Search found 152 matches
- Sat Mar 13, 2021 11:10 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts
- Replies: 6
- Views: 489
Re: Catalysts
Catalysts will not be included in the overall rate law because it is "consumed' in one step and then produced in another.
- Sat Mar 13, 2021 11:03 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Temperature vs. activation energy
- Replies: 33
- Views: 2677
Re: Temperature vs. activation energy
As others have stated above, an increase in temperature increases the rate constant, k. Similarly, a decrease in temperature decreases k.
- Sat Mar 13, 2021 11:01 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: sign for Eo when reversing rxn
- Replies: 11
- Views: 838
Re: sign for Eo when reversing rxn
Yes, if you are reversing the reaction you would flip the sign of Enaught. However, keep in mind that the value of Enaught will not change if you multiply the reaction by a factor.
- Sat Mar 13, 2021 10:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Determining The Favored Side of an Equilibrium Product
- Replies: 12
- Views: 1290
Re: Determining The Favored Side of an Equilibrium Product
If Q < K, the equilibrium will shift to the right and products are favored. If Q > K, the equilibrium will shift to the left and reactants are favored.
- Sat Mar 13, 2021 10:56 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow Step
- Replies: 14
- Views: 1462
Re: Slow Step
The slow step of a mechanism is the rate limiting step; it determines the rate of the overall reaction. You can identify the slow step from a mechanism by determining whether the rate law of that step matches the rate law of the overall reaction.
- Sun Mar 07, 2021 1:33 pm
- Forum: General Rate Laws
- Topic: Sapling 9/10 #5
- Replies: 10
- Views: 2972
Re: Sapling 9/10 #5
If [A] is halved and [B] is tripled, you would multiply the initial rate by (1/2)^1 (because [A] is first order) and 3^2 (because [B] is second-order). --> Rate = (1/2)^1 x 3^2 x 0.0480 M/s Similarly, if [A] is tripled and [B] is halved, you would multiply the initial rate by 3^1 and (1/2)^2. --> Ra...
- Sun Mar 07, 2021 1:22 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Rate Laws and Elementary Steps
- Replies: 4
- Views: 277
Re: Rate Laws and Elementary Steps
Hi! Yes, you are correct! The rate laws for the reactions of elementary steps can be written using the balanced chemical equation and its stoichiometric coefficients. However, as Jaden pointed out, it is important to note that although intermediate species can be written in the rate laws of the elem...
- Sun Mar 07, 2021 1:18 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: graphs and order
- Replies: 19
- Views: 961
Re: graphs and order
The order of the reaction will determine what should be plotted. A first order reaction is a straight line plot of ln[A] vs time. A second order reaction is a straight line plot of 1/[A] vs time. A zeroth order reaction is a straight line plot of [A] vs time. ([A] is the concentration of the reactant)
- Thu Mar 04, 2021 11:51 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Order of Reaction
- Replies: 4
- Views: 265
Re: Order of Reaction
The order of reaction is not based on the stoichiometric coefficients; it is calculated using experimental data. The order of reaction is the sum of the order of each reactant.
- Thu Mar 04, 2021 11:48 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram Commas
- Replies: 9
- Views: 621
Re: Cell Diagram Commas
No, the order does not matter in the cell diagram. You would involve Pt(s) in the cell diagram as an inert conductor to transfer electrons when there are no conducting solids.
- Sun Feb 28, 2021 6:06 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation vs Reduction
- Replies: 30
- Views: 1465
Re: Oxidation vs Reduction
I use the acronym LEO to remember that Oxidation is the Lost of Electrons and the acronym GER to remember that Reduction is the Gaining of Electrons. An oxidation half-reaction is a reaction in which a species is losing electrons. A reduction half-reaction is a reaction in which a species is gaining...
- Thu Feb 25, 2021 11:31 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Oxidation
- Replies: 2
- Views: 176
Re: Oxidation
The reagent that would oxidize Zn to Zn^2+ but not Sn to Sn^2+ would have a higher standard reduction potential than that of Zn to Zn^2+ and a lower standard reduction potential than that of Sn to Sn^2+. In other words, standard reduction potential of Zn to Zn^2+ < standard reduction potential of re...
- Thu Feb 25, 2021 11:21 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Oxidation Agent
- Replies: 12
- Views: 619
Re: Oxidation Agent
The better/best oxidizing agents are the species that are more likely to be reduced. So, the species with the higher/highest reduction potential will be the better/best oxidizing agent.
