Search found 77 matches
- Thu Mar 14, 2019 9:30 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius Equation Variations
- Replies: 1
- Views: 452
Re: Arrhenius Equation Variations
The equation ln(k 2 /k 1 )= Ea/R(1-T 1 -(1-T 2 ) is derived from the Arrhenius equation for two temperatures. ln k 2 = -Ea/RT 2 + ln A ln k 1 = -Ea/RT 1 + ln A By subtracting the two equations, you get ln k 2 - ln k 1 = -Ea/RT 2 + Ea/RT 1 Then you can factor out -Ea/R to get ln k 2 - ln k 1 = -Ea/R ...
- Wed Mar 13, 2019 10:03 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2, Question 6 part a
- Replies: 4
- Views: 463
Re: Test 2, Question 6 part a
The species with the greatest reducing power has the most negative value, so the answer is:
Pb < Cd < Mn
Pb < Cd < Mn
- Tue Mar 12, 2019 1:35 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2 #6 Ordering Reducing/Oxidizing Power
- Replies: 3
- Views: 513
Test 2 #6 Ordering Reducing/Oxidizing Power
Could someone let me know what they got for 6 a, b, and c for Test 3, and how they reasoned out the answers? a. In order of increasing reducing power going from their neutral to second oxidation state: Pb, Cd, Mn b. In order of increasing oxidation power going from their third oxidation state to neu...
- Thu Mar 07, 2019 8:04 pm
- Forum: General Rate Laws
- Topic: Average rate vs unique rate vs instantaneous rate
- Replies: 2
- Views: 372
Re: Average rate vs unique rate vs instantaneous rate
What would be the purpose of finding the average or instantaneous rate of a reaction?
- Thu Mar 07, 2019 6:23 pm
- Forum: General Rate Laws
- Topic: Order of a Reaction
- Replies: 3
- Views: 355
Re: Order of a Reaction
A reaction involving [A][B] is not necessarily a second order reaction since the rate of the reaction might not be dependent on the concentration of one of the reactants (such as when they're already in excess compared to the other reactant). The sum of the powers of the reactant concentrations have...
- Thu Mar 07, 2019 6:20 pm
- Forum: Zero Order Reactions
- Topic: plots
- Replies: 1
- Views: 263
Re: plots
In a zero-order reaction, concentration decreases over time (linear with slope -k). In a first-order reaction, ln/concentration decreases over time (linear with slope -k). In a second-order reaction, 1/concentration decreases over time (linear with slope k). https://chem.libretexts.org/@api/deki/fil...
- Mon Mar 04, 2019 9:03 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6th edition 14.47
- Replies: 4
- Views: 600
Re: 6th edition 14.47
I also was unsure about why they rounded to one sig fig. I tried it with the log equation instead of ln, and got 10^6 that way.
- Wed Feb 27, 2019 11:42 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: E cell
- Replies: 4
- Views: 624
Re: E cell
To find n, you can write out the two half-reactions for the cell reaction: Reduction: 6 Fe 3+ (aq) + 6 e- -> 6 Fe 2+ (aq) To balance the charges on both sides, 6 e- is added to the left side. Oxidation: 2 Cr 3+ (aq) + 7 H 2 O (l) -> Cr 2 O 7 2- (aq) + 14 H + The left side has a total charge of 6+ an...
- Wed Feb 27, 2019 10:32 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.1
- Replies: 1
- Views: 239
Re: 6L.1
n is the number of electrons transferred in the cell reaction, and you can calculate it by finding the half reactions and determining the number of electrons exchanged.
- Wed Feb 27, 2019 10:25 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Which Molar Ratio?
- Replies: 2
- Views: 316
Re: Which Molar Ratio?
The standard Gibbs free energy of a cell reaction is calculated with the formula:
delta G = -nFE, where n is the number of electrons transferred.
For the first reaction, determine the half reactions for the oxidation and reduction parts and balance them to find the number of electrons transferred.
delta G = -nFE, where n is the number of electrons transferred.
For the first reaction, determine the half reactions for the oxidation and reduction parts and balance them to find the number of electrons transferred.
