taking place in a basic or acidic conditions. Usually you will need to use H2O to balance excess oxygen, when you do this you will then add either H+ or OH- to the other side of the reaction to then balance the excess hydrogen from the H2O. If it is...
- Thu Feb 20, 2020 1:18 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic/Voltaic Cells
- Replies: 2
- Views: 216
Re: Galvanic/Voltaic Cells
Galvanic cells are related to a positive standard cell potential, which means the process will occur naturally without work having to be put in (spontaneously). Voltaic is another term for Galvanic. On the other hand, an electrolytic cell is related to a negative standard cell potential, so the proc...
- Thu Feb 20, 2020 1:13 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox Reactions in Basic Solution
- Replies: 4
- Views: 345
Re: Balancing Redox Reactions in Basic Solution
^^To go off what they said, you add H+ to balance the hydrogens and then add the same amount of OH- to both sides. The H+ and OH- that is on the same side will combine to form H2O
- Thu Feb 20, 2020 1:10 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation numbers
- Replies: 8
- Views: 589
Re: oxidation numbers
There are several molecules with known oxidation numbers, for example O is known to have an oxidation number of -2. Using the known oxidation numbers you can solve for oxidation numbers of other molecules, for example if you have the molecule MnO4 with an overall charge of -1, then you know that Mn ...
- Thu Feb 20, 2020 1:07 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation numbers
- Replies: 3
- Views: 255
Re: oxidation numbers
Yes, for example if Cr^6+ changes to Cr^3+, then you know it was reduced because the half reaction would be Cr^6+ + 5e- --> Cr^3+
- Thu Feb 20, 2020 1:04 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation numbers
- Replies: 5
- Views: 339
Re: oxidation numbers
It is helpful to know all the oxidation numbers and that is one way to do it, but there are several other ways as well. We will usually be given a table of reduction reactions with there E values, so you can tell from that as well. It also helps to look at oxygen, because that is where the root of t...
- Tue Feb 11, 2020 4:39 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: ∆G, ∆H, ∆S
- Replies: 6
- Views: 560
Re: ∆G, ∆H, ∆S
^^ as they said above, in order for a spontaneous reaction to occur, deltaG must be negative. This means that the value for T*deltaS must be greater than the change in enthalpy. For an endothermic reaction where enthalpy is a positive number this is often not true except at very high temperatures.
- Tue Feb 11, 2020 4:35 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Ideal gas heat capacity
- Replies: 1
- Views: 176
Re: Ideal gas heat capacity
The ideal gas heat capacity at constant pressure (Cv) is represented as 3/2R for a monoatomic gas. This is different from a substance like water, where the heat capacity is 4.186 J/g*C, where J represents joules supplied in the form of heat. As you can see, the heat capacity of a monoatomic gas does...
- Tue Feb 11, 2020 4:31 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: How to think of entropy?
- Replies: 2
- Views: 114
Re: How to think of entropy?
^^ While what they said is true, positional entropy is only one kind of entropy. For example there is also entropy when there is a volume, pressure, and temperature change in a system. There is nothing wrong with thinking of it as disorder, I think lavelle just doesn't want us to think that way beca...
- Tue Feb 11, 2020 4:26 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Relationship between Delta S Surroundings and Delta S System
- Replies: 1
- Views: 207
Re: Relationship between Delta S Surroundings and Delta S System
deltaS(surr)=-deltaS(sys) only under reversible conditions. So this means isothermal.
- Tue Feb 11, 2020 4:23 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Comparing standard molar entropies
- Replies: 6
- Views: 490
Re: Comparing standard molar entropies
Larger molecules have more particles and therefore have a greater positional entropy value. For example an element with more particles (electrons, protons, and neutrons) (such as Pb vs C) will have a larger degeneracy number, where W=#microstates^(#particles). Then use the equation S=kb(lnW) to solv...
- Sun Feb 09, 2020 11:28 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Constant T,P,V
- Replies: 4
- Views: 186
Re: Constant T,P,V
the question will specify, for example if it says the volume increased from 20M to 25M then u know the volume changed... use the context clues in the question
- Sun Feb 09, 2020 11:27 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: q rev
- Replies: 9
- Views: 344
Re: q rev
Also notice that this equation can't be used if there is change in V, P, or T, because you have to use one other equations. This also implies reversibility.
