Search found 108 matches
- Mon Mar 15, 2021 10:45 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts and Intermediates
- Replies: 16
- Views: 900
Re: Catalysts and Intermediates
Think of it as catalysts are tools used to increase the rate, and so will exist before and after the reaction. On the other hand, intermediates are created and consumed in the reaction, so will not exist before and after.
- Mon Mar 15, 2021 10:44 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow Step
- Replies: 14
- Views: 1397
Re: Slow Step
The slowest step of a reaction is the one that determines the rate of the entire reaction. You can identify it by comparing the individual steps' rate laws to the overall rate law.
- Mon Mar 15, 2021 10:42 pm
- Forum: General Rate Laws
- Topic: Intermediate
- Replies: 59
- Views: 3837
Re: Intermediate
Intermediates are substances produced, then consumed in a reaction. Unlike catalysts, they do not exist in the first step's reactants.
- Fri Mar 12, 2021 9:19 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Are catalysts consumed?
- Replies: 37
- Views: 1860
Re: Are catalysts consumed?
Catalysts are not consumed. You may be thinking of intermediates, which are consumed.
- Fri Mar 12, 2021 9:18 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Sapling 20
- Replies: 5
- Views: 337
Re: Sapling 20
Hello, so simply use the Arrhenius equation to find the k-values for each reaction (catalyzed and uncatalyzed), keeping all variables constant except the activation energy. Then divide the k of the catalyzed reaction by the k of the uncatalyzed reaction.
- Fri Mar 12, 2021 9:15 pm
- Forum: Second Order Reactions
- Topic: Determining slow step
- Replies: 22
- Views: 1200
Re: Determining slow step
If the reactants of the slow step are not given, just keep in mind that they will always be a part of the rate law.
- Mon Mar 08, 2021 1:51 am
- Forum: Second Order Reactions
- Topic: Breaking down / explaining 2nd order reactions
- Replies: 7
- Views: 488
Re: Breaking down / explaining 2nd order reactions
Lucy explained it very well above. Simply, it is just a way of describing and categorizing reactions using the order system (0-order means that reaction concentration does not affect rate, 1st order means that the concentration of only one reactant affects the rate, and 2nd order means that two part...
- Mon Mar 08, 2021 1:48 am
- Forum: First Order Reactions
- Topic: Finding order through graphs
- Replies: 17
- Views: 1104
Re: Finding order through graphs
You can plot out experimental values to find the reaction order. Given that A is the reactant and t is time: If the plot of [A] in the y-axis and t in the x-axis is linear, then the reaction is 0-order. If the plot of ln[A] in the y-axis and t in the x-axis is linear, then the reaction is 1st-order....
- Mon Mar 08, 2021 1:43 am
- Forum: Zero Order Reactions
- Topic: Overall order of the reaction
- Replies: 45
- Views: 2007
Re: Overall order of the reaction
Simply sum up the orders of each of the reactants, usually denoted by n, m, etc.
- Mon Mar 08, 2021 1:42 am
- Forum: General Rate Laws
- Topic: Rate determining step
- Replies: 38
- Views: 1563
Re: Rate determining step
Think of the saying "weakest link of a chain"--the slowest step determines the rate because it's the one that is, in a sense, holding back the rest of the reaction.
- Mon Mar 08, 2021 1:41 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: average rate
- Replies: 11
- Views: 644
Re: average rate
In a forward reaction, the average rate will always be negative since the concentration of the reactant(s) decreases as it is converted into products.
- Mon Mar 08, 2021 1:40 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: What was your favorite chem topic?
- Replies: 137
- Views: 11133
Re: What was your favorite chem topic?
Equilibrium was just so satisfying to me once i got it down!
- Sun Feb 28, 2021 10:37 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Shorthand notation
- Replies: 3
- Views: 263
Re: Shorthand notation
It goes (from left to right) anode, ion compound, ion, double line, ion, ion compound, anode.