- Wed Feb 20, 2019 9:28 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cells
- Replies: 7
- Views: 630
Re: Galvanic Cells
Could someone explain the purpose and importance of having a salt bridge between the galvanic cells?
- Wed Feb 20, 2019 6:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Midterm Q3D
- Replies: 1
- Views: 280
Re: Midterm Q3D
Acids and bases tend to be expressed as aqueous in solutions with water as a liquid. However, when they dissociate with water, the conjugate acid/base and the water that donates or accepts a proton are all considered aqueous in the solution.
- Wed Feb 20, 2019 6:10 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Midterm Question
- Replies: 5
- Views: 838
Re: Midterm Question
The question basically asks you what the value of the equilibrium constant (K) means. If it is significantly large (>10^3), then that means the reaction favors the right side of the equation, meaning that products are more stable than reactants. If it's significantly small, then the reactants are mo...
- Tue Feb 12, 2019 11:28 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: work
- Replies: 5
- Views: 504
Re: work
Work is being done on the system when w is positive, since the internal energy (U) of the system increases.
- Tue Feb 12, 2019 11:17 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Quiz 1 #5
- Replies: 7
- Views: 925
Re: Quiz 1 #5
oops didn't know there were different forms. The question asks for the pH of a .030M solution of sodium sorbate(C6H7O2), given that the pKa of sorbic acid(C6H8O2) is 4.74. The reaction is: C6H7O2+H2O<=>C6H8O2+OH Ka = 1.82*10^-5 Kb = 5.50*10^-10 x = [OH-] = 4.06*10^-6 pOH = 5.39 Therefore, pH = 14-5...
- Tue Feb 12, 2019 11:05 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Quiz 1 #5
- Replies: 7
- Views: 925
Re: Quiz 1 #5
If your question had a pKa value of 4.17 for 0.040M sodium ascorbate, the pH of the solution is 8.39.
- Tue Feb 12, 2019 10:58 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: 9.45 Sixth Edition
- Replies: 1
- Views: 294
Re: 9.45 Sixth Edition
The delta H of the system is equal to the negative delta H of the surroundings; the answer key basically just puts a negative sign before delta H of the system in the equations where you can also use delta H of the surroundings.
- Tue Feb 12, 2019 9:47 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Change and Temperature
- Replies: 3
- Views: 430
Re: Phase Change and Temperature
During a phase change, the energy is used to either form or break bonds, rather than increase the temperature of the substance by increasing its kinetic energy.
- Tue Feb 12, 2019 9:42 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Calculating entropy for a has given a temperature change
- Replies: 1
- Views: 226
Re: Calculating entropy for a has given a temperature change
I'm pretty sure your first equation should be ln(V2/V1).
Use delta S = n*R*ln(V2/V1) for an isothermal process, and delta S = n*Cv (or Cp)*ln(T2/T1) when there is a temperature change.
Use delta S = n*R*ln(V2/V1) for an isothermal process, and delta S = n*Cv (or Cp)*ln(T2/T1) when there is a temperature change.
- Mon Feb 04, 2019 7:47 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Residual Entropy
- Replies: 3
- Views: 325
Re: Residual Entropy
Residual entropy just means the randomness of the system based on the position of the elements/molecules inside of it, when there is no movement (temperature is K=0).
- Mon Feb 04, 2019 7:27 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: molecules
- Replies: 1
- Views: 278
Re: molecules
Gas molecules tend to occupy a larger space and move freely at higher speeds than liquids and solids, meaning that there is a greater number of possible states (position) that they can occupy compared to liquids and solids. This ultimately means that gases tend to have greater entropy than liquids, ...
- Mon Feb 04, 2019 7:26 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: positional (residual) entropy
- Replies: 2
- Views: 448
Re: positional (residual) entropy
Normal entropy refers to the randomness exhibited by the elements of a system due to their constant movement (like molecules in liquid). Residual entropy is entropy at absolute zero, meaning that the elements are no longer moving. Even though there is no movement, there is still residual entropy due...
