Search found 54 matches

by Natalie LeRaybaud 1G
Thu Mar 15, 2018 2:16 pm
Forum: *Enzyme Kinetics
Topic: Catalysts in a reaction
Replies: 7
Views: 338

Catalysts in a reaction

Do catalysts always appear on the left side of the reaction initially and then move to the right in the second step of the reaction?
by Natalie LeRaybaud 1G
Thu Mar 15, 2018 2:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test 2 #6
Replies: 3
Views: 102

Test 2 #6

How can you tell what is being oxidized and reduced in this equation? And what is the cell diagram supposed to look like?
The problem is:

The following redox couple forms a galvanic cell which generates a current under standard conditions. O3/O2, OH- and O3,H+/O2
by Natalie LeRaybaud 1G
Thu Mar 15, 2018 2:07 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test #2 #7
Replies: 5
Views: 182

Test #2 #7

Did anyone get this problem correct and know how to solve it?

Calculate the standard potential for the following reaction using the standard reduction potentials on the last page of the test:
(Cr2O7)^2- (aq) + 14H+ (aq) + 12e- --> 2Cr (s) + 7H20 (l)
by Natalie LeRaybaud 1G
Wed Mar 07, 2018 12:11 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7337
Views: 787702

Re: Post All Chemistry Jokes Here

Q: What do dipoles say in passing?

A: Have you got a moment?
by Natalie LeRaybaud 1G
Wed Mar 07, 2018 12:05 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7337
Views: 787702

Re: Post All Chemistry Jokes Here

I asked the guy sitting next to me if he had any Sodium Hypobromite...
He said Na BrO
by Natalie LeRaybaud 1G
Wed Mar 07, 2018 11:56 am
Forum: Student Social/Study Group
Topic: Test 3
Replies: 3
Views: 274

Re: Test 3

My TA said that it covers problems 1-39 in chapter 15
by Natalie LeRaybaud 1G
Wed Mar 07, 2018 11:55 am
Forum: First Order Reactions
Topic: Integrated Rate Laws
Replies: 1
Views: 60

Re: Integrated Rate Laws

I’m pretty sure you can be safe just memorizing them as Dr. Lavelle said we wouldn’t make sure derive anything one tests. However it is probably helpful just to know or go over how to integrate the rage laws.
by Natalie LeRaybaud 1G
Wed Feb 28, 2018 2:14 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Test 3
Replies: 2
Views: 87

Re: Test 3

Yes it covers sections 15.1-15.6 which includes all the homework problems up till #39.
by Natalie LeRaybaud 1G
Wed Feb 28, 2018 2:12 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: units of K
Replies: 5
Views: 157

units of K

Are the units of K constantly changing or are they always the same? And if they are changing, what are they according to each specific order?
by Natalie LeRaybaud 1G
Wed Feb 28, 2018 2:10 pm
Forum: First Order Reactions
Topic: Deriving these Equations
Replies: 7
Views: 189

Re: Deriving these Equations

Yes I agree that it would have to be explicitly shown as [A]0 because otherwise it could be [A]t which refers to the final concentration at a certain time. So it is necessary to be able to differentiate between the 2.
by Natalie LeRaybaud 1G
Thu Feb 22, 2018 10:58 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic vs. Electrolytic Cell
Replies: 3
Views: 99

Galvanic vs. Electrolytic Cell

What is the main difference between a galvanic and electrolytic cell?
by Natalie LeRaybaud 1G
Thu Feb 22, 2018 10:55 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Pt(s) in a cell diagram
Replies: 1
Views: 76

Pt(s) in a cell diagram

I noticed that most of the solutions with cell diagrams from the homework include Pt(s) on one or both of the ends of the cell diagrams. Can someone please explain in which cases we add Platinum to the cell diagram and how we know whether it is on the anode side, cathode side, or both.
by Natalie LeRaybaud 1G
Thu Feb 22, 2018 10:51 am
Forum: Balancing Redox Reactions
Topic: Writing and Balancing Half Reactions
Replies: 6
Views: 160

