Search found 100 matches

by Sydney Pell 2E
Sun Mar 15, 2020 2:11 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pH of acids
Replies: 11
Views: 246

Re: pH of acids

At the same concentration, weak acids will not dissociate as much as strong acids will. This means that weak acids have lower concentrations of H3O+ and therefore their pH will be closer to 7 while strong acids will have much lower pH because of their higher hydronium concentration.
by Sydney Pell 2E
Sun Mar 15, 2020 2:01 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: H2O
Replies: 8
Views: 89

Re: H2O

Solids and liquids are not factored into the calculations for equilibrium constants (and therefore in ICE tables) because their concentrations are not changing.
by Sydney Pell 2E
Sun Mar 15, 2020 1:59 pm
Forum: Calculating Work of Expansion
Topic: Integral
Replies: 2
Views: 66

Re: Integral

Work of expansion at constant pressure has to incorporate volume because expansion is a change in volume. So, to calculate the work needed to change the volume,the integral should involve the volumes.
by Sydney Pell 2E
Sun Mar 15, 2020 1:54 pm
Forum: Calculating Work of Expansion
Topic: reversible expansion
Replies: 4
Views: 64

Re: reversible expansion

The area under the reversible expansion curve is the work done during the expansion. You can solve for this using the integral formula for reversible expansion, as the definition of an integral is the area underneath the curve.
by Sydney Pell 2E
Thu Mar 12, 2020 2:00 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: determining k
Replies: 6
Views: 41

Re: determining k

As long as you have the corresponding reaction rate and the concentrations of the reactants/products, you can use any trial to determine k.
by Sydney Pell 2E
Sun Mar 08, 2020 11:10 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Termolecular Molecularity
Replies: 5
Views: 45

Re: Termolecular Molecularity

The reason termolecular reactions are so rare is that three molecules must collide simultaneously for it to occur. The more molecules needed, the lower the probability of the reaction occurring, which is why termolecular reactions are very uncommon.
by Sydney Pell 2E
Sun Mar 08, 2020 11:07 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow step vs. fast step
Replies: 3
Views: 30

Re: Slow step vs. fast step

Why aren't the fast steps also factored into the overall reaction rate law?
by Sydney Pell 2E
Sun Mar 08, 2020 10:58 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: microscopic reversibility
Replies: 3
Views: 22

microscopic reversibility

When can we assume that a reaction has microscopic reversibility?
by Sydney Pell 2E
Sun Mar 08, 2020 10:55 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A in the Arrhenius Equation
Replies: 8
Views: 70

Re: A in the Arrhenius Equation

How would you calculate the value of A to put in the Arrhenius equation? Would it need to be given to you?
by Sydney Pell 2E
Sun Mar 01, 2020 10:58 pm
Forum: General Rate Laws
Topic: Differential Rate Law
Replies: 3
Views: 55

Re: Differential Rate Law

Differential rate laws are a function of the concentration of the reactant. So, the differential rate laws compare Rate vs. [R].
by Sydney Pell 2E
Sun Mar 01, 2020 10:40 pm
Forum: General Rate Laws
Topic: Overall reaction order
Replies: 4
Views: 61

Re: Overall reaction order

Rate 2 is divided by Rate 1. Since the concentration of [NH4+] stays the same in reactions 1 and 2, these values and their units cancel out. k also cancels out when the two rates are divided. So, the only components left in the calculation are initial rate 2/initial rate 1 (which is equal to 2) and ...
by Sydney Pell 2E
Sun Mar 01, 2020 9:55 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Method 1
Replies: 3
Views: 65

Re: Method 1

This above method can also be used to determine the order of the reaction. The order of the reaction can be calculated by adding together the exponents of the reactants (n, m...).
by Sydney Pell 2E
Sun Mar 01, 2020 9:43 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: reactant vs product
Replies: 4
Views: 63

Re: reactant vs product

We focus more on [R] than [P] because it is easier to observe the initial rates of the reaction when t is very close to t=0. There are more reactants present than products at the beginning of the reaction so it is easier to measure the initial reaction rate if we examine [R].
by Sydney Pell 2E
Sun Mar 01, 2020 9:40 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: first order
Replies: 8
Views: 71

Re: first order

A first order reaction has a reaction rate in the form of k[A]^1.
by Sydney Pell 2E
Sun Feb 23, 2020 10:50 pm
Forum: Van't Hoff Equation
Topic: deltaS/R
Replies: 7
Views: 86

