## Search found 113 matches

Sun Mar 15, 2020 7:58 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ∆U and ∆H
Replies: 1
Views: 68

### Re: ∆U and ∆H

By definition, qp = delta H. Therefore, under constant pressure, qp = delta H and w = P(delta V). We can then substitute these into the equation delta U = q + w, yielding delta U = delta H + P(delta V).
Sun Mar 15, 2020 7:56 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pH of acids
Replies: 11
Views: 300

### Re: pH of acids

A strong acid has a tendancy to dissociate in water, and therefore will have a higher concentration of H+ ions and a lower pH. In contrast, a weak acid will not dissociate as much, and will therefore have a lower concentration of H+ ions and a higher pH.
Sat Mar 14, 2020 4:58 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Partial Credit?
Replies: 3
Views: 88

### Final Partial Credit?

Since the final is administered through CCLE, it seems as though we will simply submit our answers to each question online. Is there any way that Dr. Lavelle will allow us to submit our work for partial credit? Or will the answers be multiple choice?
Sat Mar 14, 2020 3:55 pm
Forum: *Enzyme Kinetics
Topic: 7E.3
Replies: 1
Views: 64

### 7E.3

"The presence of a catalyst provides a reaction pathway in which the activation energy of a certain reaction is reduced from 125 kJ*mol^−1 to 75 kJ*mol^−1. (a) By what factor does the rate of the reaction increase at 298 K, all other factors being equal? (b) By what factor would the rate change...
Sat Mar 14, 2020 3:33 pm
Forum: *Enzyme Kinetics
Topic: Catalysts and enthalpy
Replies: 4
Views: 100

### Catalysts and enthalpy

Does the presence of a catalyst affect the enthalpy of a reaction? Why or why not?
Wed Mar 11, 2020 10:40 pm
Forum: Administrative Questions and Class Announcements
Topic: ENDGAME Review Session
Replies: 71
Views: 2737

### Re: ENDGAME Review Session

Lyndon thank you for putting so much effort into every review session and being a terrific UA! I've been going to your sessions since chem 14A and you've been so helpful. I wouldn't have passed without you. I wish you all the best!
Mon Mar 09, 2020 4:03 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7D.5 Solution
Replies: 1
Views: 30

### 7D.5 Solution

"The rate constant of the reaction between CO2 and OH2 in aqueous solution to give the HCO3- ion is 1.5 x 10^10 L*mol^-1*s^-1 at 25 C. Determine the rate constant at human body temperature (37 C), given that the activation energy for the reaction is 38 kJ*mol^-1 Is there an error in the solutio...
Sun Mar 08, 2020 8:03 pm
Forum: Balancing Redox Reactions
Topic: Redox Table
Replies: 6
Views: 54

### Re: Redox Table

You can think about it both ways. If you keep the sign of Eanode as it is, then Ecell = Ecathode - Eanode. However, if you flip the sign of Eanode since it is an oxidation, then Ecell = Ecathode + Eanode. Just be clear which method you use and you will be fine!
Sun Mar 08, 2020 8:01 pm
Forum: General Rate Laws
Topic: Graphs of rate laws
Replies: 8
Views: 68

### Re: Graphs of rate laws

The graphs for the different rate laws will all be linear, but what is plotted on the y axis varies. For a 0th order reaction, [A] vs time is linear, and the slop is equal to -k. For a 1st order reaction, ln[A] vs time is linear and the slope is equal to -k. For a 2nd order reaction, 1/[A] vs time w...
Sun Mar 08, 2020 7:54 pm
Forum: Balancing Redox Reactions
Topic: Balancing Basic Redox Reactions
Replies: 6
Views: 38

### Re: Balancing Basic Redox Reactions

For redox reactions in basic solutions, you want to follow the following steps: 1. write the half reactions 2. balance the non O and H atoms 3. Balance O by adding H2O 4. balance H by adding H2O to the side that needs H and OH- to the other side (this step is a little tricky, the reason that we add ...
Sat Mar 07, 2020 4:34 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: 6O.1 b
Replies: 1
Views: 70

### 6O.1 b

"A 1.0 m NiSO4(aq) solution was electrolyzed by using inert electrodes. Write (a) the cathode reaction; (b) the anode reaction. (c) With no overpotential at the electrodes, what is the minimum potential that must be supplied to the cell for the onset of electrolysis?" For part b, I underst...
Fri Mar 06, 2020 10:13 am
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: 6N.21
Replies: 2
Views: 78

### 6N.21

"(a) What is the approximate chemical formula of rust? (b) What is the oxidizing agent in the formation of rust? (c) How does the presence of salt accelerate the rusting process?"