- Tue Jan 29, 2019 1:07 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Cp vs. Csp
- Replies: 2
- Views: 481
Re: Cp vs. Csp
Cp refers to the heat required to raise the temperature of one mole gas by 1 degree C at constant pressure, and Csp refers to the heat required to raise the temperature of one gram gas by 1 degree C at constant pressure.
- Tue Jan 29, 2019 12:59 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 8.99 in Sixth Edition
- Replies: 1
- Views: 192
Re: 8.99 in Sixth Edition
To find out the final temperature, you should start out by writing the chemical equation and figuring out which is the limiting reactant (that's what the molarity values are for). After finding out the limiting reactant, you can then find the enthalpy of reaction (delta H) and multiply that by the n...
- Mon Jan 28, 2019 12:29 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Question 12.69 Part B (Sixth Edition)
- Replies: 1
- Views: 448
Re: Question 12.69 Part B (Sixth Edition)
Metal cations in water will form tetra- or hexa- aqua complexes in water. The Al cation in water will form Al(H 2 O) 6 3+ , which will act as a weak acid with Ka = 1.4 x 10^-5. (This is all in 12.13 in the textbook). So the equation is: Al(H 2 O) 6 3+ (aq) + H 2 O (l) -><- H 3 O + (aq) + Al(H 2 O) 5...
- Thu Jan 24, 2019 3:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5% Rule and % Deprotonation
- Replies: 3
- Views: 378
Re: 5% Rule and % Deprotonation
Yes, if the percent deprotonation is less than 5%, then you are safe to approximate by assuming that a change of 0.1-x, for example, is 0.1.
- Tue Jan 22, 2019 5:52 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Changing pressure
- Replies: 3
- Views: 321
Re: Changing pressure
When pressure is increased, equilibrium will favor the side with less moles of gas. Since the reaction has two moles of reactant gas and two moles of reactant product, there is no change in equilibra.
- Tue Jan 22, 2019 5:38 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: percent ionization
- Replies: 1
- Views: 247
Re: percent ionization
Percent ionization is the concentration of {H3O+] or [OH]- divided by the initial concentration of the acid or base, multiplied by 100%.
- Tue Jan 15, 2019 9:25 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Hydrofluoric Acid
- Replies: 3
- Views: 360
Re: Hydrofluoric Acid
HF is a weak acid due to the high electronegativity difference between hydrogen and fluorine, making it harder for HF to give up an H+ and dissociate.
- Tue Jan 15, 2019 7:21 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pH question
- Replies: 3
- Views: 288
Re: pH question
I have the 6th edition textbook and solution manual for it. As I was working on 12.29 part d, i noticed that I got pOH=0.15 & pH=13.85 but the solutions manual has pOH=3.15 and pH=10.85 . The way i solved was ((2.00 mL/.500mL)*(.175))= .7 then i did -log(.7) which gave me the pOH=.15 what the b...
- Tue Jan 15, 2019 7:13 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier - Volume
- Replies: 2
- Views: 180
Re: Le Chatelier - Volume
Instead of explaining that, as volume decreases, the reaction shifts towards the side with less moles of gas, Dr. Lavelle is saying that it is better to discuss the effect of the volume change in terms of concentration. He used the reaction N2(g) + 3 H2(g) => 2 NH3 (g) to explain the concept: For ex...
- Tue Jan 08, 2019 11:21 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium Constants for Gases
- Replies: 1
- Views: 144
Re: Equilibrium Constants for Gases
Increasing the pressure for gases will not affect the equilibrium constant, but changing the temperature of the system will.
- Tue Jan 08, 2019 7:51 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: 11.1d
- Replies: 2
- Views: 265
Re: 11.1d
The equilibrium value K is constant, so if you were to increase the concentration of reactants, that would mean the concentration of the products would also need to increase in order to maintain the constant value of K.
- Mon Jan 07, 2019 5:30 pm
- Forum: General Science Questions
- Topic: Chem textbook
- Replies: 3
- Views: 407
Re: Chem textbook
It's basically the textbook, but with just the pages not bound together. It comes with an access code so that you can get the online version of the textbook as well.
