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by Hellen Truong 2J
Fri Mar 16, 2018 3:12 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reducing Power
Replies: 5
Views: 167

Re: Reducing Power

Also, I think it's helpful to remember that standard potentials are based on a cell with the hydrogen reaction as the anode. So if E>0, then the species is oxidizing the hydrogen electrode (since the species gets reduced). It E<0, then the forward reaction is not spontaneous, so the species is being...
by Hellen Truong 2J
Fri Mar 16, 2018 3:04 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reducing Power
Replies: 5
Views: 167

Re: Reducing Power

It's based on the table of standard potentials! If you want the species with highest reducing power, you want the species itself to be the most easily oxidized. That means in order of standard potentials, you order species most positive to least positive (most negative).
by Hellen Truong 2J
Fri Mar 16, 2018 3:01 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 2 Calculating standard potential #7
Replies: 2
Views: 236

Re: Test 2 Calculating standard potential #7

I used this method! I got points on the calculations for deltaG(1) and (2), but then I am confused about the final calculation for the standard potential. I added the two values, then divided by -(12mol)*(96485C/mol). I got -0.01V. How can I correct this?
by Hellen Truong 2J
Fri Mar 09, 2018 8:52 am
Forum: Zero Order Reactions
Topic: Half Lives? [ENDORSED]
Replies: 7
Views: 428

Half Lives? [ENDORSED]

Is it accurate to use half lives for questions that say something like 1/4 of the reactant is remaining?
by Hellen Truong 2J
Fri Mar 09, 2018 8:51 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Negative k? [ENDORSED]
Replies: 4
Views: 299

Negative k? [ENDORSED]

Is it possible for k to be negative for any order reaction?
by Hellen Truong 2J
Fri Mar 09, 2018 8:49 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Negative Order
Replies: 7
Views: 765

Negative Order

After you determine what order the reaction is with respect to each reactant, what does it mean conceptually when you get a negative order?
by Hellen Truong 2J
Thu Mar 01, 2018 5:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Basic Cell Diagram
Replies: 1
Views: 96

Basic Cell Diagram

How do you indicate that the reaction occurs in basic conditions for a cell diagram?
by Hellen Truong 2J
Thu Mar 01, 2018 5:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Acidic Cell Diagram
Replies: 1
Views: 90

Acidic Cell Diagram

How do you know which side to put H+ on?
by Hellen Truong 2J
Thu Mar 01, 2018 5:57 pm
Forum: Balancing Redox Reactions
Topic: One Reactant
Replies: 2
Views: 113

One Reactant

If there's a single reactant, how do you know which part is the reducing agent and which is the oxidizing agent?
by Hellen Truong 2J
Sun Feb 25, 2018 10:03 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell Potential
Replies: 4
Views: 141

Cell Potential

Why is the reduction potential for hydrogen 0?
by Hellen Truong 2J
Sun Feb 25, 2018 9:57 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Dissolving [ENDORSED]
Replies: 3
Views: 146

Dissolving [ENDORSED]

How do you know if a metal will dissolve in solution?
by Hellen Truong 2J
Sun Feb 25, 2018 9:56 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Order of Same State Molecules
Replies: 4
Views: 149

Order of Same State Molecules

How do you organize stuff when they're in the same state in a cell diagram? Like oxidized, reduced?
by Hellen Truong 2J
Thu Feb 15, 2018 3:51 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal
Replies: 2
Views: 153

Isothermal

Why does an isothermal reaction have no change in internal energy?
by Hellen Truong 2J
Thu Feb 15, 2018 3:50 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Standard Gibbs Free Energy
Replies: 3
Views: 115

Standard Gibbs Free Energy

Can it be considered standard Gibbs free energy if it is given for a temperature other than 25C?
by Hellen Truong 2J
Thu Feb 15, 2018 3:48 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: Factors Affecting Entropy
Replies: 4
Views: 1015

