## Search found 44 matches

Mon Mar 19, 2018 11:42 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: cis and trans molecules
Replies: 3
Views: 432

### Re: cis and trans molecules

In this post, viewtopic.php?t=27499, it says trans configured molecules have fewer packing positions compared to that of cis, so cis would have more entropy.
Mon Mar 19, 2018 11:13 am
Forum: Balancing Redox Reactions
Topic: periodic trends
Replies: 3
Views: 307

### Re: periodic trends

because the elements in the further upper right corner of the periodic table will have a stronger pull for an electron to fill its shells, their oxidizing powers will be stronger.
Mon Mar 19, 2018 11:10 am
Forum: Calculating Work of Expansion
Topic: reversible and irreversible expansion
Replies: 3
Views: 501

### Re: reversible and irreversible expansion

Yes, I'm pretty sure for this course we used the equation for irreversible expansion W=P(delta)V.
Mon Mar 19, 2018 12:25 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: rate of change
Replies: 4
Views: 314

### Re: rate of change

In terms of rate, and considering a reaction A -> B + C, the rates will be (-1/a)d[A]/dt = (1/b)d[B]/dt = (1/c)d[C]/dt. In finding each rate of each species, you would multiply the unique rate of the reaction by its coefficient.
Mon Mar 19, 2018 12:21 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: arrhenius equation
Replies: 1
Views: 253

### arrhenius equation

What is the value of A exactly? What does it stand for/mean in terms of rates and the rate constant?
Mon Mar 19, 2018 12:20 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation
Replies: 1
Views: 354

### Nernst Equation

What value do you use for N in this equation? Is it the electrons in the balanced redox reaction or the amount of moles?
Mon Mar 19, 2018 12:17 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: mechanism order
Replies: 1
Views: 266

### Re: mechanism order

in this case, you would end up using the steady state approximation, since you can't have intermediates in your rate law.
Mon Mar 19, 2018 12:14 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1178580

### Re: Post All Chemistry Jokes Here

Q: What do chemists call a benzene ring with iron atoms replacing the carbon atoms?
A: A ferrous wheel:
Fe - Fe
/ \
Fe Fe
\ /
Fe - Fe
Mon Mar 19, 2018 12:12 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Difference in cell potential
Replies: 2
Views: 451

### Difference in cell potential

Is the difference in cell potential just the E value calculated through the nernst equations, or is it the difference between E and E(standard)?
Sun Mar 18, 2018 10:07 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: steady state vs pre equilibrium
Replies: 3
Views: 314

### steady state vs pre equilibrium

How would you know when to use either approach to solving for rate law? Are there any factors that would make you assume one over the other?
Sun Mar 11, 2018 11:14 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate constant
Replies: 6
Views: 281

### Re: Rate constant

Also, the rate constant (K) is considered the slope of the graph showing rate of reaction. For first order reactions, the y axis is ln(molar concentration) versus the x axis of time, and the resulting line plotted has a slope of -K, and for second order reactions the y axis is 1/(molar concentration...
Sun Mar 11, 2018 11:04 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Intermediates
Replies: 2
Views: 187

### Re: Intermediates

I think the equations will be given to us (ex. slow and fast reaction equations), so from that we can determine the intermediates. They will appear in both the reactants and products, and can be cancelled out.
Sun Mar 11, 2018 10:56 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: rate law
Replies: 5
Views: 443

### rate law

Just a clarification, is the only way to determine rate law by experiment?
Sun Mar 04, 2018 9:26 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1178580

### Re: Post All Chemistry Jokes Here

How many atoms in guacamole? Avocado's number
Sun Mar 04, 2018 9:22 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell potential and Gibbs free energy
Replies: 1
Views: 124

### Cell potential and Gibbs free energy

When are you supposed to convert gibbs free energy into cell potential (deltaG=-nFE) instead of just subtracting standard cell potentials?
Sun Mar 04, 2018 9:13 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1178580

### Re: Post All Chemistry Jokes Here

Why do chemistry teachers like to teach about ammonia? Because its basic material.
Tue Feb 20, 2018 2:36 pm
Forum: Balancing Redox Reactions
Topic: Balancing
Replies: 2
Views: 4099

### Re: Balancing

It's easier to separate the half reactions, balance them, and then combine. It's less confusing so you want to do the oxidation and reduction reactions separately.
Mon Feb 12, 2018 1:18 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1178580