- Sun Feb 28, 2021 10:35 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anodes and Cathodes
- Replies: 22
- Views: 1039
Re: Anodes and Cathodes
Oxidation takes place at the anode, so the substance will have lower reduction potential.
Reduction takes place at the cathode, so the substance will have higher reduction potential.
Reduction takes place at the cathode, so the substance will have higher reduction potential.
- Sun Feb 28, 2021 10:34 pm
- Forum: Balancing Redox Reactions
- Topic: Finding Reagents From Provided Table
- Replies: 9
- Views: 428
Re: Finding Reagents From Provided Table
Yes, I personally found it helpful to just ctrl+f the particular element in question.
- Sun Feb 28, 2021 10:33 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling Week 7/8 #7
- Replies: 6
- Views: 335
Re: Sapling Week 7/8 #7
I've tried switching up the order of the elements on either side and get different, unhelpful error messages each time, so if someone did this question right, let me know. Hello, this is what I was able to get hope it helps. Thanks so much, this worked! But can anyone explain why this is correct an...
- Sun Feb 28, 2021 10:28 pm
- Forum: Balancing Redox Reactions
- Topic: states of matter
- Replies: 58
- Views: 2429
Re: states of matter
Yes, for some questions (I don't particularly remember how many exactly), the state of matter is required.
- Sun Feb 21, 2021 10:40 pm
- Forum: Calculating Work of Expansion
- Topic: adiabatic processes
- Replies: 18
- Views: 974
Re: adiabatic processes
No. Adiabatic processes have no heat transfer, so q=0 and delta U=w. Since w is the energy transferred through work rather than heat, w is not affected by whether or not a process is adiabatic.
- Sun Feb 21, 2021 10:38 pm
- Forum: Van't Hoff Equation
- Topic: Equation Sheet
- Replies: 7
- Views: 584
Re: Equation Sheet
You can use either, they just have the negative sign in different places.
- Sun Feb 21, 2021 10:36 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G and G naught
- Replies: 46
- Views: 4632
Re: Delta G and G naught
Delta G naught is simply Delta G under standard conditions (273 K / 0˚C, 1 atm).
- Sun Feb 21, 2021 10:33 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Forward vs. Reverse
- Replies: 22
- Views: 2158
Re: Forward vs. Reverse
A reaction moves forward from left to right (as given to you). Since the reactants are on the left and the products are on the right, a forward reaction is R —> P. Thus, the reverse of the same reaction moves from right to left, or P —> R.
- Sun Feb 21, 2021 10:31 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Meaning of K
- Replies: 55
- Views: 3964
Re: Meaning of K
In this context, K is always the equilibrium constant.
- Sun Feb 14, 2021 9:56 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Change in entropy
- Replies: 6
- Views: 492
Re: Change in entropy
You can use the equation delta S = deltaH/T, where delta S is taken from the surroundings and delta H is taken from the system.
- Sun Feb 14, 2021 9:54 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: qrev vs q
- Replies: 21
- Views: 2016
Re: qrev vs q
There isn't really a notable difference, just that qrev is used to specify that the heat value is taken from a reversible system.
- Sun Feb 14, 2021 9:53 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Reversible vs Irreversible Work
- Replies: 5
- Views: 259
Re: Reversible vs Irreversible Work
Reversible work is much slower, more efficient, and takes an infinite number of infinitely small steps. On the contrary, irreversible work is done rapidly and/or in large jumps one direction or another.
W = -Pex delta V is used for irreversible work, and W = -nRTln(V2/V1) is used for reversible work.
W = -Pex delta V is used for irreversible work, and W = -nRTln(V2/V1) is used for reversible work.
- Sun Feb 14, 2021 9:50 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: molar heat capacity
- Replies: 9
- Views: 498
Re: molar heat capacity
Molar heat capacity is defined as the amount of energy needed to raise 1 mol of a certain substance by 1 degree Celsius. Enthalpy, on the other hand, is applied to chemical reactions/phase changes. It is defined as the amount of energy absorbed or released as a process takes place. Molar heat capaci...
