Search found 62 matches
- Thu Mar 14, 2019 10:04 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Units of k
- Replies: 5
- Views: 904
Re: Units of k
The unit of k for a zero-order reaction is mol L-1 s-1; for a first-order reaction is s-1; For a second-order reaction is L mol-1 s-1.
- Thu Mar 14, 2019 9:31 pm
- Forum: General Rate Laws
- Topic: intermediate molecules
- Replies: 3
- Views: 489
Re: intermediate molecules
Intermediate molecules are not included in general rate laws because only reactants are, but they can be included if you break down the reaction mechanism and look into the rate for each step.
- Fri Mar 08, 2019 4:23 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Ecell and pH
- Replies: 3
- Views: 656
Re: Ecell and pH
I think E'cell is the standard E which is the same as E°. It is a fast way in my opinion because otherwise, you need to calculate pH from lnQ.
- Fri Mar 08, 2019 4:19 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: E˚ vs E
- Replies: 13
- Views: 15202
Re: E˚ vs E
E and E°can be calculated by the formula E = E°- (RT/nF) lnQ.
- Fri Mar 08, 2019 4:17 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: E° is 0 for Concentration Cells
- Replies: 3
- Views: 378
Re: E° is 0 for Concentration Cells
Standard E = 0 only when there is the same material on both sides. Otherwise, you will need to calculate by subtracting the right side by the left side.
- Fri Mar 08, 2019 4:14 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6th edition 14.35
- Replies: 3
- Views: 392
Re: 6th edition 14.35
I think the correct equation for this is In3+ (aq) + e- -----> In2+ (aq). This is from my solution manual.
- Fri Mar 08, 2019 4:07 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Electrochemistry
- Replies: 3
- Views: 437
Re: Electrochemistry
Because the actual reaction going on is the reverse of formation of Tl3+, resulting in the standard Gibbs Free energy being the opposite.
- Fri Mar 08, 2019 3:46 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Q: Partial Pressures and Concentration?
- Replies: 4
- Views: 1219
Re: Q: Partial Pressures and Concentration?
For the calculation of Q and K, the equation is that Q = (The concentration x pressure of Products)/(The concentration x pressure of reactants) in the case there are two or more products or reactants which each contains both concentration and pressure.
- Wed Feb 27, 2019 4:03 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cell Inert Component
- Replies: 1
- Views: 229
Galvanic Cell Inert Component
When we are asked to put a reaction equation into a cell diagram, how do we know if an inert component such as Pt should be included? Or it will always be mentioned in the question (since some question does not mention Pt but the ask has it)?
- Wed Feb 27, 2019 3:56 am
- Forum: Balancing Redox Reactions
- Topic: Gibbs Free Energy
- Replies: 2
- Views: 461
Re: Gibbs Free Energy
First, you need to write down the half-oxid and half-red equations for the reaction. When you balance it out, I find the electron flow of the reaction which is the number of e- being canceled on each side. Use this number as n to find the △G with △G= -nFE.
- Wed Feb 27, 2019 3:52 am
- Forum: Balancing Redox Reactions
- Topic: Oxidizing and Reducing Agent
- Replies: 4
- Views: 392
Re: Oxidizing and Reducing Agent
Yes. When an element in reactant is both oxidized and reduced in two products, it is both agents.
- Sat Feb 23, 2019 6:40 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneity
- Replies: 8
- Views: 781
Re: Spontaneity
△G determines whether a reaction can happen spontaneously. Negative △G is spontaneous, and positive △G is not. It is also related to which way of reaction can be more stable. The lower △G is, the more stable it is.
- Sat Feb 23, 2019 6:36 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Change in Gibbs Free Energy
- Replies: 3
- Views: 702
Re: Change in Gibbs Free Energy
△G with Degree means it is the standard Gibbs free energy. Without a degree is not standard. It can be calculated by △G = standard△G + RTlnQ.
- Thu Feb 21, 2019 3:58 am
- Forum: Phase Changes & Related Calculations
- Topic: joules conversion factor
- Replies: 7
- Views: 981
Re: joules conversion factor
The conversion from atm L to J is given on the formula sheet for the tests.
- Thu Feb 21, 2019 3:57 am
- Forum: Phase Changes & Related Calculations
- Topic: Signs in work equations
- Replies: 2
- Views: 344
Re: Signs in work equations
I think the sign of work always depends on if the system does the work or work is done to the system. Once it is determined, the sign of work is figured out.
