Search found 102 matches
- Sat Mar 13, 2021 5:55 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: How to find delta H of fusion
- Replies: 5
- Views: 413
How to find delta H of fusion
Is there a formula to find the delta H of fusion or is it calculated through q=mC△T and other similar formulas? In the specific problem I am working with, you are given amount of heat absorbed, mass, and T(initial).
- Fri Mar 12, 2021 9:39 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Relating delta T to volume/molarity
- Replies: 2
- Views: 343
Re: Relating delta T to volume/molarity
OH, that makes so much sense! Thank you for your helpful explanation!
- Fri Mar 12, 2021 8:48 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Relating delta T to volume/molarity
- Replies: 2
- Views: 343
Relating delta T to volume/molarity
For one of the questions on Michael's week 4 worksheet, the question asks Which combination of solutions of HCl and NaOH will produce the largest ΔT? The answer options were a combination of volume and molarity, like 50 mL of 1 M HCl with 50 mL of 1 M NaOH. How do we find a change in temperature whe...
- Fri Mar 12, 2021 12:05 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: When to split molecules into their ions for Kc
- Replies: 1
- Views: 216
When to split molecules into their ions for Kc
When solving for Kc from an equation, sometimes we are supposed to break a molecule down into its ions. For example, in Pb(No3)2 (aq) + 2KCl (aq) --> PbCl2 (s) + 2 KNO3 (aq), the equilibrium constant is 1/[Pb2+][Cl-]^2. How do we know when to break into ions or to just leave the molecules as is?
- Tue Mar 09, 2021 5:36 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook 6L.9
- Replies: 1
- Views: 148
Textbook 6L.9
I am very confused as to how the reduction and oxidation reactions were formed from the question just telling us that it was "an acidified solution of potassium permanganate and iron(II) chloride." The answer key did not use potassium or chloride in the balanced equation for the cell react...
- Mon Mar 08, 2021 5:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Understanding the galvanic cell of 6L question 3
- Replies: 2
- Views: 169
Understanding the galvanic cell of 6L question 3
Hi, I do not know how to begin writing the redox reactions for this problem. We are given O2 and H+ on one side of the double lines, and O2 and OH- on the other side. I tried to balance those reactions but it was completely different from what the back of the book said. How are we supposed to write ...
- Mon Mar 08, 2021 5:10 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 6L.1
- Replies: 4
- Views: 308
Re: 6L.1
In 6L.1 part b, I got that Cr lost three electrons and Fe gained one, meaning that n should be three, but the answer key says n is six. Since it is Cr and Cr2O7, does multiplying the Cr by 2 mean that you have to multiply the number of electrons by 2?
- Mon Mar 08, 2021 12:45 pm
- Forum: Balancing Redox Reactions
- Topic: Textbook Problem 6K.5
- Replies: 3
- Views: 221
Re: Textbook Problem 6K.5
How is O3 --> O2 an oxidation or reduction? I thought that elements standing alone/diatomics alone had an oxidation # of zero.
- Mon Mar 08, 2021 12:23 pm
- Forum: Balancing Redox Reactions
- Topic: Textbook Problem 6K.5
- Replies: 3
- Views: 221
Re: Textbook Problem 6K.5
I also am very confused on this one. I was able to get a redox and an oxidation reaction, but then I had an O2 left over. I tried just adding it on at the end, and everything balanced correctly but it was different than the answer in the book. The book got two separate equations, which I do not even...
- Sun Mar 07, 2021 1:11 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Rate Laws and Elementary Steps
- Replies: 4
- Views: 248
Re: Rate Laws and Elementary Steps
I believe that sounds correct, and another important thing to think about is that intermediates could be in the elementary reaction(s). These do not show up in the final reaction but are important molecules because they are involved in collisions that eventually lead to product formation.
- Sun Mar 07, 2021 1:07 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: First order reactions
- Replies: 3
- Views: 238
Re: First order reactions
Emily posted a great explanation, but I also wanted to add that order is for exponents and molecularity is for number of reactants. A unimolecular reaction is A --> P for example, but a bimolecular reaction is A+B-->P. A and B both have a reaction order of 1, but the first reaction is uni and the se...
- Sun Mar 07, 2021 1:04 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Rate Laws
- Replies: 7
- Views: 439
Re: Rate Laws
I think it will depend on the type of question asked, but if we are just given a chemical equation we should not have to determine the rate law from that. If we are given k and each elementary step then we will be able to determine rate law, but k is determined experimentally too.
