Search found 73 matches

by Tim Foster 2A
Sat Mar 17, 2018 12:18 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Chapter 14 # 107
Replies: 1
Views: 167

Chapter 14 # 107

Why do we use E(naught)=lnK for this problem, instead of E=E(naught)-lnQ in which Enaught would be zero (PH7)
I paraphrased the equations because I'm lazy
by Tim Foster 2A
Wed Mar 14, 2018 4:01 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Homework 8.117 [ENDORSED]
Replies: 2
Views: 94

Re: Homework 8.117 [ENDORSED]

Why dont you need to balance the equation before you begin solving it?
by Tim Foster 2A
Wed Mar 14, 2018 2:44 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Homework 8.117 [ENDORSED]
Replies: 2
Views: 94

Homework 8.117 [ENDORSED]

The question states that CH4 + H20 -> CO2 + 3H2, and I need to find the work done by this reaction. After balancing the equation, I found the change in N to be 1/2 with respect to 1 mol of H2 (1/4+4/4 - 2/4 -1/4), and I know that work= -nRT. What do I use for T? When I use 298K I get an incorrect an...
by Tim Foster 2A
Mon Mar 12, 2018 1:18 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7337
Views: 787764

Re: Post All Chemistry Jokes Here

What do you call the guest registry at the Annual Bovine Convention of Cows in Chemistry?

A Cattle-List!
moooo
by Tim Foster 2A
Thu Mar 08, 2018 6:44 pm
Forum: First Order Reactions
Topic: pseudoreactions [ENDORSED]
Replies: 2
Views: 98

pseudoreactions [ENDORSED]

Let's say we had a second order rate law that was equal to k[A][B]. To render this a pseudo-first order reaction, one could ensure that the concentration of A was so high relative to the concentration of B (lets say .85M and .003M, respectively) that the concentration of A effectively stayed constan...
by Tim Foster 2A
Mon Mar 05, 2018 3:04 pm
Forum: Balancing Redox Reactions
Topic: Test 2 Q8
Replies: 2
Views: 81

Test 2 Q8

when finding Q from the half reactions
Ag(s) + I-(aq) -> AgI(s) + e- E(anode)=-0.15V
AgCl(s) + e- -> Ag(s) + Cl- (aq) E(cathode) = 0.22V

How do you identify Cl- and I- as products or reactants?
by Tim Foster 2A
Mon Mar 05, 2018 2:48 pm
Forum: Balancing Redox Reactions
Topic: Test 2 Q6
Replies: 4
Views: 125

Test 2 Q6

How do you identify the oxidizing and reducing agents for the redox couple
O3/O2 and OH- and O3, H+/02 ?
by Tim Foster 2A
Mon Mar 05, 2018 2:43 pm
Forum: Balancing Redox Reactions
Topic: Reducing power
Replies: 2
Views: 73

Reducing power

Does Br2 have a weaker reducing power compared to I2? Does this also correlate to a stronger oxidizing power for Br2 in comparison to I2?
by Tim Foster 2A
Fri Feb 23, 2018 10:58 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.41b
Replies: 1
Views: 84

Re: 14.41b

Hey! To find the standard cell potential, we extrapolate oxidation and reduction half reactions from the cell diagram, from the left and right sides, respectively. Once we have these half rxns, we can use our handy dandy chart in Appendix 2B to search for standard reduction potentials (subtracting t...
by Tim Foster 2A
Thu Feb 22, 2018 5:51 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram
Replies: 4
Views: 133

Cell diagram

When dealing with two compounds that are in different phases, how do you know which to list first in the cell diagram? For instance, if the two compounds on the reduction side of my diagram are Cl2(g) and Cl-, which do I put first?
by Tim Foster 2A
Thu Feb 22, 2018 5:42 pm
Forum: Balancing Redox Reactions
Topic: Cell Diagram [ENDORSED]
Replies: 7
Views: 187

Cell Diagram [ENDORSED]

When writing a cell diagram, why are I- ions and I2(s) separated on the oxidation side?
by Tim Foster 2A
Thu Feb 22, 2018 2:53 pm
Forum: Balancing Redox Reactions
Topic: H+ or H3O+ to balance half-rxns in acidic conditions?
Replies: 1
Views: 68

H+ or H3O+ to balance half-rxns in acidic conditions?

