Search found 76 matches

by Helen Struble 3B
Sun Feb 16, 2020 5:56 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal reversible of ideal gas
Replies: 4
Views: 21

Re: Isothermal reversible of ideal gas

Delta U will equal 0, because q = -w. This simply means that any energy transferred from system to surroundings as work will immediately be replaced by a flow of heat from surroundings to system (or vice versa, depending on if it's an expansion or compression). Because there is no net change in ener...
by Helen Struble 3B
Sun Feb 16, 2020 5:51 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Different Types of Entropies
Replies: 4
Views: 23

Re: Different Types of Entropies

Delta S and its variants (system, surroundings, total) represent a state function (change in entropy). We can find the value of this change through the equations given to us. However, because a delta valley represents a final value minus and initial value, we know that any system must have a set val...
by Helen Struble 3B
Sun Feb 16, 2020 5:47 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal irreversible reactions
Replies: 3
Views: 19

Re: Isothermal irreversible reactions

Is the delta U of an isothermal irreversible reaction also equal to 0, like it is for an isothermal reversible reaction? If it's not equal to 0, why is that? I'm having trouble wrapping my head around an isothermal irreversible expansion. In isothermal reversible expansions, all the energy transfer...
by Helen Struble 3B
Sun Feb 16, 2020 5:43 pm
Forum: Calculating Work of Expansion
Topic: work = 0
Replies: 14
Views: 47

Re: work = 0

In order for work to be done, it has to be done on something—work measures the transfer of energy. In a vacuum, there is no gas to transfer energy to, so no work is done.
by Helen Struble 3B
Sun Feb 16, 2020 5:42 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Volume of the Universe
Replies: 4
Views: 18

Volume of the Universe

So, for calculating entropy of a system vs. the surroundings vs. the total entropy, should we just assume that the entropy of the surroundings is only affected by heat? Is this based on the assumption that any volume change due to piston expanding or contracting is negligible compared to the volume ...
by Helen Struble 3B
Sun Feb 09, 2020 9:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs LS7A
Replies: 2
Views: 13

Gibbs LS7A

In LS7A, two equations are given for Gibbs free energy:

1) deltaG = deltaH - TdeltaS
2) deltaG = G(standard) + RTlnQ

Can someone relate these two equations? If deltaG is a state function (does not change with path), why would the concentrations of products and reactants affect deltaG?
by Helen Struble 3B
Sun Feb 09, 2020 9:08 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: First Law of Thermodynamics Definition
Replies: 4
Views: 21

Re: First Law of Thermodynamics Definition

The first law of thermodynamics is represented as an equation is delta U = q - w. Often simplified to "the energy of the universe is constant." Since U is equal to internal energy, there also must be an energy of the surroundings. Any change in internal energy has the opposite change on th...
by Helen Struble 3B
Sun Feb 09, 2020 9:01 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: State Functions
Replies: 5
Views: 22

Re: State Functions

Enthalpy and entropy are state functions, but work is not. For me, I recognize a state function because in equations they usually have a delta symbol...delta H (enthalpy), delta S (entropy), delta U (internal energy), delta G (Gibbs free energy) are all state functions. They are not state functions ...
by Helen Struble 3B
Sun Feb 09, 2020 8:55 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Enthalpy and Temperature
Replies: 1
Views: 23

Re: Enthalpy and Temperature

The T refers to the temperature of the surroundings, which remains constant. This is because this equation calculates for entropy of surroundings, and entropy increases more at lower temperatures.
by Helen Struble 3B
Sun Feb 09, 2020 8:51 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U
Replies: 7
Views: 26

Re: Delta U

Isothermal systems have delta U = O because the transfer of heat and pressure are both at equilibrium, so all the energy lost by the work of expansion transfers into the system as heat in order to keep the temperature constant. Since work is being done (system losing energy), -w is negative, and sin...
by Helen Struble 3B
Sun Feb 02, 2020 8:46 pm
Forum: Calculating Work of Expansion
Topic: Work vs. Enthalpy
Replies: 1
Views: 19

Work vs. Enthalpy

Is there any scenario in which a closed reaction would do work on the system but still have a positive enthalpy? So, if delta U = q + w, is it possible for a system to lose heat but still expand, doing work on the system? Or is every reaction that causes work of expansion also exothermic?
by Helen Struble 3B
Sun Feb 02, 2020 8:44 pm
Forum: Calculating Work of Expansion
Topic: Expansion
Replies: 4
Views: 17

