## Search found 52 matches

Sun Mar 17, 2019 12:26 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: porous disk
Replies: 2
Views: 280

### Re: porous disk

Porous disks, or salt bridges, help maintain neutrality in the cell by completing the circuit formed. Electrons flow from anode to cathode, so to keep the cell neutral ions in the salt bridge flow back to the anode.
Sun Mar 17, 2019 12:22 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: voltaic cells
Replies: 2
Views: 295

### Re: voltaic cells

Yes they do. A salt bridge is essentially the same thing as a porous disk if that is confusing.
Sun Mar 17, 2019 12:21 am
Forum: Balancing Redox Reactions
Topic: Agents
Replies: 1
Views: 232

### Re: Agents

The reducing agent is being oxidized, or losing an electron, thus causing the reduction, or lowering in charge. The oxidizing agent is being reduced, because it is lowering charge by gaining an electron.
Sun Mar 17, 2019 12:16 am
Forum: General Science Questions
Topic: sig figs
Replies: 4
Views: 414

### Re: sig figs

Since you have to do the lower number of sig figs, the answer would have one digit.
Sun Mar 17, 2019 12:11 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ice tables
Replies: 3
Views: 284

### Re: ice tables

Yes it is. ICE tables show the concentrations of the reactants and products.
Sun Mar 17, 2019 12:05 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Liquids and Solids
Replies: 2
Views: 264

### Liquids and Solids

I still don't understand: Why do liquids and solids (pure substances) not affect the value of K or Q?
Sun Mar 17, 2019 12:03 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q
Replies: 6
Views: 456

### Re: Q

Q is the reaction quotient, meaning it only depends on the concentrations and not the state that the reactants and products are in.
Sun Mar 17, 2019 12:02 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: free work
Replies: 2
Views: 331

### Re: free work

Gibbs free energy calculates the maximum amount of work that can be done. If G is negative it means work is being done, not work is needed to be done, and in a spontaneous reaction work is done, not needed.
Sat Mar 16, 2019 11:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: galvanic cells
Replies: 6
Views: 465

### Re: galvanic cells

The porous disk is indicated by the two lines: ||
Sun Feb 24, 2019 2:59 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Plugging in
Replies: 2
Views: 122

### Re: Plugging in

For the electrochemical Gibbs free energy equation n represents the number of moles of electrons in the equation.
Sun Feb 24, 2019 2:53 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: inert conductor in cell diagrams
Replies: 3
Views: 117

### Re: inert conductor in cell diagrams

Put the inert conductor in the cell diagram with a phase boundary just as if it were another part of the cell.
Sun Feb 24, 2019 2:44 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Electropositive Metals
Replies: 1
Views: 100

### Re: Electropositive Metals

All metals are electropositive. All non-metals are electronegative. Salts are ionic compounds that form when electropositive metals and electronegative non-metals bond in a neutralization reaction. In water salts are pulled apart into their negative and positive ions, allowing electctrons to flow ma...
Sun Feb 24, 2019 2:39 am
Forum: Balancing Redox Reactions
Topic: Test 2 Material
Replies: 13
Views: 503

### Re: Test 2 Material

Test 2 covers everything before the Nernst equation. So yes it will have redox reactions.
Sun Feb 24, 2019 2:36 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Standard Gibbs Free Energy
Replies: 1
Views: 84

### Re: Standard Gibbs Free Energy

Standard free energy is calculated under standard-state conditions (everything at 1 atm, 20 degrees celcius etc.) These values are experimentally determined. The substances are "pure" in that it should be just them, and that standard free energy is calculated at whatever state they're in a...
Sun Feb 24, 2019 2:29 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Concepts
Replies: 2
Views: 96

### Re: Concepts

Gibbs Free Energy is what really determines spontaneity: If ∆G is negative then the reaction is spontaneous. If it's positive the reaction is non-spontaneous. Here's how to relate entropy and enthalpy to spontaneity: ∆G positive, ∆ H negative - Spontaneous at all temperatures ∆G positive, ∆H positiv...
Sun Feb 10, 2019 10:51 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: Reversible vs. Irreversible
Replies: 6
Views: 229

