## Search found 50 matches

Sun Mar 18, 2018 6:23 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Replies: 4
Views: 380

Sun Mar 18, 2018 6:23 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Number 5
Replies: 2
Views: 292

### Re: Midterm Number 5

Okay thank you ! I think you're right.
Sat Mar 17, 2018 3:16 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Number 5
Replies: 2
Views: 292

### Midterm Number 5

Hi guys, for the second step in the fifth question on the midterm, it says that the system returns to the original internal energy. How do we know that the original internal energy is positive 158 joules? I understand how to solve for -158 in part a but i don't know how from -158 we get a positive v...
Sun Mar 11, 2018 8:37 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Dimerization
Replies: 2
Views: 143

### Re: Dimerization

Dimerization is when two molecules of the same element react with each other !

A + A --> A2
Sun Mar 11, 2018 8:34 pm
Forum: Reaction Mechanisms, Reaction Profiles
Replies: 2
Views: 206

Sun Mar 11, 2018 8:33 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Heterogenous vs homogenous
Replies: 2
Views: 201

### Re: Heterogenous vs homogenous

Typical reaction examples with a heterogeneous catalyst involve a solid catalyst with the reactants as either liquids or gases. Typically everything will be present as a gas if there is a homogeneous catalyst.
Sun Mar 04, 2018 7:49 pm
Forum: First Order Reactions
Topic: half life
Replies: 2
Views: 189

### Re: half life

I believe that for orders that we don't need to use the initial concentration for, half life is an intensive property.
Sun Mar 04, 2018 7:45 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: When forming rate laws do we include solids and liquids?
Replies: 3
Views: 2710

### Re: When forming rate laws do we include solids and liquids?

The concentration of solids and liquids does not affect the reactant amount at equilibrium so they are disregarded.
Sun Mar 04, 2018 7:43 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: kinetics an thermodynamics
Replies: 3
Views: 251

### Re: kinetics an thermodynamics

I think that we should know the conceptual relation between thermodynamics and kinetics, however, in the next chapter text there won't be any mathematical questions tying the two together. Kinetics describes the rates of chemical reactions while thermodynamics studies how different forms of energy a...
Sat Feb 24, 2018 5:21 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: What other elements could be used besides Pt?
Replies: 5
Views: 371

### Re: What other elements could be used besides Pt?

I believe Pt is the most common metal to be used.
Sat Feb 24, 2018 5:16 pm
Forum: Balancing Redox Reactions
Topic: 14.1 D
Replies: 3
Views: 253

### Re: 14.1 D

Before adding half reactions in order to get a final reaction, you have to make sure that there is the same amount of electrons in each half reaction that are being either gained or lost. In order to do that you may have to multiply a half reaction by a certain number, which was done here to get tho...
Sat Feb 24, 2018 5:10 pm
Forum: Balancing Redox Reactions
Topic: Identifying Oxi/Red Agents [ENDORSED]
Replies: 6
Views: 493

### Re: Identifying Oxi/Red Agents[ENDORSED]

I have the same question. Wouldn't the S be oxidized because it is the only element of the compound that is losing electrons?
Sat Feb 24, 2018 5:07 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: kinetics
Replies: 5
Views: 433

### Re: kinetics

Kinetics is related to reactivity and thermodynamics is related to stability!
Mon Feb 19, 2018 2:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cell
Replies: 3
Views: 220

### Re: Galvanic Cell

I think you should indicate there is a salt bridge and also the direction that the electrons are flowing in.
Mon Feb 19, 2018 2:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Number 14.35 vs. Number 14.37
Replies: 1
Views: 135

### Number 14.35 vs. Number 14.37

Hey guys, I generally do not understand when to flip the sign of the E value of an anode when solving for the Ecell and when not to. In question 35 it does flip the sign of the anode value and in number 37 it doesn't. Can anyone explain why?
Sat Feb 10, 2018 3:06 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Evaluation 9.3A
Replies: 2
Views: 240

### Re: Evaluation 9.3A

When something is compressed isothermally, you use the equation qrev/T!
Sat Feb 10, 2018 2:53 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Problem 9.75
Replies: 1
Views: 200

### Problem 9.75

Can someone help me understand for this problem how we know that the cis compound will have twelve different orientations and that the trans compound will only have three? Thanks!
Mon Feb 05, 2018 2:03 pm
Forum: Balancing Redox Reactions
Topic: Redox Reactions Given? [ENDORSED]
Replies: 2
Views: 254