Re: deltaS/R

When comparing temperatures, deltaS and deltaH are assumed to stay constant for both temperatures which could be why deltaS/R seems to be ignored.
by Sydney Pell 2E
Sun Feb 23, 2020 10:42 pm
Forum: Van't Hoff Equation
Topic: Thermo in Test 2
Replies: 6
Views: 69

Re: Thermo in Test 2

The second page of outline 4 will be on test 2. This includes Gibbs Free Energy, the van't Hoff equation, work, and understanding how to implement these concepts in organic reactions, and environmental and biological examples.
by Sydney Pell 2E
Sun Feb 23, 2020 10:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: | divider in cell diagram
Replies: 5
Views: 42

Re: | divider in cell diagram

If the two were in different phases, would there then need to be a 'I' separating them?
by Sydney Pell 2E
Sun Feb 23, 2020 10:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge vs. Porous Disk
Replies: 2
Views: 26

Salt Bridge vs. Porous Disk

What is the difference between a salt bridge and a porous disk?
by Sydney Pell 2E
Sun Feb 23, 2020 10:08 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: salt bridge
Replies: 9
Views: 64

Re: salt bridge

A salt bridge helps the two solutions in a Galvanic cell maintain neutrality through ion transfer, thus preventing charge buildup.
by Sydney Pell 2E
Sun Feb 16, 2020 6:31 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: Finding the value of W
Replies: 2
Views: 79

Re: Finding the value of W

W, or degeneracy, is defined as the number of ways of achieving a given energy state. It can be calculated by counting the number of particles and the number if arrangements/states they could be in. For example, if 2 particles could be in one of two states, W=4, or 2^2. The number of particles is ra...
by Sydney Pell 2E
Sun Feb 16, 2020 6:27 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: Residual Entropy
Replies: 6
Views: 133

Re: Residual Entropy

Residual entropy (the remaining entropy of molecules when thermal entropy is ignored) is calculated using the equation S= kB lnW.
by Sydney Pell 2E
Sun Feb 16, 2020 5:50 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: Boltzmann Equation
Replies: 10
Views: 85

Re: Boltzmann Equation

The Boltzmann equation is used to represent the relationship between degeneracy, w, and entropy. Degeneracy is the number of ways of achieving a given energy state. The Boltzmann equation also includes the Boltzmann constant which is 1.381*10^-23 J*K^-1. Can we calculate degeneracy? If so how? Dege...
by Sydney Pell 2E
Wed Feb 12, 2020 5:18 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Pizza Roll's
Replies: 3
Views: 72

Re: Pizza Roll's

Step one is raising the temperature of the reactants to 200C. Step 2 is the actual reaction at 200C (deltaH is given). Step 3 is cooling the products back down to 37C. Add all these values together to get the total change in enthalpy of the reaction. What equations would you use to raise the temper...
by Sydney Pell 2E
Wed Feb 12, 2020 12:47 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: Pizza Rolls 5H
Replies: 1
Views: 37

Pizza Rolls 5H

Why does Lead have a higher molar entropy than Carbon?
by Sydney Pell 2E
Sun Feb 09, 2020 5:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Nonlinear vs linear molecules
Replies: 4
Views: 51

Re: Nonlinear vs linear molecules

I'm pretty sure that generally, nonlinear molecules will have higher molar heat capacities than linear molecules. For example, in 4C.1 from the textbook, NO2 (bent) has higher molar heat capacity than NO (linear).
by Sydney Pell 2E
Sun Feb 09, 2020 5:00 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Learning outcome fossil fuels
Replies: 2
Views: 57

Learning outcome fossil fuels

On the learning outcomes sheet for "Thermochemistry and the First Law of Thermodynamics" from Dr. Lavelle's class website, it says we should "understand the environmental impact of burning fossil fuels, and the use of alternative fuels as energy sources." Can someone explain how ...
by Sydney Pell 2E
Sun Feb 09, 2020 4:53 pm
Forum: Phase Changes & Related Calculations
Topic: phase changes, temperature constant?
Replies: 11
Views: 125

Re: phase changes, temperature constant?

