## Search found 95 matches

Mon Jan 25, 2021 2:31 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Constant Pressure vs Constant Volume
Replies: 2
Views: 6

### Re: Constant Pressure vs Constant Volume

This is pretty much right! One thing to account for is that a constant volume system cannot be created without a piston and is usually associated with the presence of a gas inside the calorimeter. And the calorimeter for constant volume can only maintain a constant volume if the piston does not move...
Mon Jan 25, 2021 2:25 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Energy Question
Replies: 1
Views: 11

### Re: Energy Question

In this case it would be the absolute value, since the question already implies that energy has been released. If it asks for an energy change then there would be a negative sign (if the system did lose heat). Hope this helps!
Mon Jan 25, 2021 2:23 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Perfect System
Replies: 2
Views: 9

### Re: Perfect System

We probably can't assume this. Heat transfer is not always efficient so all heat released from a reaction will not be kept in the solution. In other words, there is no way to keep all of the heat within a specific area where we can measure it. Sometimes it is possible, but it is not guaranteed. Hope...
Sat Jan 23, 2021 8:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pressure Units
Replies: 3
Views: 11

### Pressure Units

While reviewing some problems from the textbook, I noticed that some pressure values were given in kPa and torr, while the standard unit when performing calculations with equilibrium expressions is bars/atm. Are we expected to know these conversions for the midterm or for any other purposes?
Fri Jan 22, 2021 4:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State of Elements
Replies: 4
Views: 29

### Re: Standard State of Elements

I am sure we have to memorize these. Some of the common nonmetals and all the halogens are diatomic molecules (H2, O2, N2, F2, Cl2, Br2, I2). All of the metals are just their individual atoms (Al, Li, Na, etc.) and the other nonmetals such as phosphorus or sulfur vary. Hope this helps!
Fri Jan 22, 2021 3:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpy vs. Standard Enthalpy of Formation
Replies: 2
Views: 13

### Re: Standard Reaction Enthalpy vs. Standard Enthalpy of Formation

Standard reaction enthalpy is the enthalpy of a reaction that consists of various molecular species, whereas standard enthalpy of formation refers to the enthalpy of the reaction from which a complex molecule is created from individual elements in their most stable state. Hope that helps!
Fri Jan 22, 2021 3:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sapling Question 4 Week 3
Replies: 2
Views: 22

### Re: Sapling Question 4 Week 3

So enthalpy of combustion is kind of a shorthand notation to indicate the enthalpy of a reaction of which a compound is burned in oxygen. In this case, methane is combusted, so it is calculated in the same way, but describing it as the enthalpy of combustion helps for specificity. Hope this helps!
Fri Jan 22, 2021 3:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating -log
Replies: 7
Views: 34

### Re: Calculating -log

I have a TI-84 Plus and there is a negative button near the "Enter" button. Just be careful not to use the "subtract" button instead of the negative button. The negative sign is usually in parenthesis. Hope this helps!
Fri Jan 22, 2021 3:49 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: reaction enthalpy of O2
Replies: 4
Views: 22

### Re: reaction enthalpy of O2

This is the case for O2 because O2 in nature is its most stable state. Therefore, no input or output of energy creates this stable state because it exists in nature in this way. Usually if a molecule has an enthalpy of formation it will be listed in the table in our textbook. Hope this helps!
Wed Jan 13, 2021 7:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #9
Replies: 3
Views: 35

### Re: Sapling #9

to add, find the value of K by using the equilibrium concentrations in a reaction quotient expression. This way, you can solve for a value of x. Hope this helps!
Wed Jan 13, 2021 5:18 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.5
Replies: 5
Views: 22

### Re: 5J.5

The equation is perfectly balanced. However, the equilibrium symbol and the addition symbol just need to be switched. This should create the correct equation.
Wed Jan 13, 2021 5:15 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Chemical Equilibrium Outline
Replies: 3
Views: 58

### Re: Chemical Equilibrium Outline

I think these refer to the examples that Dr. Lavelle will present in lectures. In Chem 14A he talked about hemoglobin in the context of coordination compounds so he tried to incorporate these ideas into a biological context. When he lists these things I think he is referring to his discussion of the...
Wed Jan 13, 2021 1:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: [H30+]=[OH-] ???
Replies: 8
Views: 45

### Re: [H30+]=[OH-] ???

Yes you have to square root the Kw value. This is because the water equilibrium involved a one-to-one ratio of hydronium to hydroxide ions, so the equilibrium will result in their equilibrium concentrations being the same. Note that they are only the same in distilled water, since there are no other...
Wed Jan 13, 2021 12:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Net Ionic Equations
Replies: 2
Views: 19

