Search found 57 matches
- Sun Mar 10, 2019 1:35 pm
- Forum: General Science Questions
- Topic: Free Expansion
- Replies: 3
- Views: 596
Re: Free Expansion
expansion joints on bridges and overpasses. for example, a bridge deck gets longer in the heat of summer and contracts in the cold of winter
- Sun Mar 10, 2019 1:34 pm
- Forum: Van't Hoff Equation
- Topic: Overview
- Replies: 8
- Views: 1145
Re: Overview
it relates the change in the equilibrium constant, Keq, of a chemical reaction to the change in temperature, T, given the standard enthalpy change, ΔH, for the process.
- Sun Mar 10, 2019 1:33 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test 2: Melting Ice
- Replies: 6
- Views: 1090
Re: Test 2: Melting Ice
it's a spontaneous reaction because ice will melt by itself, not needing any external heat to be added to the system, which is why deltaG is negative
- Tue Mar 05, 2019 1:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Week 9 HW
- Replies: 6
- Views: 671
Re: Week 9 HW
i think just kinetics since that's what we covered this week in class
- Tue Mar 05, 2019 1:09 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Study Advice
- Replies: 73
- Views: 7347
Re: Study Advice
attending study sessions are super helpful. and if you find a specific topic difficult, i recommend searching it on youtube and watching a video where they do practice problems
- Tue Mar 05, 2019 1:08 pm
- Forum: General Rate Laws
- Topic: Table with different Concentration
- Replies: 4
- Views: 452
Re: Table with different Concentration
i would assume so since these type of questions were asked on the homework
- Wed Feb 27, 2019 8:52 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Phases used in a Galvanic Cell
- Replies: 3
- Views: 383
Re: Phases used in a Galvanic Cell
liquids can be listed. make sure to separate them from the other phases in the diagram
- Wed Feb 27, 2019 8:46 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Predicting Gibbs Free Energy Sign
- Replies: 3
- Views: 686
Re: Predicting Gibbs Free Energy Sign
you can't predict it based on just temperature. you would need enthalpy or entropy or both
- Wed Feb 27, 2019 8:44 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.11
- Replies: 2
- Views: 352
Re: 14.11
you want to flip one of the half reactions so the electrons from each half reaction are able to cancel out. when you flip a half reaction, the sign of that cell potential will switch
- Mon Feb 18, 2019 3:38 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy Problems
- Replies: 3
- Views: 355
Re: Gibbs Free Energy Problems
we don't need to memorize any, they'll be given to us
- Mon Feb 18, 2019 3:37 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy change: V, P, T
- Replies: 4
- Views: 2986
Re: Entropy change: V, P, T
Higher volume leads to greater entropy because the larger the volume the more ways there are to distribute the molecules in that volume; the more ways there are to distribute the molecules (energy), the higher the entropy The entropy of a system decreases with an increase in pressure. This is due to...
- Mon Feb 18, 2019 3:34 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Meaning of subscript r
- Replies: 3
- Views: 2562
Re: Meaning of subscript r
I'm not sure but I think it just means reaction
- Thu Feb 14, 2019 10:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kp equilibrium constant
- Replies: 6
- Views: 1680
Re: Kp equilibrium constant
it doesn't matter what the units are as long as you keep them consistent for each molecule in the equilibrium equation
- Tue Feb 12, 2019 11:29 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy Change by Volume and Pressure
- Replies: 2
- Views: 335
Re: Entropy Change by Volume and Pressure
no you don't need to do it twice. just be consistent in either using the volumes or pressures
- Tue Feb 12, 2019 11:27 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Reasons for Heat Capacity
- Replies: 2
- Views: 280
Re: Reasons for Heat Capacity
materials with more atoms per unit volume will generally have higher heat capacities on a per-mass basis and larger molecules will have a larger heat capacity on a per-mole basis
- Tue Feb 05, 2019 5:05 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 6th edition 8.51
- Replies: 2
- Views: 344
Re: 6th edition 8.51
to find the energy density in kJ/L, divide the amount of energy with the mass of one mole of TNT(227.14 g/mol) and then multiply it by the density of TNT (1.65 g/cm^3)
- Tue Feb 05, 2019 5:02 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 6th ed 103 units
- Replies: 1
- Views: 221
Re: 6th ed 103 units
in the solution manual, it shows the answers in Joules/moles
- Tue Feb 05, 2019 5:00 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: 6th edition Hw problem 8.23
- Replies: 1
- Views: 280
Re: 6th edition Hw problem 8.23
you want to find Ccal so take 22.5 kj and divide that by the difference in temperature. your answer will be in kJ/C
- Mon Jan 28, 2019 3:44 pm
- Forum: Ideal Gases
- Topic: Problem 8.9 6th edition
- Replies: 1
- Views: 303
Re: Problem 8.9 6th edition
find the value of work by using the equation w=-Pressure * change in the volume. then to get deltaU, take q (given in the problem) and add it with work
- Mon Jan 28, 2019 3:41 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Extensive vs Intensive properties
- Replies: 4
- Views: 411
Re: Extensive vs Intensive properties
An extensive property depends on the amount of matter while an intensive property depends on what the type of matter is. an example of an extensive property would be volume while an intensive property would be hardness
- Mon Jan 28, 2019 3:39 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Neutralization reactions
- Replies: 6
- Views: 863
Re: Neutralization reactions
yes because bonds are being made, causing energy to be released into the surrounding
- Wed Jan 23, 2019 4:43 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: autoprotolysis
- Replies: 5
- Views: 673
Re: autoprotolysis
i don't think we'll need to know how to derive it but just know the relationship. but it's pretty simple to derive it so i would know it to just help you out later on
- Wed Jan 23, 2019 4:41 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Ka and pH
- Replies: 6
- Views: 527
Re: Ka and pH
i don't think there is one but just make sure to know the relationship between pka with ka and pkb with kb and you can use an ICE box to find the concentration to find the ka or kb values
- Tue Jan 22, 2019 9:38 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Does [H3O+][OH-] always equal 10^-14?
