Search found 50 matches

by Sydney Wu 2M
Sun Mar 05, 2017 8:52 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 3 Winter 2017
Replies: 183
Views: 19638

Re: Quiz 3 Winter 2017

Can someone help me with #3 I don't understand how both of them are nucleophiles? The line diagram has multiple double bonds which are made up of a pi bond. These pi bonds serve as areas of high electronegativity due to their being so many localized electrons at each pi bond. This make it attracted...
by Sydney Wu 2M
Thu Mar 02, 2017 3:18 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: Catalysts/Enzymes regarding Entropy
Replies: 1
Views: 768

Catalysts/Enzymes regarding Entropy

Entropy is a measure of disorder, so if you make delta S less positive, you decrease entropy (more order), and if you make delta S less negative, you increase entropy (more disorder), correct? In lecture, we were told that catalysts and enzymes speed a reaction by putting reactants in the correct or...
by Sydney Wu 2M
Sun Feb 26, 2017 8:18 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Question 15.79
Replies: 1
Views: 286

Question 15.79

"In the reaction of Her with the reactive intermediate CH 3 CH=CHCH 2 + , at low temperatures the predominant product is CH3CHBrCH=CH2, but at high temperatures, the predominant product is CH 3 CH=CHCH 2 Br. (a) Which product is formed by the pathway with the larger activation energy? (b) Does ...
by Sydney Wu 2M
Sat Feb 18, 2017 1:10 pm
Forum: General Rate Laws
Topic: Unique Average Rate --> Rate Law [ENDORSED]
Replies: 2
Views: 347

Unique Average Rate --> Rate Law [ENDORSED]

Page 60 of the course reader says that the reaction rate is -(1/a)*(dR/dt) = k[R]n. Is there any specific derivation to come to this conclusion, or is this just the definition of a reaction rate?
by Sydney Wu 2M
Fri Feb 10, 2017 6:16 am
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolysis: Water 1/2 Rxn
Replies: 1
Views: 342

Electrolysis: Water 1/2 Rxn

The textbook gives us: 2 H2(g) + O2(g) --> 2 H2O(l) Ecell = +1.23V at pH = 7 2 H2O(l) --> 2 H2(g) + O2(g) Ecell = -1.23V at pH = 7 O2(g) + 4 H+ (aq) + 4e- --> 2 H2O(l) E = +0.82V at pH = 7 How do we know when to use these equations as an anode or cathode reaction, and how do we determine which one t...
by Sydney Wu 2M
Sun Feb 05, 2017 4:37 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Problem 14.25
Replies: 3
Views: 377

Problem 14.25

"Arrange the following metals in order of increasing strength as reducing agents for species in aqueous solution: (a) Cu, Zn, Cr, Fe (b) . . . " When looking up the standard reduction potentials in Appendix 2B, there are multiple values for some of the metals (i.e. Cu has E* values for Cu ...
by Sydney Wu 2M
Thu Feb 02, 2017 2:01 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Gibbs free energy for cell rxns: UNITS
Replies: 2
Views: 280

Gibbs free energy for cell rxns: UNITS

When calculating delta G* using -nFE*, units cancel nicely to yield a result in units J. However, in previous exercises, delta G* has had units kJ.mol-1. I know you can convert J to kJ, but what are the correct units for delta G*?
by Sydney Wu 2M
Sun Jan 29, 2017 2:20 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy/Equil Constant Relationship
Replies: 1
Views: 279

Gibbs Free Energy/Equil Constant Relationship

On page 41 of the course reader, it says delta G* is positive when K<1 and that delta G* is negative when K>1. Does that mean the forward reaction is not spontaneous when K<1 and is when K>1? I understand the arithmetic but I don't understand because if K<1, the reaction will want to go forward (spo...
by Sydney Wu 2M
Sat Jan 28, 2017 8:13 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Problem 9.63
Replies: 1
Views: 242

Problem 9.63

Does a negative delta G* mean stability in addition to spontaneity? Why?
by Sydney Wu 2M
Thu Jan 26, 2017 4:54 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Problem 9.47
Replies: 1
Views: 265

Problem 9.47

a) For Part (a), why was -w rev substituted in for q rev in the SSM? Also, will delta S tot always = 0 for reversible reactions? b) Part (b) asks to calculate delta S tot , delta S sys , and delta S surr for an isothermal, irreversible free expansion of an ideal gas beginning at 323K, 1.67L, and 4.9...
by Sydney Wu 2M
Fri Jan 20, 2017 6:19 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Problem 8.51
Replies: 1
Views: 290