### Re: Net Ionic Equations

Usually, net ionic equations are ideal since they remove any extraneous ions or species that may make the reaction quotient more complex. Keep in mind however that some net ionic equations still feature some pure substances in them, so just be aware of exactly which spectators you remove. While soli...
Fri Jan 08, 2021 2:46 pm
Forum: Ideal Gases
Topic: Bohr, Gay-Lussac, etc.
Replies: 3
Views: 30

### Re: Bohr, Gay-Lussac, etc.

I am sure it is just enough to know the Ideal Gas Law, since it is a combination of Gay-Lussac's Law, Boyle's law, etc. Hope this helps!
Wed Jan 06, 2021 12:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #3
Replies: 11
Views: 82

### Re: Sapling #3

the K value of 53.3 should not have a square root attached to it. Removing this square root and solving the resulting quadratic equation should result in the correct answer. Hope this helps!
Wed Jan 06, 2021 12:42 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Part 3 Post Module Assessment #19
Replies: 4
Views: 29

### Re: Part 3 Post Module Assessment #19

To add, the reason why the As is not included in the equilibrium expression is that it is a pure substance, a solid. Solids do not have any measurable concentration because they are not within a liquid, so they are not included in the equilibrium expression as a measurable concentration amount. Hope...
Wed Jan 06, 2021 12:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gas Constant (R)
Replies: 12
Views: 66

### Re: Gas Constant (R)

It depends on the situation and the units that the constant is used in. For the ideal gas equation, it is approximately 0.08206 L*atm/mol*K. Of course, this number can be converted if different units need to be applied.
Wed Jan 06, 2021 12:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Converting bar to mol/L
Replies: 5
Views: 27

### Re: Converting bar to mol/L

For the ideal gas equation, the pressure unit is atmospheres. So solve the ideal gas equation for pressure using the given temperature and concentration, and then convert the pressure value from atmospheres to bars. The conversion is about 0.99 atmospheres to 1 bar, so a direct one-to-one conversion...
Tue Jan 05, 2021 10:14 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Reactant in Excess
Replies: 9
Views: 45

### Re: Reactant in Excess

In the case of equilibrium, no excess reactant would exist. The reaction would shift such that It achieves equilibrium concentrations that follow the equilibrium constant correctly. So any excess reactant at all would not be excess, and would therefore result in a shift towards the formation of the ...
Wed Dec 16, 2020 4:05 pm
Forum: Quantum Numbers and The H-Atom
Topic: Why does nickel have an expanded octet?
Replies: 5
Views: 33

### Re: Why does nickel have an expanded octet?

To add to this, Ni2+ is very common in coordination compounds, of which it uses its expanded octet in some cases to form octahedral structures. Just thought I would introduce a biological application. Hope this helps!
Wed Dec 16, 2020 4:03 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Textbook Question 6C.19 Reasoning for Relative Acid Strengths
Replies: 1
Views: 8

### Re: Textbook Question 6C.19 Reasoning for Relative Acid Strengths

for part c, there is no bond between the H and Br. The bond in both of the molecules that you are comparing is an O-H bond. Since the bond is the exact same, we look at other aspects of the molecule. Cl is more electronegative than Br, so it has higher electron-withdrawing power, therefore the O-H b...
Sat Dec 12, 2020 7:18 pm
Forum: Sigma & Pi Bonds
Topic: CO2 sigma/pi bond composition
Replies: 3
Views: 32

### Re: CO2 sigma/pi bond composition

This is actually incorrect. The sigma bond is (C2sp,O2sp) where the orbitals overlap in each of the atoms. Correct me if I am wrong, but the pi bond is (C2p,O2p), since the orbitals do not overlap and exist adjacent to each other. I am not sure if this answer is true, but hope this helps!
Sat Dec 12, 2020 7:16 pm
Forum: Limiting Reactant Calculations
Topic: Dino Nuggets Question 3
Replies: 3
Views: 70

### Re: Dino Nuggets Question 3

first you should balance the equation, this way you can see the molar ratios of all compounds involved. Then, perform stoichiometric conversions for both the O2 and the NH3 into NO. The theoretical yield will be the smallest amount of NO that is calculated, as this reactant is also the limiting reac...
Mon Dec 07, 2020 10:37 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Identifying Bases
Replies: 7
Views: 43

### Re: Identifying Bases

Usually, bases are compounds that create hydroxide (OH-) in solution. One way that compounds do this is by releasing OH- into the solutions, as explained by the strong bases you listed above. Another way this occurs is if a compound removes a hydrogen ion (H+) from water. One example of this is ammo...
Mon Dec 07, 2020 9:49 am
Forum: Naming
Topic: Naming metals
Replies: 6
Views: 44

