## Search found 61 matches

Thu Mar 14, 2019 3:09 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 1
Views: 79

### Molecularity

I think the slowest elementary step determines the molecularity of the reaction, but if a molecule in the previous fast equation were to cancel with a molecule in the slow equation. Would that molecule still be used to determine molecularity? For example: A\rightleftharpoons 2B (Fast) 2B + C...
Thu Mar 14, 2019 2:47 pm
Forum: General Rate Laws
Topic: 6th Edition #15.85
Replies: 1
Views: 99

### 6th Edition #15.85

In the sixth edition textbook, the problem provides the rate laws derived from elementary steps and asks you to draw a proposed structure for the activated complex. What is the activated complex and how does one draw a proposed complex? For example, part c od the problem provides: "Rate = k[O2]...
Thu Mar 14, 2019 2:39 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Calculating A
Replies: 1
Views: 83

### Calculating A

How does one solve for A, the frequency factor, in the Arrhenius Equation? I think Dr. Lavelle said we wouldn't have to solve for A and we just have to assume it is 1 for this class. Is that true? If not how does one solve for A?
Sat Mar 09, 2019 7:43 pm
Forum: First Order Reactions
Topic: Fractional Rate Constants
Replies: 2
Views: 131

### Fractional Rate Constants

Is it possible to have fractional rate constants? Should we round up/down to the nearest whole number or do we just take the natural log and solve for the rate constant?
Wed Mar 06, 2019 9:38 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Unique Average Rate
Replies: 5
Views: 295

### Unique Average Rate

Can someone explain in simpler terms what the unique average rate is, why we use it, when to use it, and when not to use it? What qualities affect the rate and what qualities do not?
Wed Mar 06, 2019 9:33 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Instantaneous vs Average
Replies: 11
Views: 432

### Instantaneous vs Average

What is the difference between instantaneous rate and average rate?
Wed Feb 27, 2019 9:07 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Ion-selective electrodes [ENDORSED]
Replies: 1
Views: 119

### Ion-selective electrodes[ENDORSED]

In class, Dr. Lavelle listed three different ion-selective electrodes (H+, Na+, and K+). Are these three the most popular and only ion-selective electrodes or are there other ion-selective electrodes?
Wed Feb 27, 2019 9:05 pm
Forum: Balancing Redox Reactions
Topic: Half Reactions in a Basic Solution
Replies: 4
Views: 151

### Half Reactions in a Basic Solution

Can someone give step to step instructions and an example of how balance half reactions in a basic solution? I know you're supposed to balance the element first, then the oxygens, hydrogens, and finally electrons. I don't understand why I have to add water on the same side as OH- because then both s...
Wed Feb 27, 2019 9:02 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge vs Porous Disk
Replies: 1
Views: 76

### Salt Bridge vs Porous Disk

What are the differences and similarities between a salt bridge and a porous disk?
Sat Feb 23, 2019 2:21 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 3
Views: 133

### Salt Bridge

In the cell diagram Dr. Lavelle always draws on the board, what exactly does the salt bridge do?
Thu Feb 21, 2019 11:16 am
Forum: Balancing Redox Reactions
Topic: 1/2 reactions
Replies: 1
Views: 121

### 1/2 reactions

When we are writing out the 1/2 reactions, why do we always write our redox reactions as reductions and not oxidations? Is it possible to solve the same problem but with oxidations reactions?
Thu Feb 21, 2019 11:13 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Oxidation Potential
Replies: 2
Views: 133

### Oxidation Potential

The reduction potential is usually given to us as E°, but if we were even given the oxidation potential would it be the negative value of the reduction potential?
Wed Feb 13, 2019 3:18 pm
Forum: Calculating Work of Expansion
Topic: Change in moles
Replies: 3
Views: 165

### Change in moles

When calculating work under constant pressure the equation is w=-P delta V and can often be substituted as -delta nRT. When we solve for n do we only consider the molecules in the gas phase or do we include all molecules in any phases?
Tue Feb 12, 2019 10:51 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Ideal Gas Constants
Replies: 4
Views: 404

