Search found 77 matches
- Thu Mar 07, 2019 10:19 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test 2
- Replies: 4
- Views: 455
Re: Test 2
I thought we weren't supposed to use the Nernst equation on test 2?
- Thu Mar 07, 2019 9:54 pm
- Forum: Second Order Reactions
- Topic: Final
- Replies: 32
- Views: 2283
Re: Final
I cannot speak with certainty, of course, but I am guessing there will be at least one question that corresponds with each outline, plus a few quick multiple choice/true or false/very short answer questions concept. Certain outlines could also have multiple dedicated questions, like maybe thermo sin...
- Wed Mar 06, 2019 1:10 am
- Forum: Phase Changes & Related Calculations
- Topic: ISOBARIC
- Replies: 3
- Views: 391
Re: ISOBARIC
I've seen it in atm most of the time, but the conversion is 1atm = 760 Torr if you need it.
- Wed Mar 06, 2019 1:06 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: 6th edition 15.19
- Replies: 2
- Views: 330
Re: 6th edition 15.19
I'm not totally sure about the first question; but, as for the second, I do my calculations in mmol and then convert it to mol at the end. I don't think it matters as long as you're consistent.
- Wed Mar 06, 2019 1:03 am
- Forum: First Order Reactions
- Topic: What is the order of a reaction?
- Replies: 2
- Views: 2096
Re: What is the order of a reaction?
In a first order reaction, the reaction rate is proportional to the concentration to the first power. In a second order reaction, the reaction rate is proportional to the concentration squared.
- Wed Feb 27, 2019 3:43 pm
- Forum: Balancing Redox Reactions
- Topic: 6K.5 7th edition
- Replies: 1
- Views: 241
Re: 6K.5 7th edition
I don't think the O3 or O2 is charged since no charge was indicated.
- Tue Feb 26, 2019 4:06 pm
- Forum: Balancing Redox Reactions
- Topic: Substance reduced or oxidized? (14.17)
- Replies: 2
- Views: 275
Re: Substance reduced or oxidized? (14.17)
You have to figure out the oxidation states before and after by finding the charges of each element and matching it to what is given. If the oxidation number goes up, then it is oxidized. If the oxidation number goes down, it is reduced.
- Tue Feb 26, 2019 4:04 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell diagram
- Replies: 4
- Views: 397
Re: Cell diagram
On another post, Chem_Mod said that "if you have two ions (or an ion and a gas), you need a conducting metal that will act as the conductor of electricity for your cell so you have to add in an inert metal (Pt) that will act as the electrode. Solids (for test purposes) should always be placed o...
- Tue Feb 26, 2019 4:00 pm
- Forum: Balancing Redox Reactions
- Topic: basic
- Replies: 3
- Views: 349
Re: basic
7th edition 6K5 is a good practice problem for that.
- Tue Feb 26, 2019 4:00 pm
- Forum: Balancing Redox Reactions
- Topic: basic
- Replies: 3
- Views: 349
Re: basic
It usually works to add the amount of H2O needed to one side and double the amount of OH- to the other side [e.g. you need 4 moles of oxygen: add 4 moles of H2O to one side and 8 moles of OH- to the other]. It just takes a lot of trial and error, for me, but it gets easier the more you do it!
- Sun Feb 24, 2019 7:52 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation and Reduction?
- Replies: 6
- Views: 803
Re: Oxidation and Reduction?
Oxidation is when electrons are lost by something, while reduction is gaining electrons. You can remember this using OIL RIG: Oxidation Is Loss, Reduction Is Gain.
- Wed Feb 20, 2019 6:03 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Midterm Q3D
- Replies: 1
- Views: 280
Midterm Q3D
On question 3D on the midterm, how do we know the states of the reactants and products in the expression for Ka2? (like liquid, aqueous, etc.)
- Wed Feb 20, 2019 5:51 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Porous disc explanation?
- Replies: 6
- Views: 597
Porous disc explanation?
I understand the function of a salt bridge, but how does the porous disk act in the absense of the salt bridge? Is it a different setup entirely?
- Wed Feb 20, 2019 5:50 pm
- Forum: Van't Hoff Equation
- Topic: ΔSº and ΔHº question
- Replies: 5
- Views: 661
ΔSº and ΔHº question
Why can we assume that ΔSº and ΔHº are constant in the Van't Hoff Equation?
- Mon Feb 11, 2019 11:27 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Extensive vs Intensive
- Replies: 7
- Views: 1208
Re: Extensive vs Intensive
Sorry, I meant that heat capacity is extensive and molar/specific heat capacity is intensive!