### Re: Naming metals

Usually is a coordination compound that is bonded to an ion or has hydrates attached has those aspects at the end of the name, to add.
Mon Dec 07, 2020 9:47 am
Forum: Hybridization
Topic: Hybridization and Shape
Replies: 6
Views: 54

### Re: Hybridization and Shape

Hybridization is directly related to steric number. That is, it directly relates to the number of regions of electron density. From the table shown, both AX2E and AX3 have sp2 hybridization because there are 3 regions of electron density in each. In other words, be careful not to confuse shape with ...
Fri Dec 04, 2020 11:37 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating ligands and polydentate compounds
Replies: 3
Views: 21

### Chelating ligands and polydentate compounds

Considering some polydentate compounds (such as ethylenediamine), will polydentate compounds always form a chelate? or are there instances where these compounds may only form one coordinate covalent bond in a complex? hope this makes sense!
Tue Dec 01, 2020 6:57 pm
Forum: Naming
Topic: Oxidation number of ligands
Replies: 11
Views: 92

### Re: Oxidation number of ligands

to add: there is a chart on sapling that lists common ligands and their names in the context of coordination compounds. It also lists common oxidation states as well
Tue Dec 01, 2020 6:55 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: Overall Review of Intermolecular Forces
Replies: 4
Views: 38

### Re: Overall Review of Intermolecular Forces

Also to add to the above: water's hydrogen bonding allows water molecules to expand when in a crystalline structure (or a solid). this makes the density of this crystalline solid (ice) smaller than water and allows ice to float on water. This allows marine life to prosper well. Just thought I would ...
Tue Dec 01, 2020 6:52 pm
Forum: Naming
Topic: Ferrate vs iron
Replies: 5
Views: 49

### Re: Ferrate vs iron

to add to what was already said, ferrate should be used when the entire coordination compound has an overall negative charge. In general, the "ate" version of metals should be used for any negative charge on the coordination compound. Keep in mind that coordination compounds only have nega...
Tue Dec 01, 2020 12:16 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Transition Metal
Replies: 3
Views: 20

### Re: Transition Metal

In the case of any transition metal, it is difficult to figure out the oxidation state without memorizing it. In most cases, the charge of the TM will be given to us, but we may have to figure it out in other cases. Hope this helps!
Tue Dec 01, 2020 11:48 am
Forum: Naming
Topic: Anions outside Coordination Sphere
Replies: 5
Views: 57

### Re: Anions outside Coordination Sphere

it would just be chloride, assuming the coordination compound has a 3+ charge in this case. Anions usually do not take on the Greek prefixes, whereas ligands do even if they are the same atom/ion/compound. Hope this helps!
Tue Dec 01, 2020 11:47 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: TM good for electron transfer
Replies: 1
Views: 16

### Re: TM good for electron transfer

Transition metals can have more than one stable ionic state. For example, Fe is stable in the 2+ and 3+ state. In other words, if an Fe2+ ion exists, it can "transfer" elsewhere to be used for other biological processes. It can transfer these electrons because once the Fe2+ loses an electr...
Tue Dec 01, 2020 11:41 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number vs. Oxidation Number
Replies: 1
Views: 17

### Re: Coordination Number vs. Oxidation Number

Yes, this would be correct. Take note however that most of the time the ligands may be non-charged, and therefore would not factor into the oxidation number. In this case, the ligands are charged, but I believe in Dr. Lavelle's lecture it was mentioned that it is not common to find charged ligands. ...
Sun Nov 29, 2020 10:44 pm
Forum: Electronegativity
Topic: Be vs Cl
Replies: 13
Views: 108

### Re: Be vs Cl

Another way to compare electronegativities is to compare its placement to fluorine, the most electronegative atom. Since chlorine is closer to fluorine on the periodic table than beryllium, chlorine is more electronegative. Hope this helps!
Fri Nov 27, 2020 9:49 am
Forum: Sigma & Pi Bonds
Topic: Perpendicular Pi Bonds
Replies: 2
Views: 19

### Re: Perpendicular Pi Bonds

Hello, So I believe the orientations are either stacked orbitals or end-to-end orbitals. End-to-end orbitals represent a sigma bond since it consists of the hybridization of two different orbitals (i.e. s and p). Stacked orbitals occur to form a pi bond, since it is usually created by p orbitals. Ho...
Fri Nov 27, 2020 9:44 am
Forum: Properties of Electrons
Topic: Spin States and Ground State
Replies: 2
Views: 58