### Ideal Gas Constants

Which constant is for monoatomic, diatomic, linear, and nonlinear?
Tue Feb 12, 2019 8:43 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: equations
Replies: 1
Views: 96

### equations

Is S=nCvln(T2/T1) used only for the calculations of an ideal gas and is S=nRln(V2/V1) used only for the calculations of a gas?
Fri Feb 08, 2019 3:58 pm
Forum: Calculating Work of Expansion
Topic: Nonexpansion work
Replies: 2
Views: 95

### Nonexpansion work

Is there such thing as nonexpansion work, and if so how would one calculate that?
Fri Feb 08, 2019 3:42 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: State Function
Replies: 3
Views: 154

### State Function

Why and how is $\Delta$U a state function but q and w are not?
Mon Feb 04, 2019 11:51 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Reversible vs Irreversible
Replies: 2
Views: 139

### Reversible vs Irreversible

Can someone explain to me in simple terms what's the difference between reversible expansion and irreversible expansion? Which would do the most work, and why?
Mon Jan 28, 2019 5:51 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv and Cp
Replies: 3
Views: 144

### Re: Cv and Cp

Dr. Lavelle mentioned that for Cp you can refer to the ideal gas law PV=nRT, where the number of moles, n, and the universal gas constant, R, would remain unchanged, but the temperature, T, would increase and would, therefore, increase the overall Volume. Work is happening for Cp.
Mon Jan 28, 2019 5:47 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy and Heat Capacity
Replies: 2
Views: 101

### Enthalpy and Heat Capacity

I'm a little confused on what is the difference between enthalpy and heat capacity. Can someone explain to me what the differences are, and what would be the ideal temperature unit to use for them?
Mon Jan 28, 2019 5:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpies
Replies: 2
Views: 116

### Standard Enthalpies

Do standard enthalpies only apply for gases? Is it like equilibrium, where any solid or liquid molecule in a chemical equation is ignored? Is it the same reason as equilibrium?
Tue Jan 22, 2019 12:31 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 12.79 6th Edition
Replies: 1
Views: 84

### 12.79 6th Edition

In the 6th Edition textbook problem 12.79, they give us a strong acid as the starting molecule. Due to the fact that it is a strong acid am I suppose to assume that because it can fully disassociate I will have to the ICE Table on the second ionization equation? Also when I am solving for the initia...
Tue Jan 22, 2019 12:25 am
Forum: Ideal Gases
Topic: ICE Table Values
Replies: 9
Views: 473

### ICE Table Values

What type of values can the ICE Table calculate? I know the ideal "units" is concentration, but I was also told that you can do moles and just divide everything by the volume after. I also know that you can use bars in the ICE Table, so is there any sort of value or measurement that we sho...
Tue Jan 22, 2019 12:18 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Deprotonation
Replies: 1
Views: 81

### Re: Deprotonation

Deprotonation is when you add water to any molecule in a chemical equation and the product becomes H+/H3O+ with the conjugate base. When you solve for percent deprotonation, it is the concentration of the H+/H3O+ divided by the initial (given) concentration multiplied by 100%.

I hope this helps.
Tue Jan 15, 2019 5:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and liquids in equilibrium constants?
Replies: 2
Views: 76

### Re: Solids and liquids in equilibrium constants?

You don't use solid or liquids when calculating the equilibrium constant because solids and liquids are pure. They do not have a concentration, and if they do not have a concentration then they are not included in the calculations for K and Q.
Tue Jan 15, 2019 5:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Temperature
Replies: 3
Views: 103

### Temperature

When solving equilibrium problems is there a preferred temperature unit we should be using? I noticed in some homework problems that they use Kelvin and Celcius, should we be converting one of them or does it not matter?
Tue Jan 15, 2019 5:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Replies: 3
Views: 163