- Replies: 9
- Views: 1228
Re: Does [H3O+][OH-] always equal 10^-14?
it is 10^-14 only when water is at a constant 25 degrees C
- Tue Jan 15, 2019 1:23 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Calculate pOH
- Replies: 3
- Views: 191
Re: Calculate pOH
yes because of the 2 hydroxide ions
- Tue Jan 15, 2019 1:21 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE table
- Replies: 3
- Views: 445
Re: ICE table
you only include gases and not solids or liquids because solids/liquids concentrations are constant throughout the reaction
- Tue Jan 15, 2019 1:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE charts
- Replies: 3
- Views: 321
Re: ICE charts
for ICE charts, use concentration values
- Thu Jan 10, 2019 8:27 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Reaction quotient [ENDORSED]
- Replies: 4
- Views: 440
Re: Reaction quotient [ENDORSED]
If they're not gas, you can use the value of 1 as a replacer
- Tue Jan 08, 2019 7:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 7th Edition - 5G.3 Mistake?
- Replies: 3
- Views: 272
Re: 7th Edition - 5G.3 Mistake?
Lavelle has a link on his website that addresses any textbook mistakes, trying checking there
- Tue Jan 08, 2019 7:16 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc vs. Kp
- Replies: 7
- Views: 688
Re: Kc vs. Kp
Kp is for partial pressures, so only involves gases
- Sat Dec 01, 2018 3:44 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Dissociation energy
- Replies: 7
- Views: 665
Re: Dissociation energy
positive refers to an input of energy vs negative would be a release of energy
- Sat Dec 01, 2018 3:42 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Practice Questions for Final
- Replies: 3
- Views: 605
Re: Practice Questions for Final
lyndon's review session on tuesday should also have some good final practice
- Sat Dec 01, 2018 3:39 pm
- Forum: Octet Exceptions
- Topic: Which Elements
- Replies: 3
- Views: 615
Re: Which Elements
Sulfur, phosphorus, silicon, and chlorine are some common ones and boron and aluminum can form compounds in which they have six valence electrons
- Sun Nov 25, 2018 4:23 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2.45
- Replies: 2
- Views: 230
Re: 2.45
carbon's three bonding regions means there is one s orbital and 2 p orbitals (sp2)
- Sun Nov 25, 2018 4:21 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Test 3
- Replies: 38
- Views: 2748
Re: Test 3
i believe so and possibly some past topics may be included but i'm not sure about that
- Sun Nov 25, 2018 4:20 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Linear structure with lone pairs
- Replies: 6
- Views: 665
Re: Linear structure with lone pairs
yeah it will be 180 degrees if it's linear
- Sun Nov 25, 2018 4:19 pm
- Forum: Hybridization
- Topic: Hybridization
- Replies: 5
- Views: 583
Re: Hybridization
yeah i believe so
- Sun Nov 25, 2018 4:17 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 3
- Replies: 6
- Views: 579
Re: Test 3
Yes I believe we will need to recognize and name shapes
- Thu Nov 15, 2018 11:31 am
- Forum: SI Units, Unit Conversions
- Topic: lewis structure shape
- Replies: 6
- Views: 946
Re: lewis structure shape
in addition to knowing the shapes, also know the angles associated with them
- Thu Nov 08, 2018 11:03 pm
- Forum: Electronegativity
- Topic: Electronegativity and Polarizability
- Replies: 4
- Views: 1915
Re: Electronegativity and Polarizability
they're inversely related so a molecule with a greater electronegativity will have a lower polarizability
- Thu Nov 08, 2018 10:58 pm
- Forum: Student Social/Study Group
- Topic: Homework 6
- Replies: 5
- Views: 648
Re: Homework 6
i tried to focus on doing problems based on the lectures we've had the past week
- Thu Nov 08, 2018 10:56 pm
- Forum: Lewis Structures
- Topic: Placement of Elements?