### Re: Spin States and Ground State

To add to this, ground state atoms would follow Hund's rule, where the electrons begin to pair only when all other orbitals are full. If there are multiple electrons in a single orbital even if the other orbitals are not filled with a single electron, the atom can also be considered excited. I belie...
Fri Nov 27, 2020 9:39 am
Forum: Molarity, Solutions, Dilutions
Topic: Molarity other than solutions
Replies: 6
Views: 55

### Re: Molarity other than solutions

So one thing I would like to add is that when a solid is dissolved in water, it does in fact have molarity. However, outside of water, solids do not ever have a concentration. Gases usually do not have a concentration at all.
Thu Nov 26, 2020 5:40 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 predict energy of bond
Replies: 3
Views: 26

### Re: How to predict energy of bond

Going off what was said above, I believe a rule of thumb when gauging the strength of IMFs is that London dispersion forces are considered the weakest forces out of all the others. I wouldn't necessarily say this. There are some cases in which molecules with only Dispersion Forces form stronger int...
Mon Nov 23, 2020 11:46 am
Forum: Octet Exceptions
Replies: 4
Views: 35

As mentioned in Dr. Lavelle's lecture, the methyl radical also exists when methane is burned. This radical is somewhat stable but does not last long. Each radical varies in terms of stability, but the primary idea to understand about them is that they are extremely reactive. The extra electron neces...
Sun Nov 22, 2020 6:15 pm
Forum: Electronegativity
Replies: 8
Views: 55

### Re: Electronegativity versus atomic radius

As atomic radius decreases electronegativity decreases because there is more repulsion from the additional valence electrons that make it more difficult to add an electron. In other words, the effective nuclear charge decreases for the specific atom as atomic radius decreases, and hence it cannot at...
Sat Nov 21, 2020 11:18 pm
Forum: Ionic & Covalent Bonds
Topic: Rules of ionization energy
Replies: 18
Views: 118

### Re: Rules of ionization energy

another good way to remember is to contrast this with electronegativity. Electronegativity means that an atom has a strong ability to attract electrons, meaning that it would take a lot more energy to remove one if we wished to. In other words, a high electronegativity results in a low ionization en...
Sat Nov 21, 2020 11:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Textbook practice problem 2E.1
Replies: 4
Views: 22

### Re: Textbook practice problem 2E.1

It is still possible to have lone pairs and be linear. If the central atom has 3 lone pairs as well as 2 outer atoms, the 3 lone pairs will occupy the equatorial plane thus leaving the 2 outer atoms both on the axial planes. This would result in a 180 angle and thus a linear shape. Yes this is corr...
Sat Nov 21, 2020 11:12 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 Dipole-Induced Dipole
Replies: 5
Views: 52

### Re: Dipole-Dipole vs Dipole-Induced Dipole

dipole-dipole occurs when two polar molecules come into contact with each other, such that the positive "pole" of one molecule and the negative "pole" of another experience an attractive force. dipole-induced dipole occurs when a polar and nonpolar molecule come into contact with...
Sat Nov 21, 2020 10:45 pm
Forum: Bond Lengths & Energies
Topic: kJ/mol for bond energy in Lecture #18
Replies: 3
Views: 67

### Re: kJ/mol for bond energy in Lecture #18

You all are on the correct track. Just a minor correction to the comment above that would be 10 MOLES of hydrogen bonds, or 10 moles of water molecules broken, to result in 200 kJ of energy. However, I wouldn't focus that greatly on these specifics. The main idea is to understand the comparison betw...
Thu Nov 19, 2020 10:51 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Chromium and copper exceptions
Replies: 2
Views: 25

### Re: Chromium and copper exceptions

Hello!

This does not apply to other elements because they do not have the ability to fill a 3d subshell halfway or completely. It is more stable for electrons to be in the 4s state than the 3d state for these elements. Hope this helps!
Tue Nov 17, 2020 11:56 am
Forum: Ionic & Covalent Bonds
Topic: Covalent molecule - polarizability and en
Replies: 2
Views: 10

### Re: Covalent molecule - polarizability and en

AlCl3 is a molecule because the electronegativity difference is not that large. There is really no way to tell this since we are not given electronegativity values, but this is the simplest answer. Hope this helps!
Tue Nov 17, 2020 11:27 am
Forum: Lewis Structures
Topic: Determining Polar or Non-Polar from Lewis Structure
Replies: 3
Views: 17

### Re: Determining Polar or Non-Polar from Lewis Structure

hello! In some cases, we may be given the electronegativity values and we compare them to see whether or not the bond is polar or non-polar. Otherwise, we may need to just simply compare the polarity of two compounds. For example, we may be asked which between HF and HI is more polar. Since I is les...
Sat Nov 14, 2020 12:45 am
Forum: Ionic & Covalent Bonds
Topic: Cations and Anions
Replies: 3
Views: 36