Factors Affecting Entropy

So I know that physical states (gas>liquid>solid) affect entropy and molecular size affect entropy (larger means more entropy), but which has more of an effect? As in would a heavy liquid or a light gas have more entropy?
by Hellen Truong 2J
Mon Feb 12, 2018 1:00 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Pressure
Replies: 3
Views: 155

Pressure

Why don't changes in pressure affect change in work?
by Hellen Truong 2J
Mon Feb 12, 2018 12:57 am
Forum: Phase Changes & Related Calculations
Topic: Carbon as graphite [ENDORSED]
Replies: 7
Views: 319

Re: Carbon as graphite [ENDORSED]

When using C(gr) to solve for reaction enthalpies using the bond enthalpy method, why would you add the atomization or sublimation of carbon (+717kj/mol)?
by Hellen Truong 2J
Mon Feb 12, 2018 12:54 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bonds Broken - Bonds Formed?
Replies: 2
Views: 149

Re: Bonds Broken - Bonds Formed?

It helps to remember that atoms are more stable when they form bonds, so forming bonds releases energy (exothermic), while breaking them and returning them to a less stable state requires energy (endothermic).
by Hellen Truong 2J
Sat Feb 03, 2018 9:16 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Why does an exothermic process lead to an increase in entropy?
Replies: 3
Views: 107

Re: Why does an exothermic process lead to an increase in entropy?

Additionally, when exothermic processes release heat, the number of microstates for the surroundings is increased, so entropy still goes up! The second law of thermodynamics stays true.
by Hellen Truong 2J
Sat Feb 03, 2018 9:13 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated
Replies: 9
Views: 347

Isolated

How can an isolated system have a change in temperature but no heat transfer since isolated means no energy or matter exchanged with the surroundings?
by Hellen Truong 2J
Sat Feb 03, 2018 9:11 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: ΔS(universe)
Replies: 6
Views: 226

Re: ΔS(universe)

snehabhargava wrote:The change in entropy of the universe is the same always.


Wait how can this be true? I think my TA said that delta S can be zero for reactions at equilibrium or something like that?
by Hellen Truong 2J
Fri Jan 26, 2018 1:14 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Bomb calorimeter
Replies: 7
Views: 257

Re: Bomb calorimeter

Also, the purpose of a bomb calorimeter being an isolated system is so that heat is not lost to the environment and q rxn can be calculated as negative q calorimeter!
by Hellen Truong 2J
Fri Jan 26, 2018 1:08 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.57 Hess's Law [ENDORSED]
Replies: 3
Views: 332

8.57 Hess's Law [ENDORSED]

How do you find deltaH given enthalpies of combustion? I checked with the solution manual and I was confused about its setup of writing out all the combustion equations and then rearranging them to get the final equation so I keep getting positive 312kj/mol instead of negative.
by Hellen Truong 2J
Fri Jan 26, 2018 12:59 am
Forum: Administrative Questions and Class Announcements
Topic: Week 3 Test Topic is endorsed
Replies: 37
Views: 1807

Re: Week 3 Test Topic is endorsed

what is an example of a conceptual question in terms of internal energy? I think for example he could give you a scenario where the walls between the system and the surroundings are adiabatic. Then, it could be true/false for a series of things like: q=0 True q>0 False delta U = w True delta U = q ...
by Hellen Truong 2J
Sat Jan 20, 2018 2:49 pm
Forum: Phase Changes & Related Calculations
Topic: Change in Internal Energy
Replies: 3
Views: 123

Change in Internal Energy

When you compress a system, is that considered the system doing work or work being done on the system? How does that affect internal energy and how can I remember?
by Hellen Truong 2J
Sat Jan 20, 2018 2:46 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Confusion About One of the Answers to an Example Done in Lecture
Replies: 2
Views: 108

Re: Confusion About One of the Answers to an Example Done in Lecture

To convert from Celsius to Kelvin, you just need to add 273.15, so that's why!
by Hellen Truong 2J
Sat Jan 20, 2018 2:45 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Enthalpy
Replies: 3
Views: 111