### Re: Reversible vs. Irreversible

You get more work done in a process that releases heat slowly, since less heat is lost to the surroundings. Reversible processes are infinitely slow, and therefore do the maximum amount of work.
Sun Feb 10, 2019 10:42 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity
Replies: 4
Views: 156

### Re: Heat Capacity

Yes it can to convert.
Sun Feb 10, 2019 10:40 pm
Forum: Calculating Work of Expansion
Topic: Volume and Entropy
Replies: 2
Views: 104

### Re: Volume and Entropy

The larger the volume the more ways there are to arrange the molecules, therefore entropy increases as volume increases.
Sun Feb 10, 2019 10:36 pm
Forum: Calculating Work of Expansion
Topic: Pv=nrT
Replies: 2
Views: 109

### Re: Pv=nrT

deltanRT is used when the pressure isn't constant. PnRT is used for constant pressure.
Sun Feb 10, 2019 10:29 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific heat
Replies: 3
Views: 155

### Re: Specific heat

Specific heats are calculated through experimentation. So we should be given any specific heat we need.
Sun Feb 10, 2019 10:10 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Which does more work?
Replies: 3
Views: 111

### Re: Which does more work?

In class the isothermal examples were all irreversible. Reversible reactions are always do the maximum work because they are done more slowly (infinitely slow) and less heat is lost to the surroundings.
Tue Jan 29, 2019 2:32 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity
Replies: 5
Views: 180

### Re: Heat Capacity

It should be made very clear whether or not you are looking for heat capacity or specific heat capacity. If units of mass are given at any point in a problem then you are probably looking for specific heat capacity.
Tue Jan 29, 2019 2:26 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Thermal Equilibrium
Replies: 5
Views: 152

### Re: Thermal Equilibrium

Just like with chemical equilibrium thermal equilibrium is dynamic. This means a that heat is going into the surroundings and the system, and thermal equilibrium is released after the rate at which heat exchange is occuring is equal.
Tue Jan 29, 2019 2:24 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: When to use which method for calculating reaction enthalpies
Replies: 4
Views: 122

### Re: When to use which method for calculating reaction enthalpies

Bond Enthalpies: Generally you do not want to use this method as it is unreliable. I'm actually not totally sure when you'd use this method. Hess's Law: Remember Hess's Law is about adding enthalpies. You'll use this in problems involving the enthalpies of multiple reactions. Standard Enthalpies: Yo...
Tue Jan 29, 2019 2:16 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: K versus C*
Replies: 2
Views: 99

### Re: K versus C*

Specific heat capacity looks at the energy change, not at temperature change. If the temperature changes by 1 degrees on either scale, the change in energy is the same per unit of mass (whatever that is). This was confusing to me at first in lecture, but what you need to pay attention to more is the...
Tue Jan 29, 2019 2:10 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimetry
Replies: 5
Views: 237

### Re: Calorimetry

The first kind that was gone over in lecture (two styrofoam cups) was a constant pressure calorimeter. The bomb calorimeter is one in which the volume is kept constant. It's called a bomb calorimeter because they are more prone to explosions as the pressure changes, but not the volume, leading to hi...
Tue Jan 29, 2019 2:07 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 7
Views: 246

### Re: Bond Enthalpies

Because of the way bonds work (dipole moments, random movement of shared electrons etc.) there is no single enthalpy for pretty much any non diatomic bond. bond enthalpies are calculated by taking the average of many different bonds of a particular kind.
Sun Jan 13, 2019 11:57 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and K considered different
Replies: 2
Views: 97

### Re: Q and K considered different

K is the constant for the equation at equilibrium . This is what you want the Q, which is the reaction quotient, to be. The reaction quotient determines the direction of the reaction, more product or more reactants. Q is experimentally determined for a particular stage of the reaction, and when it m...
Sun Jan 13, 2019 11:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Inert Gases
Replies: 2
Views: 92

### Re: Inert Gases

I think unfortunately a gas being inert has to be experimentally determined. As a general rule noble gases are usually inert if present, but to truly know requires experimentation.
Sun Jan 13, 2019 11:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Actual Yield of Products
Replies: 2
Views: 96