### Re: Cations and Anions

That is typically the general trend. It is better to compare the natural ions by the column they exist in. Boron and aluminum both have 3+ charges because they are both in group 13, but boron is a metalloid and aluminum a metal, so each element being a metal, metalloid, or nonmetal is not as signifi...
Sat Nov 14, 2020 12:41 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Textbook #3F1
Replies: 4
Views: 47

### Re: Textbook #3F1

So in this case, the difference in electronegativity plays a role, but it is also important to interpret the shape. If SO2 were a LINEAR compound, there would be no dipole forces, since the dipole moments cancel. However, it’s bent shape prevents this, causing a net dipole that creates these dipole-...
Sat Nov 14, 2020 12:39 am
Forum: Electronegativity
Topic: Textbook 2D problem #7
Replies: 3
Views: 24

### Re: Textbook 2D problem #7

Hello! So it all depends on the electro negativity difference between the constituent elements. Both compounds have oxygen, and magnesium has a higher electro negativity than barium. Usually, the higher the electro negativity difference, the greater the IONIC character, and therefore the lesser the ...
Fri Nov 13, 2020 7:53 pm
Forum: Trends in The Periodic Table
Replies: 10
Views: 67

to add to what was already said, I believe we only need to compare elements in the same group or column, and not across different groups and columns entirely. Hope this helps
Fri Nov 13, 2020 6:48 pm
Forum: Resonance Structures
Topic: bond length
Replies: 6
Views: 25

### Re: bond length

Hello!

For this course, it is not required for us to memorize numerical bond lengths. We should only be familiar with the trends in bond lengths. If we ever need numerical values, they will be given to us always. Hope this helps!
Wed Nov 11, 2020 7:03 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: Polarizing power for Cations
Replies: 1
Views: 18

### Re: Polarizing power for Cations

In terms of polarizing power, you want to interpret how "free" the electrons are in moving around a compound. In the case of Li+ and Mg2+, ionic compounds would be formed so polarizing power is not even a disputable topic here. Polarizability can only be attributed to molecular compounds. ...
Sun Nov 08, 2020 2:58 pm
Forum: Lewis Structures
Replies: 2
Views: 26

To add, having only 3 bonded pairs best lowers the formal charge of the Boron atom as well. Lowering formal charge is usually a good way to discover the most stable form.
Sun Nov 08, 2020 2:56 pm
Forum: Bond Lengths & Energies
Topic: Sapling #4 Bond Length
Replies: 2
Views: 30

### Re: Sapling #4 Bond Length

So when Dr. Lavelle introduced resonance structures, he said that the way that the molecules exist in nature are that they are not entirely single or double bonds, but rest in between due to the delocalization of the electrons around the central atom. There is experimental evidence of the single and...
Sun Nov 08, 2020 2:52 pm
Forum: Octet Exceptions
Topic: Stability of Atoms in 3p
Replies: 3
Views: 48

### Re: Stability of Atoms in 3p

Hey! So it is not exactly a specific number that makes it more stable, but it depends on the electron configurations of the atom and the specific compound. For instance, in PCl5, the P atom becomes the most stable when it has 5 bonded pairs since that best lowers the formal charge of the phosphorus ...
Thu Nov 05, 2020 3:58 pm
Forum: *Shrodinger Equation
Topic: Shrodinger Equation Explanation
Replies: 3
Views: 59

### Re: Shrodinger Equation Explanation

to add on to what was already said here, I wanted to elaborate more on the idea of probability. For the sake of this course, we need to know that psi represents the wave function itself, while (psi)^2 is the probability of finding an electron in a certain region of the wave function. The double deri...
Thu Nov 05, 2020 3:49 pm
Forum: Resonance Structures
Topic: Delocalized Electrons
Replies: 5
Views: 24

### Re: Delocalized Electrons

Ok so I am going to present my interpretation of the lesson. Take nitrate ion for example. It has 3 resonance structures, each with the N=O double bond in different places. I think what Dr. Lavelle was indicating is that the electrons involved in the double bond at one moment could later be involved...
Thu Nov 05, 2020 3:43 pm
Forum: Quantum Numbers and The H-Atom
Topic: Angular momentum quantum #s over 3
Replies: 4
Views: 14

### Re: Angular momentum quantum #s over 3

In the case of this course, we only work with the s,p,d,and f orbitals. If I am not mistaken there is also a g orbital that is not heavily studied in this course. For our purposes, we are only concerned with the s,p,d,and occasionally the f orbitals. I am sure there are more, but they are outside th...
Tue Nov 03, 2020 5:15 pm
Forum: Trends in The Periodic Table
Replies: 8
Views: 62

