Search found 62 matches
- Tue Mar 12, 2019 6:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6A.19 7th edition
- Replies: 1
- Views: 234
Re: 6A.19 7th edition
I don't have 7th edition but check to see if there's any mL because that would account for the discrepancy.
- Tue Mar 12, 2019 12:14 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5I.13
- Replies: 1
- Views: 251
Re: 5I.13
A smaller equilibrium constant means at equilibrium the reactants are more favored, or it is less likely to decompose. This means that the lower the equilibrium constant, the more stable.
- Tue Mar 12, 2019 12:08 am
- Forum: General Rate Laws
- Topic: slow step
- Replies: 11
- Views: 1370
Re: slow step
It is either stated explicitly or has the smaller k value
- Tue Mar 12, 2019 12:04 am
- Forum: Second Order Reactions
- Topic: Homework, 6th edition, 15.35
- Replies: 3
- Views: 393
Re: Homework, 6th edition, 15.35
Use the formula t1/2= [A]/2k to solve for k, then modify the formula for the other proportions.
eg.
t1/16= 15[A]/16k
t1/4= 3[A]/4k
etc
eg.
t1/16= 15[A]/16k
t1/4= 3[A]/4k
etc
- Mon Mar 11, 2019 11:52 pm
- Forum: Zero Order Reactions
- Topic: zero order in rate law
- Replies: 7
- Views: 1198
Re: zero order in rate law
It is included in the unique rate law but in the overall rate law it is only included if it is greater than zero. If the reactant is zero order then it will be to the power of zero and equal to 1.
- Mon Mar 11, 2019 11:48 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K
- Replies: 1
- Views: 215
Re: K
If it doesn't specify then it doesn't matter. It's usually Kc.
- Sun Feb 17, 2019 7:24 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Calculating entropy
- Replies: 5
- Views: 430
Re: Calculating entropy
If there's a change in pressure/volume, the entropy is dependent on Temperature. If there's a change in Temperature, the entropy is dependent on volume. You've gotta do one before the other or else there's just no calculation (that a 14B student knows how to do, idk about actual chemists).
- Wed Feb 13, 2019 10:25 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Midterm Prep Question
- Replies: 3
- Views: 382
Re: Midterm Prep Question
Thank you! That clears up a lot :)
- Wed Feb 13, 2019 8:17 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Midterm Prep Question
- Replies: 3
- Views: 382
Midterm Prep Question
Q: A balloon expands from 3.3L at 298K to 9.2 x 105 L at 333K. What is ΔS ?
can someone post steps on how to solve?
can someone post steps on how to solve?
- Wed Feb 13, 2019 8:11 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: units
- Replies: 7
- Views: 974
Re: units
P: atm
V: L
n: mol
R: J/k.mol
T: K
V: L
n: mol
R: J/k.mol
T: K
- Tue Feb 12, 2019 11:10 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: R constants
- Replies: 40
- Views: 2111
Re: R constants
It depends on the constants and what needs to cancel. Both values should be provided so you just have to look at the question. It should usually be 8.314 J/k.mol
- Tue Feb 12, 2019 11:04 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Quiz 1 #5
- Replies: 7
- Views: 926
Re: Quiz 1 #5
What day is your discussion, the answers are different depending on the day.
- Tue Feb 12, 2019 11:02 pm
- Forum: Calculating Work of Expansion
- Topic: Substituting -nrT for -PΔV
- Replies: 4
- Views: 484
Re: Substituting -nrT for -PΔV
It will say in the question. Isothermal, same T, moles have to change. Increased Temperature, T changes.
- Tue Feb 12, 2019 11:00 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Boltzmann Equation
- Replies: 3
- Views: 676
Re: Boltzmann Equation
Use the Boltzman constant when finding statistical Entropy
∆S=K•lnW
∆S=K•lnW
- Tue Feb 12, 2019 10:58 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: C
- Replies: 3
- Views: 299
Re: C
Heat capacity
- Tue Feb 12, 2019 7:34 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Review Question
- Replies: 10
- Views: 921
Re: Midterm Review Question
Jim Brown 14B Lec1 wrote:Jim Brown 14B Lec1 wrote:I think you need the bond enthalpy for ethane, then use it to heat water to 100º C and to reach its ∆Hvap
Enthalpy of combustion*
nvm this [censored] is rough idk how to do it :'(
- Tue Feb 12, 2019 7:18 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Review Question
- Replies: 10
- Views: 921
Re: Midterm Review Question
Jim Brown 14B Lec1 wrote:I think you need the bond enthalpy for ethane, then use it to heat water to 100º C and to reach its ∆Hvap
Enthalpy of combustion*
- Tue Feb 12, 2019 7:16 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Review Question
- Replies: 10
- Views: 921
Re: Midterm Review Question
I think you need the bond enthalpy for ethane, then use it to heat water to 100º C and to reach its ∆Hvap
- Tue Feb 12, 2019 5:44 pm
- Forum: Administrative Questions and Class Announcements
- Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
- Replies: 179
- Views: 22862
Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
can someone explain 6(d)? I tried using the additive equation for standard enthalpy of a reaction but I don't think I'm inputting the correct value for it or if that's even a possible way to get the answer We know the total enthalpy needs to equal 42, so add the enthalpies of formation for all the ...