When heating a substance, for example, water, the heat energy is used to first raise the temperature to the boiling point. When the temperature gets to that point, the heat energy is then used to complete the phase change instead of raising the temperature further. So, the boiling water would stay a...
by Sydney Pell 2E
Sun Feb 09, 2020 4:31 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Intensive vs Extensive
Replies: 7
Views: 72

Intensive vs Extensive

What does it mean when properties are intensive vs extensive? For example, what makes entropy extensive?
by Sydney Pell 2E
Wed Feb 05, 2020 10:40 am
Forum: Calculating Work of Expansion
Topic: Reversible vs. Irreversible
Replies: 3
Views: 59

Reversible vs. Irreversible

What makes an expansion reversible vs irreversible?
by Sydney Pell 2E
Sun Feb 02, 2020 9:18 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Changing the energy of a system
Replies: 9
Views: 55

Re: Changing the energy of a system

To change the energy of a system, you can add or remove the amount of the substance in the system, although this only applies to open systems. The second way to change energy is heat or cool the system (for a closed system). The third way to change the energy of a system is to do work on the system/...
by Sydney Pell 2E
Sun Feb 02, 2020 9:15 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Identifying
Replies: 4
Views: 38

Re: Identifying

It is important to know what kind of system is present because the type of system will determine whether energy and pressure have to be constant or if they can change so that you can complete accurate calculations and choose the correct equations to use.
by Sydney Pell 2E
Sun Feb 02, 2020 8:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Forming bonds
Replies: 8
Views: 59

Forming bonds

Why is bond formation exothermic?
by Sydney Pell 2E
Sun Feb 02, 2020 8:53 pm
Forum: Phase Changes & Related Calculations
Topic: Relevance of Phase Changes
Replies: 9
Views: 67

Re: Relevance of Phase Changes

When you are calculating the enthalpy of a reaction, sometimes the reactants or products will be in the liquid form. Since predetermined enthalpy values of elements are usually given in the gas phase, you must add/subtract the enthalpies of the phase changes to these values to determine what they ar...
by Sydney Pell 2E
Sun Feb 02, 2020 8:32 pm
Forum: Phase Changes & Related Calculations
Topic: Liquid/Steam
Replies: 3
Views: 38

Re: Liquid/Steam

When water is boiled to 100 degrees C, some of it is converted to steam. Water as steam has more energy than liquid water because it requires additional energy as enthalpy of vaporization as it turns to gas. So, steam at 100 degrees Celsius has the energy of water at 100 degrees C plus the enthalpy ...
by Sydney Pell 2E
Wed Jan 22, 2020 8:18 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: chem module 1a question
Replies: 2
Views: 34

Re: chem module 1a question

K does give the relative concentrations of products to reactants when the equation is at equilibrium. This is because it is calculated using [Products]/[Reactants], thus showing us the ratio of products to reactants. A large K value (greater than 10^3) means more products at equilibrium than reactan...
by Sydney Pell 2E
Wed Jan 22, 2020 8:12 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: chem module 1a question
Replies: 2
Views: 26

Re: chem module 1a question

Speeding up the reaction would not influence the concentrations of the reactants nor products at equilibrium. Equilibrium is not affected by the speed of the reaction.
by Sydney Pell 2E
Wed Jan 22, 2020 8:05 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: "shifting" eq?
Replies: 3
Views: 47

Re: "shifting" eq?

If K is a large number (larger than 1 x 10^3), then that means at equilibrium, more products are present than reactants and the equilibrium is shifted right. If K is a small number, (smaller than 1 x 10^-3), then at equilibrium, more reactants are present than products and the equilibrium is shifted...
by Sydney Pell 2E
Wed Jan 22, 2020 1:16 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Changes in K
Replies: 2
Views: 30

Changes in K

How is K affected when the chemical equation it's based on is multiplied by a factor?
by Sydney Pell 2E
Tue Jan 21, 2020 11:30 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6A.21
Replies: 2
Views: 29

6A.21

The value of Kw for water at body temperature (37 C) is 2.1 x 10^14. (a) What is the molar concentration of H3O+ ions at 37 C? (b) What is the molar concentration of OH- in neutral water at 37 C? In this problem, how would you find the molar concentration of H3O+ ions? Would the concentrations of H...
by Sydney Pell 2E
Sun Jan 19, 2020 10:47 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Buffers
Replies: 3
Views: 31