- Sun Feb 09, 2020 11:24 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Internal Energy equations
- Replies: 1
- Views: 80
Re: Internal Energy equations
You should know (delta)U=q+w, (delta)H=(delta)U+p(delta)V, which can also be written as (delta)H=(delta)U+nR(delta)T. Also know when change in V is 0, (delta)U=q, and when q=0, (delta)U=w. And when there is no change in temperature there is no change in U so that means q=-w.
- Sun Feb 09, 2020 11:20 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Heat capacity
- Replies: 6
- Views: 276
Re: Heat capacity
Yes. Ideal gas Monoatomic molecules have a heat capacity of 3/2R while linear molecules will have a heat capacity of 5/2R because they can have more degrees of motion.
- Sun Feb 09, 2020 11:17 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Reactions at constant pressure
- Replies: 2
- Views: 108
Re: Reactions at constant pressure
I think it's because it is very difficult to change the volume of solids and liquids by a significant amount.
- Fri Jan 31, 2020 8:25 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Value of q
- Replies: 11
- Views: 593
Re: Value of q
This also makes sense if you think about the law of conservation of energy, because energy can never be created or destroyed, only transferred. Therefore if a system loses energy that means that its surroundings gain that energy and vice versa.
- Fri Jan 31, 2020 8:22 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Reversible Process
- Replies: 4
- Views: 179
Re: Reversible Process
In lecture, Lavelle said that a system at equilibrium is a reversible system. I am kind of confused on what kind of system would be irreversible?
- Fri Jan 31, 2020 8:20 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: q=nCT
- Replies: 2
- Views: 1573
Re: q=nCT
^^^ like they said, pay attention to the specific heat given. If you are given molar heat capacity (Cm), you use moles (n). If you are given specific heat capacity (Csp), then use grams. Make sure the units match!
- Fri Jan 31, 2020 8:14 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 4A.13
- Replies: 4
- Views: 146
Re: 4A.13
just think about the law of conservation of energy. energy cannot be created or destroyed, only transferred. So the positive q(reactants) must have come from a -q(calorimetry).
- Fri Jan 31, 2020 8:13 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Max Heat Capacity
- Replies: 4
- Views: 133
Re: Max Heat Capacity
heat capacity is a constant depending on the substance. The substance will have different heat capacities depending on what phase it is in.
- Sat Jan 25, 2020 1:05 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Pressure and Enthalpy
- Replies: 5
- Views: 151
Re: Pressure and Enthalpy
When you are calculating enthalpy, I'm pretty sure the pressure has to be constant. Otherwise the changes in pressure would change the enthalpies as well.
- Sat Jan 25, 2020 1:00 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: state functions
- Replies: 4
- Views: 1059
Re: state functions
A state function, like the ones mentioned above, describe the current state of the system regardless of how the system arrived at that state. So temperature is a state function while heat is not.
- Sat Jan 25, 2020 12:58 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 5
- Views: 158
Re: Hess's Law
if something is a state property, that means be addition and subtraction can be used on it. So Hess's law relates to this because you can add enthalpies of reactions together to find the overall enthalpy of reaction
- Sat Jan 25, 2020 12:49 pm
- Forum: Phase Changes & Related Calculations
- Topic: 4B.3
- Replies: 1
- Views: 59
Re: 4B.3
Work is a positive value when more work is done by the system than on it. So if the value for work is negative, then work was done on the system. If the value for work is positive, then work was done by the system
- Sat Jan 25, 2020 12:45 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heat vs. Enthalpy
- Replies: 6
- Views: 187
Re: Heat vs. Enthalpy
The total heat added to or lost from a system is the enthalpy. Enthalpy can only be calculated if the system is at a constant pressure. Heat is just the difference in temperature
- Thu Jan 16, 2020 1:18 pm
- Forum: Ideal Gases
- Topic: "omitting" the units
- Replies: 7
- Views: 660
Re: "omitting" the units
But in this course often a question will ask for a specific K, like Kc or Kp. In this case, make sure your units match with what the question is asking for. But K does not necessarily have to have this specificity
- Thu Jan 16, 2020 1:15 pm
- Forum: Ideal Gases
- Topic: approximate ideal gas law
- Replies: 3
- Views: 165
Re: approximate ideal gas law
The ideal gas law assumes that the gases are their ideal state when it is used. This might not be true, but especially for this course we always assume that the gases are at their ideal state so that we can use the equation.
- Thu Jan 16, 2020 1:13 pm
- Forum: Ideal Gases
- Topic: ICE tables
- Replies: 9
- Views: 1510
Re: ICE tables
If the questions asks for just K, and not Kc or Kp, then you need to look at the equation. If the reactants and products are gases then you should use Kp, because it is implied. If the reactants and products of the equation are aqueous then you should use Kc because it is implied. However if it ask...