- Wed Dec 05, 2018 1:04 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Ordering Polarizability and Polarizing Power
- Replies: 4
- Views: 2049
Ordering Polarizability and Polarizing Power
Order these anions in order from least to most polarizable: I-, Cl-, S2-, P3- Order these cations in order from least to most polarizing power: Li+, Ca2+, Cs+, Ba2+ How would I go about determining the relative sizes of ions? I know that a small cation has high polarizing power, and a large anion is...
- Mon Dec 03, 2018 1:20 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Hydronium
- Replies: 4
- Views: 457
Re: Hydronium
H3O+ and H+ in an aqueous solution basically mean the same thing, as H+ in water is the hydronium ion. Both are used interchangeably, H+ is just the shorter way.
- Mon Dec 03, 2018 1:07 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis vs. Bronsted
- Replies: 5
- Views: 4022
Re: Lewis vs. Bronsted
I just remember it as, since Lewis structures involve electron pairs, a Lewis acid accepts (A in acid -> accept) electron pairs and a Lewis base therefore donates electron pairs.
For Bronsted, I have to just remember that an acid donates a proton/H+ and a base accepts a proton/H+.
For Bronsted, I have to just remember that an acid donates a proton/H+ and a base accepts a proton/H+.
- Mon Dec 03, 2018 1:00 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: pH and pOH
- Replies: 1
- Views: 258
Re: pH and pOH
I think that we will mostly focus on calculating pH, but I would know how to find pOH from pH, [H3O+], and [OH-] just in case.
- Tue Nov 27, 2018 11:04 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: 4.17
- Replies: 3
- Views: 419
Re: 4.17
Couldn't there be double bonds connecting the two oxygen atoms with two lone pairs to the central atom, along with one lone pair on the central oxygen? That would lead to 18 total electrons and a formal charge of zero for all three oxygen atoms. Or does the central oxygen also have to obtain a full ...
- Tue Nov 27, 2018 6:05 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: 6th Edition Homework 6.19
- Replies: 1
- Views: 200
Re: 6th Edition Homework 6.19
London dispersion forces increase as the size of the molecule increases, particularly surface area by which the interactions can take place.
Pentane is linear and not as compact, and therefore should have stronger London forces.
Pentane is linear and not as compact, and therefore should have stronger London forces.
- Tue Nov 27, 2018 6:02 pm
- Forum: Bond Lengths & Energies
- Topic: polar
- Replies: 2
- Views: 416
Re: polar
Polarizability is the ease by which an electron cloud can be distorted, while polarizing power describes the ability to distort an electron cloud. Polarizability describes an anion, and increases as its size increases (since a larger electron cloud is easier to distort) and negative charge decreases...
- Mon Nov 26, 2018 11:38 pm
- Forum: Dipole Moments
- Topic: Dipole Moment Calculation
- Replies: 3
- Views: 299
Re: Dipole Moment Calculation
I am pretty sure we are not expected to know how to calculate the actual dipole moment/charge difference, just be able to identify if a molecule has a dipole moment or not.
- Mon Nov 26, 2018 11:36 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: Ion- Ion and Dipole- Dipole
- Replies: 1
- Views: 199
Re: Ion- Ion and Dipole- Dipole
HCl forms a covalent polar bond between H and Cl, since both are nonmetals and have a electronegativity difference of less than 2. Therefore, since it is covalent and polar, a dipole moment exists in HCl where the negative end of F and the positive end of H in another HCl molecule attracts each other.
- Mon Nov 26, 2018 9:18 pm
- Forum: Sigma & Pi Bonds
- Topic: 2F.17 7th ed: Pi bond
- Replies: 2
- Views: 373
Re: 2F.17 7th ed: Pi bond
In CH2O, carbon forms a double bond with oxygen. Double bonds consist of one sigma bond and one pi bond. Therefore, there are 3 sigma and 1 pi bonds.
- Mon Nov 26, 2018 9:15 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Homework question
- Replies: 4
- Views: 336
Re: Homework question
Forming double bonds with oxygen allows the oxygen atoms to have a formal charge of zero, rather than -1 with single bonds.
