## Search found 66 matches

Fri Mar 16, 2018 9:19 am
Forum: Calculating Work of Expansion
Topic: Irreversible Expansion vs. Reversible Expansion
Replies: 2
Views: 359

### Re: Irreversible Expansion vs. Reversible Expansion

Usually the problem will tell you directly, but if not: If the problem gives you a constant external pressure, the expansion should be irreversible; but if the pressure is increasing in miniature steps, the expansion should be reversible. Irreversible has a noticeable difference between the internal...
Fri Mar 16, 2018 9:12 am
Forum: *Alkanes
Topic: Organic Molecules in general
Replies: 1
Views: 504

### Re: Organic Molecules in general

I think there are exceptions to the rules, such as radicals where there is an extra electron on the carbon or where carbon forms 5 bonds instead of 4. But yea, for the sake of this class, I think we assume there are always 4 bonds on the carbon atoms.
Thu Mar 15, 2018 11:10 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.79
Replies: 1
Views: 158

### Re: 15.79

From the equation where ln k = Ea/ RT + ln A, we can see that activation energy and temperature are directly related provided all other things constant. Therefore, the product that forms more at higher temperatures has a higher activation energy. a) If higher temp = higher activation energy, the sec...
Wed Mar 14, 2018 9:13 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: H2O in rate law/15.101
Replies: 1
Views: 124

### Re: H2O in rate law/15.101

I think so. Provided the solution is diluted (or there is a lot more water than the other reactant), the change in H2O is considered to be too small in comparison to its initial concentration, and thus the change in concentration of H2O is taken as zero.
Mon Mar 12, 2018 10:02 pm
Forum: *Enzyme Kinetics
Topic: Temperature and rate constants
Replies: 2
Views: 293

### Re: Temperature and rate constants

ln k = -EA/(RT) + ln A is the equation for this relationship. The two variables are directly related, so increasing temperature results in a larger k and vice versa. This makes sense as a higher k means the reaction occurs at a faster rate, and a higher temperature results in more collisions resulti...
Mon Mar 05, 2018 11:46 pm
Forum: Zero Order Reactions
Topic: slope
Replies: 3
Views: 370

### Re: slope

Since the reaction rate does not depend on concentration, the concentration of the reactants will decrease at a steady rate no matter what for a given duration until there is no reactant left or the reaction meets some different condition that affects its rate. The rate at which the concentration de...
Mon Mar 05, 2018 11:41 pm
Forum: General Rate Laws
Topic: Concentration and Rate Relationship
Replies: 4
Views: 282

### Re: Concentration and Rate Relationship

I think so. This can be shown mathematically. Lets say rate = k[A]^2 If A is doubled, rate = k[2A]^2 = 4k[A]^2, meaning rate was quadrupled in rate = k[A][B] k[2A][2B] = 4k[A][B] Though in the second reaction, if you only double A or B, the rate only doubles k[2A][B] = 2k[A][B] This has to do with h...
Mon Mar 05, 2018 10:37 pm
Forum: First Order Reactions
Topic: 15.29
Replies: 3
Views: 333

### Re: 15.29

a) To find the rate constant k, we must use the rate law for a first order reaction. From the integrated law, we can find that k = ln(A initial / A at t)/t From there, the only unknown variable is At, which can be solved using stoichiometry. A decreases by a third of B produced, thus At = A0 - B for...
Mon Mar 05, 2018 8:28 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: What is Molecularity?
Replies: 9
Views: 1231

### Re: What is Molecularity?

More specifically, molecularity is the number of species that must collide for a step in the chemical reaction to proceed, not just the total amount of reactants forming a product. This tells us the rate of a step in a chemical reaction. or using the rate of the step in the reaction, we can find the...
Sun Mar 04, 2018 2:46 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Purpose of intermediate?
Replies: 2
Views: 172

### Re: Purpose of intermediate?

The intermediate shows how the reaction actually occurs in nature. You could think of it as another chemical reaction that needs to take place before the observed reaction occurs. As in the example in class, we observe the reaction: NO2 + CO -> NO + CO2 However, since we know the rate of reaction is...
Sun Mar 04, 2018 2:38 pm
Forum: General Rate Laws
Topic: Rate Law
Replies: 3
Views: 242

