Search found 101 matches
- Sun Mar 14, 2021 12:02 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Order of Reactants
- Replies: 6
- Views: 365
Re: Order of Reactants
If you are given elementary steps, then the orders are determined by the coefficients. However, if you are not given elementary steps, then you need to find the experimentally determined rate law from a table of values. This table of values includes concentrations of reactants and the specific rate ...
- Sun Mar 14, 2021 12:00 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Effect of catalyst
- Replies: 22
- Views: 2100
Re: Effect of catalyst
Catalysts only affect the activation energy barrier (the hump). They lower the activation energy barrier so that the reaction can occur at a faster rate. In doing so, rate constants increase in value. Thus, it does not affect the enthalpy difference between reactants and products.
- Sun Mar 14, 2021 11:58 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Which R to use
- Replies: 42
- Views: 2798
Re: Which R to use
It helps to look at the units. 0.0821 has units of L atm/mol K while 8.314 has units of J/mol K. I hope this helps!
- Sun Mar 14, 2021 11:57 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Determining The Favored Side of an Equilibrium Product
- Replies: 12
- Views: 1064
Re: Determining The Favored Side of an Equilibrium Product
If Q is less than K, then that means that there are more reactants. If there are more reactants, then the reaction will want to proceed in the forward direction to make more products. Thus, product formation is favored. If Q is greater than K, then that means that there are more products. If there a...
- Sun Mar 14, 2021 11:55 am
- Forum: Environment, Ozone, CFCs
- Topic: catalysis vs intermediate
- Replies: 25
- Views: 1851
Re: catalysis vs intermediate
Functionally, catalysts lower the activation energy barrier of a reaction and thus, increase the rate constant and the reaction rate. Catalysts are consumed and then produced in reactions so, overall, they are not consumed in reactions (they appear at the beginning and at the end). Intermediates, on...
- Sat Mar 06, 2021 12:47 pm
- Forum: Second Order Reactions
- Topic: Finding out order
- Replies: 22
- Views: 902
Re: Finding out order
Yes, units are definitely a good way to determine order! The units of the rate constant will always ensure that, when multiplied by the according concentration units, the overall (rate) units are M/s or mol/Ls.
- Sat Mar 06, 2021 12:45 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Adding Pt(s)
- Replies: 12
- Views: 610
Re: Adding Pt(s)
If there is no solid electrode in the overall chemical reaction, then you add Pt(s). You do not need to add it to both sides, however, if either the cathode or the anode half reaction contains a solid.
- Sat Mar 06, 2021 11:12 am
- Forum: General Rate Laws
- Topic: Factors Affecting k
- Replies: 83
- Views: 4449
Re: Factors Affecting k
Temperature is the only thing that influences k. When you increase temperature, the rate constant increases (as consistent with the Arrhenius Equation) and the reaction proceeds much more quickly.
- Sat Mar 06, 2021 11:10 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Order of reaction
- Replies: 16
- Views: 1061
Re: Order of reaction
The reaction order essentially specifies the relationship between reaction rate and reactant/product concentration. In this way, we can see the effect that each reactant has on the reaction rate.
- Sat Mar 06, 2021 11:08 am
- Forum: Balancing Redox Reactions
- Topic: How to Determine if a Reaction is in Basic or Acidic Solution?
- Replies: 53
- Views: 2765
Re: How to Determine if a Reaction is in Basic or Acidic Solution?
The problem will specify whether or not the reaction occurs in acidic or basic solution. When it comes to identifying, too, you can always tell if a reaction is in acidic solution if there are H+ ions in the overall reaction and if a reaction is in basic solution if there are OH- ions in the overall...
- Sat Feb 27, 2021 11:43 am
- Forum: Balancing Redox Reactions
- Topic: Acidic vs. Basic
- Replies: 20
- Views: 704
Re: Acidic vs. Basic
When balancing in an acidic solution, your final balanced reaction will include H+. On the other hand, when balancing in a basic solution, your final balanced reaction will include OH-. I hope this helps!
- Sat Feb 27, 2021 11:42 am
- Forum: Balancing Redox Reactions
- Topic: Adding OH-
- Replies: 5
- Views: 333
Re: Adding OH-
You add OH- if the problem specifies that the reaction is occurring in a basic solution. The way I like to do this is to balance the half reactions as if they were in acidic conditions first. Then, I add the same number of moles of OH- to both sides as there are of H+. Finally, I add up the half rea...
- Sat Feb 27, 2021 11:41 am
- Forum: Balancing Redox Reactions
- Topic: Determining which molecule is the oxidizing agent
- Replies: 49
- Views: 1721
Re: Determining which molecule is the oxidizing agent
The oxidizing agent is the molecule that it itself is being reduced so that another molecule can be oxidized. I hope this helps!
