## Search found 100 matches

Sat Mar 14, 2020 9:31 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 4
Views: 79

### Molecularity

Are there any equations associated with molecularity, or is it just something we need to know conceptually?
Sat Mar 14, 2020 9:26 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A- frequency factor
Replies: 3
Views: 59

### Re: A- frequency factor

Since A is a constant, similar to k, it will either be given or potentially solved for, which can be done by rearranging the Arrhenius Equation
Sat Mar 14, 2020 7:51 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: rate determining step
Replies: 4
Views: 77

### Re: rate determining step

The rate determining step will be the slowest occurring step in the mechanism. For instance, if you're building a car and the engine takes the longest to install, it doesn't matter how fast you assemble the rest of the car, the final product won't be produced until the engine is in place.
Sat Mar 14, 2020 6:43 pm
Forum: First Order Reactions
Topic: Half Life
Replies: 1
Views: 60

### Half Life

Conceptually, is there a reason why only first order reactions do not depend on initial concentration for half life, while Zeroth and Second Order do?
Sat Mar 14, 2020 6:41 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: negative sign
Replies: 6
Views: 117

### Re: negative sign

Energy = -work/Charge;
Rearrange this to get work = -E*Charge
From the Farraday's constant, Charge = n*F
Therefore work = -n*F*E
At constant temp and pressure, work max = deltaG
Therefore deltaG = -n*F*E
Sun Mar 08, 2020 8:43 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Microscopic Reversibility
Replies: 1
Views: 17

### Microscopic Reversibility

Does microscopic reversibility just mean that the reverse reaction follows the same mechanism of the forward reaction, but backwards?
Sun Mar 08, 2020 8:29 pm
Forum: General Rate Laws
Topic: Pseudo-Rate Law
Replies: 2
Views: 25

### Pseudo-Rate Law

When calculating the rate of a multi-reactant reaction, why is it necessary to find the pseudo rate and increase the concentrations of all of the reactants but one?
Sun Mar 08, 2020 8:09 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: How to determine the order of a reactant
Replies: 3
Views: 59

### Re: How to determine the order of a reactant

Within the scope of this class at least, you can only calculate the order of a species when it is the only concentration changing.
Sun Mar 08, 2020 7:36 pm
Forum: First Order Reactions
Topic: Graphing 1st order reaction rates
Replies: 6
Views: 45

### Re: Graphing 1st order reaction rates

You graph ln[A] vs time in order to get a linear graph, since it is ln[a] = -kt + c, not [a] = -kt + c. Using this you can find the value of k for the reaction, which would be the slope.
Sun Mar 08, 2020 7:33 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Solids/Liquids
Replies: 3
Views: 46

### Solids/Liquids

For the rate of the reaction, k[a][b], what happens if either a or b is a solid or liquid. Is it like the equilibrium constant where a product/reactant in a solid or gas phase is negligible?
Sun Mar 01, 2020 7:05 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: pH?calculating ph
Replies: 2
Views: 39

### Re: pH?calculating ph

Ahh I see, thanks for the help!
Sun Mar 01, 2020 6:51 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: pH?calculating ph
Replies: 2
Views: 39

### pH?calculating ph

How can you calculate pH using the Nernst equation?
Sun Mar 01, 2020 6:45 pm
Forum: Balancing Redox Reactions
Topic: OH and H
Replies: 8
Views: 86

### OH and H

When balancing reactions in basic and acidic solution, will OH and H, respectively, be a product or reactant, or can it be either? If either, is there a pattern?
Sun Mar 01, 2020 6:17 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Cell Diagram
Replies: 4
Views: 46

### Cell Diagram

Is the method for writing out cell potentials for concentration cells the same as standard galvanic cells?
Sun Mar 01, 2020 6:16 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cells
Replies: 4
Views: 54

### Re: Concentration Cells

I think the primary difference between concentration cells and galvanic cells is that the aqueous solution and the electrodes are the same, just in difference concentrations. In this case, the cell potential isn't coming from the difference in standard potentials for the electrodes, but rather the d...
Sun Feb 23, 2020 6:36 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: F
Replies: 7
Views: 74

### F

Sun Feb 23, 2020 6:03 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Negative E
Replies: 3
Views: 23

### Negative E

If standard potential is a negative number, does this mean the reverse process is spontaneous, where electrons flow from right to left instead of left to right?
Sun Feb 23, 2020 5:52 pm
Forum: Balancing Redox Reactions
Topic: 6K.1
Replies: 6
Views: 73

