Search found 87 matches

by Amanda Mei 1B
Sun Feb 16, 2020 8:54 pm
Forum: Van't Hoff Equation
Topic: Hoff Equation
Replies: 4
Views: 15

Re: Hoff Equation

The Van't Hoff Equation shows how the equilibrium constant K depends on temperature. It can be used to calculate K at a different temperature if ΔH° is known, assuming ΔS°is constant.
by Amanda Mei 1B
Sun Feb 16, 2020 8:49 pm
Forum: Balancing Redox Reactions
Topic: Redox Reactions
Replies: 12
Views: 19

Re: Redox Reactions

Redox reactions are also known as oxidation-reduction reactions because both oxidation and reduction occur, in two half-reactions. Electrons are transferred between species, changing the species' oxidation numbers.
by Amanda Mei 1B
Sun Feb 16, 2020 8:47 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delatG= -RTInK
Replies: 2
Views: 11

Re: delatG= -RTInK

To add on, K (equilibrium constant) is easy to measure as opposed to Gibbs Free Energy.
by Amanda Mei 1B
Sun Feb 16, 2020 8:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: endo/exo and temp
Replies: 8
Views: 27

Re: endo/exo and temp

Think of heat as either a reactant being absorbed by the reaction (endothermic) or product being given off the reaction (exothermic). If temperature is increased, the reaction will shift away from the side that the heat is on. If temperature is decreased, heat will shift to that side.
by Amanda Mei 1B
Sat Feb 15, 2020 3:48 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Negative work
Replies: 10
Views: 24

Re: Negative work

When a system pushes against an external force (pressure), it loses energy and thus work is negative. Usually this causes volume to expand.
by Amanda Mei 1B
Fri Feb 07, 2020 10:52 am
Forum: Administrative Questions and Class Announcements
Topic: Grading
Replies: 7
Views: 51

Re: Grading

Lavelle outlines the grading scheme in the syllabus: Weekly Homework (5 pts per week): 50 pts Chemistry Community (5 pts per week): 50 pts Test 1: 50 pts Midterm: 120 pts Test 2: 50 pts Final: 180 pts Total: 500 pts 50% or higher is required to pass with a C- or higher. He said that the class doesn'...
by Amanda Mei 1B
Fri Feb 07, 2020 10:30 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Combustion Reactions
Replies: 4
Views: 21

Re: Combustion Reactions

A combustion reaction involves a hydrocarbon (compounds that contains only carbon and hydrogen) burning in (reacting with) diatomic oxygen to produce carbon dioxide and water. You would balance the O 2 last, and you might need to use a fractional coefficient before multiplying all the coefficients b...
by Amanda Mei 1B
Fri Feb 07, 2020 10:22 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: using ratios for R
Replies: 3
Views: 33

Re: using ratios for R

I believe you also use ratios for R to get everything to have the same units. You can use the ratios of R because they would cancel out (like multiplying by a fraction that equals 1).
by Amanda Mei 1B
Fri Feb 07, 2020 10:20 am
Forum: Phase Changes & Related Calculations
Topic: HW problems 4B.3
Replies: 2
Views: 15

Re: HW problems 4B.3

I got 490 J as well. The solution manual says that's the answer, so the book must be incorrect.
by Amanda Mei 1B
Fri Feb 07, 2020 10:14 am
Forum: Phase Changes & Related Calculations
Topic: Heating Curve Phase Changes
Replies: 11
Views: 28

Re: Heating Curve Phase Changes

Temperature doesn't change during a phase change. Heat added to a substance either raises the temperature or causes a phase change, but not both simultaneously. If a solid is heated at its melting point, its temperature remains the same until it has completely melted because melting requires energy....
by Amanda Mei 1B
Fri Jan 31, 2020 10:49 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Work of expansion equation
Replies: 4
Views: 18

Re: Work of expansion equation

The system must do the work of expansion by pushing against P, the external pressure. The system loses energy due to this work, so the negative sign is put to account for that.
by Amanda Mei 1B
Fri Jan 31, 2020 10:46 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs isolated systems
Replies: 24
Views: 64

Re: Closed vs isolated systems

A closed system is physically closed but not thermodynamically closed, meaning that although matter cannot be exchanged between the system and its surroundings, energy can. An example would be a sealed beaker of water, which doesn't insulate, or a pan with a lid on top of it on the stove. An isolate...
by Amanda Mei 1B
Fri Jan 31, 2020 10:42 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 5
Views: 20

