## Search found 126 matches

Fri Mar 13, 2020 8:45 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Using Steady State Approx/Pre-Equilibrium Approx
Replies: 2
Views: 49

### Re: Using Steady State Approx/Pre-Equilibrium Approx

The pre equilibrium approach basically accounts for the rate-limiting reaction to be the rate law for the overall reaction. Furthermore, Dr. Lavelle says not to worry about the steady state approach, since it would not be covered on the syllabus.
Thu Mar 12, 2020 6:23 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: midterm question 3B
Replies: 1
Views: 101

### Re: midterm question 3B

Since 50 mL of 2M HCl and 50 mL of 2M NaOH is the most concentrated solution and makes the least amount of water as a product, it would be the right answer. We would need to make sure that the least amount of water is produced, since water has a very high specific heat capacity, which would hinder a...
Thu Mar 12, 2020 5:33 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: when doesn't a solid's temp change?
Replies: 2
Views: 120

### Re: when doesn't a solid's temp change?

You're definitely correct. You would need to first calculate the temperature change of the copper as it absorbs 65 J of energy, and once you get that temperature, you would then calculate the change in entropy by plugging it into the entropy equation that deals with changes in temperature. Hope this...
Thu Mar 12, 2020 5:28 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: 7A.17
Replies: 2
Views: 80

### Re: 7A.17

It is absolutely necessary to concert your answer to mols before doing many of the calculations, since a lot of them involve exponents and logarithms, which would lead to a different answer if not converted beforehand.
Thu Mar 12, 2020 5:22 am
Forum: Second Order Reactions
Topic: Stoichiometric coefficients
Replies: 2
Views: 80

### Re: Stoichiometric coefficients

If there are stoichiometric coefficients, then the overall rate of the reaction would change. For the chemical reaction aA ----> bB, the rate would equal (-1/a)*d[A]/dt = (1/b)*d[B]/dt, where a and b would be the stoichiometric coefficients of the reaction. Setting these equal to the experimentally ...
Sun Mar 08, 2020 10:30 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7C.7: Rate laws
Replies: 2
Views: 54

### Re: 7C.7: Rate laws

We would only use a reverse reaction rate if the book specified to do so, or if the chemical reaction is an equilibria chemical reaction. Remember that once the system is in equilibrium, the forward reaction rate equals the reverse reaction rate.
Sun Mar 08, 2020 10:28 pm
Forum: Biological Examples (*DNA Structural Transitions, etc.)
Topic: Application in Biology
Replies: 2
Views: 95

### Re: Application in Biology

I would suggest looking at Dr. Lavelle's outlines on his website and make sure that you truly understand everything listed on them. Other than that, it is always useful to know all of their biological significances since it might help you connect numerous chemistry concepts together on the final!
Sun Mar 08, 2020 10:26 pm
Forum: General Rate Laws
Topic: Effect on rxn rate
Replies: 2
Views: 27

### Re: Effect on rxn rate

This would all depend on which order the reactants are at. For example, for a first order reaction, the rate of the reaction will be proportional 1:1 with the reactant, while in a second order reaction, the rate of the reaction would be exponential to the factor of two as compared with the reactant.
Sun Mar 08, 2020 10:24 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: order
Replies: 4
Views: 115

### Re: order

Usually, to determine the order of a certain reaction, you would need to do it through experimental results that Lavelle will provide for you on the exam. Remember not to just use the coefficients from the chemical reaction! That is only for the equilibrium constant.
Sun Mar 08, 2020 10:23 pm
Forum: General Rate Laws
Topic: arrhennius question
Replies: 4
Views: 48

### Re: arrhennius question

You would need to use the Arrhenius equation whenever you would calculate the activation energy, or the reaction constant from a change in temperature.
Sat Feb 29, 2020 4:31 pm
Forum: Balancing Redox Reactions
Topic: Oxidizing/reducing agent
Replies: 18
Views: 271

### Re: Oxidizing/reducing agent

An oxidizing agent is a substance that gets reduced, while a reducing agent is a substance that gets oxidized. For example, let's say we have substance A (reducing agent) and substance B (oxidizing agent). An easier way of conceptualizing this would be to think that substance A needs to give away it...
Sat Feb 29, 2020 4:25 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolysis
Replies: 1
Views: 44

### Re: Electrolysis

The first one would represent the reduction of water, since we are reducing water by giving it electrons. While the bottom equation represents the formation of water because of the reduction of oxygen.
Sat Feb 29, 2020 4:23 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6L. 1
Replies: 2
Views: 54