### Re: 6K.1

To find the half reaction, identify the change occurring in the oxidation numbers of the same elements. In Cr2O7 2-, Cr has an oxidation state of 6+, but on the right side Cr has a 3+ charge; Cr has gained electrons and been oxidized. For C2H5OH, C has a -2 oxidation state, while in C2H4O, C has a -...
Sun Feb 23, 2020 5:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating Cell Potentials
Replies: 2
Views: 42

### Re: Calculating Cell Potentials

Yes, since the cathode is on the right and anode on the left, subtracting the right value from the left value will result in the value of a positive cell potential.
Sun Feb 23, 2020 5:33 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum
Replies: 4
Views: 39

### Platinum

In the example from Friday lecture where the solutions have aqueous and not solid conductors, Cu(s) | Cu2+(aq) || Fe3+(aq), Fe2+(aq) | Pt (s), why is platinum not included on the left side of the cell diagram as well?
Sun Feb 16, 2020 6:22 pm
Forum: Balancing Redox Reactions
Topic: Oxygen
Replies: 9
Views: 74

### Re: Oxygen

Then aside from the element in its pure form, like in a compound NH3, FeO, etc. will the oxidation numbers for H and O consistently be +1 and -2
Sun Feb 16, 2020 5:06 pm
Forum: Balancing Redox Reactions
Topic: Oxygen
Replies: 9
Views: 74

### Oxygen

Will elements such as oxygen and hydrogen always have the same oxidation numbers (i.e. -2, +1)? Do only transition metals have varying oxidation state?
Sun Feb 16, 2020 4:24 pm
Forum: Calculating Work of Expansion
Topic: work = 0
Replies: 14
Views: 240

### Re: work = 0

If a system is isochoric (constant volume), no work will be done since w = p*deltaV, and since there is no change in volume the w = 0.
Sun Feb 16, 2020 4:09 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Delta s = 0
Replies: 8
Views: 164

### Re: Delta s = 0

In a reversible isothermal reaction, the total entropy of the system will equal 0, as the change in entropy inside the system will be counterbalanced by a change in entropy of the opposite sign by the entropy of the surroundings.
Sun Feb 16, 2020 3:16 pm
Forum: Van't Hoff Equation
Topic: given values
Replies: 3
Views: 45

### Re: given values

If we did have to solve for delta H naught, I assume you could do so either through the standard enthalpies of formation or even the deltaU = q + w formula.
Sun Feb 09, 2020 10:19 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: The sign of entropy
Replies: 2
Views: 35

### Re: The sign of entropy

Based on the equations nRln(V2/V1) and nCln(T2/T1), the only way to get a negative delta entropy would be to have the ln term be negative. This would occur by having a decrease in volume or temperature, which produces a value less that 1 for V2/V1 and T2/T1, giving a negative number when using ln.
Sun Feb 09, 2020 8:57 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Pressure
Replies: 2
Views: 43

### Pressure

As per the category name, there are obviously formulas for delta S due to volume and temperature changes. But is there any change in delta S if there is a change in pressure? Please explain why or why not
Sun Feb 09, 2020 8:47 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: including phase changes
Replies: 2
Views: 41

### Re: including phase changes

If a phase change does occur in the problem, the enthalpy of fusion/vaporization should be given (so long as it's not water, the values of which are on the formula sheet), which should indicate that you would need to include phase change calculations.
Sun Feb 09, 2020 8:34 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: Degrees of Change in Entropy
Replies: 5
Views: 53

### Re: Degrees of Change in Entropy

delta S with the degree symbol refers to the standard entropy value, the amount of entropy of one mole of a molecule. It is in units of J/(K*mol).
Sun Feb 09, 2020 6:47 pm
Forum: Phase Changes & Related Calculations
Topic: Heat & Temperature of Phase Changes
Replies: 5
Views: 34

### Re: Heat & Temperature of Phase Changes

At a temperature where phase change occurs, heat energy is being used to separate molecules rather than change the temperature of the substance, resulting in a constant temperature.
Sat Feb 01, 2020 4:53 pm
Forum: Calculating Work of Expansion
Topic: When to Use the Integral
Replies: 2
Views: 16

