Search found 76 matches
- Sat Mar 17, 2018 2:37 pm
- Forum: Balancing Redox Reactions
- Topic: Homework Problem 14.1
- Replies: 2
- Views: 513
Re: Homework Problem 14.1
There's 2 carbons that undergo a change in oxidation state, so you need 2 e-. I prefer to look at it as a balance of charge. You need the 2 H+ ions on the right side to balance the hydrogens, and since the left hand side is neutral and right hand side is +2, you need to add 2e- to the right hand sid...
- Mon Mar 12, 2018 11:25 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Chapter 9 #69
- Replies: 1
- Views: 359
Re: Chapter 9 #69
We multiply reaction 3 by 3 for the same reason that we multiply reaction 2 by 3. The question asks for 3 mol of NADH, so reaction 2 needs to be multiplied by 3 since the given reaction is for 1 mol of NADH. However, by multiplying by 3, the number of electrons transferred is multiplied by 3. Reacti...
- Mon Mar 12, 2018 3:51 pm
- Forum: Calculating Work of Expansion
- Topic: Practice Problem
- Replies: 1
- Views: 322
Re: Practice Problem
I think it's easier to start with part b and c b) Remember that q=moles (molar heat capacity) (delta T). You have all the information, so just substitute to find q. a/c) Delta U = q + w So all that is left is you need to solve for work since q was solved above. The work is from the volume change. In...
- Mon Mar 12, 2018 3:07 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Why is entropy extensive?
- Replies: 5
- Views: 5403
Re: Why is entropy extensive?
An extensive property is dependent on size (or mass), and like you said, entropy = q/T, and q in itself is dependent on the mass, so therefore, it is extensive. Mass is an extensive property. An example of an intensive property would be density of water. No matter how much water you have, the densit...
- Mon Mar 05, 2018 2:03 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 3 - Chapter 15 homework
- Replies: 3
- Views: 536
Re: Test 3 - Chapter 15 homework
I did problems 1-39, 83, and 99 because those are the ones without reaction mechanisms/catalysts/activation energy components.
- Mon Mar 05, 2018 1:59 pm
- Forum: First Order Reactions
- Topic: Example 15.4
- Replies: 3
- Views: 495
Re: Example 15.4
In example 15.4, they give you the experimental data of concentration versus time. To figure out if it is first order, you can take the natural log of all the concentration data on your scientific calculator and plot that data. You can also tell it's linear because the ln[concentration] decreases re...
- Sat Mar 03, 2018 10:30 pm
- Forum: First Order Reactions
- Topic: 15.37 C [ENDORSED]
- Replies: 1
- Views: 312
Re: 15.37 C [ENDORSED]
Hi! The steps you wrote are exactly what I did, but it's hard to tell where you went wrong without listing the exact numbers. Maybe you can figure out which numbers differ from mine?
Here are the #'s I got:
[A] initial = 4.15x10^-5 mol/L
[A] = e ^ -10.3 = 3.22 x 10^-5 mol/L
grams of [A] = 10.9g
Here are the #'s I got:
[A] initial = 4.15x10^-5 mol/L
[A] = e ^ -10.3 = 3.22 x 10^-5 mol/L
grams of [A] = 10.9g
- Sat Mar 03, 2018 10:25 pm
- Forum: General Rate Laws
- Topic: writing rate law
- Replies: 3
- Views: 507
Re: writing rate law
While the general reaction is definitely needed to see what's happening in the bigger picture, we specifically look at the slowest step to determine the rate law because the slowest step determines the reaction rate. In class, Dr. Lavelle used the example of baking brownies; it doesn't matter how fa...
- Thu Mar 01, 2018 9:25 am
- Forum: Zero Order Reactions
- Topic: slope
- Replies: 9
- Views: 4825
Re: slope
Since k, the constant, is always positive, we must change the sign in front of k to denote the slope. So for zero order reactions, if we plot [A] vs time, the slope is (-), meaning that slope = (-)k. For first order reactions, if plot ln[A] vs time, the slope is also (-), so we set that equal to (-)...