- Sun Feb 14, 2021 9:46 pm
- Forum: Calculating Work of Expansion
- Topic: U, q, w
- Replies: 11
- Views: 863
Re: U, q, w
delta U = q + w. You can substitute 0 for q if the system does no work, such as if it is isothermal. Thus, you can also substitute 0 for w if no work is being done, such as if there is no external pressure or no change in volume.
- Sun Feb 14, 2021 9:40 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Useful Summary of Thermodynamic Definitions
- Replies: 55
- Views: 18587
Re: Useful Summary of Thermodynamic Definitions
Thank you so much!
- Sun Feb 07, 2021 9:39 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity of Calorimeter
- Replies: 7
- Views: 1002
Re: Heat Capacity of Calorimeter
I was just wondering, how we are supposed to know if something is a an atom, linear molecule, or nonlinear molecule, like those pertaining to question 20 on the sapling assignment, that were used to fid the heat capacity? For that specific problem, the molecule name was given to you (ex: H2). You c...
- Sun Feb 07, 2021 9:35 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: q and internal energy
- Replies: 8
- Views: 387
Re: q and internal energy
The standard equation for internal energy is deltaU = q + w. Since w = -PdeltaV, w will be 0 when deltaV is 0. In other words, deltaU=q when the volume is constant.
- Sun Feb 07, 2021 9:32 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling #10 Week 3/4
- Replies: 6
- Views: 255
Re: Sapling #10 Week 3/4
Since the ice is already at 0 degrees celsius, it doesn't need to change temperature to undergo a phase change. Thus, we only use the enthalpy of fusion to account for the shift from solid to liquid, and then use the heat capacity of water afterwards to account for changes in temperature after the p...
- Sun Feb 07, 2021 9:27 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Can heat capacities be negative?
- Replies: 52
- Views: 13993
Re: Can heat capacities be negative?
No, because by definition the heat capacity is the amount of heat required to raise the temperature of a substance by 1 degree. Since you cannot increase temperature by taking away heat, heat capacity will always be positive.
- Sun Feb 07, 2021 9:24 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calorimeters
- Replies: 10
- Views: 453
Re: Calorimeters
Calorimeters are simply used to calculate the transfer of heat in a reaction, whether it moves in or out of the system.
- Sun Jan 31, 2021 9:44 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpies of Formation using Hess's Law
- Replies: 18
- Views: 1122
Re: Standard Enthalpies of Formation using Hess's Law
You can flip and rearrange the reactions used, just make sure that you keep track of which direction that they end up in so that you use the correct sign for the enthalpy when calculating.
- Sun Jan 31, 2021 9:41 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 58
- Views: 3092
Re: Hess's Law
Hess's Law states that enthalpy is a state function, meaning that it doesn't take into consideration how the enthalpy arrived at its current value. Thus, enthalpies are additive, making it very straightforward for us to problem solve with them.
- Sun Jan 31, 2021 9:38 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Sapling Week 3/4 #6
- Replies: 14
- Views: 577
Re: Sapling Week 3/4 #6
Since this reaction is a textbook example of a combustion reaction, we can immediately single that out as the most likely answer. If we look at the other possibilities, the bond enthalpies don't line up (as described above). Thus, the enthalpy is equal to the combustion of CH4.
- Sun Jan 31, 2021 9:33 pm
- Forum: Phase Changes & Related Calculations
- Topic: standard form
- Replies: 14
- Views: 769
Re: standard form
Pretty sure we don't have to memorize every standard state besides the diatomic molecules as mentioned above (H2, N2, F2, etc.)
- Sun Jan 31, 2021 9:32 pm
- Forum: Phase Changes & Related Calculations
- Topic: Define Phase Change
- Replies: 78
- Views: 5414
Re: Define Phase Change
A phase change is whenever a substance changes its state of matter (solid, liquid, or gas).