Are we supposed to be able to solve for this mathematically, or should we memorize it form the reading?
Tue Mar 03, 2020 12:52 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.15
Replies: 1
Views: 50

### 6N.15

"Calculate the potential of a cell constructed with two nickel electrodes. The electrolyte in one compartment is 1.0 m Ni(NO3)2(aq). In the other compartment, NaOH has been added to a Ni(NO3)2 solution until the pH 5 11.0 at 298 K. See Table 6I.1." Can someone explain how to approach this ...
Sun Mar 01, 2020 2:58 pm
Forum: Balancing Redox Reactions
Topic: 6L.9
Replies: 3
Views: 71

### 6L.9

(a) Write balanced half-reactions for the redox reaction of an acidified solution of potassium permanganate and iron(II) chloride. How do we find the half reactions here? I don't understand how this is possible since Mn and Fe have multiple possible oxidation numbers. Do we just chose the most stabl...
Sun Mar 01, 2020 2:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Homework 6L.9
Replies: 4
Views: 73

### Re: Homework 6L.9

So if we start off with an equation: 2KMnO4 + 8FeCl2 --> 2KCl + 2MnCl2 + 8FeO + 5Cl2. Through this equation you would see that your potassium value doesn't change, its charge is still +1. You also notice that the charge of Cl doesn't change and that it is still -1. That means MnO4 and Fe are your c...
Sun Mar 01, 2020 1:39 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7 a Cell Diagram
Replies: 1
Views: 37

### 6L.7 a Cell Diagram

In the solutions manual, the favorable reaction is AgBr --> Ag+ + Br- based off the standard reduction potentials. Therefore, the half reactions are: Ag+(aq) + e- --> Ag(s) (cathode) Ag(s) + Br-(aq) --> AgBr(s) + e- (anode ) This all makes sense to me, but I'm confused about the order they wrote the...
Sun Mar 01, 2020 12:35 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: ΔS of Phase Changes
Replies: 5
Views: 139

### Re: ΔS of Phase Changes

We complete this last step because we want the entropy change at that specific temperature. When we cool the species back down to the original temperature, it completes the cycle, giving up the total entropy required to change the phase at the given temperature. If we don't cool it back down, then w...
Sun Mar 01, 2020 12:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.5 b
Replies: 1
Views: 36

### 6L.5 b

b. Ce4+(aq) + I-(aq) --> I2(s) + Ce3+(aq) When writing the cell diagram, the solution writes Pt on the iodine anode side of the cell and says, "An inert electrode such as Pt is necessary when both oxidized and reduced species are in the same solution." Why do do they assume that I is in so...
Wed Feb 26, 2020 9:58 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6L.1 a
Replies: 1
Views: 42

### 6L.1 a

Calculate the standard reaction Gibbs free energy for the following cell reactions: (a) 2 Ce4+(aq) + 3 I-(aq) --> 2 Ce3+(aq) + I3-(aq), Ecell° 511.08 V How do we find n in this reaction? I tried to find the half reactions and figure out the electron transfer, but I was struggling with the oxidation ...
Mon Feb 24, 2020 8:55 pm
Forum: Balancing Redox Reactions
Topic: 6K.5 a
Replies: 1
Views: 36

### 6K.5 a

Balance the following redox reaction in basic solution:
O3 + Br- --> O2 + BrO3-

I know that Br is oxidized and O is reduced. However, why do we balance O3 --> O2 in the reduction reaction? Both have an oxidation number of 0 so I don't understand how to balance it.
Mon Feb 24, 2020 4:59 pm
Forum: Balancing Redox Reactions
Topic: 6K.3 d
Replies: 2
Views: 35

### 6K.3 d

Question 6K.3 d asks use to balance the following redox reaction in acidic solution: Cl2(g) --> HClO(aq) + Cl2(g) It doesn't seem possible for there to be two half reactions in this equation, given that Cl2 is on both sides. Is there a typo in this problem? Should Cl2 in the products be Cl-? This wo...
Sun Feb 23, 2020 6:01 pm
Forum: Balancing Redox Reactions
Topic: Oxidation number of H
Replies: 6
Views: 79

### Re: Oxidation number of H

Hydrogen typically has an oxidation number of +1, but has an oxidation number of -1 when bounded to a cation or a metal.
Sun Feb 23, 2020 5:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: neg vs pos
Replies: 9
Views: 58