- Thu Feb 25, 2021 11:18 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 30
- Views: 1495
Re: Salt Bridge
The purpose of the salt bridge is to keep the solutions in the oxidation half-reaction and the reduction half-reaction neutral. The salt bridge prevents charge buildup by allowing anions to enter the anode side and cations to enter the cathode side. This will allow the solutions to stay neutral so t...
- Thu Feb 25, 2021 11:09 am
- Forum: Balancing Redox Reactions
- Topic: E naught
- Replies: 15
- Views: 990
Re: E naught
Since E naught is an intensive property, the value of E naught will not change since it does not depend on how many times the reaction occurred. So, for example, if you multiplied the reaction by a factor of 2, you would not multiply the E naught value by 2; it will remain the same.
- Thu Feb 25, 2021 11:06 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Sapling Weeks 7 and 8 Question 12
- Replies: 4
- Views: 302
Re: Sapling Weeks 7 and 8 Question 12
Hi! The n value is the number of moles of electrons transferred, so your n value would be 6 and not 1. Hope this helps!
- Sun Feb 21, 2021 6:38 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Forward vs. Reverse
- Replies: 22
- Views: 2231
Re: Forward vs. Reverse
If the forward reaction is R (reactants) --> P (products), the reverse reaction would be P --> R.
- Fri Feb 19, 2021 9:38 pm
- Forum: Calculating Work of Expansion
- Topic: Work sign
- Replies: 46
- Views: 2225
Re: Work sign
Work done BY the system (the system does work) is negative. Work done ON the system is positive.
- Fri Feb 19, 2021 9:36 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: When does delta H = q?
- Replies: 15
- Views: 5221
Re: When does delta H = q?
As others have stated above, delta H = q at constant pressure. It is also good to keep in mind that the term "isobaric" refers to conditions of constant pressure.
- Fri Feb 19, 2021 9:31 pm
- Forum: Calculating Work of Expansion
- Topic: Work Formula
- Replies: 15
- Views: 847
Re: Work Formula
As others have stated above, delta n refers to the net change in moles of gases, so you would only consider the moles of gases and ignore the moles of solids and liquids.
- Fri Feb 19, 2021 9:27 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: q and w for an Isolated System
- Replies: 19
- Views: 3506
Re: q and w for an Isolated System
For isolated systems, q = 0 because there is no heat transfer, and w = 0 because there is also no volume change as nothing can go in or out. This means that delta U = 0 as well.
- Fri Feb 19, 2021 9:23 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gas Constant R
- Replies: 43
- Views: 4256
Re: Gas Constant R
The R you would use depends on the units! Use R = 8.314 J/mol.K or R = 0.08206 L.atm/mol.K depending on the units of the other terms.
- Sun Feb 14, 2021 1:58 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Textbook 5J.11
- Replies: 3
- Views: 228
Re: Textbook 5J.11
If the reaction is endothermic, an increase in temperature will shift the equilibrium toward the products. If the reaction is exothermic, an increase in temperature will shift the equilibrium toward the reactants.
- Sun Feb 14, 2021 1:48 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Which R to use
- Replies: 42
- Views: 3242
Re: Which R to use
The R you would use in the equation w = -nRT*ln(V2/V1) is R = 8.314 J/(K*mol) so that the units will cancel out. When you are solving the ideal gas law equation PV=nRT, you would use R = 0.08206 (L*atm/(K*mol)).
- Sun Feb 14, 2021 1:41 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Sign of work
- Replies: 17
- Views: 836
Re: Sign of work
If work is being done BY the system, then work is a negative value. If work is being done ON the system, then work is a positive value. Whenever something, such as the system in this context, is doing work, its value for work will be negative.
- Thu Feb 11, 2021 3:27 am
- Forum: Calculating Work of Expansion
- Topic: Negative vs Positive Work
- Replies: 13
- Views: 827
Re: Negative vs Positive Work
If the system is undergoing compression, work is positive as work is being done on the system. If the system is undergoing expansion, work is negative because work is being done by the system (the system is doing work).
- Thu Feb 11, 2021 3:23 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Kelvin conversion
- Replies: 40
- Views: 3557
Re: Kelvin conversion
You can add 273 or 273.15 to your°C to convert degrees celsius to degrees kelvin. Using 273.15 is slightly more accurate but your answer should not be different if you use 273.
- Thu Feb 11, 2021 3:19 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: sapling 8
- Replies: 5
- Views: 287
Re: sapling 8
To calculate the standard molar entropy of vaporization, there are 3 steps. Step 1 is to heat the water from 40.0 °C to its normal boiling point, (100 °C) by using C*ln(T2/T1). Step 2 is to allow the water to vaporize at the boiling point (100 °C). This value is given in the problem. Step 3 is to co...