Re: Expansion

Work of expansion indicates work being done by the reaction onto the system. Since the flow of energy is from the reaction to the system, we know the reaction is doing work.
by Helen Struble 3B
Sun Feb 02, 2020 8:42 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Identifying
Replies: 4
Views: 20

Re: Identifying

The system gives you insight into where the energy of the reaction is going. In a closed system, since no heat or energy is lost to the environment, delta H is equal to delta U, the internal energy of the system. For closed or open systems it is much more difficult to quantify how much heat is lost ...
by Helen Struble 3B
Sun Feb 02, 2020 8:34 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: delta U = delta H - P delta V
Replies: 3
Views: 17

Re: delta U = delta H - P delta V

dtolentino1E wrote:yes!

the change in internal energy (delta U) is usually calculated as heat (q) + work (w), but at constant pressure, q = delta H and w = -P(deltaV)


How would this change for a constant volume set up? Is delta U no longer equal to qp in that scenario?
by Helen Struble 3B
Sun Feb 02, 2020 8:32 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Purpose
Replies: 2
Views: 15

Re: Purpose

Calorimeters are used to measure temperature changes in constant volume or constant pressure environments. If we can measure the temperature change of a constant pressure or constant volume reaction, we can deduce q p and deltaH. The accuracy depends on the type of calorimeter, more sophisticated, w...
by Helen Struble 3B
Sun Jan 26, 2020 4:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard enthalpy of element in most stable form
Replies: 5
Views: 17

Re: Standard enthalpy of element in most stable form

Elements in their standard state have a standard enthalpy of formation of 0 because they are are not formed, they just exist. They don't require any energy to get to their most stable form if they're already in that form. This is still a little confusing to me because elements in their standard for...
by Helen Struble 3B
Sun Jan 26, 2020 4:14 pm
Forum: Phase Changes & Related Calculations
Topic: Combustion vs. Cellular Respiration
Replies: 5
Views: 28

Combustion vs. Cellular Respiration

Theoretically, is the enthalpy of the reaction for the break down of glucose the same whether it is combusted or broken down in a more controlled manner like in cellular respiration?
by Helen Struble 3B
Sun Jan 26, 2020 4:06 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy vs. Energy
Replies: 2
Views: 12

Enthalpy vs. Energy

What exactly is the difference between enthalpy of a reaction and the energy of the reaction, or is enthalpy just a more specific term for the energy of a reaction?
by Helen Struble 3B
Sun Jan 26, 2020 4:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Lewis Structures Method 2
Replies: 6
Views: 25

Re: Lewis Structures Method 2

It never hurts to draw a Lewis structure to make sure you know exactly which bonds are being broken and which are being formed. For simple molecules, however, you can usually visualize the structure without having to draw the structure on paper.
by Helen Struble 3B
Sun Jan 26, 2020 4:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Preferences between Methods
Replies: 3
Views: 10

Re: Preferences between Methods

The method you have to use will usually be obvious based on the information given to you. For example, if bond energies are given to you, you'll have to compute enthalpy using that method.
by Helen Struble 3B
Sun Jan 19, 2020 7:49 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Acidity and Basicity
Replies: 4
Views: 24

Re: Acidity and Basicity

pH and pOH are important to consider when solving acid base equilibria. Because pH=-log[H3O+], if you are given the pH either initially or at equilibrium, you can use than to find the concentration of H3O at that instant. Using this, you can create an ICE table and solve for whatever the question as...
by Helen Struble 3B
Sun Jan 19, 2020 7:47 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Shift Of Reaction
Replies: 4
Views: 16

Re: Shift Of Reaction

K stays constant, so its talking about which side needs to be produced (either reactants or products) in order to reestablish that constant ratio. The only situation where this isn't the case is when K changes entirely, which is only ever due to a change in temperature.
by Helen Struble 3B
Sun Jan 19, 2020 7:46 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: reactants and products in dynamic equilibria
Replies: 3
Views: 11