- Sat Feb 27, 2021 11:38 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Gibbs Free Energy Equation and n
- Replies: 13
- Views: 554
Re: Gibbs Free Energy Equation and n
n is actually the number of moles of electrons that are being transferred in the reaction! You get this value when you separate a reaction into half reactions and effectively balance them. Then, you multiply the electrons in both half reactions by the least common multiple to get the total number of...
- Sat Feb 27, 2021 11:36 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electron Flow in Electrolytic Cells
- Replies: 1
- Views: 136
Re: Electron Flow in Electrolytic Cells
The anode is positively charged because electrons flow away from the anode, through the battery, and toward the cathode. This is why oxidation (loss of electrons) occurs at the anode and reduction (gain of electrons) occurs at the cathode. I hope this helps!
- Sat Feb 20, 2021 6:28 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta H and Delta S both positive
- Replies: 31
- Views: 7818
Re: Delta H and Delta S both positive
When delta H is a positive valuable, that is unfavorable. Exothermic reactions with negative delta H values are favorable. However, when delta S is a positive value, that is favorable because it indicates an increase in entropy. So, when there is both a positive delta H and a positive delta S, the r...
- Sat Feb 20, 2021 6:27 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: anode and cathode L/R
- Replies: 14
- Views: 579
Re: anode and cathode L/R
For now, assume that this is the case: anode is always on the left, and cathode is always on the right. Also, make sure to remember that the anode is being oxidized (losing electrons) and the cathode is being reduced (gaining electrons). This information should also help you with diagrams and such!
- Sat Feb 20, 2021 6:26 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Adiabatic
- Replies: 26
- Views: 1035
Re: Adiabatic
You are correct! Adiabatic essentially means that there is no heat transfer/flow. Because there is no heat transfer, q (heat) is effectively 0, and the change in internal energy is equal to the amount of work only. I hope this helps!
- Sat Feb 20, 2021 6:24 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: entropy positive value
- Replies: 30
- Views: 1678
Re: entropy positive value
As the second law of thermodynamics states, the entropy of the universe is always increasing and, thus, positive. In addition, a positive entropy (for a system) indicates a spontaneous reaction. I hope this helps!
- Sat Feb 20, 2021 6:23 pm
- Forum: Balancing Redox Reactions
- Topic: Salt Bridges
- Replies: 21
- Views: 749
Re: Salt Bridges
Salt bridges ensure that solutions remain neutral. When electrons are transferred from the anode to the cathode, the salt anion is transferred through the salt bridge to the anode solution in order to remove negative charge from the cathode solution and add negative charge to the anode solution. I h...
- Sat Feb 13, 2021 1:17 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Entropy
- Replies: 27
- Views: 1000
Re: Entropy
Entropy is the measure of disorder. When temperature increases, entropy tends to increase because the molecules have more kinetic energy and, consequently, more movement. When temperature decrease, entropy tends to decrease because the molecules have less kinetic energy and, as a result, less moveme...
- Sat Feb 13, 2021 1:16 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermal Reactions
- Replies: 26
- Views: 1141
Re: Isothermal Reactions
Reversible pathways are usually isothermal. This is because, in irreversible pathways that occur very quickly against a constant external pressure, the temperature drops rather dramatically. However, because reversible pathways occur much more slowly and the pressure is not constant, the heat energy...
- Sat Feb 13, 2021 1:13 pm
- Forum: Calculating Work of Expansion
- Topic: Work
- Replies: 6
- Views: 340
Re: Work
Work done along an irreversible pathway proceeds rather quickly, as pressure is constant/unchanging. However, work done along a reversible pathway is a much slower process because it occurs in a series of steps and the pressure is not constant (it fluctuates/is changing). I hope this helps!
- Sat Feb 13, 2021 1:11 pm
- Forum: Calculating Work of Expansion
- Topic: Positive vs. Negative Work
- Replies: 22
- Views: 811
Re: Positive vs. Negative Work
Positive work implies that work is being done ON the system, while negative work implies that work is being done BY the system on the surroundings. I hope this helps!
- Sat Feb 13, 2021 1:10 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible vs Irreversible
- Replies: 6
- Views: 354
Re: Reversible vs Irreversible
Expansion is characteristically irreversible when the external pressure is constant. This is why, for irreversible reactions, we use the equation -P(deltaV) when calculating work. For reversible reactions, pressure is characteristically fluctuating and has the potential to change and then return to ...
- Sat Feb 06, 2021 12:36 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible Expansion
- Replies: 7
- Views: 259
Re: Reversible Expansion
When a gas expands against a constant pressure, the expansion is deemed irreversible and you would need to use the work equation w = -P(deltaV).