- Thu Jan 16, 2020 1:04 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5J.5 d
- Replies: 3
- Views: 168
Re: 5J.5 d
Adding an inert gas never changes the equilibrium constant or pressures of the gases reacting in the equation so I think that explanation is sufficient
- Sun Jan 12, 2020 11:02 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding inert gas [ENDORSED]
- Replies: 9
- Views: 307
Re: Adding inert gas [ENDORSED]
How do you tell which gases are inert gases? is it any gas that doesnt react in the chemical equation?
- Sat Jan 11, 2020 3:42 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Reaction Quotient > Equilibrium Constant
- Replies: 4
- Views: 208
Re: Reaction Quotient > Equilibrium Constant
Since the reaction goes both ways you can think of products being a reactant for the reverse reaction. This helps me think about it because you can just write the reaction with both
- Sat Jan 11, 2020 3:30 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Temperatures and Equilibrium
- Replies: 4
- Views: 166
Re: Temperatures and Equilibrium
Each reaction has a different K's that correspond with different temperatures. This is why the temperature is often given in the question
- Sat Jan 11, 2020 3:29 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Reaction quotient
- Replies: 8
- Views: 428
Re: Reaction quotient
^^^ to go off what they said, if Q=K then the reaction is at equilibrium, so the concentrations would be the same as well
- Sat Jan 11, 2020 3:25 pm
- Forum: Ideal Gases
- Topic: converting Kc to Kp
- Replies: 13
- Views: 464
Re: converting Kc to Kp
When asked the equilibrium constant of a chemical reaction involving gases, do we solve for Kc or Kp? The question will probably ask what to solve for; either Kc or Kp, because for gases you can solve for either. if they give you partial pressures in the question than solve for Kp and if they give ...
- Sat Jan 11, 2020 3:11 pm
- Forum: Ideal Gases
- Topic: K vs Q [ENDORSED]
- Replies: 7
- Views: 616
Re: K vs Q [ENDORSED]
^^^what they said is true, but ALSO Q is useful to use when you are trying to see where the reaction is in comparison to equilibrium, so like when Q is less than K then you know that more products need to be formed to reach equilibrium, when Q > K you know that more reactants need to be formed to re...
- Fri Dec 06, 2019 11:36 am
- Forum: Trends in The Periodic Table
- Topic: Atomic Radius vs Ionic Radius
- Replies: 3
- Views: 415
Re: Atomic Radius vs Ionic Radius
Also the radius of an anion will be bigger than its parent's atom because the added electron(s) will lead to more repulsion. The radius of a cation will have a smaller radius than it's parent atom because the remaining electrons will be pulled closer to the nucleus
- Fri Dec 06, 2019 9:45 am
- Forum: Identifying Acidic & Basic Salts
- Topic: deciding whether the solution of a salt is basic, acidic, or neutral
- Replies: 5
- Views: 662
Re: deciding whether the solution of a salt is basic, acidic, or neutral
Also if you are making a mixture of a strong acid and a strong base with the same concentration, the resulting salt and solution will be neutral; you can think of the acid and base cancelling each other out. If you mix a strong acid with a weak base, the resulting solution will be acidic (although w...
- Fri Dec 06, 2019 9:36 am
- Forum: Lewis Acids & Bases
- Topic: Lewis Acids/Bases vs Bronsted
- Replies: 1
- Views: 195
Re: Lewis Acids/Bases vs Bronsted
A bronsted acid is a proton donor, and a bronsted base is a proton acceptor. This is easy to see in chemical reactions, because you can usually see the transfer of H+ going on. For example, HCl + H2O --> H3O + Cl, HCl is the bronsted base because it donated an H+ to H20, in this case the bronsted ac...
- Fri Dec 06, 2019 9:25 am
- Forum: Bronsted Acids & Bases
- Topic: HCl, HBr, HI, etc.
- Replies: 2
- Views: 235
Re: HCl, HBr, HI, etc.
You can also think of it in terms of bond length; since the bond between H-I is the longest it is the strongest acid because that bond will be easier to break, so it will dissociate the easiest. HI>HBr>HCl>HF. HF is a weak acid because F's high electronegativity and small size makes that bond short ...