### Re: 6L. 1

A shorter way of determining how many mols of electrons are being transferred would be to just look at the oxidizing or reducing agent in the equation and determine how many mols of electrons it is losing or gaining. Assuming the equation is balanced, that would be the n in your equation. Hope this ...
Sat Feb 29, 2020 4:22 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cells and Nernst Equation
Replies: 4
Views: 73

### Re: Concentration Cells and Nernst Equation

In general, you are going to have to use the Nernst equation when we are dealing with a concentration cell, since concentrations not at equilibrium of the cell can affect the EMF of the cell. Other than that, you could use it for cells that are not at their respective equilibrium concentrations of p...
Fri Feb 28, 2020 8:26 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Acid/Base Concentration Cells
Replies: 1
Views: 42

### Re: Acid/Base Concentration Cells

Since pH = -log[H+], we can easily calculate the concentration of the H+ ions, and thus we would have a concentration cell based off of "pH". We would then use these concentrations to get a range of the minimum and maximum concentration difference and thus the min/max Ecell. This would the...
Mon Feb 24, 2020 6:31 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework Problems from Outline 5 or 6 this week?
Replies: 2
Views: 145

### Re: Homework Problems from Outline 5 or 6 this week?

Outline 5, since it covers all of electrochemistry, but you can still get started on outline 6 as long as you understand the material beforehand.
Mon Feb 24, 2020 6:30 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Solar Panels
Replies: 1
Views: 24

### Re: Solar Panels

As far as I know, as the electrons on the solar panel grid get excited, they move onto a different surface above this grid. This would create one grid with electrons and one panel without. Paired with conductors and a wire, we would then have the electrons flow back into its original grid and genera...
Sun Feb 23, 2020 10:29 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: H2O, O2 in 6L7b
Replies: 1
Views: 43

### Re: H2O, O2 in 6L7b

Since you know that oxygen in an acidic solution would reduce the oxygen to H2O, because of the abundance of protons in the acidic solution. Thus, the cathode would be oxygen in the acidic solution and the anode would be oxygen in the basic solution.
Sun Feb 23, 2020 10:10 am
Forum: Balancing Redox Reactions
Topic: Oxidation number of H
Replies: 6
Views: 87

### Re: Oxidation number of H

For the large part of this course, if the hydrogen is bonded to an anion, then we would assume that the oxidation number for the hydrogen is +1. However, in the case of metal and salt hydrides, like LiH or CaH2, since it is bonded to a cation, hydrogen would have an oxidation number of -1.
Sun Feb 23, 2020 10:07 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: standard conditions
Replies: 8
Views: 93

### Re: standard conditions

Standard Condition is always going to be 1M when dealing with concentrations, 1 atm when dealing with pressures at 273.15K.
Sun Feb 23, 2020 10:06 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Positive Voltage
Replies: 2
Views: 17

### Re: Positive Voltage

For the most part, yes. Since most of the problems require you to either find the concentration of reactants, products, the voltage of the cell, etc. , you should assume that there will be a positive voltage unless specified.
Sun Feb 23, 2020 10:04 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cell emf
Replies: 3
Views: 43

### Re: Galvanic Cell emf

When emf is negative, the cell does not "absorb energy". All this means is that the reaction would be unfavorable and thus non-spontaneous. Hope this helps.
Sun Feb 16, 2020 6:28 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Autoprotolysis
Replies: 6
Views: 176

### Re: Autoprotolysis

There are numerous examples of autoprotolysis other than H20, since autoprotolysis is the proton transfer between two of the same molecules. An example would be acetic acid: CH3COOH <------> CH3COO- + CH3COOH2+. In addition, the Keq would likely be very very small, favoring the reactants, since they...
Sat Feb 15, 2020 10:21 pm
Forum: Van't Hoff Equation
Topic: Enthalpy, Entropy, and Gibbs Free Energy
Replies: 7
Views: 62

### Re: Enthalpy, Entropy, and Gibbs Free Energy

Don't forget that the temperature is changing in the Van't Hoff Equation, since it relates the Keq with a change in temperature. Thus, this makes the change in Gibbs Free Energy not constant.
Sat Feb 15, 2020 10:13 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions
Replies: 2
Views: 19

