Search found 57 matches

by Gianna Apoderado 1B
Sat Mar 17, 2018 10:30 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Catalyst and Intermediate
Replies: 7
Views: 380

Re: Catalyst and Intermediate

A catalyst will be used up in a step in the reaction mechanism but gets produced again in a different step. An intermediate gets produced in a step of a mechanism but gets consumed in another. Also, a catalyst can be included in the overall rate law, while an intermediate cannot.
by Gianna Apoderado 1B
Sat Mar 17, 2018 1:20 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation
Replies: 2
Views: 173

Re: Nernst Equation

I believe the Nernst equation on the equation sheet with log(Q) assumes that the temperature is 298 K (25oC), while the ln(Q) equation can take into account any temperature.
by Gianna Apoderado 1B
Wed Mar 14, 2018 4:30 pm
Forum: *Enzyme Kinetics
Topic: Enzymes in rate law
Replies: 4
Views: 267

Re: Enzymes in rate law

Yes, because the concentration of catalysts affect the reaction rate, the higher the concentration, the faster the reaction!
by Gianna Apoderado 1B
Mon Mar 12, 2018 2:22 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.65 b [ENDORSED]
Replies: 1
Views: 98

Re: 15.65 b [ENDORSED]

I believe that when it asks about the reaction, it generally means the forward direction, unless otherwise stated. In this case, the reaction is endothermic because the activation energy of the forward direction is greater than the activation energy of the reverse reaction, which means that the forw...
by Gianna Apoderado 1B
Mon Mar 12, 2018 2:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Identigying Anode/Cathode when just given species names and concentrations
Replies: 4
Views: 181

Re: Identigying Anode/Cathode when just given species names and concentrations

Given the species, you can generally predict which reaction will be the reduction and oxidation from a given list of reactions and their standard reduction potentials. The more positive Eo, the stronger the oxidizing agent is, and the more likely that the species will be reduced.
by Gianna Apoderado 1B
Mon Mar 12, 2018 1:53 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: 9. 35 and Cv vaues
Replies: 1
Views: 192

Re: 9. 35 and Cv vaues

I was wondering this as well.. I used (3R/2) as Cv for all three gases, and I still got B < C = A, the same result as the one on the "Errors in Solution Manual" page.
by Gianna Apoderado 1B
Mon Mar 05, 2018 10:02 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: HW 15.23
Replies: 2
Views: 136

Re: HW 15.23

You do end up using the natural log (ln) in this calculation, after you solve for the [A]t! After you get that value, you plug it in
k = (ln([A]0/[A]t)) / t to get k.
by Gianna Apoderado 1B
Mon Mar 05, 2018 9:49 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Question about Test #3
Replies: 2
Views: 132

Re: Question about Test #3

From #45-73 for sure, but there may be integrated exercises (#79 onwards) that might apply to the topics we learned in 15.1-15.6, so i would take a look there just to make sure.
by Gianna Apoderado 1B
Mon Mar 05, 2018 9:46 pm
Forum: Second Order Reactions
Topic: 2nd order rxn integration
Replies: 2
Views: 105

Re: 2nd order rxn integration

When you take the integral of the -d[A]/[A]2, it gets cancelled out. I attached the step by step integration below:
by Gianna Apoderado 1B
Fri Mar 02, 2018 3:39 pm
Forum: General Rate Laws
Topic: Question 15.39 [ENDORSED]
Replies: 4
Views: 156

Re: Question 15.39 [ENDORSED]

Since it was specified that the reactions are second-order, we can use 1/[A] = kt + 1/[A]0, and just solve for t.
by Gianna Apoderado 1B
Fri Mar 02, 2018 3:30 pm
Forum: First Order Reactions
Topic: Pseudo-First-Order Reactions [ENDORSED]
Replies: 3
Views: 142

Re: Pseudo-First-Order Reactions [ENDORSED]

We may be asked to identify/recognize when we can implement the pseudo-order reaction method, such as when the concentration of one or more reactants are far greater than the concentration of another reactant. Then you would just calculate the rate as if it were a normal ____ order reaction.
by Gianna Apoderado 1B
Fri Mar 02, 2018 3:24 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: k prime vs k [ENDORSED]
Replies: 2
Views: 768

Re: k prime vs k [ENDORSED]