Re: Bond Enthalpies

Aside from the fact that bond enthalpies of non-diatomic molecules are averages from the bonds of many different molecules, their values may vary depending on which chart you use. Since there's no universally agreed upon standard for which molecules are used to determine a bond, those making the cha...
by Amanda Mei 1B
Fri Jan 31, 2020 10:35 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: accuracy of bond enthalpies
Replies: 8
Views: 23

Re: accuracy of bond enthalpies

For all molecules that are not diatomic, their bond enthalpies are averages from the bonds in many different molecules. For example many molecules can have a C-H bond, and the bond enthalpies of each one is different.
by Amanda Mei 1B
Fri Jan 31, 2020 10:30 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated vs Closed [ENDORSED]
Replies: 33
Views: 112

Re: Isolated vs Closed [ENDORSED]

A closed system is physically closed but not thermodynamically closed, meaning that although matter cannot be exchanged between the system and its surroundings, energy can. An example would be a sealed beaker of water, which doesn't insulate, or a pan with a lid on top of it on the stove. An isolate...
by Amanda Mei 1B
Sun Jan 26, 2020 3:49 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: hess's law
Replies: 5
Views: 17

Re: hess's law

Hess's Law states that enthalpy is a state function, so its value is determined by its current state, not the path taken to obtain that state. Thus, the total enthalpy change of a multi-step reaction can be calculated by adding the enthalpy change at each step of the reaction.
by Amanda Mei 1B
Sun Jan 26, 2020 3:46 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ideal Gas QUestions
Replies: 8
Views: 31

Re: Ideal Gas QUestions

If temperature is held constant and there's a decrease in volume, the same amount of molecules will be moving in a smaller space and will collide more often, leading to an increase in pressure. If volume increases, molecules will have more space and collide less frequently, decreasing pressure.
by Amanda Mei 1B
Sun Jan 26, 2020 2:26 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.
by Amanda Mei 1B
Sat Jan 25, 2020 11:15 am
Forum: Phase Changes & Related Calculations
Topic: Steam Burn
Replies: 6
Views: 31

Re: Steam Burn

Lavelle was explaining how getting burned by steam is more severe than getting burned by boiling water. This is because when steam (water in gas form) hits your skin, it undergoes a phase change to become a liquid. This phase change as the steam hits your skin and becomes liquid releases energy, cau...
by Amanda Mei 1B
Sat Jan 25, 2020 11:11 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 5
Views: 21

Re: Hess's Law

Hess's Law states that enthalpy is a state function, so its value is determined by its current state, not the path taken to obtain that state. Thus, the total enthalpy change of a multi-step reaction can be calculated by adding the enthalpy change at each step of the reaction.
by Amanda Mei 1B
Sat Jan 18, 2020 1:32 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Validating Approximation
Replies: 2
Views: 14

Re: Validating Approximation

You would divide what you found to be x by the initial concentration, which is given, then multiple by 100 to get the percentage of the initial concentration that has been deprotonated.
by Amanda Mei 1B
Fri Jan 17, 2020 5:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Tips for Test
Replies: 16
Views: 58

Re: Tips for Test

Yes, we're being tested on chemical equilibrium and acids and bases. I'd review lecture notes and examples and do problems in the textbook.
by Amanda Mei 1B
Fri Jan 17, 2020 5:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quadratic
Replies: 10
Views: 34

Re: Quadratic

Ruby Richter 2L wrote:If you do the quadratic equation and get a positive and negative number would you just discredit the negative number? Why?


Because you can't have a negative concentration
by Amanda Mei 1B
Fri Jan 17, 2020 3:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc & Kp
Replies: 12
Views: 37

Re: Kc & Kp

gabbymaraziti wrote:Can we just use K and not specify Kc or Kp? Or would we be marked down?