- Sun Jan 24, 2021 9:11 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Week 2 Sapling 5
- Replies: 5
- Views: 241
Re: Week 2 Sapling 5
I was running into the same issue as you; turns out that I simply wasn't using the right value for B[initial]. Keep in mind that B[initial]=[B] + [x], and you should get an appropriate percentage.
- Sun Jan 24, 2021 9:08 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: H2O as a Gas
- Replies: 69
- Views: 6666
Re: H2O as a Gas
If it is a gas, then we include it. If it is in liquid form (as is in most chemical equations dealt with so far), then we exclude it.
- Sun Jan 24, 2021 9:07 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Justin Sarquiz Step-Up Question
- Replies: 9
- Views: 628
Re: Justin Sarquiz Step-Up Question
You can start solving this problem by writing out the chemical equation with the appropriate conjugate acids and bases. In this case, the K+ ions are spectator ions, so you can exclude them from your solving process. Then, set up an ICE box to solve.
- Sun Jan 24, 2021 9:04 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Approximately x
- Replies: 18
- Views: 698
Re: Approximately x
According to Dr. Lavelle, we can use this approximation when the K-value is smaller than 10^-4.
- Sun Jan 24, 2021 9:02 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Kelvin or Celsius?
- Replies: 86
- Views: 5702
Re: Kelvin or Celsius?
Default to Kelvin here.
- Sun Jan 17, 2021 3:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ice Box Method
- Replies: 14
- Views: 518
Re: Ice Box Method
Since we can choose to use + or - x for each of the compounds in a reaction, we simply have to determine which direction the reaction will shift with the given change. If it will shift to the right, we use -x for the reactants and +x for the products, and vice versa.
- Sun Jan 17, 2021 3:28 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 1 #5
- Replies: 6
- Views: 193
Re: Sapling Week 1 #5
For this question, I found it helpful to write out the expressions for each chemical equation's K value (using the brackets and such). Then, you can see that you can get the desired K value by multiplying the K of the reciprocal of equation 1 by equation 3.
- Sun Jan 17, 2021 3:26 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Approximations
- Replies: 4
- Views: 231
Re: Approximations
Since any value to 10^-4 is extremely small, it is deemed "close enough" to zero to treat it as zero in your calculations.
- Sun Jan 17, 2021 3:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Chart with Gas Pressures
- Replies: 8
- Views: 329
Re: ICE Chart with Gas Pressures
Yep; they are completely interchangeable in this coursel; just remember to keep the units of measurement consistent throughout the problem.
- Sun Jan 17, 2021 3:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: shifts left or right
- Replies: 23
- Views: 1162
Re: shifts left or right
If a reaction is shifting to the left, then it will begin to produce more reactants relative to products. If it is shifting to the right, then it will produce more products relative to reactants.
- Mon Jan 11, 2021 12:00 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 9
- Views: 577
Re: Le Chatelier's Principle
It outlines how reactions adjust to changes in concentration, pressure, and temperature.
- Mon Jan 11, 2021 12:00 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Increasing Pressure by Adding an Inert Gas
- Replies: 6
- Views: 877
Re: Increasing Pressure by Adding an Inert Gas
Since inert gases don't react with anything, all the concentrations will remain proportional.
- Sun Jan 10, 2021 11:59 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Changing pressure by adding gas
- Replies: 13
- Views: 357
Re: Changing pressure by adding gas
Yes, as adding an inert gas will not change the reaction. Only by changing individual concentrations will the reaction be affected.
- Sun Jan 10, 2021 11:58 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 7
- Views: 318
Re: Le Chatelier's Principle
The principle specifies how reactions will naturally balance themselves out from changes, meeting the same k value.
- Sun Jan 10, 2021 11:57 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: adding heat
- Replies: 15
- Views: 568
Re: adding heat
Since endothermic reactions require heat to occur, increasing temperature will aid in meeting the activation energy.