- Sat Feb 06, 2021 12:30 pm
- Forum: Calculating Work of Expansion
- Topic: Spontaneous
- Replies: 26
- Views: 1372
Re: Spontaneous
Spontaneous reactions are favorable reactions in that they can effectively proceed on their own, without any input of energy. The spontaneity of a reaction is determined by its change in heat (delta H) and by its change in entropy (delta S). For instance, when entropy is high, it is likely that the ...
- Sat Feb 06, 2021 12:26 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Ideal Gas Expansion
- Replies: 7
- Views: 149
Re: Ideal Gas Expansion
The internal energy net change is essentially zero because any energy that is lost when the system does expansion work is effectively replaced by an equal input of heat.
- Fri Feb 05, 2021 2:49 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Constant pressure/ volume
- Replies: 11
- Views: 377
Re: Constant pressure/ volume
Constant pressure does not mean that volume is constant, and vice versa. For example, if pressure (or the number of moles of gas) in a container is a high value, then the volume has to change in order to keep the pressure "constant." When there is high pressure, the volume of the container...
- Fri Feb 05, 2021 2:42 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Work
- Replies: 39
- Views: 1356
Re: Work
Negative work means that the system is doing work ON the surroundings or that work is being done BY the system ON the surroundings. When work is negative, the system effectively loses energy (as it is taken up by the surroundings). I hope this helps!
- Sun Jan 31, 2021 5:47 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: 949
Re: Standard Enthalpies of Formation using Hess's Law
Yes, you can definitely rearrange equations. If you reverse/flip an equation, make sure to switch the sign of the enthalpy change. If you multiply an equation by a certain number, make sure to multiply the enthalpy change by that same number.
I hope this helps!
I hope this helps!
- Sun Jan 31, 2021 5:42 pm
- Forum: Phase Changes & Related Calculations
- Topic: Endothermic v. Exothermic
- Replies: 139
- Views: 9245
Re: Endothermic v. Exothermic
Endothermic reactions are characterized by their positive "delta H" values. In endothermic reactions, temperature/heat can be treated as a "reactant." Thus, when temperature is increased, the reaction will shift to the right, and when temperature is decreased, the reaction will s...
- Sun Jan 31, 2021 5:39 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes
- Replies: 18
- Views: 513
Re: Phase Changes
During phase changes, the heat that is supplied goes into breaking bonds. For example, when water transitions from being a liquid to a gas (aka when water vaporizes), a lot of heat is required (more than is required for water to transition from being a solid to a liquid). In summation, heat is requi...
- Sun Jan 31, 2021 5:31 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 58
- Views: 2726
Re: Hess's Law
Hess's law basically says that, even though some reactions may have many stages, the total enthalpy change of the entire reaction is simply a summation of all the individual enthalpy changes of the individual stages. I hope this helps your understanding!
- Sun Jan 31, 2021 5:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: is HClO3 weak or strong? [ENDORSED]
- Replies: 49
- Views: 3857
Re: is HClO3 weak or strong? [ENDORSED]
HCLO3 is a strong acid in our course. It helps to remember this: So I Brought No Clean Clothes.
"So" for H2SO4, "I" for HI, "Brought" for HBr, "No" for HNO3, "Clean" for HCl" and "Clothes" for HClO3 and HClO4.
I hope this helps!
"So" for H2SO4, "I" for HI, "Brought" for HBr, "No" for HNO3, "Clean" for HCl" and "Clothes" for HClO3 and HClO4.
I hope this helps!
- Thu Jan 21, 2021 10:01 am
- Forum: Phase Changes & Related Calculations
- Topic: phase transition
- Replies: 13
- Views: 332
Re: phase transition
Temperature can remain constant because the heat being absorbed isn't going towards heating up the system/surroundings. Rather, the heat is going solely towards breaking the bonds within the system so that a phase change can occur. Bonds must be broken to transform a solid into a liquid and a liquid...
- Thu Jan 21, 2021 9:53 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: When would K be unchanged?
- Replies: 31
- Views: 1004
Re: When would K be unchanged?
If pressure, volume, or even concentration is changed in any way, K will remain constant. Temperature will make it change, however. In an endothermic reaction, if temperature increases, then the reaction shifts towards the products. If temperature decreases, then the reaction shifts towards the reac...
- Tue Jan 19, 2021 9:41 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Ka vs. Kb
- Replies: 30
- Views: 4720
Re: Ka vs. Kb
Ka and Kb are both constants, except Ka is for acids and Kb is for bases. You use Ka when you start with an acid or put an acid into solution, and you use Kb when you start with a base or put a base into solution. It is also important to note that you can find Kb from Ka, and vice versa, using the e...