The radius at that point depends on the nuclear charge. That is, the more protons in the nucleus, the greater the attraction between the nucleus and the individual electrons. If there are more protons in the nucleus, the distance between the valence electrons and the nucleus decreases, and hence the...
Tue Nov 03, 2020 5:11 pm
Forum: Properties of Electrons
Topic: Orbital Energies
Replies: 5
Views: 95

### Re: Orbital Energies

This concept relates to the calculation of electrostatic potential, which i don't think we have to know. We have to be able to relate electrostatic potential energy to ionization energy, but the actual calculation of either is not relevant to the course. However, if you are still curious about the t...
Sun Nov 01, 2020 9:36 pm
Forum: Photoelectric Effect
Topic: N initial vs. N final
Replies: 7
Views: 101

### Re: N initial vs. N final

The initial energy state is usually the state in which an electron begins. If it absorbs light, it will be excited to a higher level, but emitting light causes it to fall to a lower level. Basically the initial energy state will be given to you most of the time and will move between energy levels de...
Sat Oct 31, 2020 5:34 pm
Forum: Trends in The Periodic Table
Topic: Oxygen and Ionization Energy
Replies: 9
Views: 43

### Re: Oxygen and Ionization Energy

The difference depends upon the electron configurations. Looking at nitrogen, the 2p subshell has one electron in each of the x, y, and z states. Oxygen adds an electron to the 2px state. So in this case, the 2px state experiences a sense of electron repulsion, where it is easier to remove the elect...
Sat Oct 31, 2020 5:13 pm
Forum: Properties of Electrons
Topic: Sapling #28
Replies: 4
Views: 39

### Re: Sapling #28

Yes this seems correct. This way you would end with Phosphorus, or P. Is this what you got?
Sat Oct 31, 2020 4:35 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Sapling #21
Replies: 3
Views: 50

### Re: Sapling #21

so its not exactly calculations, but it is rather looking at the restrictions. For the n=3 subshell, 3 subshells exist: 3s, 3p, and 3d. Each s, p, and d subshell can hold 2, 6, and 10 electrons, respectively. So the maximum electrons available in the n=3 state is 2+6+10=18 electrons For n=4 and l=0,...
Fri Oct 30, 2020 3:03 pm
Forum: Trends in The Periodic Table
Topic: Trends
Replies: 14
Views: 88

### Re: Trends

For atomic radius and ionic radius, the trend is that it decreases as you move left on the periodic table and increases going down. I will first discuss the easier vertical trend. As you progress down the periodic table, the principle quantum number n increases. This increase means that there are mo...
Fri Oct 30, 2020 2:55 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Vs. Covalent
Replies: 7
Views: 63

### Re: Ionic Vs. Covalent

To add, ionic bonds usually form between a metal and a nonmetal, while covalent bonds usually form between nonmetals only. Hope this helps!
Fri Oct 30, 2020 2:54 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Numbers Question
Replies: 2
Views: 49

### Re: Quantum Numbers Question

I'm gonna interpret this as a general quantum numbers question. The first number, the principle quantum number n, refers to the exact energy level an electron is located on. The second number is l, which specifies the type of subshell the electron is located in; for this term usually s=0, p=1, d=2, ...
Fri Oct 30, 2020 2:41 pm
Forum: Trends in The Periodic Table
Topic: Electron configuration
Replies: 2
Views: 30

### Re: Electron configuration

Hello! I think it changes because some of the subshells on the n=4 shell are lower in energy than some in the n=3 shell. For instance, if we consider the electron configuration of Zn, it follows such that the configuration is [Ar]4s^2,3d^10. I used the noble gas configuration for simplification, and...
Sun Oct 25, 2020 12:18 pm
Forum: Photoelectric Effect
Topic: Mass of atoms
Replies: 18
Views: 105

### Re: Mass of atoms

Hello!

Masses should always be in kilograms since we use them in the context of Joules (which is kg m^2/s^2). This way the units cancel. As for your second question, we do not need to memorize any masses as they are given to us on the equations and constants sheet. Hope this helps!
Sun Oct 25, 2020 12:15 pm
Forum: Balancing Chemical Reactions
Topic: M.9 Net Ionic Equations
Replies: 2
Views: 54

### Re: M.9 Net Ionic Equations

Hello! a) Precipitation reactions always result in double displacement. So the combination of copper (II) Nitrate and sodium hydroxide will produce copper (II) hydroxide and sodium nitrate (Be sure to balance first!!). Using solubility rules, we can determine that Cu(OH)2 is the precipitate, and the...
Sun Oct 25, 2020 12:09 pm
Forum: Balancing Chemical Reactions
Topic: M.9 Net Ionic Equations
Replies: 2
Views: 54