Re: reactants and products in dynamic equilibria

The equilibrium either lies towards the reactants or towards the products, depending on how stable the chemical species on either side of the reaction are. More stable chemical species are less likely to participate in the reaction, so equilibrium tends to lie towards whichever side has more stable ...
by Helen Struble 3B
Sun Jan 19, 2020 7:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Buffers
Replies: 2
Views: 17

Buffers

What do we need to know about buffer reactions? If given a buffer system, what are potential questions we will be asked?
by Helen Struble 3B
Sun Jan 19, 2020 7:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acid Base Equilibria
Replies: 5
Views: 25

Acid Base Equilibria

How are acid base calculations different than regular equilibria calculations? Or is it all the same concepts just applied in one specific scenario?
by Helen Struble 3B
Sun Jan 12, 2020 3:27 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and speed of reaction
Replies: 5
Views: 30

Re: Q and speed of reaction

In the same way that K does not tell us about how quickly a reaction reached equilibrium, Q only tells us which direction a reaction will proceed, not how quickly. This is because Q is calculated from the instantaneous pressures or concentrations. Since it's from one instant, we cannot infer any inf...
by Helen Struble 3B
Sun Jan 12, 2020 3:24 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q
Replies: 6
Views: 25

Re: Q

The reaction quotient tells us which direction the reaction will proceed to reach equilibrium. If Q<K, then there are less products than would be found in the equilibrium reaction so the reaction proceeds in the forward direction. By the same logic, if Q>K, then there are more products than would be...
by Helen Struble 3B
Sun Jan 12, 2020 3:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Factors Affecting K
Replies: 5
Views: 30

Re: Factors Affecting K

For a reaction in solution, both temperature and system pressure would affect the equilibrium constant. This is because both of these affect the chemical activity of a species. Since concentration is just an approximation of chemical activity, anything that changes chemical activity will change the ...
by Helen Struble 3B
Sun Jan 12, 2020 3:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: when to use Kc vs Kp
Replies: 11
Views: 35

Re: when to use Kc vs Kp

As others mentioned, brackets denote concentration (in mol.L -1 ), so you wouldn't use them when calculating partial pressure for Kp. However, just because you are given all gases does not necessarily mean you will be calculating Kp, so pay attention to what the question asks and what values are gi...
by Helen Struble 3B
Sun Jan 12, 2020 3:07 pm
Forum: Ideal Gases
Topic: Partial Pressure
Replies: 4
Views: 16

Re: Partial Pressure

To calculate partial pressure, find the molar fraction of each gas. Then, multiply the molar fraction by the total pressure in the container.
by Helen Struble 3B
Wed Dec 04, 2019 1:47 pm
Forum: Lewis Acids & Bases
Topic: Characteristics of Lewis acids
Replies: 2
Views: 27

Characteristics of Lewis acids

Do Lewis acids have the same qualities as Bronsted acids, even if there is no transfer of H+ ion? Would they still taste sour or can we only make this assumption for traditional Bronsted acids?
by Helen Struble 3B
Sun Dec 01, 2019 6:06 pm
Forum: Bronsted Acids & Bases
Topic: How to tell
Replies: 4
Views: 32

Re: How to tell

Bronsted acids and bases are determined by whether they donate or accept protons. Remember, protons are just H + ions. Since this is just a hydrogen atom with no electrons, it is attracted to lone pairs, almost like a ligand. Since NH 3 has a lone pair, it readily accepts hydrogen atoms, therefore i...
by Helen Struble 3B
Sun Dec 01, 2019 6:00 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: H2SO4
Replies: 2
Views: 20

H2SO4

Since H2SO4 is a strong acid with two hydrogens, do both hydrogens ionize in water? If so, does this mean the concentration of H+ ions would be double the concentration of H2SO4? If only one hydrogen ionizes, why?
by Helen Struble 3B
Sun Dec 01, 2019 5:56 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Neutralization
Replies: 7
Views: 49

Re: Neutralization

Neutralization brings the pH back to a neutral 7. If the solution is basic (pH greater than 7) then you will have to add an acid to neutralize it. If the solution is acidic (pH less than 7) then you will have to add a base to neutralize it.
by Helen Struble 3B
Sun Dec 01, 2019 5:54 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong vs Weak Acids and Bases
Replies: 5
Views: 46

Re: Strong vs Weak Acids and Bases

There are only six strong acids, so I've always found it easiest to memorize them. They are: HCl, HNO3, H2SO4, HBr, HI, HClO3, and HClO3. Since they're strong acids, these six will completely ionize in water. Be sure to know all the other properties of these strong acids, too.
by Helen Struble 3B
Sun Dec 01, 2019 5:49 pm
Forum: Lewis Acids & Bases
Topic: acid v. base?
Replies: 16
Views: 73

Re: acid v. base?