Writing and Balancing Half Reactions

Does anyone have a simple step by step method to forming and balancing half reactions because I always seem to get lost along the way.
by Natalie LeRaybaud 1G
Tue Feb 13, 2018 12:41 pm
Forum: Calculating Work of Expansion
Topic: Calculating work in Reversible and Irreversible Pathways
Replies: 1
Views: 79

Calculating work in Reversible and Irreversible Pathways

How does the calculation equation for work change when finding it depending on whether the reaction is reversible or not? Like when do you use -PdeltaV, and
-nRTlnv2/v1 ?
by Natalie LeRaybaud 1G
Tue Feb 13, 2018 12:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 3/2R vs. 5/2R
Replies: 1
Views: 185

3/2R vs. 5/2R

Can someone please explain in what situations we multiply R by 3/2 and when we multiply it by 5/2. I mainly saw these calculations in internal energy problems but I am still quite confused on when they are specifically used.
by Natalie LeRaybaud 1G
Tue Feb 13, 2018 12:33 pm
Forum: Phase Changes & Related Calculations
Topic: Cv(vap) vs. normal specific heat capacity of H20
Replies: 1
Views: 86

Cv(vap) vs. normal specific heat capacity of H20

In what situations do you use Cv(vap) or Cp(vap) verses the normal specific heat capacities of water like the 4.184, 2.03, etc. values? This is referring to the context of calculating q in a heat curve problem, using q=mCdeltaT
by Natalie LeRaybaud 1G
Tue Feb 06, 2018 12:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode vs. Cathode
Replies: 2
Views: 112

Re: Anode vs. Cathode

Yes there is a difference between a Galvanic cell and an Electrolytic cell. In a Galvanic cell the reaction proceeds without an external potential helping it along. Since you have the oxidation reaction at the anode, this produces electrons and thus a build-up of negative charge in the course of the...
by Natalie LeRaybaud 1G
Tue Feb 06, 2018 12:45 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.45
Replies: 1
Views: 94

9.45

Can someone please explain how to go about doing this problem? Use the information in Table 8.3 to calculate the changes in entropy of the surroundings and of the system for (a) the vaporization of 1.00 mol CH4(l) at its normal boiling point; (b) the melting of 1.00 mol C2H5OH(s) at its normal melti...
by Natalie LeRaybaud 1G
Tue Feb 06, 2018 12:42 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: Irreversible Vs. Reversible Expansion
Replies: 2
Views: 97

Irreversible Vs. Reversible Expansion

Can someone please explain the difference between irreversible and reversible expansion and the effect it has when calculating entropy? I saw the diagrams of each posted on the website but now I feel a bit more confused on the subject.
by Natalie LeRaybaud 1G
Wed Jan 31, 2018 8:53 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.23 (molar enthalpy between molecules) [ENDORSED]
Replies: 2
Views: 93

Re: 9.23 (molar enthalpy between molecules) [ENDORSED]

In addition, molecules that are considered more complex tend to have greater entropies. Since CoF2 can be arrange in more different orientations when compared to BF3, it is considered more complex and this has a greater entropy.
by Natalie LeRaybaud 1G
Wed Jan 31, 2018 8:49 pm
Forum: Calculating Work of Expansion
Topic: Work Equations [ENDORSED]
Replies: 9
Views: 268

Re: Work Equations [ENDORSED]

Generally it is based off the information given within the problem. For instance if the temperature and amount of moles or mass of substance is given with aa changing volume, it is probably best to use the 2nd equation. If you are given a constant value of pressure then it would be safe to use the f...
by Natalie LeRaybaud 1G
Wed Jan 31, 2018 8:46 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: State functions [ENDORSED]
Replies: 7
Views: 171

Re: State functions [ENDORSED]

Yes, heat and work (q and w) are not considered state functions because they are dependent on the path taken whereas E, P, V, T, densities, and heat capacity as well as the ones we just learned deltaU, deltaH, deltaG, deltaS are all state functions.
by Natalie LeRaybaud 1G
Mon Jan 22, 2018 4:24 pm
Forum: Phase Changes & Related Calculations
Topic: 8.87 Temperatures
Replies: 5
Views: 157