- Fri Feb 23, 2018 12:28 pm
- Forum: General Rate Laws
- Topic: Doubling Concentration in Second-Order Reaction
- Replies: 2
- Views: 2056
Re: Doubling Concentration in Second-Order Reaction
The definition of a second-order reaction is that rate is proportional to the second power (ie. squaring) of the concentration. By doubling the reactant concentration, you would be actually quadrupling the reaction rate since 2 squared is 4. If it was a first-order reaction, rate is proportional to ...
- Fri Feb 23, 2018 12:23 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Homework 14.25
- Replies: 4
- Views: 606
Re: Homework 14.25
I asked the UA this, and he said it was definitely unclear, but you should always go with the half reaction that is most (-), even if there are multiple listed half reactions involving the same element.
- Fri Feb 23, 2018 12:21 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.13d
- Replies: 3
- Views: 470
Re: 14.13d
I had the same question because gold solid is not a reactant in the overall reaction. However, when you balance the half reactions (with gold solid being the reactant of the second half reaction) and sum them, the overall reaction matches the reaction stated in the problem.
- Mon Feb 19, 2018 2:10 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram Order (14.11) [ENDORSED]
- Replies: 4
- Views: 678
Re: Cell Diagram Order (14.11) [ENDORSED]
The oxidized form should be before the reduced form if both are the same phase. But can anyone answer my original question?
- Sun Feb 18, 2018 11:47 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram Order (14.11) [ENDORSED]
- Replies: 4
- Views: 678
Cell Diagram Order (14.11) [ENDORSED]
Can anyone explain the order of the cell diagram? I thought it was reactant first and product second, but in several problems, I found it to be inconsistent. Ex) 14.11 b) Cl- is written first but is a product. 14.11 e) Cl- / Hg2Cl2 / Hg is written like this in the book, but Cl- and Hg are both produ...
- Sun Feb 18, 2018 4:12 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Self-Test 14.12B
- Replies: 1
- Views: 407
Self-Test 14.12B
Calculate the potential of a cell constructed with two silver electrodes. The electrolyte in one compartment is 1.0 m AgNO3(aq). In the other compartment, NaOH has been added to a AgNO3 solution until the pH 12.5 at 298 K. Answer from back of book: At pH 12.5, pOH = 1.5 and [OH-] =10 ^ -1.5 = 0.032 ...
- Sat Feb 17, 2018 1:55 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Self Test 14.5B part a
- Replies: 1
- Views: 403
Self Test 14.5B part a
Given this cell diagram, write the chemical equation. Hg(l) / HgCl2(s) / HCl(aq) // Hg2(NO3)2 (aq) / Hg(l) I checked with the answers in the back of the book, and I don't understand 1) why does Hg2(NO3)2 become 2Hg(l) and 2NO3- instead of 2Hg+ (aq) and 2NO3- ? 2) why does the overall reaction show 2...
- Mon Feb 12, 2018 1:19 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Entropy Definitions
- Replies: 2
- Views: 453
Re: Entropy Definitions
^ 1) But what is the difference between standard molar entropy and residual entropy?
2) In the solution manual, 9.55 looks at the difference between formation and molar entropy, so what is the difference?
2) In the solution manual, 9.55 looks at the difference between formation and molar entropy, so what is the difference?
- Mon Feb 12, 2018 1:14 pm
- Forum: Calculating Work of Expansion
- Topic: 8.93 Expansion?
- Replies: 4
- Views: 684
Re: 8.93 Expansion?
^ but 1) combustion involves liquid water, not gas and 2) the solution manual says that work is +3.72 kj/mol, so I am still confused.
- Mon Feb 12, 2018 9:48 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Entropy Definitions
- Replies: 2
- Views: 453
Entropy Definitions
What is the difference between 1) standard molar entropies 2) standard molar entropies for formation 3) residual entropies?
- Mon Feb 12, 2018 9:45 am
- Forum: Calculating Work of Expansion
- Topic: 8.93 Expansion?
- Replies: 4
- Views: 684
8.93 Expansion?
For part a) Calculate the work that must be done against the atmosphere for the expansion of the gaseous products in the combustion of 1.00 mol C6H6(l) at 25 C and 1.00 bar. Why is this considered expansion, and why is work being done against the atmosphere? The equation I had was: C6H6 (l) +15/2 O2...