Should we use H+ or H3O+ to balance half-rxns in acidic conditions?
by Tim Foster 2A
Thu Feb 22, 2018 2:52 pm
Forum: Balancing Redox Reactions
Topic: Textbook 14.1
Replies: 3
Views: 121

Textbook 14.1

In 14.1 part c, why does the answer in the textbook include 14 H- in the reduction half reaction instead of 14H+?
by Tim Foster 2A
Wed Feb 14, 2018 1:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Homework Problem 9.81
Replies: 1
Views: 95

Re: Homework Problem 9.81

Hey Lily Fe3O4(s) + O2(g) = Fe2O3(s) This is the unbalanced equation for the oxidation of Magnetite to Hematite. If we balance the equation, we get 4Fe3O4(s) + O2(g) = 6Fe2O3(s). For your method to work, you would need to compare the deltaG of formation of six moles of Hematite to 4 moles of Magneti...
by Tim Foster 2A
Wed Feb 14, 2018 11:37 am
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: Boron Triflouride Degeneracy [ENDORSED]
Replies: 1
Views: 192

Boron Triflouride Degeneracy [ENDORSED]

Does Boron Triflouride have a degeneracy of one? Further implying that at T=0, it has no entropy?
by Tim Foster 2A
Tue Feb 13, 2018 3:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.15
Replies: 8
Views: 301

Re: 11.15

zanekoch1A wrote:I'm not sure what I am doing wrong but I keep getting an answer around 1.5kj. I am using in the Gnot part of the equation a T of 273 and a k of 6.8 and and in the G side a T of 1200 and ln(.13/.98). What am I doing wrong?


Hey Zane, I think your natural log should be of (.98)^2/(.13)
by Tim Foster 2A
Tue Feb 13, 2018 2:55 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal Process
Replies: 1
Views: 95

Re: Isothermal Process

The equation q=mCdeltaT is somewhat useless for isothermal processes because it has to do specifically with heat capacities. It's not that a substance that doesn't change in temperature has no heat capacity at all, its just that its impossible to tell what that heat capacity is when the temperature ...
by Tim Foster 2A
Tue Feb 13, 2018 2:29 pm
Forum: Calculating Work of Expansion
Topic: 8.93 Expansion?
Replies: 4
Views: 188

Re: 8.93 Expansion?

1) I'm not sure about this either, I know that combustion can produce water vapor when it is carried out at temperatures above 100 C, but this reaction appears to be at 25 C. 2) However, I do know that if you consider water vapor as a product instead of liquid water, you will find that the system lo...
by Tim Foster 2A
Tue Feb 13, 2018 1:41 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Textbook 9.67
Replies: 1
Views: 61

Textbook 9.67

This problem wants us to find the range over which each reaction will be spontaneous and lists a few reactions. My calculations are all slightly off for some reason; am I correct in that to solve this problem you need to use the difference in enthalpy and entropy of the products and reactants to fin...
by Tim Foster 2A
Mon Feb 12, 2018 12:50 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp vs Cv
Replies: 1
Views: 79

Re: Cp vs Cv

I believe constant pressure only dictates that the pressure is kept constant, not that volume and/or work are kept constant.
by Tim Foster 2A
Mon Feb 12, 2018 12:48 pm
Forum: Calculating Work of Expansion
Topic: 8.93 Expansion?
Replies: 4
Views: 188

Re: 8.93 Expansion?

If you write your equation with water as a gas instead of a liquid, you will find the change in moles to be +3 and you will get -3.71 KJ as the change in energy of the system due to work. If a system is losing energy due to work, that means it is performing work. Thus the work done against the atmos...
by Tim Foster 2A
Thu Feb 08, 2018 10:05 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Calculating entropy of vaporization
Replies: 1
Views: 73

Calculating entropy of vaporization

When finding entropy of vaporization from a temperature that is not the boiling point, we include the change in entropy that arises when you cool the vapor back down to original temperature. Why is this last value calculated using the heat capacity for the gaseous state? Why does cooling down a vapo...
by Tim Foster 2A
Thu Feb 08, 2018 9:59 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Finding entropy of vaporization from temperatures NOT = to boiling point [ENDORSED]
Replies: 3
Views: 124

