Search found 50 matches

Sat Mar 14, 2020 7:32 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: HW 7.17
Replies: 1
Views: 41

HW 7.17

For part e of 7.17, I understand that the catalyst will have no effect on the overall rate if the catalyst only affects the third step. However, if the problem changed and says it only affects the first step, which is the rate-determining step, would the catalyst thus have an effect on the overall r...
Sat Mar 14, 2020 6:53 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: HW 7E.5
Replies: 2
Views: 96

HW 7E.5

How do I tell which compound is the catalyst? For example, in the homework problem 7E.5, I thought the OH was an intermediate (in addition to the other listed intermediates), rather than the catalyst. How was I supposed to know that OH is a catalyst rather than an intermediate?
Sat Mar 14, 2020 2:58 pm
Forum: General Rate Laws
Topic: HW 7C.7
Replies: 2
Views: 65

HW 7C.7

The question states: Step 1: NO + Br2 ---> NOBr2 (slow) Step 2: NOBr2 + NO ---> NOBr + NOBr (fast) Write the rate law for the formation of NOBr implied by this mechanism. I know how to write the rate law (rate=k[NO][Br2]), but I was just curious as to how to write the overall reaction, just to prepa...
Thu Mar 12, 2020 4:27 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation
Replies: 3
Views: 67

Arrhenius Equation

When do we use the Arrhenius Equation? Is the activation energy (Ea) always given?
Thu Mar 12, 2020 2:28 pm
Forum: General Rate Laws
Topic: Differential vs Integrated Rate Law
Replies: 2
Views: 93

Differential vs Integrated Rate Law

What is the difference between differential and integrated rate law? When do we use each one?
Sun Mar 08, 2020 11:43 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: largeness of species and molar entropy
Replies: 3
Views: 127

Re: largeness of species and molar entropy

I think the larger the species, the electron cloud is bigger, thus having more area for the electrons to travel, thus having more randomness and a higher degree of disorder.
Sun Mar 08, 2020 11:35 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrochemical Series
Replies: 6
Views: 186

Re: Electrochemical Series

How do we know how to determine or know the electrochemical series? Or is it just something we need to memorize?
Sun Mar 08, 2020 11:25 pm
Forum: General Rate Laws
Topic: First vs Second vs Zero Order
Replies: 7
Views: 119

First vs Second vs Zero Order

What are first, second, and zero order reactions? Like what does it mean to be a first order reaction, etc.? Why does it make a difference in kinetics?
Wed Mar 04, 2020 1:51 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.3D
Replies: 3
Views: 82

Re: 6L.3D

So, from the cell diagram, the two elements don't have to be on opposite sides of the rxn? Like since O2 and H+ on the anode side of the cell diagram doesn't have to have a half rxn of O2--->H+? I have the same question. Shouldn't the half reaction go from O2 to H+ because the cell diagram says O2(...
Sun Mar 01, 2020 11:23 pm
Forum: Balancing Redox Reactions
Topic: Writing Half-reactions
Replies: 1
Views: 73

Writing Half-reactions

Instead of writing Zn --> Zn2+ + 2e- for oxidation, can I write: Zn - 2e- --> Zn2+ ? This method seems to make more sense in my opinion because it allows me to think Zn is losing two electrons in order to form Zn2+, thus Zn minus 2 electrons. This makes the oxidation process more obvious in my opini...
Sun Mar 01, 2020 11:05 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cathode/Right & Anode/Left
Replies: 7
Views: 96

Re: Cathode/Right & Anode/Left

Anode = Left = Oxidation (Losing electrons) meanwhile Cathode = Right = Reduction (Gaining electrons)
Sun Mar 01, 2020 10:57 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Replies: 8
Views: 135

Nohemi Garcia 1L wrote:I believe you add platinum to a cell diagram when the anode and/or the cathode need a solid conductor.

How do we know/tell if the anode or cathode needs a solid conductor?
Sun Mar 01, 2020 10:55 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 12
Views: 208

Re: Salt Bridge

Is there an equation or chemical formula we have to write down for the salt bridge? Or do we just say we have a salt bridge or draw it into the cell diagram?
Sun Mar 01, 2020 10:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Delta Phi Applications
Replies: 1
Views: 42

Delta Phi Applications

What is the purpose of delta phi in terms of electrochemistry? Why do we need it or when do we use it? What's the equation aside from delta phi = phi right - phi left ?
Sun Mar 01, 2020 10:52 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Delta Phi
Replies: 1
Views: 54

Delta Phi

What is delta phi? My notes say, "delta phi is the electromotive force (emf), E, of the cell (E=cell potential)." But I don't understand this concept at all. Delta phi (as i approaches 0) = E, but what is "i"?
Sun Feb 23, 2020 8:03 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff Equation
Replies: 7
Views: 154