- Mon Feb 12, 2018 9:40 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: nR = PV/T (9.47) [ENDORSED]
- Replies: 1
- Views: 465
nR = PV/T (9.47) [ENDORSED]
Hi! I'm not sure where I went wrong, but in 9.47, I tried substituting PV/T into nR in the equation delta S = nR ln (V2/V1). However, the answer I got was .0379 J/K instead of 3.84 J/K. Did I do something wrong, or am I mistaken in substituting PV/T into nR? My work: delta S = nR ln (V2/V1) = PV/T x...
- Thu Feb 08, 2018 11:37 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: oxygen has 0 Gibbs free energy of formation
- Replies: 2
- Views: 5551
oxygen has 0 Gibbs free energy of formation
Why does oxygen (and other naturally occurring elements like I2, H2, K) all have 0 Gibbs free energy, even though there is some numerical value for molar entropy still listed in the Appendix? Doesn't delta G formation = delta H formation - T (delta molar entropy)?
- Wed Feb 07, 2018 10:17 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: 9.55
- Replies: 2
- Views: 439
Re: 9.55
But why are the values different?
- Wed Feb 07, 2018 10:05 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: 9.55
- Replies: 2
- Views: 439
9.55
What is the difference between delta Sm and delta Sf? Why are the values different? Thank you in advance:)
- Mon Feb 05, 2018 2:51 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 9.21
- Replies: 3
- Views: 468
Re: 9.21
Kb is Boltzmann's constant, which is given to us on exams. The question is essentially asking for the entropy based on how many ways can you arrange the molecules. For part a), there is only 1 way to arrange it because they are all the same molecules aligned the same way. Part b), there is 4^64 ways...
- Mon Feb 05, 2018 2:47 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Question: Refrigerator Cooling
- Replies: 3
- Views: 540
Re: Question: Refrigerator Cooling
Similar is the example Dr. Lavelle used in class. If you light a match in a large room, why doesn't the temperature increase? There is no significant increase because the heat of the match is too small to affect the entire room.
- Mon Feb 05, 2018 2:39 pm
- Forum: Balancing Redox Reactions
- Topic: Memorization Technique [ENDORSED]
- Replies: 2
- Views: 636
Re: Memorization Technique [ENDORSED]
Another common one is OIL RIG
Oxidation is loss (of e-)
Reduction is gain (of e-)
Oxidation is loss (of e-)
Reduction is gain (of e-)
- Mon Jan 29, 2018 6:55 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Last quarters finals
- Replies: 4
- Views: 354
Re: Last quarters finals
^ You can keep the test.
- Mon Jan 29, 2018 6:54 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: estimating an entropy change
- Replies: 2
- Views: 300
Re: estimating an entropy change
Well, there is no gas on the reactants side, but there is a gas on the products side. There is a net increase in gases, which results in a positive change in entropy. The molar entropy of a gas is much larger than that of solids and liquids, so we can assume that entropy's sign is positive without h...
- Mon Jan 29, 2018 3:16 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Lecture Diagram
- Replies: 2
- Views: 344
Re: Lecture Diagram
The diagram is of a heat reservoir, meaning that it is always at the same temperature. The ideal gas expands into the vacuum and does work, but to remain at the same temperature, heat is added. When it expands, it pulls up the mass. Delta U is still 0 because q + w = 0, where heat added is equal to ...
- Tue Jan 23, 2018 7:22 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Open System [ENDORSED]
- Replies: 4
- Views: 497
Re: Open System [ENDORSED]
^ but what is an example of work on the open system?
- Mon Jan 22, 2018 9:55 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Open System [ENDORSED]
- Replies: 4
- Views: 497
Open System [ENDORSED]
This might be a silly question, but what are examples of how you can do work on an open system?
- Mon Jan 22, 2018 4:58 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: kj/mol vs kj
- Replies: 2
- Views: 246
kj/mol vs kj
Hi, I’m very confused about when we should use kj/mol and when we should use kj. The solution manual gives different units for each type of problem, some of them even contradicting each other. Can anyone give me a concrete answer when to use what? Here are a few examples of where I am confused. 1. I...
- Mon Jan 22, 2018 4:26 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.99
- Replies: 6
- Views: 731
Re: 8.99
You first need to write a chemical reaction between HCl and zinc. This is also a limiting reactant problem, so you need to keep that in mind. Afterwards, you need to solve for the enthalpy of reaction using enthalpies of formation in the book. The energy released by the reaction can be found by mult...