- Mon Feb 11, 2019 11:15 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Functions [ENDORSED]
- Replies: 2
- Views: 684
Re: State Functions [ENDORSED]
Lyndon said in the review today that the state functions are: PD TV HUGS (pressure, density, temperature, volume, enthalpy, internal energy, gibbs free energy, and entropy). You can remember this by thinking, "I'm under a lot of PRESSURE. I'm feeling DENSE. I just want to watch TV and get some ...
- Mon Feb 11, 2019 11:13 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Extensive vs Intensive
- Replies: 7
- Views: 1208
Re: Extensive vs Intensive
Extensive properties depend on the amount of substance while intensive properties do not. For example, molar heat capacity is an extensive property since it is J*mol^-1*K^-1 while heat capacity is intensive since it is J*K^-1
- Mon Feb 11, 2019 11:11 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Ideal Gas
- Replies: 2
- Views: 264
Re: Ideal Gas
Saying a gas is an ideal gas assumes that it is under perfect conditions so that PV=nRT is true. Basically, it means there are no attractive forces between the gas molecules, and that they occupy all of the available space.
- Mon Feb 04, 2019 4:22 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase change problems
- Replies: 2
- Views: 332
Re: Phase change problems
My TA said that it helps to draw out the graph that Lavelle had on the slides showing why steam causes more severe burns than water at the same temperature. When the graph is diagonal, you use the specific heat of the compound. When it is horizontal, you use latent heat in the calculation.
- Mon Feb 04, 2019 4:19 pm
- Forum: Calculating Work of Expansion
- Topic: Work of Expansion
- Replies: 2
- Views: 287
Re: Work of Expansion
That's correct, expansion work requires that volume is changed as it is the work as a result of the change in volume. The pressure is constant as well, as Edgar said, since it is built into the equation.
- Mon Feb 04, 2019 4:11 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Change of Temp. converting from C to K in Entropy Change Problem
- Replies: 2
- Views: 285
Re: Change of Temp. converting from C to K in Entropy Change Problem
The conversion from Celsius to Kelvin is [K] = [C] + 273.15. So, 37.6ºC would be 310.75 or approx. 310.8ºK. Likewise, 157.9ºC is 431.05 or approx. 431.1ºK.
- Tue Jan 29, 2019 11:05 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Cv versus Cp
- Replies: 4
- Views: 471
Re: Cv versus Cp
It also helps if you look at the calculation. For atoms, Cv is 3/2*R (R being a constant), while for Cp it is 5/2*R.
- Tue Jan 29, 2019 11:00 am
- Forum: Calculating Work of Expansion
- Topic: 4A.3 7th Ed
- Replies: 6
- Views: 520
Re: 4A.3 7th Ed
The change in volume in this question is given by -π*d*r^2. So, it would be -π*(20)*(1.5)^2 = -0.14 cm^3. Then, you multiply that by 1L/1000cm^3 to get it in the right unit, so you have -0.14 L.
- Tue Jan 29, 2019 10:57 am
- Forum: Calculating Work of Expansion
- Topic: reversible process
- Replies: 3
- Views: 329
Re: reversible process
Yes, R is a constant. It only changes slightly due to different units used, but it is typically 8.314 J·K-1·mol-1. You can find this on the Constants and Equations worksheet on the class website.
- Thu Jan 24, 2019 1:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Units
- Replies: 2
- Views: 313
Re: Units
Pressure is in atm or bar, concentration is molarity. Gas has a molar concentration, but I'm not sure what you mean by pressure concentration?
- Wed Jan 23, 2019 11:45 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Strong vs Weak Acids
- Replies: 2
- Views: 308
Re: Strong vs Weak Acids
Like the other answer said, stronger acids have higher concentrations of H+, which leads to a lower pH (more acidic). A weak acid will not fully ionize, so there will be less H+ atoms in solution (lower [H+] = higher pH = less acidic).
- Wed Jan 23, 2019 11:43 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Rounding concentration
- Replies: 2
- Views: 312
Re: Rounding concentration
I think we are supposed to go off what Lavelle usually does, so rounding to sig figs at the very end. Not 100% sure, but it's probably a more accurate answer that way.
- Wed Jan 16, 2019 8:24 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Percentage Ionization
- Replies: 3
- Views: 420
Percentage Ionization
Someone in lecture asked if, for example, the 1.3% ionization meant that only 1.3% of the acid reacted with the water. Is this correct? I didn't catch the answer.