- Sun Dec 13, 2020 1:18 pm
- Forum: Bond Lengths & Energies
- Topic: hydrogen bonding vs ion-dipole
- Replies: 5
- Views: 2757
Re: hydrogen bonding vs ion-dipole
Ion-dipole forces are stronger than hydrogen bonds, as hydrogen bonds are simply a strong type of dipole-dipole forces. Since ion-dipole forces are always stronger than dipole-dipole, ion-dipole forces are stronger than hydrogen bonds.
- Sun Dec 13, 2020 1:16 pm
- Forum: Bond Lengths & Energies
- Topic: Higher Melting Point
- Replies: 28
- Views: 2652
Re: Higher Melting Point
Since Iodine is a larger molecule than Fluorine, the bond is stronger due to it being easier to distort its electrons. Thus, the compound with iodine is harder to break, resulting in a higher melting point.
- Sun Dec 13, 2020 1:15 pm
- Forum: Lewis Structures
- Topic: Octet rule
- Replies: 12
- Views: 721
Re: Octet rule
Think of it as the third row p-block elements can have expanded octets, and B, Be, Li, He, and H can have less than an octet.
- Sun Dec 13, 2020 1:13 pm
- Forum: Lewis Structures
- Topic: Lewis Acids and Bases
- Replies: 3
- Views: 269
Re: Lewis Acids and Bases
Writing out the lewis structure would help here. In this compound, boron has only three bonds and no lone pairs, so can easily accept electrons from a lewis acid.
- Sun Dec 13, 2020 1:11 pm
- Forum: Ionic & Covalent Bonds
- Topic: Polar Bonds [ENDORSED]
- Replies: 26
- Views: 1327
Re: Polar Bonds [ENDORSED]
You look at the geometry and the differences in electronegativity. If there are clear differences that do not cancel out, then the bond is polar.
- Sun Dec 13, 2020 1:09 pm
- Forum: Ionic & Covalent Bonds
- Topic: Covalent Character
- Replies: 33
- Views: 1607
Re: Covalent Character
The less difference in electronegativity (look at position on periodic table), the more covalent it is.
- Sun Dec 06, 2020 10:54 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Question about Shape
- Replies: 5
- Views: 444
Re: Question about Shape
Yep, both are angular. Keep in mind that the angles are slightly less than those for a typical trigonal planar and tetrahedral structure, as lone pairs "push" other regions of electron density more than bonds. Thus, the observed bonds are more squished together.
- Sun Dec 06, 2020 10:51 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond angle
- Replies: 4
- Views: 256
Re: Bond angle
The central atom is bound to two atoms and has two lone pairs, thus holding 4 regions of electron density. This forms a tetrahedral-esque structure, which has a 109.5 degree bond angle.
- Sun Dec 06, 2020 10:48 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Structure Names
- Replies: 5
- Views: 206
Re: Structure Names
Octahedral structures are formed when 6 bonds orient regularly around a central atom, forming a structure with 8 faces (thus lending the name "octahedron"). I think of bipyramidal structures as two pyramids sharing a base, forming a shape similar to the green thing from Sims.
- Sun Dec 06, 2020 10:45 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polarity
- Replies: 7
- Views: 284
Re: Polarity
Yes; once you determine the shape of the molecule, you can see if the dipole moments cancel each other out geometrically. If so, then the molecule is nonpolar.
- Sun Dec 06, 2020 10:44 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: polar v nonpolar molecules
- Replies: 30
- Views: 2498
Re: polar v nonpolar molecules
First, you gotta determine the differences in electronegativity between the individual atoms. If none exist or if they cancel each other out, then the molecule is nonpolar. If there is a noticeable direction of electronegativity difference, then the molecule is polar.
- Sun Nov 29, 2020 10:15 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma and Pi Bonds
- Replies: 24
- Views: 1255
Re: Sigma and Pi Bonds
I'm not completely sure if double bonds are commonly referred to as pi bonds, but they include one sigma and one pi bond. Thus, it is distinct from a normal pi bond (ie single bond).