- Tue Jan 19, 2021 9:39 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: percent ionization
- Replies: 6
- Views: 211
Re: percent ionization
Percent ionization and Ka are different. You calculate percent ionization by dividing the equilibrium concentration of the base/anion produced by the de-protonation of the starting acid by the initial concentration of the starting acid. Then, you multiply this fraction by 100%. It is also interestin...
- Tue Jan 19, 2021 9:37 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Equilibrium Adjustments
- Replies: 10
- Views: 386
Re: Equilibrium Adjustments
Reactions adjust themselves through "shifting" the reaction in favor of the products or reactants. For example, in an endothermic reaction in which temperature can be deemed a "reactant", increasing the temperature will shift the reaction to the right, in favor of the products. I...
- Thu Jan 14, 2021 5:21 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: What is the Conjugate Seesaw
- Replies: 11
- Views: 581
Re: What is the Conjugate Seesaw
The conjugate seesaw works like this: the stronger the acid, the weaker its conjugate base; the weaker the acid, the stronger its conjugate base; the stronger the base, the weaker its conjugate acid; the weaker the base, the stronger its conjugate acid. I hope this helps!
- Thu Jan 14, 2021 5:20 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE table initial conc
- Replies: 3
- Views: 78
Re: ICE table initial conc
If the product concentrations are given/stated in the problem, then you can include them in your ICE table for the initial concentrations! However, a lot of the time, your product concentrations will be 0. A lot of the problems I have seen have given me an initial concentration for the reactant(s) a...
- Thu Jan 14, 2021 5:18 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Solving for equilibrium concentration using Quadratic Equation
- Replies: 5
- Views: 474
Re: Solving for equilibrium concentration using Quadratic Equation
It is very much possible to get 2 positive values for x. To determine which value you should use, you need to look at the initial concentrations you used in the ICE table. For instance, the x value that you will use must be smaller than the initial concentration(s) of the reactant(s) so that your eq...
- Tue Jan 12, 2021 5:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ba(OH)2 example
- Replies: 8
- Views: 801
Re: Ba(OH)2 example
There will likely be several instances where either H3O+ or OH- will be included in the stated reaction and we have to figure out the concentration of the missing component. For example, if H3O+ is given in the reaction, then we may have to solve for the concentration of OH- using the Kw = [H3O+][OH...
- Tue Jan 12, 2021 5:08 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure Rule
- Replies: 29
- Views: 1247
Re: Pressure Rule
In compliance with previous responses, you only have to take into account the moles of gas on either side of the reaction. If there is only a solid on one side, then that side would have 0 moles of gas and thus, fewer moles of gas than the other side.
- Thu Jan 07, 2021 11:00 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Effects of Decreasing Temperature on reactions
- Replies: 4
- Views: 266
Re: Effects of Decreasing Temperature on reactions
It depends on whether the overall reaction is endothermic or exothermic! Increasing temperature for an endothermic reaction tends to accelerate the formation of products and thus favor the forward reaction. For this reason, decreasing temperature for an endothermic reaction will favor the reverse re...
- Thu Jan 07, 2021 10:57 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K for gases
- Replies: 4
- Views: 119
Re: K for gases
Usually the book will specify, whether it gives pressure values or concentration values. If the equation includes gases and ONLY gases, you will most likely format the K expression in terms of pressure. If the equation includes gases and aqueous materials, you will likely format the K expression in ...
- Wed Jan 06, 2021 2:02 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K=1
- Replies: 6
- Views: 153
Re: K=1
K = 1 is rare because that is the point at which the reactants and products are in equilibrium and thus, equally stable. However, in equilibrium, it is not actually likely that the reactants and products are of the same stability, and the rates of the forward and reverse reactions are equal so the r...
- Wed Jan 06, 2021 2:00 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Liquids in Equilibrium Constants
- Replies: 4
- Views: 112
Re: Liquids in Equilibrium Constants
You likely won't ever encounter that in a problem! It is best that we just assume that solvent, H2O, is insignificant. We can assume that H2O is present on both the reactant and product sides of the equation and thus, in the equilibrium constant expression, they will cancel each other out. For this ...
- Tue Jan 05, 2021 1:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: adding chemical equations
- Replies: 2
- Views: 137
Re: adding chemical equations
When adding chemical equations to get an overall equation, you may need to flip/reverse an equation or multiple an equation by a specific coefficient value. When you perform these procedures, you must alter the K value accordingly. When reversing an equation, take the reciprocal of the given K. When...
