## Search found 149 matches

Thu Mar 05, 2020 10:40 pm
Forum: Balancing Redox Reactions
Topic: HW 6L.9
Replies: 3
Views: 83

### Re: HW 6L.9

The salts will dissociate in water, so see their reduction potentials to determine which one will be reduced and which one will be oxidized, then write the overall equation with that in mind.
Tue Mar 03, 2020 4:48 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6N3 a) Concentrations?
Replies: 1
Views: 67

### 6N3 a) Concentrations?

Exercise: Predict the potential of each of the following cells: (a) Pt(s)|H2(g, 1.0 bar)|HCl(aq, 0.075 mol/L) || HCl(aq, 1.0 mol/L)|H2(g, 1.0 bar)|Pt(s) -------------------------------------------------------------------------- The solutions manual shows ln Q = (0.075^2 / 1.0^2). Why is 0.075 M plug...
Tue Mar 03, 2020 4:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: A Reactivity Epiphany
Replies: 2
Views: 77

### Re: A Reactivity Epiphany

We will be given a sheet with all the half-reactions and standard potentials needed, though, right?
Mon Mar 02, 2020 12:05 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Order of compounds in cell diagram?
Replies: 5
Views: 96

### Re: Order of compounds in cell diagram?

Astrid Lunde 1I wrote:Also remember aq us closest to the center of the cell diagram than gas and lastly solid.

Thank you, that's what I needed to know.
Mon Mar 02, 2020 11:54 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Order of compounds in cell diagram?
Replies: 5
Views: 96

### Re: Order of compounds in cell diagram?

sarahforman_Dis2I wrote:I believe it is cathode on the right, anode on the left. Whatever is being oxidized is on the left and whatever is being reduced is on the right.

Oh I mean inside the half-cell. Not the order between Cl and H but between H+ and H2. That is, H2|H+ versus H+|H2.
Mon Mar 02, 2020 11:40 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Order of compounds in cell diagram?
Replies: 5
Views: 96

### Order of compounds in cell diagram?

Does the order in which I write a half-cell's components matter? For example, is H2|H+ || Cl-|Cl2 the same thing as writing H+|H2 || Cl-|Cl2?
Thu Feb 27, 2020 3:00 pm
Forum: Balancing Redox Reactions
Topic: Galvanic Cell - Favorability and oxidation number?
Replies: 3
Views: 68

### Re: Galvanic Cell - Favorability and oxidation number?

I’m not sure but if the redox number you’re referring to is the E vale of the cell, then you can tell the reaction is favorable if the cell potential (E) is positive. I was referring to the oxidation number / state, like how Fe2+ has oxidation state 2+. But it would make sense that I wrote "re...
Thu Feb 27, 2020 2:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Difference between ΔΦ and cell potential / EMF? [ENDORSED]
Replies: 1
Views: 245

### Difference between ΔΦ and cell potential / EMF?[ENDORSED]

I'm not sure what the difference between the Galvanic potential ΔΦ and cell potential E(cell) aka EMF is. I know they both measure differences in potential between electrodes and have similar equations: ΔΦ = Φcathode - Φanode E(cell) = E(anode) - E(cathode) If someone could explain the difference an...
Thu Feb 27, 2020 2:27 pm
Forum: Balancing Redox Reactions
Topic: Galvanic Cell - Favorability and oxidation number?
Replies: 3
Views: 68

### Galvanic Cell - Favorability and oxidation number?

I can't recall if Dr Lavelle mentioned something like this, but is it possible to tell if a reaction is favorable / spontaneous just by the oxidation number change? Because I have a note on my notebook saying that the conversion of electric energy to chemical energy in the Galvanic cell "will o...
Mon Feb 24, 2020 10:16 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.1b
Replies: 1
Views: 26

### Re: 6N.1b

Yeah, it's a typo. In "Corrections to Solutions Manual" it's corrected to 1 electron. The final answer's K approximately equal to 100.
Mon Feb 24, 2020 10:11 pm
Forum: Balancing Redox Reactions
Topic: 6K.5 a
Replies: 1
Views: 38

### Re: 6K.5 a

You have to balance them because there are different numbers of O atoms. When balancing redox reactions, you balance both charge and atoms. In redox reactions, oxygen is balanced by adding H2O.
Mon Feb 24, 2020 1:09 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: midterm
Replies: 5
Views: 88