- Mon Jan 22, 2018 4:20 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: heat required in example 8.3 pg 270
- Replies: 1
- Views: 226
Re: heat required in example 8.3 pg 270
delta T is the final temperature minus the initial temperature, so in this case, 100 degrees celsius -20 degrees celsius. The means that delta T = 80 degrees celsius. You can also write it as 80K because the difference in temperature can be expressed as either unit.
- Mon Jan 22, 2018 12:01 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Internal Energy
- Replies: 3
- Views: 565
Re: Internal Energy
Internal energy is a state function because it depends only on the current state of the system. For example, It doesn't matter whether you added 50J of heat or the surroundings did 50J of work on the system. Therefore, it is independent of how the system achieved the current state.
- Mon Jan 22, 2018 11:53 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.65
- Replies: 3
- Views: 641
Re: 8.65
To start off, you should write the reaction for the formation of N2O5, where N2O5 is on the right hand side with a coefficient of 1. Using the other reactions they give you, you want to rearrange the equations so that the sum of the 2 reactions would give you the overall reaction above. Using Hess's...
- Sun Jan 21, 2018 4:10 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity Units (8.43)
- Replies: 2
- Views: 359
Re: Heat Capacity Units (8.43)
Isn't molar heat capacity J/Kmol ? In this problem, why doesn't the Kelvin appear?
- Sun Jan 21, 2018 12:27 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity Units (8.43)
- Replies: 2
- Views: 359
Heat Capacity Units (8.43)
Hi, I am confused about the heat capacity units in 8.43. The book says that the heat capacity for a solid is 30 J/mol and for a liquid, it is 60J/mol. What does "J/mol" exactly mean, and what does it say about the temperature? I thought that heat capacity was J/ unit of temperature, so why...
- Tue Jan 16, 2018 11:41 pm
- Forum: Calculating Work of Expansion
- Topic: 8.3b
- Replies: 3
- Views: 313
Re: 8.3b
8.11 asks which process does more work, so this question specifically tells us to look at work from the point of view of the system itself, not the surroundings. So using the formula, we would still conclude that reversible expansion produces a more negative work than irreversible expansion. Since w...
- Tue Jan 16, 2018 11:34 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Help understanding what is being asked in 8.19
- Replies: 2
- Views: 1075
Re: Help understanding what is being asked in 8.19
In part a, you need heat to increase the temperature of both the stainless steel in 8.20 (or copper in 8.19) and the water. Using the formula q = mass x specific heat capacity x temperature change, you would need to add q of water and q of stainless steel (or copper). These should be separate sums, ...
- Tue Jan 16, 2018 5:41 pm
- Forum: Calculating Work of Expansion
- Topic: 8.3b
- Replies: 3
- Views: 313
Re: 8.3b
Work acts on the system, so if the volume is compressed, then work is being done on the system. Therefore, work is positive. However, if the volume expands, then work would be negative.
- Tue Jan 16, 2018 1:01 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Equations and formulas
- Replies: 2
- Views: 232
Re: Equations and formulas
The equation and constants sheet will be given.
Here is a link to the same question, but answered by Chem Mod.
viewtopic.php?f=129&t=25577
Here is a link to the same question, but answered by Chem Mod.
viewtopic.php?f=129&t=25577
- Tue Jan 16, 2018 12:59 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.45
- Replies: 2
- Views: 275
Re: 8.45
If you really wanted to, you can also look at the reaction in terms of carbon, which would be 358.8kj/4mol C. You can then perform stoichiometric conversions to convert moles of S8 to Carbon and whatnot, but because the problem gives the reaction in terms of S8, it would be much more advantageous to...
- Sat Jan 13, 2018 5:44 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Re-registering
- Replies: 1
- Views: 216
Re: Re-registering
Dr. Lavelle said all we had to do was change our username/alias from 14A, so having previous posts are ok since those posts are associated with the same account.
- Thu Jan 11, 2018 10:05 am
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture Outline
- Replies: 2
- Views: 395
Re: Lecture Outline
Unfortunately, there is no schedule that corresponds lectures to textbook sections, and the outline groups everything together. However, at the end of each chapter in the book, there's a "skills you should have mastered" section that shows which sections align with which topics. I would lo...