- Wed Jan 16, 2019 8:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6th Edition Homework 11.3
- Replies: 1
- Views: 188
Re: 6th Edition Homework 11.3
I noticed that too, it seems to be balanced if the stoichiometric coefficient on the product side for N2 is 5. Not sure if this is a textbook error or if there's another explanation for it.
- Wed Jan 16, 2019 8:16 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Superacids and Superbases
- Replies: 1
- Views: 344
Re: Superacids and Superbases
These links have some good explanations and examples of superacids and superbases. They say it better than I can, hopefully this helps!
Superacids: http://www.assignmentpoint.com/science/ ... racid.html
Superbases: https://www.thoughtco.com/most-common-s ... ses-603649
Superacids: http://www.assignmentpoint.com/science/ ... racid.html
Superbases: https://www.thoughtco.com/most-common-s ... ses-603649
- Thu Jan 10, 2019 8:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 7th Edition Question 5G.3 B
- Replies: 2
- Views: 237
Re: 7th Edition Question 5G.3 B
I noticed that, too. It might just be a solution manual error, but it's not on the list of errors on the class website. Lavelle did mention in class that the equations have to be balanced to get the right answer, so I think it would be safer to balance it. Maybe the 7 in front of the N2 is supposed ...
- Thu Jan 10, 2019 5:01 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Spontaneous reverse reaction? [ENDORSED]
- Replies: 4
- Views: 365
Re: Spontaneous reverse reaction? [ENDORSED]
So it only means that the reverse reaction will occur?
- Thu Jan 10, 2019 2:59 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Spontaneous reverse reaction? [ENDORSED]
- Replies: 4
- Views: 365
Spontaneous reverse reaction? [ENDORSED]
In the 7th edition textbook on page 416, it says "If Q>K, the reverse reaction is spontaneous...". What does it mean by spontaneous?
- Thu Jan 10, 2019 2:41 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Difference between C and P?
- Replies: 4
- Views: 221
Re: Difference between C and P?
I think that for part b, you would use the concentration because the products are aqueous solutions. Whereas if they were gases, you would use the partial pressure.
- Sat Dec 08, 2018 2:44 pm
- Forum: Naming
- Topic: polydentate complexes?
- Replies: 2
- Views: 417
Re: polydentate complexes?
In a review session, one of the TAs said you look at how many places the ligand can coordinate, and look at if the orientation allows for coordination. For example, NH3 is monodentate because there is a lone pair on the N which allows for coordination. H2O is also monodentate, even though it has two...
- Sat Dec 08, 2018 2:31 pm
- Forum: Significant Figures
- Topic: when to round?
- Replies: 2
- Views: 549
Re: when to round?
As far as I know, we only look at the givens. Constants do not count for sig. figs.
- Sat Dec 08, 2018 2:22 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg’s Equation - Hydrogen
- Replies: 2
- Views: 421
Re: Rydberg’s Equation - Hydrogen
The Rydberg equation applies only to hydrogen atoms (or hydrogen-like atoms with 1 electron). The constant is R=3.28984*10^15 Hz, and is given on the constants and equations sheet attached to the tests.
- Sat Dec 08, 2018 2:16 pm
- Forum: Empirical & Molecular Formulas
- Topic: Midterm Solutions Fall 2018-2019 year
- Replies: 2
- Views: 594
Re: Midterm Solutions Fall 2018-2019 year
You can use either one, but you have to tweak your calculation slightly to account for how many mol of H there are in H2O. Using Molar Mass of H2: 0.3172 g H2O * (1 mol H2O/18.015 g H2O) * (2.0158 g H2/1 mol H2O) = 0.03552 g H Using Molar Mass of H (personally, I use this method): 0.3172 g H2O * (1 ...
- Sat Dec 08, 2018 1:55 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: t shape vs trigonal bipyramidal
- Replies: 1
- Views: 453
Re: t shape vs trigonal bipyramidal
The Chem_Mod answer to this question on another post has a nice explanation for this: viewtopic.php?t=2892
- Tue Dec 04, 2018 6:32 pm
- Forum: Naming
- Topic: 7th edition 9C.3: Potassium Hexacyanidochromate (III)
- Replies: 2
- Views: 317
7th edition 9C.3: Potassium Hexacyanidochromate (III)
The solutions say the formula is K3[Cr(CN)6]3-. Is it K3 since the ion has a 3- charge?
