Search found 61 matches

by ian_haliburton_1f
Wed Mar 13, 2019 1:55 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: What is an intermediate?
Replies: 3
Views: 22

Re: What is an intermediate?

The intermediate will appear only in the elementary reactions (steps of the proposed reaction mechanism) but will cancel out when you write the overall balanced reaction. They are products of an elementary reaction that are fully used up as reactants in a subsequent elementary reaction.
by ian_haliburton_1f
Wed Mar 13, 2019 1:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum in Cell Diagram
Replies: 7
Views: 43

Re: Platinum in Cell Diagram

Platinum is written in the cell diagram to indicate that a solid platinum electrode is needed to recreate a working cell. This is needed when the anode or cathode of a cell doesn’t have any conducting substances in its composition. The platinum conducts the charge to create a current.
by ian_haliburton_1f
Wed Mar 13, 2019 1:51 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 6
Views: 36

Re: Catalysts

The catalyst will appear from the beginning in the proposed reaction mechanism, but it will not appear in the overall equation because it will not be used up in the reaction and will therefore appear as both a reactant and a product in the elementary reactions, causing it to cancel out overall.
by ian_haliburton_1f
Fri Mar 08, 2019 6:02 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 2
Views: 41

Molecularity

Does anyone know the term for when 4 molecules are required to collide? In other words, what comes after termolecular?
by ian_haliburton_1f
Fri Mar 08, 2019 5:57 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Step
Replies: 5
Views: 39

Slow Step

Can someone explain to me why the slowest step in a reaction process determines the overall rate law for the reaction?
by ian_haliburton_1f
Fri Mar 08, 2019 5:54 pm
Forum: General Science Questions
Topic: 14BL [ENDORSED]
Replies: 3
Views: 292

14BL [ENDORSED]

Hi, I'm taking 14BL next quarter, and I was wondering what material from both 14A and 14B would be most beneficial for me to review over the break in preparation for the class?
by ian_haliburton_1f
Fri Mar 01, 2019 2:20 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Gas phase products
Replies: 3
Views: 17

Gas phase products

When there is a gas phase product in an open system reaction, is it safe to ignore the reverse reaction because the gas produced escapes and therefore does not react with the other products?
by ian_haliburton_1f
Fri Mar 01, 2019 2:17 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Activation Energy
Replies: 2
Views: 47

Activation Energy

Is there an easy way to tell when a chemical reaction has too high of an activation barrier to be kinetically spontaneous even though it is already known to be thermodynamically spontaneous?
by ian_haliburton_1f
Fri Mar 01, 2019 2:13 pm
Forum: General Rate Laws
Topic: Calculus Review
Replies: 8
Views: 47

Calculus Review

Does anyone know which specific differentiation and integration formulas/concepts I should review before we continue on with kinetics?
by ian_haliburton_1f
Mon Feb 25, 2019 9:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Order
Replies: 3
Views: 58

Cell Diagram Order

The textbook has a side comment in the section about cell diagram notation that says “when it is important to emphasize the spatial arrangement of an electrode, the order may reflect that arrangement, as in Cl-(aq)|Cl2(g)|Pt(s).” I understand why the platinum is on the outside, but otherwise what ma...
by ian_haliburton_1f
Thu Feb 21, 2019 9:59 am
Forum: Balancing Redox Reactions
Topic: k from lnK
Replies: 5
Views: 52

Re: k from lnK

when you have the ln of something isolated on one side of your equation, you can solve for what’s inside the ln by taking both sides and “exponentiating” them. This means you write e^()=e^() with whatever was previously on each side of the equation in the parentheses. This works because e^(ln(x)) is...
by ian_haliburton_1f
Thu Feb 21, 2019 9:55 am
Forum: Balancing Redox Reactions
Topic: Helpful acronym for Redox Rxns
Replies: 2
Views: 25

Re: Helpful acronym for Redox Rxns

Going off of this, I was previously taught another set of acronyms for redox reactions.