Finding entropy of vaporization from temperatures NOT = to boiling point [ENDORSED]

When finding the standard entropy of vaporization of water at 85 C, why do we cool the vapor back down from 100 C? I get that entropy is a state function, but enthalpy is also a state function and when finding the enthalpy of vaporization of water at 85 C, we would simply add the Hvap of water to 4....
by Tim Foster 2A
Thu Feb 08, 2018 3:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Textbook 8.89
Replies: 1
Views: 77

Textbook 8.89

How does one solve this problem? Is there a way to figure out the melting point of iodine or is that not needed at all?
by Tim Foster 2A
Tue Feb 06, 2018 7:34 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: How cold is that iced tea tho
Replies: 1
Views: 76

How cold is that iced tea tho

If a 50.0 g ice cube is added to 250 ml of tea at 20.0 degrees celsius, what is the final temperature at thermal equilibrium?
by Tim Foster 2A
Sat Feb 03, 2018 7:48 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G [ENDORSED]
Replies: 4
Views: 74

Re: Delta G [ENDORSED]

Hey Emma, Delta G is not always negative, it is a measure of the energy available to do work in a system. For example, because the hydrolysis of ATP allows your cells to harness the energy from that spontaneous reaction and do work with it, it has a negative Delta G. A reaction that requires an net ...
by Tim Foster 2A
Sat Feb 03, 2018 7:42 pm
Forum: Phase Changes & Related Calculations
Topic: Degeneracy
Replies: 4
Views: 160

Degeneracy

What is degeneracy and how can we use it?
by Tim Foster 2A
Wed Jan 24, 2018 5:45 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Hmwk Q 8.31
Replies: 2
Views: 133

Re: Hmwk Q 8.31

Page 281 in the textbook tells us that
C=3/2RT for monatomic gases at constant volume, while C=5/2RT for monatomic gases at constant pressure.
by Tim Foster 2A
Wed Jan 24, 2018 5:40 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question regarding 8.39 homework question
Replies: 5
Views: 172

Re: Question regarding 8.39 homework question

Hey Michelle, You need to use the specific heat capacity of liquid water because once the ice melts, all heat being transferred will be subject to the properties and heat capacity of liquid water. This problem can be essentially be split into two parts; the first of which you use the heat capacity o...
by Tim Foster 2A
Wed Jan 24, 2018 5:34 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Chapter 8.7 concepts and math question
Replies: 1
Views: 136

Re: Chapter 8.7 concepts and math question

U=3/2RT for monatomic gases at constant volume, while U=5/2RT for monatomic gases at constant pressure. Rotational and translational contributions come into play when dealing with diatomic or polyatomic gases, for which we observe LINEAR MOLECULES- U= 5/2R, 7/2R (Constant volume, constant pressure) ...
by Tim Foster 2A
Wed Jan 24, 2018 5:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework Problem 8.67
Replies: 3
Views: 133

Homework Problem 8.67

8.67) Use the information in Tables 8.3, 8.6, 8.7 to estimate the enthalpy of formation of each of the following compounds in the liquid state. The standard enthalpy of sublimation of carbon is +717 kj/mol. b)CH3OH c)C6H6 (without resonance) d)C6H6 (with resonance) For b), I created the formation re...
by Tim Foster 2A
Wed Jan 24, 2018 4:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: homework 8.67
Replies: 3
Views: 166

Re: homework 8.67

Thanks Remi, one more question: Do two gases always form another gas when they react? More specifically, how did you know that H2 gas and O2 gas reacted to form H20 in its gaseous form?
by Tim Foster 2A
Wed Jan 24, 2018 3:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: homework 8.67
Replies: 3
Views: 166

homework 8.67

8.67) Use the information in Tables 8.3, 8.6, 8.7 to estimate the enthalpy of formation of each of the following compounds in the liquid state. The standard enthalpy of sublimation of carbon is +717 kj/mol. a)H20 b)CH3OH c)C6H6 (without resonance) d)C6H6 (with resonance) How do you find the enthalpi...
by Tim Foster 2A
Thu Jan 18, 2018 5:35 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.51 Sig Figs, Sign [ENDORSED]
Replies: 3
Views: 293