- Tue Feb 12, 2019 5:34 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 4F.11) 7th edition
- Replies: 1
- Views: 187
Re: 4F.11) 7th edition
Yes you can use this for a change in T
- Tue Feb 12, 2019 5:33 pm
- Forum: Student Social/Study Group
- Topic: Equations Sheet
- Replies: 4
- Views: 812
Equations Sheet
Anyone got the supplied equations? :)
- Tue Feb 12, 2019 5:23 pm
- Forum: Phase Changes & Related Calculations
- Topic: Negative and Positive values of delta H and w
- Replies: 6
- Views: 3782
Re: Negative and Positive values of delta H and w
A negative Delt. H means a -q (heat loss)
- Tue Feb 12, 2019 5:12 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Cp vs Cv
- Replies: 1
- Views: 212
Re: Cp vs Cv
The problem will tell you whether it is constant temperature or pressure, either explicitly or through the other information it gives (i.e. ethalphy indicates constant pressure)
- Tue Feb 05, 2019 8:18 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: HW Problem 8.9 6th edition
- Replies: 2
- Views: 346
HW Problem 8.9 6th edition
8.9 An ideal gas in a cylinder was placed in a heater and gained 5.50 kJ of energy as heat. If the cylinder increased in volume from 345 mL to 1846 mL against an atmospheric pressure of 750. Torr during this process, what is the change in internal energy of the gas in the cylinder?
- Tue Feb 05, 2019 7:37 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 7th edition 4F.7
- Replies: 3
- Views: 354
Re: 7th edition 4F.7
Those are used for Entropy calculation at constant Volume or Pressure. Lavelle didn't explain why other than for 3/2 is a result of there being 3 dimensions and velocity being "1/2"
- Tue Feb 05, 2019 7:30 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: temperature of a reversible reaction
- Replies: 3
- Views: 341
Re: temperature of a reversible reaction
The reaction is not isolated and takes place in a heat reservoir. This way, even if the reaction is exothermic, the overall temperature will remain the same at the beginning and the end of the reaction.
- Thu Jan 31, 2019 10:51 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy Calculations (9.1)
- Replies: 7
- Views: 4536
Re: Entropy Calculations (9.1)
2015 Chem class coming in CLUTCH
- Thu Jan 31, 2019 10:51 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy Calculations (9.1)
- Replies: 7
- Views: 4536
Re: Entropy Calculations (9.1)
2015 Chem class coming in CLUTCH
- Thu Jan 31, 2019 10:13 pm
- Forum: Student Social/Study Group
- Topic: Lecture Notes (1/30)
- Replies: 4
- Views: 408
Re: Lecture Notes (1/30)
My handwriting is terrible but
- Thu Jan 31, 2019 10:05 pm
- Forum: Phase Changes & Related Calculations
- Topic: Chemical potential energy
- Replies: 4
- Views: 319
Re: Chemical potential energy
You only have to take the bond enthalpy of the bonds broken and the new bonds formed
- Thu Jan 31, 2019 10:04 pm
- Forum: Phase Changes & Related Calculations
- Topic: Entropy vs Enthalpy concept
- Replies: 3
- Views: 308
Re: Entropy vs Enthalpy concept
Both use J/kg
- Thu Jan 31, 2019 10:02 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Gibbs
- Replies: 5
- Views: 540
Re: Gibbs
If Gibbs Free Energy is negative, the reaction is spontaneous (exergonic). If Gibbs is positive, the reaction is nonspontaneous (endergonic).
The change in Gibbs is equal to the change in enthalpy minus the change in entropy times T.
The change in Gibbs is equal to the change in enthalpy minus the change in entropy times T.