I don't think you'll be marked down for using K.
by Amanda Mei 1B
Fri Jan 17, 2020 3:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5 percent rule
Replies: 10
Views: 44

Re: 5 percent rule

Divide the x value that you find by the initial concentration to check if it is less than 5% of the initial concentration (less than 5% is deprotonated). This checks if it is small enough to disregard if being subtracted from the initial concentration, making your calculations much easier.
by Amanda Mei 1B
Sat Jan 11, 2020 3:14 pm
Forum: Ideal Gases
Topic: K vs Q [ENDORSED]
Replies: 7
Views: 44

Re: K vs Q [ENDORSED]

K is the equilibrium constant, while Q is the reaction quotient. Though they are calculated the same way, Q can be calculated at any time during the reaction, while K represents when the reaction is at equilibrium. If Q<K, then [reactants] > [products] and the forward reaction is favored. The opposi...
by Amanda Mei 1B
Sat Jan 11, 2020 3:01 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Temperature- Endothermic and Exothermic Reactions
Replies: 3
Views: 16

Re: Temperature- Endothermic and Exothermic Reactions

There are a couple ways to tell if a reaction is endothermic or exothermic. One way is to see if heat is a reactant of product. If heat is released as a product of the reaction, the reaction is exothermic. If heat is listed on the side of the reactants, it is being absorbed and the reaction is endot...
by Amanda Mei 1B
Sat Jan 11, 2020 2:50 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic and endothermic reactions
Replies: 4
Views: 23

Re: Exothermic and endothermic reactions

You can think of heat like a reactant or product, depending on whether the reaction is endothermic or exothermic, and apply the same rules by Le Chatelier's Principle as you would do with other reactants and products to figure out which way the reaction will shift.
by Amanda Mei 1B
Sat Jan 11, 2020 2:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K values
Replies: 4
Views: 36

Re: K values

K=1 tells you that there is about the same amount of products as there are reactants, so the energies of products and reactants are equal. An equilibrium reaction is dynamic and the forward and reverse reactions are constantly occurring, so it's rare for the two to have the same amount at the same t...
by Amanda Mei 1B
Sat Jan 11, 2020 1:50 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 19
Views: 75

Re: Le Chatelier's Principle

Le Chatelier's Principle can predict the effect of a change in conditions on chemical equilibria. If there is a change in conditions, the equilibrium will shift to counteract the effect of the constraint.
by Amanda Mei 1B
Sat Jan 11, 2020 1:16 pm
Forum: Ideal Gases
Topic: Topics on Test 1
Replies: 37
Views: 175

Re: Topics on Test 1

Definitely the topics on Outline 1, but I don't know if we'll get to Outline 2 by the time of the test.
by Amanda Mei 1B
Sun Dec 08, 2019 10:39 pm
Forum: Limiting Reactant Calculations
Topic: A different way
Replies: 8
Views: 122

Re: A different way

I think this is the best way to do it since many problems ask you how much product will be formed anyway, so you're essentially answering that question while you determine the limiting reactant. Just convert moles of each reactant to moles of the product you'll be looking for.
by Amanda Mei 1B
Sun Dec 08, 2019 10:37 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty
Replies: 5
Views: 37

Re: Uncertainty

Delta x represents the uncertainty in position. You can use Heisenberg's Uncertainty Principle (uncertainty of position)(uncertainty of momentum) is greater than or equal to (Planck's Constant /4 pi).
by Amanda Mei 1B
Sun Dec 08, 2019 10:27 pm
Forum: Calculating the pH of Salt Solutions
Topic: pH
Replies: 6
Views: 45

Re: pH

The pH scale is based on the self-ionization of water, where two water molecules combine to form hydronium and hydroxide ions. pH is a measurement of how acidic a solution is. A higher concentration of the hydronium ion means the solution is acidic and will have a lower pH (below 7), while a higher ...
by Amanda Mei 1B
Sun Dec 08, 2019 10:14 pm
Forum: Biological Examples
Topic: Heme complex & O2
Replies: 5
Views: 34

Re: Heme complex & O2

Yes.
by Amanda Mei 1B
Sun Dec 08, 2019 10:11 pm
Forum: Student Social/Study Group
Topic: Cyanide
Replies: 5
Views: 43

Re: Cyanide

After drawing the Lewis structure, you would count the number of valence electrons of one of the atoms, then subtract the number of bonds that atom makes, then subtract the number of lone electrons on that atom. So valence electrons - (# bonds + # lone electrons).
by Amanda Mei 1B
Sun Dec 08, 2019 10:05 pm
Forum: Administrative Questions and Class Announcements
Topic: curve
Replies: 8
Views: 102

Re: curve

I'm not sure how he's going to curve or how much, but I think he may curve at the end after final grades are determined.
by Amanda Mei 1B
Sat Nov 30, 2019 5:24 pm
Forum: Bronsted Acids & Bases
Topic: Weak Acid
Replies: 2
Views: 25