Re: 8.51 Sig Figs, Sign [ENDORSED]

Why is the answer to this problem written as "23.9 KJ/L x 10^3" and not "2.39 KJ/L x 10^4"?
by Tim Foster 2A
Tue Jan 16, 2018 3:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Finding change in enthalpy of a rxn
Replies: 3
Views: 148

Finding change in enthalpy of a rxn

When calculating the change in enthalpy of a rxn by subtracting the standard enthalpy of formation of the reactants from the standard enthalpy of the products, how do you find the enthalpies of formation for individual products/reactants? Is there a way to calculate this or is there a chart somewher...
by Tim Foster 2A
Mon Jan 15, 2018 1:37 pm
Forum: Phase Changes & Related Calculations
Topic: Types of Systems
Replies: 10
Views: 302

Re: Types of Systems

An isolated system has no interaction with its surroundings whatsoever, while a closed system has a fixed amount of matter, but can exchange energy with its surroundings. A good example of a closed system is something like an ice pack, and a good example of an isolated system is something sealed off...
by Tim Foster 2A
Sat Jan 13, 2018 10:03 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Bomb Calorimetry
Replies: 4
Views: 172

Re: Bomb Calorimetry

The main difference between a true bomb calorimeter and the coffee cup calorimeter is that the bomb is much more sophisticated and thus gives more accurate calculations. Other than that, the function of each is the same. As far as how it works, I think all we should know for this course is that a bo...
by Tim Foster 2A
Sat Jan 13, 2018 9:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: The 3 Methods for Calculating the Enthalpy of a Reaction
Replies: 4
Views: 164

Re: The 3 Methods for Calculating the Enthalpy of a Reaction

Hey! I know this much, rxn enthalpy is heat given off or taken up for the rxn, or just the enthalpy difference between the reactants and products. The enthalpy of formation of a compound is the enthalpy change between the reactants in their standard state and the product.
Hope that helps
by Tim Foster 2A
Mon Jan 08, 2018 1:26 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy and Temperature [ENDORSED]
Replies: 4
Views: 184

Enthalpy and Temperature [ENDORSED]

Can enthalpy and temperature be related?
by Tim Foster 2A
Sat Dec 09, 2017 9:53 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7337
Views: 787764

Re: Post All Chemistry Jokes Here

Which Nicki Minaj song is the best to listen to while studying Chapter 12?
Superbass!
by Tim Foster 2A
Fri Dec 08, 2017 9:58 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 11.77 textbook problem
Replies: 2
Views: 105

11.77 textbook problem

Why does increasing the temperature of the rxn X2(g)<--->2X(g), where X is a halogen, favor the products? How should we know that is endothermic in the forward direction?
by Tim Foster 2A
Thu Dec 07, 2017 9:26 am
Forum: Bronsted Acids & Bases
Topic: Autoprotolysis
Replies: 1
Views: 102

Autoprotolysis

What is this, and why does it lead to hydronium/hydroxide ions moving through water much faster than other kinds of ions?
by Tim Foster 2A
Tue Dec 05, 2017 5:45 pm
Forum: Bronsted Acids & Bases
Topic: Net ionic equations (12.9)
Replies: 1
Views: 118

Net ionic equations (12.9)

When writing net ionic equations, do solid (s) or liquid (l) compounds get split into ions?
If not, why is the Bronsted Acid in the equation NH4I (s) + H20 (l) ---> NH3 (aq) + H3O+ (aq) + I- (aq)
considered to be NH4+, instead of NH4I
by Tim Foster 2A
Mon Dec 04, 2017 5:18 pm
Forum: Administrative Questions and Class Announcements
Topic: What is a passing grade? [ENDORSED]
Replies: 4
Views: 395

Re: What is a passing grade? [ENDORSED]

The syllabus says that final grades will not be assigned until the class average score out of 500 is known, which makes me think (hope) that perhaps our grade will be out of slightly less than 500, but I am not sure
by Tim Foster 2A
Mon Dec 04, 2017 5:14 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Neutralization reactions
Replies: 4
Views: 171

Re: Neutralization reactions

How do you know that there are two hydroxide ions in Zinc Hydroxide?
by Tim Foster 2A
Mon Dec 04, 2017 5:11 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Proton Transfer Reactions
Replies: 2
Views: 130