### Re: neg vs pos

If the voltage is positive, the reaction will occur spontaneously, and therefore creates a working battery. If the voltage is negative, the reaction does no occur spontaneously, and therefore does not create a working battery.
Sat Feb 22, 2020 11:19 pm
Forum: Van't Hoff Equation
Topic: H and S temperature dependence [ENDORSED]
Replies: 1
Views: 70

### H and S temperature dependence[ENDORSED]

When deriving the Van't Hoff equation in the book, they write, "It is usually reasonable to assume that delta H and delta S are both approximately independent of temperature over the range of temperatures of interest." However, in our other equations they both are dependent of temperature ...
Sat Feb 22, 2020 10:30 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff equation
Replies: 10
Views: 221

### Van't Hoff equation

Is the Van't Hoff Equation on the equation sheet, or do we need to derive it? I didn't see it on the sheet but I may just be blind
Sat Feb 22, 2020 9:08 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5G.15
Replies: 3
Views: 47

### 5G.15

For 5G.15, I got -2.7 kJ/mol, but the solutions manual said the answer is -27 kJ/mol. I typed it into my calculator multiple times and still go the same thing. Is there an error in the solutions manual? Thanks!
Sun Feb 16, 2020 4:59 pm
Forum: Balancing Redox Reactions
Topic: oxidation vs reduction
Replies: 19
Views: 222

### Re: oxidation vs reduction

When a compound looses electrons, it undergoes oxidation, and when it gains electrons, it undergoes reduction. You can tell this by looking at the chemical equation and tracking the electron changes
Sun Feb 16, 2020 4:54 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Delta s = 0
Replies: 8
Views: 162

### Re: Delta s = 0

As said above, delta S of the universe will equal zero in a reversible expansion. In addition, delta S of the surroundings will equal zero in an isothermal, reversible, free expansion. This is because isothermal indicates that U = 0, free expansion indicates that w = 0, so q = 0. Since q = 0, then S...
Tue Feb 11, 2020 4:59 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: S = q/T
Replies: 5
Views: 61

### S = q/T

When using S = q/T, does the temperature need to be constant? Thanks in advance!
Tue Feb 11, 2020 2:06 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 4I.5
Replies: 1
Views: 28

### 4I.5

"Suppose that 50.0 g of water at 20.0 8C is mixed with 65.0 g of water at 50.0 8C at constant atmospheric pressure in a thermally insulated vessel. Calculate DS and DStot for the process." When calculating the final temperature of the water mixture, the book used calorimetry to state that ...
Mon Feb 10, 2020 11:33 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: 4H.9
Replies: 1
Views: 34

### 4H.9

"Container A is filled with 1.0 mol of the atoms of an ideal monatomic gas. Container B has 1.0 mol of atoms bound together as diatomic molecules that are not vibrationally active. Container C has 1.0 mol of atoms bound together as diatomic molecules that are vibrationally active. The container...
Sun Feb 09, 2020 8:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: finding pH from concentration of H30+
Replies: 2
Views: 38

### Re: finding pH from concentration of H30+

The equation pH = -log[H30+] assumes that the concentration of H30+ in an acid ranges between 1 and 10^-14. If the concentration is greater than 1, the acid is extremely strong, and therefore has a negative pH.
Sun Feb 09, 2020 8:07 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cv Cp
Replies: 3
Views: 35

### Re: Cv Cp

Julia Holsinger_1A wrote:For constant pressure the equation is W= -P(delta)V , what is the equation for constant volume?

This is the equation for work, not Cv or Cp. However since (delta)V = 0 at constant volume, then w = 0. Therefore, the system does no work
Tue Feb 04, 2020 5:33 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4E.9
Replies: 6
Views: 88

### 4E.9

Benzene is more stable and less reactive than would be predicted from its Kekulé structures. Use the data in Table 4E.3 to calculate the lowering in molar energy when resonance is allowed between the Kekulé structures of benzene. When we calculate the molar energy without resonance, we get 2880 kJ, ...
Mon Feb 03, 2020 11:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.9
Replies: 1
Views: 30

### 4D.9

In the solution for 4D.9, the enthalpy density (enthalpy change per liter) of the reaction of TNT and oxygen is positive. However, delta H for the reaction is negative. Why is the enthalpy density positive but delta H is negative? Thanks in advance
Mon Feb 03, 2020 12:15 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4C.3 b
Replies: 1
Views: 57

### 4C.3 b

Calculate the final temperature and the change in enthalpy when 765 J of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (b) at constant volume. Treat the gas as ideal. In the book, it gives us the the enthalpy change at constant pressure is equal to the heat absorbed or lost,...
Sun Feb 02, 2020 10:06 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed System
Replies: 7
Views: 98