Problem 8.51

"The enthalpy of formation of TNT is -67 kJ.mol -1 , and the density of TNT is 1.65 g.cm -3 ...Explore its potential as a rocket fuel by calculating its enthalpy density (enthalpy released per liter) for the reaction 4C 7 H 5 N 3 O 6 (s) + 21 O 2 (g) --> 28 CO 2 (g) + 10 H 2 O(g) + 6 N 2 (g) I ...
by Sydney Wu 2M
Fri Jan 13, 2017 7:02 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem 8.63c typo?
Replies: 2
Views: 273

Problem 8.63c typo?

Appendix 2A tells that delta hf* for K2S(aq) is -471.5. The answer in the textbook and SSM uses -417.5. Which is the correct delta hf* value?
by Sydney Wu 2M
Thu Jan 12, 2017 4:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpy of Form; Balanced Eqns
Replies: 2
Views: 272

Standard Enthalpy of Form; Balanced Eqns

Why are fractional coefficients required when balancing the equation? Don't whole numbers make everything cleaner?
by Sydney Wu 2M
Fri Dec 02, 2016 12:05 pm
Forum: *Titrations & Titration Calculations
Topic: 2012 Final Q7b
Replies: 1
Views: 275

2012 Final Q7b

"Calculate the pH at the stoichiometric point for the titration of 15.00mL of 0.100M HCOOH (K a = 1.8 x 10 -4 ) with 0.150M NaOH." Can someone please explain how to start this? I'm looking at the answer key and lecture notes, but I am completely lost on the logic of how to start and procee...
by Sydney Wu 2M
Wed Nov 30, 2016 11:17 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.57, pH/pOH v. pKa/pKb
Replies: 1
Views: 374

12.57, pH/pOH v. pKa/pKb

Are pH=pKa and pOH=pKb? I am unsuccessfully trying to figure out why the answers the 12.57 are what they are. Part (a) gives tells that the pH of .10M HClO2 was measured to be 1.2 and asks us to to determine Ka and pKa. Isn't 1.2 the same as pKa?
by Sydney Wu 2M
Tue Nov 29, 2016 8:39 am
Forum: Bronsted Acids & Bases
Topic: Textbook Q12.9c
Replies: 1
Views: 343

Textbook Q12.9c

Question 12.9c asks if the reaction CH3COOH(aq) + NH3(aq) ---> CH3CONH2 (aq) + H2O (l) can be classified as reaction between Bronsted acids and bases and to identify the acid and base if it as an acid-base reaction. Can someone please explain how no proton is transferred?
by Sydney Wu 2M
Tue Nov 29, 2016 6:23 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Q11.93b
Replies: 2
Views: 438

Re: Textbook Q11.93b

Alright, thanks!
by Sydney Wu 2M
Mon Nov 28, 2016 9:04 pm
Forum: Bronsted Acids & Bases
Topic: Common Acids/Bases
Replies: 3
Views: 453

Common Acids/Bases

Should we memorize the strong/weak acids and bases listed on pages 163-64 in the course reader?
by Sydney Wu 2M
Mon Nov 28, 2016 7:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Q11.93b
Replies: 2
Views: 438

Textbook Q11.93b

"0.020 mol NO 2 was introduced into a 1.00-L flask and the reaction 2 NO 2 (g) <--> N 2 O 4 (g) was allowed to come to equilibrium at 298 K. (a) Using information in Table 11.2, calculate the equilibrium concentrations of the two gases. (b) The volume of the flask is reduced to half its origina...
by Sydney Wu 2M
Mon Nov 28, 2016 7:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When to use atm v. bar units [ENDORSED]
Replies: 4
Views: 1082

When to use atm v. bar units [ENDORSED]

Should we always use atm (unless specified in the question to use bar)? For instance, Q8 on p. 43 of the quiz workbook asks us to calculate the equilibrium partial pressures but does not specify which units to use. Q10 on the following page requires you to convert from molar concentration to partial...
by Sydney Wu 2M
Mon Nov 28, 2016 10:53 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Quiz Workbook P 49 Q9
Replies: 2
Views: 450