Re: Buffers

The purpose of a buffer is to resist PH changes in a solution, helping to keep the solution's PH constant despite additions of acids or bases. A buffer can be made from a weak acid or a weak base and their respective salts, or from a combination of 2 salts that form a conjugate acid-base pair.
by Sydney Pell 2E
Sun Jan 19, 2020 10:43 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Conjugate Seesaw
Replies: 2
Views: 45

Re: Conjugate Seesaw

The most important part of the conjugate seesaw is that the strength of an acid determines the strength of its conjugate base. A stronger acid will have a weaker conjugate base, and a weak acid will have a strong conjugate base. The same applies to bases and their conjugate acids. A strong base will...
by Sydney Pell 2E
Sun Jan 19, 2020 10:39 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Factors affecting K
Replies: 2
Views: 29

Factors affecting K

Why does the temperature change the value of K while pressure and concentration don't?
by Sydney Pell 2E
Sun Jan 19, 2020 9:11 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: X was ignored
Replies: 27
Views: 177

Re: X was ignored

Why do we see if our approximation is correct by checking if the final answer is less than 5% of the initial? Is there a particular reason we use 5% as the cutoff?
by Sydney Pell 2E
Sun Jan 19, 2020 8:41 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Not including solids and liquids
Replies: 7
Views: 73

Re: Not including solids and liquids

K is calculated with the concentration of the products over the concentration of the reactants at equilibrium. Since solids and liquids in a reaction do not change concentrations, they would just cancel out when calculating the equilibrium constant. So, only gases are considered when calculating K.
by Sydney Pell 2E
Sun Jan 12, 2020 7:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reaction Quotient Q
Replies: 6
Views: 34

Re: Reaction Quotient Q

Both Q and K are calculated the same way. Both are the concentration of the products over the concentration of the reactants. K is that value when the reaction is at equilibrium and Q is that value at any other time.
by Sydney Pell 2E
Sun Jan 12, 2020 6:17 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Chatelier's Principle
Replies: 7
Views: 58

Re: Chatelier's Principle

Chatelier's principle can be used to see which direction a reaction will proceed in response to a change in concentration or pressure. For example, if more reactants are added, therefore increasing concentration, Le Chatelier's principle tells us that the reaction will move forward in order to minim...
by Sydney Pell 2E
Sun Jan 12, 2020 5:41 pm
Forum: Ideal Gases
Topic: PV = nRT Confusion
Replies: 4
Views: 65

Re: PV = nRT Confusion

PV=nRT is the ideal gas equation. it can be used to convert between partial pressure and concentration for a gas, which means it can help us find Kc from Kp and vice versa.
by Sydney Pell 2E
Sun Jan 12, 2020 5:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Different types of K
Replies: 9
Views: 58

Re: Different types of K

The notation of K depends on what information they give you in the equation and what phase it occurs in. If the problem gives you the partial pressures of the gases in the reaction, you would be using Kp. If the molar concentrations are given, then Kc. Either way, K always stands for the equilibrium...
by Sydney Pell 2E
Sun Jan 12, 2020 2:45 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Partial Pressures
Replies: 4
Views: 40

Re: Partial Pressures

PranaviKolla2B wrote:What are partial pressures?


If you have a mixture of gases in a container, the partial pressure would be the pressure each individual gas exerts on the container. The partial pressures added together equals the total pressure of the mixture.
by Sydney Pell 2E
Sun Dec 08, 2019 10:30 am
Forum: Biological Examples
Topic: Heme complex
Replies: 5
Views: 114

Heme complex

What is the biological importance of the heme complex?
by Sydney Pell 2E
Sun Dec 08, 2019 10:26 am
Forum: Biological Examples
Topic: Hemoglobin and Myoglobin
Replies: 4
Views: 122

Re: Hemoglobin and Myoglobin

What is the function of hemoglobin and myoglobin?
by Sydney Pell 2E
Sun Dec 08, 2019 10:24 am
Forum: Biological Examples
Topic: Cis vs Trans
Replies: 3
Views: 103

Re: Cis vs Trans

An example of this that was used in class is cisplatin and transplatin. In cisplatin, the Cl atoms are on one side of the central Pt and the NH3 molecules are bonded the opposite side. In transplatin, one Cl and one NH3 switch places so that the Cls and NH3s are diagonal from each other instead of s...
by Sydney Pell 2E
Sun Dec 08, 2019 10:11 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ka only in weak acids and bases?
Replies: 2
Views: 84

Ka only in weak acids and bases?

