Search found 83 matches

by Matthew ILG 1L
Mon Feb 10, 2020 4:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4C.3
Replies: 7
Views: 54

Re: 4C.3

Is the change in enthalpy supposed to be much larger for part b than it is for part a?
by Matthew ILG 1L
Mon Feb 10, 2020 3:21 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Example 4.c.1
Replies: 2
Views: 6

Example 4.c.1

I am on problem 4.c.3 in the book, and the example 4.c.1 is very similar to it. However, in the example, it says that Cv=5/2R, and that Cp=7/2R because in the book Cp=Cv+R.
On our equation sheet, it says that Cp=5/2R. I am confused as to which ratio is correct for Cp and Cv when converting to R.
by Matthew ILG 1L
Sun Feb 09, 2020 11:17 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework 4A13
Replies: 5
Views: 67

Re: Homework 4A13

On this same problem, why don't we use the molarity or volume of either of the compounds that are given to us in the problem? Why do we just multiply C(cal) by delta T. Hello, I believe we do this because the relationship q= -qcal is already established. It is simpler to find qcal with the informat...
by Matthew ILG 1L
Sun Feb 09, 2020 11:09 pm
Forum: Phase Changes & Related Calculations
Topic: 4B.5
Replies: 7
Views: 42

Re: 4B.5

Will the conversion of 1atm=760 Torr be given to us at all? I have yet to find that on the equations sheet from test one. I could be looking in all the wrong places though.
by Matthew ILG 1L
Sun Feb 09, 2020 10:47 pm
Forum: Administrative Questions and Class Announcements
Topic: midterm format
Replies: 8
Views: 39

Re: midterm format

There are occasionally a few true or false or fill in the blank questions thrown in to the test, but the rest is all free response.
by Matthew ILG 1L
Sun Feb 09, 2020 10:42 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Internal Energy
Replies: 4
Views: 127

Re: Internal Energy

I was just on this problem and luckily found this post. Are we supposed to know that 1atm is equivalent to 760 torr or is that somewhere on the equation sheet? Also how do we convert from L*atm to kJ?
by Matthew ILG 1L
Sun Feb 09, 2020 10:23 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: m and n in heat capacity
Replies: 4
Views: 17

Re: m and n in heat capacity

I believe that the mass and moles can both be used because the two can be converted back an forth, given the correct and necessary information. They both work, similar to how ceclius and kelvin both work at times. It can be changed to moles or to grams, but we do not need to because the equation wor...
by Matthew ILG 1L
Sun Feb 09, 2020 10:17 pm
Forum: General Science Questions
Topic: Midterm Review Questions ?
Replies: 3
Views: 34

Re: Midterm Review Questions ?

Thank you both very much. That is very helpful.
by Matthew ILG 1L
Sun Feb 09, 2020 9:55 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework 4A13
Replies: 5
Views: 67

Re: Homework 4A13

On this same problem, why don't we use the molarity or volume of either of the compounds that are given to us in the problem? Why do we just multiply C(cal) by delta T.
by Matthew ILG 1L
Sun Feb 09, 2020 8:46 pm
Forum: Phase Changes & Related Calculations
Topic: reversible
Replies: 4
Views: 17

Re: reversible

A reversible reaction is basically when the reactants form products that, in turn, react together to give the reactants back. It is shown by the two way arrows usually.
by Matthew ILG 1L
Sun Feb 09, 2020 8:44 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Intensive vs. Extensive
Replies: 14
Views: 34

Re: Intensive vs. Extensive

Extensive properties, such as mass and volume, depend on the amount of matter being measured. Intensive properties, such as density and color, do not depend on the amount of the substance present
by Matthew ILG 1L
Sun Feb 09, 2020 8:35 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Entropy in reversible reactions
Replies: 2
Views: 15

Re: Entropy in reversible reactions

ΔS total =ΔS system +ΔS surrounding So if the ΔS total =0, then ΔS system = -ΔS surrounding They will not always be equal and opposite, but that is typically when this relationship will be important. Also, you could solve for ΔS system and ΔS surrounding and add if the question is asking for the ΔS...
by Matthew ILG 1L
Sun Feb 09, 2020 8:33 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Volume decrease
Replies: 7
Views: 33