Re: Quiz Workbook P 49 Q9

Great, thank you!
by Sydney Wu 2M
Sun Nov 27, 2016 8:09 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Quiz Workbook P 44 Q9
Replies: 2
Views: 3451

Quiz Workbook P 44 Q9

Is this the type of question where it gives you too much information (are K and the molar concentrations necessary)? Do you even need to use an ICE box?
by Sydney Wu 2M
Sun Nov 27, 2016 8:05 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Quiz Workbook P 49 Q9
Replies: 2
Views: 450

Quiz Workbook P 49 Q9

My answer and the answer key do not match at all, but I don't know where I went wrong! Can someone please explain how to find K if 8.15% of the reactant remains at equilibrium? Thank you!
by Sydney Wu 2M
Sat Nov 26, 2016 3:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: H2O [ENDORSED]
Replies: 2
Views: 469

Re: H2O [ENDORSED]

Liquids and solids are pure substances, and pure substances are not included in the calculation.
by Sydney Wu 2M
Tue Nov 15, 2016 6:49 am
Forum: Naming
Topic: Amine
Replies: 1
Views: 309

Amine

If NH3 is amine, how come there are only 2 Hs for each amine in en and dien?
by Sydney Wu 2M
Thu Nov 10, 2016 2:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ch 11 #7c
Replies: 2
Views: 442

Ch 11 #7c

The SSM uses the initial pressure value for both the numerator and denominator; how? Should we assume that the pressure is constant?
by Sydney Wu 2M
Mon Nov 07, 2016 10:24 am
Forum: Naming
Topic: order of ligand names [ENDORSED]
Replies: 7
Views: 976

Re: order of ligand names [ENDORSED]

I notice that when water is a ligand (looking at #31), the SSM writes its formula as H2O for one exercise and OH2 for another one. I know the order of the atoms matter, so which one is correct? Why?
by Sydney Wu 2M
Mon Nov 07, 2016 6:26 am
Forum: Naming
Topic: Number 29 from the Hw [ENDORSED]
Replies: 4
Views: 472

Re: Number 29 from the Hw [ENDORSED]

Finding the oxidation number of metals is generally pretty straightforward as you would just subtract the overall charge of the compound by any negatively charged ligands located between the brackets (for the iron compound, there are 6 CN - molecules so subtract that from -4 gives a 2+ charge for t...
by Sydney Wu 2M
Thu Nov 03, 2016 5:52 pm
Forum: Electronegativity
Topic: Problem 4.57
Replies: 3
Views: 698

Re: Problem 4.57

So, generally speaking, ionization energy and electronegativity are directly related (IE and EN increase across a period), but oxygen is an exception since it has one e- over a half-filled orbital?
by Sydney Wu 2M
Wed Nov 02, 2016 1:46 pm
Forum: Hybridization
Topic: 2014 Midterm Q8
Replies: 5
Views: 560

Re: 2014 Midterm Q8

Oh wait, I understand now, thank you!
by Sydney Wu 2M
Wed Nov 02, 2016 12:41 pm
Forum: Hybridization
Topic: 2014 Midterm Q8
Replies: 5
Views: 560

Re: 2014 Midterm Q8

So are pi bonds always not hybridized?
by Sydney Wu 2M
Tue Nov 01, 2016 10:25 am
Forum: Hybridization
Topic: 2014 Midterm Q8
Replies: 5
Views: 560

2014 Midterm Q8

For double bonding, why are the overlapping orbitals that form a pi bond not hybridized?
by Sydney Wu 2M
Tue Nov 01, 2016 10:11 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: 2012 Midterm Q3c
Replies: 2
Views: 503

2012 Midterm Q3c

Are we expected to know what wavelength values each atomic spectra region includes?
by Sydney Wu 2M
Tue Nov 01, 2016 8:59 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Molecular Orbital theory
Replies: 5
Views: 523

Re: Molecular Orbital theory

The midterm covers only up to the end of hybridization, so there is no MO Theory.
by Sydney Wu 2M
Tue Nov 01, 2016 8:13 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Question 4.61
Replies: 1
Views: 182

Question 4.61

When you have a heteronuclear diatomic molecule with one Z > 8 and the other Z < 8, how do you know when the pi bonding orbital comes before the sigma bonding orbital, and vice versa? i.e. CO
by Sydney Wu 2M
Tue Nov 01, 2016 8:03 am
Forum: Electronegativity
Topic: Problem 4.57
Replies: 3
Views: 698