- Sun Mar 07, 2021 1:01 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Determining k when concentration is changed
- Replies: 3
- Views: 259
Determining k when concentration is changed
Say you have a rate law that = k[A][B]^2 and the initial rate is 0.34 M/s. If A is doubled and B is halved, what would the initial rate be? Could someone explain the steps you would use to figure out the rate when concentrations are shifted?
- Sun Feb 28, 2021 3:19 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Sapling Q15 week 7/8
- Replies: 3
- Views: 231
Re: Sapling Q15 week 7/8
I discovered that I was dividing the ln value instead of multiplying it, so it was a calculation error! Thank you so much for your feedback.
- Thu Feb 25, 2021 12:59 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Sapling Q15 week 7/8
- Replies: 3
- Views: 231
Sapling Q15 week 7/8
For #15 on this week's Sapling homework, it keeps telling me that my answer is wrong because I need to convert my temperature into kelvin, but I did that and I do not see where else there is an issue. The question is: Calculate the cell potential for the reaction as written at 25.00 °C, given that [...
- Thu Feb 25, 2021 12:40 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: difference between E and Eº
- Replies: 7
- Views: 507
difference between E and Eº
On the equation sheet, one equation is E = Eº - (RT/nF)lnQ, and another is Eº = (RT/nF)link. What is the difference between E and Eº, and how do you determine which one to use? Thanks so much in advance :)
- Thu Feb 18, 2021 9:37 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Cv and Cp values for an ideal gas
- Replies: 4
- Views: 942
Re: Cv and Cp values for an ideal gas
replying to myself haha but I went to a drop in session today and the UA said that for diatomic molecules you have to add another R because there are two ideal gas atoms in a diatomic. So instead of Cv= (3/2)R, the diatomic molar heat capacity is Cv= (3/2)R+ (2/2)R which equals 5/2R. Hopefully I exp...
- Thu Feb 18, 2021 3:16 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Cv and Cp values for an ideal gas
- Replies: 4
- Views: 942
Re: Cv and Cp values for an ideal gas
How do we know what the Cv and Cp for diatomic molecules are? In the "errors in the solution manual" part on Dr. Lavelle's website, he says for 4F.11 that the Cv of a diatomic ideal gas is (5/2)R when the Cv of a monatomic gas is (3/2)R. How is the diatomic value derived?
- Thu Feb 18, 2021 2:30 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Stability and delta G
- Replies: 1
- Views: 133
Stability and delta G
As I was working through the book problems, I found in one of the answer key explanations that a negative delta G means that a compound is stable (4J.13). Since a negative delta G is spontaneous, I thought that meant that the compound would be unstable because it reacts easier with other elements. C...
- Wed Feb 17, 2021 5:55 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Textbook #4J.7A
- Replies: 2
- Views: 170
Textbook #4J.7A
In the textbook for problem 4J.7 part a) we are asked to find standard reaction entropy, enthalpy, and Gibbs free energy of the decomposition of H202, or 2 H202 --> 2 H20 + O2. I thought that if we were finding standard values we had to reduce the equation to one mole, i.e. H202 --> H20 + 1/2 02. Ho...
- Wed Feb 17, 2021 5:49 pm
- Forum: Calculating Work of Expansion
- Topic: Textbook Focus problem 4I.9B
- Replies: 2
- Views: 100
Re: Textbook Focus problem 4I.9B
That makes a lot of sense, thank you Emily! I get confused about the expansion/work relationship, but your explanation was very helpful!
- Wed Feb 17, 2021 4:47 pm
- Forum: Calculating Work of Expansion
- Topic: Textbook Focus problem 4I.9B
- Replies: 2
- Views: 100
Textbook Focus problem 4I.9B
In the textbook, for focus problem 4I.9 part b), it asks to find delta S sys, surr, and total of an isothermal, irreversible expansion. The explanation on the answer key talks about U, w, and q, describing internal energy. Do we always look towards internal energy when an irreversible expansion is g...
- Wed Feb 17, 2021 4:09 pm
- Forum: Phase Changes & Related Calculations
- Topic: difference between Cp and molar heat capacity
- Replies: 2
- Views: 250
difference between Cp and molar heat capacity
On the constants and equations sheet, there is molar heat capacity of water (liquid) and Cp listed as two separate values. They are basically the same number with the same units, one is just rounded up, but I wanted to make sure there was no difference between the two. Cp is just the symbol for mola...
- Thu Feb 11, 2021 8:27 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Focus 4 Exercise 15
- Replies: 4
- Views: 290
Re: Focus 4 Exercise 15
I struggled with this problem because I did not know that we were able to look up the enthalpies of formation. I was trying to figure out the calculations but came to a standstill because I felt that information was lacking, but did not know specifically what information. What was the key wording in...