- Mon Nov 26, 2018 3:41 pm
- Forum: General Science Questions
- Topic: Test 3
- Replies: 4
- Views: 475
Re: Test 3
The topics discussed in lecture on Monday (ligands and coordinating compounds) will not be covered on Test 3, right?
- Mon Nov 26, 2018 11:20 am
- Forum: Ionic & Covalent Bonds
- Topic: Self Test 3.12A (Sixth Edition)
- Replies: 1
- Views: 369
Re: Self Test 3.12A (Sixth Edition)
Oxygen has a greater electronegativity value compared to chlorine. Both compounds are ionic, but since the electronegativity difference between oxygen and phosphorous is greater, compound A, P4O10, has greater ionic character.
- Mon Nov 26, 2018 11:15 am
- Forum: Octet Exceptions
- Topic: Atoms with expanded octets
- Replies: 4
- Views: 719
Re: Atoms with expanded octets
Typically nonmetals located in period 3 and below are able to have expanded octets, but metals are unlikely to have expanded octets as they tend to lose electrons instead of gaining in order to fill a valence shell.
- Mon Nov 19, 2018 1:33 pm
- Forum: Balancing Chemical Reactions
- Topic: Why do we balance chemical equations?
- Replies: 13
- Views: 8350
Re: Why do we balance chemical equations?
Balancing chemical equations makes sure that the number of moles of reactants and products are the same, and therefore agree with the law of conservation of mass.
- Mon Nov 19, 2018 1:21 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Homework This Week
- Replies: 1
- Views: 245
Re: Homework This Week
Week 8 homework should be turned in with week 9 homework if your discussion is on Thursday or Friday. I would ask your TA if your discussion section is on Tuesday or Wednesday, though.
- Mon Nov 19, 2018 1:13 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Electron geometry vs Molecular geometry
- Replies: 3
- Views: 414
Re: Electron geometry vs Molecular geometry
Electron geometry describes the arrangement of electrons in an atom, including lone pairs, while molecular geometry describes the arrangement of atoms without lone pairs. A molecule with two atoms bonded to a central atom and one lone pair, such as H2O, will have a trigonal planar electron geometry....
- Mon Nov 19, 2018 1:00 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Exam 3 Topics [ENDORSED]
- Replies: 6
- Views: 680
Re: Exam 3 Topics [ENDORSED]
From Dr. Lavelle's website:
Test 3 covers: End of Bonding from 3.12 (6 Ed.) and from 2D (7 Ed.); and all of Molecular Shape and Structure
Test 3 covers: End of Bonding from 3.12 (6 Ed.) and from 2D (7 Ed.); and all of Molecular Shape and Structure
- Mon Nov 19, 2018 12:46 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angle
- Replies: 8
- Views: 719
Re: Bond Angle
I learned in high school that, with each additional lone pair, the bond angles are typically reduced by 2.5 degrees from what is suggested by the model. However, as long as you note that the angles are less than the model, that should be fine.
- Sun Nov 18, 2018 11:58 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 2
- Views: 259
Re: Bond Angles
Typically, when a lone pair is present in the molecule, bond angles will slightly differ since lone pairs repel other electrons more strongly than bonded pairs.
- Sun Nov 18, 2018 11:54 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Test 3
- Replies: 19
- Views: 1312
Re: Test 3
Does anyone know where/if there's a VSEPR chart in the 6th edition of the textbook?
- Mon Nov 12, 2018 7:44 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic Compounds 2D3
- Replies: 2
- Views: 469
Re: Ionic Compounds 2D3
You can determine which atoms have ionic bonds by looking at their electronegativity differences. A difference of over approximately 2 typically means that there is an ionic bond. The Ba - Br bond has a larger difference in electronegativity values compared to Be + Br and B + Br. Br = 2.96, Ba = 0.8...
- Mon Nov 12, 2018 7:34 pm
- Forum: Electronegativity
- Topic: Electronegativity Graph
- Replies: 4
- Views: 442
Re: Electronegativity Graph
Why is there a decrease in electronegativity for one of the elements between atomic numbers 20 and 30, and between 40 and 50?