- Thu Feb 21, 2019 3:54 am
- Forum: Phase Changes & Related Calculations
- Topic: heat of a phase change
- Replies: 5
- Views: 519
Re: heat of a phase change
During the phase change, the heat is called latent heat. The formula is q=mL (L is latent heat capacity).
- Thu Feb 21, 2019 3:50 am
- Forum: Phase Changes & Related Calculations
- Topic: heat units
- Replies: 3
- Views: 396
Re: heat units
I think since C is in J/g, the final answer should be in J.
- Thu Feb 21, 2019 3:48 am
- Forum: Phase Changes & Related Calculations
- Topic: Isothermal
- Replies: 9
- Views: 1074
Re: Isothermal
Normally it is told that the system is isothermal if it is important for solving the problem.
- Thu Feb 21, 2019 3:47 am
- Forum: Phase Changes & Related Calculations
- Topic: Phase Change and Temperature
- Replies: 3
- Views: 430
Re: Phase Change and Temperature
The change in temperature means that the kinetic energy of molecules is changing. While in the phase change, the substance is changing its potential energy. Thus the temperature does not change.
- Thu Feb 21, 2019 3:43 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: units
- Replies: 7
- Views: 974
Re: units
Can the unit for Pressure be other than atm?
- Thu Feb 21, 2019 12:32 am
- Forum: Phase Changes & Related Calculations
- Topic: Steam vs Boiling Water
- Replies: 8
- Views: 1157
Re: Steam vs Boiling Water
Because the process of boiling water intakes energy, and when it becomes steam, the steam has more heat than water.
- Wed Feb 20, 2019 11:49 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Systems
- Replies: 6
- Views: 931
Re: Systems
Simply, an open system means both matter and energy can exchange; A closed system can exchange energy but not matter. An isolated system does not exchange either matter or system.
- Wed Feb 20, 2019 11:36 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Graphs
- Replies: 2
- Views: 304
Re: Graphs
There can be graphs of △H △S and △G. I think the graphs will mainly function to show the change of values.
- Wed Feb 20, 2019 11:33 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: q=mCdeltaT
- Replies: 15
- Views: 8098
Re: q=mCdeltaT
mC represents the specific heat capacity is measured in per unit of mass; nC means the specific heat capacity is measured per mole.
- Wed Feb 20, 2019 3:34 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Direction of a Reaction
- Replies: 8
- Views: 935
Re: Direction of a Reaction
If K is not given, we probably can calculate the K using given information such as concentration. If not, we can not compare K vs Q.
- Wed Feb 20, 2019 3:32 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ignoring x validity
- Replies: 6
- Views: 838
Re: ignoring x validity
That is what we are supposed to do. The formula to calculate x is given on the formula sheet, and it always works for solving the x.
- Wed Feb 20, 2019 3:29 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: increasing pressure, what happens to concentration?
- Replies: 10
- Views: 2420
Re: increasing pressure, what happens to concentration?
When pressure is increased, the reaction wants to do something to reduce the effects. Lowering the number of molecules can decrease the pressure which reduce the effect.
- Wed Feb 20, 2019 3:25 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Midterm Ice Table
- Replies: 6
- Views: 650
Re: Midterm Ice Table
The questions on the midterm should not be solved using approximations. Also, I think there is a statement by the question saying no approximation allowed.
- Wed Feb 20, 2019 3:22 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reverse Reaction
- Replies: 8
- Views: 755
Re: Reverse Reaction
For reverse reactions, it is important to calculate the K value, which k=[P]/[R].
- Wed Feb 20, 2019 3:20 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Midterm
- Replies: 4
- Views: 542
Re: Midterm
I think we need to know strong acids and bases, and others are just weak.
- Wed Feb 20, 2019 3:17 am
- Forum: Ideal Gases
- Topic: 5% rule
- Replies: 12
- Views: 3396
Re: 5% rule
I think it simply means that if x (the change) is less than 5% than it is ok. It is important that the formula x=(-b+/-(b2-4ac)^1/2)/2a always work.
- Wed Feb 20, 2019 3:12 am
- Forum: Ideal Gases
- Topic: atm vs. bar?
- Replies: 25
- Views: 2820
Re: atm vs. bar?
So which one is the right unit for the equation PV=nRT?
- Mon Dec 03, 2018 9:46 pm
- Forum: Air Pollution & Acid Rain
- Topic: Acid Rain
- Replies: 24
- Views: 3803
Re: Acid Rain
One more thing to know is that rain is normally acidic, and the acid rain is when rain is too acidic (more than normal).
