Search found 51 matches

by Chris Pleman 3E
Sat Mar 17, 2018 11:15 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: why is the entropy change at constant pressure greater than the entropy change at constant volume?
Replies: 3
Views: 164

Re: why is the entropy change at constant pressure greater than the entropy change at constant volume?

Beyond the fact that C(p,m) > C(v,m), it could be that when pressure remains constant that there's no relief in the force acting on the molecules, as when volume changes pressure will change inversely. That's my best bad guess. Maybe it could have to do with the fact that (delta)S=(delta)H/T at cons...
by Chris Pleman 3E
Sat Mar 17, 2018 11:08 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Final
Replies: 3
Views: 170

Final

Beyond memorizing the names and structures of the functional groups, is there anything else we need to know about/how to do in O Chem?
by Chris Pleman 3E
Fri Mar 16, 2018 6:13 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics Formulas for the Final
Replies: 2
Views: 239

Kinetics Formulas for the Final

For the final, are we going to have to work with collision theory and its formulas (both collision frequency, relative velocity, and molar mass formulas), or do we just have to understand the concepts behind these formulas?
by Chris Pleman 3E
Sun Mar 11, 2018 7:38 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics Test Scores [ENDORSED]
Replies: 3
Views: 274

Kinetics Test Scores [ENDORSED]

For those who have discussions later on in the week (Thursday and Friday) will we be getting our tests back earlier (in class) so that we have more time to review before the final on Sunday?
by Chris Pleman 3E
Sun Mar 11, 2018 7:35 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Reversible or irreversible?
Replies: 2
Views: 231

Re: Reversible or irreversible?

Isothermal reactions should be reversible.
by Chris Pleman 3E
Thu Mar 08, 2018 1:27 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Homework Problems
Replies: 3
Views: 143

Homework Problems

Did Dr Lavelle mention the extent of the questions in the textbook that are necessary/will be covered by the Kinetics test? If so, which ones?
by Chris Pleman 3E
Sat Mar 03, 2018 3:00 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: example 15.4: Measuring a Rate Constant
Replies: 2
Views: 165

Re: example 15.4: Measuring a Rate Constant

My TA said that it could end up on Test 3 and/or the Final, but I believe he mentioned that the numbers involved wouldn't be difficult to work with.
by Chris Pleman 3E
Sat Mar 03, 2018 2:56 pm
Forum: Zero Order Reactions
Topic: Zero Order Reactions and Rate of Reaction
Replies: 5
Views: 168

Re: Zero Order Reactions and Rate of Reaction

A zero order reaction also indicates that the rate of that specific reaction is at its maximum (usually due to the introduction of an enzyme) which is why changing the concentration of the reactant will not have an effect on the rate, but only the duration.
by Chris Pleman 3E
Sat Mar 03, 2018 2:49 pm
Forum: First Order Reactions
Topic: Naming Orders
Replies: 3
Views: 122

Re: Naming Orders

Usually you can determine through the data given for each individual compound concentration's effect on the rate of the reaction.
by Chris Pleman 3E
Thu Feb 22, 2018 12:30 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Difference between galvanic and electrolytic cells
Replies: 1
Views: 67

Re: Difference between galvanic and electrolytic cells

Yes. The Flow of electrons go from negative to positive, where they leave the anode (negatively charged) because it's getting oxidized (losing electrons), and travel over to the cathode (positively charged) where the cathode is reduced (gaining/accepting electrons).
by Chris Pleman 3E
Thu Feb 22, 2018 12:28 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Oxidizing and Reducing Agents
Replies: 2
Views: 88

Re: Oxidizing and Reducing Agents

You'll find the standard cell potentials on the electrochemistry series (page 579 of textbook).
by Chris Pleman 3E
Thu Feb 22, 2018 12:27 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Concentration Cells
Replies: 2
Views: 77

Concentration Cells

How does a potential difference arise in a concentration cell if each electrode has the same substance? A conceptual explanation would be preferred.
by Chris Pleman 3E
Sun Feb 18, 2018 5:44 pm
Forum: Balancing Redox Reactions
Topic: Addition of H3O+ or OH-
Replies: 4
Views: 141