- Mon Nov 12, 2018 6:20 pm
- Forum: Dipole Moments
- Topic: Interaction Potential Energy
- Replies: 3
- Views: 208
Re: Interaction Potential Energy
Alpha represents the polarizability, which depends on the number of electrons and the size of the atom or molecule. r is the distance between the two atoms or molecules. The potential energy equation shows that an increase in size or molar mass,, or a decrease in distance, leads to a stronger attrac...
- Mon Nov 05, 2018 8:21 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Week 6 HOmework
- Replies: 4
- Views: 368
Re: Week 6 HOmework
Should our Week 6 Homework include topics that were already covered on the midterm, or only the new material from Friday's lecture?
- Mon Nov 05, 2018 5:19 pm
- Forum: Lewis Structures
- Topic: Lewis Structure for N2O
- Replies: 7
- Views: 1207
Re: Lewis Structure for N2O
Nitrogen should be in the center of the Lewis structure since it is the least electronegative atom of the two.
- Mon Nov 05, 2018 9:18 am
- Forum: Lewis Structures
- Topic: ONF
- Replies: 2
- Views: 364
Re: ONF
The central element for the Lewis structure of ONF should be the atom with the lowest electronegativity, which in this case is nitrogen.
- Sun Nov 04, 2018 9:49 pm
- Forum: Lewis Structures
- Topic: Garlic Bread Review 12b
- Replies: 2
- Views: 287
Re: Garlic Bread Review 12b
Oxygen is more electronegative compared to chlorine, and therefore should be the atom with the negative formal charge in the molecule.
- Tue Oct 30, 2018 6:28 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Perchlorate (ClO4)-
- Replies: 7
- Views: 12428
Re: Perchlorate (ClO4)-
Finding out the formal charge of the central atom should tell you whether or not the element will follow the octet guideline, given that the element is in Periods 3+. For example, in ClO4-, three O are double bonded with the Cl so that the Cl has a formal charge of zero. If the three O were single b...
- Tue Oct 30, 2018 5:46 pm
- Forum: Ionic & Covalent Bonds
- Topic: Likely ion charge for Ga?
- Replies: 2
- Views: 488
Re: Likely ion charge for Ga?
Metals tend to lose electrons in order to acquire a noble gas configuration, and for Ga, it is easier to lose three electrons than to gain five electrons.
- Tue Oct 30, 2018 5:36 pm
- Forum: Octet Exceptions
- Topic: Structure of HClO3
- Replies: 1
- Views: 2807
Re: Structure of HClO3
HClO3 has 1+7+(3*6) = 26 valence electrons Start by putting Cl in the center (since it's the least electronegative), then draw the three oxygen around the Cl. For one of the oxygen, add the hydrogen next to it. Connect each of them with a single bond, and then fill the rest of the lone pairs. Howeve...
- Mon Oct 22, 2018 12:46 pm
- Forum: Properties of Light
- Topic: Chem Homework 1.55 Mistake?
- Replies: 2
- Views: 225
Re: Chem Homework 1.55 Mistake?
The question notes that v/c is used to represent energy with unit cm-1 (reciprocal centimeters) in infrared spectroscopy, rather than absolute wavelength.
- Mon Oct 22, 2018 12:31 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Electron density?
- Replies: 4
- Views: 199
Re: Electron density?
Electron density represents the probability of an electron being present in a given space around the atom's nucleus, and is responsible for the shapes of the orbitals (which are mathematical functions that represent this probability).
- Mon Oct 22, 2018 12:09 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Confused about Copper and Chromium [ENDORSED]
- Replies: 2
- Views: 1754
Re: Confused about Copper and Chromium [ENDORSED]
Essentially chromium has five 3d orbitals, four of which have a valence electron. Another electron is taken from the 4s energy level in order to occupy the fifth 3d orbital (so that all five 3d orbitals have one electron each) since symmetry is favored. The same happens for copper, where all but the...