Re: Weak Acid

Acetic acid only ionizes partly in water (there aren't as many separate acetate and hydrogen ions as whole acetic acid molecules). Acetic acid partially dissociates and releases only some of its hydrogen atoms into the solution and is less capable of losing and donating protons = definition of a wea...
by Amanda Mei 1B
Sat Nov 30, 2019 4:02 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Exam Content
Replies: 14
Views: 80

Re: Final Exam Content

Will the final have more questions about the content we learned after the midterm or will it be cover the entire quarter evenly? I don't think Lavelle mentioned this, but it's worth asking your TA. I'm guessing there will probably be a good chunk of questions on content we learned after the midterm...
by Amanda Mei 1B
Sat Nov 30, 2019 3:16 pm
Forum: Student Social/Study Group
Topic: Final Exam
Replies: 3
Views: 31

Re: Final Exam

It's on Sunday, December 8, from 11:30 am to 2:30 pm.
by Amanda Mei 1B
Sat Nov 30, 2019 3:15 pm
Forum: Student Social/Study Group
Topic: Final
Replies: 2
Views: 23

Re: Final

Lavelle said in an email that Wednesday is the last day we'll learn new material.
by Amanda Mei 1B
Sat Nov 30, 2019 3:10 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Weak Acids & Bases
Replies: 6
Views: 38

Re: Weak Acids & Bases

Weak Acids:
Acetic acid (CH3COOH), carbonic acid (H2CO3), hydrofluoric acid (HF), hydrocyanic acid (HCN), phosphoric acid (H3PO4)

Weak Bases:
Ammonia (NH3), methylamine (CH3NH2), diethylamine ((CH3CH2)2NH)
by Amanda Mei 1B
Sat Nov 30, 2019 2:13 pm
Forum: Hybridization
Topic: Counting Charge Clouds
Replies: 2
Views: 18

Re: Counting Charge Clouds

It doesn't matter what type of bond exists there - it counts as one charge cloud.
by Amanda Mei 1B
Sat Nov 30, 2019 1:44 pm
Forum: Administrative Questions and Class Announcements
Topic: Chemistry Community Posts
Replies: 10
Views: 101

Re: Chemistry Community Posts

They should be added weekly but sometimes take a while to be added to your grade
by Amanda Mei 1B
Sun Nov 24, 2019 8:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: T Shape
Replies: 3
Views: 24

Re: T Shape

Trigonal bipyramidal is a type of electron arrangement or geometry, while T-shape is a type of molecular geometry. Any time there are 5 electron groups, the molecule has a trigonal bipyramidal electron arrangement. Lone pairs of electrons are taken into account for molecular geometry. Yes, the rest ...
by Amanda Mei 1B
Sun Nov 24, 2019 8:19 pm
Forum: Lewis Structures
Topic: Bent or Angular?
Replies: 15
Views: 95

Re: Bent or Angular?

Both are correct but Lavelle uses "bent".
by Amanda Mei 1B
Sun Nov 24, 2019 8:16 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: paramagnetism
Replies: 6
Views: 52

Re: paramagnetism

Paramagnetic compounds have at least one unpaired (paramagnetic) electron while diamagnetic compounds have all paired electrons. Paramagnetic compounds are attracted to magnetic fields, while diamagnetic compounds are repelled.
by Amanda Mei 1B
Sun Nov 24, 2019 8:00 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Bond order
Replies: 5
Views: 41

Re: Bond order

Bond order is the number of chemical bonds between atoms. To find bond order, count the number of bonds in a molecule and divide that by the number of bonding regions. For example, NO3- has 4 bonds, comprised of two single bonds and one double bond. You would divide 4 bonds by 3 bonding regions/bond...
by Amanda Mei 1B
Sun Nov 24, 2019 7:46 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: dipole-dipole vs induced dipole
Replies: 9
Views: 59

Re: dipole-dipole vs induced dipole

Why is the molecule OCS is considered polar,shouldn't their dipoles cancel out making the molecule non-polar? Oxygen is more electronegative than sulfur, which means the C-S bond will have a stronger partial negative charge on the sulfur and the C-O bond will have a weaker partial negative charge o...
by Amanda Mei 1B
Sun Nov 24, 2019 7:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Non-polar atoms with lone pairs
Replies: 4
Views: 21