From what I understand from today's lecture, k is the normal rate constant for a reaction, let's say for rate = k[A] N [B] M [C] L . However, if [B] 0 and [C] 0 >> [A] 0 , we can say that rate = k'[A] N , and that the reaction is a pseudo-first order reaction. Comparing the two, we can see differenc...
by Gianna Apoderado 1B
Mon Feb 19, 2018 5:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.13 part D
Replies: 2
Views: 119

Re: 14.13 part D

I was wondering this as well, since Au3+ is supposed to be on the products side. It may have been a solution manual error.
by Gianna Apoderado 1B
Mon Feb 19, 2018 5:12 pm
Forum: Balancing Redox Reactions
Topic: 14.9
Replies: 2
Views: 120

Re: 14.9

Since the equation is balanced, you can take a half-reaction from that equation to find the number of electrons, n r . When 2 Ce 4+ --> 2 Ce 3+ , we can see that the overall charge on each side goes from +8 to +6, so, in order to balance that, two electrons need to be added to the left side. This is...
by Gianna Apoderado 1B
Mon Feb 19, 2018 5:08 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.19
Replies: 1
Views: 68

14.19

In the calculation of the standard potential for the left (Metal) reduction, how come the sign of the Cu oxidation potential doesn't become negative? Initially, I had: E o (left) = E o (right) - E o (cell) = -0.34 - 0.689 = -1.029 But when I checked the answer, it was -0.349, meaning the potential o...
by Gianna Apoderado 1B
Mon Feb 12, 2018 9:03 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneous Change
Replies: 1
Views: 76

Re: Spontaneous Change

In the book, it says that a spontaneous process has a natural tendency to occur, so it may not even occur at all, depending on the rate of that tendency (which will be covered in Ch. 15)
by Gianna Apoderado 1B
Mon Feb 12, 2018 8:59 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: work and free energy
Replies: 2
Views: 87

Re: work and free energy

The change in free energy (delta G) for a spontaneous process is the energy that is available to do useful work. We were also given an equation in lecture, wmax = delta G, where maximum work is done by a process at constant temperature and pressure. Hope that helps!
by Gianna Apoderado 1B
Mon Feb 12, 2018 8:52 pm
Forum: Calculating Work of Expansion
Topic: Reversible, isothermal reactions
Replies: 1
Views: 91

Re: Reversible, isothermal reactions

A similar question/post was posted on Chemistry Community a few weeks ago:

viewtopic.php?f=128&t=26506

Someone said while not all isothermal reactions are reversible, reversible reactions are isothermal.
by Gianna Apoderado 1B
Mon Feb 12, 2018 8:47 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Residual Entropy
Replies: 1
Views: 87

Re: Residual Entropy

Residual entropy is the entropy of a sample at T = 0, that comes from positional disorder surviving at that temperature. In other words, it is the disorder retained by some solids at T = 0.
by Gianna Apoderado 1B
Fri Feb 09, 2018 8:43 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Self test 8.14A
Replies: 2
Views: 128

Re: Self test 8.14A

I also got the same answer as Kelly! Make sure to double check your signs, you may have misplaced a negative sign or positive sign.
by Gianna Apoderado 1B
Fri Feb 09, 2018 8:38 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Calculating the change in entropy with constant pressure
Replies: 2
Views: 110

Re: Calculating the change in entropy with constant pressure

I would stick with using C(p,m) in that deltaS equation, which as said by Joyce, is (5/2)R at constant pressure.
by Gianna Apoderado 1B
Fri Feb 09, 2018 8:32 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.99
Replies: 2
Views: 150

Re: 11.99

By the way, the table for bond dissociation energies is Table 3.3, which is page 93 in the textbook!
by Gianna Apoderado 1B
Fri Feb 09, 2018 8:24 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: delta U [ENDORSED]
Replies: 10
Views: 360

Re: delta U [ENDORSED]

Yes, like Mitch said above, delta U has two components, as seen in the equation deltaU = q + w (the first law of thermodynamics). Even if change in temperature is 0, and q is 0, work can still be done and affect internal energy.
by Gianna Apoderado 1B
Sat Feb 03, 2018 10:38 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Units of ΔS
Replies: 3
Views: 249