### Re: midterm

I think the regrade request deadline was last Friday! But I'm not sure and sending an email asking won't hurt. But if it's just clarifying something I think you can email them anytime or approach them in discussion.
Mon Feb 24, 2020 1:08 am
Forum: Administrative Questions and Class Announcements
Topic: Hw 8
Replies: 10
Views: 147

### Re: Hw 8

5G and 6K-6N
Mon Feb 24, 2020 1:07 am
Forum: Administrative Questions and Class Announcements
Topic: Test 2 info
Replies: 8
Views: 149

### Re: Test 2 info

Test 2 is not cumulative. It covers the second page of outline 4 and the entirety of outline 5.
Mon Feb 24, 2020 12:59 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.3-d Water and oxygen cell reaction?
Replies: 1
Views: 40

### 6L.3-d Water and oxygen cell reaction?

I'm not sure how to write the half-reactions for Pt(s) | O2(g) | H+(aq) || OH-(aq) | O2(g) | Pt(s)
I can see that we're going to use water, but trying to write the reactions is giving me inverted answers. Could someone please walk me through this?
Mon Feb 17, 2020 3:03 pm
Forum: Administrative Questions and Class Announcements
Topic: Recommended Pathway for Chem Series
Replies: 13
Views: 413

### Re: Recommended Pathway for Chem Series

I'd recommend finishing 14A-14D first as they are requirements for upper division courses. You can take BL and CL later on without rush.
Sat Feb 15, 2020 5:23 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm Curve
Replies: 45
Views: 554

### Re: Midterm Curve

Emma Popescu 1L wrote:My TA said he will most likely curve the midterm because most people did very bad.

I hope he does make an exception and curve. The midterm had some unexpected questions :/
Sat Feb 15, 2020 5:21 pm
Forum: Balancing Redox Reactions
Topic: redox reactions
Replies: 3
Views: 65

### Re: redox reactions

Redox reactions are reactions in which the transfer of electrons between reactants occurs to form the products. It happens because when bonds are broken, some substances develop a net charge and attract / donate electrons in order to achieve their most stable states. The way it happens is that basic...
Wed Feb 12, 2020 11:39 am
Forum: Calculating Work of Expansion
Topic: Does the substance make a difference in expansion work?
Replies: 2
Views: 30

### Re: Does the substance make a difference in expansion work?

That was what I thought, but I wasn't sure. Thanks!
I got this from one of Lyndon's help sessions worksheet.
Tue Feb 11, 2020 9:57 pm
Forum: Calculating Work of Expansion
Topic: Does the substance make a difference in expansion work?
Replies: 2
Views: 30

### Does the substance make a difference in expansion work?

Some exercises specify a gas that is being compressed by a piston and I don't know whether knowing what gas it is (and therefore its properties, like molar mass) is important for solving the exercise. One example is: "Given a piston that expands from 0.200 L to 1.50 L, at 25 C, and is filled wi...
Tue Feb 11, 2020 9:51 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Pizza Rolls 3B
Replies: 2
Views: 55

### Re: Pizza Rolls 3B

The ice cream receives a total of 234 kJ. Part of it is used to increase its temperature from -2.8 C to fusion point at 0 C, the rest is used in the phase change of half of the mass of the ice cream (that is, 125 g / 2 = 62.5 g) from solid to liquid. First equation (temperature change): q = m.c.∆T =...
Tue Feb 11, 2020 9:23 pm
Forum: Phase Changes & Related Calculations
Topic: 4C.13
Replies: 1
Views: 71

### Re: 4C.13

You know that q(ice) = -q(water). Let's split that into two parts: A) q(ice) = heat required by phase change + heat required by temperature change q(ice) = n.∆H + m.c.∆T = (50 / 18).(6.01*10^3) + (50)(4.18)(Tf - 0) > Here, 6.01*10^3 (the enthalpy of fusion of water per mole) is given in one of the t...
Mon Feb 10, 2020 11:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Hw 5.39
Replies: 1
Views: 35

### Re: Hw 5.39

Pretty sure it's a typo and we're supposed to use table 5D.2 (Henry's Constants for gases at 20°C)
Mon Feb 10, 2020 11:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.61
Replies: 1
Views: 24

### Re: 5.61

C6H12O6 is dissolved in water, so no, it has no impact. Compression only really affects gases, but remember that this includes water vapor, which is denoted with (v) instead of (g). In short, we have the same number of gases in both sides, so compression doesn't affect equilibrium.
Mon Feb 10, 2020 11:16 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test 1 Problem 6
Replies: 2
Views: 62