### Re: Closed System

Yes. The car releases exhaust, so gasoline is leaving the system. Therefore, it is open
Sun Feb 02, 2020 10:05 pm
Forum: Calculating Work of Expansion
Topic: Enthalpy
Replies: 5
Views: 29

### Re: Enthalpy

This means that values of enthalpy can be added/subtracted to find the change in enthalpy, as we do in Hess's law. This is because enthalpy is a state function, so the path to get there does not matter.
Sun Feb 02, 2020 9:58 pm
Forum: Ideal Gases
Topic: Temperature
Replies: 17
Views: 151

### Re: Temperature

Most questions will require you to convert to Kelvin, since this is the S.I. unit. However, if the question asks for the change in temperature, delta T, then it's unnecessary to change the units. This is because Celsius and kelvin have the same magnitude, so the change in temperature will be the same.
Sat Feb 01, 2020 12:31 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Ideal Gases: Heat Capacity
Replies: 2
Views: 29

### Ideal Gases: Heat Capacity

Do we need to know how to find the heat capacities of ideal gases? For example, in the book it covers that the heat capacity of a monotonic ideal gas under constant volume is equal to (3/2)R. This was covered in the book but not in lecture, so I was wondering if it's important? Thanks!
Fri Jan 31, 2020 7:22 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4A.5
Replies: 1
Views: 34

### 4A.5

A piston confines 0.200 mol Ne(g) in 1.20 L at 25 8C. Two experiments are performed. (a) The gas is allowed to expand through an additional 1.20 L against a constant pressure of 1.00 atm. (b) The gas is allowed to expand reversibly and isothermally to the same final volume. Which process does more w...
Sun Jan 26, 2020 3:18 pm
Forum: Phase Changes & Related Calculations
Topic: protonation v ionization
Replies: 2
Views: 20

### Re: protonation v ionization

Prioritization occurs when a base gains an H+ molecule in a chemical reaction, therefore gaining a proton. Ionization is when an acid looses an H+ molecule in a chemical reaction, and therefore becomes negatively charged.
Sun Jan 26, 2020 3:15 pm
Forum: Phase Changes & Related Calculations
Topic: State property
Replies: 6
Views: 55

### Re: State property

A state property is a property that is not dependent on the path taken to get to that state. Therefore, it's value is only determined by it's current state. For example, volume is a state property because it doesn't matter how that volume was obtained, so it's value is only determined by it's curren...
Sun Jan 26, 2020 3:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Lewis Structures
Replies: 4
Views: 52

### Re: Lewis Structures

To draw the Lewis structure of a compound, count the number of valence electrons present in each atom. Then chose the atom with lowest ionization energy as the central atom, and arrange the atoms symmetrically around the central atom. Then arrange the electrons so that each atom has a full octet, ad...
Thu Jan 23, 2020 6:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6D.15 b
Replies: 1
Views: 40

### 6D.15 b

Calculate the pH of (b) 0.055 m AlCl3(aq).

In the solutions manual, the chemical equation they used was
Al(H2O)63+ +H2O <--> H3O+ + Al(H2O)5OH2+

Can someone explain how they got this equation? I'm confused.
Thu Jan 23, 2020 6:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6D.13
Replies: 1
Views: 33

### 6D.13

Rank the following solutions in order of increasing pH: (a) 1.0 x 10^-5 m HCl(aq); (b) 0.20 m CH3NH3Cl(aq); (c) 0.20 m CH3COOH(aq); (d) 0.20 m C6H5NH2(aq). Justify your ranking.

Is there a way to do this problem without doing an ice table for each one, or is that the best way to do this?
Sun Jan 19, 2020 3:19 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Effect of Temperature on K
Replies: 2
Views: 31

### Re: Effect of Temperature on K

Changing the temperature affects the value of K because it affects whether the reaction favors reactants or products. If the reaction is endothermic, it absorbs heat. Therefore, increasing the temperature means that it will favor the formation of products to use up the additional heat, increasing th...
Sun Jan 19, 2020 3:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Change in Pressure?
Replies: 2
Views: 36

### Re: Change in Pressure?

It's important to remember that the actual value of K does not change unless the temperature of the reaction is changed. Therefore, when you change the pressure, the K value does not change. However, changes in pressure mean that the system at that point in time will not be at equilibrium partial pr...
Sun Jan 19, 2020 3:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: autoprotolysis
Replies: 5
Views: 41