- Wed Feb 10, 2021 12:34 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Relating Internal Energy and Spontaneity
- Replies: 4
- Views: 426
Relating Internal Energy and Spontaneity
Hi, Would anyone be able to explain how internal energy (delta U) and spontaneity (deltaH/delta S) relate? Does the sign (+ or -) or internal energy tell if a reaction is spontaneous, or are there other factors that are involved? If there is a different relationship between the two please let me kno...
- Tue Feb 09, 2021 9:18 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Sapling question #3 week 5/6
- Replies: 2
- Views: 124
Sapling question #3 week 5/6
For the 3rd question in sapling for weeks 5/6, it asks to classify the phase changes by the signs of the system's ΔH and S. I do not understand how gas to liquid vs liquid to solid would have different entropies. If it is endothermic, I thought it would always be negative delta S because putting ene...
- Sat Feb 06, 2021 4:08 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible Expansion
- Replies: 7
- Views: 267
Re: Reversible Expansion
Could someone explain the definition of reversible expansion? Does it just mean that the volume or pressure is constant?
- Wed Feb 03, 2021 7:50 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Sapling Learning Week 3 and 4 Homework Question 18
- Replies: 2
- Views: 139
Re: Sapling Learning Week 3 and 4 Homework Question 18
Shanna, thank you for the great explanation! At the end, I was wondering why you have to do Cv-R (or 4R-R) instead of just 4R? Why do we need to subtract one R?
- Wed Feb 03, 2021 7:03 pm
- Forum: Calculating Work of Expansion
- Topic: Sapling Week 3&4 HW #14
- Replies: 4
- Views: 214
Re: Sapling Week 3&4 HW #14
How do you know whether you use the initial or final V and P? I have used the same formula and ideas as Olivia so I was wondering how you know which V and P values to use.
- Sun Jan 31, 2021 7:01 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5J.5 d
- Replies: 6
- Views: 528
Re: 5J.5 d
The correct answer is that it does not shift to either side! Since the moles are equal, the equilibrium does not shift at all and the molar quantities/pressure stays the same. This is if you use the correct equation, 2HD <-> H2 + D2. The one written in the book, 2HD(g) + H2(g) <—> D2(g), is not comp...
- Wed Jan 27, 2021 4:04 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: How Kc and heat relate
- Replies: 1
- Views: 87
How Kc and heat relate
If you add heat to a reaction and are not given whether the reaction is endothermic or exothermic, how do you know if the equilibrium will shift to the right or to the left? In book problem 5J.13, We were given two Kc's for the same reaction, one at 600K and one at 700K. The Kc for the 600K was high...
- Wed Jan 27, 2021 3:39 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5J.5 d
- Replies: 6
- Views: 528
Re: 5J.5 d
On Dr. Lavelle's website, he has a section titled Errors in the Solution Manual of the 7th edition, and 5J.5 d) is one of them! Katarina is correct about what the equation is supposed to look like. Therefore, there would be no shift in equilibrium because there are two moles on each side.
- Tue Jan 26, 2021 8:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook problem 5G.3
- Replies: 2
- Views: 64
Re: Textbook problem 5G.3
Wow that is sad I did not know that haha. That clears up so much thank you!!!
- Tue Jan 26, 2021 12:30 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook problem 5G.3
- Replies: 2
- Views: 64
Textbook problem 5G.3
Hi! For this problem in the book, we are asked to write an expression of K for two different reactions. In the answer key, it gives us the partial pressures instead of concentration. Is this a book mistake or were we somehow supposed to know that they were asking for partial pressures? The exact wor...
- Sun Jan 24, 2021 1:58 pm
- Forum: Phase Changes & Related Calculations
- Topic: sapling weeks 3-4 #4
- Replies: 6
- Views: 226
Re: sapling weeks 3-4 #4
How does this work with individual elements? When A combines with B to make AB for example, isn't that always exothermic because a bond is being formed?
- Sun Jan 24, 2021 12:18 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: figuring out whether salts are acidic or basic
- Replies: 4
- Views: 185
figuring out whether salts are acidic or basic
If a salt has a strong base cation such as K3PO4, the salt is basic because it pulls H+ from the water. What does it mean to pull H+?
- Sun Jan 24, 2021 11:50 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: what does formal concentration mean
- Replies: 3
- Views: 558
Re: what does formal concentration mean
Oh, that makes much more sense! Thank you for your in depth explanation. In the problem, when they gave us the pH, that means that the [H+] is the equilibrium concentration correct?