### Re: Test 1 Problem 6

I believe the tests have different prompts for different sections. Could you post a picture or type the question please?
Mon Feb 10, 2020 1:10 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: heat capacity question
Replies: 1
Views: 18

### Re: heat capacity question

C equals n.C(molar), so when the exercise solution says it prefers q=CΔT I think it's just skipping the step where you plug in C = n.C(molar) You'd use -3227 kJ if you had only one mole of benzoic acid. However, you have 1.453 g (which does not equate to 1 mole of benzoic acid). Thus, to get the ent...
Sun Feb 09, 2020 11:58 pm
Forum: Calculating Work of Expansion
Topic: q=C delta T
Replies: 5
Views: 49

### Re: q=C delta T

You should use a different notation because these equations are different things. The variable Cs (sometimes denoted as c) stands for specific heat capacity, the heat required to change the temperature of 1 gram of a substance by +1°C. The variable C stands for heat capacity, the heat required to ch...
Sun Feb 09, 2020 11:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4C7
Replies: 1
Views: 33

### Re: 4C7

The formula for enthalpy change is ΔH(vaporization) = q / n, which gives an answer of energy units per moles. This is because enthalpy of phase change measures the energy required to take 1 mole of some substance from one state to the other.
Sun Feb 09, 2020 11:47 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Boltzmann equation
Replies: 5
Views: 60

### Re: Boltzmann equation

The Boltzmann Equation gives a relationship between entropy S and degeneracy W. Degeneracy describes all the possible microstates (i.e. positions) that might be occupied by the molecules of a system. They're related because entropy is the tendency towards disorder, and degeneracy describes all the w...
Wed Feb 05, 2020 7:24 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 7
Views: 111

### Re: Midterm

Looks like they haven't I looked for a post in the topic but couldn't find anything.
Sun Feb 02, 2020 6:42 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4A.13
Replies: 3
Views: 28

### Re: 4A.13

Kate Swertfager wrote:I think because the temp change between temp in K and temp in C is the same?

Correct. The units are different but when it comes to changes in temperature, the change value in both Celsius and Kelvin is numerically the same.
Sun Feb 02, 2020 6:30 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calculating q
Replies: 5
Views: 73

### Re: Calculating q

I think that what you're getting mixed up is heat capacity (symbol is capital "C") and specific heat capacity (in high school for me it was "c" but Prof Lavelle and the book are using Cs). C = Cs*m and q = C*ΔT, so when you plug Cs*m into q = C*ΔT, you get q = Cs*m*ΔT
Sun Feb 02, 2020 6:24 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Significance of Constant Pressure and Constant Volume
Replies: 1
Views: 40

### Re: Significance of Constant Pressure and Constant Volume

From what I've seen in the textbook, the questions will most likely clearly state whether we should consider constant volume / pressure / temperature / etc.
At constant pressure, use: ΔH = ΔU + P.ΔV
At constant volume, use: ΔH = Q(v) (that is, equal to the heat received by the system)
Sun Feb 02, 2020 6:15 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test 1 Pressure
Replies: 5
Views: 58

### Re: Test 1 Pressure

If pressure is increased by compression (as opposed to other methods like increasing temperature), the reaction will shift to whichever side has fewer moles of gas in total. This means that substances in solid / liquid state should not be accounted for.
Sun Feb 02, 2020 6:12 pm
Forum: Administrative Questions and Class Announcements
Topic: week 5 homework
Replies: 4
Views: 59

### Re: week 5 homework

Your hw should always aim to cover the most recent topics, so go for the Second and Third Laws of Thermodynamics. But if you feel too much difficulty don't worry and just pick some from the previous topic. Nobody's gonna keep a strict track of which topics you choose, it's more a matter of getting e...
Sun Feb 02, 2020 5:42 pm
Forum: Calculating Work of Expansion
Topic: 4B.13
Replies: 1
Views: 50

### Re: 4B.13

Correct. In the ideal gas equation, the units of P.V are atm*L. But for the work equation, we need joules, which is why in nRT we use R = 8.314 J·K-1·mol-1 instead of 8.206 × 10-2 L·atm·K-1·mol-1.
Wed Jan 22, 2020 12:12 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 6B 11
Replies: 3
Views: 67

### Re: 6B 11

Yeah of course. I'll give you an example. If I say "A is 100 times bigger than B", it's the same thing as "B is 100 times smaller than A". So what you need to extract from the exercise to solve this part is that the original solution is 100 times more concentrated than the dilute...
Tue Jan 21, 2020 8:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5J.5 D
Replies: 5
Views: 55

