Search found 63 matches

by Gillian Gabrielsen2F
Fri Jan 22, 2021 6:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy units
Replies: 3
Views: 15

Re: Enthalpy units

ΔHf is kJ/mol because it's the enthalpy required to form a mole of a particular substance. ΔHrxn is just the enthalpy of the overall reaction. Enthalpy is just a measure of the energy released/absorbed as heat while at a constant pressure, hence why kJ is used.
by Gillian Gabrielsen2F
Sun Jan 17, 2021 4:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reaction shift
Replies: 5
Views: 10

Re: Reaction shift

If only the amount of reactants is given, then the foreword reaction is favored. If amounts of both reactants and products are given, you would have to find the value of Q. For Q<K, there's an excess of reactants so the foreword reaction is favored: products are formed (+x) and reactants are used up...
by Gillian Gabrielsen2F
Thu Jan 14, 2021 5:25 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Gas
Replies: 16
Views: 69

Re: Gas

In one of the lecture, Lavelle said that for purposes of this class we can use atm and bar interchangeably. So even though they technically aren't equal, for this course we can assume 1atm=1bar
by Gillian Gabrielsen2F
Thu Jan 14, 2021 5:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solving for equilibrium concentration using Quadratic Equation
Replies: 5
Views: 22

Re: Solving for equilibrium concentration using Quadratic Equation

X should be less than the initial concentrations. If x is greater than an initial concentration, you would have a negative conc at equilibrium (which of course doesn't happen). The smaller of the two positive values should be correct.
by Gillian Gabrielsen2F
Thu Jan 14, 2021 5:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE table initial conc
Replies: 3
Views: 25

Re: ICE table initial conc

It all depends on what substances are in the "starting" solution for whether there's any products or not. If the problem says there is an initial concentration of products, put it in the ICE table. When the concentration of products is given, you'll also have to find the Q value and see wh...
by Gillian Gabrielsen2F
Tue Jan 12, 2021 5:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Homework 2, Question 9
Replies: 2
Views: 58

Re: Sapling Homework 2, Question 9

I view it as when pH<pKa means that the environment has a stronger acid than HA. This means when HA dissociates into A-, the stronger acid protonates A- ions, leading to there being more HA in the solution. Since HA isn't a stronger acid than the environment, it's unable to further lower the pH.
by Gillian Gabrielsen2F
Sat Jan 09, 2021 2:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #5
Replies: 11
Views: 85

Re: Sapling #5

For a reaction A -> B with the equilibrium constant K, The eq. constant of the reverse reaction, B -> A would be 1/K If you multiply the reaction by a number, N(A -> B) the eq. constant would be K^N If you have a composite rxn that can be shown as adding two reactions together, A -> B, k1 B -> C , k...
by Gillian Gabrielsen2F
Thu Jan 07, 2021 7:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Temperature and Kc
Replies: 4
Views: 27

Re: Temperature and Kc

Remember Kc= [products]/[reactants] and the temperature isn't included in it; the temperature just influences the concentration of the products and reactants. How temperature effects K depends on if the reaction is endothermic or exothermic. An Endothermic reaction absorbs heat, so it can be represe...
by Gillian Gabrielsen2F
Wed Jan 06, 2021 6:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: What is an activity?
Replies: 9
Views: 67

Re: What is an activity?

From my understanding, activity is a way to compensate the differences between ideal vs. real behavior in molecules. Real reactions don't occur as idealized due to the additional molecular interactions that occur outside of the specific reaction, so the real pressure/concentration doesn't match exac...
by Gillian Gabrielsen2F
Wed Jan 06, 2021 5:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Box
Replies: 4
Views: 48

Re: ICE Box

It depends on which way the reaction has to go in order to reach equilibrium. If the foreword reaction is favored (excess of reactants, Q<K), the reactants will have a negative change(-x) and the products will have a positive change(+x). If the reverse reaction is favored (excess of products, Q>K), ...
by Gillian Gabrielsen2F
Wed Jan 06, 2021 5:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gas Constant (R)
Replies: 12
Views: 66

Re: Gas Constant (R)

Refer to the equation sheet on Lavelle's website and use whichever R that uses the same measure of pressure as the ones given in the question. This way, all the units cancel out.
by Gillian Gabrielsen2F
Sat Dec 12, 2020 6:27 pm
Forum: Hybridization
Topic: Textbook problem 2F1
Replies: 3
Views: 35