Lewis acids can accept electrons because they have an empty orbital. So, to identify a Lewis acid, just look for an incomplete octet. Lewis bases have to have a lone pair (though not every structure with a lone pair is a Lewis base, obviously).
by Helen Struble 3B
Sun Nov 24, 2019 9:13 pm
Forum: Naming
Topic: Cobalt vs. Cobaltate
Replies: 4
Views: 24

Re: Cobalt vs. Cobaltate

Colbatate indicates that the entire compound has a negative charge. This means the coordination compound is an anion and can form an ionic bond with a cation to form another compound.
by Helen Struble 3B
Sun Nov 24, 2019 9:12 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Sphere
Replies: 5
Views: 35

Coordination Sphere

What is the significance of the coordination sphere? Do all the atoms in a ligand have to be inside the sphere?
by Helen Struble 3B
Sun Nov 24, 2019 9:10 pm
Forum: Biological Examples
Topic: Cisplatin
Replies: 12
Views: 91

Re: Cisplatin

I think the important thing about cisplatin is the way its structure affects its biological function. Because the two chlorine atoms are next to each other instead of across, they can bond to both sides of DNA's double helix, preventing it from "unzipping" and therefore stopping replicatio...
by Helen Struble 3B
Sun Nov 24, 2019 9:08 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Transition Metals
Replies: 2
Views: 18

Transition Metals

Why is it that only transition metals form coordination compounds, and not s-block metals?
by Helen Struble 3B
Sun Nov 24, 2019 9:07 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordinate covalent bonds
Replies: 5
Views: 30

Re: Coordinate covalent bonds

A coordinate bond is one in which both shared electrons are provided by a single compound, as opposed to each atom/compound providing one electron to form a bond. The compound which binds to the transition metal by donating two electrons is known as the ligand.
by Helen Struble 3B
Sun Nov 17, 2019 10:24 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Stronger molecular force?
Replies: 2
Views: 16

Re: Stronger molecular force?

Ion-ion is the stronger force. We can infer this from the dramatic difference in boiling point between ionic compounds and compounds with hydrogen bonding. The melting point of water is 0 degrees celsius. The melting point of NaCl, which has ion-ion interactions, is 801 degrees celsius. This shows t...
by Helen Struble 3B
Sun Nov 17, 2019 10:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs
Replies: 2
Views: 23

Re: Lone Pairs

^^Lone pairs definitely influence molecular shape. Compared to shapes which do not have lone pairs, shapes with lone pairs usually have smaller bond angles because of the stronger repulsion. However, the actual name ("see-saw" or "trigonal pyramidal") comes from the geometric arr...
by Helen Struble 3B
Sun Nov 17, 2019 10:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AXE Formula
Replies: 4
Views: 29

AXE Formula

Is the only way to determine a molecule's AXE formula to draw the Lewis structure? Is there any way to determine if there are lone pairs without drawing a Lewis structure?
by Helen Struble 3B
Sun Nov 17, 2019 10:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angles
Replies: 8
Views: 35

Re: bond angles

Lone pairs have stronger electron repulsion than a bonding atom's electron cloud, so they typically distort bond angles. The bonding atoms are pushed further away from the lone pair. This results in smaller bond angles than if there were only atoms and no lone pairs.
by Helen Struble 3B
Sun Nov 17, 2019 10:06 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs on VSEPR Model
Replies: 2
Views: 17

Re: Lone Pairs on VSEPR Model

The example we talked about in class was for the "see-saw," or AX 4 E. This geometry is the same as trigonal bipyramidal except one of the axial atoms is instead a lone pair. Lone pairs have higher repulsion, so the lowest energy structure is one in which the lone pair is in the place of a...
by Helen Struble 3B
Sun Nov 10, 2019 10:09 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Relationship between size of atom and bond strength
Replies: 2
Views: 11