### Re: Balancing Redox Reactions

We should always keep track of the electron transfer between the molecules that are getting reduced and oxidized, since we are assuming that throughout this reaction, the mass of all the molecules is conserved, thus the electrons as well.
Sat Feb 15, 2020 10:12 pm
Forum: Calculating Work of Expansion
Topic: isobaric compression
Replies: 7
Views: 151

### Re: isobaric compression

To understand why pressure does not change during an isobaric process, we need to first understand what "pressure" is. Pressure is directly proportional to the frequency at which the gas molecules collide with the piston and their speed. In order to conserve the pressure throughout this pr...
Sat Feb 15, 2020 9:59 pm
Forum: Student Social/Study Group
Topic: Preparing for Exam Content
Replies: 7
Views: 194

### Re: Preparing for Exam Content

Honestly, I do feel the same way about this midterm, since it did involve high level problem solving skills which you cannot really prepare for except for just practicing problems. However, I think that the best way to prepare for a midterm like this would still be more and more practice problems un...
Sun Feb 09, 2020 8:09 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Degeneracy
Replies: 5
Views: 63

### Re: Degeneracy

We would use this equation when we are given the degeneracy, but Lavelle might make us calculate W first. Remember that W=(# of positions the molecules could be at)^(# of atoms or molecules).
Sun Feb 09, 2020 8:05 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Ideal Gas Chart
Replies: 3
Views: 41

### Re: Ideal Gas Chart

Could someone please summarize this chart please? What is R and why would it be the way it is on the chart?
Sun Feb 09, 2020 7:59 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy on midterm
Replies: 5
Views: 91

### Re: Gibbs Free Energy on midterm

Yes, that equation and also the fact that G is also a state function. This would mean that the standard free energy formation of a reaction would equal the standard free energy formation of the products minus the standard free energy formation of the reactants. This could come in handy on the midterm.
Sun Feb 09, 2020 7:57 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter Calculations
Replies: 3
Views: 25

### Re: Calorimeter Calculations

There is no difference between these equations. q=CAT happens when m=1 g.
Sun Feb 09, 2020 7:56 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calculating q
Replies: 4
Views: 63

### Re: Calculating q

When n=1 mol, the molar heat capacity (q=nCAT) would equal CAT. Similarly, when m=1 g, the specific heat capacity (q=mCAT) would equal CAT.
Sun Feb 09, 2020 7:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: finding pH from concentration of H30+
Replies: 2
Views: 54

### Re: finding pH from concentration of H30+

Having a concentration of 3.1M would definitely result in a negative pH. There are certain acids called superacids that do result in a negative pH, since they are so strong. Thus, remember that if you get a negative pH with a high molar concentration of H30+ ions, the formula is still -log(concentra...
Sun Feb 09, 2020 7:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Halogen equilibrium reaction
Replies: 1
Views: 38

### Re: Halogen equilibrium reaction

To determine how this reaction is affected by temperature, you would need to look if the reaction is exothermic or endothermic. If the reaction is endothermic (which I assume it is), then increasing temperature would favor product formation and vice versa for if the reaction is exothermic.
Sun Feb 09, 2020 7:43 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Difference between qv and qp
Replies: 5
Views: 66

### Re: Difference between qv and qp

It is just a difference in notation. I do not really know why he makes it this confusing.
Sun Feb 02, 2020 2:35 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Difference between qv and qp
Replies: 5
Views: 66

### Re: Difference between qv and qp

Under conditions of constant pressure, the piston has to be freely movable, thus accommodating for the constant pressure when heated. This would mean that under constant pressure the q would be the enthalpy change or equivalent to the amount of heat added. However, under conditions of constant volum...
Sun Feb 02, 2020 1:11 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Constant pressure
Replies: 19
Views: 199

### Re: Constant pressure

Yes they are referring to constant external pressure, since a dynamic external pressure would do unnecessary work on a system, and thus be unreasonable problem to solve.
Sun Feb 02, 2020 1:02 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 5 Homework
Replies: 7
Views: 101

### Re: Week 5 Homework

Yes, since Lavelle just finished Thermochemistry and just started Thermodynamics.
Sun Feb 02, 2020 12:41 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4C.3
Replies: 1
Views: 19

### Re: 4C.3

I assume that he might give us a brief overview on this material very soon. The general idea is that most of the energy in a molecule would be stored in the vibrations of their respective bonds, rotations of single bonds, and translations.
Sun Feb 02, 2020 12:29 pm
Forum: Calculating Work of Expansion
Topic: Equation
Replies: 4
Views: 40