### Re: 5J.5 D

There isn't a typo; there are 2 moles of gas on the reactants' side (2 moles of HD) and 2 on the products' side (1 mole of H2 and 1 mole of D2). Thus, compression won't affect equilibrium.
Tue Jan 21, 2020 6:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test 1 Practice Worksheet #5
Replies: 6
Views: 122

### Re: Test 1 Practice Worksheet #5

Yes, I got 10.86
Tue Jan 21, 2020 12:08 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating pH from Concentration of Strong Acid/Base
Replies: 2
Views: 40

### Re: Calculating pH from Concentration of Strong Acid/Base

Since Ba(OH)2 is a strong acid, it is fully dissociated in water. This means that, at equilibrium, zero Ba(OH)2 is left and there is only Ba2+ and OH- in solution, dissociated from the quantity of reactant added to the water. If you write down the equation for this reaction, you will notice that the...
Mon Jan 20, 2020 11:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6D.15
Replies: 2
Views: 40

### Re: 6D.15

Use the ICE table. The initial concentration is just 0.055M of AlCl3, the rest is 0. Then, there will be a change of -x in [AlCl3] and +x in each of the products. The equilibrium concentration will be 0.055-x, x, x. Plug these expressions into the Ka expression and solve the resulting expression to ...
Mon Jan 20, 2020 11:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6A.23
Replies: 3
Views: 54

### Re: 6A.23

You don't need K nor the ICE table because Ba(OH)2 is a strong base and thus will be 100% dissociated in water. This means you can assume the equilibrium concentration of the reaction will be: [Ba2+]final = [Ba(OH)2]initial = 0.025M and [OH-]final = 2*[Ba2+]final = 0.05M Remember that these conclusi...
Mon Jan 20, 2020 11:10 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 6B 11
Replies: 3
Views: 67

### Re: 6B 11

Since I don't know which exercises you're referring to (when you mention that some exercises do 5/500 instead of 500/5), I'm not sure if there's a particular reason; but it's just a matter of finding a ratio of solvent between the original and the diluted, and as long as you know the magnitude of di...
Mon Jan 20, 2020 11:05 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 6.23 Buffer Solutions
Replies: 2
Views: 47

### Re: 6.23 Buffer Solutions

I wouldn't worry about it since it's not on the syllabus... When an exercise is not on the syllabus it sometimes means Dr Lavelle didn't teach the content, so we aren't able to solve it anyways
Mon Jan 20, 2020 11:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6d.1
Replies: 2
Views: 32

### Re: 6d.1

Just before the exercises there is an observation: "Refer to Tables 6C.1 and 6C.2 for Ka and Kb. Assume 25 8C throughout."
Wed Jan 15, 2020 10:57 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: calculating kP
Replies: 4
Views: 54

### Re: calculating kP

The standard unit is atm. I think all exercises will give partial pressures in atm but in case you need to convert a number to/from Pascals (1 atm = 101 325 Pa), you can find the conversion in the Constants and Equations PDF on Dr Lavelle's website.
Mon Jan 13, 2020 11:56 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Temperature change
Replies: 5
Views: 34

### Re: Temperature change

Increasing the temperature makes the reaction environment more energetic, and this extra energy is used in breaking chemical bonds, which speeds up reaction. It affects K because the formation of product may require heat (endothermic), so if the temperature raises then the forward reaction will be f...
Mon Jan 13, 2020 11:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6A.19
Replies: 6
Views: 84

### Re: 6A.19

Pretty sure the textbook question should be 3.1x10^-3 instead of just 3.1, since all the units are the same (L) and it's otherwise just plugging numbers in.
Mon Jan 13, 2020 11:35 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: HW 5I23
Replies: 1
Views: 89

### Re: HW 5I23

We know that we have 0.478 mol CH4 at equilibrium. The balanced equation is given, which means we can tell the concentration of H2O is 0.478 M since it has a proportion of 1:1 to CH4. From there, we can build the ICE table. CO 3H2 CH4 H2O 2 3 0 0 -x -3x* +x +x 2-x 3-3x .478 +x *This has to be 3x bec...
Mon Jan 13, 2020 10:02 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.5
Replies: 3
Views: 39

### Re: 5J.5

The simple way to think about it is the way you mentioned: when pressure is increased by compression, the reaction will tend towards the side with the higher number of moles. This means, for example, that in a) the reactant formation is favored. When the number of moles of gas is equal in both sides...
Mon Jan 13, 2020 9:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Which subforum do I ask my question under?
Replies: 1
Views: 31