Re: Relationship between size of atom and bond strength

I think you are confusing the strength of bonds with the strength of the intermolecular forces. The bond is what holds the two atoms together, for F 2 and I 2 , this is a non polar covalent bond. The intermolecular forces are what keep the molecules together as a solid, liquid, or gas. In your quest...
by Helen Struble 3B
Sun Nov 10, 2019 10:02 pm
Forum: Dipole Moments
Topic: dipole
Replies: 4
Views: 34

Re: dipole

Dipoles are the partial negative and partial positive charges on molecules which have atoms with a notable difference in electronegativity. We can figure out if a molecule will have a dipole by calculating the difference in electronegativity between atoms.
by Helen Struble 3B
Sun Nov 10, 2019 8:36 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Boiling point
Replies: 5
Views: 26

Re: Boiling point

The bond type doesn't necessarily contribute to boiling point, but the IMFs associated with certain bonds do. For instance, ionic salts like NaCl have strong ion-ion forces which give it its high boiling point because it requires a lot of energy in the form of heat to overcome these forces. F 2 is a...
by Helen Struble 3B
Sun Nov 10, 2019 8:31 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Lattice Energy
Replies: 2
Views: 12

Lattice Energy

How can we predict the lattice energy of a compound. What forces are responsible for the lattice energy?
by Helen Struble 3B
Sun Nov 10, 2019 8:30 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Fluctuating Dipoles
Replies: 5
Views: 24

Re: Fluctuating Dipoles

Remember that electrons exist in a cloud around an atom. Though we can use probability and wave functions to get an idea of where they are likely to be, we can never know for sure where electrons are around the atom/molecule at any given moment. Occasionally, the electrons random motion around the a...
by Helen Struble 3B
Sun Nov 03, 2019 6:33 pm
Forum: Bond Lengths & Energies
Topic: Bond Strength
Replies: 6
Views: 26

Re: Bond Strength

The strength of any bond comes from the bonding electrons attraction to the nucleus. It follows that the more attracted the bonding electrons are to the nucleus of the two atoms involved in a bond, then the stronger the bond. Because the bonding electrons of smaller atoms are closer to the nucleus, ...
by Helen Struble 3B
Sun Nov 03, 2019 6:29 pm
Forum: Dipole Moments
Topic: Induced Dipole
Replies: 5
Views: 49

Re: Induced Dipole

Induced dipoles are caused when a non-polar compound (no dipoles) comes close to a polar compound (with dipoles). Because the polar compound has partial charges, when the electron cloud of the non-polar compound is close, the negatively charged electrons are repelled from the negative pole and attra...
by Helen Struble 3B
Sun Nov 03, 2019 6:21 pm
Forum: Octet Exceptions
Topic: Identifying Radicals
Replies: 6
Views: 49

Re: Identifying Radicals

Given that this is chemistry for life science majors, radicals are particularly important because they can wreak havoc on biological systems. Since they are so reactive, they can react with important biological molecules, even DNA, causing mutations. I'm pretty sure radicals come into play when any ...
by Helen Struble 3B
Sun Nov 03, 2019 6:09 pm
Forum: Ionic & Covalent Bonds
Topic: Homework 2D #15
Replies: 5
Views: 48

Re: Homework 2D #15

In order to answer this question, we need to look at atomic trends. F, Cl, and Br are all in the same group, but different periods. As you move down a group, atomic radius increases. Why is this important? Increasing atomic radius means increasing bond length. Longer bonds typically require less ene...
by Helen Struble 3B
Sun Nov 03, 2019 6:01 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Purpose of Formal Charge
Replies: 6
Views: 24

Re: Purpose of Formal Charge

Formal charge allows us to find the most likely molecular structure when there are multiple valid Lewis structures. Among the valid Lewis structure, the structure with FC closest to 0 is the most likely arrangement of atoms. It is super important to note that this is not the same as resonance or ele...
by Helen Struble 3B
Sun Oct 27, 2019 3:50 pm
Forum: Resonance Structures
Topic: Resonance hybrids
Replies: 3
Views: 32

Re: Resonance hybrids

A resonance hybrid represents electron delocalization. Though the Lewis structures may indicate a different between the single and double bonds, suggesting a difference in bond length, if a molecule or compound is a resonance hybrid then the electrons delocalize and there is no difference in bond le...
by Helen Struble 3B
Sun Oct 27, 2019 3:46 pm
Forum: Ionic & Covalent Bonds
Topic: Valence Electrons
Replies: 16
Views: 110