Re: Non-polar atoms with lone pairs

I have a follow-up question: How can we tell that dipole moment vectors cancel when they are at angles to one another (e.g. in a molecule with trigonal planar geometry)? Do we have to break up the vectors into their individual components? If all the bonds are between the same 2 atoms, they cancel o...
by Amanda Mei 1B
Sun Nov 24, 2019 3:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent Shape
Replies: 29
Views: 186

Re: Bent Shape

If a molecular had 2 bonding groups and 1 lone pair, or 2 bonding groups and 2 lone pairs, the molecular shape would be bent.
by Amanda Mei 1B
Sun Nov 17, 2019 6:13 pm
Forum: Dipole Moments
Topic: SCl4 Molecule
Replies: 5
Views: 26

Re: SCl4 Molecule

When there's a lone pair, it makes the molecular polar because the molecule isn't symmetrical and electrons won't be uniformly distributed.
by Amanda Mei 1B
Sun Nov 17, 2019 6:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Order
Replies: 3
Views: 28

Re: Bond Order

You don't need to know bond order in order to find bond angle or bond length. But to find each one, it'd be helpful to draw the Lewis structure.
by Amanda Mei 1B
Sun Nov 17, 2019 5:53 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: bond order calculations
Replies: 4
Views: 38

Re: bond order calculations

To find bond order, count the number of bonds in a molecule and divide that by the number of bonding regions. For example, NO 3 - has 4 bonds, comprised of two single bonds and one double bond. You would divide 4 bonds by 3 bonding regions/bond groups to get a bond order of 1.33. For H 2 , you'd div...
by Amanda Mei 1B
Sun Nov 17, 2019 5:30 pm
Forum: Sigma & Pi Bonds
Topic: Sigma V Pi
Replies: 5
Views: 34

Re: Sigma V Pi

Sigma bonds form between two atoms along the x-axis, and pi bonds form from p-orbital overlap and connect atoms along the y-axis. Sigma bonds are single bonds, pi bonds are the bonds that form after that.
by Amanda Mei 1B
Sun Nov 17, 2019 3:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR shape question
Replies: 2
Views: 15

Re: VSEPR shape question

Linear, and the bond angle would be 180 degrees.
by Amanda Mei 1B
Sun Nov 17, 2019 3:25 pm
Forum: Bond Lengths & Energies
Topic: Quiz for Next week dashes/wedges
Replies: 11
Views: 89

Re: Quiz for Next week dashes/wedges

In class he mentioned that we can just draw a normal Lewis Structure as long as we name the shape I think. Do we have to worry about where we arrange the atoms around the central atom (example: drawing a tetrahedral shape vs square planar) or can we just draw it normally and name the shape after? L...
by Amanda Mei 1B
Sun Nov 10, 2019 3:50 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: How to Draw Dipole Arrows
Replies: 8
Views: 47

Re: How to Draw Dipole Arrows

After drawing a Lewis structure, you'd draw a dipole arrow pointing towards the atom with higher electronegativity. This is because this atom attract electrons and gains a partial positive charge. The other atom involved in the bond, the one with the lower electronegativity, would have a partial pos...
by Amanda Mei 1B
Sat Nov 09, 2019 11:33 pm
Forum: Electronegativity
Topic: Periodic Trend
Replies: 13
Views: 75

Re: Periodic Trend

Electronegativity refers to how strongly an atom attracts bonding electrons to itself. Higher electronegativity means an atom is more likely to attract electrons. EN increases from left to right because more protons means there is a stronger attracted between the positively charged nucleus and negat...
by Amanda Mei 1B
Sat Nov 09, 2019 11:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Formal Charge
Replies: 9
Views: 480

Re: Formal Charge

The most stable Lewis structure for an ion is the one that minimizes formal charges (minimize having separate charges). Also, the negative formal charge should be on the most electronegative atom.
by Amanda Mei 1B
Sat Nov 09, 2019 2:51 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: Intermolecular forces
Replies: 3
Views: 24

Re: Intermolecular forces

Yes, hydrogen-bonding is the strongest intermolecular force. It's between the hydrogen atom of one molecule and an atom of another molecule with high electronegativity.
by Amanda Mei 1B
Sat Nov 09, 2019 2:47 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: Hydrogen bonding
Replies: 8
Views: 38

Re: Hydrogen bonding

N, O, and F are the most electronegative elements (upper righthand corner of the periodic table). Hydrogen will only form hydrogen bonds with them because the electronegative atoms attract the electron cloud around hydrogen and leave hydrogen with a positive charge.
by Amanda Mei 1B
Sat Nov 09, 2019 2:02 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polar Covalent VS Ionic
Replies: 11
Views: 59