### Re: Which subforum do I ask my question under?

I believe under "Equilibrium Constants & Calculating Concentrations" since there isn't a subforum for acids and bases specifically
Sun Jan 12, 2020 1:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: HW 5I.15
Replies: 3
Views: 44

### Re: HW 5I.15

The reaction is occurring in the forward direction, which means the solid NH4HS will yield more of the products -- in this case, the products are NH3 and H2S. In other words, the initial amount of NH3 (0.200 mol) will increase by x because of the reaction of NH4HS. So does this mean that whenever w...
Thu Jan 09, 2020 9:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Combining Equations
Replies: 1
Views: 31

### Re: Combining Equations

Yes, when combining equations the product of one reaction will be the reactant in the next, so it cancels out. When you've found all relevant reactions, you just have to multiply their K to find the final reaction's equilibrium constant.
Thu Jan 09, 2020 9:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Unites for K
Replies: 2
Views: 46

### Re: Unites for K

Because it's a ratio (between the amount of product and reactant)
Thu Jan 09, 2020 9:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: HW 5I.15
Replies: 3
Views: 44

### Re: HW 5I.15

The reaction is occurring in the forward direction, which means the solid NH4HS will yield more of the products -- in this case, the products are NH3 and H2S. In other words, the initial amount of NH3 (0.200 mol) will increase by x because of the reaction of NH4HS.
Thu Jan 09, 2020 8:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H.3 Multiplying K's
Replies: 2
Views: 38

### Re: 5H.3 Multiplying K's

Recall that in the formula for the equilibrium constant, we put in the concentration of each substance to the power of their coefficient. Consider also that when summing reactions, the product of one reaction is the reactant in the next. Thus, when we multiply K for these reactions, the product-turn...
Thu Jan 09, 2020 8:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How does the concentration change the equilibrium constant?
Replies: 2
Views: 31

### Re: How does the concentration change the equilibrium constant?

Hi nicolely3B! You are correct in saying that the K doesn't change as long as it is the exact same reaction. In the practice problems, these reactions are not exactly the same. They differ by the stoichiometric coefficients used in the Keq expression. The original expression looks something like th...
Thu Jan 09, 2020 8:27 pm
Forum: Ideal Gases
Topic: Rate of reaction
Replies: 2
Views: 36

### Re: Rate of reaction

The main factors are catalyst (addition of a substance that doesn't take part in the reaction but speeds it up, e.g. by decreasing energy required to break bonds), pressure, temperature, and concentration. This topic is pretty fundamental so I'm sure Dr Lavelle will be covering it in the near future...
Thu Jan 09, 2020 7:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How does the concentration change the equilibrium constant?
Replies: 2
Views: 31

### How does the concentration change the equilibrium constant?

I thought I remembered Dr Lavelle saying that the amount of product / reactant doesn't affect a reaction's equilibrium constant if the conditions are the same. But in question 1 in topic 5H we have to calculate the K for variations of the same reaction, and each has a different K. I understand the i...
Sun Dec 08, 2019 12:00 am
Forum: Air Pollution & Acid Rain
Topic: Final Exam
Replies: 4
Views: 313

### Re: Final Exam

I think we just have to know that nitrogen and sulfur oxides in the air are responsible for making the rain water acidic. Prof Lavelle didn't mention anything other than that
Sat Dec 07, 2019 11:57 pm
Forum: Administrative Questions and Class Announcements
Topic: Wavelength
Replies: 2
Views: 68

### Re: Wavelength

The last three audio-visual focus topics on Prof Lavelle's website all have a bunch of questions with wavelengths, but you have to go through the simpler, conceptual questions first. Other than that, I think Dino Nuggets (towards the end) has the best
Sat Dec 07, 2019 11:55 pm
Forum: Naming
Topic: Nitrito vs nitro
Replies: 1
Views: 46

### Re: Nitrito vs nitro

-kN means that the N atom is bonding to the central atom in the coordination complex, and -kO means that the O atom is bonding. In a formula, the bonded atom will be written closest to the central atom:
N is bonding: [metal(NO2)]
O is bonding: [metal(ONO)]
Sat Dec 07, 2019 5:24 pm
Forum: Lewis Acids & Bases
Topic: 6.21
Replies: 2
Views: 34

### Re: 6.21

It already has two bonds (1 double bond), therefore its octet is complete and its formal charge is zero. It's the most stable situation possible for Oxygen
Sat Dec 07, 2019 1:01 pm
Forum: Lewis Structures
Topic: Priority of factors when drawing Lewis structures
Replies: 4
Views: 180