### Re: M.9 Net Ionic Equations

Hello! Precipitation reactions always result in double displacement. So the combination of copper (II) Nitrate and sodium hydroxide will produce copper (II) hydroxide and sodium nitrate (Be sure to balance first!!). Using solubility rules, we can determine that Cu(OH)2 is the precipitate, and theref...
Sat Oct 24, 2020 1:49 pm
Forum: *Shrodinger Equation
Replies: 4
Views: 39

So I am going to assume that you are referencing the Schrodinger equation, since that question is brought up in a lot of lectures and discussions. The only thing we have to know about the Schrodinger equation is that it gives rise to different wave functions that necessitate the need for quantum num...
Sat Oct 24, 2020 1:43 pm
Forum: Properties of Light
Topic: Application of Equations to Experiments
Replies: 2
Views: 38

### Re: Application of Equations to Experiments

I am sure that these same ideas can be applied to other experiments (such as mulit-electron atoms). However, the experiments that Dr. Lavelle uses in his lectures are primarily for the purpose of explaining concepts with a more simple experiment. In other words, he probably uses experiments that are...
Tue Oct 20, 2020 1:40 pm
Forum: DeBroglie Equation
Topic: De Brogile Wavelength Car Ex. from Lecture 8
Replies: 7
Views: 76

### Re: De Brogile Wavelength Car Ex. from Lecture 8

It was mentioned in the lecture that the minimum detectable wavelength is about an angstrom, which is 1^-10 m. Usually, the minimum detectable wavelength has an extent of about 1^-14 m, but anything shorter than this is not detectable. Hope this helps!
Tue Oct 20, 2020 1:38 pm
Forum: Quantum Numbers and The H-Atom
Topic: 1D.23 on Homework
Replies: 3
Views: 48

### Re: 1D.23 on Homework

Hello! a) n=2 refers to the second energy level, and l=1 refers to the p orbital, and it is known that any p orbital has 3 orbitals. b and d) Any time we are given an ml value, this refers to a single electron inside an orbital, so this will always be 1 (if I am not mistaken) c)n=2 refers to the sec...
Tue Oct 20, 2020 1:34 pm
Forum: Einstein Equation
Topic: E=hv vs. Ephoton = Erequired + KEelectron
Replies: 2
Views: 41

### Re: E=hv vs. Ephoton = Erequired + KEelectron

To add on to what was already said, hv represents the energy of the photon directed at an electron (lets use an electron for the sake of simplicity). For questions relating to the equation in the subject, two of the entities will be given and we will usually have to solve for a third. However, the q...
Sun Oct 18, 2020 5:22 pm
Forum: Einstein Equation
Topic: workshop wk2question
Replies: 2
Views: 29

### Re: workshop wk2question

Hello! So I realize that intensity and energy may be confusing, so I will clarify here. First for simple definitions: intensity refers to the amount of photons of light that are being directed at an object, and energy is the amount of physical ability that the photons have to remove an electron. Now...
Sat Oct 17, 2020 4:16 pm
Forum: Properties of Light
Topic: Exercise 1A.15
Replies: 3
Views: 53

### Re: Exercise 1A.15

Hey Adam! So the equations may be confusing, but when you are dealing with a change in energy, only use the Rydberg Equation, which is En=(hR)/n^2. In other words, the energy change between levels is not calculated using wavelength, frequency, etc. It's found using this equation. The change in energ...
Sat Oct 17, 2020 4:00 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty in speed post module #18
Replies: 1
Views: 32

### Re: Uncertainty in speed post module #18

Hey Kayko! So basically the premise of what the question is talking about is the Heisenberg Uncertainty Principle. It starts with (delta)p*(delta)x>/=h/(4*pi). The question gives you what the uncertainty in the position is, which is 0.05*10^-9*0.01. Using all these values, find what the change in mo...
Fri Oct 16, 2020 11:48 am
Forum: Properties of Electrons
Topic: Bound vs. Free Electrons
Replies: 6
Views: 57

### Re: Bound vs. Free Electrons

I think by free electrons he means the ones that have been ejected. At about the 17 minute timestamp of the 10/16 lecture he indicates that the En value approaches 0 as n approaches infinite, or in a sense when the electrons are free. All of the non-infinite levels of n have a negative energy value,...
Fri Oct 16, 2020 11:45 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: In class question
Replies: 3
Views: 58

### Re: In class question

Hey Norah! Yes the equation you have listed would work fine as well! Knowing that E=h*frequency, both sides of the original equation are practically divided by Planck's constant, or h. Dividing by h on the left side gives you (delta)E/h, which results in the frequency. And dividing h out of the righ...
Wed Oct 14, 2020 12:27 pm
Forum: Properties of Light
Topic: Memorization of Increasing Energy
Replies: 4
Views: 57