LEO says GER
(Loss of Electrons-Oxidation), (Gain of electrons-reduction)
The professor already introduced the LEO part, but I feel like the GER (like the lions roar) goes with it nicely.
by ian_haliburton_1f
Thu Feb 21, 2019 9:52 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Maximum potential
Replies: 1
Views: 18

Re: Maximum potential

Maybe it has to do with the fact that potential difference has to do with how positive one electrode is versus the other. When a stronger current of electrons flows, the positive electrode will attract them, which I would imagine effectively makes its charge more negative, thereby decreasing the pot...
by ian_haliburton_1f
Wed Feb 13, 2019 2:42 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Utotal
Replies: 1
Views: 41

Re: Utotal

This comes from the fact that we're treating the gas as only being able to move in 3 directions. Its molecules can move in any direction x, y or z, so we write 3/2. We ignore the possibility that it has rotational or vibrational energy, which would make this coefficient higher. Dr. Lavelle just brou...
by ian_haliburton_1f
Wed Feb 13, 2019 2:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Ideal Gases
Replies: 2
Views: 38

Re: Ideal Gases

For one thing, there are certain conditions under which gases do behave more like ideal gases and in those instances you would be able to perform calculations as we have been.For example, conditions of higher temp. and lower pressure contribute to more ideal behavior.
by ian_haliburton_1f
Wed Feb 13, 2019 2:35 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Heat and Entropy
Replies: 3
Views: 44

Re: Heat and Entropy

Since this equation for entropy change is in the form ∆S=nCln(T2/T1), you could use the "heat equation" q=nC∆T to solve for C if you know q, which you would then use for the entropy calculation.
by ian_haliburton_1f
Thu Feb 07, 2019 12:57 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy units
Replies: 3
Views: 22

Entropy units

What units (if any) do we use to measure entropy? Along those lines, do we write anything for units with degeneracy (W)?
by ian_haliburton_1f
Thu Feb 07, 2019 12:51 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity vs. Specific Heat
Replies: 2
Views: 55

Re: Heat Capacity vs. Specific Heat

Yes, you are finding the heat capacity of the calorimeter, whereas that equation corresponds to molar heat capacity. As such, you can ignore the mass of the calorimeter and just use C=q/delta T
by ian_haliburton_1f
Thu Feb 07, 2019 12:49 pm
Forum: Phase Changes & Related Calculations
Topic: ΔH
Replies: 2
Views: 28

Re: ΔH

Delta H equals qp for a system under constant pressure where the only work involved is the work of expansion. Since delta H is included for conditions in which there is usually work involved, it is more usual that delta U will equal delta H plus work.
by ian_haliburton_1f
Wed Jan 30, 2019 9:47 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Studying gases
Replies: 2
Views: 43

Studying gases

Generally speaking, are gases the most common subject of consideration in thermodynamics for chemistry?
by ian_haliburton_1f
Wed Jan 30, 2019 9:44 pm
Forum: Calculating Work of Expansion
Topic: Antiderivative of work
Replies: 1
Views: 43

Antiderivative of work

Since we can write the work function using an integral, does this mean there is some antiderivative equation that we can use to do straightforward integration?
by ian_haliburton_1f
Wed Jan 30, 2019 7:05 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy and Titration
Replies: 1
Views: 37

Re: Internal Energy and Titration

I believe that volume change in calculations of internal energy is only relevant to gas phase reactions. This is why work, which affects internal energy, can be written in a form that includes delta v, the change in volume.
by ian_haliburton_1f
Thu Jan 24, 2019 12:24 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Calculating Q
Replies: 11
Views: 92

Re: Calculating Q

You calculate Q when you are not sure whether the reaction is at equilibrium. If you already know the reaction’s K value, you can use the same formula for K at any time, even when the reaction is not at equilibrium, and call the calculated value Q. Its value relative to K (whether it is less than K ...
by ian_haliburton_1f
Thu Jan 24, 2019 12:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Definition Clarification
Replies: 2
Views: 33

Re: Enthalpy Definition Clarification

I believe that changing the volume of a container in which the reaction occurs would change the pressure (therefore pressure would not be constant) of the gases in said container according to the equation P=(nRT)/V.
by ian_haliburton_1f
Thu Jan 24, 2019 12:17 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: endothermic vs exothermic
Replies: 6
Views: 67

Re: endothermic vs exothermic

The term exothermic is used to denote reactions that release energy in the form of heat when they are carried out. Conversely, endothermic denotes reactions that require energy (which they acquire by absorbing heat from surroundings) to be carried out.
by ian_haliburton_1f
Thu Jan 17, 2019 3:42 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem 14b weekly homework
Replies: 2
Views: 38