Re: Units of ΔS

From what I’ve seen, delta S is given in both J/K and J/K•mol-1 depending on the context of what you need it for! (Ive always assumed that the “per mole” is implied)
by Gianna Apoderado 1B
Sat Feb 03, 2018 10:34 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: entropy vs. Degeneracy
Replies: 4
Views: 180

Re: entropy vs. Degeneracy

We can also view entropy as representative of the amount of energy that is unavailable to do mechanical work in a closed system!
by Gianna Apoderado 1B
Sat Feb 03, 2018 10:26 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta S, H, and G
Replies: 2
Views: 68

Re: Delta S, H, and G

Like Michelle, I assumed the r subscript stood for reaction, but when I looked it up, it said r stood for rotational?
by Gianna Apoderado 1B
Mon Jan 22, 2018 8:35 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.61 Question
Replies: 2
Views: 73

Re: 8.61 Question

Yes, what Ammar said above is true! In addition, as you work through the problem you can see that you'll have to get rid of N2, which isn't in the net equation, and flipping the second equation is the only way to get rid of it.
by Gianna Apoderado 1B
Mon Jan 22, 2018 8:11 pm
Forum: Administrative Questions and Class Announcements
Topic: Equipartition Theorem - Test 1
Replies: 1
Views: 128

Re: Equipartition Theorem - Test 1

Hi! For test 1, Lavelle said to look through Outline 1 on his website for the concepts we will be tested on, except for isothermal problems. Since the equipartition theorem is not on there, I would say that we don't need to study it.
by Gianna Apoderado 1B
Thu Jan 18, 2018 10:20 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.25
Replies: 2
Views: 122

Re: 8.25

You can also look at it as finding the q of the reaction, or qrxn. So, using the relationship of qrxn = -qcal, your calculated value of the specific heat of the calorimeter and the change in temperature, you can find the solution (much like how Joyce did!)
by Gianna Apoderado 1B
Thu Jan 18, 2018 10:15 pm
Forum: Calculating Work of Expansion
Topic: units for calculating work
Replies: 6
Views: 124

Re: units for calculating work

I would stick with atm for pressure and liters (L) for volume when calculating work using w=-P*deltaV.
by Gianna Apoderado 1B
Thu Jan 18, 2018 10:11 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW 8.21
Replies: 2
Views: 111

Re: HW 8.21

Going by the sig figs of the given values, I agree that it should be 3 sig figs. (Maybe the book isn't as strict with sig figs, I'm not sure)
by Gianna Apoderado 1B
Fri Jan 12, 2018 11:03 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Intensive vs extensive property
Replies: 3
Views: 134

Re: Intensive vs extensive property

Yes! To add on to what Lisa said, intensive properties only depend on the type of the substance, so no matter the size or amount of substance you have, the property does not change. For example, the color of copper does not change whether you have 2 g of it or 50 g.
by Gianna Apoderado 1B
Fri Jan 12, 2018 10:56 pm
Forum: Calculating Work of Expansion
Topic: Calculating required heat
Replies: 3
Views: 2108

Re: Calculating required heat

I don't really get why you need to add the heat of the kettle and the heat of the water together. I thought it was just asking for the heat supplied to the kettle to heat it up to 100 degrees Celsius. Hi, I assume you mean it was just asking for the heat needed for the water to boil. We need to tak...
by Gianna Apoderado 1B
Fri Jan 12, 2018 10:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar heat capacity of gas
Replies: 3
Views: 125

Re: Molar heat capacity of gas

Gas has two molar heat capacities because there is one for constant volume (Cv) and one for contant pressure (Cp) !
by Gianna Apoderado 1B
Sat Dec 09, 2017 9:46 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: titration
Replies: 3
Views: 168

Re: titration

Since Dr. Lavelle didn't cover it in lecture or included it in the topic outlines on his website, I believe we don't need to know it for the final!
by Gianna Apoderado 1B
Sat Dec 09, 2017 9:43 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Conjugate seesaw
Replies: 3
Views: 301

Re: Conjugate seesaw

The conjugate seesaw is a term describing the relative strength of an acid/base to its conjugate base/acid. The stronger the acid, the weaker its conjugate base. The stronger the base, the weaker its conjugate base.
by Gianna Apoderado 1B
Thu Dec 07, 2017 12:27 pm
Forum: Lewis Acids & Bases
Topic: What tables should we know from the book?
Replies: 4
Views: 254

Re: What tables should we know from the book?