- Tue Dec 04, 2018 11:58 am
- Forum: Bronsted Acids & Bases
- Topic: Bronsted v. Lewis
- Replies: 1
- Views: 254
Re: Bronsted v. Lewis
I believe AlCl3 and Al2O3 and common examples of Lewis acids that aren't Bronsted acids.
- Tue Dec 04, 2018 11:55 am
- Forum: Administrative Questions and Class Announcements
- Topic: About the test
- Replies: 8
- Views: 1023
Re: About the test
Lavelle said that everything in the syllabus will be covered on the final, so I think that anything is fair game. I think he said at least 1 problem per outline, possibly 2 for some.
- Tue Dec 04, 2018 11:53 am
- Forum: Lewis Structures
- Topic: Elements that break the octet rule
- Replies: 6
- Views: 828
Re: Elements that break the octet rule
I think H, He, Li, Be, and anything in group 13 can have an incomplete octet. Any element in row 3 or below can have an expanded octet because of the d-orbital.
- Wed Nov 28, 2018 12:00 am
- Forum: Dipole Moments
- Topic: Polarity of Asymmetrical Molecules
- Replies: 4
- Views: 473
Polarity of Asymmetrical Molecules
Can bent molecules or trigonal pyramidal molecules (and the like) ever be nonpolar?
- Tue Nov 27, 2018 11:55 pm
- Forum: Dipole Moments
- Topic: Drawing dipole moments
- Replies: 3
- Views: 406
Re: Drawing dipole moments
I noticed this too. I believe Lavelle said that, in class, we draw the dipole from the positive to the negative side. As long as you label the delta negative and the delta positive, I'm sure you'll be fine, but I think we are supposed to draw them positive to negative.
- Tue Nov 27, 2018 11:54 pm
- Forum: Hybridization
- Topic: sigma and pi bonds
- Replies: 5
- Views: 480
Re: sigma and pi bonds
I thought that pi bonds were weaker than sigma bonds since the amount of overlap in a sigma bond is greater than that in a pi bond. I try to imagine the lobes of the p-orbitals overlapping in a sigma bond versus a pi bond; the head-to-head overlay > side-to-side overlay.
- Tue Nov 27, 2018 3:58 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: I3-
- Replies: 1
- Views: 199
Re: I3-
I think it would be non-polar since it has no positive/negative "side." It is made up of atoms of the same element, and molecules of this type are usually not polar, and its geometry is symmetric.
- Tue Nov 27, 2018 3:53 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Determining Central Atom
- Replies: 2
- Views: 686
Re: Determining Central Atom
I thought it was the central atom in both?
HCN: http://www.chemeddl.org/alfresco/d/d/wo ... 9f/hcn.png
ClCN: https://nonsibihighschool.org/intbasch11_files/ClCN.png
HCN: http://www.chemeddl.org/alfresco/d/d/wo ... 9f/hcn.png
ClCN: https://nonsibihighschool.org/intbasch11_files/ClCN.png
- Tue Nov 27, 2018 3:46 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Determining Bond Angle
- Replies: 3
- Views: 232
Re: Determining Bond Angle
From my understanding, we use the actual shape (trigonal pyramidal). The bond angle is slightly less than 109.5 because the atom arrangement (which I call the parent shape) is tetrahedral, which has bond angles of 109.5 like you stated. But, trigonal pyramidal shapes have a lone pair, which sort of ...
- Sat Nov 24, 2018 10:06 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: molecular shape vs molecular geometry
- Replies: 3
- Views: 275
Re: molecular shape vs molecular geometry
What the other people said is right, I think. Usually, Prof. Lavelle says the molecular geometry first (the one including lone pairs), then determines molecular shape (the one only including bound atoms).
- Sat Nov 24, 2018 10:00 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sigma and Pi bonds
- Replies: 6
- Views: 621
Re: Sigma and Pi bonds
In short, the difference is that sigma bonds overlap end-to-end and are the strongest covalent bonds, while pi bonds overlap side-by-side. I believe "component orbital" refers to the orbitals that sort of make up the hybrid orbital. For example, in 2sp, the component orbitals would be 2s, ...
- Sat Nov 24, 2018 9:51 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Van Der Waals Forces
- Replies: 1
- Views: 184
Re: Van Der Waals Forces
I believe London Dispersion forces are a subcategory of Van Der Waals forces, so it would apply to them as well. Not totally sure though.