- Sat Dec 12, 2020 10:23 pm
- Forum: Hybridization
- Topic: Electron Density
- Replies: 6
- Views: 377
Re: Electron Density
When determining the number of hybrid orbitals, you must take into account bonding pairs and lone pairs. For example, NH3 would have sp3 hybridization due to its 3 bonding pairs and 1 lone pair.
- Sat Dec 12, 2020 10:22 pm
- Forum: Air Pollution & Acid Rain
- Topic: Why does acid rain exist
- Replies: 16
- Views: 981
Re: Why does acid rain exist
I agree with everyone, that acid rain exists due to CO2, SO2, and NO2 in the atmosphere forming acids upon reacting with water molecules (i.e. carbonic acid, sulfurous acid, etc.). Oftentimes, these gases result due to the burning of substances. For instance, SO2 is produced by the burning of coal. ...
- Sat Dec 12, 2020 10:19 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate Ligands
- Replies: 5
- Views: 255
Re: Polydentate Ligands
I remember a problem similar to that! It is helpful just to remember them off the top of your head. "en" is bidentate, "dien" is tridentate, and "edta" is hexadentate. Hopefully this is helpful!
- Sat Dec 12, 2020 10:18 pm
- Forum: Hybridization
- Topic: hybrid orbitals
- Replies: 4
- Views: 140
Re: hybrid orbitals
Oftentimes, you will not need to specify the energy level. He will usually just ask for the general "hybridization" of the element, in which case you would put sp2 or sp3, etc. However, there was one textbook problem where we had to specify (i.e. sigma bond: (H1s, C2ps2)), so just be prepa...
- Sat Dec 12, 2020 10:16 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma and Pi Bonds
- Replies: 24
- Views: 991
Re: Sigma and Pi Bonds
Hi Claudia, the only thing I think you are mistaken about is the name of the double bond. Even though double bonds consist of a single pi bond, they are not often referred to as simply a "pi bond." But you are right, make sure to remember that a double consists of a sigma bond AND a pi bond!
- Sun Dec 06, 2020 4:24 pm
- Forum: Conjugate Acids & Bases
- Topic: Conjugate acids vs conjugate base
- Replies: 12
- Views: 750
Re: Conjugate acids vs conjugate base
Basically, the conjugate acid includes the attachment of a proton to the base, and the conjugate base involves the removal of a proton from the acid. In this case, the conjugate base will be SO4^2- and the conjugate acid is H2SO4!
- Sun Dec 06, 2020 4:20 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination Number Question
- Replies: 12
- Views: 624
Re: Coordination Number Question
Coordination number is the number of bonds that the transition metal forms with its ligands (within the coordination sphere). In the example you provided, the coordination number would be 6 because 4 NH3 and 2 Br are attached to a single metal.
Re: Chloride
Cl2 is a molecule of chlorine (gas), formed by the chemical bonding of two chlorine atoms. Cl is just the chlorine ion by itself!
- Sun Dec 06, 2020 4:16 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Oxidation # Question
- Replies: 4
- Views: 308
Re: Oxidation # Question
Oxidation number is the number of electrons that an atom needs to acquire or donate when forming a chemical bond with another atom. For example, an oxygen atom needs to gain 2 electrons (oxidation number --> -2) and a magnesium atom needs to lose 2 electrons (oxidation number --> +2).
- Sat Dec 05, 2020 6:46 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma and Pi Bonds
- Replies: 24
- Views: 991
Re: Sigma and Pi Bonds
You are correct that a single bond is denoted by a sigma bond. However, a double bond is denoted by BOTH a sigma bond and a pi bond; essentially, a double bond cannot just be called a "pi bond" because it contains both types of bonds.
- Sat Nov 28, 2020 5:11 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shape vs Polarity
- Replies: 11
- Views: 568
Re: Shape vs Polarity
You are right! When determining shape, you look at the electron arrangement, which includes both bonding pairs and lone pairs. However, in order to determine polarity, you must consider the overall effect of the lone pairs on the bonding pairs (specifically on their location). Lone pairs occupy a la...
- Sat Nov 28, 2020 5:08 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pair VSEPR
- Replies: 5
- Views: 187
Re: Lone Pair VSEPR
Yes, exactly! Lone pairs are not constrained to bonds, and so they occupy a larger volume overall. This occupation forces the bonding pairs closer to each other and farther away from the lone pair, thus creating a larger bond angle between lone pair and bonding pair and a smaller bond angle between ...
- Sat Nov 28, 2020 5:05 pm
- Forum: Octet Exceptions
- Topic: Question on Radicals
- Replies: 7
- Views: 376
Re: Question on Radicals
Radicals and free radicals are the same. Both are denoted by one unpaired electron.
