## Search found 61 matches

Mon Mar 11, 2019 4:17 pm
Forum: Second Order Reactions
Topic: Final
Replies: 30
Views: 847

### Re: Final

It's cumulative, but I would focus more on the newest topics and topics that were not heavily covered on the midterm and two tests.
Mon Mar 11, 2019 4:16 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Rate Order Graphs
Replies: 3
Views: 192

### Re: Rate Order Graphs

i find this diagram pretty helpful in determining order: (shows zero, first, and second order graphs respectively)
Mon Mar 11, 2019 4:07 pm
Forum: Zero Order Reactions
Topic: Graphs
Replies: 6
Views: 421

### Re: Graphs

here are the graphs for zero order, first order, and second order, respectively
Tue Mar 05, 2019 10:04 am
Forum: General Rate Laws
Topic: Order of Reaction
Replies: 6
Views: 265

### Re: Order of Reaction

We should be prepared to find, for the purposes of this class, the zeroth order, first order, and second order. There are orders higher than that, but they are rare and we are not expected to do calculations involving those.
Tue Mar 05, 2019 10:03 am
Forum: General Rate Laws
Topic: units of rates and rate constants
Replies: 4
Views: 206

### Re: units of rates and rate constants

The above responses are correct. You can think of dividing the units by moles as you move up to the next order.
Tue Mar 05, 2019 9:58 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Replies: 73
Views: 3965

### Re: Study Advice

I like Lyndon's and Karen's because they have worksheets you can practice.
Tue Feb 19, 2019 4:48 pm
Forum: Van't Hoff Equation
Topic: Equation
Replies: 4
Views: 360

### Re: Equation

We are not technically using the Van't Hoff Equation, we are using a derivation that is useful for the purposes of this class.
Tue Feb 19, 2019 4:46 pm
Forum: Van't Hoff Equation
Topic: Constants and formulas
Replies: 7
Views: 508

### Re: Constants and formulas

We never have to be able to completely derive an equation, only manipulate one and solve it.
Tue Feb 19, 2019 4:43 pm
Forum: Van't Hoff Equation
Topic: Practice Test
Replies: 5
Views: 686

### Re: Practice Test

We don't need to know how to derive it, only to manipulate/solve it.
Sun Feb 17, 2019 11:00 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: calculating delta G
Replies: 4
Views: 146

### Re: calculating delta G

If given degrees Celsius, convert to K.
Sun Feb 17, 2019 10:59 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy
Replies: 7
Views: 307

### Re: Gibbs Free Energy

Eva Guillory 2E wrote:

What do exergonic and endergonic mean?
Sun Feb 17, 2019 10:57 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity
Replies: 4
Views: 166

### Re: Spontaneity

You know a reaction is spontaneous when delta G is negative. If it's positive, the reaction is not spontaneous.
Tue Feb 12, 2019 9:44 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Difference between delta U and delta H?
Replies: 3
Views: 195

### Re: Difference between delta U and delta H?

Delta H is equal to q at constant pressure, whereas delta U=q+w.
Tue Feb 12, 2019 9:41 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: assuming no work
Replies: 2
Views: 66

### Re: assuming no work

Work is interpreted as energy used in the process of compression or expansion of a system. This means the value of work changes when the volume changes. For this reason, w=0 when there is no compression or expansion.
Tue Feb 12, 2019 9:37 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Replies: 4
Views: 186

### Re: answer format

If they ask for the change in internal energy, give your answer in J or kJ.
Mon Feb 04, 2019 1:41 pm
Forum: Phase Changes & Related Calculations
Topic: Heat Curve
Replies: 6
Views: 219

### Re: Heat Curve

We will be given the curve if we need the values to solve a problem. Lavelle never makes us memorize constants.
Mon Feb 04, 2019 1:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 4
Views: 152

### Re: Bond Enthalpies

Other than pure visualization, there is no shortcut.
Mon Feb 04, 2019 1:37 pm
Forum: Phase Changes & Related Calculations
Topic: Heat and Condensation
Replies: 9
Views: 371

### Re: Heat and Condensation

Condensation is exothermic.
Tue Jan 29, 2019 9:40 am
Forum: Phase Changes & Related Calculations
Topic: Phase changes
Replies: 14
Views: 638

### Re: Phase changes

I know phase changes from liquid to vapor, solid to liquid, and solid to vapor are always endothermic. Would the opposite phases changes (vapor to liquid, and liquid to solid) always be exothermic? Yes, you are correct. In the first changes you listed, heat acts like a reactant. This means the reac...
Tue Jan 29, 2019 9:37 am
Forum: Phase Changes & Related Calculations
Topic: Steam
Replies: 11
Views: 426