- Sat Nov 17, 2018 6:42 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: End-to-end vs. Side-to-side
- Replies: 2
- Views: 2045
End-to-end vs. Side-to-side
So I know that sigma bonds are end-to-end and pi bonds are side-to-side, but what exactly does this mean? What does are we refering to when we say “end-to-end”?
- Sat Nov 17, 2018 6:40 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 16
- Views: 1161
Bond Angles
Are we supposed to memorize bond angles for different shapes? Or is there a way to calculate them? Just wondering in case it comes up on an exam.
- Sat Nov 17, 2018 6:38 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: tetrahedral vs trigonal planar
- Replies: 9
- Views: 1063
Re: tetrahedral vs trigonal planar
It helps me to just remember that tetrahedral has a general formula of AX4 while trigonal planar has a formula of AX3. (A being the central atom and X being bound atoms)
- Mon Nov 05, 2018 11:42 pm
- Forum: Ionic & Covalent Bonds
- Topic: Identifying compounds
- Replies: 2
- Views: 306
Re: Identifying compounds
I think I remember Professor Lavelle saying that we would almost always be given the formula, but it may help to memorize some common ions, prefixes, and suffixes. To find out which bonds are ionic vs. covalent, I believe you'd have to look at the components of each compound and compare it to what w...
- Mon Nov 05, 2018 11:38 pm
- Forum: Lewis Structures
- Topic: Identifying the element
- Replies: 8
- Views: 913
Re: Identifying the element
I believe that answer would suffice, especially since you brought in formal charge to explain your reasoning.
- Mon Nov 05, 2018 11:36 pm
- Forum: Trends in The Periodic Table
- Topic: Electronegativity vs. Electron Affinity?
- Replies: 11
- Views: 1618
Electronegativity vs. Electron Affinity?
Is one dependent on the other? I know they follow the same trends but I don't quite understand the difference between the two.
- Sat Nov 03, 2018 10:36 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Happy Birthday, Dr. Lavelle!
- Replies: 3
- Views: 446
Happy Birthday, Dr. Lavelle!
Sorry this isn't a question.
- Fri Nov 02, 2018 7:40 pm
- Forum: SI Units, Unit Conversions
- Topic: Molar Mass to Kg
- Replies: 6
- Views: 16874
Re: Molar Mass to Kg
I believe you would divide by Avogadro's number, then convert the grams to kilograms by adding *10^3.
- Thu Nov 01, 2018 12:21 pm
- Forum: Trends in The Periodic Table
- Topic: Implications of ionization energy
- Replies: 2
- Views: 214
Implications of ionization energy
Can someone explain why we place the atom with the lowest ionization energy in the middle of a Lewis structure?
- Thu Nov 01, 2018 12:20 pm
- Forum: Trends in The Periodic Table
- Topic: Atomic radius across a period
- Replies: 3
- Views: 460
Atomic radius across a period
So I know that atomic radius decreases as you move right across a period, but can someone explain why? Is it because there are more protons so they have a stronger pull on the electrons?
- Tue Oct 23, 2018 10:38 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: 1D.25 Seventh Edition
- Replies: 2
- Views: 261
Re: 1D.25 Seventh Edition
The subshell 2d cannot exist since the greatest possible value of l is n-1. So in this case, since n=2, l can only be 1 or 0. l=1 corresponds with p and l=0 goes with s.
- Tue Oct 23, 2018 10:35 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg Equation
- Replies: 7
- Views: 674
Re: Rydberg Equation
I was wondering this as well. The textbook says it's initial-final, so I've been using that for my calculations.
- Tue Oct 23, 2018 10:19 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 1D.23, part c (7th Edition)
- Replies: 2
- Views: 278
1D.23, part c (7th Edition)
The question is: How many orbitals can have the following quantum numbers in an atom: c) n=2
I thought it was 3 (1s, 2s, 2p), but the textbook solutions say the answer is 4. Can someone explain this to me?
I thought it was 3 (1s, 2s, 2p), but the textbook solutions say the answer is 4. Can someone explain this to me?
- Thu Oct 18, 2018 8:19 pm
- Forum: Properties of Light
- Topic: Speed of Light
- Replies: 5
- Views: 592
Re: Speed of Light
My TA said that we should always use whatever is on the formula sheet so we can avoid as much rounding error as possible. Same goes for other constants (h, R, etc.).
- Thu Oct 18, 2018 8:18 pm
- Forum: DeBroglie Equation
- Topic: units
- Replies: 3
- Views: 250
Re: units
Yes, you have to convert the units to SI units in order to cross out the units. It helps if you write out all the units, like 1 J = 1 kg*m^2*s^-2, and then cross off as you go to make sure you get the right conversion.