Addition of H3O+ or OH-

How can we tell when to add H3O+ or OH- when balancing half reactions, and how do we know what side of the equation to add it to?
by Chris Pleman 3E
Sun Feb 18, 2018 5:41 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Conc. Cells
Replies: 2
Views: 111

Re: Conc. Cells

Because the addition of the electron into the products cause the ions to aggregate into solids, which will accumulate on the electrode that's in the solution- so you're making more of the inert substance.
by Chris Pleman 3E
Sun Feb 18, 2018 5:40 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E equations
Replies: 3
Views: 107

Re: E equations

There isn't. Both equations are equal to each other, one simply uses a natural log, and the other uses a log base 10 and simplifies/integrates the constant into the equation required to make both equations equal.
by Chris Pleman 3E
Sun Feb 11, 2018 6:38 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Derivation of Formulas
Replies: 5
Views: 282

Derivation of Formulas

Will we be expected to derive the formulas we've learned in class on the midterm?
by Chris Pleman 3E
Sun Feb 11, 2018 6:36 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Practice Midterm [ENDORSED]
Replies: 5
Views: 353

Practice Midterm [ENDORSED]

Where can I find the practice midterm exam?
by Chris Pleman 3E
Sun Feb 11, 2018 6:36 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Practice Midterm
Replies: 1
Views: 114

Practice Midterm

Where can I find the practice midterm?
by Chris Pleman 3E
Sun Feb 11, 2018 6:31 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: Finding entropy of vaporization for water at room temp
Replies: 2
Views: 116

Re: Finding entropy of vaporization for water at room temp

It depends on the pressure acting on the system (the water). If you lower the pressure, then the energy required to vaporization should be less.
by Chris Pleman 3E
Sun Feb 04, 2018 10:24 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Transfer Test 1 Concept Question
Replies: 2
Views: 105

Re: Heat Transfer Test 1 Concept Question

If it's being held at constant temperature, increasing volume will lead to a decrease in temperature. However, to maintain a constant T, energy/heat must be supplied to the system.
by Chris Pleman 3E
Sun Feb 04, 2018 10:22 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Q or Qc when calculating Gibbs Free Energy
Replies: 1
Views: 50

Re: Q or Qc when calculating Gibbs Free Energy

If you're only provided with partial pressures then you can use that to find Q, either way, as long as you calculate Q correctly (when delta G is not equal to zero) then it shouldn't matter whether you've used partial pressures or concentrations to come to the solution. Most of the time it will depe...
by Chris Pleman 3E
Sun Feb 04, 2018 10:19 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sig Figs
Replies: 6
Views: 108

Re: Sig Figs

They shouldn't be anymore or less important than the topics we've covered in the past. However, they'll matter more on the test and/or in a lab.
by Chris Pleman 3E
Sun Jan 28, 2018 11:27 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Test question [ENDORSED]
Replies: 16
Views: 488

Re: Test question [ENDORSED]

I also put the equation (delta)E(univ)= (delta)E(sys) + (delta)E(surroundings), but I'm not sure if that was redundant in lieu of stating that matter and energy are neither created nor destroyed.
by Chris Pleman 3E
Sun Jan 28, 2018 11:21 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Exothermic vs Exergonic and Endothermic vs Endergonic
Replies: 3
Views: 769

Re: Exothermic vs Exergonic and Endothermic vs Endergonic

Exo/Endothermic represents the relative change in heat/enthalpy in a system, whereas Exer/Endergonic refers to the relative change in the free energy of a system.
by Chris Pleman 3E
Sun Jan 28, 2018 11:20 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: entropy property? [ENDORSED]
Replies: 2
Views: 98

Re: entropy property? [ENDORSED]

I think it would be extensive because it changes based on the volume, or the number of particles- these would affect the number of microstates possible.
by Chris Pleman 3E
Sun Jan 21, 2018 9:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: delta n
Replies: 3
Views: 437

Re: delta n

The focus should be on the change in moles of gaseous particles, as this is will sometimes be the cause of the change in volume (which will help you solve for work). As for whether it's Ps-Rs or vice versa, it's more or less focusing on the change in the number of moles due to how the initial and fi...
by Chris Pleman 3E
Sun Jan 21, 2018 9:02 pm
Forum: Phase Changes & Related Calculations
Topic: Test 1 [ENDORSED]
Replies: 7
Views: 294