### Re: Equation

We utilize the integral when both the pressure and volume of a system are changing. This is because if we have a system with constant pressure and a change in volume, the integral would basically be the area of the rectangle which is P*(delta)V and no need to use calculus. If the pressure in changin...
Sun Feb 02, 2020 12:25 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: total entropy change
Replies: 1
Views: 49

### Re: total entropy change

When the total entropy of a system is negative, this would indicate that the final entropy state of the system is less than its initial, or in simple terms, the system has become more ordered while increasing the disorder of its surroundings. The reverse reaction then, might be spontaneous, as it wo...
Sat Jan 25, 2020 4:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard enthalpy
Replies: 2
Views: 19

### Re: Standard enthalpy

They are essentially the same thing, but with one small difference. Standard reaction enthalpy would be the difference between the enthalpies of the reactants and products, but standard enthalpy of formation would be the difference between the enthalpies of the reactants and products in their standa...
Sat Jan 25, 2020 4:09 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Water Properties
Replies: 3
Views: 119

### Re: Water Properties

Amphoteric molecules are molecules that are both acidic and basic in character, while amphiprotic molecules are molecules that can both donate and receive H+ ions. Usually an amphoteric molecule is also amphiprotic due to the commonality of being both an acid/base and donating/receiving H+ ions. For...
Sat Jan 25, 2020 4:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpies
Replies: 2
Views: 30

### Re: Standard Reaction Enthalpies

Since no chemical reaction takes place, no bonds or broken nor formed. Thus, the standard reaction enthalpy change would be 0. This is the only element to consider when looking at a reaction that does not occur under standard conditions.
Sat Jan 25, 2020 3:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: H3O+ < 10^-7 Neutral?
Replies: 1
Views: 36

### Re: H3O+ < 10^-7 Neutral?

Since a single water molecule consists of H2O, when it ionizes into H30+ then we would have a remainder of one hydroxide molecule (OH-). Thus a concentration of 10^-7 mol/L H3O+ would mean that the solution also has 10^-7 mol/L OH-, and thus the solution would be neutral or a pH of 7.
Sat Jan 25, 2020 11:23 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: sign changes in bond enthalpy
Replies: 5
Views: 65

### Re: sign changes in bond enthalpy

When you're given the bond enthalpies on a table, you would make the enthalpies negative when bonds are formed (the products). This is because the net enthalpy of a reaction is the enthalpies of bonds broken minus the bonds formed.
Sun Jan 19, 2020 11:58 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Change in Temperature
Replies: 2
Views: 31

### Re: Change in Temperature

An increase in temperature in endothermic reactions would favor product formation, since it requires energy or heat for the products to form. Furthermore, in an endothermic reaction an increase in temperature would cause an increase in K, and thus more product formation. This effect is the opposite ...
Sun Jan 19, 2020 11:51 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: acids and bases
Replies: 4
Views: 54

### Re: acids and bases

Yes, acid and base reactions are just like other reactions and most of the time are at equilibrium, unless the problem states otherwise.
Sat Jan 18, 2020 10:03 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Why does only Temperature change K?
Replies: 2
Views: 33

### Re: Why does only Temperature change K?

K is very energy dependent, because adding or taking away heat from a chemical reaction would change the overall kinetics of the reaction itself, and thus affect K. Changing the concentrations would not change K, as increasing the concentration of products would result in an increase in concentratio...
Sat Jan 18, 2020 9:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Decreasing pressure
Replies: 4
Views: 48

### Re: Decreasing pressure

Decreasing the pressure would mean that it would increase the volume of the reactants/products. This would indicate that the concentration of the reactants/products would decrease. This would mean that the reaction would shift towards the side with the least amount of moles, since it would have a lo...
Tue Jan 14, 2020 4:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.16
Replies: 2
Views: 38

### Re: 5I.16

Yes, the K value would only include the partial pressure of gases or their concentrations. Furthermore, solids and liquids would not be present in the equation.
Tue Jan 14, 2020 4:38 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 1
Replies: 2
Views: 58

### Re: Test 1

I am fairly sure that Dr. Lavelle will go over acid/base titrations between tomorrow's lecture or Friday's. Anything he taught from week 1 is fair game for the first test.
Sat Jan 11, 2020 2:31 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic and endothermic reactions
Replies: 4
Views: 42