- Sat Feb 06, 2021 8:38 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Work
- Replies: 39
- Views: 1747
Re: Work
If the value of work is negative, it means that the system is doing work on the surroundings. If the value of work is positive, it means that work is done on the system, meaning the surroundings are doing work on the system.
- Sat Feb 06, 2021 8:32 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: deltaU
- Replies: 29
- Views: 985
Re: deltaU
Delta U is the change in internal energy of a system, which consists of the heat absorbed/released from a system and the work done by/on the system. The equation to calculate delta U is deltaU = q + w.
- Sat Feb 06, 2021 8:27 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: q=mCdeltaT vs q=CdeltaT
- Replies: 3
- Views: 178
Re: q=mCdeltaT vs q=CdeltaT
q = mCdeltaT is used to calculate the specific heat capacity. q = CdeltaT is used to calculate the heat capacity.
- Wed Feb 03, 2021 10:39 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook 6A.21
- Replies: 4
- Views: 236
Re: Textbook 6A.21
As others have said above, you would assume [H3O+] = [OH-] are equal since the water is neutral, which means that [H3O+] = [OH-] = x. Then, you would plug in x and the given Kw into the equation Kw = [H3O+] x [OH-], which would equal Kw = (x) x (x) = x^2.
- Wed Feb 03, 2021 10:35 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Reversible and Irreversible System
- Replies: 1
- Views: 103
Re: Reversible and Irreversible System
Reversible expansions do more work than irreversible expansions because since the system is at equilibrium, the internal and external pressures are approximately the same, so when the external pressure slowly decreases by a small value such as a millionth, the internal pressure will undergo a small ...
- Sun Jan 31, 2021 9:48 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure affects only gas reactions?
- Replies: 23
- Views: 1941
Re: Pressure affects only gas reactions?
Hi! Changes in pressure (by changing the volume) only affects gases since gases are compressible. If the pressure increases (decreasing the volume), the equilibrium would shift to the side with less amount of moles of gas, but if there are equal moles of gases on both sides of the reaction, the equi...
- Fri Jan 29, 2021 1:30 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Outline Point: Effect of K
- Replies: 5
- Views: 176
Re: Outline Point: Effect of K
Let's say that you are given the reaction: A + B <--> C and the K for this reaction. If you reverse this reaction to C <--> A + B, the K for this reaction would be 1/K. (If you reverse the reaction, you take the inverse of the K). If you multiply the reaction by a coefficient, for example 2A + 2B <-...
- Fri Jan 29, 2021 1:21 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Making X negligible
- Replies: 34
- Views: 1617
Re: Making X negligible
If K < 10^-4 , you can make the assumption that x is a really small value, which means you can use the shortcut of approximation. To be safe, you should confirm whether you can make the approximation by calculating the percent ionization. If (x/initial concentration) x 100 is less than 5%, your appr...
- Fri Jan 29, 2021 1:11 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: How Does Temperature Affect the Equilibrium Constant?
- Replies: 25
- Views: 22934
Re: How Does Temperature Affect the Equilibrium Constant?
Raising the temperature will either increase or decrease K. If the reaction is endothermic, raising the temperature will cause an increase in K. If the reaction is exothermic, raising the temperature will cause a decrease in K.
- Fri Jan 29, 2021 1:06 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Textbook problem 6.61
- Replies: 7
- Views: 313
Re: Textbook problem 6.61
In this problem water is not affecting the equilibrium because it is in its liquid state. Solids and liquids are omitted from the equilibrium constant expression, and hence do not affect the equilibrium, because the change in their concentrations are negligible.
- Wed Jan 27, 2021 10:24 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K greater than 1 or greater than 10^3
- Replies: 4
- Views: 286
Re: K greater than 1 or greater than 10^3
K being greater/less than 10^-3, and K being greater/less than 1 indicates whether the products/reactants are or not strongly strongly favored. If K > 10^3, products are strongly favored. If K < 10^-3, reactants are strongly favored. If K > 1, products are slightly favored. If K < 1, reactants are s...
- Wed Jan 27, 2021 10:17 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Finding Ka from pH
- Replies: 7
- Views: 1000
Re: Finding Ka from pH
Hi! To calculate the Ka from the given pH and concentration, first you would convert the pH to [H3O+]. To do this conversion, you would plug in the pH to this equation: [H3O+] = 10^-pH. Next, I would set up an ice table using the given initial concentration in order to organize the expressions for t...