Van't Hoff Equation

When do we use this equation? I don't recall learning this in lecture.
Sun Feb 23, 2020 8:02 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2
Replies: 15
Views: 348

Re: Test 2

Will test 2's difficulty be more like test 1's difficulty or the midterm's difficulty?
Sun Feb 23, 2020 8:00 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Standard vs Non
Replies: 3
Views: 94

Standard vs Non

What's the difference between calculating standard cell potentials and non-standard cell potentials?
Sun Feb 23, 2020 7:58 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Spontaneity
Replies: 7
Views: 176

Re: Spontaneity

Ronak Naik wrote:Higher cell potentials will indicate a greater level of spontaneity; however, spontaneity is a thermodynamic concept. It does not relate to kinetics, and thus, will not tell us anything about the speed of a reaction.

So then what tells us about the speed of a reaction? Is it just a catalyst?
Sun Feb 23, 2020 7:56 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Numbers/States
Replies: 8
Views: 173

Oxidation Numbers/States

What's the difference between oxidation numbers and oxidation states? Also, how do I calculate oxidation numbers and why are oxidation numbers important?
Sun Feb 23, 2020 7:54 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram
Replies: 4
Views: 75

Cell Diagram

Why are cell diagrams important? Also, can someone explain cell diagrams to me? I'm super confused.
Sun Feb 23, 2020 7:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cathode vs Anode
Replies: 11
Views: 205

Cathode vs Anode

What is a cathode and what is an anode? Is cathode just always the one on the left side of the cell diagram?
Sun Feb 23, 2020 7:51 pm
Forum: Balancing Redox Reactions
Topic: Half Reactions
Replies: 12
Views: 282

Re: Half Reactions

Anisha Chandra 1K wrote:An example of some half reactions would be:

Zn(s) --> Zn2+(aq)
Cu2+(aq) --> Cu (s)

So in these examples, which one is oxidizing and which one is reducing?
Sun Feb 23, 2020 7:50 pm
Forum: Balancing Redox Reactions
Topic: What is Being Reduced?
Replies: 10
Views: 154

Re: What is Being Reduced?

Is reduction based on charges and electrons or is it based on moles?
Sun Feb 23, 2020 7:47 pm
Forum: Administrative Questions and Class Announcements
Topic: Extra Credit
Replies: 17
Views: 338

Extra Credit

Will there be any extra credit opportunities? Or any opportunities to get points to boost our grades?
Sun Feb 09, 2020 6:56 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible vs Irreversible
Replies: 7
Views: 191

Reversible vs Irreversible

Why does it matter if a system is reversible or irreversible? Does it change the formulas utilized?
Sun Feb 09, 2020 6:48 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: First Law of Thermodynamics Definition
Replies: 4
Views: 82

First Law of Thermodynamics Definition

What is the official definition of the First Law of Thermodynamics that we should know for this class? I know my notes simply say that "Internal energy of an isolated system is constant. Universe is an isolated system; therefore, energy of the universe is constant." Does the first law of t...
Sun Feb 09, 2020 6:45 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Formula
Replies: 2
Views: 58

Re: Enthalpy Formula

The formula is basically derived from each other, so I believe we could use both.

qp=delta H so
delta U = q+w ------> delta U = delta H + w
w = -p*delta V -------> delta U = delta H -p*delta V
solve for delta H so...
delta H = delta U + p*delta V
Sun Feb 09, 2020 6:39 pm
Forum: Phase Changes & Related Calculations
Topic: Heat & Temperature of Phase Changes
Replies: 5
Views: 44

Heat & Temperature of Phase Changes

Under my class notes, it states "Because heat is required during melting or boiling (phase transitional), the temperature of the sample remains constant even though heat is being supplied." Is this basically saying temperature stays constant because the heat required cancels out with the h...
Sun Feb 09, 2020 6:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.21
Replies: 3
Views: 69

4D.21

For 4D.21, I have the exact numbers and equation correct according to the book, but my final answer was different from the book answer manual. The book says the correct answer is "-138.18 kJ" but I got -709.84 kJ. Am I making a minor calculation mistake based on how I put it into the calcu...
Sun Feb 02, 2020 6:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Delta U vs Delta H
Replies: 4
Views: 39

Re: Delta U vs Delta H

Delta U is the change in internal energy; meanwhile, delta H is enthalpy, or the change in heat.
Sun Feb 02, 2020 6:14 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Standard Form of molecule
Replies: 6
Views: 105

Re: Standard Form of molecule

By standard form, is this referring to the STP vs. NTP thing?
Sun Feb 02, 2020 6:10 pm
Forum: Calculating Work of Expansion
Topic: thermodynamic equations
Replies: 3
Views: 55

