Search found 70 matches
- Fri Mar 16, 2018 7:13 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Work and derivations
- Replies: 2
- Views: 507
Work and derivations
So I know for a reaction that produces a net number of moles, w=-(delta n)RT, is this in anyway related to Delta H=\Delta U+\Delta nRT (which is found in the book)? If so, how come we can use this equation under constant volume. I thought that work is zero for constant volume. However, this is the p...
- Fri Mar 16, 2018 12:31 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Book Thinking Point
- Replies: 1
- Views: 456
Book Thinking Point
I saw this in the book and don't understand. "Potential energy is related to position. Therefore, in an isothermal expansion, why is there no potential energy change as the molecules move further apart?" Is this because temperature is related to the heat energy of the particles, and so the...
- Fri Mar 16, 2018 12:29 am
- Forum: Phase Changes & Related Calculations
- Topic: Constant Volume
- Replies: 3
- Views: 508
Constant Volume
Is this correct? So I know that when volume is constant, work is zero. However, for a reaction with changing pressure and moles, but constant volume, that is behaving ideally, we can relate deltaPV=delta nRT, in which there would be work, right?
- Mon Mar 12, 2018 11:24 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Distinguishing a Catalyst
- Replies: 4
- Views: 678
Re: Distinguishing a Catalyst
A reactant does not show up on the product sides. It is consumed in the reaction. A catalyst, on the other hand, will show up on both sides.
- Mon Mar 12, 2018 11:23 pm
- Forum: General Rate Laws
- Topic: graphs
- Replies: 8
- Views: 983
Re: graphs
I would assume so, as they will aid in finding the y intercepts, and the overall shape of the graph, based on the order.
- Mon Mar 12, 2018 11:22 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Reaction Mechanism Steps
- Replies: 4
- Views: 577
Re: Reaction Mechanism Steps
I think so because the rate law is just determined by that one step, so that is the only step that could be the rate determining step.
- Mon Mar 12, 2018 11:21 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Discussion Sections
- Replies: 2
- Views: 482
Re: Discussion Sections
Yes. Discussion sessions meet this week. However, next week, there are no classes.
- Fri Mar 09, 2018 12:03 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: What is Molecularity?
- Replies: 9
- Views: 2508
Re: What is Molecularity?
I don't think that molecularity isn't involved in intermediates. Molecularity only applies to the reactants in the rate determining step. If there are intermediates in the slow step, you have to solve for correct pre-equilibrium rate law, I believe.
- Fri Mar 09, 2018 12:01 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts
- Replies: 5
- Views: 863
Re: Catalysts
The activation energy determines the rate of reaction. To increase the rate of reaction, the activation energy or energy barrier must be lowered. For example, when rolling a ball up a hill and then letting it roll down, the get up the hill is the activation energy. A catalyst just builds a tunnel th...
- Fri Mar 09, 2018 12:00 pm
- Forum: Second Order Reactions
- Topic: Units of k for orders above 2nd
- Replies: 6
- Views: 893
Re: Units of k for orders above 2nd
Yes this trend should continue. Just remember that for zero order, it is actually mol/l*s, not inverted.
- Sat Mar 03, 2018 3:20 pm
- Forum: General Rate Laws
- Topic: 15.39a
- Replies: 3
- Views: 476
15.39a
For a, because the reaction is 2A-->B + C, why isn't there a 2 in the reaction. If we are solving the differential rate law -1/2 d[A]/dt=k[A]^2, we get -1/2 d[A]/[A]^2= kdt. If we multiply the 2 to the other side, we are left with -d[A]/[A]^2=2kdt. If we integrate both sides, we get 1/[A]=2kt + 1/[A...
- Wed Feb 28, 2018 10:39 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Determining order
- Replies: 1
- Views: 365
Re: Determining order
They determined the concentration of H3O+ from steps 2 and 4. In these steps, both BrO3- and Br- are staying the same initial concentration. However, only H3O+ is changing. Therefore, by using these two steps, find the exponent of H3O+. And fc and ln is just another way of finding the exponent. They...