- Wed Jan 27, 2021 10:09 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: How to understand if -x is insignificant
- Replies: 13
- Views: 576
Re: How to understand if -x is insignificant
Hi! If K < 10^-4, then you can make an approximation and leave out x in the denominator. To confirm whether your approximation is valid, you can do the 5% rule. If (x/initial concentration) x 100 is less than 5%, your approximation is valid and you can carry on with your calculations. However, if (x...
- Sun Jan 24, 2021 9:27 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Strong vs weak acids/bases
- Replies: 6
- Views: 392
Re: Strong vs weak acids/bases
Hi! Since strong acids/bases completely dissociate, we can assume that the concentration of H3O+ ions is equal to the concentration of the strong acid, and similarly we can assume that the concentration of OH- ions is equal to the concentration of the strong base. This is why ice tables are not need...
- Sun Jan 24, 2021 9:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Making the Approximating for X: K or % Ionization?
- Replies: 6
- Views: 297
Re: Making the Approximating for X: K or % Ionization?
Hi! If K < 10^-4, then you can make your approximation of x. However, if you are unsure about whether or not you can make the approximation, you can calculate the % ionization to determine whether the approximation is valid. So, if (x/initial concentration) x 100 < 5%, your approximation is valid. I...
- Sat Jan 23, 2021 1:36 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Percentages
- Replies: 2
- Views: 187
Re: Percentages
I believe that percentage ionization applies to both acids and bases. Percentage deprotonation applies to acids, since acids are proton donors and give up protons. Percentage protonation applies to bases, since bases are proton acceptors and pick up protons.
- Sat Jan 23, 2021 1:32 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ordering from weakest to strongest Acd/base
- Replies: 11
- Views: 607
Re: Ordering from weakest to strongest Acd/base
Hi! A large Ka/Kb and a small pKa/pKb correlates with a stronger acid/base. In other words, the stronger the acid, the larger its Ka value and the smaller its pKa value. Similarly, the stronger the base, the larger its Kb value and the smaller its pKb value. A small Ka/Kb and a larger pKa/pKb correl...
- Sat Jan 23, 2021 1:23 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Tables
- Replies: 36
- Views: 2034
Re: ICE Tables
The change in equilibrium, denoted by the "C" row, is determined by the stoichiometric coefficients. Whether the change in x is a positive or negative value depends on whether the reactant or product is being used up. For example, if the reactant is being used up, then the change will be -...
- Tue Jan 19, 2021 1:04 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Approximately x
- Replies: 18
- Views: 738
Re: Approximately x
Hi! If K < 10^-4, then you can approximate when solving for x. If you are unsure about whether or not your approximation is valid, or if you want to check to see if your approximation is valid, you can substitute values into this expression: (x/initial concentration) x 100. If the value is less than...
- Tue Jan 19, 2021 12:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Water Being Significant in Equilibria
- Replies: 9
- Views: 500
Re: Water Being Significant in Equilibria
Hi! To reiterate what others have said, when water is a solvent (in liquid form), it would not be included in the expression for K because it is present in large excess. However, when water is in a gas form, it would be included in the expression for K. Hope this helps!
- Tue Jan 19, 2021 12:50 pm
- Forum: Ideal Gases
- Topic: Omitting solid/liquid
- Replies: 19
- Views: 810
Re: Omitting solid/liquid
We do not include solids and liquids (solvents) in the expression for K because their concentrations essentially do not change. For example, the change in concentration of solvents are so small that the change is insignificant. In other words, if you take the initial concentration and subtract a rea...
- Sun Jan 17, 2021 9:36 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Total Pressure
- Replies: 26
- Views: 2164
Re: Total Pressure
Hi! The total pressure is the sum of the partial pressures of the reactants and products (gases) at equilibrium. Hope this helps!
- Sun Jan 17, 2021 9:32 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reactants and Products
- Replies: 9
- Views: 445
Re: Reactants and Products
Since the reactions are reversible, there are 2 reactions: the forward reaction and the reverse reaction. In the forward reaction, the reactants are on the left side and the products are on the right side. In the reverse reaction, the product of the forward reaction is the reactant of the reverse re...
- Sun Jan 17, 2021 7:44 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle with Gases
- Replies: 6
- Views: 235
Re: Le Chatelier's Principle with Gases
If the pressure increases by decreasing the volume, then the equilibrium will shift to the side with the lesser amount of moles of gas.