### Re: autoprotolysis

The autoprotolysis of water occurs when water molecules react with each other to form OH- and H3O+. The equation is 2H2O(l) <--> OH- + H3O+. Since water is a pure liquid, the equilibrium expression for this reaction is Kw = [OH-] [H3O+]. In order to calculate the value of Kw, we must remember that w...
Sat Jan 18, 2020 10:27 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.61a
Replies: 3
Views: 42

### 5.61a

5.61 The overall photosynthesis reaction is 6 CO2(g) + 6 H2O(l) -- C6H12O6(aq) + 6 O2(g), and H = 12802 kJ. Suppose that the reaction is at equilibrium. State the effect that each of the following changes will have on the equilibrium composition: tends to shift toward the formation of reactants, ten...
Thu Jan 16, 2020 11:53 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.5 d
Replies: 3
Views: 41

### 5J.5 d

State whether reactants or products will be favored by an increase in the total pressure (resulting from compression) on each of the following equilibria. If there is no change, explain why that is so. (d) 2 HD(g) ∆ H2(g) 1 D2(g) In the solutions manual, they explain that there is not change in whet...
Wed Jan 15, 2020 8:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.13 c
Replies: 1
Views: 26

### 5I.13 c

Use your results from parts (a) and (b) to determine which is thermodynamically more stable relative to its atoms at 1000. K, Cl2 or F2. The Kc for Cl2 was 1.2 x 10^-7 and the Kc for F2 was 1.2 x 10^-4. Why is Cl2 more stable than F2? Does stability just mean that the reactants (either Cl2 or F2 in ...
Thu Jan 09, 2020 1:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q versus K
Replies: 4
Views: 46

### Q versus K

Can someone explain the different between K and Q? How can Q be used to tell us the direction the reaction will proceed? Thanks in advance!
Thu Jan 09, 2020 1:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.1C
Replies: 3
Views: 54

### Re: 5G.1C

The equilibrium constant is not affected by the initial partial pressures of the reactant due to Le Chatlier's principle. This principle states that when stress is placed on the system (such as increasing the partial pressure of a reactant), then the equilibrium will shift in order to counteract tha...
Thu Jan 09, 2020 12:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K values
Replies: 4
Views: 51

### Re: K values

When K is less than 10^-3, we can say with certainty that the reaction strongly favors reactants. However when K is between 10^-3 and 1, the concentration of the reactants will be slightly higher than the concentration of the products. Therefore, I would assume that the reaction slightly favors the ...
Thu Jan 09, 2020 12:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc vs K
Replies: 6
Views: 78

### Re: Kc vs K

Kc is used when calculating the equilibrium constant using concentration, whereas Kp is used for calculating the equilibrium constant using partial pressure. However, as Dr. Lavelle explained in lecture, K can be used as an abbreviation to represent either Kc or Kp, depending on the context of the p...
Tue Jan 07, 2020 7:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.9
Replies: 3
Views: 82

### 5G.9

In the solutions for 5G.9, the book writes the equilibrium constants using the concentrations opposed to the partial pressures. However, since the products and reactants are gasses, wouldn't it be more correct to use the partial pressure? Thanks in advance
Sat Dec 07, 2019 8:52 pm
Forum: Biological Examples
Topic: Transition Metal Cations
Replies: 1
Views: 34

### Transition Metal Cations

How do transition metal cations function as enzymes? Is this important for the exam?
Sat Dec 07, 2019 8:37 pm
Forum: Biological Examples
Topic: Vitamin B12
Replies: 2
Views: 72

### Vitamin B12

What is the structure of Vitamin B12? I know that Co is the transition metal that makes up the central atom, but what is the ligand? Also, what is its biological significance and how does the structure enable vitamin B12 to perform its function? Thanks in advance
Mon Dec 02, 2019 10:25 pm
Forum: Biological Examples
Topic: Heme Complex
Replies: 2
Views: 86

### Heme Complex

In the marshmallow problems,it asks what the oxidation state of Fe in the heme complex is. How do we find this? it also asks about the porphryn ligand. What is this? Is it mono or poly dentate? Is this something we need to memorize?
Mon Dec 02, 2019 2:50 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: 6C.21
Replies: 2
Views: 146

### 6C.21

Suggest an explanation for the different strengths of (b) acetic acid and formic acid.

Can someone explain why formic acid is a stronger acid than acetic acid? Is it because is looses protons more easily? Thank you
Mon Dec 02, 2019 2:16 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: 6C.17
Replies: 2
Views: 141

### 6C.17

Which is the stronger base, the hypobromite ion, BrO2, or morphine, C17H19O3N? Justify your answer.