- Wed Feb 28, 2018 10:37 pm
- Forum: First Order Reactions
- Topic: Derivation
- Replies: 8
- Views: 1064
Re: Derivation
No. My TA stated that this won't be necessary. However, Dr. Lavelle has spoken on how it helps to know how to derive each formula, as it demonstrates a deeper understanding of the concepts.
- Wed Feb 28, 2018 10:36 pm
- Forum: General Rate Laws
- Topic: Overall order [ENDORSED]
- Replies: 6
- Views: 1023
Re: Overall order [ENDORSED]
We will need to know the overall order, if given experimental data (in order to right a rate law). However, for integrated rate laws, as of right now, we are only are dealing with zero, first, and second orders, and only one reactant.
- Wed Feb 21, 2018 10:57 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Notation
- Replies: 2
- Views: 366
Re: Notation
And remember, each side is usually written (anode reactant, anode product) and (cathode reactant, cathode product).
- Wed Feb 21, 2018 10:55 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: E and Eo
- Replies: 2
- Views: 1265
Re: E and Eo
E depends on the concentrations of the products and reactants. However, Eo is at standard state, and with respect to a hydrogen electrode.
- Tue Feb 20, 2018 3:09 pm
- Forum: Balancing Redox Reactions
- Topic: 14.115
- Replies: 2
- Views: 450
14.115
This problem states that "the aluminum air fuel cell is used as a reserve battery in remote location. In this cell , aluminum reacts with the oxygen in air in basic solution. It asks for the oxidation/reduction half reactions. However, for the oxidation, the answer key shows Al-->Al(OH)3. How w...
- Wed Feb 14, 2018 2:32 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Constant Pressure
- Replies: 2
- Views: 402
Re: Constant Pressure
Lucian1F wrote:For a constant volume, not pressure, the work is 0 so U=q=H. The example you stated says U=q at constant volume
According to the example 8.6b, it is at constant pressure.
- Wed Feb 14, 2018 2:19 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Constant Pressure
- Replies: 2
- Views: 402
Constant Pressure
How come at constant pressure, for the first law, delta U=q=delta H? Why is there no work being done? An example of this is on pages 281-282 for example 8.6 where it asks for the change in internal energy at constant pressure.
- Tue Feb 13, 2018 2:52 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: First Law
- Replies: 5
- Views: 996
First Law
So delta U is 0 when it is an isothermal, reversible expansion. However, what if the expansion is irreversible? Is it still zero? Also, when is q in the first law zero?
- Tue Feb 13, 2018 2:50 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reversible but not-isothermal expansion?
- Replies: 3
- Views: 502
Re: Reversible but not-isothermal expansion?
That could work. However, delta U would have to be given. But we do have an equation for a reversible reaction that is not isothermal for work.
- Tue Feb 13, 2018 2:49 pm
- Forum: Phase Changes & Related Calculations
- Topic: Reversible
- Replies: 5
- Views: 1141
Re: Reversible
Reversible is when there is an infinitesimally small change, the reaction can be "reversed" and is not greatly affected. On the other hand, a irreversible reaction is a large change that is can be specifically pinpointed.
- Tue Feb 13, 2018 2:48 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: deltaS total spontaneity question 9.73
- Replies: 1
- Views: 277
Re: deltaS total spontaneity question 9.73
Hi! This relates to question 9.73 in the book: "Under what conditions, if any, does the sign of each of the following quantities provide a criterion for assessing the spontaneity of a reaction? (a) G ; (b) H ; (c) S ; (d) delta S total" I thought that if delta S total was negative the rea...
- Wed Feb 07, 2018 10:59 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 9.103
- Replies: 4
- Views: 591
Re: 9.103
Minie 1G wrote:So how would you tell whether the equations, A and B, are spontaneous or not?
If the ΔG is negative for the reaction, it is spontaneous. If it is positive, it is non spontaneous. Another way you could do it is by calculating the total ΔS. If ΔS total is greater than 0, the reaction is spontaneous.