- Sat Nov 28, 2020 5:03 pm
- Forum: Hybridization
- Topic: sapling #11
- Replies: 11
- Views: 515
Re: sapling #11
Hybridization relies on electron arrangement. The number of electron densities around an atom equals the number of hybrid orbitals. If an atom has 4 regions of electron density, then it will have sp3 hybridization (s, p, p, p). If an atom has 2 regions of electron density, then it will have sp hybri...
- Sat Nov 28, 2020 5:01 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: pi and sigma bonds
- Replies: 17
- Views: 1895
Re: pi and sigma bonds
An easy way to think about sigma bonds is to remember that a SINGLE bond is denoted by a SIGMA bond. If a molecule has multiple bonds, like a double bond or a triple bond, then only one of the bonds will be a sigma bond and the other bonds will be pi bonds. For example, a double bond has one sigma b...
- Sun Nov 22, 2020 11:14 pm
- Forum: Sigma & Pi Bonds
- Topic: Pi Bonds with s Orbital
- Replies: 4
- Views: 166
Re: Pi Bonds with s Orbital
S orbitals do not overlap in the way required to form a pi bond due to their spherical symmetry. P orbitals, however, are able to form pi bonds due to their ability to overlap side-by-side with electron density both above and below the axis.
- Sun Nov 22, 2020 11:10 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Names of different orbitals
- Replies: 7
- Views: 413
Re: Names of different orbitals
Yes, the d and f orbitals have different (specific) configurations just as the p orbital does. However, I do not think it is necessary to memorize the specifics of these orbitals, as they are far more complicated and not entirely of focus in this class.
- Sun Nov 22, 2020 11:07 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 25
- Views: 883
Re: Bond Angles
Yes, I believe that you will have to memorize the bond angles. Most of them are pretty straightforward (180º, 90º, 120º, etc.), and the only difficult one is the bond angle of molecules with tetrahedral shape (109.5º). For molecules where a bonding pair is replaced by a lone pair, just remember that...
- Sun Nov 22, 2020 11:05 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionization Energy
- Replies: 19
- Views: 718
Re: Ionization Energy
For the first ionization energy, the electron is taken from the outermost orbital. The electrons in the outermost orbital are so far removed from the nucleus and its dense positive charge (Zeff) that they require the least amount of energy to remove. This is why the first ionization energy is the sm...
- Sun Nov 22, 2020 11:03 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic and Covalent Bonds
- Replies: 7
- Views: 423
Re: Ionic and Covalent Bonds
You are correct that ionic bonds tend to have a very large electronegativity difference (much larger than that of covalent bonds). This large electronegativity difference causes electrons to be TRANSFERRED rather than SHARED. Additionally, ionic bonds form between a metal and a nonmetal (a cation an...
- Sun Nov 15, 2020 12:19 pm
- Forum: Resonance Structures
- Topic: Resonance
- Replies: 19
- Views: 624
Re: Resonance
In resonance structures, electrons are delocalized, meaning that they can move around within different bonds and they can occupy larger volumes. The most stable structure has the smallest quantity/amount of formal charges.
- Sun Nov 15, 2020 12:15 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Writing Electron Configurations
- Replies: 9
- Views: 797
Re: Writing Electron Configurations
In that electron configuration, the electrons in the 5s orbital have more energy than those in the 4d orbital. In turn, these electrons will be removed first because they are farthest from the nucleus and are more reactive than the electrons in the full, lower energy 4d orbitals.
- Sun Nov 15, 2020 12:10 pm
- Forum: Ionic & Covalent Bonds
- Topic: Electronegativity
- Replies: 18
- Views: 599
Re: Electronegativity
There is usually a table of given values that you can use to calculate the numerical electronegativity difference. However, we will probably not be given a table so just remember that electronegativity increases as you move right across a period and up in a group.
- Sun Nov 15, 2020 12:08 pm
- Forum: Photoelectric Effect
- Topic: Lyman Series
- Replies: 30
- Views: 1085
Re: Lyman Series
In Lyman series, the final principal quantum number/energy level is always n = 1.
- Sun Nov 15, 2020 12:03 pm
- Forum: Lewis Acids & Bases
- Topic: Explanation of Lewis acids & Bases
- Replies: 7
- Views: 3277
Re: Explanation of Lewis acids & Bases
Due to F-'s negative charge, F- is the Lewis base that can donate a pair of electrons to neutral BF3. Thus, BF3 is the Lewis acid because it accepts an electron pair from F- to form BF4-.
- Sun Nov 08, 2020 1:11 pm
- Forum: Properties of Electrons
- Topic: intensity vs energy
- Replies: 29
- Views: 3115
Re: intensity vs energy
The answer is false. Intensity and energy do not have a relationship, and they are therefore not directly proportional to one another. Energy and frequency are related, however.