In the 6th Edition textbook problem 11.39, the problem gives the reaction 2BrCl(g) + H2(g) \rightleftharpoons Br2(g) + 2HCl(g) and hints for us to use Table 11.2 for help. From there I noticed we had to add two different equations to form the given reaction. How exactly do you add the two equations ...
Thu Jan 10, 2019 3:32 pm
Forum: Ideal Gases
Topic: Reaction Quotient
Replies: 6
Views: 208

### Reaction Quotient

Why is it that when solving for Q, the reaction quotient, we disregard the solids and the liquids in the chemical equation? I think we disregard solids because it isn’t possible to find the concentration of a solid but why do we disregard liquids?
Thu Jan 10, 2019 3:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K, Kc and Kp
Replies: 8
Views: 205

### Re: K, Kc and Kp

K is also known to be the composition of the reaction mixture at equilibrium at a given temperature. Kc is used for substances with concentration (Aqueous and or if there is more than one form in the chemical equation), and Kp is used for partial pressures that have gaseous compounds.
Wed Jan 09, 2019 6:37 pm
Forum: Ideal Gases
Topic: Reaction Quotient
Replies: 4
Views: 171

### Reaction Quotient

What is the reaction Quotient and how does one solve for that? For example in the 6th edition textbook, problem number 13a, how would you solve for that problem?
Thu Dec 06, 2018 10:07 pm
Forum: Amphoteric Compounds
Topic: Determining Amphoteric Compounds
Replies: 3
Views: 145

### Determining Amphoteric Compounds

Is the only way you can determine if a compound is amphoteric is if it is located near that diagonal band of metalloids?
Sun Dec 02, 2018 6:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentates
Replies: 1
Views: 106

### Polydentates

How do I determine if a ligand is polydentate? Is the only method drawing out the ion? In the 6th edition #17.33 why is [CO3](2-) only able to have 1-2 bonding sites, I thought a bonding was possible as long as there were lone pairs?

Why is water always a monodentate ligand?
Sun Dec 02, 2018 5:37 pm
Forum: Naming
Topic: 6th Edition Ch 17.5 #31 b and d
Replies: 1
Views: 97

### 6th Edition Ch 17.5 #31 b and d

So for 31b the name is "pentaamminesulfatocobalt(III)" which the solution manual gives [Co(NH3)5(SO4)]Cl what happened to the 3? Does it go to Cobalt or Chloride? I had the same issue with part d which is "sodium bisoxalato(diaqua)ferrate(III)" and the solution manual gives Na[Fe...
Thu Nov 29, 2018 10:12 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Simpler Terms
Replies: 4
Views: 415

### Simpler Terms

Can someone explain in simpler terms what diamagnetism and paramagnetism is? The book definition is a little confusing. Thanks!
Thu Nov 29, 2018 9:43 pm
Forum: Bond Lengths & Energies
Topic: 6th Edition #89 b
Replies: 1
Views: 310

### 6th Edition #89 b

What does the solution manual mean when it states "However, because C atom is involved in a double bond and the N single bond radius gives 142pm, which is close to the experimental value of 133pm"? I thought the bond length for CN would just be 77pm +75pm=152pm. Why does it suddenly talk a...
Thu Nov 29, 2018 9:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole moment
Replies: 7
Views: 375

### Dipole moment

How do you determine when the largest dipole moment is for a molecule?
Thu Nov 22, 2018 9:10 pm
Forum: Hybridization
Topic: Writing Pi Bonds
Replies: 2
Views: 145

### Writing Pi Bonds

How do you write pi bonds on the molecule? I understand how to identify them, but I don't understand how to write the composition of the bond and the hybridization of a pi bond? For example on problem #95 (in the 6th edition chapter 4), in part b the problems asks that you write the composition of t...
Thu Nov 22, 2018 9:05 pm
Forum: Hybridization
Topic: HW Problem #81
Replies: 1
Views: 34