If I recall correctly, the only table we were meant to be quite familiar with was Table 17.4. The other tables in the chapters we've discussed may be helpful in understanding concepts, but I don't believe we have to have them memorized.
by Gianna Apoderado 1B
Thu Dec 07, 2017 12:19 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation Numbers
Replies: 2
Views: 123

Re: Oxidation Numbers

Hi! Oxidation numbers are not always positive! For example, for a sulfur ion S^2-, its oxidation number is -2.
by Gianna Apoderado 1B
Mon Nov 27, 2017 5:45 pm
Forum: Naming
Topic: Alphabetical Order
Replies: 2
Views: 124

Re: Alphabetical Order

Well, I can see why NH3 will come before the Cl, because it is called ammine, while the chloride is called chlorido. I'm not too sure why NO2, or nitro, comes before chlorido though.
by Gianna Apoderado 1B
Mon Nov 27, 2017 5:40 pm
Forum: Naming
Topic: Problem 17.31 d [ENDORSED]
Replies: 3
Views: 202

Re: Problem 17.31 d [ENDORSED]

That might have just been a book error, or maybe a rare exception to the rule, because according to Toolbox 17.1 we do name ligands in alphabetical order!
by Gianna Apoderado 1B
Fri Nov 24, 2017 3:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electronegativity
Replies: 3
Views: 178

Re: Electronegativity

Yes! We take both the geometry of the molecule as well as the electronegativity of each atom in that molecule to determine polarity. We can use the periodic table and its trends to determine which atom is more electronegative than the other (but take note of the exceptions to this rule - such as the...
by Gianna Apoderado 1B
Fri Nov 24, 2017 3:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: HW 4.73
Replies: 2
Views: 208

Re: HW 4.73

Also, we know that CH2 has a larger bond angle than CH4 because CH2 has less electron regions, only 3, so when we apply the electron repulsion theory, they can be further apart from each other than a molecule with 4 electron regions. Hope that helps!
by Gianna Apoderado 1B
Fri Nov 24, 2017 3:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: HW 4.73
Replies: 2
Views: 208

Re: HW 4.73

Yes, CH2 would have a bond angle less than 120 due to the lone pair! The so-called electron "cloud" takes up a large volume of space, and electron repulsion from that lone pair pushes down on the bond angles.
by Gianna Apoderado 1B
Wed Nov 15, 2017 8:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.1 Lone pairs
Replies: 6
Views: 317

Re: 4.1 Lone pairs

Here is a diagram clarifying what Ashley said above! You can see that the 3 lone pairs and their electron "clouds" have repulsion, such that the bonds between the central atom and the two other atoms are manipulated to a linear shape. https://image.slidesharecdn.com/tang04-vsepr-1209261830...
by Gianna Apoderado 1B
Wed Nov 15, 2017 8:07 pm
Forum: Hybridization
Topic: Benzene Hybridization [ENDORSED]
Replies: 4
Views: 693

Re: Benzene Hybridization [ENDORSED]

Yes, just to reiterate, every single bond, as well as the first bond (so only 1!) in a double or triple bond, counts as a sigma bond.
by Gianna Apoderado 1B
Wed Nov 15, 2017 7:58 pm
Forum: Dipole Moments
Topic: Polar and non-polar molecules
Replies: 2
Views: 131

Re: Polar and non-polar molecules

For me, how I identify polar vs nonpolar molecules is by looking at the lewis structures of the molecules, and determining whether on not the shape allows for dipoles (if there are any) to cancel. Take two common examples: CO2 and H20. When you draw the lewis structure for H20, you'll see that the s...
by Gianna Apoderado 1B
Wed Nov 08, 2017 1:52 pm
Forum: Trends in The Periodic Table
Topic: Hydrogen Electronegativity
Replies: 4
Views: 696

Re: Hydrogen Electronegativity

From what I understand, hydrogen has relatively high electronegativity, especially compared to the other elements in its group, due to only having one electron in its 1s shell. Atoms are more stable and "happiest" with a full shell, so hydrogen has a higher tendency to attract an electron ...
by Gianna Apoderado 1B
Wed Nov 08, 2017 1:44 pm
Forum: Trends in The Periodic Table
Topic: Atomic/Ionic Radius [ENDORSED]
Replies: 2
Views: 187