### Re: Steam

To answer this question, you must refer to the heating curve. In this case, steam has more energy in Kj/mol, meaning it will burn your hand more upon contact due to the higher amount of energy of vaporized water (compared to the lower amount of energy in liquid water).
Tue Jan 29, 2019 9:33 am
Forum: Phase Changes & Related Calculations
Topic: Standard entalpy of formation
Replies: 6
Views: 232

### Re: Standard entalpy of formation

When a molecule is in its most stable state, the standard enthalpy of formation equals 0.
Wed Jan 23, 2019 12:35 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endothermic vs. Exothermic
Replies: 8
Views: 365

### Re: Endothermic vs. Exothermic

When a reaction is endothermic, think of heat as a reactant.
When a reaction is exothermic, think of heat as a product.
Wed Jan 23, 2019 12:31 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Chem Eq. Module #4 Question 15 Conflicting Answers
Replies: 2
Views: 150

### Re: Chem Eq. Module #4 Question 15 Conflicting Answers

This is similar to when we discuss endothermic or exothermic reactions. If heat is added or removed, the equilibrium shifts. However, heat is not included in K. Same goes for water in this example.
Wed Jan 23, 2019 12:28 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Chemical Equilibrium part 4 post module assessment question #12
Replies: 2
Views: 93

### Re: Chemical Equilibrium part 4 post module assessment question #12

This is because the stoichiometric coefficients/ratio are the same on each side, meaning it won't favor either side.
Mon Jan 21, 2019 6:22 pm
Forum: Administrative Questions and Class Announcements
Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
Replies: 179
Views: 12897

### Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)

Meigan Wu 2E wrote:On Worksheet 2, why is the concentration of CO3 the same as Ka2 for problem 4b?

^ I have the same question
Wed Jan 16, 2019 12:49 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: stability
Replies: 3
Views: 159

### Re: stability

Stability is based on whether the reaction favors the products. A more stable reaction would favor the products, making the K value larger.
Wed Jan 16, 2019 12:46 pm
Forum: Ideal Gases
Topic: pressure [ENDORSED]
Replies: 13
Views: 357

### Re: pressure[ENDORSED]

For the effect of something like pressure, use the ideal gas law PV=nRT. Increasing something on one side will increase something on the other side.
Wed Jan 16, 2019 12:43 pm
Forum: Ideal Gases
Topic: Homework for week 2 [ENDORSED]
Replies: 10
Views: 2393

### Re: Homework for week 2[ENDORSED]

Anything that's not too far off base from what we've learned so far is good. This all relates to chemical equilibria.
Thu Jan 10, 2019 10:12 am
Forum: Ideal Gases
Topic: Ideal vs Real Gas
Replies: 6
Views: 237

### Re: Ideal vs Real Gas

haleyervin7 wrote:For purposes of calculation, do we always assume it is an ideal gas?

For the purposes of this class, we need to assume that a gas is an ideal gas in order to use the idea gas equation. If the problem requires calculations, it's safe to assume it's an ideal gas.
Thu Jan 10, 2019 10:05 am
Forum: Ideal Gases
Topic: Post Assessment
Replies: 3
Views: 153

### Re: Post Assessment

A similar way to think about it is that if K>10^3, the reaction favors the products. If K<10^3, the reaction favors the reactants.
Thu Jan 10, 2019 10:03 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Giving Qc or Qp when asked for Q
Replies: 5
Views: 197

### Re: Giving Qc or Qp when asked for Q

When they give you values in bars, use Qp. When they give you values in M (mol/L), use Qc.
Mon Dec 03, 2018 1:48 pm
Forum: Bronsted Acids & Bases
Topic: Comparing pH levels
Replies: 3
Views: 125

### Re: Comparing pH levels

Not sure if we have to answer that directly, yet it's good to know for problem solving and checking your answer.
Mon Dec 03, 2018 1:47 pm
Forum: Naming
Topic: Metal Suffix
Replies: 2
Views: 141

### Re: Metal Suffix

Yes, you only add -ate if the whole compound is negative.
Mon Dec 03, 2018 1:46 pm
Forum: Naming
Topic: Order of Ligand Naming
Replies: 6
Views: 231

### Re: Order of Ligand Naming

Saman Andalib 1A wrote:You name the ligands in a coordination compound in alphabetical order.