Re: Test 1 [ENDORSED]

There should be a link posted on Lavelle's website that goes over the concepts and formulas that will be covered on the test. However, (delta)U= (delta)q + (delta)w, w = -P(delta)V, q = mC(delta)T / q = nC(delta)T (formula differs whether you're using specific heat, or molar heat capacity), are the ...
by Chris Pleman 3E
Sun Jan 21, 2018 8:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Specific enthalpy
Replies: 1
Views: 104

Re: Specific enthalpy

Beyond understanding what it means, it should be provided on the test.
by Chris Pleman 3E
Sun Jan 14, 2018 10:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Recording Lectures
Replies: 2
Views: 164

Re: Recording Lectures

You can also check any modules he has on his website.
by Chris Pleman 3E
Sun Jan 14, 2018 10:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard States
Replies: 4
Views: 187

Re: Standard States

I believe we should be told on the test, but beyond that, a table of standard enthalpy of formation would have a zero next to a compound in its standard state.
by Chris Pleman 3E
Sun Jan 14, 2018 9:02 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: q equations
Replies: 2
Views: 99

Re: q equations

The first equation applies to Molar Heat Capacity, which is designated by the Cm symbol, and why the symbol for moles ("n") is included in the formula- when solving for q, the moles will "cancel" out during dimensional analysis. Csp, on the other hand, refers to the specific heat...
by Chris Pleman 3E
Sun Dec 10, 2017 9:48 pm
Forum: Administrative Questions and Class Announcements
Topic: Final [ENDORSED]
Replies: 4
Views: 876

Re: Final [ENDORSED]

What I did was find the molarity of both the H+ and OH- ion in the 1.00 L solution, and then took the difference in molarities between the two ions, because I wanted to find the net concentration of a certain ion. I chose to find the net concentration, because I believed that the H+ and OH- ion woul...
by Chris Pleman 3E
Sun Dec 10, 2017 9:44 pm
Forum: Amphoteric Compounds
Topic: Finals Question about Glycine? [ENDORSED]
Replies: 1
Views: 434

Re: Finals Question about Glycine? [ENDORSED]

It asked whether or not it was amphiprotic, and I said yes, because the N atom had a lone pair, and the H connected to the Oxygen seemed that it would likely dissociate in a solution. Therefore, it could both gain, and donate a proton (H+ ion).
by Chris Pleman 3E
Sun Dec 03, 2017 9:39 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Noble Gas increasing pressure
Replies: 3
Views: 267

Re: Noble Gas increasing pressure

The only time the equilibrium constant will change, will be when temperature changes. All other variables like Pressure, n (moles), and Volume, do not have an effect on the constant itself.
by Chris Pleman 3E
Sun Dec 03, 2017 9:37 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Question 11.89 Part A
Replies: 2
Views: 154

Re: Question 11.89 Part A

It could possibly be that they are trying to balance the coefficients on each side, so if A is a reactant, and B and C are the products, then there needs to be two (lets say) moles on the reactant and product side of the equation.
by Chris Pleman 3E
Sun Nov 26, 2017 10:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc or Kp for a heterogenenous equilibrium?
Replies: 2
Views: 133

Re: Kc or Kp for a heterogenenous equilibrium?

You have to convert either to only gas (giving you Kp) or only molarity (Kc), so you will need to use the ideal gas law to convert from one to the other.
by Chris Pleman 3E
Sun Nov 26, 2017 10:46 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: convertine to partial pressure
Replies: 2
Views: 166

Re: convertine to partial pressure

If you already have a substance in gas form you shouldn't have to convert to partial pressure.
by Chris Pleman 3E
Sun Nov 19, 2017 11:19 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7337
Views: 788498

Re: Post All Chemistry Jokes Here

Did you know that you can cool yourself to -273.15˚C and still be 0k?
by Chris Pleman 3E
Sun Nov 19, 2017 11:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Octahedral vs Trigonal Bypyramidal family
Replies: 3
Views: 179

Re: Octahedral vs Trigonal Bypyramidal family

For the Octahedral shape, there will be four atoms on one plane, and two axial atoms bonded to the central atom.
by Chris Pleman 3E
Sun Nov 12, 2017 11:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Where to put the lone pairs?
Replies: 3
Views: 173

Re: Where to put the lone pairs?