Re: Polar Covalent VS Ionic

If you're given an electronegativity table, you can take the absolute value of the difference between the electronegativity values of each atom in the bond. A difference of >1.7 means the bond is ionic, 0.4-1.7 means the bond is polar covalent, and <0.4 means the bond is nonpolar covalent.
by Amanda Mei 1B
Sun Oct 27, 2019 6:24 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: p-orbitals
Replies: 11
Views: 41

Re: p-orbitals

You don't need to write Px, Py, or Pz.
by Amanda Mei 1B
Sun Oct 27, 2019 6:23 pm
Forum: Ionic & Covalent Bonds
Topic: Writing Electron Configurations for an Ion
Replies: 6
Views: 36

Re: Writing Electron Configurations for an Ion

Yes, that's all that changes!
by Amanda Mei 1B
Sun Oct 27, 2019 6:22 pm
Forum: General Science Questions
Topic: Extra Credit
Replies: 19
Views: 128

Re: Extra Credit

I don't think so.
by Amanda Mei 1B
Sun Oct 27, 2019 6:21 pm
Forum: Administrative Questions and Class Announcements
Topic: Thanksgiving
Replies: 3
Views: 42

Re: Thanksgiving

I think we will.
by Amanda Mei 1B
Sun Oct 27, 2019 6:20 pm
Forum: Properties of Electrons
Topic: Electron removal
Replies: 11
Views: 82

Re: Electron removal

The positively charged nucleus is further from these negatively charged electrons, so its pull is not as strong.
by Amanda Mei 1B
Sun Oct 27, 2019 6:03 pm
Forum: Resonance Structures
Topic: Determining Resonance Structures
Replies: 6
Views: 50

Re: Determining Resonance Structures

There is no ideal resonance structure. The sulfate ion could be drawn with the double bond between the central S atom and any of the various O atoms. The formal charge doesn't change because you're not changing the elements that have that specific bond. The double bond is still between S and O.
by Amanda Mei 1B
Sun Oct 27, 2019 5:55 pm
Forum: Trends in The Periodic Table
Topic: Central Atom
Replies: 13
Views: 59

Re: Central Atom

It's usually the atom that creates the most bonds (has fewest valence electrons).
by Amanda Mei 1B
Sun Oct 20, 2019 5:05 pm
Forum: Quantum Numbers and The H-Atom
Topic: Difference in Quantum Numbers?
Replies: 2
Views: 19

Re: Difference in Quantum Numbers?

The principle quantum number (n) determines energy level and size of an orbital an electron is in (shell) The angular momentum number (l) describes the shape of the orbital, and it refers to the number of subshells The magnetic quantum number (m l ) labels the different energy levels/orbitals of a s...
by Amanda Mei 1B
Sun Oct 20, 2019 4:59 pm
Forum: Properties of Electrons
Topic: Hund's Rule
Replies: 5
Views: 45

Re: Hund's Rule

Hund's Rule says that every orbital in a sublevel must be occupied by one electron before any orbital is occupied by two electrons, and all of these lone electrons have the same spin.
by Amanda Mei 1B
Sat Oct 19, 2019 12:29 pm
Forum: SI Units, Unit Conversions
Topic: How to express answers
Replies: 13
Views: 180

Re: How to express answers

I don't believe that sig figs are too important in this class. My TA told us that sig figs are not too big of a deal, as long as you do not round to whole numbers or to only 1 decimal place when the answer should clearly have 2 or 3 decimal places. As for scientific notation, I believe that it is m...
by Amanda Mei 1B
Sat Oct 19, 2019 12:21 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: building up principle
Replies: 5
Views: 31

Re: building up principle

Dr. Lavelle mentioned two exceptions in class to the Aufbau principle: Chromium and Copper. Could someone please explain what those exceptions are and why they are there? These exceptions are that these elements do not follow the normal filling order for typical electron configurations. This occurs...
by Amanda Mei 1B
Sat Oct 19, 2019 12:12 pm
Forum: *Shrodinger Equation
Topic: Electron Distribution Definition
Replies: 4
Views: 61

Re: Electron Distribution Definition

It means density, so electron density is the probability of finding an electron in that location. In an area with higher electron density, you're more likely to find an electron there.
by Amanda Mei 1B
Sun Oct 13, 2019 5:09 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Best Way To Study?
Replies: 56
Views: 384

Re: Best Way To Study?