### Re: When to Use the Integral

The integral is necessary when P is not a constant. In the derivation of the integral, when P is constant it can be removed from the integral as a coefficient, becoming P * the integral of dv. The integral of dv is equivalent to v2 - v1 (delta V) which produces P*delta V.
Sat Feb 01, 2020 4:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Elements
Replies: 8
Views: 41

### Elements

Why do substances like O2 have a 0 standard enthalpy of formation?
Sat Feb 01, 2020 4:31 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Energy of Systems
Replies: 4
Views: 38

### Re: Energy of Systems

Why does changing the amount of substance effect internal energy? Is it due to a change in enthalpy?
Sat Feb 01, 2020 4:22 pm
Forum: Calculating Work of Expansion
Topic: Reversible Process
Replies: 2
Views: 40

### Reversible Process

Does a reaction with a constant pressure count as an irreversible process?
Sat Feb 01, 2020 3:19 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Two-State System
Replies: 1
Views: 29

### Two-State System

What are the two degenerate states in the "dog-bone" example that Dr. Lavelle gave in lecture? What makes them different from each other?
Sat Jan 25, 2020 2:05 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard state
Replies: 3
Views: 21

### Re: Standard state

The standard state is the phase a compound is in at standard conditions (25 C, 1 atm), and is typically indicated for an element on the periodic table.
Sat Jan 25, 2020 1:56 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 3
Views: 44

### Re: Phase Changes

Yes, it's just the change in heat between the final and initial states. The deltaH between states will be the same, only the sign will be different (e.g. solid -> liquid deltaH = 50, liquid -> solid deltaH = -50)
Sat Jan 25, 2020 1:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat
Replies: 1
Views: 22

### Heat

In lecture, Dr. Lavelle mentioned that enthalpy is a state function but that heat was not. What's the difference between the two?
Sat Jan 25, 2020 1:35 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Change
Replies: 4
Views: 42

### Phase Change

How do you determine the value of the change in enthalpy between phase states?
Sat Jan 25, 2020 1:29 pm
Forum: Phase Changes & Related Calculations
Topic: Bond Enthalpies
Replies: 5
Views: 47

### Re: Bond Enthalpies

However, using bond enthalpy to calculate the change in enthalpy is the most inaccurate of the three methods, as a lot of the calculations for bond enthalpies rely on averages rather than exact figures.
Sat Jan 18, 2020 6:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant Units
Replies: 4
Views: 43

### Equilibrium Constant Units

I know that Kc is a value without units, but can someone explain why that is? The units don't strictly cancel out all of the time.
Sat Jan 18, 2020 6:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Questions and Sig Figs
Replies: 6
Views: 67

### Re: Equilibrium Questions and Sig Figs

Calculating for sig figs should only be done at the end of the problem to ensure the accuracy of your answer. While realistically rounding early might only throw the answer off by a couple hundredths, I'd say its better safe than sorry.
Sat Jan 18, 2020 5:50 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Kb vs Ka
Replies: 5
Views: 29

### Re: Kb vs Ka

If I understood correctly, I believe that it is the Kb/Ka for the conjugate reaction, whichever produces either OH or H3O, respectively
Sat Jan 18, 2020 5:17 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Identifying Acids, Bases, and Salts in a Rxn
Replies: 4
Views: 48

### Re: Identifying Acids, Bases, and Salts in a Rxn

Salts typically consist of an cation bonded to anion (e.g. NaCl, CaI)
Sat Jan 18, 2020 5:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc sig figs
Replies: 4
Views: 39

### Re: Kc sig figs

For log sig figs, you take the number of sig figs from the number you log and have that many sig figs after the decimal point of your answer (e.g. log(3.800) = 0.5798).
Sun Jan 12, 2020 1:46 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Quick way
Replies: 7
Views: 90

### Re: Quick way

The example Dr. Lavelle gave in class was if you added Helium to a reaction occurring within a sealed container. While the pressure of the reaction is increasing, it has no effect on the equilibrium because adding gas doesn't have any effect on the actual concentration of either the products or reac...
Sun Jan 12, 2020 1:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K = 1
Replies: 2
Views: 16

### Re: K = 1

For a reaction to have K = 1, there must be equal concentration of reactant and product at equilibrium. This entails that neither side must be favored, something that rarely occurs as the purpose of a reaction is to achieve a more preferred, stable form.
Sun Jan 12, 2020 11:43 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q
Replies: 6
Views: 81