- Fri Dec 06, 2019 9:20 am
- Forum: Bronsted Acids & Bases
- Topic: Determining Strong Acids
- Replies: 1
- Views: 195
Re: Determining Strong Acids
Strong acids dissociate the easiest, so a longer bond length between H and an atom will mean a stronger acid. This is why HI is a stronger acid than HCl. When comparing weak acids, look at the stability of the conjugate base that is left over after the acid is deprotonated. A more stable conjugate b...
- Sat Nov 30, 2019 4:42 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Drawing sigma & Pi bonds
- Replies: 7
- Views: 642
Re: Drawing sigma & Pi bonds
^^^ I am not sure if we have to draw them but it we definitely have to label them and know that pi bonds restrict rotation
- Sat Nov 30, 2019 4:40 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: paramagnetism
- Replies: 8
- Views: 707
Re: paramagnetism
if a paramagnetic electron means it is unpaired, then does that mean the molecule is radical? okay I thought about this more and I am going to answer my own question, I realized that a paramagnetic electron from one atom could bond with a paramagnetic electron from another atom so it is not always ...
- Sat Nov 30, 2019 4:39 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: paramagnetism
- Replies: 8
- Views: 707
Re: paramagnetism
if a paramagnetic electron means it is unpaired, then does that mean the molecule is radical?
- Sat Nov 30, 2019 4:33 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: dipole-dipole in a solid phase vs gas phase
- Replies: 15
- Views: 1207
Re: dipole-dipole in a solid phase vs gas phase
Nathan Rothschild_3D wrote:So is solid stronger or are they both the same? or does it depend on the molecule, not the state
I think it is safe to say that the intermolecular forces in a solid compound are generally stronger than in a gas phase
- Sat Nov 30, 2019 4:15 pm
- Forum: Amphoteric Compounds
- Topic: Examples of amphoteric compounds
- Replies: 5
- Views: 342
Re: Examples of amphoteric compounds
The diagonal band they are referring to includes Be, Al, Ga, Sn, Sb, and Pb. The examples Lavelle used in class were all bonded with oxygen, so BeO, Al2O3, Ga2O3, SnO2, SbO5, and PbO2
- Fri Nov 22, 2019 9:02 am
- Forum: Dipole Moments
- Topic: Determining intermolecular forces
- Replies: 4
- Views: 239
Re: Determining intermolecular forces
if it is nonpolar then it will only be affected by dispersion forces. If it is non-polar it will be affected by dipole-dipole forces. if there are H bonded to N,O,F then it will experience H bonding.
- Fri Nov 22, 2019 9:00 am
- Forum: Dipole Moments
- Topic: Cancelling Dipole Moments
- Replies: 4
- Views: 376
Re: Cancelling Dipole Moments
Since in tetrahedral molecules there are no molecules directly opposite one another, the only way it will be nonpolar is if all of the surrounding atoms are the same
- Fri Nov 22, 2019 8:57 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polar vs. Nonpolar
- Replies: 6
- Views: 319
Re: Polar vs. Nonpolar
I understand that CH2Cl2 is polar because a tetrahedral shape isn't completely symmetrical. However if a shape is symmetrical like a square planar would it be considered nonpolar? For example if it was a square planar with two Cl and two H atoms around a central atom, would it be considered non pol...
- Fri Nov 22, 2019 8:52 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Tetrahedral and its polarity
- Replies: 6
- Views: 414
Re: Tetrahedral and its polarity
If you have a molecule like CHF3, it will be polar because not all of the atoms surrounding the C are the same, but will that affect the bond angles or do you still assume that it is 109.5
- Fri Nov 22, 2019 8:48 am
- Forum: Hybridization
- Topic: hybridizing d orbitals
- Replies: 7
- Views: 454
Re: hybridizing d orbitals
are we going to have to know the d hybridizations or are we only supposed to know the p hybridizations?
- Sun Nov 17, 2019 1:23 pm
- Forum: Bond Lengths & Energies
- Topic: Interaction Potential Energy equation
- Replies: 7
- Views: 479
Re: Interaction Potential Energy equation
my TA said there are no calculations you will really have to do on the test, but you do need to know the concepts behind the equations
- Sun Nov 17, 2019 1:21 pm
- Forum: Bond Lengths & Energies
- Topic: Bond lengths
- Replies: 8
- Views: 417
Re: Bond lengths
also don't bond lengths depend on the atoms, ie a bond between two very electronegative atoms would be shorter? also has to do with atomic radius
- Sun Nov 17, 2019 1:14 pm
- Forum: Dipole Moments
- Topic: Dipole-Dipole vs. Dipole-Induced Dipole
- Replies: 3
- Views: 149
Re: Dipole-Dipole vs. Dipole-Induced Dipole
are dipole-induced dipole forces the ones that are always present in everything?