- Tue Dec 04, 2018 7:49 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: strong or weak base
- Replies: 3
- Views: 605
Re: strong or weak base
There are 8 common strong bases worth committing to memory. It consists of Alkali and Alkaline Earth metals paired with Hydroxide Ions. LiOH - lithium hydroxide NaOH - sodium hydroxide KOH - potassium hydroxide RbOH - rubidium hydroxide CsOH - cesium hydroxide Ca(OH)2 - calcium hydroxide Sr(OH)2 - s...
- Tue Dec 04, 2018 7:45 pm
- Forum: Amphoteric Compounds
- Topic: amphoteric oxides
- Replies: 3
- Views: 357
Re: amphoteric oxides
In Lecture Lavelle said we should just commit them to memory. The staircase that is similar to that of the metalloids can be a good guiding line for which oxides this includes.
- Sun Dec 02, 2018 10:28 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis acid/ bronsted acid
- Replies: 1
- Views: 206
Re: Lewis acid/ bronsted acid
All Brönstead acids/bases are Lewis Acids/Bases, but something can be considered a lewis acid even if it might not qualify as a Brönstead acid. This is because a Brönstead acid needs to donate a proton (needs to contain hydrogen) while a Lewis Acid only needs to be able to accept the lone pair.
- Sun Dec 02, 2018 10:25 pm
- Forum: Naming
- Topic: Ions with more than one possible charge
- Replies: 1
- Views: 114
Re: Ions with more than one possible charge
This is only possible with transition metals. Transition metals lose electrons more easily, and they do not lose them based on completing an octet because they utilize the d-orbital.
- Sun Dec 02, 2018 10:23 pm
- Forum: Lewis Acids & Bases
- Topic: Amphoteric Compounds
- Replies: 1
- Views: 222
Re: Amphoteric Compounds
You've just gotta memorize which elements bond to make amphoteric compounds. The list is similar (but not identical) to the list of metalloids.
- Sun Nov 25, 2018 10:33 pm
- Forum: Hybridization
- Topic: pi bonds and rotation
- Replies: 3
- Views: 458
Re: pi bonds and rotation
Pi-bonds do not allow free rotation, if the molecule is rotated, the pi-bond will break. This results in rigidly structured molecules.
- Sun Nov 25, 2018 10:28 pm
- Forum: Hybridization
- Topic: regions of electron density and double bonds
- Replies: 2
- Views: 270
Re: regions of electron density and double bonds
A single bond and a double bond are both 1 region of electron density. Double bonds will determine the different hybridizations and the shape of the molecule, but even with these added it still follows the same rules as the single region of electron density in the VSEPR model.
- Sun Nov 25, 2018 12:36 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3006141
- Thu Nov 15, 2018 9:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 6th Edition Ch4 Q7
- Replies: 2
- Views: 279
Re: 6th Edition Ch4 Q7
There aren't different bond angles, all the angles are the same. You just have to memorize the general rules for the specifics of each shape and apply it to the various molecules that follow that structure.
- Thu Nov 15, 2018 9:03 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Vespr Formula
- Replies: 6
- Views: 529
Re: Vespr Formula
Not sure but it's pretty easy. Its the character A followed by X with a subscript of the number of bonds with another atom, then E with a subscript of the number of lone pairs.
- Thu Nov 15, 2018 9:01 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Linear Shape
- Replies: 5
- Views: 344
Re: Linear Shape
Rosha Mamita 1E wrote:Yes, though the shape will be different and would not be called linear
This is true for most electron geometries and will result in a bent shape, but you can still get a linear shape when there are 5 areas of electron density and 3 of them are lone pairs
- Thu Nov 15, 2018 9:00 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Linear Shape
- Replies: 5
- Views: 344
Re: Linear Shape
Yes, a trigonal bipyramidal electron geometry with 3 lone pairs will give you a linear shape with 180º angles
- Thu Nov 15, 2018 6:50 am
- Forum: Lewis Structures
- Topic: 7th Edition #2E.13
- Replies: 3
- Views: 2844
Re: 7th Edition #2E.13
You want to try and minimize the formal charge
- Thu Nov 15, 2018 6:42 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Geometry vs Electron-Pair Geometry
- Replies: 4
- Views: 2386
Re: Molecular Geometry vs Electron-Pair Geometry
Molecular geometry takes into account only the atoms surrounding the central atom. This includes shapes like bent, trigonal pyramidal, square planar, etc. Electron-pair geometry is based on the number of electron density fields. This includes only the basic geometries (linear, trigonal planar, tetra...
- Thu Nov 15, 2018 6:35 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: The difference between placing lone pairs in certain positions?
- Replies: 3
- Views: 389
Re: The difference between placing lone pairs in certain positions?
It depends on the number of electron fields. See how the T-shaped has five and the square planar has 6? It's worth committing to memory.