### Re: Rate Law

The rate law shows how the concentration of the reactants are changing over time. If the reactants are being consumed to form products, then the reactants must be decreasing. Therefore, the rate at which the concentration of reactants are changing over time must be negative.
Sun Mar 04, 2018 2:36 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.23?
Replies: 3
Views: 233

### Re: 15.23?

Just to clarify, in a reaction where 2A -> B + C, if B is increasing by 0.034 (assuming B initial = 0), then A must decrease by 0.034 * 2 since the reaction requires 2 A to be converted into B. As A initial = .134 and the change in A is -0.034 * 2, A at time t is .134 - 2 * 0.034. Of course, C can b...
Wed Feb 28, 2018 2:34 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: units of K
Replies: 5
Views: 308

### Re: units of K

The units do change based on the order:
EDIT: this post did it better I think
https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=5287
Wed Feb 28, 2018 9:45 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Dependence on Concentration
Replies: 2
Views: 186

### Re: Dependence on Concentration

Other than that, they aren't really related. The equilibrium constant is just the ratio of which products and reactants will be when the reaction is at equilibrium. The rate constant affects how fast the reaction will occur based on the concentrations of the reaction (depending on the order of the r...
Wed Feb 28, 2018 9:23 am
Forum: General Rate Laws
Topic: Orders of Reactions
Replies: 1
Views: 149

### Re: Orders of Reactions

The reaction order tells us what is required for the reaction to occur, or how the concentrations will affect the rate of the reaction. 0 order: Concentrations of the reactants don't affect the rate of the reaction; therefore, the rate will occur at a constant provided all other factors are held the...
Sun Feb 25, 2018 10:10 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell Potential
Replies: 4
Views: 245

### Re: Cell Potential

I read that the potential of hydrogen is set as zero to set a standard to which other cells can be compared to (positive or negative). Not sure if this is completely accurate but it seems like it makes sense.
Hope that helps
Sun Feb 25, 2018 8:18 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: NERNST
Replies: 4
Views: 282

### Re: NERNST

Sadly you cant use ln, as the constant ratio from ln to log was used to find the constant. It would be a different constant if you are using ln instead of log.
EDIT: ^^^
Sun Feb 25, 2018 8:13 pm
Forum: First Order Reactions
Topic: Negative Rates
Replies: 4
Views: 330

### Re: Negative Rates

If the rate is negative for the reactant after doing the math, that means it is increasing over time. I think in that case you would switch the chemical equation around, as the reactants become the product and the product become the reactants.
I hope that makes sense
Sun Feb 25, 2018 3:06 pm
Forum: Zero Order Reactions
Topic: zero order slopes
Replies: 5
Views: 332

### Re: zero order slopes

Since zero order reactions occur at a constant rate independent of the concentration, the rate of the reaction will not change with time or concentration as long as the reaction can continue. Therefore, the slope should be zero.
Wed Feb 14, 2018 3:12 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Boiling point at room temperature
Replies: 5
Views: 278

### Re: Boiling point at room temperature

If you are trying to find the boiling point of water at room temperature, the water must first be at room temperature. From there, you can calculate (I don't know how) the other various, non-standard conditions to allow this to be true, like a rapid change in pressure.
Tue Feb 13, 2018 10:18 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: irreversible system
Replies: 1
Views: 160

### Re: irreversible system

I think in that problem they are holding w= 0 to be true for both the system and the surroundings. Might've been misinterpreted.
Tue Feb 13, 2018 10:09 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Boiling point at room temperature
Replies: 5
Views: 278

### Re: Boiling point at room temperature

If you are talking about the case in which water will boil at lower temperatures due to extremely low pressures, it is more like you are trying to find the atmospheric pressure than the temperature.
Otherwise, it doesn't really make sense, since water of course won't usually boil at room temperature.
Sun Feb 11, 2018 4:39 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: equilibrium
Replies: 3
Views: 240

### Re: equilibrium

If the reaction is at equilibrium, meaning there is no biased for the electron to move from reactant to product, there is no voltage and E = 0.
EDIT: ^^ beat me to it
Sun Feb 11, 2018 1:41 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: 9.75
Replies: 1
Views: 160