Re: Volume decrease

The rule of less moles only applies when you are dealing with gases. If the substances in the rxn are not gases, then I do not believe the rule applies.
by Matthew ILG 1L
Sun Feb 09, 2020 8:32 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: reversible vs. irreversible
Replies: 3
Views: 15

Re: reversible vs. irreversible

In a irreversible reaction, the reactants react to form the products, which cannot revert back into reactants. In reversible reactions, as the reactants react with other reactants to form products, the products are reacting with other products to form reactants. Combustion is an example of an irreve...
by Matthew ILG 1L
Sun Feb 09, 2020 8:30 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Weak acid/base
Replies: 14
Views: 42

Re: Weak acid/base

Mariana Fuentes 1L wrote:Does that mean that Ka and pKa are kind of opposite?

Yes exactly!! The smaller the value of Ka, the larger the value of pKa, the weaker the acid.
by Matthew ILG 1L
Sun Feb 09, 2020 8:29 pm
Forum: General Science Questions
Topic: Midterm Review Questions ?
Replies: 3
Views: 34

Midterm Review Questions ?

I'm going through and doing problems from each section of the book to prepare for the midterm. Does anyone have any especially good problems they would suggest doing in preparation for the midterm? Can be from any section we have covered. Thank you
by Matthew ILG 1L
Sun Feb 09, 2020 8:27 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE BOX
Replies: 27
Views: 73

Re: ICE BOX

I believe that Dr. Lavelle said we can ignore x when K<10^-3.
by Matthew ILG 1L
Thu Feb 06, 2020 7:21 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: 3rd Law
Replies: 4
Views: 12

Re: 3rd Law

The third law acts similar to a limit function in calculus:
As the temperature of the system approaches absolute zero, the entropy of the system approaches zero.
by Matthew ILG 1L
Wed Feb 05, 2020 8:28 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: closed vs isolated
Replies: 14
Views: 41

Re: closed vs isolated

Isolated systems are completely sealed and closed off. Imagine a test tube with a lid on it, then wrapped completely in a "puff jacket" as Dr. Lavelle said in his in class example from a few weeks ago. It does not interact with its environment at all.
by Matthew ILG 1L
Wed Feb 05, 2020 8:22 pm
Forum: General Science Questions
Topic: Class before Midterm
Replies: 2
Views: 27

Class before Midterm

Does anybody know if we will be learning new material for the entirety of Friday's class, or will part of it be review and example problems for the midterm?
by Matthew ILG 1L
Sun Feb 02, 2020 9:01 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Shifts
Replies: 5
Views: 19

Re: Shifts

If you are referring to K value vs Q value:
When Q>K, the rxn will shift to the left, creating more reactants
When Q<K, the rxn will shift to the right, creating more products
by Matthew ILG 1L
Sun Feb 02, 2020 8:53 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: U and H
Replies: 2
Views: 22

Re: U and H

U = q - w is used when there is heat added to the system (q). H = U + PV is under constant pressure and constant temperature.
by Matthew ILG 1L
Sun Feb 02, 2020 8:01 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Types of entropy
Replies: 2
Views: 11

Re: Types of entropy

I may be wrong, but I believe the Boltzmann equation is still used for positional entropy.
by Matthew ILG 1L
Thu Jan 30, 2020 1:01 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Celcius and Kelvin
Replies: 11
Views: 29

Re: Celcius and Kelvin

We needed to know the conversion from celcius to kelvin on the last test, so I assume that on the midterm and other tests we will need to have it memorized as well. However, I do not believe we need to use the exact conversion value of 273.15, but rather we are bale to use 273.
by Matthew ILG 1L
Thu Jan 30, 2020 12:59 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: memorize
Replies: 6
Views: 17

Re: memorize

Water is one heat capacity you should memorize. Other than that, the heat capacity of different elements is usually given in the specific problem.
by Matthew ILG 1L
Wed Jan 29, 2020 1:19 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs isolated systems
Replies: 24
Views: 64

Re: Closed vs isolated systems

Dr. Lavelle gave a good example today in lecture. He said a closed system in a closed system, energy can still exchange with surrounding, but matter is not exchanged (i.e a sealed beaker of water. the beaker does not insulate) In a isolated system, nothing exchanged with the surroundings. It is as i...
by Matthew ILG 1L
Wed Jan 29, 2020 12:55 pm
Forum: Lewis Acids & Bases
Topic: Lewis acid and bases
Replies: 5
Views: 26