### Re: Q

Q taken at any point when the reaction is not at equilibrium indicates the direction that will be favored by the reaction. If Q is less than Kc, then there is an excess of reactants, and product will be created to balance that amount out. The same goes vice versa if Q is greater than Kc leading to m...
Sun Jan 12, 2020 11:40 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q<K
Replies: 4
Views: 25

### Re: Q<K

If Q is less than K, that means the Q ratio has a higher concentration of reactants due to the form [P]/[R], as a higher denominator produces a smaller number. To raise Q to the value of Kc, the amount of R must be reduced, which is done by creating more product, or favoring the right
Sun Jan 12, 2020 11:36 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pressure
Replies: 1
Views: 24

### Re: pressure

Manipulating the ideal gas law (PV = nRT) into the form P = nRT/V, n/V is equal to concentration creating the formula P = concRT. Concentration is therefore equal to Pressure divided by R and T (Kelvin).
Sat Dec 07, 2019 12:51 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligand Charges
Replies: 3
Views: 64

### Ligand Charges

Is there a way to calculate the charge of a ligand, or is it something that just has to be memorized?
Sat Dec 07, 2019 12:48 pm
Forum: Sigma & Pi Bonds
Topic: pi bonds
Replies: 5
Views: 179

### Re: pi bonds

Yup, a bonding region can only have one sigma bond but multiple pi bonds.
Sat Dec 07, 2019 12:41 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: HClO3
Replies: 2
Views: 123

### Re: HClO3

Since oxygen is the most electronegative atom and has a negative charge, hydrogen attaches to oxygen in order to neutralize the charge and make the molecule more stable.
Fri Dec 06, 2019 2:18 pm
Forum: Lewis Acids & Bases
Topic: electron withdrawing
Replies: 2
Views: 53

### Re: electron withdrawing

When an acid donates a hydrogen, it gains a negative charge from accepting an electron lone pair. The stability of the resulting anion determines if the acid is strong or weak. In electron withdrawing, electronegative atoms in the anion work to delocalize the negative charge and in doing so makes th...
Fri Dec 06, 2019 2:12 pm
Forum: Bronsted Acids & Bases
Topic: Hydrogen Bonding
Replies: 10
Views: 219

### Hydrogen Bonding

Is the formation of hydrogen bonds considered an interaction between an acid and base?
Sun Dec 01, 2019 1:17 pm
Forum: Bronsted Acids & Bases
Topic: Ammonia NH3
Replies: 1
Views: 33

### Ammonia NH3

Is it possible for ammonia to act as an acid by donating one of its hydrogen atoms, rather than acting as a base as is normally seen?
Sun Dec 01, 2019 1:11 pm
Forum: Lewis Acids & Bases
Topic: Donating Proton vs Accepting Electron
Replies: 4
Views: 73

### Re: Donating Proton vs Accepting Electron

They are essentially just different ways of saying the same thing. An acid loses it's hydrogen (proton) in water to form hydronium (H3O), and in exchange gains the electron lone pair from the water molecule it interacts with.
Sun Dec 01, 2019 1:06 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Organic vs. Inorganic Acids
Replies: 2
Views: 50

### Re: Organic vs. Inorganic Acids

Because organic acids typically don't have atoms with high electronegativity, the presence of which gives the attached hydrogen a greater partial positive charge and incentive for proton transfer, the hydrogen atom is less likely to form hydronium with water
Sun Dec 01, 2019 12:44 pm
Forum: Naming
Topic: Coordination compounds vs complexes
Replies: 2
Views: 38

### Re: Coordination compounds vs complexes

Just going off of the language in the textbook, it seems that the two terms are interchangeable.
Sun Dec 01, 2019 12:38 pm
Forum: Lewis Acids & Bases
Topic: Strong Acids/Bases
Replies: 2
Views: 31

### Strong Acids/Bases

What gives strong acids/bases harmful qualities, ie. strong corrosive property?
Sat Nov 23, 2019 11:40 pm
Forum: Biological Examples
Topic: Heme Complex
Replies: 5
Views: 94

### Re: Heme Complex

A heme complex is the specific arrangement of a central Fe atom surrounded by 4 N atoms. If the central atom isn't Fe but is a different type of transition metal, then it isn't a heme complex but rather a different complex.
Sat Nov 23, 2019 11:33 pm
Forum: Naming
Topic: Greek Prefixes
Replies: 2
Views: 43