- Sun Nov 08, 2020 1:08 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Filling orbitals
- Replies: 2
- Views: 44
Re: Filling orbitals
It doesn't necessarily matter which direction you have the arrow pointing, as long as electrons within the same orbital are spinning in opposite directions and electrons in different orbitals are spinning in the same direction when you first start assigning electrons to each orbital.
- Sun Nov 08, 2020 1:06 pm
- Forum: Coordinate Covalent Bonds
- Topic: coordinate covalent bond
- Replies: 7
- Views: 926
Re: coordinate covalent bond
A coordinate covalent bond is formed when a single atom provides BOTH electrons (one full electron pair) in a chemical bond.
- Sun Nov 08, 2020 12:57 pm
- Forum: Resonance Structures
- Topic: Rules for Determining Favored Structure
- Replies: 8
- Views: 510
Re: Rules for Determining Favored Structure
The formal charges should be as close to 0 as possible and the most electronegative atom should have the most negative formal charge. Also the formal charges should be as spread out as possible in the molecule (not all congregated together, on atoms of close proximity, if possible).
- Sun Nov 08, 2020 12:55 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: valence electrons
- Replies: 7
- Views: 342
Re: valence electrons
The number of valence electrons that transition metals have is pretty difficult to determine and slightly randomized. There are a few basic ones that you can probably just memorize if you see them enough in problems! Otherwise, you can just write out the electron configurations to figure it out!
- Sun Nov 08, 2020 12:42 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge Equation
- Replies: 16
- Views: 530
Re: Formal Charge Equation
L is the numerical value of lone pairs of electrons that an atom has. To determine this value, all you need to do is count how many "dots" or electrons the atom has! Be careful not to simply write the number of lone PAIRS; rather, make sure to write the number of ELECTRONS (i.e. not 1 lone...
- Sat Oct 31, 2020 12:10 pm
- Forum: Balancing Chemical Reactions
- Topic: Molar Mass
- Replies: 23
- Views: 1781
Re: Molar Mass
I don't believe that there are a specific number of significant figures that you should always use, but I find it better to use the molar masses specified on the periodic table to ensure that I yield the most accurate results always.
- Sat Oct 31, 2020 12:02 pm
- Forum: Trends in The Periodic Table
- Topic: Ionization energy
- Replies: 4
- Views: 341
Re: Ionization energy
Oxygen has a lower ionization energy than nitrogen and fluorine because, if you look at the electron configuration for oxygen, you will notice that the 2p sub-shell has 4 electrons in it, and so one of the three orbitals in this sub-shell consists of two electrons with opposite spins while the other...
- Sat Oct 31, 2020 11:54 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Atomic and Ionic Radius
- Replies: 6
- Views: 153
Re: Atomic and Ionic Radius
Atomic and ionic radii both follow the same trend. As the number of energy levels increases down a column on the periodic table, the atomic and ionic radii increase because there is a greater distance between the largest energy level and the nucleus.
- Sat Oct 31, 2020 11:50 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Ground State vs. Excited State Question
- Replies: 8
- Views: 1319
Re: Ground State vs. Excited State Question
The ground state configuration displays the lowest energy state that an atom can occupy and often describes an atom in its most stable state. The excited state configuration occurs when one or more of the electrons move to a higher energy state than the one(s) occupied in the ground state configurat...
- Sat Oct 31, 2020 11:45 am
- Forum: Ionic & Covalent Bonds
- Topic: Nonpolar and polar
- Replies: 16
- Views: 1027
Re: Nonpolar and polar
To determine polarity, you need to look at the electro-negativities of the atoms in the molecule. Electronegativity tends to increase from left to right across the periodic table, and from bottom to top of the periodic table. Two atoms with a fairly substantial difference in electronegativity such a...
- Sun Oct 25, 2020 3:48 pm
- Forum: Empirical & Molecular Formulas
- Topic: Dealing with Diatomic Elements
- Replies: 14
- Views: 1220
Re: Dealing with Diatomic Elements
I personally believe that it is easier to treat nitrogen as N when trying to find the empirical formula. It can get a little confusing otherwise.
- Sun Oct 25, 2020 3:45 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg details
- Replies: 3
- Views: 186
Re: Heisenberg details
I was also a little confused about this! In this class, I think it is okay to generalize that speed and velocity are ultimately representative of the same thing. I've been treating them as the same for the past few weeks and have yet to run into any issues! I hope this helps.
- Sun Oct 25, 2020 3:42 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg Equation Confusion
- Replies: 3
- Views: 110
Re: Rydberg Equation Confusion
I was a little confused on this, too! When I was doing the Sapling Weeks 2, 3, and 4 homework problems, however, I noticed that n1 was the final energy level and n2 was the initial energy level.