- Mon Oct 15, 2018 12:51 pm
- Forum: General Science Questions
- Topic: Uncertainty Principle Problem
- Replies: 1
- Views: 342
Re: Uncertainty Principle Problem
The delta speed is multiplied by 2 since ±1.0 mm/s means a range of uncertainty of 2.0 mm/s.
For example, if the speed were 5.0mm/s ±1.0 mm/s, then that would mean the speed would be anywhere between 4.0 mm/s and 6.0 mm/s.
6.0 - 4.0 = 2.0 mm/s, which is the uncertainty in the speed (∆v).
For example, if the speed were 5.0mm/s ±1.0 mm/s, then that would mean the speed would be anywhere between 4.0 mm/s and 6.0 mm/s.
6.0 - 4.0 = 2.0 mm/s, which is the uncertainty in the speed (∆v).
- Mon Oct 15, 2018 12:38 pm
- Forum: DeBroglie Equation
- Topic: 1B19 Edition 7
- Replies: 2
- Views: 119
Re: 1B19 Edition 7
Since both the proton and the neutron have the same mass, their wavelengths are the same as well. The difference is 0, so the percentage should be 0%.
- Mon Oct 15, 2018 12:26 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Incorrect Atomic Model
- Replies: 6
- Views: 452
Re: Incorrect Atomic Model
Essentially we are trying to use the Heisenberg Uncertainty Model to disprove the atomic model that an electron is located inside the nucleus of an atom with diameter 1.7*10^-15 m (electrons are located in the space around the nucleus). We used the uncertainty model to determine the delta velocity (...
- Mon Oct 08, 2018 5:48 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Number of questions on test one [ENDORSED]
- Replies: 39
- Views: 21471
Re: Number of questions on test one [ENDORSED]
705160853 wrote:Also, is the quiz only testing topics in Outline 1? In other words, is the quantum stuff going to be on the test too
My TA said that the quiz will only cover the Fundamentals topic, and will not include stuff on The Quantum World.
- Mon Oct 08, 2018 12:09 pm
- Forum: Properties of Light
- Topic: Problem 1b 7b
- Replies: 1
- Views: 151
Re: Problem 1b 7b
First, you need to find the amount of energy that is released by one atom of sodium using E=hv and c=(lambda)v You're given the wavelength as 589 nm (which is lambda), and the speed of light (c) is given as 3.00x10^8 m/s Plug those values into c=(lambda)v to find v (remember to convert units first),...
- Mon Oct 08, 2018 12:00 pm
- Forum: SI Units, Unit Conversions
- Topic: Homework for Week 2
- Replies: 16
- Views: 985
Re: Homework for Week 2
You can do problems from either the Quantum World or Fundamentals for Week 2
- Mon Oct 01, 2018 12:00 am
- Forum: Significant Figures
- Topic: Rounding vs. Storing answers each step [ENDORSED]
- Replies: 2
- Views: 252
Re: Rounding vs. Storing answers each step [ENDORSED]
Usually, I don't round off my answers to each step until the very end when I write the final calculation in the proper number of significant figures. I find that rounding off steps tends to give me an answer that's off by a few digits, so I would recommend storing each step's answer on the calculator.
- Sun Sep 30, 2018 11:05 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Question E29
- Replies: 1
- Views: 419
Re: Question E29
For Part B and C, you need the number of moles of CuCl 2 * 4H 2 O calculated in Part A, which is 0.0417 mol CuCl 2 *4H 2 O . Part B: For each mole of CuCl 2 *4H 2 O, there are two moles of Cl- because of the subscript number 2 in CuCl 2 . Therefore, multiply 0.0417 by 2 to get 0.0834 mol Cl- ions . ...
- Sun Sep 30, 2018 9:07 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Molar Mass of Sulfide
- Replies: 2
- Views: 550
Re: Molar Mass of Sulfide
The question first wants you to determine the metal "M" in M(OH)2 with molar mass 74.10 g/mol, which we can find by finding the molar mass of "M." (OH)2 has molar mass: (16.00+1.01)*2 = 34.02 g/mol Molar mass of "M" in M(OH)2 = 74.10 g/mol - 34.02 g/mol = 40.08 g/mol Lo...