- Sun Jan 24, 2021 11:48 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: reaction enthalpy of O2
- Replies: 4
- Views: 657
Re: reaction enthalpy of O2
Hi! I believe that Dr. Lavelle stated the standard enthalpy of formation for O2 is zero, not the bond enthalpy. I think that the bond enthalpy of O2 is 498 kJ/mol, but if you meant to ask about the standard enthalpy of formation instead of the bond enthalpy, then Jay explains it well above. Hope th...
- Fri Jan 22, 2021 5:05 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: what does formal concentration mean
- Replies: 3
- Views: 558
what does formal concentration mean
In week 2 sapling question 5, to find the pronated percentage we had to calculate formal concentration by adding the concentration of the amine (reactant) and its acidic form (product). This was the denominator, and the concentration of the acidic form was the numerator. I do not understand why we h...
- Fri Jan 22, 2021 3:48 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: reaction enthalpy of O2
- Replies: 4
- Views: 657
reaction enthalpy of O2
In the Friday lecture, Dr. Lavelle said that the bond enthalpy of O2 was zero. He also said that diatomic bond enthalpies are extremely accurate, so I was wondering when you know that the diatomic has a bond enthalpy of zero or the exact calculated value. Or is this instance just particular to O2?
- Fri Jan 22, 2021 3:46 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies of diatomics vs Bond Enthalpies of Everything else
- Replies: 2
- Views: 87
Re: Bond Enthalpies of diatomics vs Bond Enthalpies of Everything else
Diatomics are always the same in reactions because it is just the two elements bonded with each other with the same amount of electrons, bond angles, etc. every time. The other bond enthalpies are averages because a C-H bond in a CH4 molecule will have an ever so slight different bond enthalpy than ...
- Fri Jan 22, 2021 3:42 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: standard enthalpy terminology clarification
- Replies: 2
- Views: 169
Re: standard enthalpy terminology clarification
Yes, standard enthalpy of formation is just in kJ/mol. The important part is the units, knowing that it represent the formation of ONE mole of a substance. Both are the most stable states of molecules in their standard phases. I do not think we will ever be asked to calculate standard rxn enthalpy s...
- Fri Jan 22, 2021 3:02 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: method 2 in lecture
- Replies: 4
- Views: 121
Re: method 2 in lecture
As a follow-up to my last post, did he leave out the 4 C-H bonds on the left because they cancel out with the 4 C-H bonds on the right? In this case, since there are 5 total on the right, I believe that would mean that you only need to calculate the bond enthalpy for one C-H bond. If someone could v...
- Fri Jan 22, 2021 3:00 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: method 2 in lecture
- Replies: 4
- Views: 121
Re: method 2 in lecture
In the example he used for method 2, he calculated the bond enthalpy of a C=C bond but not the 4 C-H bonds in the CH2=CH2 molecule. Why would you not include those bond enthalpies? Aren't those bonds still broken?
- Thu Jan 21, 2021 8:48 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Ka vs. Kb
- Replies: 30
- Views: 4916
Re: Ka vs. Kb
If NH3 reacts with water to form NH4+ and OH-, would you use Kb because OH- is produced?
- Thu Jan 21, 2021 8:46 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Week 2 Sapling #5
- Replies: 9
- Views: 249
Re: Week 2 Sapling #5
How would you set up this equation? I tried both times once disregarding x and once without and did not get the correct answer either time. Do you need to switch Kb to Ka?
- Thu Jan 21, 2021 8:41 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: What is Qp?
- Replies: 5
- Views: 283
What is Qp?
In the 1/20 lecture, Dr. Lavelle said that Qp = delta H. I am familiar with delta H but get confused about the Q. In equilibrium, Q is an equilibrium constant and P normally represents pressure but I am guessing it is used differently here. If someone could explain what Qp is in the context of entha...
- Tue Jan 12, 2021 8:00 pm
- Forum: Ideal Gases
- Topic: Inert Gases
- Replies: 7
- Views: 315
Re: Inert Gases
Why are inert gases only noble gases? Is there a reason these noble gases are the only type of gases that go through the equations where inert gases are present? I am a bit confused. It is only inert/noble gases that do not change the equilibrium based on Anna's explanation. Any other gas that is p...
- Sun Jan 10, 2021 10:24 pm
- Forum: Ideal Gases
- Topic: Equation Constant
- Replies: 5
- Views: 183
Re: Equation Constant
The gas constant is R in the equation PV=nRT. PV is proportional to nT because a change in one affects the other. If P goes up, nT goes down. The R constant is necessary because it allows you to solve for an unknown value, rather than just having the ratios. R changes depending on the units of the p...