### HW Problem #81

In the 6th Edition of the Chemical Principles book the textbook draws a Lewis Structure that gives Boron a double bond with Nitorgen when it does that doesn't it give Boron a -1 charge? But the initial molecule does not have a charge so shouldn't we just draw a lone pair on each Nitrogen? Does this ...
Thu Nov 22, 2018 9:00 pm
Forum: Hybridization
Topic: HW Problem 43
Replies: 1
Views: 98

### HW Problem 43

In the 6th Edition of the Chemical Principles Textbook, the question states "Noting that the bond angles of an sp3 hybridization atom is 109.5 degrees and that of an sp2 hybridization atom of 120 degrees, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-...
Tue Nov 13, 2018 2:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Rule 3 of the VSPER model
Replies: 1
Views: 96

### Rule 3 of the VSPER model

Can someone describe in simpler terms what rule 3 is talking about? The textbook says, "All regions of high electron density, lone pairs, and bonds, are included in a description of the electronic arrangement, but only the positions of atoms are considered when identifying the shape of a molecu...
Tue Nov 13, 2018 2:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Rule 2 of VSEPR Model
Replies: 2
Views: 120

### Rule 2 of VSEPR Model

In the textbook rule 2 states, "There is no distinction between single and multiple bonds: a multiple bond is treated as a single region of high electron concentration." What exactly does it mean? Does that mean a single bond is simply a region with lower electron concentration? Does the e...
Tue Nov 13, 2018 2:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Names and Shapes of molecules
Replies: 2
Views: 57

### Names and Shapes of molecules

How many names and shapes of molecules are we expected to know? Are we expected to memorize these?
Thu Nov 08, 2018 9:51 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Distortion and Polarization
Replies: 3
Views: 367

### Distortion and Polarization

Can someone explain in simple terms what is distortion and how it affects polarization? Also, could you define polarization in simple terms? Thanks!
Thu Nov 08, 2018 9:45 pm
Forum: Bond Lengths & Energies
Topic: Dipole Moment Units
Replies: 3
Views: 203

### Dipole Moment Units

What are the units used for Dipole Moment? I know the equation is dipole moment (mu) = charge (q) x distance between atoms (bond length) [d], but what exactly does this measure and what units are each variable?
Thu Nov 08, 2018 9:39 pm
Forum: Ionic & Covalent Bonds
Topic: Dipole and Dipole Moments
Replies: 2
Views: 147

### Dipole and Dipole Moments

Can someone explain in simple terms what exactly does dipole mean and what is a dipole moment?
Fri Nov 02, 2018 3:48 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Valence Electrons in the d-orbitals
Replies: 2
Views: 151

### Valence Electrons in the d-orbitals

How do you know how many valence electrons are in the d orbitals, since 4s2 is technically the "outer most" orbital? Would all d orbital elements be either one or two depending on 4s? Or do we add the d orbital and the s orbital together? For example, would Iron (Fe) have six valence elect...
Wed Oct 31, 2018 11:45 am
Forum: Formal Charge and Oxidation Numbers
Topic: Stable Condition
Replies: 8
Views: 1998

### Re: Stable Condition

Thanks for answering the second part! But for the first part I was confused on the example he gave for sulfate, (SO4)2-. I know that sulfate has a negative charge of 2 electrons, so I thought the most stable condition would be when the Formal Charge equals minus 2. Or is it when it equals 0? I remem...
Wed Oct 31, 2018 11:40 am
Forum: Formal Charge and Oxidation Numbers
Topic: Formal CHarge
Replies: 5
Views: 241

### Formal CHarge

An atom or molecule is the most stable when the formal charge of the lowest ionization energy atom is 0? Or does the whole entire molecule have to equal 0? Is it safe to only check the lowest ionization energy atom is zero (when determining if it is in a stable state) or should I check each individu...
Mon Oct 29, 2018 11:05 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Stable Condition
Replies: 8
Views: 1998

### Stable Condition

I am a bit confused about the stable condition and the equation used to calculate it. Is a molecule or atom the most stable when it's Lewis Structure is equal to zero or is it the most stable when it is equal to the charge? Like for [SO4]2-, is the molecule most stable when the Lewis Structure is eq...
Wed Oct 24, 2018 10:31 pm
Forum: Trends in The Periodic Table
Replies: 4
Views: 205