Re: Chem 14b weekly homework

Just showing your work is fine. Make sure to write down the question number though (e.g. 5C.1).
by ian_haliburton_1f
Thu Jan 17, 2019 3:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Review of Weak Bases
Replies: 2
Views: 46

Review of Weak Bases

Now that we are doing acid-base equilibrium, I was specifically wondering if anyone had a concise set of guidelines for identifying a weak base compared to a strong base as I am particularly foggy in my memory of that.
by ian_haliburton_1f
Thu Jan 17, 2019 3:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How temperature affects K
Replies: 4
Views: 38

Re: How temperature affects K

I am fairly certain that this has to do with principles of thermodynamics that we will study later in the course.
by ian_haliburton_1f
Wed Jan 09, 2019 3:47 pm
Forum: Ideal Gases
Topic: Units
Replies: 5
Views: 43

Re: Units

I believe you can also use other units for pressure (such as atm or Torr) as long as you adjust the value and units of the constant R accordingly? There is a table for values of R based on which units are used.
by ian_haliburton_1f
Wed Jan 09, 2019 3:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kinetics and Thermodynamics
Replies: 1
Views: 28

Re: Kinetics and Thermodynamics

The equation for the equilibrium constant, which is all we’ve been working with so far, can be derived to the same point using either a kinetic consideration or a thermodynamic consideration. There is a thorough explanation of what these both entail at the end of topic 5G, but I believe the technica...
by ian_haliburton_1f
Wed Jan 09, 2019 3:36 pm
Forum: Ideal Gases
Topic: pressure notation
Replies: 2
Views: 48

Re: pressure notation

It is notation for standard pressure, which is 1 bar. It is included in the equation for the equilibrium constant only as a formality to make sure all the units cancel out.
by ian_haliburton_1f
Wed Dec 05, 2018 5:53 pm
Forum: Bronsted Acids & Bases
Topic: Glucose as an acid
Replies: 3
Views: 32

Glucose as an acid

Is glucose a Bronsted acid considering that it contains several hydrogen ions? If so, is it a weak acid or a strong acid? Does this have anything to do with the condition ketoacidosis?
by ian_haliburton_1f
Wed Dec 05, 2018 5:49 pm
Forum: Identifying Acidic & Basic Salts
Topic: group 1 and 2 anions
Replies: 1
Views: 22

Re: group 1 and 2 anions

Cations in these groups only have charges of 2+ or 1+, which is not often a high enough charge (unless you’re talking about transition metals with such charges) to break other molecules’ bonds and bond with them. For example, a sodium cation’s 1+ Charge is not enough to break oxygen’s bond with hydr...
by ian_haliburton_1f
Wed Dec 05, 2018 5:38 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Single Bonds of Coordination Compounds
Replies: 1
Views: 50

Re: Single Bonds of Coordination Compounds

When coordinating, the oxygen in the water molecule is making three single bonds, making its formal charge already positive. It will not trade its remaining lone pair for another bond as its formalcharge would increase even more.
by ian_haliburton_1f
Fri Nov 30, 2018 4:18 pm
Forum: Biological Examples
Topic: Coordination compounds and the nervous system [ENDORSED]
Replies: 1
Views: 64

Coordination compounds and the nervous system [ENDORSED]

Just out of curiousity, are there any coordination compounds that are critical to the functioning of the nervous system, just as heme structures are critical to the circulatory system?
by ian_haliburton_1f
Fri Nov 30, 2018 4:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Pentagonal bipyramidal
Replies: 4
Views: 47

Pentagonal bipyramidal

The textbook lists pentagonal bipyramidal as a possible molecular geometry, but I don’t believe that any of the examples we’ve done have had this shape. Is it super rare? What would be an example of a molecule with this shape?
by ian_haliburton_1f
Fri Nov 30, 2018 4:11 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Physical properties of acids and bases
Replies: 1
Views: 27

Physical properties of acids and bases

What is it, on a molecular level, that gives acids and bases their distinctive qualities. For example, what does the concentration of hydronium ions have to do with the sourness of acidic substances and what do hydroxide ions have to do with the soapy feel of bases?
by ian_haliburton_1f
Fri Nov 23, 2018 11:22 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: Distinctions between intermolecular forces
Replies: 2
Views: 50