### Greek Prefixes

I think I understand how to use the bis-, tris-, tetrakis-, etc. prefixes but can someone provide an example where this is used?
Sat Nov 23, 2019 11:19 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation Number
Replies: 3
Views: 40

### Re: Oxidation Number

Oxidation number for the transition metal is calculated by adding up the negative charges of the ligands attached to the central metal then comparing that number to the total charge of the atom. The oxidation number will be the difference between the total charge and the negative charges, as the pos...
Sat Nov 23, 2019 11:15 pm
Forum: Hybridization
Topic: Sigma Bonding
Replies: 2
Views: 51

### Re: Sigma Bonding

When the book talks about the 2pz orbital as being the only one able to form a sigma bond, it only means with respect to the z axis. Since 2pz is the only orbital directly along the z axis, the 2px and 2py orbitals, if they are involved through double or triple bond, form pi bonds. However, the 2px ...
Wed Nov 20, 2019 12:45 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Pentagonal Bipyramidal
Replies: 8
Views: 99

### Re: Pentagonal Bipyramidal

We most likely don't need to know it, but just in case the structure is a pentagonal formation on the equatorial plane along with one atom below and one above. Essentially trigonal bipyramidal, but instead of only 3 atoms in the middle it's 5 instead.
Sun Nov 17, 2019 1:54 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Large Molecules
Replies: 2
Views: 26

### Large Molecules

How does VSEPR apply when it comes to large molecules like carbon chains that don't really have a central atom?
Sun Nov 17, 2019 1:49 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Pentagonal Bipyramidal
Replies: 8
Views: 99

### Re: Pentagonal Bipyramidal

Pentagonal Bipyramidal is AX7, so one more bonding site than octahedral (AX6).
Sat Nov 16, 2019 8:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 5
Views: 79

### Re: Bond Angles

Similarly, molecules that have more atoms will have decreased bond angles as there are more regions of electron density surrounding the central atom making it more cramped.
Sat Nov 16, 2019 8:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 4
Views: 64

### Bond Angles

What causes different molecules with the same VSEPR shape to have slightly different bond angles from each other?
Sat Nov 16, 2019 8:24 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: Potential energy
Replies: 1
Views: 34

### Re: Potential energy

It's the energy generated from the interaction between two molecules. The more polar the molecules and the smaller the radius between them, the more energy present from the interaction. This type of energy is potential rather than kinetic as the molecules have this energy from their relative positio...
Sun Nov 10, 2019 1:17 pm
Forum: Bond Lengths & Energies
Topic: Strength of Interactions
Replies: 3
Views: 45

### Re: Strength of Interactions

The stronger the interactions between molecules, the more energy/heat required to separate them from each other, which raises the boiling/melting points of the molecule.
Sun Nov 10, 2019 1:05 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: H20 and H2S melting/boiling point
Replies: 4
Views: 40

### Re: H20 and H2S melting/boiling point

Molecules with greater bond strength from their interactions will be harder to separate, thus requiring more energy/heat to break the bonds (raising the melting/boiling points) allowing a solid to become a liquid, or a liquid a gas.
Sun Nov 10, 2019 1:00 pm
Forum: Octet Exceptions
Topic: Octet Exception
Replies: 8
Views: 223

### Octet Exception

Is the expansion of the octet rule limited only to an element's d-block, or can the f-block store electrons too? Any examples of this happening?
Sun Nov 10, 2019 12:56 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: Interaction Energy Calculation
Replies: 3
Views: 45

### Interaction Energy Calculation

When using the formula for interaction energy how is the polarizability (alpha) calculated for each molecule?
Sun Nov 10, 2019 12:33 pm
Forum: Bond Lengths & Energies
Topic: Hydrogen Bonding
Replies: 3
Views: 55

### Re: Hydrogen Bonding

I'm pretty sure hydrogen bond strength will vary depending on how polarized the atoms are that hydrogen interacts with. I'm not sure on the calculation for that specific number, but I assume -20kj/mol is just the strength of the attractive force on average.
Sat Nov 02, 2019 6:40 pm
Forum: Electronegativity
Topic: Electronegativity and charge
Replies: 2
Views: 45