I hope this helps!
I hope this helps!
- Sun Oct 25, 2020 3:40 pm
- Forum: Properties of Light
- Topic: Wavelength
- Replies: 14
- Views: 511
Re: Wavelength
It depends on whether or not the problem specifies the units. Most of the time, however, your answer will be in meters. For example, in order to find wavelength using the c = (wavelength)(frequency) equation, you must always first convert the wavelength value to meters.
- Sun Oct 25, 2020 3:38 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity and Electronegativity
- Replies: 9
- Views: 394
Re: Electron Affinity and Electronegativity
Electronegativity indicates how well an atom can attract electrons to itself, whereas electron affinity is the quantitative amount of energy released when an electron is gained by an atom. When a more stable element gains an electron, it will absorb energy because the addition of an electron to this...
- Fri Oct 16, 2020 1:57 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Q#39 Atomic Spectra Post Assessment
- Replies: 4
- Views: 151
Re: Q#39 Atomic Spectra Post Assessment
You will use the equation (frequency = - R[(1/n1^2) - (1/n2^2)] where R = 3.29 x 10^15, n1 is the starting energy level (in this case, n = 4), and n2 is the ending energy level (in this case, n = 2). When you get your frequency value, you are not down with the problem yet. You must plug this frequen...
- Fri Oct 16, 2020 1:49 pm
- Forum: Photoelectric Effect
- Topic: How to find the kinetic energy of an electron?
- Replies: 4
- Views: 169
Re: How to find the kinetic energy of an electron?
Often, we will be given the velocity of the electron. From there, all you need to do is plug values into the standard kinetic energy equation (1/2mv^2) where m = mass of electron (9.11 x 10^-31 kg).
- Fri Oct 16, 2020 1:43 pm
- Forum: Properties of Electrons
- Topic: energy levels
- Replies: 4
- Views: 216
Re: energy levels
An electron in an atom can only have certain amounts or quanta of energy. Also, as the energy level (n) and the required amount of energy to move from one energy level to another are inversely proportional. Thus, the largest, quantized difference in energy exists between the first energy level and t...
- Fri Oct 16, 2020 1:37 pm
- Forum: *Black Body Radiation
- Topic: What is Black Body?
- Replies: 53
- Views: 2110
Re: What is Black Body?
A black body is an object that absorbs all EM radiation (any and all frequencies) and, in consequence, produces black-body radiation/black light.
- Wed Oct 14, 2020 8:45 pm
- Forum: Photoelectric Effect
- Topic: Electron not emitted even for high intensity light
- Replies: 9
- Views: 320
Re: Electron not emitted even for high intensity light
Hi! This is based on my understanding... If light exhibited ONLY wave properties, then increasing the intensity (i.e. higher amplitude) should increase the number of electrons emitted. However, light exhibits BOTH wave and particle properties. Thus, if the frequency of light is too low, then increas...
- Sun Oct 11, 2020 1:20 pm
- Forum: Balancing Chemical Reactions
- Topic: Types of Chemical Reactions
- Replies: 8
- Views: 405
Re: Types of Chemical Reactions
It definitely doesn't hurt to know how to identify and work with all the various types of reactions! It'll only help you to have the general ideas/concepts about these reactions and how to work with them in the back of your head as the class becomes more complex.
- Sun Oct 11, 2020 1:18 pm
- Forum: Ionic & Covalent Bonds
- Topic: Physical properties
- Replies: 4
- Views: 668
Re: Physical properties
Ionic bonds are very difficult to break (they require a lot of energy) so, therefore, they have high boiling and melting points. The substances they make up tend to be harder/more brittle too. Covalent bonds are generally less difficult to break so they have lower boiling and melting points. The sub...
- Sat Oct 10, 2020 5:01 pm
- Forum: Photoelectric Effect
- Topic: Threshold Energy vs. Binding Energy
- Replies: 3
- Views: 344
Re: Threshold Energy vs. Binding Energy
I was a little confused about this too, but I realized that threshold energy and binding energy are the same thing! Both indicate the minimum amount of energy needed to expel an electron/particle from a surface.
Hope this helps!
Hope this helps!
- Thu Oct 08, 2020 6:53 pm
- Forum: Balancing Chemical Reactions
- Topic: States of Matter in Chemical Equations
- Replies: 13
- Views: 259
Re: States of Matter in Chemical Equations
Hi! States of matter come into play in later concepts, but I think it is best to get in the habit of writing the states of matter in the chemical equations now. If the states of matter aren't given to you in the problem, then I wouldn't stress too much about it! If they are given, it definitely does...