How would you answer this question? Thank you
Sun Dec 01, 2019 8:42 pm
Forum: Calculating the pH of Salt Solutions
Topic: Sig Figs for logarithmic funcitons
Replies: 6
Views: 136

### Sig Figs for logarithmic funcitons

How do sig figs work on logarithmic functions when doing pH calculations?
Sun Dec 01, 2019 5:37 pm
Forum: Bronsted Acids & Bases
Topic: How to tell
Replies: 4
Views: 59

### Re: How to tell

You need to look at the chemical formula and see if the molecule is more likely to accept or donate an H+ ion. Since NH3 has a lone pair on the N, it is more likely to accept a proton and is therefore considered a weak base. However, it's also good to memorize common acids and bases.
Sun Dec 01, 2019 5:29 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 6
Views: 64

### Re: Coordination Number

Jorge Ramirez_4H wrote:Is there a good way of memorizing this?

You don't need to memorize the coordination number for each coordination compound. Just look at the number of ligands in the square brackets of the chemical formula and you should be able to find it.
Sun Dec 01, 2019 5:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelate and polydentate
Replies: 2
Views: 47

### Chelate and polydentate

Can someone explain what a chelating ligand is and why it's important? Also, how is this related to a ligand being polydentate?
Sun Dec 01, 2019 5:17 pm
Forum: Naming
Topic: How to Know the Charge of Ions
Replies: 7
Views: 90

### Re: How to Know the Charge of Ions

Unfortunately, the only way to know the charge of a common poly atomic ions, such as SO4 2-, is through memorization. I recommend flashcards. And Lavelle won't give us the ligand table for naming coordination compounds, we have to memorize that as well.
Sun Dec 01, 2019 5:13 pm
Forum: Bronsted Acids & Bases
Topic: 6A.9 a
Replies: 3
Views: 81

### 6A.9 a

Which of the following can be classified as reactions between Brønsted acids and bases? For those that can be so classified, identify the acid and the base. (Hint: It might help to write the net ionic equations.) (a) NH4I(aq) + H2O(l) -> NH3(aq) + H3O1(aq) + I2(aq) Would the acid in this case be NH4...
Sun Nov 24, 2019 4:29 pm
Forum: Naming
Topic: Cyano vs cyanido
Replies: 1
Views: 24

### Cyano vs cyanido

In lecture, Lavelle mentioned that we should write cyano for CN- in cooridation compounds, but the book says we should write cyanido. Which is correct?
Sun Nov 24, 2019 2:55 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Lewis Acids
Replies: 4
Views: 48

### Re: Lewis Acids

I'm not exactly sure what you mean by regular acids, but if I understand correctly, a Lewis acid is a regular acid. A Lewis acid is simply a way to define chemically what an acid is. By definition, a Lewis acid is an electron acceptor, which provides a visual representation what what an acid does in...
Sun Nov 24, 2019 2:49 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Bronsted vs. Lewis Acids
Replies: 9
Views: 100

### Re: Bronsted vs. Lewis Acids

A Bronsted atom is a proton donor, whereas a Lewis acid is an electron acceptor. While the definition of these acids are different, they are complimentary, meaning that if a molecule is a Lewis acid it is also a Bronsted acid. Therefore, both definitions are acceptable.
Sun Nov 24, 2019 2:35 pm
Forum: Naming
Topic: Chloro vs Chloride
Replies: 3
Views: 45

### Re: Chloro vs Chloride

The suffix -ide is used for the naming of common anions. For example, Cl-1 is named "chloride," and S2- is named "sulfide." However, as Lavelle stated in lecture on Friday, when naming coordination compounds, you drop the -ide from the anion name and add the suffix -o. Therefore,...
Sun Nov 24, 2019 2:28 pm
Forum: Biological Examples
Topic: Heme complex
Replies: 8
Views: 120

### Re: Heme complex

The heme complex is an iron ion bound to a porphyrin ligand, which is a cage like molecule consisting of four tetradentate square planar nitrogen molecules. When the heme complex binds to a protein, it creates myglobin. Myglobin is important because the structure of the molecule allows the iron ion ...
Sun Nov 24, 2019 2:18 pm
Forum: Biological Examples
Topic: Cisplatin
Replies: 15
Views: 158

### Re: Cisplatin

The Cl atoms on the clisplatin molecule bind to the exposed N on two nearby (but not necessarily next to each other) guanine nucleotides, forming a coordination compound with the DNA molecule. The bound cisplatin blocks DNA replication machinery, preventing the DNA from replicating and ultimately st...
Sun Nov 17, 2019 1:00 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: Intermolecular Force Strengths
Replies: 2
Views: 43