Re: Lewis acid and bases

Lewis acids and bases are defined in terms of being able to accept or donate electron pairs, while Bronsted Lowry acids and bases are defined in terms of being able to accept or donate hydrogen ions ( H+ )
by Matthew ILG 1L
Wed Jan 29, 2020 12:54 pm
Forum: Administrative Questions and Class Announcements
Topic: 14A Final Pickup
Replies: 3
Views: 24

Re: 14A Final Pickup

Thank you! I still have yet to pick mine up as well.
by Matthew ILG 1L
Wed Jan 29, 2020 12:47 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Work
Replies: 6
Views: 37

Re: Work

"In chemistry, the convention is that anything going out of the system is negative and anything coming into the system is positive. If your system is a gas in a piston, work is being done on the system when it is being compressed, so the work done on the system is positive, and the work done by...
by Matthew ILG 1L
Sat Dec 07, 2019 1:32 pm
Forum: Bronsted Acids & Bases
Topic: Naming Acids and Bases
Replies: 1
Views: 20

Naming Acids and Bases

On question 6.A.7, it asks us to write the name of each acid based on the molecular drawing (HClO3 and HNO3).
Is there a list of acid names we are expected to memorize and know, or is there a way to know the names of these acids based on the formula and atoms within it.
by Matthew ILG 1L
Sat Dec 07, 2019 1:28 pm
Forum: Hybridization
Topic: 2sp2 vs sp2
Replies: 3
Views: 21

Re: 2sp2 vs sp2

You usually add the 2 i front of the sp2 when you are describing the hybridization of a bond. If you are just describing the hybridization of an individual molecule, I don't believe that you need the 2 in front.
by Matthew ILG 1L
Fri Dec 06, 2019 4:30 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Deciding shape
Replies: 3
Views: 35

Re: Deciding shape

If you determine the coordination number you can determine how many molecules bond to it, if you find this out you can find the molecular shape. I agree with this. the coordination number helps you determine the shape. Some common ones are: CN=6 is Octahedral CN=4 is tetrahedral or in the case of c...
by Matthew ILG 1L
Fri Dec 06, 2019 4:25 pm
Forum: Naming
Topic: Naming
Replies: 2
Views: 24

Re: Naming

The Ta's and Ua's have said that either is acceptable as well. Which ever naming convention is easiest for you to remember.
by Matthew ILG 1L
Fri Dec 06, 2019 4:23 pm
Forum: Conjugate Acids & Bases
Topic: Conjugate acids and bases
Replies: 2
Views: 21

Re: Conjugate acids and bases

In addition to this, a weak acid leads to a strong conjugate base. And vise versa, a strong acid leads to a weak conjugate base.
by Matthew ILG 1L
Mon Dec 02, 2019 11:30 pm
Forum: Naming
Topic: Cyano vs. Cyanido
Replies: 2
Views: 24

Re: Cyano vs. Cyanido

I found a chem community post from 2011 that said this:
"They are actually the same ligand, but the the first (cyano) is an older naming convention. Cyanido is the IUPAC preferred name for the ligand".
It also says that both forms are acceptable.
by Matthew ILG 1L
Mon Dec 02, 2019 11:28 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 9 and 10 Homework
Replies: 2
Views: 37

Re: Week 9 and 10 Homework

Coordination compounds and acid and base structures are the newest material, but I'm pretty sure that if you do older problems as a way to review for the final your TA will accept that as well. But it may be better to be safe and just turn in problems from the coordination compounds and acid and bas...
by Matthew ILG 1L
Mon Dec 02, 2019 11:26 pm
Forum: General Science Questions
Topic: Final test locations
Replies: 4
Views: 69

Re: Final test locations

I'm sure he will also show the locations on a slide in class on Wednesday or Friday, like he did for the midterm. He showed a quick glimpse of it in class today as well, and I believe A-L last names are in CS50, though I'm not sure where M-Z last names are.
by Matthew ILG 1L
Mon Dec 02, 2019 11:18 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strength of Strong Acids
Replies: 2
Views: 23