- Wed Feb 07, 2018 10:56 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 9.51 [ENDORSED]
- Replies: 3
- Views: 595
Re: 9.51 [ENDORSED]
Exothermic reactions transfer heat from the system to the surroundings. One of the common formulations of the 2nd Law of Thermodynamics is that the entropy of the universe always increases. This means that exothermic reactions are more likely to be spontaneous. If you consider the relationship ΔG =...
- Wed Feb 07, 2018 10:53 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 9.89 [ENDORSED]
- Replies: 1
- Views: 183
9.89 [ENDORSED]
I don't understand the explanation of the book. In previous examples, it has said that entropy of dissolving decreases for the surroundings (thermally) and increases for the system (positionally) (positive overall). Therefore, why are some still negative? The answer speaks of errors in reference poi...
- Thu Feb 01, 2018 2:12 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: sign of entropy
- Replies: 11
- Views: 1694
Re: sign of entropy
How do I know whether the entropy has a "+" or a "-"? It depends on the the ratio of final to initial temperature, volume, and/or pressure. You can logically think about by analyzing whether the number of microstates is increasing or decreasing, which can give an indication to w...
- Thu Feb 01, 2018 2:11 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Regarding the equation deltaS=nCln(Tf/Ti)
- Replies: 3
- Views: 1427
Re: Regarding the equation deltaS=nCln(Tf/Ti)
melissa carey 1f wrote:Also, when do we need to include n, the number of moles, as I see it omitted in some forms of the equations? Thanks!
You pretty much always include them for entropy calculations. Because the units have to cancel out to leave you with J/K.
- Thu Feb 01, 2018 2:09 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 9.11 [ENDORSED]
- Replies: 3
- Views: 415
Re: 9.11 [ENDORSED]
We are not given values for V or T in this problem. Only n and P . Thus, two of the unknowns in the ideal gas equation of state PV = nRT are left unknown. The information that the change occurs isothermally is enough for us to use the formula \Delta S = nRln\frac{V_{f}}{V_{i}} but since we are give...
- Thu Jan 25, 2018 10:42 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Internal Energy
- Replies: 5
- Views: 527
Re: Internal Energy
William Lan 2l wrote:If delta P = 0 (constant pressure), why is delta U = q + w? I thought that w = -PdeltaV. If P is 0, there would be no work then right?
That is a variation of the original equation. It all depends on what the environment/surrounding/situation is and whether the reaction is reversible or not.
- Thu Jan 25, 2018 10:41 pm
- Forum: Calculating Work of Expansion
- Topic: Expanding VS Compressing
- Replies: 2
- Views: 314
Re: Expanding VS Compressing
Cristian Carrasco 1F wrote:If a system is expanding would that be the system doing work? and would Delta U be positive or negative
Delta U would depend on both q and w, not just q. If a system is expanding, it is doing work. If it is being compressed, work is being done on the system, and thus is a positive value.
- Tue Jan 23, 2018 8:40 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3966501
Re: Post All Chemistry Jokes Here
Organic chemistry is difficult. Those who study it have alkynes of trouble.
- Tue Jan 23, 2018 8:39 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat vs. Enthalpy
- Replies: 5
- Views: 373
Re: Heat vs. Enthalpy
so when using delta H, is it wrong for someone to refer to that as heat? delta H is enthalpy right? Heat and enthalpy are only equal when pressure is constant and volume is constant. That is why Dr. Lavelle wrote the equation qp=delta H. If these are not constant, you have to assume that Delta U=De...
- Tue Jan 23, 2018 8:12 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Units
- Replies: 2
- Views: 294
Units
When is delta H in kJ/mol or just kJ? (because the book uses both units)
- Thu Jan 18, 2018 6:29 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Energy and matter?
- Replies: 6
- Views: 738
Re: Energy and matter?
Yes. That is correct. Isolated let’s nothing in or out.
- Thu Jan 18, 2018 6:27 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat vs. Enthalpy
- Replies: 5
- Views: 373
Re: Heat vs. Enthalpy
Enthalpy is heat but not heat is enthalpy.