Re: Valence Electrons

^^It's important to note that this is a shortcut that really only works for the s-block and p-block, when we can assume that most bonding will follow the octet rule. However, there are even exceptions to the octet rule in the p-block—take PCl 5 . So don't always assume a full octet is a full valence...
by Helen Struble 3B
Sun Oct 27, 2019 3:13 pm
Forum: Trends in The Periodic Table
Topic: Question on 2A.23 part a
Replies: 2
Views: 12

Re: Question on 2A.23 part a

Because magnesium is a group 2 element, we can expect it to take on a 2+ charge, making it isoelectronic to neon and thus more stable. Though the p block is a little harder to predict, in an ionic compound, we can make an educated guess that arsenic will take on a 3- electronic charge, making it iso...
by Helen Struble 3B
Sun Oct 27, 2019 2:56 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration Special Cases
Replies: 6
Views: 44

Re: Electron Configuration Special Cases

I think that Lavelle really only expects us to know the chromium and copper exceptions, but from the little bit of research I've done, it seems that rubidium and silver also have abnormal electron configurations because it is more stable to have a half-filled or filled d orbital. I'm not sure if thi...
by Helen Struble 3B
Sat Oct 26, 2019 11:22 pm
Forum: Trends in The Periodic Table
Topic: Period 3 Elements
Replies: 2
Views: 17

Re: Period 3 Elements

Period 3 elements have access to the 3d orbital even though they fill the 3p orbital first. Electrons in the d orbital still can function as valence electrons. This allows them to form more bonds/have more lone pairs than the octet rule would typically allow.
by Helen Struble 3B
Sat Oct 19, 2019 3:26 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Spin Magnetic Quantum Number
Replies: 1
Views: 24

Re: Spin Magnetic Quantum Number

The spin of an electron is only relevant when filling out electronic configurations. The quantum number ms in no way determines how many orbitals exist—that is all based on the principle quantum number (n), angular momentum quantum number (l), and magnetic quantum number (ml). ms comes into play whe...
by Helen Struble 3B
Sat Oct 19, 2019 3:10 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: HW 1D.23
Replies: 2
Views: 27

Re: HW 1D.23

Let's walk through the possible quantum values, knowing that if n is given, l can be = 0, 1, 2...n-1 and m can be = l, l-1, l-2....-l. An orbital is any valid set of unique quantum numbers. A) n=2, l=1. ml is not given, and can have the possible values of -1, 0, and 1. Therefore, since we can make t...
by Helen Struble 3B
Sat Oct 19, 2019 2:58 pm
Forum: Quantum Numbers and The H-Atom
Topic: Angular Momentum Quantum Number
Replies: 3
Views: 50

Re: Angular Momentum Quantum Number

The second quantum number, l, describes shape because it clues us into how many radial and angular nodes are in the subshell. With the principle quantum number, n, we can figure out how many radial and angular nodes are in a subshell. N=sum of radial and angular nodes. N = n - l - 1. So, for the 3p ...
by Helen Struble 3B
Sat Oct 19, 2019 2:51 pm
Forum: *Shrodinger Equation
Topic: Wave Function
Replies: 2
Views: 26

Re: Wave Function

The use of the variable psi denotes a wave function in the same way that the use of the variable x and y denotes a cartesian function or r and theta denotes a polar function. Psi itself does not really have an equivalent in the physical system, however, as it only represents the amplitude of the wav...
by Helen Struble 3B
Sat Oct 19, 2019 2:30 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Numbers
Replies: 3
Views: 31

Re: Quantum Numbers

Remember, the angular momentum quantum number, l, determines the subshell. n can have integer values greater than 0, in this case n=4 is given. l can have integer values from 0 to n-1, so if n=4, l can = 0,1,2,3. So, in a ground state there are a possible of four subshells: l=0 would be the s subshe...
by Helen Struble 3B
Sun Oct 13, 2019 6:15 pm
Forum: Properties of Light
Topic: Visualizing wave-particle duality
Replies: 3
Views: 43

Visualizing wave-particle duality

I find that I keep visualizing light as a wave of photons now. Does the wave-particle duality mean that light is like a stream of photons in a wave? Or does it mean that every individual photon also individually behaves as a wave? If the latter, is the wavelength of light the same as the wavelength ...
by Helen Struble 3B
Sun Oct 13, 2019 6:07 pm
Forum: Photoelectric Effect
Topic: Why do electrons behave like a particle in the photoelectric effect?
Replies: 2
Views: 40

Re: Why do electrons behave like a particle in the photoelectric effect?