- Sun Nov 29, 2020 10:13 pm
- Forum: Ionic & Covalent Bonds
- Topic: More Covalent
- Replies: 8
- Views: 566
Re: More Covalent
You can either look at the number of bonds formed (more bonds=more covalent) or the bond length (shorter=more covalent).
- Sun Nov 29, 2020 10:12 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic radius
- Replies: 18
- Views: 905
Re: Ionic radius
More electrons = larger radius and vice versa, as adding additional electrons will increase their repulsion from the nuclei.
- Sun Nov 29, 2020 10:10 pm
- Forum: Ionic & Covalent Bonds
- Topic: Homework due date
- Replies: 49
- Views: 2286
Re: Homework due date
Sunday night at 12 am.
- Sun Nov 29, 2020 10:10 pm
- Forum: Sigma & Pi Bonds
- Topic: Sapling Q #16
- Replies: 14
- Views: 918
Re: Sapling Q #16
Delocalized simply means that there exist resonance structures for the compound, so the pi bond(s) can exist in multiple different positions.
- Sun Nov 22, 2020 9:06 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bond Angle
- Replies: 8
- Views: 585
Re: Bond Angle
There is no need to memorize specific bond angles for different compounds. However, bond angles can be calculated and/or estimated by playing around with the fact that a circle has an angle of 360 degrees. For example, you can deduce that a trigonal planar molecule has bond angles of about 360/3=120...
- Sun Nov 22, 2020 9:03 pm
- Forum: Ionic & Covalent Bonds
- Topic: Molecule size and ionic character
- Replies: 13
- Views: 1451
Re: Molecule size and ionic character
Although molecule size is often correlated with its ionic character, a better way to determine ionic character is by looking at the difference in electronegativity between the bonded elements. The greater the difference, the stronger ionic character the molecule exhibits.
- Sun Nov 22, 2020 9:01 pm
- Forum: Ionic & Covalent Bonds
- Topic: Covalent Character
- Replies: 14
- Views: 2409
Re: Covalent Character
You simply look at the difference in electronegativity between the bonded elements. For example, a molecule with carbon and hydrogen is extremely covalent because they are very similar in electronegativity.
- Sun Nov 22, 2020 8:59 pm
- Forum: Ionic & Covalent Bonds
- Topic: Polar/ Nonpolar
- Replies: 25
- Views: 1325
Re: Polar/ Nonpolar
Shape can be used to determine if a molecule is polar or nonpolar, but you must consider whether or not it has existing dipole moments. If dipole moments are not present or if they cancel each other out (with respect to shape), then it is nonpolar. If they exist and do not cancel out, then it is pol...
- Sun Nov 22, 2020 8:57 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Lewis acids and bases
- Replies: 22
- Views: 1190
Re: Lewis acids and bases
Generally, you can determine which molecules accept (acids) or donate (bases) by looking at their respective Lewis Structures. Lone pair electrons usually indicate that the molecule is a base.
- Sun Nov 22, 2020 8:55 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Best Formal Charge Equations
- Replies: 24
- Views: 1141
Re: Best Formal Charge Equations
Personally, I take the number of valence electrons (V) and subtract from it the number of bonds (s/2) combined with the number of non-bonding electrons (L).
- Sun Nov 15, 2020 8:26 pm
- Forum: Lewis Structures
- Topic: Sapling Question #4
- Replies: 5
- Views: 353
Re: Sapling Question #4
In general, comparing the given bond lengths to the values on the table provided should give a strong indication of ample or overwhelming characteristics. In other words, on an exam, the difference between the two classifications should be extremely clear, and will allow you to simply make your best...
- Sun Nov 15, 2020 8:24 pm
- Forum: Lewis Structures
- Topic: Sapling Weeks 5/6 HW #18
- Replies: 7
- Views: 391
Re: Sapling Weeks 5/6 HW #18
In the case of dispersion forces, larger molecules have stronger attraction due to the distance between the nuclei and the outer electrons. Since the outer electrons in large atoms are more loosely held compared to smaller atoms, they are more easily affected by external charges.