- Thu Jan 18, 2018 6:26 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Specific Heat Capacity vs Heat Capacity
- Replies: 5
- Views: 586
Re: Specific Heat Capacity vs Heat Capacity
Heat capacity doesn’t take into account how much of a substance is there. It doesn’t include grams or moles
- Wed Jan 10, 2018 6:50 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 5
- Views: 498
Re: Bond Enthalpies
Yes and no. You are just adding the values together. The values of energy required are always positive and the values of energy released are negative. So just add the positive and negative values.
- Wed Jan 10, 2018 6:47 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity vs. Specific Heat Capacity
- Replies: 6
- Views: 1094
Re: Heat Capacity vs. Specific Heat Capacity
It's basically just about the units. It depends whether you are using grams or moles.
- Wed Jan 10, 2018 6:46 pm
- Forum: Phase Changes & Related Calculations
- Topic: Why can state properties be added?
- Replies: 11
- Views: 1306
Re: Why can state properties be added?
They cannot be changed by intrinsically. That allows for them to be added. For example, work cannot be added together because of how "it is prepared." Either force or distance can be changed. But energy "preparation" is the same, and likewise for all state properties, allowing th...
- Sat Dec 09, 2017 9:35 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding Water
- Replies: 2
- Views: 330
Adding Water
The book specifies that adding water will only shift an equilibrium if the other products or reactants are not dilute. However, if they are dilute, it says that we can assume that the concentration is unchanged. Will this be specified, whether the products or reactants are dilute in solution or not,...
- Sat Dec 09, 2017 9:19 am
- Forum: Octet Exceptions
- Topic: Radical Confusion
- Replies: 3
- Views: 507
Radical Confusion
I've heard many conflicting arguments whether when assigning a radical, formal charge or electronegativity is more important. Some say that the electron is assigned to the atom of the lower electronegativity. However, in the book, there is a homework problem of CL-O where chlorine has a full octet w...
- Fri Dec 08, 2017 1:54 pm
- Forum: Conjugate Acids & Bases
- Topic: Acid Strength Comparison. 12.115A [ENDORSED]
- Replies: 1
- Views: 367
Acid Strength Comparison. 12.115A [ENDORSED]
If we are given only the structures of two conjugate bases from weak acids and are asked to compare which acid is stronger, how would we tell from the molecular structure? For example, in 12.115A, it asked whether carbonic acid would act as an acid or base in an acetate solution, without looking at ...
- Wed Dec 06, 2017 9:09 pm
- Forum: Lewis Acids & Bases
- Topic: Strength [ENDORSED]
- Replies: 1
- Views: 292
Strength [ENDORSED]
When we were talking about bond character and polarizability and polarizing power, we said that those with higher polarizing power and higher polarizability express more covalent character than ionic character and becomes less soluble. However, does this only apply to salts? Because, this seems to b...
- Wed Dec 06, 2017 9:48 am
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Reason for not including water
- Replies: 6
- Views: 752
Re: Reason for not including water
Both your reasons that you stated are equally correct. Remember though than in Le Chatelier's Principle, the concentration of everything can be affected by the addition or subtraction of water.
- Wed Dec 06, 2017 9:46 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: ICE Chart [ENDORSED]
- Replies: 9
- Views: 1323
Re: ICE Chart [ENDORSED]
It's okay to use an ICE chart whenever there is a reaction. It just depends what you put for the starting and change values. For a strong base/acid, the change will cause the reactant base/acid to go to 0 while for weak base/acid, there will be some reactant still left over.
- Mon Dec 04, 2017 10:57 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Acid Strength
- Replies: 1
- Views: 212
Acid Strength
When determining acid strength comparisons, which is more important: bond length or polarity of the bond? It seems to differ between oxoacids/carboxylic acids and acids like HF, HBr, HI, and HCl.
- Fri Dec 01, 2017 9:18 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3966501
Re: Post All Chemistry Jokes Here
I'm out of chemistry jokes. I should zinc of a new one.