- Fri Jan 15, 2021 9:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Approximating concentrations
- Replies: 4
- Views: 135
Re: Approximating concentrations
I would go with what Dr. Lavelle stated in lecture. If Ka < 10^-4, you can approximate to solve for x. If you are unsure, you can check to see if your approximation is valid by determining whether the value of x you solved for is less than 5% of the initial concentration. If it is, then the approxim...
- Wed Jan 13, 2021 11:16 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Increase in Pressure
- Replies: 31
- Views: 901
Re: Increase in Pressure
Increasing pressure (by decreasing volume) only applies to gases because for liquids and solids, changing the pressure does not change the volume. Therefore, you would only consider the moles of gases.
- Mon Jan 11, 2021 7:20 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: H30+ and OH-
- Replies: 4
- Views: 484
Re: H30+ and OH-
[H30+] and [OH-] must be the same/equal in a neutral solution at 25C because the equilibrium constant for water, Kw, does not change. Since Kw = 1.0 x 10^-14 and is a constant, it will not change. This means that [H30+] = [OH-], and the only value that works for those concentrations is 1.0 x 10^-7.
- Mon Jan 11, 2021 7:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Pure substances
- Replies: 9
- Views: 1226
Re: Pure substances
The concentrations of pure substances (solids and liquids) are not involved in the calculation of the equilibrium constant, K, of chemical reactions because the change in their concentrations is so small, it is negligible. For example, if you have $1 million and you lose $1, you would still say that...
- Mon Jan 11, 2021 6:59 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Approximations
- Replies: 4
- Views: 217
Re: Approximations
Yes, you can use the approximation method when K < 10^-4. In today's lecture (Lecture #4), Dr. Lavelle mentioned that you can use approximations not just for cubic equations, but also for quadratic equations as long as K < 10^-4.
- Sun Jan 10, 2021 7:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q and K
- Replies: 8
- Views: 428
Re: Q and K
Both Q and K are calculated in the same way by calculating the ratio of [P] / [R]. If the chemical reaction is at equilibrium, you are calculating for K, but if the chemical reaction is not at equilibrium, you are calculating for Q.
- Sun Jan 10, 2021 4:54 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Changing pressure
- Replies: 7
- Views: 334
Re: Changing pressure
As others have expressed above, changing the pressure by changing the volume will cause the reaction to change because changing the volume changes the concentration of the products and reactants. On the other hand, changing the volume by adding an inert gas will not cause the reaction to change beca...
- Sun Jan 10, 2021 4:47 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Counting Moles
- Replies: 11
- Views: 579
Re: Counting Moles
As others have stated above, only the moles of gasses are considered when determining the effect of changing the pressure.
- Sun Jan 10, 2021 4:44 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Reaction Quotient Definition
- Replies: 7
- Views: 591
Re: Reaction Quotient Definition
The reaction quotient Q is used when you are calculating the ratio of the concentration of products not at equilibrium to the concentration of reactants not at equilibrium. In other words, you are calculating Q when the reaction is not at equilibrium.
- Wed Jan 06, 2021 6:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homogeneous & Heterogeneous Reactions
- Replies: 4
- Views: 364
Re: Homogeneous & Heterogeneous Reactions
Homogeneous equilibrium refers to all of the reactants and products being in the same phase. Heterogeneous equilibrium refers to at least one or more of the reactants or products being in different phases. The molar concentration of a pure substance (solid or liquid) does not change in a reaction, s...
- Tue Jan 05, 2021 6:03 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Qc vs Kc
- Replies: 15
- Views: 5496
Re: Qc vs Kc
When Qc > Kc, the reverse reaction is favored (reactants are favored).
When Qc < Kc, the forward reaction is favored (products are favored).
When Qc = Kc, neither reactants nor products are favored.
When Qc < Kc, the forward reaction is favored (products are favored).
When Qc = Kc, neither reactants nor products are favored.
- Tue Jan 05, 2021 5:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Pure Substances
- Replies: 5
- Views: 284
Re: Pure Substances
Pure liquids are not involved in the calculation for the equilibrium constant because their change in concentration is so small that the change is negligible. Professor Lavelle used money as an example to illustrate this concept. For example, if you had $1 million and you gained or lost $1, you woul...
- Tue Jan 05, 2021 5:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q vs K
- Replies: 12
- Views: 637
Re: Q vs K
Q is the reaction quotient and K is the equilibrium constant. Both Q and K are calculated in the same way; however, the difference between the two is that Q is calculated when the reaction is not at equilibrium whereas K is calculated when the reaction is at equilibrium. In other words, Q = [P] / [R...