Atomic/Ionic Radius [ENDORSED]

For test 3 question 2b, we had to place Cl, Na, and Br- in increasing atomic or ionic radius. I had them in the order of Cl < Br- < Na, but the correct answer was Cl < Na < Br-. I understand that Br- is larger than the neutral atom Br due to the extra electron, but how is it larger than Na, when the...
by Gianna Apoderado 1B
Mon Nov 06, 2017 11:29 pm
Forum: Limiting Reactant Calculations
Topic: Post-Module Assess. #31 and #33
Replies: 1
Views: 176

Re: Post-Module Assess. #31 and #33

31. Using the mole ratio provided in the chemical equation, 1 mole of A means that you'll use 0.5 moles of B. (You could convert this into grams if you know the grams per mole of B). 33. Since the limiting reagent is A, the max amount of product you could produce has to be calculated from the amount...
by Gianna Apoderado 1B
Sat Oct 28, 2017 4:44 pm
Forum: Trends in The Periodic Table
Topic: Carbon Electron Affinity [ENDORSED]
Replies: 3
Views: 212

Re: Carbon Electron Affinity [ENDORSED]

Like Nina said above, periodic trends are not always 100%! There are some exceptions to the "rules" that apply generally to the elements.
by Gianna Apoderado 1B
Sat Oct 28, 2017 4:37 pm
Forum: Trends in The Periodic Table
Topic: Electron affinity [ENDORSED]
Replies: 4
Views: 243

Re: Electron affinity [ENDORSED]

Electron affinity, the change in energy when an electron is added to a neutral atom to form a negative ion, affects elements/electrons in the sense that the higher the electron affinity, the greater the attraction for a electron/the easier it is for that element to gain electrons.
by Gianna Apoderado 1B
Mon Oct 16, 2017 8:33 pm
Forum: Photoelectric Effect
Topic: Post Module #19
Replies: 3
Views: 181

Re: Post Module #19

I believe the answer is D! A, B, and C all describe the same equation, which has to do with the photoelectric effect. The equation for D was not derived as a result from the photoelectric experiment!
by Gianna Apoderado 1B
Mon Oct 16, 2017 8:28 pm
Forum: Photoelectric Effect
Topic: Post Module #24
Replies: 3
Views: 198

Re: Post Module #24

I believe the answer is UV! If I'm not mistaken, ultraviolet radiation is used because it has a short wavelength (high frequency), which means it has a higher energy per photon (E=hv). Even with low intensity light, it can eject electrons from the surface.
by Gianna Apoderado 1B
Sat Oct 14, 2017 1:59 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Question about Balmer Series [ENDORSED]
Replies: 2
Views: 853

Re: Question about Balmer Series [ENDORSED]

Hi! Since we are referring to the Balmer series, after the excited electron moves from a higher energy level back down to n=2, it does not move down to n=1, because then we'd be referring to the Lyman series. I've included a link to an image similar to the one shown in Friday's lecture, which hopefu...
by Gianna Apoderado 1B
Tue Oct 10, 2017 12:07 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Balmer and Rydberg series
Replies: 3
Views: 170

Re: Balmer and Rydberg series

From what I understood from the reading, the Balmer series is made up of lines in the visible spectrum. I'm assuming you mean the Lyman series, not the Rydberg series (because there was only mention of a Rydberg constant in the book). The Lyman series is made up of lines in the ultraviolet spectrum....
by Gianna Apoderado 1B
Thu Oct 05, 2017 11:19 pm
Forum: Limiting Reactant Calculations
Topic: M9
Replies: 4
Views: 366

Re: M9

It said on the website that the test will cover Fundamentals, so I'm assuming we will have to know some of the concepts in the textbook in that section that weren't covered in class. I'm not entirely positive though!
by Gianna Apoderado 1B
Mon Oct 02, 2017 11:14 pm
Forum: Empirical & Molecular Formulas
Topic: M21
Replies: 1
Views: 140

Re: M21

Hello Rita, From what I recall, there's a system of writing chemical formulas called the Hill system. Whenever a chemical formula contains carbon atoms, carbon is listed first, then hydrogen (if it contains hydrogen), then the rest of the elements in alphabetical order. If there are no carbon atoms,...

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