- Sun Jan 10, 2021 10:16 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: relationship between reaction, product, and K
- Replies: 7
- Views: 222
Re: relationship between reaction, product, and K
To expand on this idea, the total K can be found by adding individual, smaller reactions together to get the correct reactants/products, and the K from each reaction is multiplied to get the equilibrium constant for the final equation. If you have to switch a reaction around, you would use 1/K for t...
- Sun Jan 10, 2021 10:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Getting a negative during quadratic
- Replies: 5
- Views: 215
Getting a negative during quadratic
For one of the sapling problems, I got a negative number inside of the square root, which usually means the problem has no real solutions. However, I decided to try and keep going, and the answer that I got using that imaginary number worked for the problem. I do not understand how this is possible,...
- Sat Jan 09, 2021 11:07 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: endothermic v endergonic
- Replies: 4
- Views: 244
endothermic v endergonic
In Dr. Lavelle's lecture, he mentioned both the terms endothermic and endergonic. I thought that they can be used interchangeably, but I do not know for sure. Do they mean the same thing or should they be used differently?
- Fri Dec 11, 2020 9:00 pm
- Forum: Naming
- Topic: identifying polydentate compounds
- Replies: 3
- Views: 157
Re: identifying polydentate compounds
This is all really helpful info, thank you so much! As a follow up to that, why is water not bidentate? It has two lone pairs on the oxygen, so shouldn't that mean that it could bond to a metal atom in two different places?
- Fri Dec 11, 2020 8:39 pm
- Forum: Naming
- Topic: identifying polydentate compounds
- Replies: 3
- Views: 157
identifying polydentate compounds
If we are given a compound like H2SO4 or something and asked whether it is mono dentate or polydentate, how would you figure that out? I thought that it would be polydentate if it was the lone pair-spacer atom structure that Dr. Lavelle discussed, but then I learned that (CO3)^2- is polydentate and ...
- Fri Dec 11, 2020 8:00 pm
- Forum: Naming
- Topic: Topic 9C Exercises Question 3
- Replies: 4
- Views: 218
Re: Topic 9C Exercises Question 3
Why is there no net negative charge since the compound ends in -ate (chromate)? I thought that if it ended with this suffix then the compound needed to have an overall negative charge.
- Fri Dec 11, 2020 10:42 am
- Forum: Einstein Equation
- Topic: units for E=hv
- Replies: 21
- Views: 1078
units for E=hv
Hi! When calculating E=hv, how do yo9u know if it is in J/photon or J/atom? I was doing some hw problems (1B #7 and 9) and one was in J/atom and the other was in J/photon, so I was wondering why you can do this and how to tell when to use which set of units.
- Mon Dec 07, 2020 11:34 am
- Forum: Calculating the pH of Salt Solutions
- Topic: explanation of 10^-14
- Replies: 3
- Views: 192
explanation of 10^-14
In Dr. Lavelle's Friday lecture, I was a bit confused on what 10^-14 M represented. He said that all compounds must equal this value in terms of balancing pH? I don't really know what this means. If someone could explain that would be great!
- Sun Dec 06, 2020 11:00 pm
- Forum: Coordinate Covalent Bonds
- Topic: General Question on Coordinate Covalent Bonds
- Replies: 8
- Views: 594
Re: General Question on Coordinate Covalent Bonds
Are Lewis acids and Lewis bases the only ones involved in coordinate covalent bonding, or is it any transition metal and ligand?
- Sun Dec 06, 2020 10:58 pm
- Forum: Coordinate Covalent Bonds
- Topic: Coordination Compounds vs Ionic Compounds
- Replies: 2
- Views: 296
Re: Coordination Compounds vs Ionic Compounds
Transition metals are more likely to form bonds than group one and two cations because they reside in the d block. This means that they have more orbitals that are empty and could potentially be filled by the ligands. This property also means that they can accept lone pairs. Looking at where they li...
- Sun Dec 06, 2020 10:54 pm
- Forum: Bronsted Acids & Bases
- Topic: Strong & Weak Acid
- Replies: 6
- Views: 201
Re: Strong & Weak Acid
Do longer bonds mean that the acids are stronger because they can dissociate more easily? If this is true, does this logic also apply for strong bases?
- Thu Dec 03, 2020 10:37 pm
- Forum: Coordinate Covalent Bonds
- Topic: H3O+ explanation
- Replies: 4
- Views: 327
H3O+ explanation
If H+(aq) is "code" for H3O+, then would you need to write H3O+(aq) because that coordination compound is also in water? or would you omit the state of matter because it is technically including it in the compound?