Re: Textbook problem 2F1

This refers to the electron geometry that corresponds with the hybridization. And you should probably know this for the final.
sp3d2- octahedral
sp3d- trigonal bipyramidal
sp3- tetrahedral
sp2- trigonal planar
sp-linear
by Gillian Gabrielsen2F
Sat Dec 12, 2020 11:23 am
Forum: Bronsted Acids & Bases
Topic: Determining strong or weak from reaction
Replies: 7
Views: 71

Re: Determining strong or weak from reaction

You can determine the relative strength based on the Ka/Kb value, but I don't think you get much information from the reaction itself. If anything, when there's a double arrow indicating a reaction that goes both directions, that means the acid/base is weak. Also, it's helpful to memorize all the st...
by Gillian Gabrielsen2F
Fri Dec 11, 2020 7:24 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: polydentates
Replies: 3
Views: 35

Re: polydentates

It'd be helpful to remember the most common polydentates (so common they have nicknames): (en)=bidentate, (dien)=tridentate, (ox)=bidentate, and (edta)=hexadentate.
by Gillian Gabrielsen2F
Fri Dec 11, 2020 9:38 am
Forum: Determining Molecular Shape (VSEPR)
Topic: same plane example
Replies: 3
Views: 38

Re: same plane example

It's because of the pi bonds, which since they exist above and below the bonding axis and prevent the molecules from rotating. https://qph.fs.quoracdn.net/main-qimg-3148d3a88e9d48b8bfb75c9716eb61fe.webp I think this image shows it well. The pi bonds have to alternate which way they're oriented to mi...
by Gillian Gabrielsen2F
Fri Dec 11, 2020 9:30 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Delocalized
Replies: 6
Views: 56

Re: Delocalized

I am still a little confused as to what causes delocalization in an atom or molecule? What could change an unstable molecule with uneven electron distribution into a stable one? Delocalization occurs with differences in electronegativity and resonance. When an atom is highly electronegative, it pul...
by Gillian Gabrielsen2F
Tue Dec 08, 2020 6:12 pm
Forum: Dipole Moments
Topic: induced dipole
Replies: 4
Views: 31

Re: induced dipole

Induced dipole occurs in molecules that aren't dipoles (as in they don't have polar bonds) having a temporary dipole moment due to changing electron clouds. It's only a temporary uneven distribution of electron density. For dipoles, there's a permanent uneven distribution of electron density due to ...
by Gillian Gabrielsen2F
Sat Dec 05, 2020 6:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: difference
Replies: 4
Views: 33

Re: difference

https://upload.wikimedia.org/wikipedia/commons/thumb/3/31/Trigonal-3D-balls.png/330px-Trigonal-3D-balls.png Trigonal Planar has uniform bond angles of 120°. It has three regions of electron density: three bound atoms and no lone pairs. https://upload.wikimedia.org/wikipedia/commons/thumb/b/b9/T-sha...
by Gillian Gabrielsen2F
Sat Dec 05, 2020 6:16 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxalate ion
Replies: 5
Views: 38

Re: Oxalate ion

Because of it's geometry, only two oxygens can bound at a time. Each carbon has a trigonal planar geometry, which means the bond angles are ~ 120 degrees, so all 4 oxygens are unable to bond with the same central metal atom. Here's a picture, where you can see that the non bound oxygens are on the o...
by Gillian Gabrielsen2F
Fri Dec 04, 2020 2:27 pm
Forum: Lewis Acids & Bases
Topic: Difference between a Lewis Base/Acid and Bases and Acids
Replies: 2
Views: 26

Re: Difference between a Lewis Base/Acid and Bases and Acids

The main distinction is that what's a Lewis Acid isn't always a Bronsted acid, and same with bases. Any species with an electron pair it can donate can act as a Lewis base, a proton doesn't have to be involved. A Lewis acid is a species that receives electrons, a proton also doesn't have to be invol...
by Gillian Gabrielsen2F
Thu Dec 03, 2020 6:56 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: ligand vs polyatomic
Replies: 3
Views: 30

Re: ligand vs polyatomic

The difference is a ligand bonds with a central metal ion to form a coordinate complex, while a polyatomic ion is an ionic compound made of multiple atoms. CN- is a polyatomic ion, and due to it's lone pair of electrons on the N and C, it's able to act as a ligand and form a coordinate covalent bond...
by Gillian Gabrielsen2F
Tue Dec 01, 2020 4:41 pm
Forum: Naming
Topic: Naming Coordination Compounds
Replies: 4
Views: 45