### Re: Priority of factors when drawing Lewis structures

I'm not sure but I know that having an octet is the most important thing when drawing lewis structures and then usually from making sure each atom has an octet you can figure out how to best balance the formal charges. What if there is more than one way to make all atoms have eight electrons? Then ...
Sat Dec 07, 2019 1:25 am
Forum: Lewis Structures
Topic: Priority of factors when drawing Lewis structures
Replies: 4
Views: 180

### Re: Priority of factors when drawing Lewis structures

AngieGarcia_4F wrote:I'm not sure but I know that having an octet is the most important thing when drawing lewis structures and then usually from making sure each atom has an octet you can figure out how to best balance the formal charges.

What if there is more than one way to make all atoms have eight electrons?
Sat Dec 07, 2019 12:27 am
Forum: Lewis Structures
Topic: Priority of factors when drawing Lewis structures
Replies: 4
Views: 180

### Priority of factors when drawing Lewis structures

What is the hierarchy for the factors to draw the Lewis structure of lowest energy? E.g. if I had to order: - Central atom with FC = 0 - Overall charge = 0 - Electronegativity - etc. For example, when I was drawing the lowest energy structure for N2O, I was in doubt whether it was central atom with ...
Wed Dec 04, 2019 8:51 pm
Forum: Hybridization
Topic: Hybridization General Question
Replies: 3
Views: 95

### Re: Hybridization General Question

Sears 4A wrote:do we need to put the energy level into our answers when we write down hybridized orbitals?

Can't say for sure but probably not... I only see them in bonds in the book.
Wed Dec 04, 2019 6:35 pm
Forum: Hybridization
Topic: Hybridization General Question
Replies: 3
Views: 95

### Re: Hybridization General Question

2 stands for the energy level in which the hybridized orbitals are located. I think they're only necessary when writing bond hybridization. The number is associated with the element's period in the periodic table.
Wed Dec 04, 2019 6:34 pm
Forum: Hybridization
Topic: 2.45 Hybridization
Replies: 3
Views: 66

### Re: 2.45 Hybridization

It follows the same logic as the bonds. The oxygen has a hybridization of sp2 (two being lone pairs) because it is connected to three areas of electron density; each lone pair will have that hybridization because they are electrons in hybridized orbitals, same as if they were bonded
Wed Dec 04, 2019 5:29 pm
Forum: Hybridization
Topic: Drawing Acrylonitrile
Replies: 1
Views: 44

### Re: Drawing Acrylonitrile

This is an organic chain molecule. In other words, it's a chain formed by C. If you're not very familiar with ochem, another way to go around this would be: H is for sure on the periphery and central atoms are going to be the least electronegative, therefore, C-atoms are going to form the central ch...
Wed Dec 04, 2019 2:59 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Melting point of solid argon vs. xenon
Replies: 2
Views: 36

### Re: Melting point of solid argon vs. xenon

It's a larger atom, so it requires more energy to separate the additional electrons orbiting its nucleus.
Wed Dec 04, 2019 2:55 am
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charge for H20+HCl-->H30++Cl-(aq)
Replies: 1
Views: 100

### Re: Formal charge for H20+HCl-->H30++Cl-(aq)

Follow the usual procedure and, at the end, subtract the value of the charge if the compound is a cation / sum the value of the charge if the compound is an anion.
Wed Dec 04, 2019 2:54 am
Forum: Lewis Structures
Topic: 6.5b
Replies: 2
Views: 131

### Re: 6.5b

Cis-trans isomerism isn't applicable to compounds with only one central atom.
Wed Dec 04, 2019 2:47 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Rotation and Ligands
Replies: 1
Views: 32

### Re: Rotation and Ligands

I think that, if stability hasn't been reached yet (i.e. two bonded atoms can potentially become stabler), pi bonds can help stabilize a bond between two atoms.
Wed Dec 04, 2019 2:45 am
Forum: Lewis Acids & Bases
Topic: HW Problem 6.13
Replies: 1
Views: 43

### Re: HW Problem 6.13

a) All the bonds are single, so resonance isn't relevant.
b) Lewis acid. Just by following the table you see that the product of proton transfer is B(OH)4, which means B(OH)3 receives electrons and is thus a Lewis acid.
Wed Dec 04, 2019 2:43 am
Forum: Conjugate Acids & Bases
Topic: 6.21
Replies: 1
Views: 57