### Re: Actual Yield of Products

No it isn't. Adding more reactants will still lead to a stabilization of the reaction in which there is a dynamic equilibrium, with both products and reactants. That's simply the way these reactions are.
Mon Dec 03, 2018 12:05 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: DNA
Replies: 1
Views: 71

### Re: DNA

The acidity in DNA comes from the phosphate groups that are found in it. The acidity from this is countered slightly by the bases in the nucleotides, but since those bases are weak bases DNA is overall acidic.
Mon Dec 03, 2018 12:00 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Net Dipole
Replies: 1
Views: 329

### Re: Net Dipole

Yes. Technically there is an electronegativity difference, and due to the shape (pyramidal), and chlorine being more electronegative, there is a dipole towards the chlorine.
Sun Dec 02, 2018 11:53 pm
Forum: Hybridization
Topic: tetrahedral
Replies: 5
Views: 222

### Re: tetrahedral

The type of hyrbrid orbital is named after the number of p orbitals that are needed for the central atom to have the right amount of bonds. An sp3 hybrid orbital is 1 s orbital and the three p orbitals of the same energy level (sp2 would be one s orbital and 2 p orbitals). because the central atom b...
Sun Dec 02, 2018 11:47 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligand Names
Replies: 2
Views: 120

### Re: Ligand Names

If you mean by how many sites the ligand bonds at then yes you should know that bonding at one, two, three, and six sites are monodentate, bidentate, teidentate and hexodentate respectively. Other terms we saw in the lecture refer to names of specific molecules.
Sat Nov 10, 2018 5:42 pm
Forum: Resonance Structures
Topic: Bond Lengths
Replies: 6
Views: 589

### Re: Bond Lengths

Calculating exact bond lengths probably relies on information we won't learn in Chem 14A, so you will not need to know exact bond lengths. All you really need to know is which ones are longer (single bonds) and which are shorter (triple bonds) and how valence structures have bond length in between t...
Sat Nov 10, 2018 5:40 pm
Forum: Ionic & Covalent Bonds
Topic: Relation between strong acid and weak bond
Replies: 3
Views: 195

### Re: Relation between strong acid and weak bond

Lewis acids accept electrons, so a weaker bond means that it is easier for that hydrogen bond to be broken. Iodine is larger than the other atoms and therefore the bond between it and hydrogen is weaker, making it a stronger electron acceptor, or a stronger acid.
Sat Nov 10, 2018 5:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Remembering VSEPR
Replies: 2
Views: 121

### Re: Remembering VSEPR

The most important thing to remember is that the electrons are repelling each other and wan to be as far from each other as three dimensions will allow them to be. So whatever number of atoms you have just arrange them so that they are the largest angle apart from each other as possible. As for the ...
Mon Nov 05, 2018 5:05 am
Forum: Electronegativity
Topic: Ionization Energy over Electronegativity?
Replies: 4
Views: 241

### Re: Ionization Energy over Electronegativity?

Ionization energy tells how likely an atom is to share an electron, and the atom most likely to share electrons is the one that is going to form the most bonds in a compound.
Mon Nov 05, 2018 5:00 am
Forum: Lewis Structures
Topic: Extra electrons
Replies: 3
Views: 163

### Re: Extra electrons

If I'm understanding your question right, your asking what's the greatest number of atoms a central atom that's part of an expanded octet, where there are more than 8 valence electrons, can have. Most importantly, expanded octets have enough electrons to keep all atoms at the lowest possible energy ...
Mon Nov 05, 2018 4:42 am
Forum: Resonance Structures
Topic: Bond Lengths
Replies: 7
Views: 386

### Re: Bond Lengths

NO3 2- has resonance, meaning that the double bond in it can be between any of the three oxygens and the nitrogen atom. It has been experimentally determined for the N-O bonds in NO3 for example that they are all 124 pm, in between the single bond length of 140 pm and the double bond length of 120 p...
Sun Oct 28, 2018 11:55 pm
Forum: Ionic & Covalent Bonds
Topic: Octet Rule Guideline
Replies: 3
Views: 145