### Re: Redox Reactions Given?[ENDORSED]

I believe that when given a chemical formula, we are expected to determine which elements are being oxidized or reduced, and subsequently write out their half reactions.
Mon Jan 29, 2018 10:14 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Internal Energy
Replies: 2
Views: 231

### Re: Internal Energy

Work calculations will be on the second test.
Mon Jan 29, 2018 10:13 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Positional disorder?
Replies: 2
Views: 143

### Re: Positional disorder?

They are essentially the same thing !
Mon Jan 29, 2018 10:12 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Degeneracy and Entropy
Replies: 3
Views: 287

### Re: Degeneracy and Entropy

Degeneracy is the different number of ways that energy can exist. There is a direct relationship between entropy and the degree of degeneracy, meaning that if there is a high degree of degeneracy, there will be more entropy because there are more configurations of energy to be in.
Sun Jan 28, 2018 6:25 pm
Forum: Calculating Work of Expansion
Topic: Thermodynamics for W
Replies: 3
Views: 346

### Re: Thermodynamics for W

You use that equation when pressure is not constant. -PdeltaV is used when pressure is constant.
Sun Jan 28, 2018 6:21 pm
Forum: Calculating Work of Expansion
Topic: work done on and by the system
Replies: 12
Views: 725

### Re: work done on and by the system

When work is being done by the system, w will be positive. When work is being done on the system, w will be negative.
Sun Jan 28, 2018 6:18 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Chapter 9 help
Replies: 3
Views: 261

### Re: Chapter 9 help

Fri Jan 19, 2018 8:10 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Thermodynamic vocabulary
Replies: 3
Views: 476

### Re: Thermodynamic vocabulary

Isothermal just means constant temperature ! The temperature inside a system can be the same as its surroundings without it being necessary for the system to be closed.
Fri Jan 19, 2018 8:04 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Replies: 3
Views: 272

Convection is the transfer of energy by movement of the medium present while radiation is transfer of energy through thermal radiation. Radiation does not require a medium.
Fri Jan 19, 2018 8:01 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Energy and matter?
Replies: 6
Views: 387

### Re: Energy and matter?

Yes they are taken into account for definition purposes however they are not both transferred in each case.
Fri Jan 12, 2018 2:27 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: tables in chapter 8
Replies: 5
Views: 265

### Re: tables in chapter 8

He will provide the information needed, such as the bond enthalpies when calculating delta H.
Fri Jan 12, 2018 2:26 pm
Forum: Administrative Questions and Class Announcements
Topic: Textbook Question
Replies: 1
Views: 161

### Re: Textbook Question

In 14A with Lavelle we covered the fundamentals, chapter one - four, part of seventeen, eleven and some of twelve.
Fri Jan 12, 2018 2:23 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 8.3
Replies: 2
Views: 136

### Question 8.3

hey guys !

for question 8.3, how do we know that delta V is pi*r^2*d? is it just because we're assuming the bicycle pump is a cylinder ?
Fri Dec 08, 2017 6:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.9
Replies: 2
Views: 258

### Re: 11.9

I believe that it is just asking you to find coefficients that aren't multiples of smaller numbers.
Fri Dec 08, 2017 12:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: T-shaped and Trigonal Pyramidal
Replies: 6
Views: 472

### Re: T-shaped and Trigonal Pyramidal

T shaped have two lone pairs and trigonal pyramidal have one.
Sun Dec 03, 2017 4:17 pm
Forum: Coordinate Covalent Bonds
Topic: Monodentate, Tridentate
Replies: 1
Views: 566

### Monodentate, Tridentate

I understand the definition of the term monodentate or tridentate but im not really sure how to classify which one applies to a compound when given its name. Could someone help me with the process of figuring that out?
Sun Dec 03, 2017 4:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Pi and sigma bonds [ENDORSED]
Replies: 7
Views: 441

### Re: Pi and sigma bonds[ENDORSED]

I think the most important thing to know about pi and sigma bonds is that a single bond is a sigma bond and a double bond is a sigma and a pi bond. Pi bonds don't allow rotation.
Sun Nov 26, 2017 11:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.9 Problem
Replies: 4
Views: 345

### Re: 4.9 Problem

It is T shaped because the lone pairs are not taken into account when naming. That means there are three attached atoms.
Sun Nov 26, 2017 11:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Molecular Shape
Replies: 3
Views: 209