Re: Naming Coordination Compounds

I believe we'll only have access to the period table and the formula sheet during the final, so it's better to be familiar with the coordination complex names in case a question about naming pops up on the test. Also, Lavelle also has a pdf on his website of naming compounds which shows the traditio...
by Gillian Gabrielsen2F
Sun Nov 29, 2020 3:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polar vs non-polar
Replies: 7
Views: 52

Re: polar vs non-polar

The electronegativity of the two atoms doesn't necessary have to be the same. The bond can also be considered nonpolar if the values are extremely close to each other. An example is a bond C-H bond. Carbon and Hydrogen have different electronegativities, but the difference is so slight the bond is e...
by Gillian Gabrielsen2F
Fri Nov 27, 2020 8:16 pm
Forum: Hybridization
Topic: Delocalized Pi Bonds
Replies: 3
Views: 42

Re: Delocalized Pi Bonds

A delocalized pi bond would occur in a molecule with resonance structures, where the pi bond in shared amongst the molecules. An example of this is benzene, where the Carbons the same 3 pi bonds the C-C bonds are somewhere between single and double bonds. A regular, localized pi bond is confined wit...
by Gillian Gabrielsen2F
Wed Nov 25, 2020 4:55 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Transition Metal Binding Properties
Replies: 2
Views: 19

Re: Transition Metal Binding Properties

I believe they all can have up to 6 bonds since they can have up to 12 valence electrons (10 in 3d, 2 in 4s)
by Gillian Gabrielsen2F
Wed Nov 25, 2020 1:53 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Identifying Octahedron
Replies: 1
Views: 21

Re: Identifying Octahedron

It's the same as the the electron arrangement and VSEPR shape. When there's 4 regions of electron density it's a tetrahedral electron arrangement. When there's four ligands, it's likely a tetrahedral (there's also the possibility of square planar, which is an octahedral but with lone pairs in the ax...
by Gillian Gabrielsen2F
Wed Nov 25, 2020 11:00 am
Forum: Dipole Moments
Topic: higher dipole moment sapling #10
Replies: 5
Views: 59

Re: higher dipole moment sapling #10

The answer is COFH because in COF2, the dipole moment of O almost cancels out the one of the fluorine's. First of all, we know each of these molecules are trigonal planar, with bond angles ~120 degrees. It's easiest to think of dipole moments as vectors. In a bond between two atoms, the vector will ...
by Gillian Gabrielsen2F
Fri Nov 20, 2020 5:38 pm
Forum: Lewis Structures
Topic: Central Atom Question
Replies: 20
Views: 135

Re: Central Atom Question

H will never be the central atom because Hydrogen can only form one bond (it only has one unpaired electron)
by Gillian Gabrielsen2F
Thu Nov 19, 2020 7:05 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 9
Views: 98

Re: Electron Affinity

I know this was answered, but I personally find visualizing arrows like this on the periodic table helpful. Just remember the noble gases have a full valence shell already, so they're nonreactive and don't need to gain electrons https://chem.libretexts.org/@api/deki/files/1189/Electron_Affinity_Tren...
by Gillian Gabrielsen2F
Wed Nov 18, 2020 1:52 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing Power/Polarizability Trend?
Replies: 4
Views: 44

Re: Polarizing Power/Polarizability Trend?

Yes, an anion is more polarizable if it has a larger atomic radius. A cation has higher polarizing power as their atomic radius gets smaller and as their charge increases.
Image
by Gillian Gabrielsen2F
Wed Nov 18, 2020 1:43 pm
Forum: Dipole Moments
Topic: Dipole Moments Always Exist?
Replies: 3
Views: 40

Re: Dipole Moments Always Exist?