### Re: 9.75

I'm no expert, but polarity occurs only through the structure of the molecule, so I would think it would be more accurate to show increased entropy through structure. I don't think polarity is really related to entropy of a single molecule except in that it is related to structure. Stability in term...
Sun Feb 11, 2018 1:02 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: Problem 9.77
Replies: 1
Views: 254

### Re: Problem 9.77

b) This like calculating possible combinations. If there are 6 atoms, there are 12 unique combinations in which 2 atoms of the 6 have the energy. Visual representation below. EDIT: wait shouldn't the answer be 15? c)Basically, it is asking how energy will flow between the two systems in part b. The ...
Thu Feb 01, 2018 5:43 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: sign of q
Replies: 7
Views: 450

### Re: sign of q

Qrev is the heat being transferred into or out of the system. If heat is leaving the system, the q would be negative. If heat enters the system, then q is positive. This makes sense since if there is more energy in the system, you can expect there to be an increase in entropy.
Thu Feb 01, 2018 5:39 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Chapter 9 Problem 115
Replies: 1
Views: 137

### Re: Chapter 9 Problem 115

Pure solids and liquids aren't included in chemical equilibrium equations themselves, but an aqueous solid or liquid is, therefore removing an aqueous product will result in the reaction favoring the formation of products. I think you just got tripped up in that aqueous molecules are also included i...
Wed Jan 31, 2018 12:44 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.9
Replies: 3
Views: 196

### Re: 9.9

For ideal gases, all the energy is in the kinetic energy of the particles. Temperature is basically a measure of the average kinetic energy of the molecules. Isothermal means there is no change in temperature, and if there is no change in temperature, there must be no change in total kinetic energy....
Sat Jan 27, 2018 7:23 pm
Forum: Phase Changes & Related Calculations
Topic: 8.40
Replies: 4
Views: 257

### Re: 8.40

Sat Jan 27, 2018 7:18 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy and Gravity
Replies: 1
Views: 163

### Entropy and Gravity

How does gravity obey the second law of thermodynamics if its a force that attracts all things with mass together, meaning less possible positions? Is this due to an increase in heat created by gravity?
Sat Jan 27, 2018 7:05 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.12 Textbook Example : Calculating the total entropy change for the expansion of an ideal gas
Replies: 1
Views: 97

### Re: 9.12 Textbook Example : Calculating the total entropy change for the expansion of an ideal gas

a) Since the reaction is isothermal, there is no net change in internal energy. For that gas inside the piston (the system), you can expect an increase in entropy due to the volume increasing. If volume increases, the molecules have more possible positions, and therefore greater entropy. For the sur...
Fri Jan 19, 2018 11:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Difference between a lattice enthalpy and lattice energy
Replies: 1
Views: 2606

### Re: Difference between a lattice enthalpy and lattice energy

Lattice energy can be measured as the amount of energy required to break a bond between solid ions into a gas. Lattice enthalpy is the enthalpy change from when the solid structure is formed or broken. Basically, one is to measure the energy of the bond while the other measures the change in enthalp...
Fri Jan 19, 2018 11:10 pm
Forum: Phase Changes & Related Calculations
Topic: Change in enthalpy and change in internal energy
Replies: 2
Views: 129

### Re: Change in enthalpy and change in internal energy

From my understanding, enthalpy is a state function and entails more information than internal energy. Change in internal energy includes the work done on or by the system along with the amount of heat transferred in or out of the system. Enthalpy is the internal energy of the system along with the ...
Fri Jan 19, 2018 10:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpies [ENDORSED]
Replies: 3
Views: 149

### Re: Enthalpies[ENDORSED]

For Hess's Law: you must know the total energies produced by at least two different reactions which can be combined due to similar reactants or products. For Bond Enthalpies: you need the enthalpies of each bond in all the reactants and products For Standard Enthalpies of Formtation: is kinda betwee...
Fri Jan 19, 2018 10:38 pm
Forum: Calculating Work of Expansion
Topic: 8.25
Replies: 1
Views: 100

### Re: 8.25

In the first part of the problem, you find the heat capacity (the kilojoules required to raise the whole calorimeter by a degree kelvin), which is a ratio that can be applied to all reactions in that specific calorimeter where there is a change in temperature. This unlike specific heat capacity wher...
Fri Jan 12, 2018 11:40 am
Forum: Administrative Questions and Class Announcements
Replies: 2
Views: 180