Re: Strength of Strong Acids

I believe that the stronger the acid, the weaker the bond, and therefore the easier it is for that bond to break and for the acid to completely dissociate in water. So to answer your question, what sets certain acids apart as "stronger" and varying levels of dissociating completely is the ...
by Matthew ILG 1L
Mon Dec 02, 2019 10:49 pm
Forum: Naming
Topic: Latin names of Elements
Replies: 1
Views: 18

Latin names of Elements

Will we be required to know and memorize the latin names of elements for the final? A video I watched kept using the latin names, such as cobalt being cobaltate and platinum being platinate when naming their coordinate compounds. Will a list of latin anmes of elements be given on the final or do we ...
by Matthew ILG 1L
Sun Dec 01, 2019 6:51 pm
Forum: Administrative Questions and Class Announcements
Topic: Points
Replies: 11
Views: 100

Re: Points

I have heard that the discussion posts have been graded both ways in the past. Some years they grade on a week to week basis and other years they simply check your total number of posts at the very end. It is good to try and stay up to date, but if you fall behind, talking with your TA is never a ba...
by Matthew ILG 1L
Sun Dec 01, 2019 6:42 pm
Forum: General Science Questions
Topic: Memorization for Final
Replies: 2
Views: 24

Re: Memorization for Final

You will also need to know unit conversions I believe, such as grams to kilograms or meters to nanometers.
by Matthew ILG 1L
Sun Dec 01, 2019 6:36 pm
Forum: General Science Questions
Topic: Week 10 Classes
Replies: 7
Views: 98

Week 10 Classes

Will we be learning new material throughout the entirety of this week (December 2-6) for the final? Or will the last Friday of class be a review day for our final?
by Matthew ILG 1L
Sun Dec 01, 2019 6:33 pm
Forum: Student Social/Study Group
Topic: Final Studying
Replies: 8
Views: 41

Re: Final Studying

In addition to the review sessions, are there any specific videos or chemistry youtubers you would suggest watching who are good at teaching the more conceptual things?
by Matthew ILG 1L
Sun Dec 01, 2019 6:30 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Relative acidity
Replies: 7
Views: 47

Re: Relative acidity

The strength of an acid depends on two things: The strength of the A-H bond, and the stability of the resulting anion. Bond strength is related to the length of the bond, and because Iodine has a much larger atomic radius than Fluorine, HI has a much longer, and therefore weaker, bond. The hydrogen ...
by Matthew ILG 1L
Sun Dec 01, 2019 6:27 pm
Forum: Student Social/Study Group
Topic: Study Strategies
Replies: 6
Views: 38

Re: Study Strategies

It sounds like you are doing fine in the class. I would say that reading over some of the textbook and attending the workshops are very helpful in reviewing and applying what we learned in lecture. When reading over the textbook do you suggest taking notes? I have tried to read it and it just gets ...
by Matthew ILG 1L
Sun Dec 01, 2019 6:25 pm
Forum: Lewis Acids & Bases
Topic: Difference between Lewis and Bronsted Acids?
Replies: 2
Views: 17

Re: Difference between Lewis and Bronsted Acids?

The Bronsted definition: an acid is a proton (H+ ion) donor, and a base is a proton acceptor
The Lewis definition: an acid is an electron acceptor, and a base is an electron donor.
by Matthew ILG 1L
Wed Nov 27, 2019 4:43 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: Test 2 7a
Replies: 6
Views: 53

Re: Test 2 7a

Yes, you coun't the number of lone pairs and hydrogens and you should get 11 bonding sites. You may get 12 but my TA said that the Hydrogen that is on the most far right that is bonded to carbon cannot form a hydrogen bond because hydrogens need to bond to N O or F (or small molecules..) and since ...
by Matthew ILG 1L
Wed Nov 27, 2019 4:42 pm
Forum: Sigma & Pi Bonds
Topic: Question on Test 2
Replies: 11
Views: 120

Re: Question on Test 2

For this question, you had to be able to identify that all the single bonds had a sigma bond in it and that all the double bonds that a sigma bond and a pi bond in it. When counting the number of hydrogen bonding sites you need to include the H-bonds already present and the lone pairs on N,O, or F....
by Matthew ILG 1L
Wed Nov 27, 2019 4:35 pm
Forum: Hybridization
Topic: sigma or pi?
Replies: 20
Views: 102

Re: sigma or pi?