- Thu Jan 11, 2018 9:50 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity: molar versus specific
- Replies: 3
- Views: 2221
Re: Heat Capacity: molar versus specific
Molar heat capacity measures how much heat is needed to increase the temperature of one mole of that substance by one degree while specific heat capacity measures how much heat is needed to increase the temperature of one gram by one degree. I believe specific heat capacity is used in calorimeter pr...
- Wed Jan 10, 2018 3:11 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Change in Enthalpy of the Reverse Reaction
- Replies: 5
- Views: 4310
Re: Change in Enthalpy of the Reverse Reaction
Yes, you would just change the sign to indicate whether heat is being absorbed or released. When solid becomes liquid, the sign is positive since heat must be added to break bonds. If liquid froze to become solid, then the sign must be negative since heat must be released to form bonds.
- Fri Dec 08, 2017 8:47 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: HI vs HOI
- Replies: 2
- Views: 1289
HI vs HOI
So this isn't a hw question, but this is more from the lecture notes. Why is HI a really strong acid, and HOI not as strong? I understand that HI has a long bond length and is long, and I understand that having more oxygens stabilizes the resulting anion. However, when combining these concepts, it w...
- Fri Dec 08, 2017 8:43 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: 12.53 b
- Replies: 1
- Views: 444
12.53 b
I know this question has been asked several times, but I am still very confused about why formic acid is stronger than acetic acid. The solution manual and previous forums talk about electron donating properties and electron withdrawing. I'm not sure what these mean. 1) Why does the CH3 group in ace...
- Thu Dec 07, 2017 5:39 pm
- Forum: Naming
- Topic: Hydrate + Prefixes [ENDORSED]
- Replies: 1
- Views: 522
Hydrate + Prefixes [ENDORSED]
If H2O is outside the coordination compound, then it is called hydrate. We include its Greek prefix. Is H2O the only compound where we would have a prefix even if it's outside the brackets?
- Wed Dec 06, 2017 10:54 am
- Forum: Administrative Questions and Class Announcements
- Topic: 1pm lecture cancelled? [ENDORSED]
- Replies: 3
- Views: 729
1pm lecture cancelled? [ENDORSED]
If classes after noon are cancelled, will the 11am and 1pm lectures be cancelled as well? And if the 11am is not cancelled, will the 11am lecture be "ahead" of the 1pm lecture?
- Mon Dec 04, 2017 12:30 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: 12.45 [ENDORSED]
- Replies: 2
- Views: 381
Re: 12.45 [ENDORSED]
I'm assuming you are referring to 12.43 instead of 12.45, but I would use the "withdrawing power" or electronegativity differences to explain why 2,4,6 trichlorophenol has a larger Ka. You would use the Ka to identify which is stronger, but to "account for the difference in acid stren...
- Wed Nov 29, 2017 10:39 pm
- Forum: Naming
- Topic: Self Test 17.3B (a)
- Replies: 1
- Views: 342
Self Test 17.3B (a)
Name the compound [CoBr(NH3)5]SO4
The back of the book states that the answer is pentaaminebromidocobalt(II) sulfate. I understand everything except for the charge of cobalt. Why is the Roman numeral II, rather than III?
The back of the book states that the answer is pentaaminebromidocobalt(II) sulfate. I understand everything except for the charge of cobalt. Why is the Roman numeral II, rather than III?
- Mon Nov 27, 2017 8:17 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: problem 11.89
- Replies: 1
- Views: 277
Re: problem 11.89
First identify which is a reactant and which is a product. Since the partial pressure of A decreases, it must be a reactant. Conversely, the partial pressures of B and C increase, so they must be products. To figure out the coefficients, you have to look at the numerical values of each partial press...
- Mon Nov 27, 2017 3:03 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.63
- Replies: 1
- Views: 198
11.63
The solution manual states that "Because the equilibrium constant is small, assume that x <<0.22." I understand that the change in concentration is pretty much negligible because the equilibrium constant is small, but in general, what is the "cutoff" value for K so that we can as...