### Re: Electronegativity and charge

Difference in electronegativity really only gives information about the character of the bond, whether it is more ionic or covalent, depending upon the constituent elements.
Sat Nov 02, 2019 5:51 pm
Forum: Lewis Structures
Topic: double bonds
Replies: 2
Views: 34

### Re: double bonds

Fluorine only goes up to the second shell regarding orbitals, so it is unable to hold an expanded octet as higher numbered atoms can. Because of this, Fluorine can only hold a standard octet, and starting off with seven valence electrons, only has enough space in its valence to take one more electro...
Sat Nov 02, 2019 5:47 pm
Forum: Electronegativity
Topic: What is isoelectronic?
Replies: 13
Views: 116

### Re: What is isoelectronic?

Isoelectronic simply refers to two atoms that have the same amount of electrons. For instance, Neon has 10 electrons as does Fluorine-, which starts with 9 electrons but gains another to have 10 total, so these two atoms are isoelectronic.
Sat Nov 02, 2019 5:41 pm
Forum: Coordinate Covalent Bonds
Topic: Atom Sharing
Replies: 5
Views: 90

### Atom Sharing

Aside from that one atom donates both electrons to form a coordinate covalent bond, are there any other characteristics that differ between a coordinate and regular covalent bond?
Sat Nov 02, 2019 5:39 pm
Forum: Coordinate Covalent Bonds
Topic: Bond Formation
Replies: 2
Views: 62

### Bond Formation

Is there any particular reason why some atoms form coordinate covalent bonds? Is it just to from octets or as a result of electronegativity?
Sat Oct 26, 2019 5:00 pm
Forum: Ionic & Covalent Bonds
Topic: Effective charge
Replies: 3
Views: 48

### Effective charge

What effect is there on the nuclear charge when atoms gain expanded valence shells? Does moving electrons to the d-block increase electron shielding?
Sat Oct 26, 2019 4:47 pm
Forum: Properties of Light
Topic: emission vs absorption
Replies: 2
Views: 45

### Re: emission vs absorption

The emission and absorption spectra are essentially opposites of each other. The emission spectra will show the specific wavelengths given off, while the absorption spectra will show these specific wavelengths taken in by the atom. The wavelengths present in emission will be the ones absent in absor...
Sat Oct 26, 2019 4:39 pm
Forum: Ionic & Covalent Bonds
Topic: Expanded Valence Shells
Replies: 4
Views: 57

### Re: Expanded Valence Shells

Expanded valence shells occur once you get to n=3 on the periodic table as at that point there start to be d-block orbitals. Elements after n=3 can use the d-block as a form of storage for the extra electrons allowing for the atom to be stable even outside the standard configuration of an octet.
Sat Oct 26, 2019 4:34 pm
Forum: Ionic & Covalent Bonds
Topic: Electronegativity and electron affinity
Replies: 3
Views: 34

### Re: Electronegativity and electron affinity

Regarding electron affinity, because energy is released when an electron is added to an atom it makes the configuration of the atom more stable, which is why higher electron affinity (ie. more energy released) corresponds to the likelihood of the atom accepting an electron. Lower electron affinity m...
Sat Oct 26, 2019 4:16 pm
Forum: Einstein Equation
Topic: Usage of Einstein Equation
Replies: 2
Views: 164

### Re: Usage of Einstein Equation

In addition, be careful not to mistakenly use this equation when regarding electrons, Einstein equation is only intended for photons.
Sat Oct 19, 2019 12:06 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: building up principle
Replies: 5
Views: 59

### Re: building up principle

Also, in orbitals where different configurations are present (ie. px, py, and pz for the p orbital), electrons will move to occupy each configuration and having parallel spin before pairing up within an orbital to maintain a lower energy state
Sat Oct 19, 2019 11:56 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shell/Orbital Energies
Replies: 2
Views: 30

### Re: Shell/Orbital Energies

That makes a lot more sense now. Thanks!!!
Sat Oct 19, 2019 10:55 am
Forum: DeBroglie Equation
Topic: Rydberg and De Brogile
Replies: 3
Views: 79

### Re: Rydberg and De Brogile

To add on, De Broglie's equation should only be used for particles/objects with mass, never with light. Regarding light and other forms of EM radiation, the main equations to be used will be either v*lambda = c and E = hv.
Sat Oct 19, 2019 10:36 am
Forum: Quantum Numbers and The H-Atom
Topic: Principal Quantum Number
Replies: 3
Views: 54