Distinctions between intermolecular forces

Will we need to know the nuances of what distinguishes induced dipole induced dipole, London dispersion force and Van Der Waals force? They were grouped together in the lecture.
by ian_haliburton_1f
Fri Nov 23, 2018 11:20 am
Forum: Administrative Questions and Class Announcements
Topic: Test 3
Replies: 10
Views: 169

Test 3

Will there be any calculation heavy elements to this third test as there was with the last two?
by ian_haliburton_1f
Fri Nov 23, 2018 11:18 am
Forum: Administrative Questions and Class Announcements
Topic: Homework for week 9
Replies: 11
Views: 133

Homework for week 9

Can we staple all 14 problems together or should we turn in two sets of seven, labeled separately as homeworks 8 and 9?
by ian_haliburton_1f
Fri Nov 16, 2018 6:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: analysis of non-polar molecules without vectors
Replies: 2
Views: 26

analysis of non-polar molecules without vectors

Dr. Lavelle described a way to think about non polar molecules that doesn’t require drawing vector diagrams. I remember something about interactions with an electric field, but otherwise the concept was lost on me. I would appreciate if someone could elucidate this.
by ian_haliburton_1f
Fri Nov 16, 2018 6:40 pm
Forum: Dipole Moments
Topic: Definition of a dipole
Replies: 2
Views: 66

Re: Definition of a dipole

We talk about dipoles as a way to explain the differences in charges between parts of a molecule relative to the distance between them. This is used to illustrate that there is a subtle distortion/ attraction of electrons towards whatever part has a partial negative charge.
by ian_haliburton_1f
Fri Nov 16, 2018 6:37 pm
Forum: Electronegativity
Topic: Question about what makes something ionic
Replies: 5
Views: 68

Re: Question about what makes something ionic

Numerically speaking, have you checked to see if the difference is greater than 2? Otherwise there’s a good deal of room for ambiguity that can only be resolved experimentally.
by ian_haliburton_1f
Tue Nov 13, 2018 6:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecules with the same molecular formula
Replies: 1
Views: 29

Molecules with the same molecular formula

In lecture last week, Dr. Lavelle pointed out two molecules that have the same molecular formula but are referred to by different names because they have different shapes. How would one differentiate between two possibilities when the formulas are the same?
by ian_haliburton_1f
Tue Nov 13, 2018 6:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Visualizing Molecules
Replies: 1
Views: 30

Visualizing Molecules

Can anyone recommend an interactive online resource for visualizing different molecular shapes in 3D?
by ian_haliburton_1f
Tue Nov 13, 2018 6:29 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 4
Views: 134

Midterm

When the midterm is returned, will there be comments on any portions where we lost points so that we can consider what we did wrong?
by ian_haliburton_1f
Sat Nov 03, 2018 11:51 pm
Forum: Lewis Structures
Topic: Lewis Structures of acids and bases
Replies: 1
Views: 32

Re: Lewis Structures of acids and bases

The reasons for both cases have to do with formal charges. For b), Phosphate has 5 valence electrons, so you're trying to get the formal charge to equal 5 minus 5 in some way. In the structure of the Hydrogen phosphate ion, Phosphate achieves a formal charge of zero by making 5 bonds. If it were to ...
by ian_haliburton_1f
Sat Nov 03, 2018 11:38 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Au question
Replies: 1
Views: 41

Re: Au question

The 6s electron is still the most energized in the atom, and it is furthest away from the nucleus, being the only n=6 state electron. So, it will be easiest to separate from the atom altogether.
by ian_haliburton_1f
Sat Nov 03, 2018 11:32 pm
Forum: Octet Exceptions
Topic: Radicals
Replies: 3
Views: 31

Re: Radicals

It is because radicals are so unstable that they will only exist for a very short time before reacting with something else in an effort to regain stability. This intense reactivity is what makes them dangerous to things like the body's cells, for example.
by ian_haliburton_1f
Fri Oct 26, 2018 5:22 pm
Forum: *Shrodinger Equation
Topic: Quantum spin number and wave function
Replies: 1
Views: 84