Since we are using the same textbook, and the solutions manual provides the answers to all odd problems in the textbook, I think we can use the same one.
Fri Jan 12, 2018 11:35 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Ideal Gases
Replies: 1
Views: 132

### Re: Ideal Gases

Ideal gases are hypothetical in that all collisions between gas molecules are perfectly elastics and no energy is lost to collisions with the container, thus no energy can be lost (if nothing about the system is changing). Of course, the energy of an ideal gas can change depending on the problem Mos...
Fri Jan 12, 2018 11:23 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Vibrational Energy?
Replies: 1
Views: 154

### Re: Vibrational Energy?

I think the influence of potential energy (or the position) on an atom is similar to spring and pendulum physics, depending on the direction the atom is vibrating. When the atom is vibrating towards and away from the other atoms, then it is similar to spring oscillations in physics. When the atom ha...
Thu Dec 07, 2017 11:32 am
Forum: Bronsted Acids & Bases
Topic: Neutralization reactions
Replies: 2
Views: 245

### Re: Neutralization reactions

I think a neutralization reaction is whenever a base and acid react to form a salt and water, usually in an aqueous solution. Bases dissociate between some +ion and OH- while acids dissociate to some -ion and H+. The ions of the acid and base combine to form a salt (which is usually more stable than...
Thu Dec 07, 2017 11:22 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong Bases
Replies: 1
Views: 204

### Re: Strong Bases

The strongest base will have a pH of 14, but through calculating K a , not K b . When calculating Ka, you are measuring the amount of H30+ ions there are in the solution. The more the H30+, the smaller the pH, and the more acidic the solution gets. Kb, on the other hand, is the opposite in that it c...
Wed Nov 29, 2017 2:47 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Energy levels
Replies: 2
Views: 291

### Re: Energy levels

I don't quite understand whats being asked, but if you mean orbitals they are the same.
N = [He]2s2 2p3
O = [He]2s2 2p4
F = [He]2s2 2p5

First number is energy level and second is the number of electrons in that orbital
Wed Nov 29, 2017 2:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.89 Part b
Replies: 2
Views: 274

### Re: 11.89 Part b

I saw this too and thought it might be a typo (since kPa = 1000 Pa, so convert to Pa). Since pascals are the SI unit for pressure (newtons per square meter), I wonder why they changed it to bar instead of the base pascal? (the answers will be different since the unit changes don't cancel out).
Wed Nov 29, 2017 2:36 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 11.89 part a
Replies: 1
Views: 168

### Re: 11.89 part a

You have the least of B, so it probably has the smallest coefficient and is a good place to start. It has a value of 5. B = 5. From there, C has twice as much product created than B, so the ratio from B to C is 1:2. Therefore, C's coefficient must be twice as much as B's. (as you can see it is 10). ...
Mon Nov 27, 2017 12:00 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 11.37
Replies: 3
Views: 292

### Re: 11.37

edit: ^ they got it a) is the inverse of the equation given, meaning the products and reactions switch. Therefore, the products become the reactants and the reactants become the products, and switch in the equation K = P/R. Therefore, K in this equation becomes the inverse of the first equation. Ma...
Sun Nov 26, 2017 11:30 pm
Forum: Naming
Topic: Oxidation Numbers
Replies: 2
Views: 204

### Re: Oxidation Numbers

edit: ^ sums it up The numerals represent how many electrons the metal atom lost. Oxidation is simply the loss of electrons, thus it is called oxidation number. To find the oxidation number, you need to look at the total charge of the atom(s) or molecule(s) attached to the metal. In the example giv...
Sun Nov 26, 2017 9:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.45 part c
Replies: 1
Views: 124

### Re: 11.45 part c

Stability means that the molecule is less likely to dissociate, or less likely to become un-bonded. That means in the given reactions, (CL2 -> 2CL or F2 -> 2F) the more stable molecule will have more of the reactant (the bonded molecule), and therefore a lower Kc since Kc is product divided by react...
Sun Nov 26, 2017 9:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium
Replies: 1
Views: 179