### Re: Memorization of Increasing Energy

Hey Inderpal! I'm not sure if it is 100% necessary, but I suggest doing so just in case! I don't think there will be questions that indicate to blatantly "rank" them by decreasing wavelength, decreasing energy, etc. But it may ask us to find a wavelength or frequency and then indicate whic...
Mon Oct 12, 2020 2:46 pm
Forum: Properties of Light
Topic: 1A.7
Replies: 2
Views: 51

### Re: 1A.7

Hey Lisa! So I am unsure as to what the textbook says is the answer but i can indicate that the wavelength for b should be much smaller than that of part a! Translating it to smaller units, part a should be in nanometers and part b in picometers due to the higher frequency in part b. Hope this helps...
Mon Oct 12, 2020 2:14 pm
Forum: Photoelectric Effect
Topic: Lecture 5
Replies: 5
Views: 90

### Re: Lecture 5

Hello all! So I think as I was watching the lecture 5 this morning I made an important distinction. Increasing the intensity of the light implies that you are increasing its amplitude, which means that there is more light, but it has the same wavelength and frequency since amplitude is not correlate...
Thu Oct 08, 2020 11:48 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Sapling E.5
Replies: 3
Views: 52

### Re: Sapling E.5

Hello! The title indicates Sapling, but I will assume that this question is from the textbook. To find the moles of people, the given 7 billion should be divided by 6.022*10^23 people. In this case the units are (people)/(people/mole), leaving you with an answer in moles. For part b, we will assume ...
Thu Oct 08, 2020 11:40 am
Forum: Limiting Reactant Calculations
Topic: Sapling Homework Week 1 Q10
Replies: 6
Views: 133

### Re: Sapling Homework Week 1 Q10

Hey Jalyn! So you are on the right track with converting to the moles of the 2-butanone. You use the mole ratio of 2-butanone to 3-methyl-3-hexanone and the molar mass of the product, which is C7H16O, to obtain the grams of your product. This will give you your theoretical yield. Divide the given ac...
Mon Oct 05, 2020 7:55 pm
Forum: Limiting Reactant Calculations
Topic: Determining Limiting Reactant
Replies: 7
Views: 57

### Re: Determining Limiting Reactant

Hey John,

Unfortunately this is the only way to do it. Even though its not that efficient, converting all of the reactants to products and choosing the lowest product value is probably the most accurate way to do it.
Mon Oct 05, 2020 6:03 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E9
Replies: 7
Views: 110

### Re: E9

The term "formula units" is used when referring to an ionic compound in comparison to a molecular compound. Sorry, I still don't quite understand how that indicates that you should find the number of molecules. Could you elaborate? A formula unit is essentially one unit of a full compound...
Mon Oct 05, 2020 4:44 pm
Forum: Balancing Chemical Reactions
Topic: State in chemical reactions
Replies: 13
Views: 117

### Re: State in chemical reactions

Hey Emily! So I can recall from the pre-recorded lecture today, specifically the equation in which sodium metal reacts with water, that the states were not 100% necessary. I believe the focus on balancing the chemical equations is to simply do just that. I think the lecture said that if possible, we...
Mon Oct 05, 2020 10:25 am
Forum: Molarity, Solutions, Dilutions
Topic: Diluting a Solution
Replies: 9
Views: 98

### Re: Diluting a Solution

So I am slightly confused by the wording of this question, but I am going to try to address it. When you transfer a solution to another empty beaker, that is completely different from a dilution. When transferring a solution to an empty beaker, the concentration remains the same. Dilutions are conce...
Mon Oct 05, 2020 10:20 am
Forum: Significant Figures
Topic: Significant Figures In A Given Weight
Replies: 11
Views: 186

### Re: Significant Figures In A Given Weight

For that question I believe that since 7 is an integer, there is no specific amount of significant figures that you should use. I would suggest using only 1 anyway since there are no zeros after the integer, just to be safe. Usually for questions involving moles and grams, you should use the least n...
Fri Oct 02, 2020 7:25 pm
Forum: Empirical & Molecular Formulas
Topic: Mass Percent for Empirical and Molecular Formulas [ENDORSED]
Replies: 9
Views: 304

### Re: Mass Percent for Empirical and Molecular Formulas[ENDORSED]

So I don’t think it is 100% necessary to find the mass percent composition unless the question asks you to. I believe using the given mass amounts would result in the same empirical formula anyway. However, I think its best to just find the mass percent composition since it is easier to use as a ref...