Re: 8.87 Temperatures

Yes you would always use these temperature intervals because according to the heat curve 0 degrees is waters melting point and 100 degrees is the boiling point for water. These temperatures are significant because it is right at the point before a phase change occurs. Ex: 0 degrees: solid-> liquid a...
by Natalie LeRaybaud 1G
Mon Jan 22, 2018 4:20 pm
Forum: Phase Changes & Related Calculations
Topic: 8.21 Heat Lost vs. Heat Gained
Replies: 3
Views: 114

Re: 8.21 Heat Lost vs. Heat Gained

Not always. Sometimes there are other factors present in a system to take into account that can have an impact on the overall energy. However, when there is a direct heat transfer such as in this case the Copper transferring heat to the water, then the sum of the qs in the system equals zero.
by Natalie LeRaybaud 1G
Mon Jan 22, 2018 4:14 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 3 Test Topic is endorsed
Replies: 37
Views: 1643

Re: Week 3 Test Topic is endorsed

After going through the homework I noticed numbers 3-13,25-31, and 47-49 all have to do with calculating work or internal energy. I would suggest studying all the other homework problems specifically for this upcoming test.
by Natalie LeRaybaud 1G
Tue Jan 16, 2018 8:27 pm
Forum: Administrative Questions and Class Announcements
Topic: Acids and Bases
Replies: 3
Views: 147

Re: Acids and Bases

Although it isn't explicitly listed on the syllabus, I would still suggest making sure you know it because it will come in handy when doing problems in the future and its always good to have background knowledge with these things.
by Natalie LeRaybaud 1G
Tue Jan 16, 2018 5:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculating enthalpy using bond energies [ENDORSED]
Replies: 2
Views: 197

Calculating enthalpy using bond energies [ENDORSED]

When calculating the enthalpy using bond energies do we multiply the bond energy by the amount of moles the molecule has within the reaction or by the amount of bonds in the molecule? For example in number 75 the solution manual did not multiply the C-H bond energy by 4 even though the initial equat...
by Natalie LeRaybaud 1G
Tue Jan 16, 2018 5:45 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.77
Replies: 2
Views: 105

8.77

Can someone please explain how to go about doing this problem? Benzene is more stable and less reactive than would be predicted from its Kekulé structures. Use the mean bond enthalpies in Table 8.7 to calculate the lowering in molar energy when resonance is allowed between the Kekulé structures of b...
by Natalie LeRaybaud 1G
Sat Jan 13, 2018 11:00 pm
Forum: Phase Changes & Related Calculations
Topic: Extensive/Intensive
Replies: 5
Views: 189

Re: Extensive/Intensive

Extensive: depends on the amount of matter present Intensive: does not depend on the amount of matter in a substance It is important to know the properties because since all things are made up of matter it is necessary to understand these characteristics for calculations and whether or not a chemica...
by Natalie LeRaybaud 1G
Sat Jan 13, 2018 10:53 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Bomb Calorimetry
Replies: 4
Views: 172

Re: Bomb Calorimetry

A coffee cup calorimeter is good for measuring heat flow in a solution however it can’t be used for gaseous reactions because the gas would escape from the styrofoam cup. Although they both have the same function, the bomb calorimeter is generally used to measure heat flows for higher temperature re...
by Natalie LeRaybaud 1G
Sat Jan 13, 2018 10:48 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 13
Views: 451

Re: Phase Changes

The exothermic phase changes are the ones that occur going down a heat curve. This is because they are releasing energy during the reaction and therefore have energy as a product and have a negative delta H (enthalpy). This includes freezing, condensation, and deposition as stated above.
by Natalie LeRaybaud 1G
Sat Dec 09, 2017 8:49 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Compression effect on a system
Replies: 2
Views: 210

Compression effect on a system

How does compressing a system affect the overall reaction? This includes in matters such as volume, concentration , equilibrium, etc.
by Natalie LeRaybaud 1G
Thu Dec 07, 2017 10:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Cubic equations [ENDORSED]
Replies: 2
Views: 116

Cubic equations [ENDORSED]