- Sun Nov 04, 2018 5:33 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity
- Replies: 3
- Views: 344
Re: Electron Affinity
Electron affinity increases across a period and decreases down a group.
- Sun Nov 04, 2018 5:32 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity
- Replies: 2
- Views: 239
Re: Electron Affinity
The Noble gasses are nonreactive. Neon has a greater effective charge, but its octet is complete, so it won't pick up any electrons, where chlorine will in order to complete the octet.
- Sun Oct 28, 2018 8:58 pm
- Forum: Ionic & Covalent Bonds
- Topic: Variable Valence
- Replies: 2
- Views: 91
Re: Variable Valence
Variable valency just refers to chemicals (typically [if not always?] a metal) that form multiple ions with different charges. (Chemicals like iron (II) and iron (III), tin (III) and tin (IV), etc.)
- Tue Oct 23, 2018 8:47 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3006141
- Mon Oct 22, 2018 11:18 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Calculate orbitals and subshells
- Replies: 3
- Views: 243
Re: Calculate orbitals and subshells
l corresponds to the orbital (s, p, d, f, etc.) Orbitals increase by two for each new shape (s has 1, p has 3, d has 5, etc) The l quantum number 2 represents a p orbital, so there are 3 subshells. The l quantum number 3 represents a d orbital, so there are 5 subshells. The l quantum number 1 repres...
- Fri Oct 19, 2018 9:54 am
- Forum: Properties of Electrons
- Topic: Rydberg Formula 1.13
- Replies: 3
- Views: 386
Re: Rydberg Formula 1.13
Ryberg's constant is 3.29e+15
- Fri Oct 19, 2018 9:51 am
- Forum: Properties of Electrons
- Topic: HW help 1.15
- Replies: 1
- Views: 223
Re: HW help 1.15
Use wavelength to calculate E then work backwards from total Energy. Set up the problem E=Rh(1/(n[final])^2 - 1/(n[initial])^2). Divide everything by hR. You end up with .888 = 1/(n[final])^2 - 1/(n[initial])^2. Test values of integers and you'll end up with a change from 1 to 3.
- Mon Oct 15, 2018 11:08 am
- Forum: Photoelectric Effect
- Topic: 1B.7
- Replies: 2
- Views: 348
Re: 1B.7
Convert wavelength to energy by using the energy formula E=hν. Because νλ is equal to the speed of light this can be rewritten as E=hC/λ. You now have a formula that you can plug in values for and get the energy for one the emission of one atom (3.37 e-17). Next, convert the mass of sodium into atom...
- Sun Oct 14, 2018 10:19 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Email about textbooks
- Replies: 1
- Views: 176
Re: Email about textbooks
I asked Lavelle, he said a pdf is fine. The textbook is to help you learn so whatever works for you.
- Sun Oct 14, 2018 12:41 pm
- Forum: Student Social/Study Group
- Topic: Water
- Replies: 1
- Views: 137
Water
Is water wet? @Dr. Lavelle
- Sun Oct 14, 2018 12:39 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Empirical Equation for H Atom
- Replies: 1
- Views: 196
Re: Empirical Equation for H Atom
The "R" is a constant like "h", "C" or Avogadro's number. It was derived through experimentation.
- Sat Oct 06, 2018 11:05 am
- Forum: SI Units, Unit Conversions
- Topic: Chemistry Community Points
- Replies: 3
- Views: 207
Re: Chemistry Community Points
I meant like if I made a post during week zero (24th-30th) does that count as points for week one?
- Sat Oct 06, 2018 10:18 am
- Forum: SI Units, Unit Conversions
- Topic: Chemistry Community Points
- Replies: 3
- Views: 207
Chemistry Community Points
Do posts made during week zero count as posts for week one?
- Sat Oct 06, 2018 10:02 am
- Forum: General Science Questions
- Topic: Orbitals
- Replies: 2
- Views: 391
Re: Orbitals
The 4S orbital is located closer to the nucleus, so the energy level is higher and will fill out first. It's easy to tell which orbitals have higher energy levels by looking at the organisation of the elements filling those orbitals on the periodic table.
- Sat Sep 29, 2018 7:06 pm
- Forum: Limiting Reactant Calculations
- Topic: Is there a specific way to solve limiting reactant problems?
- Replies: 4
- Views: 407
Re: Is there a specific way to solve limiting reactant problems?
The method I use to solve limiting reactant problems is by converting the reactants' mass into moles. I don't think this is impossible because once you have converted the reactants into moles, you compare the two. The reactant with less moles is the limiting reactant. I believe you can solve these ...