- Mon Nov 27, 2017 2:34 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Chem Equilibrium Module 4 #15 [ENDORSED]
- Replies: 6
- Views: 1109
Re: Chem Equilibrium Module 4 #15 [ENDORSED]
In this situation, liquid water is a part of the reaction. According to Le Chatelier's Principle, if more reactant is added then more CO2 will react and more product will be made. If the reaction did not include water however, then the addition of water will not affect the amount of product that is...
- Mon Nov 27, 2017 2:31 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Homework 4.13
- Replies: 3
- Views: 517
Re: Homework 4.13
P can have an expanded octet. You want to achieve the lowest normal charge possible. That is when O has two bonds and two lone pairs. This gives it a formal charge of 0. If it only had one bond, it would have a formal charge of -1.
- Mon Nov 27, 2017 1:24 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Bidentates
- Replies: 1
- Views: 245
Bidentates
If a compound is a tridentate for example, will it only act as a tridentate, or could it be a bidentate or monodentate?
- Wed Nov 22, 2017 3:55 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Using the ICE Box
- Replies: 2
- Views: 356
Re: Using the ICE Box
The bars are another way of writing molarity or concentration. []=molarity
- Wed Nov 22, 2017 3:54 pm
- Forum: Lewis Structures
- Topic: Extended Octets
- Replies: 1
- Views: 214
Re: Extended Octets
Look at their hybridization and how many orbitals are half filled as well as their location in the periodic table.
- Wed Nov 15, 2017 10:23 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Difference Between Orbitals and Subshells [ENDORSED]
- Replies: 7
- Views: 1882
Re: Difference Between Orbitals and Subshells [ENDORSED]
Remember when it asks for sub shell designation, it means both n and l as well (e.g. 4s, 2p, etc...).
- Wed Nov 15, 2017 10:22 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Bond Angles
- Replies: 8
- Views: 1585
Re: Bond Angles
Usually with bond angles and molecular/electron shape, it is pure memorization and nothing more. However, most of the bond angles are relatively easy to figure out by using logic and working through the lewis structure.
- Tue Nov 07, 2017 5:12 pm
- Forum: Octet Exceptions
- Topic: Radical Lewis Structures
- Replies: 4
- Views: 3214
Radical Lewis Structures
If a molecule has an unpaired electron, where does this electron go? Should the Lewis structure be made so that the lowest formal charge is achieved and that determines the placement of this electron?
- Tue Nov 07, 2017 4:37 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Configuration of Ions
- Replies: 2
- Views: 333
Re: Electron Configuration of Ions
Remember, atoms want to be in the lowest energy and most stable state. This is either when all the orbitals are filled or none are filled. For group 13, they lose 3 electrons so that they reach noble gas configuration. Noble gasses are in the most stable state. They neither accept nor donate electro...
- Tue Nov 07, 2017 4:32 pm
- Forum: Octet Exceptions
- Topic: Resonance Structures and Isomers
- Replies: 2
- Views: 826
Re: Resonance Structures and Isomers
A resonance structure means that the molecule is the same but the bonds can be interchanged. The bonds blur together in (dotted line). In isomers, this is referring to only organic compounds. The bonds do not blur with one another. Resonance structures can refer to both organic and inorganic molecul...
- Mon Nov 06, 2017 6:12 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3966501
Re: Post All Chemistry Jokes Here
Chemists never die. They just reach equilibrium.
- Wed Nov 01, 2017 10:30 am
- Forum: Trends in The Periodic Table
- Topic: Chapter 2, #93
- Replies: 3
- Views: 346
Re: Chapter 2, #93
When in ground state and having lost or gained no electrons, atomic radius increases from right to left and down. However, when ions come into play, because those on the right of the periodic table gain electrons, they have an expanded shell and thus have a larger radius than cations. But, in all, a...