- Replies: 5
- Views: 610
Re: Placement of Elements?
we're going to learn shape soon and then the placement will matter, but based on what we've learned so far, we don't have to have a certain placement
- Thu Nov 08, 2018 10:52 pm
- Forum: Lewis Structures
- Topic: Formal charges
- Replies: 15
- Views: 1323
Re: Formal charges
i don't think it's required unless specified. but i always do because i find it to be super helpful to figure out the most stable form of a molecule
- Thu Nov 08, 2018 10:50 pm
- Forum: Octet Exceptions
- Topic: Octet vs formal charge
- Replies: 16
- Views: 3156
Re: Octet vs formal charge
formal charge being 0 is more important because don't forget about elements that have octet exceptions
- Wed Oct 31, 2018 5:23 pm
- Forum: Lewis Structures
- Topic: Lewis Structures and adding multiple bonds
- Replies: 2
- Views: 319
Re: Lewis Structures and adding multiple bonds
you will know whether you'll need to add a double or triple bond depending if it changes the formal charge closer to 0. this means the atom will be more stable
- Wed Oct 31, 2018 5:22 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge of a compound
- Replies: 3
- Views: 465
Re: Formal Charge of a compound
yes the overall formal charge of the atom will equal the total of the formal charge of each element in the atom
- Fri Oct 26, 2018 3:37 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ground State Electron Configurations
- Replies: 7
- Views: 690
Re: Ground State Electron Configurations
This is the closest noble gas, using this allows for the electron configuration to be shorter in length to write
- Fri Oct 26, 2018 3:36 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: 7th Edition Example 1B.5 (Page19)
- Replies: 2
- Views: 273
Re: 7th Edition Example 1B.5 (Page19)
The book is using the Heisenberg equation that is h with a dash over 2pi so that's why it's being multiplied by 2. I believe so?
- Sun Oct 21, 2018 10:35 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Quantum numbers
- Replies: 5
- Views: 592
Re: Quantum numbers
Yup! It's 4f because n=4 and l=3 which refers to the f block
- Thu Oct 18, 2018 1:31 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Homework 1E.13 Silver
- Replies: 2
- Views: 149
Re: Homework 1E.13 Silver
It's because you want to complete the 4d orbital before moving onto the 5s orbital. A full 4d orbital contains 10 electrons.
- Thu Oct 11, 2018 12:51 pm
- Forum: Limiting Reactant Calculations
- Topic: Percent Yield [ENDORSED]
- Replies: 13
- Views: 2918
Re: Percent Yield [ENDORSED]
Actual Yield is the value the problem should give you. It's the amount actually produced in the experiment. Theoretical yield is the amount you should expect to produce while using information from the balanced equation and the starting amount of the reactant.
- Thu Oct 11, 2018 11:16 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Naming Simple Coumpounds
- Replies: 2
- Views: 560
Re: Naming Simple Coumpounds
I believe we don't need to know how to name compounds on the first test. However, we will eventually need to know them. I think the best way to learn them is just memorize them, make flashcards on quizlet. My TA said eventually, after doing a lot of practice problems,we'll start memorizing the names...
- Wed Oct 10, 2018 6:18 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Spectral Line Diagram
- Replies: 1
- Views: 253
Re: Spectral Line Diagram
Spectral Line Diagrams are mainly used to identify molecules or atoms from their exact, unique placement of their particular spectral line. It's another way to analyze frequencies in addition to the electromagnetic spectrum.
- Mon Oct 01, 2018 9:08 pm
- Forum: General Science Questions
- Topic: Periodic Table
- Replies: 16
- Views: 1698
Re: Periodic Table
I tend to just use the whole number listed on the periodic table to make sure my answers are exact as possible, but if it's a super long number, I usually stop after 3 decimal places
- Mon Oct 01, 2018 11:50 am
- Forum: SI Units, Unit Conversions
- Topic: Unit "t"
- Replies: 2
- Views: 211
Re: Unit "t"
The "t" refers to the unit. In this case, it means metric ton (aka 1000 kg)
- Mon Oct 01, 2018 11:49 am
- Forum: Significant Figures
- Topic: Significant Figures
- Replies: 10
- Views: 2890
Re: Significant Figures
I tend to use exact calculations throughout the problems ensuring there are no rounding errors by the end. Once I get my answer, then I take significant figures into consideration. I find this provides the most accurate answer.
- Mon Oct 01, 2018 11:37 am
- Forum: SI Units, Unit Conversions
- Topic: Grams/mole
- Replies: 12
- Views: 1215
Re: Grams/mole
Yes these two notations mean the same thing. I believe it is a personal preference for which version to use. In some cases, it might be easier to type one out than the other. The negative 1 in the numerator means it will move to the denominator.