### Re: Exothermic and endothermic reactions

If the reaction is exothermic, then adding heat to the reaction would make the reverse reaction more favorable, and thus more reactants would form. Vice versa for removing heat. If the reaction is endothermic, then adding heat would make the forward reaction more favorable. Vice versa for removing h...
Sat Jan 11, 2020 2:29 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changes in Pressure
Replies: 3
Views: 77

### Changes in Pressure

During Dr.Lavelle's last lecture he mentioned that changes in pressure does not necessarily cause a forward or reverse reaction to be favored. Instead, he said that it all relies on changes in concentration not change in pressure. Can someone please explain this?
Sat Jan 11, 2020 2:20 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.13
Replies: 3
Views: 43

### Re: 5I.13

Usually, you would use Kp for gases and Kc for other compounds with given concentration. However, whichever you use, you would get the same equilibrium ratio, so it does not really matter.
Sat Jan 11, 2020 2:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Table 5G.2
Replies: 5
Views: 52

### Re: Table 5G.2

Typically, you would use Kc when you are given the concentration of the compounds, while Kp when you are working with gases. But in this case, it would not really matter which ones you use to calculate, since the equilibrium ratio would be the same.
Sat Jan 11, 2020 11:48 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table Calculations
Replies: 4
Views: 31

### Re: ICE Table Calculations

You would need to know the quadratic equation only when you do not know the change in initial partial pressure and the final partial pressure. In order to compensate for this, we would say that the change would be x and thus the final partial pressure for the products would be x, while the final par...
Sat Dec 07, 2019 2:47 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH and pKA for acids
Replies: 1
Views: 29

### Re: pH and pKA for acids

If pH<PKa, then the solution will be more acidic. This is due to the shift in chemical equilibrium, as the weak acid will deprotonate in order to shift the solution's acidity so that pH=PKa.
Wed Dec 04, 2019 1:53 pm
Forum: Bronsted Acids & Bases
Topic: HF is a weak acid?
Replies: 8
Views: 176

### Re: HF is a weak acid?

Since Flourine is such a small molecule, the bond between fluorine and the hydrogen is the shortest when comparing the other halogen-based acids. This would mean that it is much more difficult to break this bond and thus less H+ exist in an aqueous solution of HF.
Wed Dec 04, 2019 1:50 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: atomic orbital probability
Replies: 2
Views: 215

### Re: atomic orbital probability

I think this means to make sure that you understand that the atomic orbitals are electron density probability regions (areas in which the electrons exist, not the individual electrons themselves). This is because of the Heisenberg's uncertainty principle, since we cannot know the momentum and the po...
Wed Dec 04, 2019 1:48 pm
Forum: Conjugate Acids & Bases
Topic: Conjugate Acids and Bases
Replies: 6
Views: 72

### Re: Conjugate Acids and Bases

A general guidline to figure out conjugate acids and bases would be to draw the formula out and first identify the acids and bases involved in the reaction. Then, looking at the products, the product of the acid would be its conjugate base and the product of the base would be its conjugate acid. For...
Wed Dec 04, 2019 1:44 pm
Forum: Naming
Topic: Naming for Hydrocarbons
Replies: 2
Views: 56

### Re: Naming for Hydrocarbons

I really doubt that you would have to memorize the hydrocarbon structures, since that is basically organic chemistry. It would however be helpful to know some common hydrocarbons, such as benzene, methane, and ethane.
Wed Dec 04, 2019 1:42 pm
Forum: Conjugate Acids & Bases
Topic: Oxoacids
Replies: 4
Views: 137

### Re: Oxoacids

An oxoacid is any acid containing an oxygen group. The presence of the oxygen group helps withdraw the electrons and stabilize the structure, which would then result in a stronger acid.
Wed Dec 04, 2019 1:41 pm
Forum: Bronsted Acids & Bases
Topic: HOI vs HOCl
Replies: 3
Views: 79

### Re: HOI vs HOCl

HOCl and HOI are both oxoacids and act quite differently, because of the oxygen involved in their structure. Since the electrons are withdrawn (or pulled due to the high electronegativity of oxygen and chlorine), they are delocalized and are more prone to get rid of the H+ proton than HOI. But when ...
Tue Dec 03, 2019 2:59 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 3
Views: 54

### Re: Ligands

Drawing the Lewis structure and calculating the charges definitely would give you the net charge of the molecule. However, it would be much easier and more efficient if you just memorized the charges of common polyatomics and ligands.
Tue Dec 03, 2019 2:35 pm
Forum: Hybridization
Topic: Conjugation and hybridization
Replies: 1
Views: 40