- Mon Jan 04, 2021 10:57 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: KC vs KP [ENDORSED]
- Replies: 6
- Views: 389
Re: KC vs KP [ENDORSED]
The units will tell you whether you are calculating for Kc or Kp. If the molar concentration is given, you are calculating for Kc. If the units of atm/bar is given, you are calculating for Kp.
- Mon Jan 04, 2021 8:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 1 Problem #1
- Replies: 5
- Views: 359
Re: Sapling Week 1 Problem #1
The first statement means that the concentration of the reactants and the concentrations of the products are the same. For example, [R] = [P] = 1.0 M. This statement would be false because the concentrations of the reactants and products do not have to be the same values. The second statement means ...
- Tue Dec 15, 2020 8:42 pm
- Forum: Dipole Moments
- Topic: Dipole Arrows & Electronegativity
- Replies: 6
- Views: 502
Re: Dipole Arrows & Electronegativity
Arrows indicating a dipole moment point in the direction of the more electronegative atom.
- Tue Dec 15, 2020 8:33 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: pka and acidity
- Replies: 6
- Views: 588
Re: pka and acidity
pKa is the -log(Ka) and it tells you how acidic the compound is (the strength of the acid). The lower the pKa value, the stronger the acid. The higher the pKa value, the weaker the acid.
- Tue Dec 15, 2020 8:29 pm
- Forum: Conjugate Acids & Bases
- Topic: What is the difference between a lewis acid and bases and Bronsted acids and bases?
- Replies: 7
- Views: 578
Re: What is the difference between a lewis acid and bases and Bronsted acids and bases?
Yes, you are correct. Bronsted acids are proton donors while bronsted bases are proton acceptors, and lewis acids are lone pair acceptors while lewis bases are lone pair donors.
- Tue Dec 15, 2020 8:17 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis acids and bases vs Bronsted Acids and Bases
- Replies: 4
- Views: 406
Re: Lewis acids and bases vs Bronsted Acids and Bases
A lewis acid is an electron lone-pair acceptor, and a lewis base is an electron lone-pair donor. A bronsted acid is a proton donor, and a bronsted base is a proton acceptor. The difference between lewis acids/bases and bronsted acids/bases is what you are referring to. If you are describing the tran...
- Tue Dec 15, 2020 8:10 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Bond Angles
- Replies: 12
- Views: 696
Re: Bond Angles
The bond angle would be less than 109.5 due to the tetrahedral arrangement. The exact value of the bond angles depends on the atoms being bonded.
- Sat Dec 12, 2020 4:08 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: [OH-] and pOH difference
- Replies: 9
- Views: 1954
Re: [OH-] and pOH difference
[OH-] is the concentration of hydroxide ions (OH-) whereas pOH is the -log of [OH-]. In other words, pOH is a value that indicates how basic the solution is.
- Sat Dec 12, 2020 4:00 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Seesaw vs. trigonal pyramidal
- Replies: 22
- Views: 2418
Re: Seesaw vs. trigonal pyramidal
Seesaw and trigonal pyramidal are not the same shape. Seesaw has 5 regions of electron density (1 of which is a lone pair while 4 are bonding pairs). Trigonal pyramidal has 4 regions of electron density (1 of which is a lone pair while 3 are bonding pairs).
- Sat Dec 12, 2020 3:51 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: wedge and dash
- Replies: 14
- Views: 2769
Re: wedge and dash
As others have said above, wedges and dashes are used to help you visualize the shape and structure of the molecule. If you had a 3-d model of the molecule in front of you, a wedge indicates that the bond is facing towards you while a dash indicates that the bond is facing away from you.
- Sat Dec 12, 2020 3:48 pm
- Forum: Hybridization
- Topic: Lone Pairs & Hybridization
- Replies: 6
- Views: 478
Re: Lone Pairs & Hybridization
Yes, lone pairs come into play in hybridization since it is a region of electron density and regions of electron density contribute to hybridization.
- Wed Dec 09, 2020 3:01 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Sapling Week 10 question
- Replies: 6
- Views: 241
Re: Sapling Week 10 question
When calculating the pH, pOH, [H+], and [OH-] of a solution, it is important to keep these formulas/equations in mind:
[H+] [OH-] = 1.0 x 10^-14
pH + pOH = 14
pH = -log[H+]
pOH = -log[OH-]
[H+] [OH-] = 1.0 x 10^-14
pH + pOH = 14
pH = -log[H+]
pOH = -log[OH-]
- Wed Dec 09, 2020 2:52 am
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: pH vs pKa
- Replies: 9
- Views: 1045
Re: pH vs pKa
To add on, pH is the -log of [H3O+] (hydronium ion concentration) whereas pKa is the -log of the Ka value or acid dissociation constant. The lower the pKa value, the stronger the acid, and the higher the pKa value, the weaker the acid.