### Intermolecular Force Strengths

Should we memorize the approximate strengths of each intermolecular force? Or is it sufficient to know the strengths relative to each other (ie knowing that hydrogen bonding is stronger than dipole-dipole, etc)
Sun Nov 17, 2019 12:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.21 d
Replies: 2
Views: 31

### 2E.21 d

IN 2E.21, the answer key says that the bond angle of N2H2 is 107 degrees. Are we expected to be able to predict this, or is saying the angle is less than 109.5 degrees sufficient?
Sun Nov 17, 2019 11:38 am
Forum: Determining Molecular Shape (VSEPR)
Topic: polar and nonpolar
Replies: 3
Views: 53

### Re: polar and nonpolar

I believe that the example of the cis and trans molecule served as an example of how two molecules with the same molecular formula but different arrangements can be either polar or non polar, depending on whether the dipole moments cancel. Since the cis molecule had the Cl atoms on the same side of ...
Sun Nov 17, 2019 11:32 am
Forum: Ionic & Covalent Bonds
Topic: Bonds strength
Replies: 4
Views: 69

### Re: Bonds strength

A double bond isn't twice as strong as a single bond because there are electron electron repulsions in the double bond that slightly reduce the strength.
Sun Nov 17, 2019 11:28 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent vs angular
Replies: 1
Views: 49

### Bent vs angular

In the book, they use the term angular, but does the term bent also apply?Thank you
Sun Nov 10, 2019 8:49 pm
Forum: Dipole Moments
Topic: 3F.13
Replies: 2
Views: 60

### 3F.13

Identify the arrangement (I, II, or III; all molecules are CH2Cl2) that should possess the strongest intermolecular attractions, and justify your selection. (there's an image in the textbook). How are we supposed to be able to tell the difference in the arrangements of these molecules? I cannot see ...
Sun Nov 10, 2019 8:43 pm
Forum: Dipole Moments
Topic: 3F.3 c
Replies: 1
Views: 26

### 3F.3 c

Which way is the dipole pointing on CHCl2? I don't understand why this molecule experiences dipole-dipole attraction. Thanks
Sun Nov 10, 2019 8:40 pm
Forum: Dipole Moments
Topic: 3F.1 d
Replies: 1
Views: 35

### 3F.1 d

Identify the types of attractive intermolecular interactions that might arise between molecules of each of the following substances: (d) SO2. The solutions manual said this molecule experiences London dispersion forces and dipole-dipole attraction. How does it have dipole-dipole attraction? Which wa...
Wed Nov 06, 2019 10:08 am
Forum: Lewis Structures
Topic: Line Drawings Outline 3
Replies: 2
Views: 47

### Line Drawings Outline 3

On outline three, it says we should be able to "Draw line structures of organic compounds." I don't remember Lavelle going over this, should we know it for the midterm?
Tue Nov 05, 2019 9:00 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic vs molecular spectroscopy: outline 2 [ENDORSED]
Replies: 1
Views: 88

### Atomic vs molecular spectroscopy: outline 2[ENDORSED]

On outline 2, the seventh bullet point says: "With respect to electron transitions that give rise to a UV or visible spectrum: understand the difference between electronic transitions in atomic orbitals (atomic spectroscopy) and electronic transitions in molecular orbitals (molecular spectrosco...
Sun Nov 03, 2019 12:40 pm
Forum: Bond Lengths & Energies
Topic: 2D.19
Replies: 1
Views: 40

### 2D.19

"Use the covalent radii in Fig. 2D.11 to calculate the bond lengths in the following molecules. Account for the trends in your calculated values: (a) CF 4; (b) SiF 4; (c) SnF 4"

Can someone explain how to do this? Thank you
Sat Nov 02, 2019 10:46 pm
Forum: Lewis Structures
Topic: Dino Nugs 12b
Replies: 5
Views: 72

### Re: Dino Nugs 12b

Does Cl04- not have any resonance structures? I thought it did have resonance, but it makes more sense to me that oxygen has the negative charge because it's more electronegative. It does have resonance structures, since three of the oxygen are double bonded to the Cl and the other has a single bon...
Sat Nov 02, 2019 10:44 pm
Forum: Octet Exceptions
Topic: 2C.3
Replies: 3
Views: 68

### 2C.3

In 2C.3 c, the book asked up to draw the Lewis Structure for chloric acid. The answer gave three structures, two of which had expanded octets. Would all of these be considered resonance structures, or is the final structure they gave (the one with lowest energy charge) technically correct? Thanks
Sat Nov 02, 2019 8:51 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Atoms to Moles
Replies: 7
Views: 240