### Determining Molecular Shape

Hey guys ! I know that in order to find the molecular shape, you have to draw the lewis structure first, but what if there are different resonance structures? How do you know which lewis structure to use for naming?
Fri Nov 17, 2017 8:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Exceptions to the Octet Rule
Replies: 4
Views: 367

### Re: Exceptions to the Octet Rule

The elements that can exceed the octet rule and have more than eight electrons are those who have a quantum number of 3 or above!
Fri Nov 17, 2017 8:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Chapter 4
Replies: 3
Views: 293

### Re: Chapter 4

Yes we've finished chapter four !
Sun Nov 12, 2017 8:50 pm
Forum: Lewis Structures
Topic: Bonding
Replies: 3
Views: 305

### Re: Bonding

Quadruple bonds usually don't occur because of the octet rule as well. The octet rule would be fulfilled for an element in an ion if there were four bonds which means no other element could be bonded to it. It also would not contribute to a plausible shape for the ion.
Sun Nov 12, 2017 8:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Resonance
Replies: 3
Views: 257

### Re: Resonance

Resonance does not influence shape. What configuration to use is determined by using formal charges. The sum of all the formal charges should equate the charge of the ion, or at least be close to it.
Fri Nov 03, 2017 6:05 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 2
Views: 235

### Re: Orbitals

I agree with Ryan. Just in case, I would specify the subshell.
Fri Nov 03, 2017 6:00 pm
Forum: *Shrodinger Equation
Topic: What does this even mean?
Replies: 4
Views: 590

### Re: What does this even mean?

Solving Schrodinger's equation helps you find the wavefunctions and energy levels of an electron in an atom. The quantized energies of the system, once calculated, helps you find out other properties of the atom such as its shape and orientation.
Fri Oct 27, 2017 5:42 pm
Forum: Ionic & Covalent Bonds
Topic: Polyatomic Lewis Structures
Replies: 5
Views: 794

### Re: Polyatomic Lewis Structures

The polyatomic ions aren't their usual, balanced charge so when something is 3+, it means that it has three less electrons that it would normally. Anions gain electrons and Cations lose them. When you draw lewis structures, people usually write the charge in the upper right to differentiate !
Fri Oct 27, 2017 5:35 pm
Forum: Lewis Structures
Topic: Double or single bonds
Replies: 4
Views: 265

### Re: Double or single bonds

When drawing a Lewis structure, you have to count the valence electrons of every element and multiply that number by the amount of molecules of that element if that is needed. After you know how many total electrons there are, you can start drawing the structure with, generally, the least electroneg...
Fri Oct 20, 2017 4:44 pm
Forum: DeBroglie Equation
Topic: Conceptual Wavelength measurement
Replies: 3
Views: 306

### Re: Conceptual Wavelength measurement

I believe that Plank's constant might be the limit.
Fri Oct 20, 2017 4:39 pm
Forum: Photoelectric Effect
Topic: Energy emitted from an Electron [ENDORSED]
Replies: 4
Views: 458

### Re: Energy emitted from an Electron[ENDORSED]

When using the Rydberg equation in the form of r(1/N1^2 - 1/N2^2), N1 is always the lower energy level! Even if the electron is jumping from a high energy level to a lower one.
Thu Oct 12, 2017 6:10 pm
Forum: Properties of Electrons
Topic: Wave Properties of Electrons
Replies: 3
Views: 361

### Re: Wave Properties of Electrons

If an electron didn't have wavelike properties, in the photoelectric experiment, the electron would go through the small hole and travel straight. However, because the electron has wavelike properties, it hit several different locations. An example of wavelike properties would be fields oscillating ...
Thu Oct 12, 2017 6:08 pm
Forum: Properties of Electrons
Topic: Rydberg's Equation [ENDORSED]
Replies: 3
Views: 282

### Rydberg's Equation[ENDORSED]

If an electron, for example, is jumping from n=4 to n=2, do you still use n=2 as the value of n1 in rydberg's equation?
Thu Oct 05, 2017 7:18 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E.27 [ENDORSED]
Replies: 2
Views: 344

### Re: E.27[ENDORSED]

I did this question by calculating the molar mass of water, and then converting that to molecules using a conversion equation with avogadro's number.
Thu Oct 05, 2017 7:14 pm
Forum: Limiting Reactant Calculations