- Sun Dec 06, 2020 11:15 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordinate Covalent Bond
- Replies: 6
- Views: 440
Re: Coordinate Covalent Bond
Yes, a coordinate covalent bond connects the ligands to the transition metal ion. The ligand is contributing both electrons since it forms a coordinate covalent bond with the transition metal ion.
- Sun Dec 06, 2020 11:10 am
- Forum: Lewis Acids & Bases
- Topic: Bronsted vs. Lewis bases
- Replies: 11
- Views: 435
Re: Bronsted vs. Lewis bases
Bronsted bases and lewis bases are essentially the same; the only difference is how you use the term to describe the molecule/compound. When referring to protons, bronsted bases are used to indicate that it is a proton acceptor. When referring to electrons, lewis bases are used to indicate that it i...
- Sun Dec 06, 2020 11:04 am
- Forum: Bronsted Acids & Bases
- Topic: Difference between Bronsted Acid and Lewis acid?
- Replies: 4
- Views: 205
Re: Difference between Bronsted Acid and Lewis acid?
To reiterate what others have said, a lewis acid is an electron lone pair acceptor while a Bronsted acid is a proton donor.
- Thu Dec 03, 2020 12:56 am
- Forum: Lewis Acids & Bases
- Topic: Textbook 6A.13
- Replies: 2
- Views: 173
Re: Textbook 6A.13
A lewis acid is an electron acceptor. BF3 is a lewis acid since it is electron deficient, which means that it can accept a lone pair of electrons.
- Thu Dec 03, 2020 12:52 am
- Forum: Bronsted Acids & Bases
- Topic: Bronsted Acids and Bases
- Replies: 7
- Views: 256
Re: Bronsted Acids and Bases
A bronsted acid is a proton donor whereas a bronsted base is a proton acceptor. This is similar to lewis acids and bases where lewis acids are electron acceptors whereas lewis bases are electron donors.
- Wed Dec 02, 2020 2:08 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Oxidation
- Replies: 3
- Views: 243
Re: Oxidation
You can determine whether a ligand is neutral by calculating its formal charge or by memorizing which ligands are neutral. Calculating the formal charge allows you to determine the charge of the ligand, which will help you calculate the oxidation number of the transitional metal since the individual...
- Wed Dec 02, 2020 1:59 am
- Forum: Naming
- Topic: Lecture Example [Co(Nh3)5 Cl]Cl2H2O
- Replies: 8
- Views: 406
Re: Lecture Example [Co(Nh3)5 Cl]Cl2H2O
Since the Cl and H20 are outside of the brackets, they do not interact directly with the transition metal and therefore are named as they normally are. The rules for naming coordination compounds only apply to the molecules/ions inside of the brackets.
- Wed Dec 02, 2020 1:53 am
- Forum: Naming
- Topic: use of bis,tris,etc
- Replies: 3
- Views: 205
Re: use of bis,tris,etc
You would use the prefixes bis-, tris-, tetrakis-, or pentakis- if the ligand has the prefixes di-, tri-, or tetra- in its name or if the ligand is polydentate. For your example the name of the coordination compound is bisethylenediammine.
- Sun Nov 29, 2020 8:42 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: sigma vs pi bonds
- Replies: 33
- Views: 2240
Re: sigma vs pi bonds
Hi! A sigma bond is a bond that is formed when two orbitals, each with 1 electron, interact end-to-end. A pi bond, on the other hand, is a bond that is formed when two orbitals, each with 1 electron, overlap side-by-side. All single bonds are sigma bonds. A double bond has one sigma bond and one pi ...
- Sun Nov 29, 2020 8:30 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond angles
- Replies: 7
- Views: 311
Re: Bond angles
Since bond angles are experimentally determined, we are not able to definitively state what the bond angles between atoms are. However, we can use the VSEPR model to estimate what the bond angle should be. Identifying the electron arrangement of the molecule will help us qualitatively determine the ...
- Fri Nov 27, 2020 5:35 pm
- Forum: Hybridization
- Topic: Single Bonds and Sigma Bonds
- Replies: 23
- Views: 1226
Re: Single Bonds and Sigma Bonds
A single bond is a sigma bond. A sigma bond is when 2 orbitals, each with 1 electron, interact end-to-end to form a bond. When two atoms are bound by more than one covalent bond, one of those bonds will be a sigma bond, and the additional bonds will be pi bonds.