How do you know when and how to simplify cubic equations when solving an ICE box problem?
by Natalie LeRaybaud 1G
Thu Dec 07, 2017 10:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.79 (with a quartic function) [ENDORSED]
Replies: 1
Views: 107

11.79 (with a quartic function) [ENDORSED]

I just noticed the following problem involves a quartic function. Are we supposed to expect quartic functions with ice boxes on the final? If so can someone please explain how to solve this problem? I have tried various times and the solution manual does not show the steps in solving for x. A reacto...
by Natalie LeRaybaud 1G
Wed Dec 06, 2017 3:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How to assume X is too small
Replies: 3
Views: 158

How to assume X is too small

Is there any way to assume X to be too small without calculating the actual value of X and using the 5% rule?
by Natalie LeRaybaud 1G
Wed Dec 06, 2017 3:39 pm
Forum: Limiting Reactant Calculations
Topic: Limiting reagent [ENDORSED]
Replies: 3
Views: 206

Re: Limiting reagent [ENDORSED]

Yes I agree. The best way is to use stoichiometry to find how many moles of a certain product the reaction will yield based off of the initial amount of reactant you are given in the problem. The reactant that yields less moles of product is the limiting reagent.
by Natalie LeRaybaud 1G
Tue Nov 28, 2017 6:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.91
Replies: 2
Views: 145

4.91

Can some one please explain part B to this problem? Benzyne, C6H4, is a highly reactive molecule that is detected only at low temperatures. It is related to benzene in that it has a six-membered ring of carbon atoms; but, instead of three double bonds, the structure is normally drawn with two double...
by Natalie LeRaybaud 1G
Tue Nov 28, 2017 6:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.59
Replies: 1
Views: 149

11.59

Can someone please explain how to solve this question, using the quadratic formula? A reaction mixture is prepared by mixing 0.100 mol SO2, 0.200 mol NO2, 0.100 mol NO, and 0.150 mol SO3 in a 5.00-L reaction vessel. The reaction SO2(g) NO2(g) ∆ NO(g) SO3(g) is allowed to reach equilibrium at 460 C, ...
by Natalie LeRaybaud 1G
Mon Nov 20, 2017 3:43 pm
Forum: Hybridization
Topic: How to tell the hybridization [ENDORSED]
Replies: 4
Views: 204

Re: How to tell the hybridization [ENDORSED]

A quick way to determine hybridization is to look at the electron domains. Generally if a molecule has less than 5 electron domains, the hybridization has the number 1 less than the amount of domains. For example 4 e- domains: SP3, 3 e- domains: SP2, 2 e- domains: SP. Thats just a quick way to check...
by Natalie LeRaybaud 1G
Mon Nov 20, 2017 2:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar ve non polar [ENDORSED]
Replies: 7
Views: 315

Re: Polar ve non polar [ENDORSED]

Another way to quickly determine whether a molecule is polar or non-polar is to look at the lewis structures. Generally, a non-polar molecule will look completely symmetrical, such as CCl4. The chlorines pull on the carbon in an equal manor with equal bond angles. Other lewis structures which are no...
by Natalie LeRaybaud 1G
Thu Nov 16, 2017 8:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs
Replies: 5
Views: 265

Re: Lone Pairs

In general you would put the lone pairs on the central atom, unless of course it follows the octet rule and can not have more than 8 valence electrons bonded. But overall pay attention to the octet rule and if the central atom follows it, then the lone pair is most likely to be placed on the central...
by Natalie LeRaybaud 1G
Thu Nov 16, 2017 8:36 pm
Forum: Hybridization
Topic: Lone pairs effect hybridization
Replies: 3
Views: 112

Lone pairs effect hybridization

Do lone pairs effect hybridization? And if so what would be the hybridization of an atom with more than 4 or 5 electron domains ?
by Natalie LeRaybaud 1G
Tue Nov 07, 2017 7:42 pm
Forum: Bond Lengths & Energies
Topic: Bond Lengths [ENDORSED]
Replies: 8
Views: 431

Re: Bond Lengths [ENDORSED]