Could someone explain why there isn't a trend for covalent radius?
Sat Oct 20, 2018 10:10 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Effective Nuclear Charge
Replies: 3
Views: 174

### Effective Nuclear Charge

What exactly is Z and how does it come into play for the effective nuclear charge? The equation given is En= - Z^2 eff hR/n^2, can someone explain what this equation is used for and what it means?
Sat Oct 20, 2018 10:03 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Alternate names of n, l, ml, and ms
Replies: 2
Views: 401

### Alternate names of n, l, ml, and ms

In professor's Lavelle's lecture he stated that n= energy and size aka shell, l= shape aka angular momentum, ml= orientation aka magnetic quantum, and ms= magnetic spin, but are there alternative names? I was reading some of the textbook problems, and they ask for subshells or principle quantum numb...
Fri Oct 19, 2018 11:27 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: d- orbitals
Replies: 2
Views: 151

### d- orbitals

For the p-orbital there are the px, py, and pz atomic orbitals, but what are the five different orbitals for the d-orbital? What about the f-orbital? Do we only need to know the p atomic orbitals or do we need to know all of them to some extent?
Tue Oct 16, 2018 3:14 pm
Forum: *Shrodinger Equation
Topic: Schrodinger Equation
Replies: 3
Views: 299

### Schrodinger Equation

What are the units used for Schrodinger's Equation and what information is needed in order to solve for it?
Tue Oct 16, 2018 3:01 pm
Forum: Properties of Electrons
Topic: Stefan-Boltzmann law
Replies: 1
Views: 127

### Stefan-Boltzmann law

What exactly is the Stefan-Boltzmann law, when should one use it, and how does one use it?
Fri Oct 12, 2018 3:46 pm
Forum: Balancing Chemical Reactions
Topic: L39, TB 6th Edition
Replies: 1
Views: 282

### Re: L39, TB 6th Edition

The question is " A 1.50-g sample of metallic tin was placed in 26.45-g crucible and heated until all copper had reacted with the oxygen in air to form oxide. The crucible and product together were found to weight 28.35g. (a) What is the empirical formula of the oxide? (b) Write the name of the...
Fri Oct 12, 2018 3:31 pm
Forum: DeBroglie Equation
Topic: Negative Energy?
Replies: 2
Views: 90

### Negative Energy?

Is there such a thing as negative energy? Why is it that during the lecture today when delta E= -4.09 x 10^19 J, we discarded the negative when plugging in delta E into De Broglie Equation?
Fri Oct 12, 2018 3:25 pm
Forum: DeBroglie Equation
Topic: Week 3 Textbook Assignment
Replies: 2
Views: 75

### Re: Week 3 Textbook Assignment

My TA said you could do any 7 problems from any of the assigned problems on the syllabus, but it would be best to follow what Professor Lavelle had just lectured on.
Fri Oct 12, 2018 3:20 pm
Forum: Properties of Light
Topic: Work Function
Replies: 2
Views: 64

### Work Function

If not given the work function, how do I calculate for that? What information is needed in order to calculate the work function if not given?
Thu Oct 11, 2018 6:59 pm
Forum: Empirical & Molecular Formulas
Topic: Rounding for limiting reactants
Replies: 5
Views: 326

### Rounding for limiting reactants

When calculating for the empirical formula, you must first calculate for the limiting reactant. The part I am confused on is how do you know what number to multiply by when your number isn't whole? For example, if you have 100 grams of H2O and you divide by 18g/mol of H2O (the molar mass) your final...
Thu Oct 11, 2018 11:08 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Naming Simple Coumpounds
Replies: 2
Views: 262

### Naming Simple Coumpounds

Can someone please explain how naming simple compounds work? I'm a bit confused when to use -ate, -ide, -ous, -ic, and -ite. Do we have to memorize these?