- Sun Nov 15, 2020 8:21 pm
- Forum: Ionic & Covalent Bonds
- Topic: Hydrogen Bonding
- Replies: 13
- Views: 432
Re: Hydrogen Bonding
When an H atom is bonded to a N, O, or F atom, it causes a notable electronegativity difference due to the strong electronegativity of N, O, and F. Thus, the present partial charges allow for the formation of a hydrogen bond.
- Sun Nov 15, 2020 8:20 pm
- Forum: Ionic & Covalent Bonds
- Topic: Difference on how atomic size affects covalent and dipole interactions
- Replies: 9
- Views: 2085
Re: Difference on how atomic size affects covalent and dipole interactions
Yep, that's exactly right. Just to clarify for dispersion forces, larger atomic radii cause weaker attraction between the outer electrons and the nuclei, thus allowing for easier polarization.
- Sun Nov 15, 2020 8:17 pm
- Forum: Ionic & Covalent Bonds
- Topic: Resonance Structures
- Replies: 5
- Views: 209
Re: Resonance Structures
A way to think about hybrid resonance is by taking the "average" of the known resonance structures for the molecule. All the bonds that differ between the structures are "averaged out" to form the hybrid structure.
- Sun Nov 08, 2020 7:31 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: ml and number of possible electrons
- Replies: 6
- Views: 225
Re: ml and number of possible electrons
You're spot on! Since ms is the variable that specifies the spin of the electrons, there are two possible electron states for each ml value.
- Sun Nov 08, 2020 7:30 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Spin state
- Replies: 25
- Views: 1322
Re: Spin state
As others have already said, it refers to which direction that the electron is spinning on the axis. In short, it's just another level of specificity when it comes to describing electrons/electron behavior.
- Sun Nov 08, 2020 7:29 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Are there subshells past f?
- Replies: 28
- Views: 1166
Re: Are there subshells past f?
Yes, but we don't have to worry about them for this class.
- Sun Nov 08, 2020 7:28 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 4s before 3d Orbital
- Replies: 11
- Views: 544
Re: 4s before 3d Orbital
This is considered an "exception" to the general rule of increasing energy through orbitals, as the 4s is lower energy than 3d. Thus, it is filled first, specifically with d-block elements. However, 3d is still written before 4s when notating electron configuration.
- Sun Nov 08, 2020 7:25 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: S and P electrons
- Replies: 14
- Views: 1558
Re: S and P electrons
Since p-electrons are further away from the nucleus of the atom, they have higher energy, as is required to keep them on the atom.
- Sun Nov 08, 2020 7:24 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbital vs Subshell
- Replies: 7
- Views: 532
Re: Orbital vs Subshell
N specifies which shell is being isolated, l specifies which subshell of that shell, and ml specifies which orbital of that subshell. Thus m, l, and ml are increasing in terms of specificity.
- Sun Nov 01, 2020 7:02 pm
- Forum: Trends in The Periodic Table
- Topic: Hydrogen on the periodic table
- Replies: 3
- Views: 213
Re: Hydrogen on the periodic table
Generally, Hydrogen is placed in group 1 on the Periodic Table. However, it shares some properties with both group 1 and group 17, so some arguments can be made on its classification. But overall, it's just a unique element.
- Sun Nov 01, 2020 7:00 pm
- Forum: Trends in The Periodic Table
- Topic: ionic radius
- Replies: 14
- Views: 484
Re: ionic radius
As anions have extra electrons and cations have less electrons than the "normal" state of the element, anions are larger and cations are smaller.
- Sun Nov 01, 2020 6:58 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Simplifying Electron Configurations
- Replies: 9
- Views: 982
Re: Simplifying Electron Configurations
As other people seem to have already answered the first part of your question quite thoroughly, I thought I'd add that by convention, noble gases are the only elements used as shorthand reference elements (due to their convenience both in location on the table and for having a complete outer shell a...