To follow up, is it alphabetical order by prefix or by the names of the ligands?
Mon Nov 26, 2018 9:21 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: test #3
Replies: 14
Views: 755

### Re: test #3

Maggie Pickford 3F wrote:So what exactly is paramagnetism and diamagnetism?

Paramagnetic means that there is only one electron in the subshell, whereas diamagnetic means that two electrons are paired (with opposite spin) in the same subshell.
Mon Nov 26, 2018 9:20 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: test #3
Replies: 14
Views: 755

### Re: test #3

ariellasarkissian_3H wrote:Also, are we responsible for memorizing the bond angles for each shape?

Yes, he mentioned that you must memorize the VSEPR shapes and their bond angles.
Mon Nov 26, 2018 9:18 pm
Forum: Hybridization
Topic: electron occupying unhybridized orbital
Replies: 2
Views: 90

### Re: electron occupying unhybridized orbital

This is because a hybridization gives the molecule a lower energy state than if it were unhybridized. This makes it more stable.
Tue Nov 20, 2018 10:27 am
Forum: Hybridization
Topic: Hybridized Orbitals
Replies: 4
Views: 150

### Re: Hybridized Orbitals

The d orbital exists when there is an expanded octet.
Tue Nov 20, 2018 10:25 am
Forum: Hybridization
Topic: Identifying types of bonds and hybridization in Lewis Structures
Replies: 3
Views: 155

### Re: Identifying types of bonds and hybridization in Lewis Structures

We are only expected to draw the Lewis structures as we had done so before. He just wants us to be able to identify the geometry (VSEPR model) by looking at the Lewis structure. We are not expected to draw the VSEPR model ourselves.
Tue Nov 20, 2018 10:21 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bold/Dashed Lines in Bonds
Replies: 4
Views: 171

### Re: Bold/Dashed Lines in Bonds

It doesn't matter which atoms for which the bonds you make bold or dashed if the bonds are symmetrical with that shape because the structure can rotate. It's just a different view.
Wed Nov 14, 2018 5:40 pm
Forum: Dipole Moments
Topic: dipole distance
Replies: 3
Views: 137

### Re: dipole distance

Here's a way I like to think about it:
single bond- longest, weakest
double bond
triple bond- shortest, strongest
Wed Nov 14, 2018 5:34 pm
Forum: Electronegativity
Topic: Electronegativity Values
Replies: 2
Views: 143

### Re: Electronegativity Values

For reference, there is a figure in the electronegativity section showing the electronegativity values on the periodic table. However, for the test, just know that the further apart elements are on the periodic table, the greater difference in electronegativity they will have.
Wed Nov 14, 2018 5:31 pm
Forum: Electronegativity
Topic: ChemistryHow are electronegativity values for elements determined?
Replies: 3
Views: 173

### Re: ChemistryHow are electronegativity values for elements determined?

The electronegativity values are experimentally calculated. There is a chart in the book that lists electronegativity values, so you can just use that. As a general rule, elements further apart on the periodic table will have a higher difference in electronegativity.
Thu Nov 08, 2018 9:45 am
Forum: Octet Exceptions
Topic: electron affinity
Replies: 6
Views: 274

### Re: electron affinity

Fluorine is kind of an exception to the general rule of electron affinity. Typically, you would expect F to have a higher electron affinity since it is higher in the group than Cl. F is very small though, so there is electron-electron repulsion when you add a new electron because there are already e...
Thu Nov 08, 2018 9:36 am
Forum: Formal Charge and Oxidation Numbers
Topic: How do both intersect?
Replies: 3
Views: 233

### Re: How do both intersect?

Finding the oxidation number of each element in a molecule gives you the formal charge of each element and subsequently that of the whole molecule.
Thu Nov 08, 2018 9:30 am
Forum: Resonance Structures
Replies: 11
Views: 790

Radicals have one unpaired, lone valence electron. They are very unstable and don't exist long by themselves in nature.
Here's an example of what it looks like and how you would draw it:
Tue Oct 30, 2018 11:22 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Lowest Energy/Stable
Replies: 2
Views: 230

### Re: Lowest Energy/Stable

Most stable/lowest energy are essentially the same in this context. As for the structures, if you compare two separate structures that have different formal charges assigned, the one with the formal charge closest to zero would be considered most stable/lowest energy.
Tue Oct 30, 2018 11:18 pm
Forum: Ionic & Covalent Bonds
Topic: Interactions between ions
Replies: 3
Views: 207

