Search found 54 matches
- Thu Mar 15, 2018 2:16 pm
- Forum: *Enzyme Kinetics
- Topic: Catalysts in a reaction
- Replies: 12
- Views: 1716
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?
- Thu Mar 15, 2018 2:10 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2 #6
- Replies: 3
- Views: 484
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
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
- Thu Mar 15, 2018 2:07 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test #2 #7
- Replies: 5
- Views: 1445
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)
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)
- Wed Mar 07, 2018 12:11 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3911999
Re: Post All Chemistry Jokes Here
Q: What do dipoles say in passing?
A: Have you got a moment?
A: Have you got a moment?
- Wed Mar 07, 2018 12:05 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3911999
Re: Post All Chemistry Jokes Here
I asked the guy sitting next to me if he had any Sodium Hypobromite...
He said Na BrO
He said Na BrO
- Wed Mar 07, 2018 11:56 am
- Forum: Student Social/Study Group
- Topic: Test 3
- Replies: 3
- Views: 646
Re: Test 3
My TA said that it covers problems 1-39 in chapter 15
- Wed Mar 07, 2018 11:55 am
- Forum: First Order Reactions
- Topic: Integrated Rate Laws
- Replies: 1
- Views: 287
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.
- Wed Feb 28, 2018 2:14 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Test 3
- Replies: 2
- Views: 378
Re: Test 3
Yes it covers sections 15.1-15.6 which includes all the homework problems up till #39.
- Wed Feb 28, 2018 2:12 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: units of K
- Replies: 5
- Views: 688
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?
- Wed Feb 28, 2018 2:10 pm
- Forum: First Order Reactions
- Topic: Deriving these Equations
- Replies: 7
- Views: 778
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.
- 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: 501
Galvanic vs. Electrolytic Cell
What is the main difference between a galvanic and electrolytic cell?
- 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: 297
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.
- Thu Feb 22, 2018 10:51 am
- Forum: Balancing Redox Reactions
- Topic: Writing and Balancing Half Reactions
- Replies: 6
- Views: 1069
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.
- Tue Feb 13, 2018 12:41 pm
- Forum: Calculating Work of Expansion
- Topic: Calculating work in Reversible and Irreversible Pathways
- Replies: 1
- Views: 308
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 ?
-nRTlnv2/v1 ?
- Tue Feb 13, 2018 12:37 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: 3/2R vs. 5/2R
- Replies: 1
- Views: 768
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.
- 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: 298
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
- Tue Feb 06, 2018 12:58 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode vs. Cathode
- Replies: 2
- Views: 1065
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...
- Tue Feb 06, 2018 12:45 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 9.45
- Replies: 2
- Views: 1018
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...
- 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: 390
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.
- 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: 347
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.
- Wed Jan 31, 2018 8:49 pm
- Forum: Calculating Work of Expansion
- Topic: Work Equations [ENDORSED]
- Replies: 9
- Views: 1452
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...
- Wed Jan 31, 2018 8:46 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: State functions [ENDORSED]
- Replies: 7
- Views: 787
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.
- Mon Jan 22, 2018 4:24 pm
- Forum: Phase Changes & Related Calculations
- Topic: 8.87 Temperatures
- Replies: 5
- Views: 526
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...
- Mon Jan 22, 2018 4:20 pm
- Forum: Phase Changes & Related Calculations
- Topic: 8.21 Heat Lost vs. Heat Gained
- Replies: 3
- Views: 451
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.
- Mon Jan 22, 2018 4:14 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Week 3 Test Topic is endorsed
- Replies: 37
- Views: 4942
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.
- Tue Jan 16, 2018 8:27 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Acids and Bases
- Replies: 3
- Views: 307
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.
- 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: 1009
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...
- 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: 420
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...
- Sat Jan 13, 2018 11:00 pm
- Forum: Phase Changes & Related Calculations
- Topic: Extensive/Intensive
- Replies: 5
- Views: 1689
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...