The way i remember is: Sigma=Single. The double S helps me out. Also sigma bonds are every bond in a structure.
by Matthew ILG 1L
Wed Nov 27, 2019 4:33 pm
Forum: Bronsted Acids & Bases
Topic: Acids vs Bases
Replies: 5
Views: 28

Re: Acids vs Bases

In addition to the difference between acids and bases, there is also a difference between organic acids and bases vs inorganic acids and bases. Acids containing carbon are known as organic acids. Bases containing carbon are known as organic bases. Acids that do NOT contain carbon are known as inorga...
by Matthew ILG 1L
Wed Nov 27, 2019 4:30 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Inorganic vs organic
Replies: 5
Views: 27

Re: Inorganic vs organic

Acids containing carbon are known as organic acids. Bases containing carbon are known as organic bases. Acids that do NOT contain carbon are known as inorganic acids or mineral acids. Bases that do NOT contain carbon are known as inorganic bases.
by Matthew ILG 1L
Thu Nov 14, 2019 1:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 2
Replies: 15
Views: 155

Re: Test 2

What topics should we expect to show up on test #2? From what I've heard, Test 2 will cover material up until Friday's lecture. Based on this, questions on Test 2 can appear from any material up until VSEPR. This includes, but is not limited to: 1. Review of high school chemistry 2. Quantum 3. Chem...
by Matthew ILG 1L
Thu Nov 14, 2019 1:13 pm
Forum: Student Social/Study Group
Topic: Final Exam
Replies: 10
Views: 70

Re: Final Exam

So the final is cumulative, but Test #2 is just information from after the midterm?
by Matthew ILG 1L
Thu Nov 14, 2019 1:12 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: Test Topics
Replies: 11
Views: 88

Re: Test Topics

We won't have to draw VSEPR models, but we will most likely have to draw lewis structures and be able to label the VSEPR information.
by Matthew ILG 1L
Thu Nov 14, 2019 1:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle
Replies: 9
Views: 47

Re: Bond Angle

When labeling the bonds in a trigonal pyramidal model are we allowed to say that it is 109.5 degrees or do we have to specify that it is slightly less than that?
by Matthew ILG 1L
Thu Nov 14, 2019 12:57 pm
Forum: Administrative Questions and Class Announcements
Topic: Test #2
Replies: 4
Views: 28

Re: Test #2

I assume we will need to know how to do Lewis Structures, which was taught before the midterm, in order to label VSEPR models. But other than that I am not sure how much we will need to know or study from before the midterm.
by Matthew ILG 1L
Thu Nov 14, 2019 12:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Arrangement vs Shape
Replies: 3
Views: 17

Re: Arrangement vs Shape

If "arrangement" is referring to the Lewis Structure and "shape" is referring to VSEPR model, then the arrangement is a 2-dimensional view of the molecular configuration, while the shape is a 3-dimensional model that has more specific angles.
by Matthew ILG 1L
Sun Nov 10, 2019 11:21 pm
Forum: Electronegativity
Topic: Atom size
Replies: 16
Views: 165

Re: Atom size

I don't believe that electronegativity and atomic radius are directly related. However, their trends are opposite, with the atomic radius increasing down and to the left and the electronegativity increasing up and to the right. It is a case of correlation without causation I believe.
by Matthew ILG 1L
Sat Nov 02, 2019 3:45 pm
Forum: General Science Questions
Topic: Can We Take The Final In Pencil?
Replies: 14
Views: 531

Re: Can We Take The Final In Pencil?

The syllabus says that only pens are allowed on tests. I have always used pencils for homework and other classes because I always am erasing things. But with a pen I have just started putting a large "x" over whatever I would normally erase.
by Matthew ILG 1L
Sat Nov 02, 2019 2:57 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Calculator rounding
Replies: 3
Views: 41

Re: Calculator rounding

What type of calculator are you using? Also if you are rounding during intermediate values during the equation process that may be a reason that you are ending with a rounded value.
by Matthew ILG 1L
Sat Nov 02, 2019 2:46 pm
Forum: Trends in The Periodic Table
Topic: Exceptions
Replies: 3
Views: 21