The photoelectric effect actually studies the particle-like qualities of light, more so than electrons. If light were truly a wave, then by the standard wave model increasing the intensity of the light should eject electrons from the surface of a metal. It was assumed that more intensity = more ener...
by Helen Struble 3B
Sun Oct 13, 2019 5:44 pm
Forum: Einstein Equation
Topic: Diffraction patterns
Replies: 2
Views: 39

Re: Diffraction patterns

The diffraction patterns exhibited by electrons prove that electrons exhibit wave-like properties as well as typical particle-like properties. Diffraction is a phenomenon which occurs in waves which are directed at an obstacle or slit which is similar in size to the wavelength. Because diffraction i...
by Helen Struble 3B
Thu Oct 10, 2019 7:05 pm
Forum: Properties of Electrons
Topic: Rydberg Formula
Replies: 2
Views: 423

Re: Rydberg Formula

Instead of using the Rydberg formula, I prefer to simply find the change in electron energy between each energy level. We know the E n = -(hR)/n 2 . This gives us the energy of an electron at every energy level in the hydrogen spectra. Knowing this, we can set up an equation for Delta E, knowing tha...
by Helen Struble 3B
Thu Oct 10, 2019 6:51 pm
Forum: Properties of Light
Topic: Classical Mechanics
Replies: 4
Views: 74

Re: Classical Mechanics

We only need to describe light as quantized when we are describing interactions between individual photons and electrons/atoms/m'cules. This is why we need to use the quantized model to explain the photoelectric effect—because it is individual photons exciting individual electrons, it is only the en...
by Helen Struble 3B
Thu Oct 03, 2019 4:07 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Fundamental E
Replies: 2
Views: 70

Re: Fundamental E

Because you know how many moles of H 2 O are in the coffee, you can use molar ratios to find the solution. Because it is H 2 O, we know that there are two hydrogen atoms in each water molecule, therefore for each mole water, there are two moles hydrogen. Then, we can set up a conversion factor: 2 mo...
by Helen Struble 3B
Wed Oct 02, 2019 7:20 pm
Forum: Limiting Reactant Calculations
Topic: Steps to calculate limiting reagant
Replies: 4
Views: 46

Re: Steps to calculate limiting reagant

Once you have the moles available of each reactant, you must compare to the molar ratios given in the chemical equation. Take the balanced equation: N 2 + 3H 2 = 2NH 3 . You have already calculated moles of each reactant as 3.0 moles of N 2 and 8.0 moles of H 2 . I would proceed by picking one of th...
by Helen Struble 3B
Wed Oct 02, 2019 1:52 pm
Forum: Empirical & Molecular Formulas
Topic: Homework problem E1
Replies: 9
Views: 91

Re: Homework problem E1

For me, the easiest way to approach this problem was simply as a dimensional analysis problem. As with any dimensional analysis, I started by establishing conversion factors. It is important to note that the problem gives the radius of an Ag atom, but since we are thinking of a string of atoms lined...
by Helen Struble 3B
Wed Oct 02, 2019 11:44 am
Forum: Significant Figures
Topic: How Many significant figures to use ?
Replies: 9
Views: 111

Re: How Many significant figures to use ?

Keep in mind, significant figures are not only about decimal places. Leading zeros and trailing zeros are still not significant. For example, .0000000078 actually still only has two significant figures. Likewise, 78000000 only has two. Decimal places do denote significant figures when a number is wr...
by Helen Struble 3B
Wed Oct 02, 2019 11:36 am
Forum: SI Units, Unit Conversions
Topic: mol, g.mol and g.mol-1
Replies: 12
Views: 156

Re: mol, g.mol and g.mol-1

Mols are not the same as g*mol or g*mol-1. A mole is a unit of amount—in chemistry, it is usually used to represent how many particles are in a certain mass of compound (this is much easier than doing calculations using the actual number of atoms/particles). If you need to know exactly how many atom...

Go to advanced search