I read the textbook for sections we cover in class as a way to supplement lectures and clear up anything I don't completely understand during lecture. Aside from watching his audio-visual focus modules, Khan Academy can be a great resource.
by Amanda Mei 1B
Sun Oct 13, 2019 5:06 pm
Forum: DeBroglie Equation
Topic: P
Replies: 3
Views: 58

Re: P

Since p, momentum, is the mass of an object times its velocity, the unit for mass (kg) times the unit for velocity (m/s) will yield (kg)(m)/(s)
by Amanda Mei 1B
Sun Oct 13, 2019 4:58 pm
Forum: Properties of Light
Topic: speed of light
Replies: 10
Views: 51

Re: speed of light

The speed of light in a vaccuum is 3.00x10^8 m/s. It is slower in mediums like air, water, and glass. I think that for this class we'll just use this value.
by Amanda Mei 1B
Sun Oct 13, 2019 4:54 pm
Forum: Properties of Electrons
Topic: electron energy
Replies: 4
Views: 41

Re: electron energy

Ionization energy is the energy needed to remove an electron from a gaseous atom or ion. This value varies based on which electron you are removing, and from which atom. For example, ionization energy will be higher to remove an electron from an atom with a full valence shell. Ionization energy incr...
by Amanda Mei 1B
Sun Oct 13, 2019 3:52 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Advice
Replies: 6
Views: 64

Re: Advice

On the syllabus, Lavelle lists which sections we should read and which problems would be good ones to do for practice.
by Amanda Mei 1B
Sat Oct 05, 2019 5:42 pm
Forum: Limiting Reactant Calculations
Topic: Determining Limiting Reactant by Mole or Mass
Replies: 8
Views: 85

Re: Determining Limiting Reactant by Mole or Mass

I learned to convert moles of reactants to mass of a product and compare which reactants created less/more product. Both ways work. Using Lavelle's way of comparing calculated moles to required moles saves you a step, but I found that problems often asked for how much product would be created, so I ...
by Amanda Mei 1B
Sat Oct 05, 2019 5:34 pm
Forum: Significant Figures
Topic: Sig Figs in % Yield
Replies: 10
Views: 153

Re: Sig Figs in % Yield

Shanzey wrote:If we were to do sig figs for a percent yield question, would we use the significant figures of the grams given for the actual yield?


Yes, you would.
by Amanda Mei 1B
Sat Oct 05, 2019 5:26 pm
Forum: SI Units, Unit Conversions
Topic: Sig figs
Replies: 5
Views: 42

Re: Sig figs

30 is just one sig fig, 30. would be two, and 30.0 would be three. A decimal indicates the tailing zeroes to be significant (e.g. 30. or 30.0). You can also use scientific notation to make sure sig figs are correct. You should check out Lavelle's "Everything you want to know about Sig Fig"...
by Amanda Mei 1B
Sat Oct 05, 2019 5:02 pm
Forum: Balancing Chemical Reactions
Topic: balancing charges
Replies: 4
Views: 60

Re: balancing charges

We need to balance charges when working with redox/oxidation-reduction reactions, which occur when one reactant is oxidized and one is reduced. We will need to split the reaction into two half-reactions and balance them by adjusting coefficients and adding H2O, H+, and electrons (in that order). Whe...
by Amanda Mei 1B
Sat Oct 05, 2019 4:36 pm
Forum: Significant Figures
Topic: Clarification with sig figs
Replies: 6
Views: 64

Re: Clarification with sig figs

Don't round throughout the problem; use exact measurements. Just do sigfigs at the end.
by Amanda Mei 1B
Sat Oct 05, 2019 4:33 pm
Forum: Properties of Light
Topic: Quantum Mechanics
Replies: 9
Views: 77

Re: Quanta and Photons

Can someone please clarify what are quanta? Chem_Mod's answer from an older post: "Quanta are described as discrete packets of energy because it requires a certain amount of energy (not just any amount of energy that is continuous) to excite electrons from one state to another (say in a H atom...
by Amanda Mei 1B
Wed Oct 02, 2019 4:50 pm
Forum: Administrative Questions and Class Announcements
Topic: homework
Replies: 5
Views: 79

Re: homework

Just this week our homework is due in lecture. We usually turn homework in to our TA's during discussion.

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