- Sat Jan 13, 2018 10:53 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Bomb Calorimetry
- Replies: 4
- Views: 1868
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...
- Sat Jan 13, 2018 10:48 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes
- Replies: 13
- Views: 1562
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.
- Sat Dec 09, 2017 8:49 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Compression effect on a system
- Replies: 2
- Views: 399
Compression effect on a system
How does compressing a system affect the overall reaction? This includes in matters such as volume, concentration , equilibrium, etc.
- Thu Dec 07, 2017 10:38 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Cubic equations [ENDORSED]
- Replies: 2
- Views: 283
Cubic equations [ENDORSED]
How do you know when and how to simplify cubic equations when solving an ICE box problem?
- Thu Dec 07, 2017 10:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.79 (with a quartic function) [ENDORSED]
- Replies: 1
- Views: 404
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...
- Wed Dec 06, 2017 3:41 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: How to assume X is too small
- Replies: 3
- Views: 722
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?
- Wed Dec 06, 2017 3:39 pm
- Forum: Limiting Reactant Calculations
- Topic: Limiting reagent [ENDORSED]
- Replies: 3
- Views: 496
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.
- Tue Nov 28, 2017 6:40 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 4.91
- Replies: 2
- Views: 423
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...
- Tue Nov 28, 2017 6:34 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.59
- Replies: 2
- Views: 909
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, ...
- Mon Nov 20, 2017 3:43 pm
- Forum: Hybridization
- Topic: How to tell the hybridization [ENDORSED]
- Replies: 4
- Views: 660
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...
- Mon Nov 20, 2017 2:43 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polar ve non polar [ENDORSED]
- Replies: 7
- Views: 1012
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...
- Thu Nov 16, 2017 8:41 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs
- Replies: 5
- Views: 680
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...
- Thu Nov 16, 2017 8:36 pm
- Forum: Hybridization
- Topic: Lone pairs effect hybridization
- Replies: 3
- Views: 409
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 ?
- Tue Nov 07, 2017 7:42 pm
- Forum: Bond Lengths & Energies
- Topic: Bond Lengths [ENDORSED]
- Replies: 8
- Views: 1160
Re: Bond Lengths [ENDORSED]
No I don't think that you will have to know pi bonds for the midterm.
- Tue Nov 07, 2017 7:40 pm
- Forum: Balancing Chemical Reactions
- Topic: Balancing Chemical Reactions post-module assessment
- Replies: 2
- Views: 407
Re: Balancing Chemical Reactions post-module assessment
I'm pretty sure it is Reaction Coefficients.
- Tue Nov 07, 2017 7:32 pm
- Forum: Lewis Structures
- Topic: Shape
- Replies: 5
- Views: 591
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.
- Tue Nov 07, 2017 7:26 pm
- Forum: Limiting Reactant Calculations
- Topic: Limiting Reactant
- Replies: 3
- Views: 667
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...
- 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: 2143
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?
- Tue Oct 31, 2017 4:25 pm
- Forum: Trends in The Periodic Table
- Topic: Ionization energy exception; O
- Replies: 2
- Views: 4593
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?
- Mon Oct 23, 2017 9:19 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Sequen of Orbitals
- Replies: 4
- Views: 545
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 ...
- Mon Oct 23, 2017 9:03 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: p-orbitals
- Replies: 3
- Views: 435
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?
- Fri Oct 13, 2017 11:43 am
- Forum: Properties of Light
- Topic: Speed of Light Constant
- Replies: 18
- Views: 1784
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.
- Fri Oct 13, 2017 11:25 am
- Forum: Properties of Light
- Topic: Figure 1.9
- Replies: 4
- Views: 525
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.
- Thu Oct 05, 2017 6:58 pm
- Forum: Empirical & Molecular Formulas
- Topic: Empirical Coefficients [ENDORSED]
- Replies: 12
- Views: 5845
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.
- Thu Oct 05, 2017 3:21 pm
- Forum: Significant Figures
- Topic: Sig Figs
- Replies: 8
- Views: 3498
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...