### Re: 6.21

Both oxygen atoms have two bonds, which means their octet is filled and they're stabler. Adding a proton would throw them off that stability. Btw, this question isn't on the syllabus, so maybe don't worry too much about it
Wed Dec 04, 2019 2:37 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: J.17
Replies: 4
Views: 107

### Re: J.17

It's mostly a matter of knowing the table of anions and cations. This includes rules that Prof Lavelle gave (e.g. knowing the cations from Groups 1 and 2)
Wed Dec 04, 2019 2:35 am
Forum: Conjugate Acids & Bases
Topic: 6.13 Homework
Replies: 1
Views: 48

### Re: 6.13 Homework

a) Resonance isn't important. All bonds are single.
b) Lewis acid, because it accepts the anionic compound OH- from H2O. (This can be concluded from the table in the book; there it gives B(OH)4 as the product in proton transfer equilibrium).
Wed Dec 04, 2019 2:31 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.1
Replies: 3
Views: 117

### Re: 6B.1

The pH equation is -log([H+]). The equation for change is -log(change in concentration / original concentration). In this case: -log(0.12*[HCl] / [HCl]). We don't need the actual value of [HCl], we can just assume it's 1 to represent the original value. Thus, we have -log(0.12) = 0.92
Wed Dec 04, 2019 2:26 am
Forum: Bronsted Acids & Bases
Topic: Self-test J.2B
Replies: 2
Views: 61

### Re: Self-test J.2B

The HPO4 doesn't seem to fit here. It'd be best to use H3PO4. Also, Ca has a 2+ charge, so calcium hydroxide is actually Ca(OH)2. Using these compounds, the reaction will look like this: 2 H3PO4 + 3 Ca(OH)2 -> Ca3(PO4) + 6 H2O
Wed Dec 04, 2019 2:12 am
Forum: Bronsted Acids & Bases
Topic: Identifying Bronsted acids and bases
Replies: 4
Views: 90

### Re: Identifying Bronsted acids and bases

Sorry, for c) yeah, its because there is an OH and NH2 swapping places. Since there's no H atom transfer, not a bronsted-lowry acid&base. For d), it is a bronsted Lowry reaction because once you separate everything into the molecules, Nh4 gives one of its h atoms to nh2. Sorry about that, didn'...
Sun Dec 01, 2019 11:37 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Hemoglobin vs Myoglobin
Replies: 3
Views: 51

### Re: Hemoglobin vs Myoglobin

Hi,
Could you explain what a heme complex is? Thank you. And do myoglobins make up hemoglobin?[/quote]

It's a coordination complex formed by a Fe attached to a porphyrin (a tetradentate ligand). Myoglobins are some of the components making up a hemoglobin
Sat Nov 30, 2019 4:50 pm
Forum: Bronsted Acids & Bases
Topic: Identifying Bronsted acids and bases
Replies: 4
Views: 90

### Re: Identifying Bronsted acids and bases

DLee_3C wrote:C) and d) aren't considered bronzed-lowry reactions because there is no simple transfer of a H atom in the chemical reaction.

By that do you mean that in c) it isn't the H that is transferred, but the OH-?
Solutions manual says d) is a Bronsted reaction.
Sat Nov 30, 2019 1:51 pm
Forum: Bronsted Acids & Bases
Topic: Identifying Bronsted acids and bases
Replies: 4
Views: 90

### Identifying Bronsted acids and bases

Exercise 6A.9 asks to identify which of the reactions below occur between Bronsted acids and bases. I have no problem identifying which compound is donating or accepting a proton. I'm confused on c) and d) mostly. How do I know c) isn't a Bronsted reaction? I thought it was because there is a transf...
Fri Nov 29, 2019 3:26 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Hemoglobin vs Myoglobin
Replies: 3
Views: 51

### Re: Hemoglobin vs Myoglobin

They're both red proteins. A Fe atom bound to 4N forms a heme complex, and a heme complex bound to a protein forms a myoglobin (which transports O2 in muscle cells). Four myoglobin-like molecules exist in each hemoglobin, binding four O2 molecules. That's pretty much everything Prof Lavelle mentione...
Fri Nov 29, 2019 3:22 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH scale
Replies: 4
Views: 70

### Re: pH scale

It can, but these substances are rare and not really relevant if you're not a chemist for example. Any pH above 9 or 10 is already considered extreme
Fri Nov 29, 2019 3:17 pm
Forum: Student Social/Study Group
Topic: Midterm 2a
Replies: 4
Views: 77