Re: Exceptions

The trends, such as electronegativity, atomic radius, and ionization energy, are typically very straight forward and have little to no exceptions.
by Matthew ILG 1L
Sat Nov 02, 2019 2:40 pm
Forum: Octet Exceptions
Topic: Expanded Valence Shells
Replies: 4
Views: 23

Re: Expanded Valence Shells

8 valence electrons is the limit for an element to hold in a given shell. If there are more than 8, then a new shell is formed.
by Matthew ILG 1L
Sat Nov 02, 2019 2:37 pm
Forum: Octet Exceptions
Topic: Exceptions?
Replies: 5
Views: 35

Re: Exceptions?

The way I learned in high school, the elements in third period and below are typically allowed to break the octet rule.
by Matthew ILG 1L
Sat Oct 26, 2019 11:27 pm
Forum: Resonance Structures
Topic: Bond lengths
Replies: 5
Views: 32

Re: Bond lengths

Bonds lengths are measured in angstroms, the stronger the bond, the shorter the lengths. The length will be given to us I believe, as was the case in Wednesday's lecture when the Dr. Lavelle stated in a slide "Observed N--O bond length in (NO3)- = 1.24 Angstroms. "
by Matthew ILG 1L
Sat Oct 26, 2019 11:15 pm
Forum: General Science Questions
Topic: Week 5 homework
Replies: 2
Views: 28

Re: Week 5 homework

For week 5, I was still doing some hw from the "quantum world" section. The problems seem to still be relevant with the notes, although I did do half of my problems on "chemical bonds" as well.
by Matthew ILG 1L
Sat Oct 26, 2019 11:10 pm
Forum: Lewis Structures
Topic: Reasoning for the octet
Replies: 3
Views: 34

Re: Reasoning for the octet

The reasoning for the octet rule that I learned in high school is that atoms "want" to be like the noble gases (He, Ne, Ar, Kr, Xe, Rn) and have 8 electrons in their outer shell, because electrons are most stable with a full outer shell.
by Matthew ILG 1L
Sat Oct 26, 2019 11:04 pm
Forum: Bond Lengths & Energies
Topic: Bond Lengths
Replies: 4
Views: 41

Re: Bond Lengths

An easy way I like to remember that double bonds are shorter and stronger than single bonds is I think of them as sticks. Longer, skinnier sticks are easier to break i.e. weaker bond. The shorter and wider the stick, or in our case, the bond (triple bond), the stronger it is.
by Matthew ILG 1L
Sat Oct 26, 2019 10:49 pm
Forum: Lewis Structures
Topic: Drawing the Lewis Structure
Replies: 2
Views: 24

Re: Drawing the Lewis Structure

The Lewis Structure should typically be symmetrical, with the singular element in the center.
by Matthew ILG 1L
Thu Oct 17, 2019 10:44 pm
Forum: Einstein Equation
Topic: unit of energy
Replies: 7
Views: 284

Re: unit of energy

I know the problem you're referring to. Its 1.B.5. You have to convert the 140.511keV to eV by multiplying it by 10^3, and then multiply the eV by 1.6022x10^-19J to find the J.
by Matthew ILG 1L
Thu Oct 17, 2019 8:46 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Drawing Orbitals
Replies: 5
Views: 40

Re: Drawing Orbitals

I have found in the past that drawing orbitals actually helps me understand the orbital levels better than just looking at it quantitatively. But there are others who would not benefit from drawing circles in a chemistry class.
by Matthew ILG 1L
Thu Oct 17, 2019 8:43 pm
Forum: *Shrodinger Equation
Topic: derivation
Replies: 5
Views: 34

Re: derivation

Having the equation sheet on the tests and quizzes, I would think that it is not too important to know how to derive the equations. There are many equations that are extremely complicated and time consuming to prove as well. I think that if Dr. Lavelle has proved the equation on the board during a l...
by Matthew ILG 1L
Thu Oct 17, 2019 8:41 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Why divide h by 4pi?
Replies: 5
Views: 48

Re: Why divide h by 4pi?