### Re: Conjugation and hybridization

In chemistry, a conjugated system generally refers to a molecule, in which the electrons are delocalized and are much more stable. this usually occurs in the hybridization of the p-orbitals involved in the respective atoms. Since the electrons are delocalized, the molecule is much more stable. I don...
Tue Dec 03, 2019 2:32 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Final
Replies: 2
Views: 46

### Re: Final

I think it would be helpful to understand the chemical properties of EDTA and their purposes when they act as ligands. Other than that, I would not expect him to ask us its molecular structure.
Tue Dec 03, 2019 12:14 pm
Forum: Lewis Acids & Bases
Topic: Products of Lewis Acids and Bases
Replies: 1
Views: 40

### Re: Products of Lewis Acids and Bases

The product of Cl- + SO2 would essentially be SO2Cl. This could be very easily figured out by drawing their respective Lewis structures and checking for any lone pairs which the atoms can either donate or receive, Since SO2 has one lone electron, and chlorine has 7 valence electrons, they can form a...
Tue Dec 03, 2019 12:10 pm
Forum: Bronsted Acids & Bases
Topic: J.7b
Replies: 2
Views: 67

### Re: J.7b

Since you know that nitrate has a negative charge, it would most likely be bonded to a hydrogen and act as an acid. Vice versa for zinc, because of its positive charge. Thus, this reaction takes into consideration that zinc hydroxide (a base) reacts with nitric acid (an acid) and forms a salt (zinc ...
Tue Dec 03, 2019 12:07 pm
Forum: Conjugate Acids & Bases
Topic: H-F in conjugate bases
Replies: 3
Views: 72

### Re: H-F in conjugate bases

Since the other halogen based acids are much stronger than HF (due to weaker bonds between hydrogen and the halogen), they would not be strong conjugate bases. HF would be the only halogen based acid that is a strong conjugate base for a weaker acid.
Tue Dec 03, 2019 12:04 pm
Forum: General Science Questions
Topic: Exam Subjects
Replies: 5
Views: 270

### Re: Exam Subjects

I really doubt that the exam will be on topics that we haven't yet tested on. It will most likely be an equal distribution of topics from before the midterm and after the midterm. I'm assuming that the exam will be hard, not because of the content, but the combination of different concepts. Or bette...
Tue Dec 03, 2019 12:01 pm
Forum: Industrial Examples
Topic: Bond rotations
Replies: 4
Views: 103

### Re: Bond rotations

I would assume that resonance structures would not rotate, since their electrons are still delocalized throughout the molecule, which expresses a similar 3 dimensional structure as a double bond (1 sigma and 1 pi bond), and thus not allowing for rotation.
Tue Dec 03, 2019 12:00 pm
Forum: Amphoteric Compounds
Topic: Amphoteric, Amphiprotic, Polyprotic
Replies: 2
Views: 57

### Re: Amphoteric, Amphiprotic, Polyprotic

Firstly, a molecule is ionic based off the electronegativity difference between its bonded atoms. If it's great enough, then it displays ionic character. Next, a polyprotic acid is an acid that could donate multiple protons (H+) instead of one. An example of a polyprotic acid is H2SO4, where 2 H+ ca...
Mon Nov 25, 2019 1:12 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: edta
Replies: 1
Views: 55

### Re: edta

The EDTA ligand would form an octahedral complex once it's bonded to the metal ion and it would wrap around it. The molecule itself does not look like it can wrap around the central transition metal ion, but because of VSPER theory, its shape is very complicated due to numerous trigonal planar and t...
Mon Nov 25, 2019 1:05 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9c3
Replies: 1
Views: 65

### Re: 9c3

To do 9C3, you would need to understand how they write the coordination complex and translate it to the chemical formula. Once you understand that, the easiest way to do the problem would just be to break it down bit by bit. potassium hexacyanidochromate(III) becomes potassium (K), hexacyanido (6 cy...
Mon Nov 25, 2019 12:32 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C. 5
Replies: 1
Views: 54

### Re: 9C. 5

For a molecule to be a polydentate, it must must donate more than one pair of electrons to the central transition metal. Also, because of the shape of certain molecules, they are only able to donate one pair of electrons to the central atom, even if they have more lone pairs. Taking all this into ac...
Mon Nov 25, 2019 12:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelateing Ligands
Replies: 3
Views: 84