### Re: Interactions between ions

We only need to know what he lists on his lecture outlines on his website for 14A. I would check the Chemical Bonds outline!
Tue Oct 30, 2018 11:14 pm
Forum: Lewis Structures
Topic: Exception to Octet Rule [ENDORSED]
Replies: 3
Views: 136

### Re: Exception to Octet Rule[ENDORSED]

The exceptions start in the second row of the p-block, and continue in the rows of the p-block below that.
Sat Oct 27, 2018 11:07 pm
Forum: Ionic & Covalent Bonds
Topic: Help on 3.39
Replies: 2
Views: 217

### Re: Help on 3.39

remember that ionic bonds do not share electrons!
Sat Oct 27, 2018 11:01 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Shielding effect
Replies: 6
Views: 392

### Re: Shielding effect

For me, it helps to use the bonfire metaphor that Dr. Lavelle mentioned in lecture. Let's say you're an electron sitting close to the fire. If another person (another electron) sits or stands in between you and the fire, then you will feel less heat (or attraction) to the fire (nucleus). In a sense,...
Sat Oct 27, 2018 9:43 pm
Forum: Trends in The Periodic Table
Topic: Homework 2.67b
Replies: 2
Views: 106

### Re: Homework 2.67b

Additionally, in general the elements in the top right of the periodic table have a higher electron affinity. So by this general guideline, carbon would have a higher electron affinity.
Sun Oct 21, 2018 2:30 pm
Forum: Properties of Electrons
Topic: Quantum World 1.33
Replies: 4
Views: 180

### Re: Quantum World 1.33

Does anyone know with certainty that we will be given the mass of an electron on the test?
Sun Oct 21, 2018 2:28 pm
Forum: Properties of Electrons
Topic: Wavelength Calculations
Replies: 5
Views: 280

### Re: Wavelength Calculations

To add to the previous response, we will only be given the equations for E=hv and c=λv, which we must combine to produce E=hc/λ on the test.
Sun Oct 21, 2018 2:23 pm
Forum: Properties of Electrons
Topic: Atomic Spectra: absorption vs emission
Replies: 3
Views: 104

### Re: Atomic Spectra: absorption vs emission

As far as I know, the electrons must still jump up or down an energy level, but there is the same energy difference between each. So absorption would be +eV, and emission would be the same amount but -eV.
Sat Oct 13, 2018 5:50 pm
Forum: Photoelectric Effect
Topic: Module Question 30 (Part C)
Replies: 1
Views: 74

### Module Question 30 (Part C)

Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Will someone walk me through this? 30. C. What is the frequency of the incident light on the sodium metal surface? A. 3.01 x 1014 Hz B. 2.27 x 1038 Hz C. 4....
Sat Oct 13, 2018 5:49 pm
Forum: Photoelectric Effect
Topic: Module Question 29 (Part B)
Replies: 4
Views: 233

### Module Question 29 (Part B)

Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Will someone walk me through this? 29. B. How much energy is required to remove an electron from one sodium atom? A. 2.501 x 10-22 J B. 1.506 x 105 J C. 2.5...
Sat Oct 13, 2018 5:48 pm
Forum: Photoelectric Effect
Topic: Module Question 28 Part A
Replies: 1
Views: 70

### Module Question 28 Part A

Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Will someone walk me through this? A. What is the kinetic energy of the ejected electron? A. 3.01 x 1025 J B. 3.98 x 10-19 J C. 7.96 x 10-19 J D. 1.99 x 10-...
Thu Oct 04, 2018 5:32 pm
Forum: Molarity, Solutions, Dilutions
Topic: Periodic Table and Molar Mass?
Replies: 2
Views: 72

### Re: Periodic Table and Molar Mass?

During lecture, Dr. Lavelle mentioned that we would always be given the periodic table on tests (even when we do not need it) so that we can feel comfortable. I am assuming he was referring to not only the midterm and final but the discussion quizzes/tests as well.
Thu Oct 04, 2018 5:28 pm
Forum: Balancing Chemical Reactions
Topic: Net number of molecules
Replies: 3
Views: 126

### Re: Net number of molecules

1. Add up the coefficients of each side of the equation (this gives you the total amount of moles on each side).
2. Find the difference in moles on each side (subtract the total moles of products from the total moles of reactants).
Thu Oct 04, 2018 5:21 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Molecule vs Formula Unit
Replies: 4
Views: 341

### Re: Molecule vs Formula Unit

Essentially, when they are asking for the amount of molecules, they are referring to an element or something covalently bonded (think Na or O2). When they are asking for the amount of formula molecules, they are referring to an ionic compound (NaCl). You must use Avogadro's number for both situation...

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