- Thu Dec 03, 2020 10:34 pm
- Forum: Coordinate Covalent Bonds
- Topic: Hydrogen bonding
- Replies: 15
- Views: 822
Re: Hydrogen bonding
I am confused because in lecture, Dr. Lavelle said that HCl in H2O would mean that the H and the O in two separate compounds would interact with each other as a coordinate covalent bond, when I thought that this would be considered hydrogen bonding. Does anyone have an explanation as to why this is ...
- Sun Nov 29, 2020 7:39 pm
- Forum: Lewis Structures
- Topic: Expanded Valence Shells
- Replies: 7
- Views: 453
Re: Expanded Valence Shells
What is the reason that p-block elements can have an expanded valence shell? Why do elements with an atomic number >20 want more electrons?
- Sun Nov 29, 2020 7:37 pm
- Forum: Coordinate Covalent Bonds
- Topic: Do C.C. bonds have expanded octet?
- Replies: 3
- Views: 202
Do C.C. bonds have expanded octet?
In all the examples provided so far, it seems that coordinate covalent bonds with transition metals always form expanded octets. Is this because transition metals are in the d-block on the periodic table, or is it because their "sea of electrons" nature means that it is easier for them to ...
- Sun Nov 29, 2020 7:24 pm
- Forum: Coordinate Covalent Bonds
- Topic: Polarity of Ni(NH3)4Cl2
- Replies: 2
- Views: 407
Polarity of Ni(NH3)4Cl2
Hi, I was going through Dr. Lavelle's Wednesday lecture and was trying to figure out the polarity of Ni(NH3)4Cl2 (octrahedral shape) and thought that it would be non-polar because the NH3 dipoles would cancel from the 90° equatorial positions and the Cl dipoles would cancel from the 180° axial posit...
- Tue Nov 24, 2020 10:19 pm
- Forum: Dipole Moments
- Topic: higher dipole moment sapling #10
- Replies: 5
- Views: 1204
Re: higher dipole moment sapling #10
Also for this question, how do you determine which atom is the "negative pole"? I don't get how the negative pole can be between two atoms. I thought it would be towards O since O has two lone pairs, meaning more negative charge.
- Tue Nov 24, 2020 9:52 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: equatorial vs. axial atom positions
- Replies: 4
- Views: 158
equatorial vs. axial atom positions
How do you identify whether an atom is at the equatorial or axial position in the VSEPR shape of trigonal bipyramidal?
- Sun Nov 22, 2020 12:54 pm
- Forum: Hybridization
- Topic: General question about hybridization
- Replies: 3
- Views: 75
Re: General question about hybridization
For example, in the sp3 orbital, does this mean that there are 4 unpaired electrons (1 in s, 3 in p)? So 4 electrons in each orbital, which is done to make the molecule more stable?
- Fri Nov 20, 2020 1:23 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: bond angle of see saw and square planar
- Replies: 2
- Views: 165
bond angle of see saw and square planar
Is the bond angle of see saw 120° and 90° or <120° and <90° because of lone pairs? Second question, is square planar all 90° angles because the lone pairs provide "even" repulsion on both sides?
- Tue Nov 17, 2020 7:30 pm
- Forum: Lewis Structures
- Topic: Textbook Problem 2B.15
- Replies: 2
- Views: 75
Re: Textbook Problem 2B.15
Even though the structure with all single bonds is unfavorable, why is it not also included as a resonance structure? Aren't resonance structures just all the possibilities of shape, whether they are favorable or not?
- Mon Nov 16, 2020 9:56 pm
- Forum: Lewis Structures
- Topic: 2B.9
- Replies: 2
- Views: 119
Re: 2B.9
I was confused on this problem too, so I will explain my thinking and hopefully that will help! To figure out the subscript, you need to know what the charge of the polyatomic ion is. I think you need to have these memorized, so for example ammonium (NH4+) has a +1 charge. Since Cl is just -1, then ...
- Sun Nov 15, 2020 10:04 pm
- Forum: Bond Lengths & Energies
- Topic: Valence electrons of nitrogen
- Replies: 10
- Views: 423
Re: Valence electrons of nitrogen
Oh, was he talking about how nitrogen wants to reach a full octet of 8 electrons when it is bonding?
- Sun Nov 15, 2020 10:02 pm
- Forum: Bond Lengths & Energies
- Topic: Valence electrons of nitrogen
- Replies: 10
- Views: 423
Valence electrons of nitrogen
In Dr. Lavelle's 11/11 lecture, he said that Nitrogen always has 8 valence electrons when he was talking about hydrogen bonding of base pairs in DNA. Doesn't nitrogen have 5 valence electrons? I was not sure if this was a mistake or if I had my information incorrect.