It's also possible for two polar bonds to cancel each other out, based on the molecular geometry, so that the molecule as a whole doesn't have a permanent dipole moment. For example in CO2, even though C=O is a polar bond, because the molecule is linear the bonds pull in opposite directions and they...
by Gillian Gabrielsen2F
Tue Nov 17, 2020 4:49 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: d vs s orbitals
Replies: 7
Views: 97

Re: d vs s orbitals

For s block elements, like K and Ca, 4s fills up first. To my understanding this is because 4s and 3d are close in energy level and 3d is more compact, so the electrons are held closer together which causes more repulsion, so filling up 4s first is more efficient energy wise. However, for transition...
by Gillian Gabrielsen2F
Fri Nov 13, 2020 5:58 pm
Forum: Electronegativity
Topic: C and H electronegativity
Replies: 7
Views: 65

Re: C and H electronegativity

Their electronegativity levels aren't the same, but the difference between them isn't large enough for the bond to be considered polar.
by Gillian Gabrielsen2F
Fri Nov 13, 2020 8:53 am
Forum: Coordinate Covalent Bonds
Topic: Hydrogen bonding
Replies: 15
Views: 112

Re: Hydrogen bonding

Hydrogen bonding is a form of intermolecular forces, so it's the attraction between molecules. More specifically, it's a special type of dipole-dipole interaction. Coordinate Covalent bonds forms new molecules by sharing electrons, where only one atom provides the electrons being shared. Even though...
by Gillian Gabrielsen2F
Thu Nov 12, 2020 10:03 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Covalent Character
Replies: 3
Views: 29

Re: Covalent Character

An ionic bond having covalent character means there's a slight region where the electrons appear to be "shared", where the electron density tends to be in a region between the anion and cation. Remember that electrons don't orbit the nucleus like planets around around the sun, they move so...
by Gillian Gabrielsen2F
Thu Nov 12, 2020 8:52 am
Forum: Ionic & Covalent Bonds
Topic: Hydrogen Bond & Density
Replies: 1
Views: 29

Re: Hydrogen Bond & Density

The water molecules in ice would be further apart, since they're less dense. Density = mass/volume, so the same numbers of water molecules take up slightly more space as ice than liquid. The hydrogen bonds lead to the water molecules in ice being pushed further apart in a more uniform structure. As ...
by Gillian Gabrielsen2F
Wed Nov 11, 2020 9:25 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Can an Anion be Polarizing
Replies: 4
Views: 61

Re: Can an Anion be Polarizing

I don't think so. A cation's positive charge is what causes it to be polarizing. Since a cation has a positive charge, the nucleus has a greater pull on the cation's electrons and they're held more tightly within the electron cloud. An anion has a negative charge, which means it has an excess of ele...
by Gillian Gabrielsen2F
Sun Nov 08, 2020 9:20 am
Forum: Lewis Structures
Topic: Which atom to add positive/negative charge?
Replies: 6
Views: 50

Re: Which atom to add positive/negative charge?

I believe that you also can determine the charge of an atom based on what column it resides in the periodic table. F is negative because it has seven valence electrons, meaning that it only wants to gain one to reach the octet. This makes is F-. Calcium has two valence electrons, so it wants to los...
by Gillian Gabrielsen2F
Fri Nov 06, 2020 5:13 pm
Forum: Octet Exceptions
Topic: Phosphorus and d-Orbital
Replies: 7
Views: 66

Re: Phosphorus and d-Orbital

s, p, d, and f are all subshells of the energy level, n. So 3s, 3p, and 3d all have n=3 and all make up that energy level. Phosphorus' electrons fill up to 3p, so it is able to fill into 3d to accommodate the extra electrons since n=3 for 3d and 3p, meaning they're part of the same energy level. 4s ...
by Gillian Gabrielsen2F
Fri Nov 06, 2020 9:07 am
Forum: Quantum Numbers and The H-Atom
Topic: 4th quantum number
Replies: 8
Views: 45

Re: 4th quantum number

Ms represents the spin of the electron, with +1/2 for up and -1/2 for down. You can tell if an electron is + or - based on what direction the arrow is pointing (up is positive, down is negative). When filling up orbitals, you have to follow Hund's rule and the Pauli Exclusion Principle. That just me...
by Gillian Gabrielsen2F
Fri Nov 06, 2020 8:45 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbital vs Subshell
Replies: 7
Views: 76

Re: Orbital vs Subshell

A way to remember is that a shell/energy level (n) can be broken down into subshells (s,p,d,f), which can then be further broken down into orbitals (ml). Each orbital can hold two electrons, one spinning up and one spinning down(ms)
by Gillian Gabrielsen2F
Fri Nov 06, 2020 8:20 am
Forum: Ionic & Covalent Bonds
Topic: Drawing Lewis structures (sapling)
Replies: 3
Views: 53

Re: Drawing Lewis structures (sapling)