- Mon Nov 20, 2017 5:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reaction progress [ENDORSED]
- Replies: 2
- Views: 585
Re: Reaction progress [ENDORSED]
You can illustrate the reaction progress on a graph where molar concentration is on the y axis and time on the x axis. As the reaction proceeds, the concentration of reactants decreases while the concentration of products increases. Figure 11.1 shows this also.
- Mon Nov 20, 2017 5:34 pm
- Forum: Ideal Gases
- Topic: solving 11.7
- Replies: 2
- Views: 397
Re: solving 11.7
At equilibrium, the concentrations of reactants and products are constant, so they don't have to necessarily be equal. In this case, the concentration of "single" and "double" molecules do not change from the third to the fourth flask because the number of each remains constant. ...
- Thu Nov 16, 2017 8:56 pm
- Forum: Ionic & Covalent Bonds
- Topic: SiO2
- Replies: 4
- Views: 6132
SiO2
Can anyone explain why SiO2 is polar without knowing what the electronegativity values are? This topic was in another forum, but I'm still confused. Dr. Lavelle specifically said in class that we will not need to know the electronegativity values and that we can determine the difference in electrone...
- Thu Nov 16, 2017 8:51 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: bond angle
- Replies: 4
- Views: 2289
Re: bond angle
The bond angle is the angle between XAX (X being the surrounding atoms, and A being the central atom). Here is a useful chart that shows you what the angles are for any molecular shape. http://mmstcchemistry.weebly.com/upload ... ometry.pdf
- Wed Nov 15, 2017 12:43 pm
- Forum: Hybridization
- Topic: Notation
- Replies: 6
- Views: 787
Re: Notation
It is just to indicate the specific orbital within a sub shell. Normally, you would just write p3, but if you wanted to specify that there are three different orbitals lying along the x,y,z axis, then you would write px py pz. Both are acceptable unless otherwise stated.
- Thu Nov 09, 2017 11:51 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Relationship between Orbitals and Properties of Electrons
- Replies: 2
- Views: 342
Relationship between Orbitals and Properties of Electrons
This is from the outline on Lavelle's website.
"Name and explain the relationship of each of the four s-, p-, and d-orbitals to the properties of electrons in these states."
I'm confused about how to answer this. Any help is appreciated!
"Name and explain the relationship of each of the four s-, p-, and d-orbitals to the properties of electrons in these states."
I'm confused about how to answer this. Any help is appreciated!
- Tue Nov 07, 2017 9:50 pm
- Forum: Ionic & Covalent Bonds
- Topic: 3.11
- Replies: 3
- Views: 1282
Re: 3.11
The difference between 3.11 and 3.9 is that 3.11 is talking about a 3+ cation whereas 3.9 is talking about a 2+ cation. For 3.11A, we need to find an element with the configuration [Ar]3d74s2. A parent atom loses 3 valence electrons to form a cation, so going from a cation to a parent atom means tha...
- Mon Nov 06, 2017 9:08 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Spin Quantum Number Question
- Replies: 2
- Views: 696
Re: Spin Quantum Number Question
An electron can have either spin value, ms = -1/2 or 1/2. Since 3d9 and 3d10 are in the same orbital, they must have opposite spin. It could be either 1) 3d9 is -1/2 and 3d10 is 1/2 or 2) 3d9 is 1/2 and 3d10 is -1/2. So therefore, 3d10 can have either spin number if 3d9’s spin number is not specified.
- Tue Oct 31, 2017 5:47 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Determining if an atom is in an excited state
- Replies: 2
- Views: 2143
Re: Determining if an atom is in an excited state
The electron configurations tell us whether an atom is in an excited state or ground state. In a ground state, electrons fill orbitals to have the lowest energy, so electrons must occupy the lowest orbitals possible. In an excited state, not all electrons are expected to fill the lowest orbitals pos...
- Tue Oct 31, 2017 5:41 pm
- Forum: Trends in The Periodic Table
- Topic: Ionization energy exception; O
- Replies: 2
- Views: 4594
Re: Ionization energy exception; O
Oxygen has a lower ionization energy than fluorine, as fluorine is farther to the right on the periodic table and follows the trend that IE increases as you go right. However, the anomaly is that oxygen has a lower ionization energy than nitrogen. If we look at the electron configurations, oxygen is...