- Sun Nov 15, 2020 1:40 pm
- Forum: Dipole Moments
- Topic: London Dispersion forces
- Replies: 14
- Views: 509
Re: London Dispersion forces
All molecules do exhibit London dispersion forces! They exist between ionic and covalent molecules, in both polar and non polar molecules. For my sapling question at least, it was dispersion and dipole-dipole, but the answer should be one that has both unless the question asked just for the stronges...
- Tue Nov 10, 2020 11:26 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Spin state
- Replies: 25
- Views: 1215
Re: Spin state
When following Hund's rule, do the electrons in each orbital all start with an upwards spin? Or does it not really matter as long as you know that pairs go in opposite directions and each orbital must be filled before pairing
- Tue Nov 10, 2020 11:22 pm
- Forum: Resonance Structures
- Topic: Resonance structures and stability
- Replies: 4
- Views: 169
Re: Resonance structures and stability
I believe that it is also important to note that the resonance structures we draw are not a depiction of what the compound actually looks like, since the bond lengths are not specific lengths (for example, some singles and a double) but rather each bond is a length in between those two.
- Tue Nov 10, 2020 11:18 pm
- Forum: Trends in The Periodic Table
- Topic: Electron affinity and Ionization energy
- Replies: 7
- Views: 424
Re: Electron affinity and Ionization energy
Electron affinity only applies to group 18 (noble gas) elements right? Also, how exactly does an atom "give up" energy to accept an electron? Does it release energy by forming a bond with another atom?
- Tue Nov 10, 2020 11:14 pm
- Forum: Lewis Structures
- Topic: Which atom to add positive/negative charge?
- Replies: 6
- Views: 252
Re: Which atom to add positive/negative charge?
I apologize, I did not read the question closely enough! Thank you Gillian for the clarification and great explanation of formal charge.
- Tue Nov 10, 2020 11:12 pm
- Forum: Trends in The Periodic Table
- Topic: Group 14 elements
- Replies: 1
- Views: 86
Group 14 elements
Are group 14 elements +4 or -4 depending on what atom they are bonding with? I do not remember reading about these elements but as I was understanding assigning charge I realized I was unsure what to do when I got to this group.
- Sat Nov 07, 2020 4:09 pm
- Forum: Lewis Structures
- Topic: Which atom to add positive/negative charge?
- Replies: 6
- Views: 252
Re: Which atom to add positive/negative charge?
I believe that you also can determine the charge of an atom based on what column it resides in the periodic table. F is negative because it has seven valence electrons, meaning that it only wants to gain one to reach the octet. This makes is F-. Calcium has two valence electrons, so it wants to lose...
- Sat Nov 07, 2020 4:05 pm
- Forum: Ionic & Covalent Bonds
- Topic: Polarity
- Replies: 9
- Views: 451
Re: Polarity
Polarity is the partial positive and partial negative charges of a covalent bond, meaning electrons are shared unequally.
- Sat Nov 07, 2020 4:04 pm
- Forum: Ionic & Covalent Bonds
- Topic: Salts v. Ionic bonds
- Replies: 9
- Views: 284
Re: Salts v. Ionic bonds
In the converse manner, are all ionic bonds salts too? Or is it only one sided
- Sat Nov 07, 2020 3:29 pm
- Forum: Ionic & Covalent Bonds
- Topic: Salts v. Ionic bonds
- Replies: 9
- Views: 284
Salts v. Ionic bonds
In Dr. Lavelle's lecture on Friday, he said that KCl, KF, and LiF are salts with ionic bonds. Are all salts ionic bonds, or how can you tell which is a salt and which is just an ionic bond? Thanks!
- Sat Oct 31, 2020 2:19 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: h vs. ħ?
- Replies: 11
- Views: 5390
Re: h vs. ħ?
Is h-bar used in any other circumstances, or is the indeterminacy equation the only one that uses this?
- Sat Oct 31, 2020 2:17 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Using quantum numbers to find number of electrons
- Replies: 4
- Views: 364
Re: Using quantum numbers to find number of electrons
Adila, this is very helpful! Thank you for your in depth explanation!
- Sat Oct 31, 2020 2:09 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Energy Level Excited
- Replies: 8
- Views: 369
Re: Energy Level Excited
How do you correctly interpret quantum numbers to figure out the neutral state of an electron when you're given an excited state? Sapling said something about how you just count the total number of electrons of the excited state, and that is the atomic number of the neutral state. Is that correct?