### Re: Post All Chemistry Jokes Here

What happens to nitrogen when the sun rises?
It becomes daytrogen :3
Mon Feb 12, 2018 1:09 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Test #1 Question 1B
Replies: 3
Views: 208

### Re: Test #1 Question 1B

the bonds broken are 1 C=C, and 1 CL-Cl, while bonds formed are 1 C-C as well as 2 C-Cl bonds. The C-H bonds are left intact throughout the reaction. If you see, in CH2 there are only C-H bonds and no H-H bonds
Mon Feb 12, 2018 1:05 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Pressure
Replies: 3
Views: 223

### Re: Pressure

Pressure does affect work, at least for gases (think our two equations for work that contain pressure). I think in terms of solids and liquids, pressure wouldn't affect because it's extremely hard to compress liquids and solids. Hopefully this answered your question!
Sun Feb 04, 2018 11:41 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy in real life
Replies: 1
Views: 138

### Entropy in real life

This is kind of random, but I was just wondering, how does entropy increase through air conditioning? Or any kind of cold-increasing system?
Sun Feb 04, 2018 11:35 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: test question 5
Replies: 5
Views: 329

### Re: test question 5

I think the idea is that an ideal cooler will not let and heat or matter in or out (thus isolated) and in turn because the contents are inside, they will not be able to change from their original state either.
Sun Feb 04, 2018 11:32 pm
Forum: Phase Changes & Related Calculations
Topic: Determining if reversible or irreversible
Replies: 2
Views: 151

### Re: Determining if reversible or irreversible

I'm pretty sure you have to be told whether it is reversible or irreversible, just make sure to know which equations to know for what kind of reaction.
Sun Jan 21, 2018 11:56 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Internal Energy
Replies: 3
Views: 231

### Internal Energy

Why is internal energy a state function?
Sun Jan 21, 2018 11:49 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Heat and systems
Replies: 3
Views: 249

### Re: Heat and systems

When heat is transferred out of a system, heat is lost so the q value is negative (exothermic). When heat is transferred into a system, heat is gained so the q will be positive (endothermic). I hope this answers your question.
Sun Jan 21, 2018 11:42 pm
Forum: Calculating Work of Expansion
Topic: When to use equation [ENDORSED]
Replies: 3
Views: 198

### When to use equation[ENDORSED]

When would we use this equation -work=-nrt(ln(vf/vi))- versus w=-p(changeinv). I get that we use the first one when the system is in equilibrium, but would a problem explicitly say "this system is in equilibrium/ is reversible?"
Sun Jan 14, 2018 10:42 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1178580

### Re: Post All Chemistry Jokes Here

Q: What fruit contains Barium and double Sodium? A: BaNaNa!
Sun Jan 14, 2018 10:35 pm
Forum: Phase Changes & Related Calculations
Topic: Heat Capacity
Replies: 4
Views: 260

### Heat Capacity

What is the difference between heat capacity and specific heat capacity and why is one an extensive property and the other an intensive property?
Sun Jan 14, 2018 10:24 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1178580

### Re: Post All Chemistry Jokes Here

What element derives from a Norse [censored]? Thorium.
Sat Dec 09, 2017 6:32 pm
Forum: Naming
Topic: Polydentates
Replies: 4
Views: 414

### Re: Polydentates

My TA also pointed out that for a molecule with COO attached, only one oxygen will be a dentate. Since one of the oxygens is double bonded and has 2 lone pairs, and the other is single bonded, only the singled bonded oxygen will be a point of attachment, so don't count every oxygen all the time.
Sat Dec 09, 2017 6:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium partial pressures
Replies: 2
Views: 393

### Equilibrium partial pressures

For question 63 in chapter 11 At 25 C, K =3.2 x 10^-34 for the reaction 2 HCl(g) <-> H2(g) + Cl2(g). If a 1.0-L reaction vessel is filled with HCl at 0.22 bar, what are the equilibrium partial pressures of HCl, H2, and Cl2? Do you have to solve this by first calculating number of moles of HCl using ...
Sat Dec 09, 2017 3:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Changing Kc
Replies: 2
Views: 514