- Tue Oct 24, 2017 10:06 am
- Forum: Trends in The Periodic Table
- Topic: Trends of ionic radius
- Replies: 4
- Views: 766
Re: Trends of ionic radius
Well the previous reply is not always true because sometimes the ions doesn’t lose or gain enough electrons to subtract or add an energy level. Sometimes you can remove one electron and it would still have the same principal quantum number. Cations are smaller because cations have less electrons tha...
- Tue Oct 24, 2017 10:02 am
- Forum: Trends in The Periodic Table
- Topic: Concept question (2.81)
- Replies: 1
- Views: 258
Re: Concept question (2.81)
So it makes sense that oxygen has a lower ionization energy than fluorine, as fluorine is more right on the periodic table and follows the above trend. However, the anomaly is that oxygen has a lower ionization energy than nitrogen. If we look at the electron configurations, oxygen is p4 while nitro...
- Tue Oct 17, 2017 5:32 pm
- Forum: DeBroglie Equation
- Topic: Help with #1.33 part C
- Replies: 1
- Views: 334
Re: Help with #1.33 part C
3.6 x 10^3 is km/s but the SI unit should be meters and not kilometers. Therefore, you must convert km/s to m/s so that all the units cancel out in the final equation.
- Mon Oct 16, 2017 2:08 pm
- Forum: Properties of Electrons
- Topic: Atomic Spectra [ENDORSED]
- Replies: 3
- Views: 536
Re: Atomic Spectra [ENDORSED]
So we want to find how long one wavelength of krypton 86 is. The problem gives that there are 1,650,763.73 wavelengths in one meter. To find how long one wavelength is, we must divide 1m by the total number of wavelengths in one meter. An analogy is: there are 4 laps in a mile. How long is each lap?...
- Mon Oct 16, 2017 2:04 pm
- Forum: Properties of Light
- Topic: Quiz #2 References [ENDORSED]
- Replies: 4
- Views: 597
Re: Quiz #2 References [ENDORSED]
This is the set of constants and equations given every test from the class website. https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/constants_equations.pdf If there are any additional numerical constants specific to a problem, they should be given on the sheet (Example: 1ev= 1.602x...
- Thu Oct 12, 2017 7:46 pm
- Forum: Properties of Light
- Topic: 1.27
- Replies: 3
- Views: 488
Re: 1.27
Avogadro's constant can be used to find the moles of anything really. Yes, you can use it to find the quantity of atoms, but you can also apply it for molecules, formula units, photons, etc.
- Wed Oct 11, 2017 2:30 pm
- Forum: Properties of Light
- Topic: 1.3 homework [ENDORSED]
- Replies: 11
- Views: 1353
Re: 1.3 homework [ENDORSED]
Hello, a) No, speed is constant at 3.00 x 10^8 m/s b) No, wavelength increases. Frequency and wavelength are inversely proportional since c = (lambda)(freq) c) Yes, the electric field oscillates in strength and direction. If the frequency decreases, then the field oscillates less. d) No, energy is d...
- Wed Oct 04, 2017 3:47 pm
- Forum: Significant Figures
- Topic: If last digit is 5: round to nearest even number?
- Replies: 2
- Views: 2833
If last digit is 5: round to nearest even number?
"IF LAST DIGIT IS 5: ROUND TO NEAREST EVEN NUMBER (2 sf then 2.35 is 2.4 and 2.65 is 2.6)" I was reading through the "Everything You Want to Know about Sig Figs" link on the class website, and I read the part above. I've never heard of this rule and have been sticking to the 0-4,...
- Tue Oct 03, 2017 1:36 pm
- Forum: Limiting Reactant Calculations
- Topic: Help with M9
- Replies: 5
- Views: 870
Re: Help with M9
I actually missed this too, but I realize now that the question asks for the net ionic equation. This means that spectator ions like sodium wouldn't be part of the equation unless it was asking for the complete ionic equation.
- Tue Oct 03, 2017 10:21 am
- Forum: Balancing Chemical Reactions
- Topic: Balancing Process
- Replies: 11
- Views: 1256
Re: Balancing Process
There’s no really strict guideline to choosing which to balance first. What you said is correct; you balance either hydrogen or phosphorus first since oxygen appears in both reactants and thus harder to balance. While hydrogen and phosphorus have equal number of atoms, I would start with phosphorous...