- Sun Nov 01, 2020 6:57 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Configuration For Calcium
- Replies: 7
- Views: 320
Re: Electron Configuration For Calcium
K and Ca are simply exceptions to the rules applied to the previous elements, as 4s is lower energy than 3d. Thus, for these two elements, 4s is written before 3d in order to keep with the convention that configurations are written with ascending energy.
- Sun Nov 01, 2020 6:54 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 4s and 3d
- Replies: 14
- Views: 489
Re: 4s and 3d
The third is written before the fourth simply because it notates a lower n-value (shell). Since these are written in ascending order by convention, 3d will always come before 4s.
- Sun Nov 01, 2020 6:54 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 4s and 3d
- Replies: 14
- Views: 489
Re: 4s and 3d
The third is written before the fourth simply because it notates a lower n-value (shell). Since these are written in ascending order by convention, 3d will always come before 4s.
- Sun Oct 25, 2020 10:17 pm
- Forum: Photoelectric Effect
- Topic: Mass of atoms
- Replies: 18
- Views: 671
Re: Mass of atoms
Other people have pretty much covered it, but just make sure that your SI units align in your equations, and when in doubt double check the conversions.
- Sun Oct 25, 2020 10:15 pm
- Forum: Properties of Electrons
- Topic: Lyman and Balmer series
- Replies: 6
- Views: 297
Re: Lyman and Balmer series
For most problems, you just have to know that the Balmer series covers jumps starting or ending at n=2, and the Lyman series with n=1. Also, the Balmer covers the visible regions of the EM spectrum, and the Lyman covers UV regions. I'm pretty sure you don't need to know the specific frequency limits...
- Sun Oct 25, 2020 10:05 pm
- Forum: Properties of Electrons
- Topic: rydberg equation
- Replies: 8
- Views: 384
Re: rydberg equation
As other people have said, n1 is the lower energy level and n2 is the higher one (in emission equations). Another way to remember it is to make sure that the value of (1/n1^2)-(1/n2^2) is always positive.
- Sun Oct 25, 2020 10:02 pm
- Forum: Properties of Light
- Topic: Speed of light
- Replies: 25
- Views: 836
Re: Speed of light
Though 3.0 will probably be fine in most questions, you can round to math the sig figs of the given values just to be safe.
- Sun Oct 25, 2020 9:04 pm
- Forum: Properties of Light
- Topic: Amplitude
- Replies: 9
- Views: 535
Re: Amplitude
Yes, amplitude is specifically a feature of wave models. However, increasing the amplitude of a light source will not increase its energy - only its intensity. The only way (that's been mentioned in class so far) to change energy is to change frequency.
- Sun Oct 18, 2020 10:33 am
- Forum: Photoelectric Effect
- Topic: Excess energy
- Replies: 20
- Views: 609
Re: Excess energy
This equation is used to find the kinetic energy of the electron, which is essentially the leftover energy after the threshold energy is used up to eject the electron in the first place.
- Sun Oct 18, 2020 10:31 am
- Forum: Photoelectric Effect
- Topic: Question about Short Wavelengths vs. Long Wavelengths
- Replies: 6
- Views: 456
Re: Question about Short Wavelengths vs. Long Wavelengths
Essentially, the wavelength determines whether or not the light will be able to eject electrons, as higher wavelength = higher energy of the photons. Since intensity refers only to the number of photons of light emitted, increasing intensity while not changing wavelength will not affect whether or n...
- Sun Oct 18, 2020 10:27 am
- Forum: Photoelectric Effect
- Topic: Frequency vs. Intensity
- Replies: 16
- Views: 711
Re: Frequency vs. Intensity
The light must meet a certain frequency in order to eject electrons from the material. Since the intensity only refers to the number of photons and not their energy level, increasing the intensity but not the frequency will not affect whether or not electrons are ejected.