Quantum spin number and wave function

Is it correct that the values of the quantum spin number have nothing to do with the wave function? I remember the later experiment with electrons and magnetism described in the text, but how is the value 1/2 derived?
by ian_haliburton_1f
Fri Oct 26, 2018 5:14 pm
Forum: Lewis Structures
Topic: Lewis Structures vs. Line Structures
Replies: 2
Views: 31

Lewis Structures vs. Line Structures

Will we be drawing line structures in this course as well? Regardless, what is the benefit of each system for representing bonds compared to the other?
by ian_haliburton_1f
Fri Oct 26, 2018 4:52 pm
Forum: Quantum Numbers and The H-Atom
Topic: Principal Quantum Number - Periodic Table
Replies: 2
Views: 57

Re: Principal Quantum Number - Periodic Table

This is because until it has a pair of electrons occupying it, the 4s orbital actually has less energy than the 3d orbitals. So, elements whose outermost electrons are in 4s (Potassium and Calcium) occur in the table before any of the 3d elements. To include the 3d elements in the same period as 3s ...
by ian_haliburton_1f
Sat Oct 20, 2018 4:15 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Symmetry in electron density distribution
Replies: 3
Views: 56

Re: Symmetry in electron density distribution

The asymmetry is a way of describing that there are certain spaces in the atom where it would be more likely to find an electron.
by ian_haliburton_1f
Sat Oct 20, 2018 4:12 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Indeterminacy Equation
Replies: 1
Views: 22

Re: Heisenberg Indeterminacy Equation

The equation from the book that you’re referencing uses the constant “h bar”(the typical h but with a line trough the stem of it) h bar is equal to h/2(pi). So when you substitute this you get the familiar h/4(pi).
by ian_haliburton_1f
Sat Oct 20, 2018 4:09 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: P orbital
Replies: 2
Views: 48

Re: P orbital

Dr. Lavelle stated that he will follow the convention that -1 corresponds to Px, 0 to Py and 1 to Pz.
by ian_haliburton_1f
Fri Oct 12, 2018 9:20 am
Forum: General Science Questions
Topic: Workshops
Replies: 3
Views: 134

Re: Workshops

I have heard that these sessions are helpful if you would benefit from additional structured review time on top of discussions. They can also be easier to access than office hours.
by ian_haliburton_1f
Wed Oct 10, 2018 10:45 pm
Forum: Properties of Electrons
Topic: atomic spectra
Replies: 2
Views: 37

Re: atomic spectra

Certain amounts of energy from incoming photons will excite the electrons and cause them to move to higher energy levels. Beyond a certain point, however, the electron can move far enough away from the positive nucleus that the attractive force can no longer keep it in orbit. It is when there’s enou...
by ian_haliburton_1f
Tue Oct 09, 2018 9:26 pm
Forum: Balancing Chemical Reactions
Topic: Review question L.35 in the 7th edition
Replies: 1
Views: 93

Review question L.35 in the 7th edition

If you are working through problem L.35 in the 7th edition, be advised that your copy (like mine) may contain a typo in the question. Namely, the third equation’s reactant should be Fe3Br8 instead of FeBr2, as the three equations are supposed to represent a series of reactions.
by ian_haliburton_1f
Tue Oct 02, 2018 11:57 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Excercise F13
Replies: 2
Views: 46

Re: Excercise F13

For this question, as you are given the total mass of the compound, you do not need to concern yourself with mass percentage composition. Rather, you can divide the actual available masses of the elements by their molar masses to find how many moles of each there are. This is the first step that the...
by ian_haliburton_1f
Tue Oct 02, 2018 11:50 pm
Forum: Molarity, Solutions, Dilutions
Topic: Units when calculating volume
Replies: 4
Views: 53

Re: Units when calculating volume

When solving for a value using this equation, you will need to know three other values already. So, one of the known values needed to solve will always be a concentration. This value is given in terms of moles per liter, so any other values in terms of mililiters to the equation would be off the sca...
by ian_haliburton_1f
Tue Oct 02, 2018 3:55 pm
Forum: Empirical & Molecular Formulas
Topic: Metal Hydroxides and sulfides
Replies: 2
Views: 44

Metal Hydroxides and sulfides

In the practice problem set of Fundamentals E, there is a question (E15) that requires knowledge about metal hydroxides and sulfides. It seems that if you are given a metal hydroxide’s formula, you can derive a corresponding sulfide through the hydroxide’s molar mass. I am not sure how and why works...

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