### Re: Midterm 2a

You don't have to use the combined equation -- you can do first E = h.v and then c = lambda.v (when using E=h.v remember to convert kJ to J and find the energy per atom, as the work function given is per mol). But if you're interested in using the combined equation, simply single out v in the second...
Fri Nov 29, 2019 2:40 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Exam Location
Replies: 11
Views: 162

### Re: Final Exam Location

Prof Lavelle will talk about this in class and send an email later on like he did with the midterm. It's probably going to be the same and we'll be split by last name.
Fri Nov 29, 2019 11:59 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 3
Views: 36

### Re: Ligands

The central atom isn't a ligand -- the ligand is a structure that will bond to a central atom. The ligand needs to have a lone pair available for bonding with the central atom.
Fri Nov 29, 2019 11:55 am
Forum: Octet Exceptions
Topic: 2.27
Replies: 7
Views: 233

### Re: 2.27

Fri Nov 29, 2019 11:53 am
Forum: Hybridization
Topic: Reason for 1 sigma and multiple pi bonds
Replies: 3
Views: 39

### Re: Reason for 1 sigma and multiple pi bonds

A double or triple bond can only be formed if orbitals from the two bonding atoms overlap side by side, otherwise there'd be no space for electron bonding. This side by side alignment is a pi bond -- that's why in a non-single bond, the first bond is sigma and the rest are necessarily pi.
Mon Nov 18, 2019 11:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polarity
Replies: 5
Views: 88

### Re: polarity

CH2Cl2 is a tetrahedral molecule, and tetrahedral molecules are only nonpolar if all bonded atoms are the same. The Cl pair is causing polarity to one direction and there isn't another opposing Cl pair.
Mon Nov 18, 2019 8:32 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: CHI3 vs CHF3
Replies: 2
Views: 86

### Re: CHI3 vs CHF3

Tai Metzger 3K wrote:Hi Chloe! CHI3 had a higher boiling point because it has many more electrons and is much larger, causing the london dispersion forces to be greater than the dipole-dipole interactions of CHF3.

I thought F's high electronegativity would overcome dispersion forces?
Mon Nov 18, 2019 8:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Square pyramidal
Replies: 3
Views: 47

### Re: Square pyramidal

Probably yes, as Prof Lavelle did not mention anything about not having this shape on exams.
Mon Nov 18, 2019 8:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: XeF2 Bond Angle and Shape
Replies: 2
Views: 34

### Re: XeF2 Bond Angle and Shape

The lone pairs *are* pushing the bonded atoms, it's just that they do so in a way that the resulting electron arrangement shape is trigonal bipyramidal. This is possible because there are three electron pairs and two bonded atoms. If it had only two electron pairs and two bonded atoms, then the shap...
Mon Nov 18, 2019 8:11 pm
Forum: Dipole Moments
Topic: define
Replies: 1
Views: 41

### Re: define

Dipole is a result of two opposite charges exerting force on each other. The word dipole refers to the existence of two poles caused by two different charges.
Mon Nov 18, 2019 8:09 pm
Forum: Ionic & Covalent Bonds
Topic: Lone pairs
Replies: 4
Views: 71

### Re: Lone pairs

Because they cause strong repulsion, so there will be a certain arrangement in which they will be in balance. This is described by the shapes in the VSEPR theory
Mon Nov 18, 2019 7:55 pm
Forum: Determining Molecular Shape (VSEPR)
Replies: 2
Views: 39

### Re: Question About Linear Molecules

The three lone pairs of the central atom will repel each other as well as the bonded atoms. The resulting molecular geometry is linear and the electron arrangement is trigonal bipyramidal. The angles will be: - Between 2 lone pairs = 120 - Between a lone pair and a chlorine atom = 90 - Between chlor...
Thu Nov 14, 2019 10:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Prefixes
Replies: 2
Views: 72

### Re: Prefixes

So far the exams have given us the formula, but it's very handy and potentially important to know the prefixes. I don't know any tricks so maybe memorization is the way to go. General rule for molecules is (numerical prefix + name of first atom, numerical prefix + name of second atom with "-ide...
Thu Nov 14, 2019 10:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E1 - Molecules with bent geometry
Replies: 7
Views: 102

### 2E1 - Molecules with bent geometry

Exercise 2E.1 displays one bent molecule and one linear molecule. The answer key says that the linear molecule "may have" (not necessarily has) lone pairs of electrons on the central atom. I have a theory for why this is possible (since the textbook didn't mention this, at least not in 2E)...