### Re: Chemical Equilibrium

Alright so if 60% of the initial hydrogen reacts, 40% of the hydrogen in the concentration remains , meaning the final concentration of hydrogen is 40% of the initial concentration. Final = .4 * initial Therefore initial = .133 (as you calculated) final = .4 * .133 FOR HYDROGEN The change in concent...
Wed Nov 08, 2017 11:47 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Post Module #18
Replies: 2
Views: 221

### Re: Post Module #18

So we know the equation for uncertainty: ΔpΔx >= h/4π Given a distance (Δx) and Δp = m * Δv (since velocity is the only thing that is uncertain about a momentum, mass is known) we can derive 1. Δv >= h/( 4π * Δx * m) 2. The Δx of an electron is said to be within 1% of .05 nm, thus .01 * .05 * 10^-9 ...
Wed Nov 08, 2017 10:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Memorizing VSEPR
Replies: 2
Views: 704

### Re: Memorizing VSEPR

As far as memorization goes, I think the best method for learning anything is quiz and recall. If you really want to, I'd make (or look up) flashcards of the different types of shapes (one side name, other shape) and try quizzing yourself whenever you can, even in between classes, until you got it d...
Wed Nov 08, 2017 12:16 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Post Assessment Module #42
Replies: 1
Views: 185

### Re: Post Assessment Module #42

1. Through the emitted photon, we can figure out the net change of energy of the electron. E = hv 2. Using this energy, we have all the variables for the E = -RH/n^2[initial] - (-RH/n^2) [final] but must solve for n [initial] We know that the energy level must have gone from a higher number to 4 bec...
Sat Nov 04, 2017 11:30 pm
Forum: Lewis Structures
Topic: Lewis Structure
Replies: 4
Views: 1217

### Re: Lewis Structure

For now, I think it’s just a general rule for making Lewis dot structures. The reason is most likely due to the lower ionization atom more easily gives away or share electrons. They also usually have more unpaired electrons (seen in the electron config) that can be paired for bonding. (N has 3 while...
Sat Nov 04, 2017 5:10 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Why does the Cu2+ ion form?
Replies: 1
Views: 358

### Re: Why does the Cu2+ ion form?

I hope this is right. It is explained through Jahn - Teller distortion. In certain configurations, Cu(II) is more stable due to its distorted octahedral shape. Basically, the other atoms around it determine which form of copper is more stable. I think larger elements, especially metals, require more...
Sat Nov 04, 2017 4:26 pm
Forum: Lewis Structures
Topic: Lewis Structure
Replies: 4
Views: 1217

### Re: Lewis Structure

http://wtt-pro.nist.gov/wtt-pro/image.png?cmp=chlorine_nitrate Chlorine nitrate right? We'll probably learn this later, but since it is written as ClONO2 in this case instead of CLNO3 to make it easier for us, you can think of it as CLO bonding with NO2. CLO bonds to create a full octet plus 2 elec...
Sat Nov 04, 2017 3:55 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Poloarizability
Replies: 2
Views: 287

### Re: Poloarizability

An electron cloud is the regions in which the different electrons in an atom occupy (usually seen as all the orbitals together to make a "cloud" of electrons around the nucleus). I think so; the more distorted cloud will always be the anion since it has a net negative charge while the cati...
Sun Oct 29, 2017 1:52 pm
Forum: Trends in The Periodic Table
Topic: Electron affinity
Replies: 1
Views: 161

### Re: Electron affinity

[edited] Yes, I think its because the electron and atom both become more stable. Since the electron fills the atom's outer shell/orbital, the atom itself becomes more stable. For the electron, you could think of it as the different energy states (n = 1, n = 2, etc). When the electron enters the atom...
Tue Oct 24, 2017 9:51 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Difference between orbital, shell, and subshell?
Replies: 2
Views: 1192

### Re: Difference between orbital, shell, and subshell?

You could think of it this way: in Schrodinger's wave function formula, the shell is n, the orbital are the different l, and the suborbital are the different m. Basically, the shell is all of the orbitals at a certain energy state, the orbitals are the "shapes" in the shell (s, p, d, f), a...
Sun Oct 22, 2017 9:37 pm
Topic: Stefan-Boltzmann Law
Replies: 3
Views: 483