Enthalpy

Why is enthalpy related to heat under constant pressure but not constant volume? What is the difference between enthalpy and heat in general?
by Hellen Truong 2J
Sun Jan 14, 2018 12:29 pm
Forum: Phase Changes & Related Calculations
Topic: Heat and work not state functions
Replies: 7
Views: 326

Re: Heat and work not state functions

Are there any other path functions we should know?
by Hellen Truong 2J
Sun Jan 14, 2018 12:28 pm
Forum: Phase Changes & Related Calculations
Topic: Extensive vs Intensive
Replies: 2
Views: 134

Extensive vs Intensive

What is the difference between these two and are there any shortcuts to remember?
by Hellen Truong 2J
Sun Jan 14, 2018 12:27 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law: Method 1
Replies: 3
Views: 181

Re: Hess's Law: Method 1

I think we used enthalpy changes of each step and added them together to demonstrate that enthalpy of a net reaction is additive.
by Hellen Truong 2J
Wed Dec 06, 2017 5:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.25 [ENDORSED]
Replies: 2
Views: 122

Re: 11.25 [ENDORSED]

Also when you write partial pressures, you don't need the brackets because those indicate concentration!
by Hellen Truong 2J
Wed Dec 06, 2017 5:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Factors Affecting K [ENDORSED]
Replies: 2
Views: 148

Factors Affecting K [ENDORSED]

Why don't changes in pressure alter the equilibrium constant?
by Hellen Truong 2J
Mon Nov 27, 2017 4:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.63
Replies: 1
Views: 111

Re: 11.63

The cutoff value is 10^-3 when determining if the reaction tends toward reactants.
by Hellen Truong 2J
Mon Nov 27, 2017 4:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units
Replies: 1
Views: 106

Units

Why can units be ignored during equilibrium constant calculations? Can equilibrium constants still be determined for a system with both solutes and gases?
by Hellen Truong 2J
Wed Nov 22, 2017 2:32 pm
Forum: Hybridization
Topic: Significance of hybridization
Replies: 2
Views: 360

Re: Significance of hybridization

There is also conservation of orbitals. Even when carbon orbitals are hybridized into sp or sp2, there are 2 and 1 p orbitals left over, respectively. The total number of orbitals following hybridization stays the same.
by Hellen Truong 2J
Wed Nov 22, 2017 2:30 pm
Forum: Hybridization
Topic: Hypervalent Hybridization
Replies: 2
Views: 178

Hypervalent Hybridization

How do we visualize the hybridization of something like the sulfur in SO4 2-?
by Hellen Truong 2J
Thu Nov 16, 2017 1:50 am
Forum: Determining Molecular Shape (VSEPR)
Topic: T-shape
Replies: 2
Views: 140

Re: T-shape

One example of T-shape is AX3E2, which has a structure of trigonal bipyramidal, so the lone pairs always go on the equatorial plane because they are separated from the bonded atoms by 90 and 120 degrees. If the lone pairs went on the axial plane, it would only be separated by 90 degrees which is uns...
by Hellen Truong 2J
Thu Nov 16, 2017 1:47 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Benzene Bond Order
Replies: 1
Views: 149

Benzene Bond Order

So in class we discussed how bond order is the average of the bonds because electrons are delocalized. For benzene, is 1.5 the correct bond order? (I divided 6 sigma bonds and 3 pi bonds by 6 carbons to get 1.5 between each carbon)
by Hellen Truong 2J
Sat Nov 11, 2017 1:48 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Isoelectronic [ENDORSED]
Replies: 4
Views: 285

Isoelectronic [ENDORSED]

Are Be2+ and Li+ considered isoelectronic to F-?
by Hellen Truong 2J
Sat Nov 11, 2017 1:46 pm
Forum: Lewis Structures
Topic: HOCO [ENDORSED]
Replies: 3
Views: 239

Re: HOCO [ENDORSED]

To determine the Lewis structure for HOCO, I first counted the electrons to get 17. Then, I linked single bonds so the structure looked like H-O-C-O. I added a double bond between C and the second O and then filled in 2 lone pairs for each oxygen. At this point, 16 electrons have been filled in and ...
by Hellen Truong 2J
Mon Oct 30, 2017 2:48 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 4
Views: 279