- Sat Oct 31, 2020 2:04 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: explanation of ml
- Replies: 4
- Views: 187
explanation of ml
Hi! Could someone explain to me what ml is? I thought that it was the spin that an electron has but I think that might be incorrect. I also get confused how to calculate it, if for example n=2 and l=2. Thank you!
- Mon Oct 26, 2020 4:12 pm
- Forum: Properties of Electrons
- Topic: orbitals
- Replies: 3
- Views: 202
Re: orbitals
I went to the step up session on Sunday and it gave me a little more clarification on orbitals. When electrons move around their orbitals, they move so fast that they interfere with themselves and each electron creates a standing wave. Connecting the endpoints of the standing wave is what forms the ...
- Mon Oct 19, 2020 1:33 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Negative sign in En expression
- Replies: 8
- Views: 368
Re: Negative sign in En expression
Yes, that is a great explanation. Thanks so much for the clarification!
- Mon Oct 19, 2020 11:09 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg Equation and Empirical Equation
- Replies: 4
- Views: 218
Re: Rydberg Equation and Empirical Equation
For the Rydberg equation, is the energy that we get as our answer in J/photon?
- Mon Oct 19, 2020 11:02 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Negative sign in En expression
- Replies: 8
- Views: 368
Re: Negative sign in En expression
I have a follow up question to the negative sign. When solving for frequency using the change in energy just found, why do you not input the negative sign? I know frequency cannot be negative but it seems odd to me that you can just emit the negative sign when plugging it into the E=hv equation. Doe...
- Sun Oct 18, 2020 5:00 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect Module Question 28
- Replies: 9
- Views: 387
Re: Photoelectric Effect Module Question 28
OH this is a response to my last question and it might be silly but all electrons have the same mass correct? It doesn't differ based on the element?
- Sun Oct 18, 2020 4:52 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect Module Question 28
- Replies: 9
- Views: 387
Re: Photoelectric Effect Module Question 28
So in order to answer this question you had to look up the mass of an electron of sodium? I was stuck for so long because I did not think that the question gave us enough info.
- Fri Oct 16, 2020 7:25 pm
- Forum: Properties of Light
- Topic: Showing Destructive Interference?
- Replies: 5
- Views: 280
Re: Showing Destructive Interference?
I found this example that shows both constructive and destructive interference with light. It is a little convoluted but I thought it was nice to show both examples on the same plane.
- Fri Oct 16, 2020 7:22 pm
- Forum: Properties of Light
- Topic: Spectral Lines
- Replies: 11
- Views: 462
Re: Spectral Lines
I do not know if this answer if specific enough, but I think the number of lines is determined by how many electrons drop energy levels. The more electrons that emit energy, the greater number of spectral lines will be shown.
- Fri Oct 16, 2020 7:16 pm
- Forum: Properties of Light
- Topic: rydberg equation
- Replies: 7
- Views: 316
Re: rydberg equation
is the Rydberg equation just E= -(hR)/(n^2) ?
- Fri Oct 16, 2020 7:15 pm
- Forum: Properties of Light
- Topic: Balmer and Lyman series
- Replies: 7
- Views: 272
Balmer and Lyman series
Does the Lyman series just mean that the electrons fall back down to n=1 and the Balmer series just mean that electrons fall to n=2? If so, is there a way you can tell which series an atom will be a part of if you are not told which level the electron will fall down to?
- Fri Oct 16, 2020 6:13 pm
- Forum: Properties of Light
- Topic: Helium gas
- Replies: 2
- Views: 198
Helium gas
In the example at the beginning of Professor's lecture on Friday, why is there multiple colors on the EM spectrum for Helium? I thought that each element had its unique amounts of energy/unique colors that are emitted when an electron fell back down from its excited state.
- Wed Oct 14, 2020 12:56 pm
- Forum: Properties of Light
- Topic: Type of light and electron energy levels
- Replies: 3
- Views: 436
Type of light and electron energy levels
I am a little confused on how you can tell what type of light (infrared, UV), is being emitted based on how many energy levels an atom falls. In lecture, when professor was showing the n=1, n=2, n=3 etc. levels I believe he said that you can tell what type of light is emitted based on how far it jum...
- Sat Oct 10, 2020 3:10 pm
- Forum: Properties of Light
- Topic: Fireworks and Sun example
- Replies: 3
- Views: 262
Re: Fireworks and Sun example
This also can be demonstrated by an experiment that's been done in some high school chem classes. When certain metals (sodium, strontium, copper) are put into fire, the flame will turn a different color depending on the metal due to the electron jumping to a higher energy level then falling back dow...