- Sun Nov 17, 2019 1:12 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Van Der Waals Interaction
- Replies: 11
- Views: 641
Re: Van Der Waals Interaction
^^^ what they said, van der waals forces are constant but also constantly changing, that is why it is useful to think of them as induced-diple induced-dipole forces
- Sun Nov 17, 2019 1:08 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs
- Replies: 5
- Views: 325
Re: Lone Pairs
u can think of lone pairs as another region of electron density, so it will effect the shape as if there was another bonding pair
- Fri Nov 08, 2019 8:57 am
- Forum: Dipole Moments
- Topic: Drawing Unpaired Electrons
- Replies: 7
- Views: 353
Re: Drawing Unpaired Electrons
if you have lone pairs it will also affect your dipole moment, so lone pairs are important
- Fri Nov 08, 2019 8:54 am
- Forum: Dipole Moments
- Topic: How do i know if a molecule has a dipole moment?
- Replies: 7
- Views: 400
Re: How do i know if a molecule has a dipole moment?
^^^ not all bonds between different elements produce a dipole because you have to take molecular shape into account. For example, in a symmetric molecule like CCl4 there would be dipoles between the C-Cl bonds, but they would all cancel each other out because of the symmetrical shape of the molecule
- Fri Nov 01, 2019 3:13 pm
- Forum: Octet Exceptions
- Topic: Expanded Valence Shells
- Replies: 3
- Views: 265
Re: Expanded Valence Shells
what is the most electrons an expanded valence shell can have? 10? 14? is it different for different atoms?
- Fri Nov 01, 2019 3:07 pm
- Forum: Octet Exceptions
- Topic: More than 8 e-
- Replies: 3
- Views: 171
Re: More than 8 e-
does the d shell have to be completely empty? I thought it could be partially full also
- Fri Nov 01, 2019 3:03 pm
- Forum: Octet Exceptions
- Topic: Exceptions to the Octet Rule
- Replies: 3
- Views: 106
- Fri Nov 01, 2019 3:03 pm
- Forum: Octet Exceptions
- Topic: Exceptions to the Octet Rule
- Replies: 3
- Views: 106
Re: Exceptions to the Octet Rule
What they said above, and the reason they don't stay very long is because the unpaired electron will make it very reactive as it will attempt to par that electron
- Fri Nov 01, 2019 3:01 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Central atom
- Replies: 8
- Views: 362
Re: Central atom
do resonance structures depend only on the FC of central atom or on all of the atoms
- Fri Oct 25, 2019 1:33 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bond length
- Replies: 11
- Views: 459
Re: Bond length
Will bond length be given to us on tests or are we supposed to know bond lengths/assume resonance? Do you just base your lewis structure on the lowest formal charge?
- Fri Oct 25, 2019 1:31 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Orbital Box Diagram
- Replies: 5
- Views: 537
Re: Orbital Box Diagram
Just to confirm, we would draw all the up arrows first for a specific subshell and then start filling in all the down arrows right? Yes, this is because you would fill all unpaired electrons first, and when electrons are unpaired they have parallel spin. then, when you go to fill in the pairs you w...
- Fri Oct 25, 2019 1:28 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Energy of Electrons
- Replies: 6
- Views: 240
Re: Energy of Electrons
It is kind of confusing because the electrons closest to the nucleus take more energy to remove from the atom. so how come electrons in shells that are further away have more energy?
- Fri Oct 25, 2019 1:25 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Energy of spdf orbitals
- Replies: 11
- Views: 400
Re: Energy of spdf orbitals
705198479 wrote:is there a rule that restricts a sub shell ? is it important to remember for this class?
you should know how many electrons each shell can hold; the s shell can only hold 2, p holds 6, d holds 10 and f holds 14
- Fri Oct 25, 2019 1:22 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Spin Quantum Number
- Replies: 6
- Views: 231
Re: Spin Quantum Number
It is also good to know that when electrons are paired, they have opposite spins. when electrons are unpaired but in the same orbital, they have parallel spins
- Fri Oct 18, 2019 9:18 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Bohr's Equation
- Replies: 5
- Views: 244
Re: Bohr's Equation
considering we get a list of equations and constants, i dont think you need to derive any equations. rearranging equations perhaps, but i wouldnt worry about it
- Fri Oct 18, 2019 9:14 am
- Forum: *Shrodinger Equation
- Topic: Quantum Number
- Replies: 2
- Views: 201
Re: Quantum Number
the fourth number represents the spin state of that same electron, so it can't be used to describe other electrons. The fourth number only indicates if the electron is spinning up or down.