Yes it matters. Those charges are used to represent the formal charge of the atom, so you can only apply a specific charge to each atom. When you add up all the formal charges, you should reach the overall charge of the molecule.
by Gillian Gabrielsen2F
Sun Nov 01, 2020 10:16 am
Forum: Einstein Equation
Topic: de Broglie and neutrons
Replies: 8
Views: 64

Re: de Broglie and neutrons

The de Broglie equation can be used with anything that has mass. So it can be used on neutrons, electrons, protons, and macroscopic objects like baseballs, but it can't be used on photons since light doesn't have mass. For light you'll need to use other equations.
by Gillian Gabrielsen2F
Wed Oct 28, 2020 6:12 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Sapling Question
Replies: 4
Views: 75

Re: Sapling Question

n is is energy level, or the shell. s,p,d and f are all subshells that make up the particular shell. For a particular element, n is based on the period(row) of the periodic table, and it's the number in front of s,p,d,f. for s and p block, n = # row. For d block, n = # row - 1. For f block n= # row ...
by Gillian Gabrielsen2F
Wed Oct 28, 2020 5:35 pm
Forum: DeBroglie Equation
Topic: p
Replies: 19
Views: 160

Re: p

p=(mass)(velocity), as others have said. Because of mass, you can only use the deBroglie Equation for things that have mass. Therefore, it can't be used for photons since light doesn't have mass, but you can use it for other subatomic particles. So you will use deBroglie if a problem is asking for t...
by Gillian Gabrielsen2F
Wed Oct 28, 2020 5:28 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra wave-like or particle-like properties
Replies: 3
Views: 54

Re: Atomic Spectra wave-like or particle-like properties

Light behaves like particles, as each electron emits/absorbs an individual photon as it changes energy levels.
by Gillian Gabrielsen2F
Tue Oct 27, 2020 10:37 am
Forum: DeBroglie Equation
Topic: #22 Sapling conversion
Replies: 4
Views: 65

Re: #22 Sapling conversion

For this problem, you can first use the de Broglie equation to get the velocity \lambda =\frac{h}{mv} . After you get v, you should be able to find the KE using KE=\frac{1}{2}mv^{2} . Make sure you convert the mass of the electron to kilograms, since Joules are kg*m^2*s^-2, and nanometers to meters....
by Gillian Gabrielsen2F
Tue Oct 27, 2020 10:22 am
Forum: Properties of Light
Topic: Tips for knowing what equation to use?
Replies: 5
Views: 74

Re: Tips for knowing what equation to use?

I normally write out the values that are given and what the problem is asking for then base the equation on those values. Keep your eye out for if the problem mentions mass, velocity, or momentum, because that means you'll likely have to use de Broglie's.
by Gillian Gabrielsen2F
Fri Oct 23, 2020 3:05 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Frequency Equation Question
Replies: 5
Views: 60

Re: Rydberg Frequency Equation Question

I know for the Balmer series, n1=2 while for the Lyman series n1=1. So if the problem says "violet light is emitted" or another color, n1=2. Just remembering that made these problems less confusing for me. This picture helped me a lot. https://haygot.s3.amazonaws.com/questions/625565_59644...
by Gillian Gabrielsen2F
Fri Oct 23, 2020 2:40 pm
Forum: SI Units, Unit Conversions
Topic: Given Unit Conversions?
Replies: 6
Views: 42

Re: Given Unit Conversions?

The sheet we're allowed to have, which someone linked above, has a few unit conversions on it. Those are probably the only ones we'll need to know for the test. And I doubt we'll receive questions in imperial, since metric is the primary system for science (and the world)
by Gillian Gabrielsen2F
Fri Oct 23, 2020 1:40 pm
Forum: Einstein Equation
Topic: m vs nm
Replies: 66
Views: 445

Re: m vs nm

The midterm is multiple choice and they aren't collecting scratch work, so is doesn't matter if it's in m or nm, as long as it's correct.
by Gillian Gabrielsen2F
Fri Oct 23, 2020 1:37 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Indeterminacy for Electrons in Bohr's Model of Atoms?
Replies: 3
Views: 78

Re: Indeterminacy for Electrons in Bohr's Model of Atoms?