- Mon Dec 03, 2018 9:38 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Sigma and Pi Bond with Hybridization
- Replies: 2
- Views: 570
Sigma and Pi Bond with Hybridization
I understand the number of the bond (single, double and triple) results in the type of bond. Can anyone tell me the relationship between the type of bond (sigma and pi) and its hybridization orbital?
- Mon Dec 03, 2018 9:27 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: ph vs pOH
- Replies: 5
- Views: 519
Re: ph vs pOH
The pH is the concentration of H3O+ and calculated by -log[H3O+], whereas the pOH is the concentration of OH- and calculated by -log[OH-]
- Mon Dec 03, 2018 9:03 pm
- Forum: Hybridization
- Topic: Hybridization
- Replies: 5
- Views: 593
Re: Hybridization
Yes, because the Tetrahedral shape has 4 bonds, which is 4 regions of electron density, resulting in an sp3 hybrid orbital.
- Mon Dec 03, 2018 8:57 pm
- Forum: Hybridization
- Topic: Hybrid Orbitals
- Replies: 3
- Views: 393
Re: Hybrid Orbitals
Yes, the number of regions of electron density include bond and lone pairs, which is equal to hybrid orbitals.
- Mon Dec 03, 2018 8:51 pm
- Forum: Hybridization
- Topic: tetrahedral
- Replies: 5
- Views: 497
Re: tetrahedral
The tetrahedral shape has 4 bonds, which in order 1, 2, 3, 4 bonds form s, sp, sp2 and sp3 hybridization.
- Mon Dec 03, 2018 8:45 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Seesaw shape
- Replies: 3
- Views: 371
Re: Seesaw shape
Because of the existence of a lone pair, the bond angles of seesaw shape should be <120 and <90 degrees. I guess less than 180 degrees will work too.
- Mon Dec 03, 2018 8:38 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: bond angle
- Replies: 6
- Views: 485
Re: bond angle
For trigonal planer, the bond angle is exactly 120 degrees. For other shapes, since the lone pair has a stronger force, the bond angle can be slightly smaller than the original angle.
- Mon Dec 03, 2018 8:29 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: polarity
- Replies: 11
- Views: 801
Re: polarity
Molecules with one pair of electrons are polar, but as for two pairs or more, it depends on the shape and if the elements are the same. The graph on the textbook of VSEPR type VS polarity would help.
- Wed Nov 14, 2018 7:30 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Dipole Dipole Forces
- Replies: 3
- Views: 592
Re: Dipole Dipole Forces
The interaction potential energy equation is expressed by (-a1a2)/(r to the sixth). Therefore, the determinations would be the charges of molecules and the distance between them. The distance is more significant because of the 6th power.
- Wed Nov 14, 2018 7:21 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Bond energy value signs
- Replies: 3
- Views: 473
Re: Bond energy value signs
Energy is needed to break a bond and is released to form a bond. You also can understand by looking at the energy equation which starts with a negative sign.
- Wed Nov 14, 2018 7:12 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: States of matter and forces
- Replies: 3
- Views: 471
Re: States of matter and forces
There is no definite determination on which force results in which state of matter because it depends on the element. However, the stronger the intermolecular force is, the more likely it will be solid; the weaker it is, the more to be gas.
- Tue Nov 06, 2018 10:17 am
- Forum: Electronegativity
- Topic: Electronegativity
- Replies: 4
- Views: 402
Re: Electronegativity
When you are asked to calculate the difference of electronegativity, the values will be given. More importantly, you need to know how to compare each element in a periodic table to figure out, for example, which bond has more ionic or covalent characteristics.
- Tue Nov 06, 2018 10:09 am
- Forum: Bond Lengths & Energies
- Topic: Lengths of Bonds
- Replies: 9
- Views: 615
Re: Lengths of Bonds
Because the double bond has a stronger attraction between the atoms, which pulls to form a shorter bond than a single bond.
- Tue Nov 06, 2018 10:06 am
- Forum: Lewis Structures
- Topic: Parenthesis for Ions' Lewis Structures
- Replies: 2
- Views: 374
Parenthesis for Ions' Lewis Structures
In the answer key, I found that when we draw a Lewis structure for an ion, we need to put parenthesis after drawing the diagram and the write the charge on the up right corner. I wonder if it is a necessary step or just a better representation?
- Wed Oct 31, 2018 6:42 am
- Forum: Resonance Structures
- Topic: How to tell when an molecule is resonant?
- Replies: 7
- Views: 1598
Re: How to tell when an molecule is resonant?
This is a good question because the example given in lecture C6H6 has two possible structures, while indeed they are just one turning around. I believe it is still a resonance for the reason that it can also be seen as the change of single bond and double bond of the Cs in the structure.