- Wed Nov 01, 2017 10:28 am
- Forum: Octet Exceptions
- Topic: Octet Rule [ENDORSED]
- Replies: 1
- Views: 381
Octet Rule [ENDORSED]
Which takes priority? Should you have a lower formal charge with an expanded octet or higher formal charge with the 8 valence e-? And should you try to the central atom to have the lowest formal charge in all?
Thanks!
Thanks!
- Wed Oct 25, 2017 9:44 am
- Forum: Quantum Numbers and The H-Atom
- Topic: 4s before 3d
- Replies: 3
- Views: 11355
Re: 4s before 3d
Why exactly do electrons fill up the 4s orbital before filling up the 3d? And why when writing out the configuration must we write 3d before 4s? It all depends on the where the atom is on the periodic table. If d is 4/5, or 9/10, then d fills up first (goes to the higher number). If not these scena...
- Wed Oct 25, 2017 9:41 am
- Forum: Properties of Electrons
- Topic: Rydberg Equation [ENDORSED]
- Replies: 6
- Views: 1076
Re: Rydberg Equation [ENDORSED]
Rydberg's Equation describes the change in energy. Change is always final-initial, except in very few specific cases.
- Tue Oct 17, 2017 7:49 pm
- Forum: Properties of Electrons
- Topic: Rydberg's formula
- Replies: 6
- Views: 1083
Re: Reinberg's formula
It's easier to think about in terms of E=-hR/n^2. Then, calculated the change of final-initial. Or use energy to get wavelength or frequency. Hope this helps!
- Tue Oct 17, 2017 7:46 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: ch1 question 43
- Replies: 8
- Views: 1146
Re: ch1 question 43
Set up the equation like this. The change in momentum times the change in position has to be greater than or equal to h/4pi. Momentum is mv of an electron. v is the unknown but you do know the position. So, plug in these numbers (9.110x10^-31 kg)(x m/s)(350.x10^-12 m)>/(6.626x10^-34 Js)/4pi. Solve t...
- Tue Oct 10, 2017 10:32 pm
- Forum: Properties of Light
- Topic: Chapter 1 #3
- Replies: 9
- Views: 1031
Re: Chapter 1 #3
EM radiation can be seen through the particle lens. If the frequency is decreasing, the energy of the field/wave is decreasing as well. With relation to an electric field, if the frequency, hence the energy decreases.
- Tue Oct 10, 2017 10:29 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Chapter 1 question 15
- Replies: 4
- Views: 994
Re: Chapter 1 question 15
Laura Riccardelli wrote:How often will be asked to apply Rydberg's equation in this class?
Usually, you can assume to apply the Rydberg equation whenever there is a change in energy level, say from n=2 to n=1, etc... Other than that scenario, the Rydberg equation is not that useful.
- Wed Oct 04, 2017 11:02 am
- Forum: Balancing Chemical Reactions
- Topic: Combustion Reaction Water Phase
- Replies: 2
- Views: 735
Re: Combustion Reaction Water Phase
joshuaxian wrote:During a combustion reaction of an organic compound, is water vapor usually produced, or are there situations in which liquid water is produced instead?
usually water vapor unless otherwise stated.
- Wed Oct 04, 2017 10:42 am
- Forum: Molarity, Solutions, Dilutions
- Topic: HW Problem E35
- Replies: 5
- Views: 1093
Re: HW Problem E35
As a follow-up question for Problem E35, I was wondering how you know the conversion of 1 mol Ca5((PO4)3)OH is exactly 1 mol Ca5((PO4)3)F ? Is it assumed since the problem doesn't state otherwise? That was the whole point of the percent increase problem. If you have a certain number of grams of Ca5...
- Tue Oct 03, 2017 10:49 pm
- Forum: Significant Figures
- Topic: All students read this sig fig post [ENDORSED]
- Replies: 170
- Views: 37193
Re: All students read this sig fig post [ENDORSED]
Do you know if the problems will specifically tell us how many significant figures to use? No. With the numbers that are given, you should know how many sig figs to use. But when using molecular mass, the best number is 3-4 sig figs. When in doubt, use 3 sig figs. Other than that, always apply the ...