In the Audio-Visual Focus topic, Lavelle applied the indeterminacy equation to the Bohr model. He used the radius of the first shell of a hydrogen atom (which is 10^-10 m, or one angstrom), and the indeterminacy of velocity ended up being 2.3*10^5 m/s, which is a plausible value since it's less than...
by Gillian Gabrielsen2F
Tue Oct 20, 2020 4:03 pm
Forum: Significant Figures
Topic: How would you round these numbers
Replies: 10
Views: 118

How would you round these numbers

How do you round numbers such as 7.956 and 4.9773 to two sigfigs? I normally round to 8.0 or 5.0 but that seems incorrect
by Gillian Gabrielsen2F
Sun Oct 18, 2020 9:56 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Test Accuracy
Replies: 13
Views: 155

Re: Test Accuracy

I'd imagine we just need the correct number of sig figs and the correct units. Even if the test is multiple choice like some people have said, it's a good habit to write down the correct units and sig figs while working out problems. I know I got some chem/physics/calc problems incorrect in the past...
by Gillian Gabrielsen2F
Sun Oct 18, 2020 9:51 am
Forum: Significant Figures
Topic: When should I start looking at sig figs?
Replies: 31
Views: 234

Re: When should I start looking at sig figs?

You should only worry about sigfigs once you have your final answer. Rounding the intermediary steps will lead to slight errors in the final answer. So in other words, leave the really long decimals until your final answer, which should be rounded and in scientific notation
by Gillian Gabrielsen2F
Sun Oct 18, 2020 9:48 am
Forum: Properties of Electrons
Topic: Electron Wave-Particle Duality
Replies: 10
Views: 98

Re: Electron Wave-Particle Duality

From my understanding, light (along with all other matter) has wave-particle duality because our limited perception of the quantum realm makes it impossible for us to understand and "see" what is truly going on. We use the descriptions of waves and particles to make the quantum realm under...
by Gillian Gabrielsen2F
Thu Oct 15, 2020 9:15 pm
Forum: Photoelectric Effect
Topic: Definition of "Work"
Replies: 6
Views: 86

Re: Definition of "Work"

Work is the threshold energy, which as said is the amount of energy required to remove an electron from the surface. You'll likely need to use the equation when the two of the values of the equation [ E(photon)-work=KE(electron)] is given. (remember KE(electron)=1/2mv^2). The equation essentially ex...
by Gillian Gabrielsen2F
Thu Oct 15, 2020 9:04 pm
Forum: Properties of Light
Topic: "Intensity"
Replies: 20
Views: 133

Re: "Intensity"

A photon is like a particle of light. Since light is both a wave and a particle, it's the same intensity. When discussing the photoelectric effect, the wave model alone is insufficient as Dr. Lavelle explained. If the amplitude of the light is increased (the light source becomes brighter), there are...
by Gillian Gabrielsen2F
Sun Oct 11, 2020 9:46 am
Forum: Limiting Reactant Calculations
Topic: Determining Limiting Reactant
Replies: 7
Views: 87

Re: Determining Limiting Reactant

As people have said, even if in the balanced equation the reactants have a 1:1 ratio, that doesn't mean they're both limiting reactants. With LR, it matters how many moles are actually present, and then seeing how that ratio compares to the molar ratio within the equation. Just assume for all proble...
by Gillian Gabrielsen2F
Fri Oct 09, 2020 9:15 am
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Reactions Order
Replies: 31
Views: 241

Re: Balancing Chemical Reactions Order

I've heard it's better to start with the largest molecule, but I normally just balance from left to right. As long as you double check your answer at the end, it shouldn't matter.
by Gillian Gabrielsen2F
Fri Oct 09, 2020 9:11 am
Forum: Balancing Chemical Reactions
Topic: Fractions
Replies: 26
Views: 169

Re: Fractions

The stoichiometric coefficient should be the lowest whole number, so multiple all the coefficients by the denominator to get rid of the fraction.
by Gillian Gabrielsen2F
Fri Oct 09, 2020 9:06 am
Forum: Significant Figures
Topic: Inaccurate Answer
Replies: 4
Views: 101

Re: Inaccurate Answer

It's because you're using different values, such as H=1.007 rather than H=1.008 and O=15.9994 instead of O=16. Different periodic tables use values of the molar mass that are rounded differently.
by Gillian Gabrielsen2F
Fri Oct 09, 2020 8:55 am
Forum: Significant Figures
Topic: Rounding Rule
Replies: 8
Views: 77

Re: Rounding Rule

You round to the least number of significant figure, though in multiple step problems only round in the last step. So keep the really long decimals on your calculator until you have the solution of the problem, which you then round to the lowest number of sigfigs.

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