Why are Ka calculations are only used for weak acid and bases?
by Sydney Pell 2E
Sun Dec 08, 2019 10:04 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Carboxylic Acid
Replies: 2
Views: 115

Carboxylic Acid

What is the difference between a carboxylic acid and an oxoacid? How can you tell which is which?
by Sydney Pell 2E
Sun Dec 01, 2019 10:20 pm
Forum: Lewis Acids & Bases
Topic: Oxoacids
Replies: 3
Views: 32

Re: Oxoacids

Oxoacids are oxygen-containing inorganic acids. The strength of an oxoacid depends on the number of oxygens (more O atoms = stronger), the electronegativity of the center atom (Higher EN = stronger), and the oxidation number of the center atom (bigger # = stronger).
by Sydney Pell 2E
Sun Dec 01, 2019 10:16 pm
Forum: Conjugate Acids & Bases
Topic: the conjugate seesaw
Replies: 5
Views: 74

Re: the conjugate seesaw

A conjugate acid is what is created when the base receives a proton as it dissociates in an aqueous solution. Conjugate acids are weak acids because they can now donate the proton they received back to where they received it from to become a base again (this act of donating a proton makes it an acid...
by Sydney Pell 2E
Sun Dec 01, 2019 10:03 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: notes
Replies: 2
Views: 49

Re: notes

This pretty much means that oxoacids can dissociate better and thus are stronger acids when, after giving off a proton, they are able to delocalize the negative charge. This means that oxoacids composed of atoms with similar electronegativities (and therefore would delocalize the charge) will be mor...
by Sydney Pell 2E
Sun Dec 01, 2019 8:25 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong Acids
Replies: 3
Views: 36

Re: Strong Acids

Strong acids are able to completely dissociate in a solution to donate their protons. Most strong acids are inorganic.
by Sydney Pell 2E
Sun Dec 01, 2019 8:20 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH Calculation explanation
Replies: 1
Views: 24

pH Calculation explanation

Can someone explain why you have to take the negative log of the H+ concentration to find pH? Why is it negative?
by Sydney Pell 2E
Sun Nov 24, 2019 9:19 pm
Forum: Amphoteric Compounds
Topic: Amphiprotic
Replies: 11
Views: 115

Re: Amphiprotic

Yes, H20 is amphiprotic because it can can accept or donate a proton.
by Sydney Pell 2E
Sun Nov 24, 2019 7:34 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: What are coordination numbers?
Replies: 3
Views: 44

Re: What are coordination numbers?

The coordination number is the number of bonds around the central metal in the coordination compound.
by Sydney Pell 2E
Sun Nov 24, 2019 7:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 5
Views: 40

Re: Ligands

A ligand is an ion or molecule with at least one lone pair of e- that forms a coordinate covalent bond with a central metal atom.
by Sydney Pell 2E
Wed Nov 20, 2019 12:48 pm
Forum: Hybridization
Topic: 2F:7.d
Replies: 2
Views: 35

Re: 2F:7.d

The number of hybridized orbitals is equal to the number of atomic orbitals around the central atom. So, the hybridization is sp3 to match the four atomic orbitals around the central atom that is seen in its Lewis structure.
by Sydney Pell 2E
Wed Nov 20, 2019 12:38 pm
Forum: Hybridization
Topic: Is hybridized orbitals all weighed equally in character?
Replies: 4
Views: 44

Re: Is hybridized orbitals all weighed equally in character?

Yes, the hybridized orbitals are an average of the s, p, and d orbitals which means they should be weighed equally.
by Sydney Pell 2E
Sun Nov 17, 2019 3:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion
Replies: 6
Views: 61

Re: Repulsion

In order of most repulsion strength to least repulsion strength according to the VSEPR model, the order is lone pair-lone pair > Lone pair-bonding pair > Bonding pair-bonding pair.
by Sydney Pell 2E
Sun Nov 17, 2019 3:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Can there be lone pairs on the central atom if the shape is linear?
Replies: 4
Views: 37

Re: Can there be lone pairs on the central atom if the shape is linear?

If two lone pairs were added to the central atom, the molecule would then have four areas of electron density and so the electron geometry would be tetrahedral and the molecular geometry would then be bent since there are 2 bonding pairs. So, a molecule can only be linear if the central atom only ha...
by Sydney Pell 2E
Sun Nov 17, 2019 2:57 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Trigonal Pyramidal?
Replies: 4
Views: 42

Re: Trigonal Pyramidal?