The only real way to see why h is divided by 4pi is to prove the entire equation, which is a very long and arduous process. However, if you are interested in it, here is a helpful link showing the proof.
https://www.quora.com/Why-is-h-divided- ... -principle
by Matthew ILG 1L
Thu Oct 17, 2019 8:30 pm
Forum: Balancing Chemical Reactions
Topic: Determining the state of matter
Replies: 4
Views: 55

Re: Determining the state of matter

Often times when there are two of a molecule in a balanced equation, such as 0subscript2 or Hsubscript2, it is a gas.
by Matthew ILG 1L
Thu Oct 10, 2019 6:38 pm
Forum: Photoelectric Effect
Topic: Work Function
Replies: 4
Views: 59

Re: Work Function

It seemed to me that during the lecture Dr. Lavelle was using "Work Function" and "Threshold Energy" fairly interchangeably.
by Matthew ILG 1L
Thu Oct 10, 2019 6:31 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Test Equation Sheet
Replies: 8
Views: 67

Re: Test Equation Sheet

Constants such as Planck's Constant and Avogadro's number? And is Angstrom or other prefixes provided as well?
by Matthew ILG 1L
Thu Oct 10, 2019 6:20 pm
Forum: Student Social/Study Group
Topic: Pen or Pencil for Homework Problems?
Replies: 8
Views: 72

Re: Pen or Pencil for Homework Problems?

On the syllabus is says that tests and exams must be written in pen. But it does not say anything about homework.
by Matthew ILG 1L
Thu Oct 10, 2019 6:18 pm
Forum: Photoelectric Effect
Topic: Planck's Constant
Replies: 4
Views: 68

Re: Planck's Constant

Planck's Constant in measured in juuls if I am not mistaken. If that is so, then is radiation considered an energy similar to Kinetic or Thermal?
by Matthew ILG 1L
Thu Oct 10, 2019 6:12 pm
Forum: Significant Figures
Topic: Range of Sig Figs
Replies: 8
Views: 71

Re: Range of Sig Figs

Was there also a different rule for sig figs when dealing with addition/subtraction problems vs. multiplication/division problems? I think I remember learning something about that in high school but I can't remember.
by Matthew ILG 1L
Tue Oct 01, 2019 9:04 pm
Forum: Limiting Reactant Calculations
Topic: Other Way to Find the Limiting Reactant [ENDORSED]
Replies: 3
Views: 77

Re: Other Way to Find the Limiting Reactant [ENDORSED]

Yes, that it another possible way to find the limiting reactant, and I believe Dr. Lavelle stated that during the lecture after the first example that you just mentioned. I prefer the second way that you mentioned myself because it is easier to compare the two or three or however many elements are p...
by Matthew ILG 1L
Tue Oct 01, 2019 8:58 pm
Forum: Significant Figures
Topic: General Rules to Help with Sig Figs
Replies: 18
Views: 214

Re: General Rules to Help with Sig Figs

This is super helpful. Especially the one about the leading zeros and the decimal at the end of a number. I will for sure be coming back to this throughout the year. Thank you very much!!
by Matthew ILG 1L
Sun Sep 29, 2019 7:22 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Accuracy vs Precision
Replies: 10
Views: 128

Re: Accuracy vs Precision

Dr. Lavelle showed this same image during the lecture last Friday, September 27th, and I found it to be very helpful and informative. https://www.google.com/url?sa=i&source=images&cd=&ved=2ahUKEwi3nceJvvfkAhWWFTQIHZGbBuwQjRx6BAgBEAQ&url=https%3A%2F%2Fsites.google.com%2Fa%2Fapaches.k1...
by Matthew ILG 1L
Sun Sep 29, 2019 7:19 pm
Forum: Administrative Questions and Class Announcements
Topic: Formatting homework
Replies: 12
Views: 153

Re: Formatting homework

Are we supposed to write a title at the top of the page such as "week 1 chem 14A homework". I definitely agree that writing your name and lecture/discussion section at the top is helpful. And I assume answers should be boxed as well yes?
by Matthew ILG 1L
Sun Sep 29, 2019 7:15 pm
Forum: Significant Figures
Topic: Constants and Sig Figs
Replies: 4
Views: 56

Re: Constants and Sig Figs

I agree with the other two responses, and it holds true the other way as well. If a given numerical value has less sig figs than a constant, the constant should not be shortened to match the sig figs of the given value. For example, if we have C with an amu of 12.01 but a value in the equation we ar...

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