## 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: 196

### 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: 30
Views: 799

### 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: 148

### 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: 135

### 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: 1862

### 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: 82

### 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: 97

### 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: 99

### 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: 121

### 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: 121

### 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: 260

### 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: 124

### 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: 183

### 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: 247

### 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: 419

### 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: 146

### 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: 419

### 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: 87

### 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: 104

### 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: 91

### 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: 119

### 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: 187

### 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: 196

### 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: 131

### 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: 136

### 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: 139

### 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: 97

### 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: 164

### 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: 79

### 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: 148

### 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
Thu Jan 10, 2019 8:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th Edition Question 5G.3 B
Replies: 2
Views: 81

### 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: 152

### 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: 152

### 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: 113

### 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: 177

### 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: 342

### 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: 325

### 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: 382

### 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: 140

### 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: 113

### 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: 87

### 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
Replies: 8
Views: 461

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: 431

### 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: 176

### 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: 158

### 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: 192

### 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: 97

### 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: 227

### Re: Determining Central Atom

Tue Nov 27, 2018 3:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Bond Angle
Replies: 3
Views: 70

### 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: 73

### 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: 189

### 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: 100

### 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: 235

### 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: 418

### 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: 487

### 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: 137

### 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: 377

### 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: 642

### 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: 294

### 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: 680

### 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: 112

### 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: 176

### 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: 123

### 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: 404

### 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: 128

### 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?
Thu Oct 18, 2018 8:19 pm
Forum: Properties of Light
Topic: Speed of Light
Replies: 5
Views: 286

### 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: 179

### 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: 323

### 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: 188

### 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: 241

### 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: 102

### 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
Thu Oct 11, 2018 11:35 pm
Forum: Properties of Light
Topic: Kinetic energy equation
Replies: 4
Views: 125

### 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: 241

### 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: 332

### 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!
Thu Oct 04, 2018 5:39 pm
Forum: Empirical & Molecular Formulas
Topic: Homework Problem F.3 (part a)
Replies: 2
Views: 118

### 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: 120

### 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: 332

### 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...