There are four regions of electron density, which means the electron geometry is tetrahedral. Since one is a lone pair, the molecular geometry is trigonal pyramidal.
by Sydney Pell 2E
Sun Nov 17, 2019 2:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Trigonal Pyramidal?
Replies: 4
Views: 42

Re: Trigonal Pyramidal?

A trigonal planar molecule must have no more than three areas of electron density, and all three must be bonding pairs. SO3 (2-) has three bonding pairs, but since it also has a lone pair, it would then be trigonal pyramidal since the lone pair would repulse the bonding pairs away from it.
by Sydney Pell 2E
Sun Nov 17, 2019 2:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Structure of H2O
Replies: 3
Views: 40

Re: Structure of H2O

The lone pairs in H2O are not opposite each other because H2O has four areas of electron density and therefore is in tetrahedral electron geometry. It would not matter which two pairs of electrons are the lone pairs because no matter what the molecular geometry will be bent.
by Sydney Pell 2E
Sun Nov 10, 2019 11:54 pm
Forum: Properties of Light
Topic: How to find the longest wavelength?
Replies: 6
Views: 202

Re: How to find the longest wavelength?

The kintetic energy (Ek) would be equal to zero because if you want to find the longest wavelength of light that is able to eject an electron, that means that there is no energy left over (Ek) because all of it is used to eject the electron (the work function). So, set the energy of the photon (Ep) ...
by Sydney Pell 2E
Sun Nov 10, 2019 11:47 pm
Forum: Trends in The Periodic Table
Topic: Ionization
Replies: 5
Views: 245

Re: Ionization

Is this the only exception to the general trend for ionization energy? ( That ionization energy increases across a period and decreases down a group?) Or do all group 16 elements have lower ionization energies than their preceding group 15 element?
by Sydney Pell 2E
Sun Nov 10, 2019 11:42 pm
Forum: Resonance Structures
Topic: Negative Charge
Replies: 3
Views: 36

Re: Negative Charge

The more electronegative atom will carry the negative charge because it wants to have more electrons.
by Sydney Pell 2E
Sun Nov 10, 2019 11:35 pm
Forum: Ionic & Covalent Bonds
Topic: Both types of bonds
Replies: 6
Views: 59

Re: Both types of bonds

Covalent bonds have ionic characteristics if they share their electron unequally (if one element is more electronegative than the other, but not enough to become completely ionic). This is called a polar covalent bond. One side of the molecule is more positively charged and one side is more negative...
by Sydney Pell 2E
Sun Nov 10, 2019 8:37 pm
Forum: Dipole Moments
Topic: Identifying dipoles
Replies: 3
Views: 42

Re: Identifying dipoles

In a way, you have to use the electronegativities of the elements in order to make the lewis structures. So, electronegativity is definitely an important component when it comes to determining dipole moments.
by Sydney Pell 2E
Sun Nov 03, 2019 7:19 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge Purpose
Replies: 4
Views: 65

Re: Formal Charge Purpose

It's also important to remember that if you are drawing an ion, the total formal charges should add up to the overall charge of the ion.
by Sydney Pell 2E
Sun Nov 03, 2019 7:14 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic and Covalent
Replies: 5
Views: 45

Re: Ionic and Covalent

Covalent bonds can have ionic characteristics if the atoms in the molecule share the electron unequally (have different electronegativities/electron affinities). Atoms with higher electronegativity will pull the shared electrons closer to it, thus making it slightly negative. The element that has th...
by Sydney Pell 2E
Sun Nov 03, 2019 6:55 pm
Forum: Lewis Structures
Topic: Lewis Structures and Polarity
Replies: 1
Views: 26

Lewis Structures and Polarity

Does the polarity/dipole moments of molecules play a role when we draw its Lewis structure?
by Sydney Pell 2E
Sun Nov 03, 2019 6:34 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: degenerate orbitals
Replies: 3
Views: 48

Re: degenerate orbitals

Also, how do you find the number of degenerate orbitals an atom has?
by Sydney Pell 2E
Sun Nov 03, 2019 6:14 pm
Forum: Lewis Structures
Topic: Atoms that can accept more than 8 Valence E-
Replies: 3
Views: 49