Proton Transfer Reactions

When writing the chemical equation for the proton transfer reaction of NaC6H5O, I realized that my answer (NaC6H5O + H2O --> NaOH + C6H5OH)
differed from the textbook solution in that the solution did not include sodium at all (C6H5O- + H20 --> C6H5OH + OH-). Why is sodium left out?
by Tim Foster 2A
Mon Dec 04, 2017 4:33 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Zinc Nitrate
Replies: 2
Views: 132

Zinc Nitrate

How does one draw the lewis structure of this compound?
by Tim Foster 2A
Mon Dec 04, 2017 4:29 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Neutralization reactions
Replies: 4
Views: 171

Neutralization reactions

What would a neutralization reaction that resulted in the formation of zinc nitrite look like?
by Tim Foster 2A
Mon Dec 04, 2017 9:54 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: H20 Dentate [ENDORSED]
Replies: 2
Views: 128

H20 Dentate [ENDORSED]

If H20 has two atoms with lone pairs on them, why is it monodentate and not bidentate?
by Tim Foster 2A
Mon Nov 27, 2017 8:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.1 Homework
Replies: 2
Views: 132

11.1 Homework

"If one starts with a higher pressure of reactant, the equilibrium constant will be larger."
Why is this false? I thought K=[Products]/[Reactants]
by Tim Foster 2A
Mon Nov 27, 2017 3:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: CH2Cl2
Replies: 1
Views: 124

CH2Cl2

Why is this molecule polar? What's stopping the chlorines from being on opposite sides of the carbon, and their dipoles canceling? Why are they adjacent to each other instead?
by Tim Foster 2A
Mon Nov 27, 2017 3:06 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw
Replies: 2
Views: 142

Seesaw

What are the different bond angles in a seesaw arrangement of atoms in a molecule?
by Tim Foster 2A
Mon Nov 27, 2017 11:16 am
Forum: Determining Molecular Shape (VSEPR)
Topic: T_shaped Molecules
Replies: 2
Views: 147

T_shaped Molecules

What's an example of a t-shaped molecules and how does this shape come to be? What stops the atoms attached to the central atom from getting as far away from each other as possible and forming a trigonal planar shape?
by Tim Foster 2A
Mon Nov 27, 2017 11:10 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pair Effect on Bond Angles [ENDORSED]
Replies: 3
Views: 198

Re: Lone Pair Effect on Bond Angles [ENDORSED]

Hey! Not sure about calculating the exact measure of bond angles being influenced by a lone pair, I believe that's a little above this course's pay grade, but I do know that bond angles in a molecule adjacent to the bond angle containing the lone pair will be slightly smaller than they would have be...
by Tim Foster 2A
Tue Nov 21, 2017 6:41 pm
Forum: Naming
Topic: HCN
Replies: 2
Views: 122

HCN

How does one name this molecule?
by Tim Foster 2A
Tue Nov 21, 2017 5:47 pm
Forum: Hybridization
Topic: Significance of hybridization
Replies: 2
Views: 200

Re: Significance of hybridization

The necessity of the hybridization of orbitals can be traced back to Valence Bond theory, the theory that calculates covalent bonds angles and lengths. When we try to apply this theory to a compound like methane (CH4), it begins to fall apart. This is due to something called Electron Promotion, in w...
by Tim Foster 2A
Mon Nov 20, 2017 2:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reaction progress [ENDORSED]
Replies: 2
Views: 148

Reaction progress [ENDORSED]

How does one depict the progress of a reaction graphically?
by Tim Foster 2A
Mon Nov 20, 2017 2:14 pm
Forum: Ideal Gases
Topic: PV=nRT [ENDORSED]
Replies: 4
Views: 200

PV=nRT [ENDORSED]

What do all of the different variables in the ideal gas law above represent?
by Tim Foster 2A
Sat Nov 11, 2017 12:47 pm
Forum: Lewis Structures
Topic: HOCO [ENDORSED]
Replies: 3
Views: 210

HOCO [ENDORSED]

What does the correct lewis structure for this molecule look like?
by Tim Foster 2A
Wed Nov 08, 2017 2:08 pm
Forum: Empirical & Molecular Formulas
Topic: Fundamentals E9
Replies: 1
Views: 136