- Wed Oct 31, 2018 6:32 am
- Forum: Lewis Structures
- Topic: Central Atom
- Replies: 13
- Views: 850
Re: Central Atom
For the Lewis structure, we always choose the atom with the lowest ionization energy as the central atom. Therefore it is C in this case.
- Wed Oct 31, 2018 6:29 am
- Forum: Ionic & Covalent Bonds
- Topic: Covalent Bonds
- Replies: 16
- Views: 1541
Re: Covalent Bonds
No, because metals tend to form cations and nonmetals tend to form anions.
- Thu Oct 25, 2018 4:14 am
- Forum: DeBroglie Equation
- Topic: equation definition
- Replies: 5
- Views: 904
Re: equation definition
De Broglie equation describes the status of a single quantum, which includes the mass and velocity. Therefore, the object has to be in motion.
- Thu Oct 25, 2018 4:11 am
- Forum: *Black Body Radiation
- Topic: Black Body Radiation
- Replies: 4
- Views: 813
Re: Black Body Radiation
Will the concept of Black Body Radiation be tested?
- Thu Oct 25, 2018 2:07 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Spherical Polar Coordinates
- Replies: 1
- Views: 213
Spherical Polar Coordinates
In the textbook, there is a part in chapter 2 describing spherical polar coordinates, but I do not think our professor covered that in classes. Is it a required material for the test?
- Tue Oct 16, 2018 1:12 am
- Forum: Properties of Light
- Topic: E=hv
- Replies: 13
- Views: 1026
Re: E=hv
Since electromagnetic radiation acts like particles, E in this equation stands for the energy per photon.
- Tue Oct 16, 2018 1:02 am
- Forum: Photoelectric Effect
- Topic: Homework Ch. 1 Question 25; 6th Edition
- Replies: 4
- Views: 556
Re: Homework Ch. 1 Question 25; 6th Edition
The question is: Sodium vapor lamps, used for public lighting, emit yellow light of wavelength 589 nm. How much energy is emitted by (a) an excited sodium atom when it generates a photon; (b) 5.00 mg of sodium atoms emitting light at this wavelength; (c) 1.00 mol of sodium atoms emitting light at th...
- Tue Oct 16, 2018 1:00 am
- Forum: Photoelectric Effect
- Topic: Energy Unit of keV
- Replies: 1
- Views: 404
Energy Unit of keV
In homework problem 1.23, the energy is in the unit of keV. I wonder what is its relation to joules and how often do we use it.
- Fri Oct 12, 2018 4:14 am
- Forum: Limiting Reactant Calculations
- Topic: Limiting Reagent
- Replies: 10
- Views: 1560
Re: Limiting Reagent
I would say you do the three reagents together. Find the moles of each one first and figure out which one is the smallest. That is the limiting reagent.
- Fri Oct 12, 2018 4:12 am
- Forum: Empirical & Molecular Formulas
- Topic: Empirical & Molecular Formulas
- Replies: 11
- Views: 1489
Re: Empirical & Molecular Formulas
Yes, they can be the same when the molecule, or the molecular formulas, is at the simplest form, then it is the empirical formula.
- Fri Oct 12, 2018 4:02 am
- Forum: SI Units, Unit Conversions
- Topic: Homework for Week 2
- Replies: 16
- Views: 985
Re: Homework for Week 2
I have the same question that if my discussion is on Friday, can I still do the homework from the previous chapter?
- Fri Oct 05, 2018 3:01 am
- Forum: Balancing Chemical Reactions
- Topic: Balancing reactions tips
- Replies: 29
- Views: 2039
Re: Balancing reactions tips
From my experiences, I usually start with the element that is the least common to the most common or easiest. By meaning the easiest, for example, H2 can be the one because it will be balanced easily so that I leave it for the latest. After you have the fixed number of the least common element, try ...
- Fri Oct 05, 2018 2:49 am
- Forum: Significant Figures
- Topic: Scientific Notation
- Replies: 7
- Views: 379
Re: Scientific Notation
I would say scientific notation is not required except the question asks. It is a way to make your answer clear, so it is up to you to use it or not for most questions as long as you get the right result.
- Fri Oct 05, 2018 2:36 am
- Forum: Administrative Questions and Class Announcements
- Topic: Advice from a Medical Student [ENDORSED]
- Replies: 297
- Views: 382348
Re: Advice from a Medical Student [ENDORSED]
This post is very useful for a biology student like me. Thank you very much!