Re: Atoms that can accept more than 8 Valence E-

The hybridization and mixing of orbitals in period 3 or larger atoms are part of the reason why some atoms can have expanded octets. This is because orbitals in the same shell can mix together because they are similar in energy, which means they can have more orbitals available to fill during bonding.
by Sydney Pell 2E
Sun Oct 27, 2019 10:26 pm
Forum: Ionic & Covalent Bonds
Topic: Valence Electrons
Replies: 3
Views: 36

Re: Valence Electrons

The number of valence electrons depends on where the element is in on the periodic table. For neutral atoms, it is the element's main group number (1-8). Group 1 elements have 1 valence e-, Group 2 had 2 valence e-, and so on. But, if the atom has a charge, then you would take the element's main gro...
by Sydney Pell 2E
Sun Oct 27, 2019 10:21 pm
Forum: Trends in The Periodic Table
Topic: s block metals vs p block metals
Replies: 2
Views: 32

Re: s block metals vs p block metals

P-block metals have high ionization energies, which means it is more difficult for them to lose electrons. But, for some elements in the p-block, this does not necessarily mean that they are less reactive. For example, group 17 elements have high electron affinity, which means that they have a high ...
by Sydney Pell 2E
Sun Oct 27, 2019 10:00 pm
Forum: Resonance Structures
Topic: Bond Length of Single Bond, Double Bond, and Tripler Bond.
Replies: 2
Views: 32

Re: Bond Length of Single Bond, Double Bond, and Tripler Bond.

A double bond is shorter than a single bond because although there are more electrons that would want to repulse each other, the electrostatic pull between the positive nuclei and the now more negatively charged (with 2 electrons shared instead of 1) double bond will overcome this. The pull between ...
by Sydney Pell 2E
Sun Oct 27, 2019 9:24 pm
Forum: Sigma & Pi Bonds
Topic: Single vs. Double bonds
Replies: 15
Views: 155

Re: Single vs. Double bonds

Sometimes, if the structure has resonance, the double bond may not be much longer than the single bond. This occurs only if a species is resonant because all of its possible resonant structures blend, thus creating a partial double bond structure and making the double bond shorter than it otherwise ...
by Sydney Pell 2E
Sun Oct 27, 2019 9:17 pm
Forum: Ionic & Covalent Bonds
Topic: Metals Vs. Nonmetals
Replies: 8
Views: 186

Re: Metals Vs. Nonmetals

The majority of elements are most stable when they have 8 valence electrons, filling up their outer shell. So, elements will either try to lose or gain electrons based on how many electrons they have in their valence shells to begin with. The reason metals will lose their valence electrons to form c...
by Sydney Pell 2E
Sat Oct 19, 2019 9:16 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: determining types of orbitals (?)
Replies: 4
Views: 65

Re: determining types of orbitals (?)

If you remember the blocks on the periodic table as previously mentioned, you can write the electron configuration of the elements. You mostly need to remember that the electrons will fill up the smaller shells first until all the orbitals are full and then will expand to larger shells.
by Sydney Pell 2E
Sat Oct 19, 2019 8:33 pm
Forum: Quantum Numbers and The H-Atom
Topic: n, l, m
Replies: 4
Views: 55

Re: n, l, m

n is the principal quantum number, which describes the electron's energy and size (which shell it's in). l is the Angular Momentum Quantum number, which describes the shape of the orbital of the electron. In this class, we will likely only see l = 0 (s-orbital), 1 (p-orbital), 2 (d-orbital), or 3 (f...
by Sydney Pell 2E
Sat Oct 19, 2019 8:15 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron Configuration Model Confusion
Replies: 3
Views: 40

Re: Electron Configuration Model Confusion

I believe that every time he added another electron, he was diagramming the electron configuration of the next element on the periodic table. He was showing the order of which orbitals get filled up first by electrons.
by Sydney Pell 2E
Sat Oct 19, 2019 2:13 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Paired vs Parallel electrons
Replies: 5
Views: 33

Re: Paired vs Parallel electrons

Thanks! So to clarify, when filling up a subshell, one electron will be in each orbital (parallel to each other) until each orbital is occupied and then after that, the electrons will start pairing up?
by Sydney Pell 2E
Sat Oct 19, 2019 1:36 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Paired vs Parallel electrons
Replies: 5
Views: 33