### Re: Chelateing Ligands

A chelate is a compound where the central atom is essentially "wrapped" inside a ring created by more molecules. These molecules need to be bonded to each other in a ring shape, essentially allowing for greater stability of the entire molecule. You can tell whether a compound is a chelate ...
Mon Nov 25, 2019 12:21 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9 C.7
Replies: 1
Views: 59

### Re: 9 C.7

To form a chelating complex, you would need the molecules that form a ring relatively close to each other, so they can bond with each other. This essentially "wraps" the central atom in a ring, and thus makes it a chelating complex. Since isomers a and c do not have the amine group close e...
Sat Nov 23, 2019 2:56 pm
Forum: Naming
Topic: English name vs Latin stem for transition metals
Replies: 1
Views: 23

### Re: English name vs Latin stem for transition metals

From all the problems that I have done, I think iron is the only exception where we use the Latin name for the transition metal. But all the other times we should use the English name.
Sat Nov 23, 2019 2:55 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelates
Replies: 1
Views: 30

### Re: Chelates

Chelates are able to bind to cations tightly because of their stable ring structure, allowing for more rigidity. In simpler terms, the cation is essentially "tucked in" the chelating complex, and the rings around it allow for a much more stable and strong shape.
Sat Nov 23, 2019 2:54 pm
Forum: Resonance Structures
Topic: Resonance and Naming
Replies: 11
Views: 298

### Re: Resonance and Naming

Resonance should not affect the way we name chemical compounds in this course.
Mon Nov 18, 2019 1:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles with different atoms surrounding a central atom
Replies: 1
Views: 25

### Re: Bond angles with different atoms surrounding a central atom

In molecules, such as CH2F2 the bond angles would of course not be exactly 109.5 degrees, because of the different size of the atoms attached to the carbon. However, for the sake of simplification, we can assume that they are roughly 109.5 degrees. This would indicate that the F-C-F bond angle would...
Mon Nov 18, 2019 1:16 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic vs covalent
Replies: 2
Views: 105

### Re: Ionic vs covalent

The best way to tell the bonds apart would be to look at the electronegativity difference between the two atoms. The greater the electronegativity difference, the greater the ionic character behind that bond and vice versa. Furthermore, you can analyze the polarizability of the two atoms to figure o...
Mon Nov 18, 2019 1:10 pm
Forum: Hybridization
Topic: 2F.9
Replies: 1
Views: 65

### Re: 2F.9

To start this problem, you would first need to sketch the Lewis structures of each molecule, since you need the Lewis structure to correctly identify the VSEPR model for each molecule. Then, according to the VSEPR model, you can calculate the electron density clouds around each central molecule (Pho...
Mon Nov 18, 2019 1:08 pm
Forum: Hybridization
Topic: Hybridization example problem
Replies: 1
Views: 41

### Re: Hybridization example problem

The hybridization on all the carbons would be sp2, since each carbon has 3 electron density clouds. The hybridization on the oxygen attached would be sp3, since the oxygen has 4 electron density clouds.
Mon Nov 18, 2019 1:05 pm
Forum: Hybridization
Topic: 2.19
Replies: 1
Views: 40

### Re: 2.19

Part D of this question asks for which molecule has a more covalent character, not the one with the greatest lattice energy. Since Tl2O would have a charge of +3, it would be more polarizing, and thus a greater covalent character.
Sun Nov 17, 2019 10:06 am
Forum: Dipole Moments
Topic: Dipole-Dipole
Replies: 2
Views: 43

### Re: Dipole-Dipole

It is particularly difficult to deduce dipole moments by looking at a chemical formula. It would be much more helpful if you drew out the Lewis structure of the molecule and utilizing electronegativity to figure out where the electrons or negative dipole are pulled towards. This would help you under...
Sun Nov 17, 2019 10:03 am
Forum: Determining Molecular Shape (VSEPR)
Topic: T Shape Geometry
Replies: 2
Views: 55

### Re: T Shape Geometry

I would assume that you would need to know T-shaped geometry, since it is the structure of many molecules, such as ClF3, where the Chlorine would have 3 bonded pairs with Fluorine, but 2 lone electron pairs, creating a T-shape.
Sun Nov 17, 2019 10:01 am
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angles less than <109.5
Replies: 4
Views: 65