- Thu Oct 18, 2018 8:04 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Representation
- Replies: 4
- Views: 576
Re: Representation
It gives a range of possible values that the velocity could take on. So, for example, if you have an initial velocity of 5m/s, and you calculated the change in velocity to be +/-2, the final velocity could be between 3 and 7m/s. It can sort of be compared to the margin of error, if that makes sense.
- Tue Oct 16, 2018 11:12 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Wavelengths
- Replies: 5
- Views: 351
Re: Wavelengths
Wavelengths, by convention, can’t be negative as far as I understand. For instance, wavelength is equal to the speed of light over frequency, both of which are always positive values; so, wavelength couldn’t be negative. It’s also usually measured in a unit like meters, which can’t have negative val...
- Fri Oct 12, 2018 10:45 am
- Forum: Properties of Electrons
- Topic: Quantum World
- Replies: 6
- Views: 513
Re: Quantum World
Dr. Lavelle just clarified in lecture that this relationship only applies to electromagnetic radiation, so it can’t be used for all waves.
- Thu Oct 11, 2018 11:40 pm
- Forum: Properties of Electrons
- Topic: HW problem Focus 1 B5 7th edition
- Replies: 2
- Views: 196
Re: HW problem Focus 1 B5 7th edition
I believe 1 keV is equal to 1.6022 x 10^-16 J, so you'd just multiply the amount of keV by that number to convert the units.
140.511 keV * (1.6022*10^-16 J / 1 keV) = 2.25*10^-14 J
140.511 keV * (1.6022*10^-16 J / 1 keV) = 2.25*10^-14 J
- Thu Oct 11, 2018 11:35 pm
- Forum: Properties of Light
- Topic: Kinetic energy equation
- Replies: 4
- Views: 308
Re: Kinetic energy equation
As far as I know, electrons have the same mass of 9.109 x 10^-31 kg.
- Thu Oct 11, 2018 11:30 pm
- Forum: Properties of Electrons
- Topic: Quantum World
- Replies: 6
- Views: 513
Re: Quantum World
Yes, that's correct. Frequency and wavelength have an inverse relationship, so frequency increases as wavelength decreases.
- Fri Oct 05, 2018 1:05 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Molarity and Dilution of a Solution Post Module Assessment Question 25
- Replies: 5
- Views: 664
Re: Molarity and Dilution of a Solution Post Module Assessment Question 25
@Melissa:
The initial volume is 0.020L because only 0.020L of the original solution is diluted. The 0.150L is there so that you can find the initial concentration of the solution. Hope that makes sense!
The initial volume is 0.020L because only 0.020L of the original solution is diluted. The 0.150L is there so that you can find the initial concentration of the solution. Hope that makes sense!
- Thu Oct 04, 2018 5:39 pm
- Forum: Empirical & Molecular Formulas
- Topic: Homework Problem F.3 (part a)
- Replies: 2
- Views: 199
Homework Problem F.3 (part a)
In the homework question F.3 (7th edition), part a, it asks you to write the formula for nitric acid. How would you find this? And will there be questions/parts of questions on exams that ask you to start with writing the formula for a compound from only the name? Sorry if this is a dumb question, I...
- Tue Oct 02, 2018 7:14 pm
- Forum: Limiting Reactant Calculations
- Topic: Confusion on Post-Module Assessment Q18?
- Replies: 1
- Views: 219
Confusion on Post-Module Assessment Q18?
I have done the post-module assessment for the Audio-Visual Focus Topic a couple times, and I keep getting question 18 wrong. It reads: Determine the limiting reagent if 21.4g NH3 reacts with 42.5g O2. 4 NH3 (g) + 5 O2 (g) -> 4 NO (g) + 6 H2O (g) I know I'm doing something wrong because I get that N...
- Tue Oct 02, 2018 7:06 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Molarity and Dilution of a Solution Post Module Assessment Question 25
- Replies: 5
- Views: 664
Re: Molarity and Dilution of a Solution Post Module Assessment Question 25
This will be quite similar to Layal's post, but it may help to see it in a slightly different way! First, I found molar mass of KMnO4: (molar mass K) + (molar mass Mn) + 4(molar mass O) = 39.10g/mol + 54.94g/mol + 4(16.00g/mol) = 158.04 g/mol Then, use KMnO4's molar mass to find how many moles of KM...