Electron Affinity

How do we remember the trend for electron affinity if it doesn't really seem to follow the periodic table? For example, I know that higher electron affinities are usually toward the top right of the table, but chlorine and fluorine already contradict that.
by Hellen Truong 2J
Mon Oct 30, 2017 11:14 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: +/- x meters ? [ENDORSED]
Replies: 2
Views: 204

Re: +/- x meters ? [ENDORSED]

This is also true for uncertainty in speed! On example 1.7, it shows you that you need to double the uncertainty because it is given as +/- 1.0 m/s, so when you plug it into the Heisenberg equation, it should be 2.0 m/s.
by Hellen Truong 2J
Wed Oct 25, 2017 7:35 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s and 3d
Replies: 2
Views: 139

4s and 3d

Why are electrons removed from the 4s orbital first if it is a lower energy and is filled before the 3d orbital is?
by Hellen Truong 2J
Wed Oct 25, 2017 7:33 pm
Forum: Ionic & Covalent Bonds
Topic: Ionization Energy [ENDORSED]
Replies: 5
Views: 245

Re: Ionization Energy [ENDORSED]

To rephrase, ionization energy is the energy an atom needs to form an ion. Ionization energies are specific to elements, but they get higher each successive electron removal because of shielding. After the first electron is removed, all the other electrons experience a stronger pull, so the second i...
by Hellen Truong 2J
Mon Oct 23, 2017 2:35 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Wave Function Solutions
Replies: 1
Views: 112

Wave Function Solutions

I remember in class that a complete set of quantum numbers (n, l, ml) is the solution to the wave function, but how do we visualize what that means without the actual equation? Do we have to know the equation or just understand that it models the electron density of an atom?
by Hellen Truong 2J
Mon Oct 23, 2017 2:33 am
Forum: *Shrodinger Equation
Topic: Double derivative [ENDORSED]
Replies: 3
Views: 265

Re: Double derivative [ENDORSED]

For the wave function, the double derivative helps you understand how either side is related to each other. Because psi is returned on the right side after the equation is performed, you can relate this concept to the way (for example) sinx would return -sinx after you derive it twice. Though the or...
by Hellen Truong 2J
Fri Oct 13, 2017 8:09 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectroscopy vs Photoelectric Effect
Replies: 3
Views: 194

Atomic Spectroscopy vs Photoelectric Effect

I know that the aim of atomic spectroscopy is to measure the energy emitted or absorbed by monitoring photons, and the photoelectric effect studies the kinetic energy contained by electrons after incident light exceeds the work function. Why doesn't the energy added to the atom in atomic spectroscop...
by Hellen Truong 2J
Fri Oct 13, 2017 8:05 pm
Forum: Properties of Electrons
Topic: Wave Properties of Electrons
Replies: 3
Views: 212

Re: Wave Properties of Electrons

Diffraction is when wavelengths of light encounter a narrow opening, and they spread out. This is accompanied by interference if there are multiple narrow openings, causing the new curved wavelengths to hit each other. Destructive interference occurs when the waves are out of phase, or not perfectly...
by Hellen Truong 2J
Sat Oct 07, 2017 9:58 pm
Forum: Empirical & Molecular Formulas
Topic: F11 part B [ENDORSED]
Replies: 2
Views: 222

F11 part B [ENDORSED]

This problem gives percentages anyway, but if a problem were to give me amounts in grams, could I convert to moles and find a ratio that way? Why does the book teach us to find mass percentages and then use a sample mass of 100g?
by Hellen Truong 2J
Sat Oct 07, 2017 9:49 pm
Forum: SI Units, Unit Conversions
Topic: Dimensional Analysis/ Unit conversion [ENDORSED]
Replies: 5
Views: 545

Re: Dimensional Analysis/ Unit conversion [ENDORSED]

My TA showed us this method for dimensional analysis called a ladder! You can easily convert to different units by writing out your "given," and then matching conversion units to it by just writing the units so that they cancel out. Every unit should cancel out diagonally if you match all ...

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