### Re: bond angles less than <109.5

Even if a molecule with a trigonal pyramidal shape looks to be arranged tetrahedrally (bond angles=109.5), the lone electron pair has a greater electron repulsion strength than a bonded one, forcing the 3 bonded atoms closer to each other, and thus making their bond angles slightly less than 109.5.
Sun Nov 17, 2019 9:59 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Model
Replies: 5
Views: 40

### Re: VSEPR Model

The molecular shape would be the 3 dimensional shape of the molecule, emerging from their respective electron arrangement. A specific electron arrangement between atoms would determine the shape of the molecule, as the electron-electron repulsion would be the force holding its shape.
Sun Nov 17, 2019 9:56 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw Shape
Replies: 3
Views: 39

### Re: Seesaw Shape

The seesaw shape is more favorable, since the most stable structure would be the one with the least electron repulsions. The only way to accomplish this on a structure with 4 bonding pairs and 1 non bonding pair would be to position the electrons in such manner.
Mon Nov 04, 2019 2:47 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Quantum World Guidelines
Replies: 1
Views: 72

### Re: Quantum World Guidelines

Atomic spectroscopy deals with electron transitions within in one atom, while molecular spectroscopy deals with electron transitions in two or more bonded atoms. Since the bonding of atoms alters their orbitals and where the valence electrons are truly located, they would have very similar, but diff...
Mon Nov 04, 2019 2:39 pm
Forum: Coordinate Covalent Bonds
Topic: Coordinate Covalent Bond
Replies: 2
Views: 137

### Re: Coordinate Covalent Bond

A coordinate covalent bond is different from a covalent bond, because instead of both atoms each sharing one electron to form a bond, there is only one atom that donates two of its electrons to form a bond. Coordinate covalent bonds do not just occur in Lewis acids and bases, and could also be found...
Mon Nov 04, 2019 2:28 pm
Forum: Lewis Structures
Topic: When to use brackets
Replies: 2
Views: 76

### Re: When to use brackets

We use brackets when the overall compound has a net charge, or when using ionic molecules, since in ionic molecules, the anions simply strip away the electron from the cation. Thus, leaving the cation with a new positive charge and the anion with the net negative charge.
Mon Nov 04, 2019 2:27 pm
Forum: Lewis Structures
Topic: breaking octet rules with electronegativity
Replies: 2
Views: 46

### Re: breaking octet rules with electronegativity

Correction on the last part of my response: N2O would be most stable when triple bonded to a nitrogen and double bonded to the oxygen*
Mon Nov 04, 2019 2:25 pm
Forum: Lewis Structures
Topic: breaking octet rules with electronegativity
Replies: 2
Views: 46

### Re: breaking octet rules with electronegativity

The reason why you may put the extra electron on one atom and not the other does not depend on electronegativity, but depends on the formal charge. Since it is a universal rule that most things in the universe love to attain maximum stability, the most stable Lewis Structure of a molecule would be t...
Mon Nov 04, 2019 2:19 pm
Forum: Ionic & Covalent Bonds
Topic: Polyatomic Ions
Replies: 2
Views: 77

### Re: Polyatomic Ions

I highly doubt that we need to know any polyatomics, since they most likely will be listed on any one of the questions that have them. But, it is helpful to know these ones: C2H3O2- Acetate CN- Cyanide ClO- Hypochlorite ClO2- Chlorite ClO3- Chlorate ClO4- Perchlorate CO3- Carbonate SO4- Sulfate MnO4...
Mon Oct 28, 2019 2:26 pm
Forum: Trends in The Periodic Table
Replies: 3
Views: 72

This is a very complicated question, but most of the time the ionic radius has the opposite periodic table trend than the atomic radius, since the atomic radius is the general radius of the atom, while the ionic radius would be the general radius of the ion. Since certain atoms lose or gain electron...
Mon Oct 28, 2019 2:06 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 3
Views: 54

### Re: Resonance

If you take NO3- (Nitrate) for example, Nitrogen would need to form a single double bond with Oxygen in order for it to be stable. Since we have 3 Oxygens that it can form a double bond to, we can write out three different Lewis Structures of Nitrate, indicating that it is a resonance structure. Fur...
Mon Oct 28, 2019 2:03 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic spectra post assessment question 42
Replies: 2
Views: 65

### Re: Atomic spectra post assessment question 42

You were really close, but the formula goes like this. Frequency = R ((1/nf^2) - (1/ni^2)), where nf means n (final) indicating that this is where the electron will be at the end and ni meaning n (initial) indicating where it started. I think you switched your initial and final values, resulting in ...