### Re: Octet Rule Guideline

What this is referring to is how the number of valence electrons an atom has determines how many bonds it can make. Because covalent bonds are the sharing of valence electrons, the number of valence electrons an atom already has determines the number of bonds it can make to achieve an octet. For exa...
Sun Oct 28, 2018 11:51 pm
Forum: Lewis Structures
Topic: Identifying the Charge
Replies: 2
Views: 100

### Re: Identifying the Charge

I'm not exactly sure what you're asking, but I think the answer to your question is that sometimes the molecule itself is an ion, and so after adding up the charges of the atom's themselves, you have to subtract or add electrons based on the charge (i.e. if its a 2+ molecule you have to remove 2 ele...
Sun Oct 28, 2018 11:48 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Balmer series, Lyman series?
Replies: 3
Views: 222

### Re: Balmer series, Lyman series?

According to my TA, and I think professor Lavelle as well, all you need to know is that the Balmer series is the series of spectra produced when the electron's final resting place is in the second energy level (n=2), while in the Lyman series the electron's final resting place is the first energy le...
Sun Oct 21, 2018 11:40 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron Spin States?
Replies: 4
Views: 87

### Re: Electron Spin States?

This is really a much more advanced topic that we don't need to know. But electron spin does ultimately affect the spectra produced. The spin's magnetic moment affects how the atom interacts with magnetic fields.
Sun Oct 21, 2018 11:37 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Module Question 27
Replies: 2
Views: 156

### Re: Photoelectric Effect Module Question 27

In order to find the energy per photon, you just need to know the frequency of the radiation. You only need to use E=h*v. This formula gives you the energy per photon. The answer you should get is around 19.88*10^-19 (E= h(*6.626*10^-34) * v(3.00*10^15). Or E=1.99*10^-18.
Sun Oct 21, 2018 11:21 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals on the test
Replies: 6
Views: 241

### Re: Orbitals on the test

According to my TA and what I remember from Lavelle, we will only need to know what quantum numbers each orbital is represented by. We will not need to draw any and we don't even need to know the orientation (only that a particular quantum number means a particular orientation). Really just focus on...
Sun Oct 14, 2018 11:58 pm
Forum: Properties of Light
Topic: Experiments and Equations
Replies: 3
Views: 73

### Re: Experiments and Equations

Technically we don't. I don't think we're gonna have questions on the scientists and their experiments like in high school. However from experience I can tell you that understanding the experiments can help a lot with understanding concepts.
Sun Oct 14, 2018 11:56 pm
Forum: Photoelectric Effect
Topic: Threshold Energy
Replies: 2
Views: 68

### Re: Threshold Energy

In a way yes. the photons that don't have enough energy to remove an electron end up heating up the surface of the metal.
Sun Oct 14, 2018 11:50 pm
Forum: Photoelectric Effect
Topic: Photoelectric effect and atomic spectra difference
Replies: 3
Views: 139

### Re: Photoelectric effect and atomic spectra difference

Atomic spectra shows the frequencies of electromagnetic radiation that a particular atom has the ability to emit as an electron changes energy levels. The photoelectric effect has nothing to do with the types of EM radiation, rather it deals with the energy it takes to remove an electron from the at...
Fri Oct 05, 2018 5:10 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: diatomic elements
Replies: 12
Views: 1903

### Re: diatomic elements

The reason these elements are diatomic is because they don't have enough electrons to fill up their valence shells. Thus, they cannot exist as a single atom.
Fri Oct 05, 2018 5:01 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: 6th edition: E15
Replies: 2
Views: 125

### Re: 6th edition: E15

What you need to do is determine what the metal, M, is by using the molar mass given. Then you need to find the molar mass of MS2, the metal and the sulfide bonded.
Fri Oct 05, 2018 4:57 am
Forum: General Science Questions
Topic: Significant figures / decimal places in intermediate steps in calculations
Replies: 4
Views: 255

### Re: Significant figures / decimal places in intermediate steps in calculations

While is may be better to limit your significant figures in intermediate steps to the number originally given, I personally try to include as much of the actual numbers as possible. The final answer must have the proper number of significant figures, however it also needs to be as accurate as possib...