Re: thermodynamic equations

Will we need to memorize all these formulas or will they be given on the formula sheet?
Sun Feb 02, 2020 6:09 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Useful Summary of Thermodynamic Definitions
Replies: 46
Views: 15185

Re: Useful Summary of Thermodynamic Definitions

Why does it matter if something is a state function or not? How does it affect the problem/question? I'm very confused.
Sun Feb 02, 2020 6:08 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Pressure in an open beaker
Replies: 12
Views: 119

Re: Pressure in an open beaker

Is the constant pressure being referred to by everyone just 1 atm? Or will the actual pressure be given with the question?
Sun Jan 26, 2020 6:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Best method for reaction enthalpies
Replies: 2
Views: 19

Re: Best method for reaction enthalpies

Can you elaborate on what info should be given for each method?
Sun Jan 26, 2020 6:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pressure and equilibrium
Replies: 9
Views: 86

Re: Pressure and equilibrium

Pressure does not affect the equilibrium constant. Only temperature changes the equilibrium constant.
Sun Jan 26, 2020 6:34 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: delta H and delta U
Replies: 2
Views: 20

Re: delta H and delta U

What is the difference between delta H and delta U?
Sun Jan 26, 2020 6:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond vs Standard Enthalpies
Replies: 1
Views: 28

Bond vs Standard Enthalpies

Are there different ways to calculate or determine the bond enthalpy versus the standard enthalphy?
Sun Jan 26, 2020 6:25 pm
Forum: Phase Changes & Related Calculations
Topic: Why does steam cause burns?
Replies: 29
Views: 371

Re: Why does steam cause burns?

I also believe that, through the diagram that he showed in lecture, steam is hotter than liquid because the temperature was much higher above 100 degrees, meanwhile the liquid for temperature went between 0 degrees and 100 degrees.
Mon Jan 20, 2020 4:50 pm
Forum: Student Social/Study Group
Topic: test 1
Replies: 7
Views: 96

Re: test 1

The test is in your chem discussion. The points are usually based on the amount of time given. I believe this test should be 50 points (so 50 mins to take it) and about 7-8 questions long.
Mon Jan 20, 2020 4:44 pm
Forum: Ideal Gases
Topic: Acid and Bases
Replies: 16
Views: 165

Acid and Bases

To clarify, what is the pH scale for acidity? The most acidic is a lower pH, meanwhile the more basic is a higher pH right?
Mon Jan 20, 2020 4:41 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Replies: 7
Views: 68

Adding a catalyst will not change the equilibrium concentrations. A catalyst simply speeds things up, so equilibrium will be reached quicker.
Mon Jan 20, 2020 4:40 pm
Forum: Ideal Gases
Topic: PV=nRT
Replies: 13
Views: 159

Re: PV=nRT

You can use the ideal gas law (PV=nRT) with concentration as well because Molarity is mol/liter, which is also what n/v is (if you divide V over to the right side).

PV=nRT --> P= (n/v)RT
Mon Jan 20, 2020 4:38 pm
Forum: Ideal Gases
Topic: Equilibrium Constant
Replies: 7
Views: 77

Equilibrium Constant

For a small equilibrium constant (K<10^-3), it favors the reactants so more reactants are produced. Why?
Sun Jan 12, 2020 11:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units for K
Replies: 21
Views: 246

Re: Units for K

K has no units because of "activity"; however, activity is really low (close to 1) for the most part, so the equation ratio is simplified to the form that we know. But also, in the ratio, the units in the numerator and denominator will cancel out.
Sun Jan 12, 2020 11:56 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert gas
Replies: 6
Views: 66

Re: Inert gas

To clarify, by "inert gas", you guys are referring to mostly helium and the noble gasses right? These are inert gasses because they will not react due to their full valence shells?
Sun Jan 12, 2020 11:55 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Partial Pressure
Replies: 19
Views: 151

Re: Partial Pressure

Can partial pressure be measured in bars and atm or just bars?
Sun Jan 12, 2020 11:54 pm
Forum: Ideal Gases
Topic: Q vs. K
Replies: 10
Views: 115

Re: Q vs. K

Q is focused on the reactants and products that are gasses or aqueous solutions, meanwhile K can be for all forms including solids I believe.
Sun Jan 12, 2020 7:17 pm
Forum: Ideal Gases
Topic: Le Chatelier's Principle
Replies: 7
Views: 262

Le Chatelier's Principle

In class, Professor Lavelle mentioned Le Chatelier's Principle. What is Le Chatelier's Principle and how does it apply to chemical equilibrium and the ideal gas law?

Sorry, I don't have a strong background in chemistry because I didn't take AP Chem and don't remember sophomore year's chemistry.