- Fri Oct 18, 2019 9:11 am
- Forum: Properties of Electrons
- Topic: Relationship between Speed and Frequency
- Replies: 3
- Views: 166
Re: Relationship between Speed and Frequency
as the person above said, de broglies equation can only be used for particles with a resting mass. Since light does not have a resting mass, the equations are not interchangeable.
- Fri Oct 18, 2019 9:09 am
- Forum: Properties of Light
- Topic: Unit for Wavelength
- Replies: 34
- Views: 2507
Re: Unit for Wavelength
while nanometers is common for wavelength, so is picometers, or leaving your answers in meters. honestly you could leave it in any unit of meters you want, lol
- Fri Oct 18, 2019 9:02 am
- Forum: Properties of Light
- Topic: How does light have momentum but we assume it has no mass?
- Replies: 4
- Views: 202
Re: How does light have momentum but we assume it has no mass?
Light has no resting mass, but electrons do. That's why de Broglies equation can be used for electrons, and it is also why electrons don't move at the speed of light
- Fri Oct 18, 2019 8:57 am
- Forum: SI Units, Unit Conversions
- Topic: Calculate using kg or g?
- Replies: 13
- Views: 898
Re: Calculate using kg or g?
I think different equations are in terms of kg, while some you can use grams. For molar mass, obviously use grams
- Wed Oct 09, 2019 7:45 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Finding Wavelength of Light
- Replies: 3
- Views: 157
Re: Finding Wavelength of Light
In lecture Prof Lavelle urges not to use the Rydberg equation if it confuses you but instead to use the H-atom spectrum equation, which is E(n)= -hR/n^2. you do that for both energy states, n=2 and n=1, and then subtract the initial energy from the final energy to get the change in energy. you can t...
- Wed Oct 09, 2019 7:39 pm
- Forum: DeBroglie Equation
- Topic: Momentum
- Replies: 4
- Views: 136
Re: Momentum
As the person above said, a smaller particle with tiny masses will actually lead to a larger wavelength detected, because of their negligible mass. This is why large objects that have velocity, such as cars, do not act like waves, because their large masses lead to undetectably small wavelengths acc...
- Wed Oct 09, 2019 7:37 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Photon Absorption/Emission
- Replies: 8
- Views: 434
Re: Photon Absorption/Emission
The photon will be absorbed, exciting the electron to a higher energy state, and then as the electron drops back down to the ground state the photon will be emitted again. The photon will have the same amount of energy as it is absorbed and as it leaves because of the law of conservation of energy
- Wed Oct 09, 2019 7:33 pm
- Forum: Properties of Light
- Topic: Formulas
- Replies: 2
- Views: 130
Re: Formulas
They are essentially the same equation. The Rydberg equation is simply derived from using the H-atom equation twice, with the final and initial n values. You can use either and get the same answer, however Prof Lavelle suggested using the H-atom equation because it is easier to understand than tryin...
- Wed Oct 09, 2019 7:29 pm
- Forum: Photoelectric Effect
- Topic: Work Function
- Replies: 3
- Views: 285
Re: Work Function
The work function is the energy needed to remove an electron from the surface of a metal. There is an equation that in words goes like this "E(photon)-E(energy needed to remove e-)=kinetic energy of e-). So the work function is needed to solve for the kinetic energy of an electron, or excess en...
- Thu Oct 03, 2019 11:10 am
- Forum: Molarity, Solutions, Dilutions
- Topic: Fundamentals of chem: Dilution G9
- Replies: 5
- Views: 3695
Re: Fundamentals of chem: Dilution G9
This problem confuses me too, why wouldn't you use the equation M1V1=M2V2? Is it because you are trying to find the mass?
- Thu Oct 03, 2019 11:06 am
- Forum: SI Units, Unit Conversions
- Topic: SI units for exam
- Replies: 6
- Views: 351
Re: SI units for exam
To elaborate on the above comment, usually you round sig figs to the least amount of sig figs given in the problem. This is to make the answer as accurate as possible.
- Thu Oct 03, 2019 10:55 am
- Forum: Balancing Chemical Reactions
- Topic: States of Matter in a Chemical Equation [ENDORSED]
- Replies: 11
- Views: 917
Re: States of Matter in a Chemical Equation [ENDORSED]
What is the purpose of having the states of matter in the chemical equation? What does it imply? Does it only matter in a lab/experiment setting?