### Principal Quantum Number

How is the Principal Quantum Number (n) calculated for a certain atom? Is it based off of the period of an element? If so does atom excitation affect n?
Sat Oct 19, 2019 9:57 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shell/Orbital Energies
Replies: 2
Views: 30

### Shell/Orbital Energies

Can anyone explain why higher numbered shells have higher energy than lower number shells as well as the same for orbitals (ie. s has less energy than p which has less than d)?
Sun Oct 13, 2019 2:24 am
Forum: Properties of Light
Topic: de broglies equation
Replies: 6
Views: 113

### Re: de broglies equation

De Broglie's equation (wavelength = h/p) is calculated using both Planck's constant (h) and momentum (p) to determine wavelength. Momentum equals mass times velocity (p=mv), therefore you can extend the equation to [wavelength = h/(mv)]. With this is mind, De Broglie's equation should be used if a q...
Sun Oct 13, 2019 1:27 am
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 6
Views: 94

### Re: Photoelectric Effect

The energy of light is based off of the equation E=hv, where h = Planck's constant and v = frequency. Since v is the only variable that isn't constant, you're correct in stating that only an increase in frequency will change the energy of light, amplitude isn't even a factor in the energy equation.
Sun Oct 13, 2019 12:49 am
Forum: Photoelectric Effect
Topic: Why do photons not obey the wave equation?
Replies: 6
Views: 131

### Re: Why do photons not obey the wave equation?

Because of the particle quality of a photon, the interaction between photons and electrons occur one to one, that is the energy from only a single photon is transferred to one electron. If the energy of this single interaction does not meet the work function threshold, the electron will not be eject...
Sun Oct 13, 2019 12:21 am
Forum: Properties of Electrons
Topic: Series
Replies: 2
Views: 44

### Re: Series

Each of the series are differentiated by the starting energy level of the electron belonging to the hydrogen atom. Lyman has a starting energy level of n=1, Balmer n=2, Paschen n=3, etc.
Sun Oct 13, 2019 12:10 am
Forum: Properties of Electrons
Topic: Electron Quantum Energies
Replies: 3
Views: 46

### Re: Electron Quantum Energies

The quantization between energy states of electrons is due to the wave-like properties possessed by an electron. The electron is represented as a circular standing wave around the nucleus of an atom. The amount of energy absorbed by an electron will alter its wavelength and frequency, thereby changi...
Thu Oct 03, 2019 9:59 pm
Forum: SI Units, Unit Conversions
Topic: 2.Mass Percentage and Decimal Rounding:
Replies: 10
Views: 125

### Re: 2.Mass Percentage and Decimal Rounding:

Most elements on the periodic table are typically given to the hundredths place, so it's best to match that when using percentages so the number of sig figs match up.
Thu Oct 03, 2019 9:54 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E. Moles and Molar Masses
Replies: 2
Views: 43

### Re: E. Moles and Molar Masses

Sulfide is on the right side of the periodic table, so it's the anion that will replace the OH. Use subtraction to figure out the mass of mystery element M. Then add that value to the mass of sulfur to find the total mass of the sulfide compound.
Thu Oct 03, 2019 9:45 pm
Forum: Significant Figures
Topic: Sig Fig Rules
Replies: 3
Views: 103

### Re: Sig Fig Rules

Also, when you're working with values with different numbers of sig figs, your answer should use the lowest amount of sig figs present (ie. 2.56 * 4.1 = your answer should be rounded off to two sig figs 10.)
Thu Oct 03, 2019 4:39 pm
Forum: Empirical & Molecular Formulas
Topic: Calculating Empirical Formula with Given Amounts of Each Element
Replies: 7
Views: 85

### Calculating Empirical Formula with Given Amounts of Each Element

When calculating the empirical formula of a compound and the masses of each element are given, is it necessary to convert the amount of each into a percentage of the actual mass then use the % out of 100g to find the mol ratio, or can you just go from the amounts given to the number of moles of each...
Tue Oct 01, 2019 4:29 pm
Forum: Balancing Chemical Reactions
Topic: Combustion Reaction Notation
Replies: 6
Views: 105

### Re: Combustion Reaction Notation

No. From the examples given in the textbook (pg F63) on combustion reactions, there isn't any symbol or change made to the basic format of the chemical equation regarding combustion specifically. So while, like you said a spark may be necessary to initiate the reaction it looks like that information...