### Re: Atoms to Moles

Yes. Since Avogadro's number is in particles/mol, dividing the number of atoms by Avogadro's number will give you the number of mols.
Sat Nov 02, 2019 8:48 pm
Forum: Resonance Structures
Topic: Delocalized electrons
Replies: 4
Views: 72

### Re: Delocalized electrons

When electrons are delocalized, it means that they aren't associated with a single atom or covalent bond. We can see this in resonance structures, where the Lewis structure can have multiple equivalent locations for a bond, such as a double bond. Here, the observed bond lengths are between the exper...
Sat Nov 02, 2019 8:36 pm
Forum: Lewis Structures
Topic: Dino Nugs 12b
Replies: 5
Views: 72

### Dino Nugs 12b

On Dino Nuggets question 12b, why does ClO4- have three double bonds and not four? I know that with three double bonds the Cl will have a formal charge of zero and the single bonded O will have a formal charge of -1, but why is this more stable than the Cl having four double bonds and a formal charg...
Sun Oct 27, 2019 11:57 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Assigning Orbitals to Elements
Replies: 4
Views: 67

### Re: Assigning Orbitals to Elements

It doesn’t matter if an electron is in the px, py, or pz orbital, but you must follow Hunds rule and ensure that each orbital is filled before electrons are paired.
Sun Oct 27, 2019 11:54 am
Forum: Trends in The Periodic Table
Replies: 11
Views: 126

### Re: atomic Radii

Yes, this is true. However, you have to remember that going across a period, the number of electrons is increasing, but so is the effective nuclear charge. Therefore, the atomic radius gets smaller across a period, but increases down a group.
Sun Oct 27, 2019 11:50 am
Forum: Trends in The Periodic Table
Topic: Question on 1F.5 b
Replies: 3
Views: 46

### Re: Question on 1F.5 b

The ionization energy is the energy it takes to remove an electron from an atom. Ionization energies are paired with atomic radius. Since atomic radius increases from left to right on the periodic table so does ionization energy. Na is to the left of Mg so this would mean that Na has the smaller at...
Sun Oct 27, 2019 11:40 am
Forum: Lewis Structures
Topic: Expanded Octet
Replies: 6
Views: 64

### Expanded Octet

Can someone please explain why certain elements can have an expanded octet?
Sun Oct 27, 2019 11:30 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Question 1E.25
Replies: 1
Views: 41

### Question 1E.25

"Give the notation for the valence-shell configuration (including the outermost d-electrons) of (c) Group 5 transition metals."

Can someone please explain this? The answer says it is (n-1)d5ns2, but i thought it was (n-1)d3ns2. Thanks!
Sat Oct 19, 2019 2:02 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Coulomb's Law
Replies: 3
Views: 45

### Coulomb's Law

Can someone help explain the significance of Coulomb's Law to me? I don't understand why Coulombs Law states that the electrostatic energy is lower at a larger distance, but electrons further from the nucleus have higher energies. These statements seem to contradict each other, so I'm confused. Than...
Fri Oct 18, 2019 3:54 pm
Forum: DeBroglie Equation
Topic: Linear Momentum
Replies: 6
Views: 103

### Re: Linear Momentum

Linear momentum is the product of the mass and velocity of an object. It is a vector quantity with units of kg*m/s, and is conserved.
Fri Oct 18, 2019 3:50 pm
Forum: Photoelectric Effect
Topic: Threshold Energy
Replies: 7
Views: 124

### Re: Threshold Energy

If the energy of the light matches the threshold energy, then electrons will be emitted from the surface. If the energy of light is greater than the threshold energy, then the electrons emitted will have increasing kinetic energy.
Tue Oct 15, 2019 10:16 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1B. 25
Replies: 1
Views: 49

### Re: 1B. 25

1.054 457x10^-34 isn't the value for h, but it is actually the value of h bar. H bar is equal to h/(2pi), and is denoted as an h with a line through the top. Although it's used in the uncertainty principle in the book, it's not necessary to know it because it's just a shorthand.
Mon Oct 14, 2019 2:23 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Problem 1B.27
Replies: 3
Views: 53

### Problem 1B.27

A bowling ball of mass 8.00 kg is rolled down a bowling alley lane at 5.00 +/- 5.0 m/s. What is the minimum uncertainty in its position? In the answer key, they used 5.00 m/s as the uncertainty in velocity (delta v). Why wouldn't the uncertainty be 10.00 m/s? I thought it would be that because 10.00...

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