- Fri Nov 27, 2020 5:28 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: coordination number
- Replies: 13
- Views: 628
Re: coordination number
The coordination number is the number of bonds present within the molecule. In [Fe(CN)6]^4-, the coordination number is 6 since there are 6 things bonded to the central atom.
- Fri Nov 27, 2020 5:24 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shape vs Polarity
- Replies: 11
- Views: 686
Re: Shape vs Polarity
When naming the shape of a molecule, you would only consider the position of the bound atoms (bonding pairs). Considering the regions of electron density (bonding pairs and lone pairs) allows you to determine the electron arrangement of the molecule. Having different atoms surrounding the central at...
- Wed Nov 25, 2020 9:56 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: What is bond order?
- Replies: 8
- Views: 539
Re: What is bond order?
As others have said above, bond order is the number of bonds present between 2 atoms. If there is a single bond between 2 atoms, the bond order is 1. If there is a double bond between 2 atoms, the bond order is 2. If there is a triple bond between 2 atoms, the bond order is 3.
- Wed Nov 25, 2020 9:50 am
- Forum: Ionic & Covalent Bonds
- Topic: More Covalent
- Replies: 8
- Views: 578
Re: More Covalent
To determine if a covalent bond is strong, you can determine how many bonds the molecule has. Triple bonds indicate the strongest bond, double bonds indicate a stronger bond, and single bonds are the weakest bonds. You can also use the atomic radius to determine the bond length as well. For example,...
- Wed Nov 25, 2020 9:43 am
- Forum: Ionic & Covalent Bonds
- Topic: Differentiating Between Ionic and Covalent
- Replies: 3
- Views: 299
Re: Differentiating Between Ionic and Covalent
Ionic bonds are typically formed between a metal and a nonmetal while covalent bonds are typically formed between 2 nonmetals. An atom on the far left of the periodic table and an atom on the far right would form an ionic bond since the electronegativity difference is higher while 2 atoms close toge...
- Wed Nov 25, 2020 9:40 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Reason why lone pairs decrease bond angle
- Replies: 7
- Views: 517
Re: Reason why lone pairs decrease bond angle
Hi! Lone pairs occupy a larger volume, and the repulsion strength between a lone pair and a bonding pair is greater than that of a bonding pair and a bonding pair. Due to this, the lone pairs push down on the bonded pairs, distorting (decreasing) the bond angles. Hope this helps!
- Wed Nov 25, 2020 9:36 am
- Forum: Lewis Structures
- Topic: Octet Rule
- Replies: 17
- Views: 1232
Re: Octet Rule
The octet rule is more of a guideline as there are some exceptions to it. For example, an expanded valence shell is an exception to the octet rule. Atoms in period 3 or higher can accommodate more than 8 valence electrons.
- Sun Nov 22, 2020 8:09 pm
- Forum: Sigma & Pi Bonds
- Topic: Pi bonds and Sigma bonds
- Replies: 3
- Views: 272
Re: Pi bonds and Sigma bonds
Sigma bonds are present in every covalent bond (so they are present in single, double, and triple bonds), while pi bonds are present in double and triple bonds. For example, if there is a single bond, it is a sigma bond. In a double bond there is 1 sigma bond and 1 pi bond, and in a triple bond ther...
- Sun Nov 22, 2020 8:05 pm
- Forum: Lewis Structures
- Topic: Polar and non polar elements
- Replies: 9
- Views: 640
Re: Polar and non polar elements
I'm not sure if this is true, but I think they technically can? For example, a molecule can have polar bonds, which describes a polar characteristic. However, the molecule may be nonpolar overall if the dipole moments cancel out, which describes a nonpolar characteristic.
- Sun Nov 22, 2020 8:01 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: repulsion strength
- Replies: 10
- Views: 315
Re: repulsion strength
The electron repulsion between lone pairs is stronger than the repulsion between bonding pairs since lone pairs occupy a larger volume. In other words, since lone pairs occupy a larger volume, they are able to push down on the bonded pairs, which is why lone-lone pair repulsion is stronger compared ...
- Thu Nov 19, 2020 1:53 am
- Forum: Lewis Structures
- Topic: radicals
- Replies: 4
- Views: 235
Re: radicals
I agree with the above posts. Radicals are exceptions to the octet rule since they have an unpaired electron or an odd number of electrons. Since, CH3 and OH have 7 electrons, there will be an unpair electron in the lewis structure.