A tetrahedral shape shouldn't have any lone pairs, only trigonal pyramidal will have a singular lone pair above the central atom.
by Chris Pleman 3E
Sun Nov 12, 2017 11:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Formula
Replies: 2
Views: 147

Re: VSEPR Formula

A corresponds to the central atom, the X with its subscript symbol represents the number of bonded atoms, and the E and its subscript applies to the number of lone pairs.
by Chris Pleman 3E
Sun Nov 05, 2017 10:46 pm
Forum: Lewis Structures
Topic: 3.25 part d
Replies: 2
Views: 124

Re: 3.25 part d

Hydrogen is allowed to act like a cation with no electrons- this hydrogen ion is common, and is what makes (for example) HCl an acids, as it disassociates into H+ and OH-.
by Chris Pleman 3E
Sun Nov 05, 2017 10:41 pm
Forum: SI Units, Unit Conversions
Topic: Si Unit for molar mass
Replies: 3
Views: 404

Re: Si Unit for molar mass

Yes, because the units for molar mass is g*mol^-1.
by Chris Pleman 3E
Sun Oct 29, 2017 10:11 pm
Forum: Quantum Numbers and The H-Atom
Topic: Direction of the Spin Magnetic Quantum Number
Replies: 5
Views: 300

Re: Direction of the Spin Magnetic Quantum Number

Postive 1/2 has an upward spin/arrow, and negative 1/2 has a downward spin/arrow.
by Chris Pleman 3E
Sun Oct 29, 2017 10:07 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity [ENDORSED]
Replies: 3
Views: 215

Re: Electron Affinity [ENDORSED]

Usually specific values will be provided through experimental data, but for the Chlorine vs. Bromine example, Chlorine would have the greater eletron affinity, as it is above Bromine in the periodic table.
by Chris Pleman 3E
Sun Oct 22, 2017 10:53 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: P orbitals
Replies: 4
Views: 372

Re: P orbitals

The first three electrons in the P orbital will all have a positive spin, and will occupy the Px, then Py, then Pz, orbital. Then the next three will all have negative spins, and will fill in that order. When filling orbitals (usually) we go from left to right with a positive spin first, and then on...
by Chris Pleman 3E
Sun Oct 22, 2017 10:46 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Numbers - Magnetic Quantum Number
Replies: 2
Views: 156

Re: Quantum Numbers - Magnetic Quantum Number

For this quantum number, the reason that it can have negative numbers for the orbitals is because it mirrors whatever positive number you get based off what l equals: therefore if you get m= 1, then it can be 1, 0, and -1, and if m=2 then it can be 2, 1, 0, -1, -2.
by Chris Pleman 3E
Sun Oct 15, 2017 4:39 pm
Forum: Photoelectric Effect
Topic: General Q about photoelectric effect terms [ENDORSED]
Replies: 2
Views: 136

Re: General Q about photoelectric effect terms [ENDORSED]

Threshold energy, unless specified otherwise.
by Chris Pleman 3E
Sun Oct 15, 2017 4:26 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Variation of Empirical Equation of H-atom [ENDORSED]
Replies: 2
Views: 138

Re: Variation of Empirical Equation of H-atom [ENDORSED]

The first is equation is referring to the change in energy (either released or absorbed) during the transition state of an electron from energy level to the next. So, (delta)E actually equals [(-hR)/(n(final))^2 - (-hR)/(n(initial))^2], because "delta" refers to "the change in" w...
by Chris Pleman 3E
Thu Oct 05, 2017 9:44 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E7 [ENDORSED]
Replies: 9
Views: 462

Re: E7 [ENDORSED]

Prof. Lavelle said that he isn't stressing sig figs as much as the content/information. Although, it's a better idea to round off at the end, because truncating your numbers too early can drastically change your answer.
by Chris Pleman 3E
Thu Oct 05, 2017 9:38 pm
Forum: Limiting Reactant Calculations
Topic: Percent Yield [ENDORSED]
Replies: 5
Views: 391

Re: Percent Yield [ENDORSED]

Also, another reason a high yield is important is if you're preparing a solution or a chemical that is an intermediate step to a larger experiment, the lower the yield the worse off the entire experiment becomes. If you think about it mathematically, it's similar to the function p= (C)^x where C is ...

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