Problem 4.57

How is oxygen more electronegative than nitrogen if it has a lower ionization energy?
by Sydney Wu 2M
Mon Oct 31, 2016 11:00 pm
Forum: Lewis Structures
Topic: 2012 Midterm Q5b, part (e)
Replies: 2
Views: 331

Re: 2012 Midterm Q5b, part (e)

That's right, thank you!
by Sydney Wu 2M
Mon Oct 31, 2016 6:11 pm
Forum: Lewis Structures
Topic: 2012 Midterm Q5b, part (e)
Replies: 2
Views: 331

2012 Midterm Q5b, part (e)

Why is N the central atom for N2O? Doesn't O have the lower ionization energy?
by Sydney Wu 2M
Mon Oct 31, 2016 5:57 pm
Forum: Lewis Structures
Topic: Lewis acids and bases [ENDORSED]
Replies: 2
Views: 514

Re: Lewis acids and bases [ENDORSED]

I understand now, thank you!
by Sydney Wu 2M
Mon Oct 31, 2016 11:46 am
Forum: Hybridization
Topic: Hybrid Orbital combinations
Replies: 2
Views: 205

Re: Hybrid Orbital combinations

Great, thank you!
by Sydney Wu 2M
Mon Oct 31, 2016 11:45 am
Forum: Lewis Structures
Topic: Lewis acids and bases [ENDORSED]
Replies: 2
Views: 514

Lewis acids and bases [ENDORSED]

How can you determine whether or not an element is a Lewis acid or base? For instance, for AlCl3, is Al donating e-s to Cl so that Cl has a full octet, therefore making it a Lewis base?
by Sydney Wu 2M
Fri Oct 28, 2016 10:40 am
Forum: Hybridization
Topic: Hybrid Orbital combinations
Replies: 2
Views: 205

Hybrid Orbital combinations

I do not understand how hybrid combinations are derived. For instance, the 4 hybrid orbitals of sp3 are:

h1 = s + px + py + pz
h2 = s - px - py + pz
h3 = s - px + py - pz
h4 = s + px - py - pz

Are these fundamental? Will we be expected to know these for the midterm?
by Sydney Wu 2M
Thu Oct 20, 2016 10:22 am
Forum: Formal Charge and Oxidation Numbers
Topic: Problem 3.65
Replies: 1
Views: 316

Problem 3.65

How is possible for elements in Group 18 to form bonds (don't they already have a filled octet)?
by Sydney Wu 2M
Tue Oct 18, 2016 5:36 pm
Forum: Ionic & Covalent Bonds
Topic: Question 3.39b [ENDORSED]
Replies: 1
Views: 310

Question 3.39b [ENDORSED]

Can someone please explain why P is the central atom of the Lewis structure? It makes sense on paper because it looks nice, but doesn't K have the lower ionization energy?
by Sydney Wu 2M
Wed Oct 12, 2016 9:55 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Numbers n, l, and m
Replies: 2
Views: 326

Quantum Numbers n, l, and m

I am very confused on the concept on n, l, and m l ... 1) Can the relationship between n, l, and m be described as shell, sub-shell, and orbital within a sub-shell, respectively? 2) Does the l-value tell you the highest possible sub-shell of that particular energy level? (i.e. n=3; l=0, 1, & 2 -...
by Sydney Wu 2M
Wed Oct 05, 2016 6:25 pm
Forum: Properties of Electrons
Topic: Difficulty with Problem 1.55 [ENDORSED]
Replies: 1
Views: 316

Re: Difficulty with Problem 1.55 [ENDORSED]

I too, at first, converted the cm into m and got a different answer from the SSM. I re-read the problem, and it is says that it's "common to express energy in terms of v/c with units cm -1 " (for this particular kind of spectroscopy). So literally all you have to do is set up v/c = some va...
by Sydney Wu 2M
Wed Sep 28, 2016 9:28 am
Forum: SI Units, Unit Conversions
Topic: H-Atom Electron in Energy Level n
Replies: 1
Views: 223

H-Atom Electron in Energy Level n

In the Atomic Spectra and The Bohr Frequency Condition module, we derived an equation that resulted in . In the book and SSM, R is positive, not negative. Which equation is correct?

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