### Changing Kc

In the practice final, question number 32 asks if Kc is x at 400 K, what is Kc if the stoichiometric coefficients are halved? The answer says the root of x or x^1/2, and I know this makes sense mathematically, but doesn't the value of Kc for a reaction only change based on temperature?
Sat Dec 09, 2017 2:26 pm
Forum: Hybridization
Topic: Hybridization
Replies: 2
Views: 190

### Re: Hybridization

For example, with H2O, the Hydrogen has two single bonds to the two oxygens, and 2 lone pairs of electrons- so in conclusion it has 4 areas of electron density and sp3 hybridization. Remember that a double bond or triple bond will count only as one area of electron density.
Sat Dec 09, 2017 2:22 pm
Forum: Bronsted Acids & Bases
Topic: Mg(OH)2
Replies: 2
Views: 243

### Re: Mg(OH)2

It's a weak base because it's only slightly soluble in water.
Wed Dec 06, 2017 2:25 am
Forum: Hybridization
Topic: sp2 hybridization
Replies: 5
Views: 323

### Re: sp2 hybridization

Since there are 3 fluorides, Boron needs 3 lone electrons to bond with them. Since Boron has an electron config. of 1s2 2s2 2p1, an electron in the 2s orbital is excited into a 2p orbital (left with 1s2 2s1 2px1 2py1) which leaves us with 3 orbitals containing lone electrons thus 3 lone electrons. S...
Sun Dec 03, 2017 11:19 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1178580

### Re: Post All Chemistry Jokes Here

"That was sodium funny"
"I slapped my neon that one"
Sun Dec 03, 2017 10:49 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation States
Replies: 4
Views: 284

### Re: Oxidation States

An example: given Pt(NH3)2Cl4 find the oxidation number for Platinum So we know that NH3 is a neutral ligand, and Cl has a -1 oxidation number. Since there are two 0 charge NH3 and four -1 charge Cl, there is a -4 charge by the ligands. To make this compound have an overall charge of 0, Platinum mus...
Sun Nov 26, 2017 11:27 pm
Forum: Ideal Gases
Topic: R in PV=nRT [ENDORSED]
Replies: 7
Views: 506

### Re: R in PV=nRT[ENDORSED]

No, the Rydberg constant relates to atomic spectra and quantum levels of the hydrogen atom. These two constant correlate to different parts of chem.
Sun Nov 26, 2017 11:22 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Reaction constant
Replies: 4
Views: 383

### Re: Reaction constant

I'm pretty sure Lavelle said they would just call it K without specifying, but you should know by the values given in the problem as p has to do with pressure and c with molarity.
Sun Nov 26, 2017 9:37 pm
Forum: Naming
Topic: Cyano vs Cyanido
Replies: 1
Views: 164

### Re: Cyano vs Cyanido

They are interchangeable
Sun Nov 19, 2017 6:49 pm
Forum: Lewis Structures
Topic: Midterm Question: Lewis Structure for HOCO [ENDORSED]
Replies: 6
Views: 992

### Re: Midterm Question: Lewis Structure for HOCO[ENDORSED]

Why can't Carbon be double bonded to both oxygens and the radical electron go on one of the oxygens? Oxygen is more electronegative than Carbon, and if Carbon had 2 double bonds then its orbitals would be filled and formal charge in most places would be the lowest possible.
Sun Nov 19, 2017 6:34 pm
Forum: Hybridization
Topic: Hybridization in General
Replies: 3
Views: 695

### Re: Hybridization in General

Hybridization is basically when atomic orbitals combine to be more suitable for chemical bonds. For example, Carbon has a ground state configuration of 1s2 2s2 2p2, indicating it has two lone electrons. This would mean Carbon is inclined to only bond two electrons, however we know that is not the ca...
Sun Nov 05, 2017 10:58 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals of subshell
Replies: 3
Views: 193

### Re: Orbitals of subshell

Quantitatively, we can find ml by taking negative l to positive l. ml basically tells us how many orbitals there are present and their orientation within a subshell. Ie, we are given a 3p subshell- n would be 3, l would be 2 (n-1), and the possible solutions for ml would be -2,-1,0,1,2.
Sun Nov 05, 2017 7:28 pm
Forum: Lewis Structures
Topic: HW Question 3.41
Replies: 2
Views: 156

### Re: HW Question 3.41

So the way they give you cycline is kind of nice, because they group the location of the elements to help you draw lewis structure. Since carbon is the least electronegative element, we put one in the center, and then build off from there as said in the comment above. Because they give you H2C(NH2)C...