Paired vs Parallel electrons

What is the difference between when electrons are paired vs parallel? How can you determine this?
by Sydney Pell 2E
Sun Oct 13, 2019 8:34 pm
Forum: Photoelectric Effect
Topic: De Broglie's Equation
Replies: 5
Views: 36

Re: De Broglie's Equation

As long as you have two of the three variables (mass, velocity, or wavelength), you can use De Broglie's Equation to solve for the remaining one. Usually, questions will ask to solve for the wavelength, but the equation could also be manipulated to solve for m or v as well.
by Sydney Pell 2E
Sun Oct 13, 2019 7:52 pm
Forum: Properties of Electrons
Topic: Wavelength properties of electrons
Replies: 4
Views: 51

Re: Wavelength properties of electrons

Typically, if the calculated De Broglie wavelength of an object is less than 10^-15 m, its wave-like properties are not detectable. Electrons and other small particles would have a wavelength that is higher than 10^-15m, so only typically in smaller objects would this be used.
by Sydney Pell 2E
Sun Oct 13, 2019 7:25 pm
Forum: DeBroglie Equation
Topic: Constructive vs. Destructive Interference
Replies: 5
Views: 54

Constructive vs. Destructive Interference

In my notes, it says that diffraction patterns may result from constructive or destructive interference. What is the difference between these two and do they result in different diffraction patterns?
by Sydney Pell 2E
Sun Oct 13, 2019 6:58 pm
Forum: Properties of Light
Topic: Quanta- clear up comparison
Replies: 3
Views: 44

Re: Quanta- clear up comparison

During the lecture, Dr. Lavelle was trying to demonstrate how a stream of water may seem like it is continuous, but if you zoomed in close enough, it is actually made of molecules as the smallest "transferrable" unit. So, the mass of the water poured has to go up by at least one molecule a...
by Sydney Pell 2E
Fri Oct 11, 2019 1:44 pm
Forum: Properties of Light
Topic: Energy Levels and Color of light
Replies: 4
Views: 66

Re: Energy Levels and Color of light

It depends on which levels the electron is jumping to and from. This will determine the amount of excess energy which will then determine the wavelength of light emitted. The color of the light depends on its wavelength. Sometimes, the light emitted will not be in the visible spectrum and so it will...
by Sydney Pell 2E
Fri Oct 04, 2019 2:43 pm
Forum: Significant Figures
Topic: Sig Figs
Replies: 3
Views: 53

Re: Sig Figs

If there was a decimal point at the end (8340. ), then there would have been 4.
by Sydney Pell 2E
Fri Oct 04, 2019 2:18 pm
Forum: Empirical & Molecular Formulas
Topic: Difference between empirical and molecular formulas
Replies: 6
Views: 129

Re: Difference between empirical and molecular formulas

An empirical formula is the relative number of atoms a molecule has. In other words, it's the proportion of each element in a molecule. For example, glucose's empirical formula would be CH2O because for every carbon atom in a glucose molecule, there are 2 hydrogens and 1 oxygen. A molecular formula ...
by Sydney Pell 2E
Fri Oct 04, 2019 2:05 pm
Forum: Molarity, Solutions, Dilutions
Topic: Homework Question H11
Replies: 3
Views: 91

Re: Homework Question H11

For this problem, a good trick to remember is that you should always start balancing the equation with the elements that appear the least number of times. In this case, Fe and C both appear once on the reactant side and once on the product side, while oxygen appears twice on the left and once on the...
by Sydney Pell 2E
Fri Oct 04, 2019 1:55 pm
Forum: SI Units, Unit Conversions
Topic: SI
Replies: 5
Views: 69

Re: SI

I think that understanding the most common prefixes for SI units would not be a bad thing to study, not just for this test but for the entire rest of the class! Being familiar with kilo (10^3), centi (10^-1), milli (10^-3), micro (10^-6), nano (10-9), and pico (10^-12) would be the most helpful so t...
by Sydney Pell 2E
Fri Oct 04, 2019 1:34 pm
Forum: Properties of Light
Topic: Amplitude? [ENDORSED]
Replies: 8
Views: 145

Re: Amplitude? [ENDORSED]

Yes, the amplitude corresponds directly with the intensity of light. So, having a high amplitude would mean the light has high intensity. On the other hand, wavelength (distance between between the peaks) tells you what type of light it is.

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