### Re: Stefan-Boltzmann Law

I think the confusion is with intensity. Intensity does relate to the energy given off by an object emitting light, just not the individual photons within the light. When the intensity increases, the individual photons may or may not be increasing in energy, but the amount of photons is increasing. ...
Sun Oct 22, 2017 8:59 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Chapter 2 #25 and #29 [ENDORSED]
Replies: 2
Views: 321

### Re: Chapter 2 #25 and #29[ENDORSED]

Sorry my last post was the wrong questions, fixed now. Any specific concepts in particular? Anyways, #25: a) In any p orbital, no matter what n (or energy) it is, there can be 6 electrons in it. You can look at the quantum numbers to figure this out. n doesn't matter; l = 1 for P; thus m can be 1, 0...
Tue Oct 10, 2017 1:46 pm
Forum: General Science Questions
Topic: Covalent Bonds
Replies: 3
Views: 540

### Re: Covalent Bonds

Welp in case anyone cares, the reason electrons tend to pair up and chemically bond in atoms with un filled orbitals despite being without charge is that they can. If a lone hydrogen atom with one electron meets another, the electrons will be able to jump between each other’s orbitals when the orbit...
Tue Oct 10, 2017 1:23 pm
Forum: Einstein Equation
Topic: How does E = hv lead to Einsteins equation E=MC2?
Replies: 4
Views: 2086

### Re: How does E = hv lead to Einsteins equation E=MC2?

Can someone explain the theory behind these equations? I don't understand what the photon energy is used to represent or what chemistry theories are represented. E = hv or better seen on the computer as hf (Plancks equation) shows that if the frequency of a wave (light) increases, the amount of ene...
Tue Oct 10, 2017 12:36 pm
Forum: DeBroglie Equation
Topic: Chapter 1 #33 a [ENDORSED]
Replies: 1
Views: 219

### Re: Chapter 1 #33 a[ENDORSED]

So to find lambda (wavelength), you just need mass since velocity and h is known. The mass of an electron is also a constant, 9.1x10^-31 kg (google). Then, just plug in. (Convert km/s to m/s) 6.626x10^-34 (m^2 kg / s) / (9.1x10^-31 kg * 3.6x10^6 m/s. Should give answer in meters. Sorry for lengthy e...
Tue Oct 10, 2017 12:15 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molar Mass and Atomic Mass
Replies: 3
Views: 356

### Re: Molar Mass and Atomic Mass

I think we use molar mass for conversions because it is the average mass per mole of commonly found isotopes of that element. Atomic mass is specific to one isotope, and is the number of protons and neutrons in that one atom. Basically, molar mass is an average that can be used as a basis for conver...
Tue Oct 10, 2017 10:18 am
Forum: Properties of Light
Topic: Chapter 1, problem 3 [ENDORSED]
Replies: 10
Views: 895

### Re: Chapter 1, problem 3[ENDORSED]

The electric, or magnetic, fields are the reason we draw light as waves. We do this to simplify the image of light so that we do not have to draw both fields, as it is much easier to draw one wave rather than two in a 2D plane (since the electric and magnetic fields are perpendicular to each other)....
Fri Oct 06, 2017 5:17 pm
Forum: General Science Questions
Topic: Covalent Bonds
Replies: 3
Views: 540

### Re: Covalent Bonds

Ah that makes sense. I guess my question is more specifically what causes atoms to require their valence levels to be "full" when normally the atoms would repel each other, like when some elements desire to share electrons while others receive electrons (is there a specific forces)?
Fri Oct 06, 2017 11:05 am
Forum: General Science Questions
Topic: Covalent Bonds
Replies: 3
Views: 540

### Covalent Bonds

I understand from a physics standpoint that atoms which are held by ionic bonds are pulled together through electromagnetic forces, but what force holds covalent bonded atoms together, such as H2? Or rather, what makes sharing electrons amongst atoms with free valence electrons pull these atoms toge...
Fri Oct 06, 2017 10:55 am
Forum: SI Units, Unit Conversions
Topic: Derived Units
Replies: 4
Views: 413

### Derived Units

Should derived units, such as molar mass, be written using the SI units, or does it not matter which units we use in our work as long as the final answer is in SI units?