No I don't think that you will have to know pi bonds for the midterm.
by Natalie LeRaybaud 1G
Tue Nov 07, 2017 7:40 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Reactions post-module assessment
Replies: 2
Views: 141

Re: Balancing Chemical Reactions post-module assessment

I'm pretty sure it is Reaction Coefficients.
by Natalie LeRaybaud 1G
Tue Nov 07, 2017 7:32 pm
Forum: Lewis Structures
Topic: Shape
Replies: 5
Views: 214

Re: Shape

No I remember in class that he said that as long as you got the electron distribution right and the relative shape, it would be fine. He also said that either _I_ or the Mercedes logo shape would be fine specifically for trigonal planar structures.
by Natalie LeRaybaud 1G
Tue Nov 07, 2017 7:26 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reactant
Replies: 3
Views: 204

Re: Limiting Reactant

Yes you can assume this only if you have solved for the amount after your conversions. Like after you convert from percent-->grams-->moles--> and then divide by the smallest mole. The lowest value at that point is safe to say is the limiting reactant, otherwise you can't assume (like if your just ta...
by Natalie LeRaybaud 1G
Tue Oct 31, 2017 4:29 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Determining if an atom is in an excited state
Replies: 2
Views: 185

Determining if an atom is in an excited state

How can you determine if an atom is in its ground state or excited state just by looking at the electron configuration?
by Natalie LeRaybaud 1G
Tue Oct 31, 2017 4:25 pm
Forum: Trends in The Periodic Table
Topic: Ionization energy exception; O
Replies: 2
Views: 388

Ionization energy exception; O

Can someone please explain why Oxygen is an exception to the ionization energy trend of the periodic table, like when it is compared to Nitrogen or Fluorine?
by Natalie LeRaybaud 1G
Mon Oct 23, 2017 9:19 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Sequen of Orbitals
Replies: 4
Views: 187

Sequen of Orbitals

Are we always supposed to put the 4s orbitals after the 3d? Because in high school I'm pretty sure we learned to write out 4s then 3d. For example the electron configuration for Gallium I thought would be Ga: [Ar] 4s2 3d10 4p1 but are we now supposed to write it as Ga: [Ar] 3d10 4s2 4p1 ? And if so ...
by Natalie LeRaybaud 1G
Mon Oct 23, 2017 9:03 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: p-orbitals
Replies: 3
Views: 153

p-orbitals

Do we always have to separate the p orbitals? For example like px, py, pz? And if so, why is it only done for p orbitals?
by Natalie LeRaybaud 1G
Fri Oct 13, 2017 11:43 am
Forum: Properties of Light
Topic: Speed of Light Constant
Replies: 18
Views: 587

Re: Speed of Light Constant

Honestly, it doesn't really matter. You will get the correct answer either way. But it would be safer to be more exact so I would suggest using 2.998*10^8. Just remember to round to the nearest Sig Fig.
by Natalie LeRaybaud 1G
Fri Oct 13, 2017 11:25 am
Forum: Properties of Light
Topic: Figure 1.9
Replies: 4
Views: 225

Re: Figure 1.9

Yes, I agree my TA specified to know the Electromagnetic Spectrum, not in the sense that you need to memorize every single value but like if you were to be given a specific wavelength, you should be able to estimate which area its in. Visible Light will be the most common.
by Natalie LeRaybaud 1G
Thu Oct 05, 2017 6:58 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical Coefficients [ENDORSED]
Replies: 12
Views: 636

Re: Empirical Coefficients [ENDORSED]

Yeah I agree. You mainly want to round when you get a number ending in like .5, .333, .666. etc. Other then that, if the number is below .5 in the tens place then round down and if above, round up.
by Natalie LeRaybaud 1G
Thu Oct 05, 2017 3:21 pm
Forum: Significant Figures
Topic: Sig Figs
Replies: 8
Views: 645

Re: Sig Figs

So a little trick to remember sig figs is the PACIFIC/ATLANTIC rule. If the decimal is PRESENT you start from the left side (Pacific) and go to the first non-zero number and count that one as well all the numbers after Ex: 0.004670 would be 4 sig figs because the 1st non-zero number is 4 so you coun...

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