Fundamentals E9

The question asks how many atoms of oxygen are in 5.15 grams of epsom salt, or magnesium sulfate heptahydrate. Firstly, are we going to need to know nomenclature like this for the midterm? Secondly, I googled the formula and got MgSO4(7H20). I am unsure of whether or not this problem would like me t...
by Tim Foster 2A
Tue Nov 07, 2017 8:43 am
Forum: Ionic & Covalent Bonds
Topic: oxidation state
Replies: 3
Views: 202

oxidation state

What is an oxidation state, and how can chlorine have both positive and negative oxidation states?
by Tim Foster 2A
Mon Oct 30, 2017 9:35 pm
Forum: Electronegativity
Topic: ELECTRON AFFINITY
Replies: 7
Views: 495

ELECTRON AFFINITY

How are we supposed to know how electron affinity changes as you go down a group on the periodic table? I know that (generally) electron affinity increases from left to right across the table, but how should I know that Na has a lower EA than Li, for example?
by Tim Foster 2A
Sun Oct 29, 2017 10:50 pm
Forum: Resonance Structures
Topic: HOW [ENDORSED]
Replies: 1
Views: 147

HOW [ENDORSED]

How do we know what the most stable amount of double bonds is for a sulfur atom in a Sulfide molecule?
by Tim Foster 2A
Sun Oct 29, 2017 10:46 pm
Forum: Resonance Structures
Topic: Resonance Structures [ENDORSED]
Replies: 3
Views: 202

Resonance Structures [ENDORSED]

How do we draw a representation of a resonance structure? Is it just a combination of all possible configurations?
by Tim Foster 2A
Fri Oct 20, 2017 5:08 pm
Forum: Properties of Light
Topic: 1.43
Replies: 1
Views: 189

1.43

What is the minimum uncertainty in the speed of an electron confined to within a lead atom of diameter 350. pm?
by Tim Foster 2A
Fri Oct 20, 2017 5:05 pm
Forum: SI Units, Unit Conversions
Topic: Chemistry
Replies: 3
Views: 224

Chemistry

how do I convert cm-1 into meters? Thanks!
by Tim Foster 2A
Thu Oct 12, 2017 9:20 pm
Forum: Properties of Light
Topic: Question 1.33
Replies: 1
Views: 108

Question 1.33

Hey! I'm having trouble with part c of this problem. When I use the equation wavelength=c/frequency I get around 12 nm, but the back of the book says 8.8
by Tim Foster 2A
Thu Oct 12, 2017 2:18 pm
Forum: Properties of Light
Topic: 1.27
Replies: 1
Views: 135

Re: 1.27

Hey Irma! A key step of this problem is to find the energy created by one photon from this source of radiation, which we can do by using the formula E=hv, h being planck's constant (6.626x10^-34) and v being the frequency. In order to plug the frequency into the above equation we must use the formul...
by Tim Foster 2A
Tue Oct 10, 2017 2:49 pm
Forum: Properties of Light
Topic: Atomic Spectra
Replies: 1
Views: 147

Atomic Spectra

Using the formula
V=R(1/nsquared - 1/nsquared)
in atomic spectra problems, what does it mean when the initial n is greater than the final n (ex// n=1 transitioning to n=5) and you get a negative value for the frequency of the energy emitted?
by Tim Foster 2A
Tue Oct 10, 2017 2:37 pm
Forum: Properties of Light
Topic: Problem 1.4
Replies: 3
Views: 167

Problem 1.4

The problem asks which statement is true A) x-rays travel faster than infrared radiation B) the wavelength of visible radiation decreases as its color changes from blue to green C) the frequency of infrared radiation is half that of radio waves D) the frequency of infrared radiation is twice that of...
by Tim Foster 2A
Mon Oct 02, 2017 1:38 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Equations [ENDORSED]
Replies: 1
Views: 172

Balancing Chemical Equations [ENDORSED]

What are coefficients in chemical equations called?
by Tim Foster 2A
Mon Oct 02, 2017 1:37 pm
Forum: Limiting Reactant Calculations
Topic: % yield [ENDORSED]
Replies: 2
Views: 248

% yield [ENDORSED]

Hey, what is the difference between percent yield and theoretical yield?

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