## Search found 52 matches

Sat Mar 17, 2018 10:46 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetically controlled reactions
Replies: 3
Views: 619

### Re: Kinetically controlled reactions

Kinetically controlled rxn has lower Ea than thermodynamically controlled rxn at higher speed and higher collision frequency as seen in pg 644.
Sat Mar 17, 2018 10:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: I-/I3-
Replies: 3
Views: 974

### Re: I-/I3-

You can tell that this is an oxidation reaction:
I- has an oxidation state of -2
I3- has oxidation of -1 because taken as a whole molecule, each I atom has -1/3 charge
Sat Mar 17, 2018 10:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Potential vs Standard Cell Potential
Replies: 2
Views: 202

### Re: Cell Potential vs Standard Cell Potential

Standard cell potential does not change because it is already calculated from standard conditions (Also! It's an intensive property since it's independent on the amount of substances). However, Ecell can change because it's dependent on the changes in the amounts of substance you have. If you have a...
Sun Mar 11, 2018 9:01 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8042
Views: 1412373

### Re: Post All Chemistry Jokes Here

What do you call a tooth in a liter of water?
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A one molar solution
Sat Mar 10, 2018 8:44 pm
Forum: Second Order Reactions
Topic: the slope
Replies: 12
Views: 781

### Re: the slope

zero order= neg slope
1st order= neg slope
2nd order= pos slope
These are taken from the plots of time vs [A], ln[A], 1/[A] (for the 0th, 1st, and 2nd orders respectively)
Sat Mar 10, 2018 8:39 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: relationship between temperature and rate constants [ENDORSED]
Replies: 2
Views: 197

### Re: relationship between temperature and rate constants[ENDORSED]

Reaction rate is temperature-dependent: Raising the temperature will increase collisions of the molecules, therefore increasing the rate constant (fast reaction).
Sat Mar 10, 2018 6:42 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Change in Enthalpy vs. Change in Entropy [ENDORSED]
Replies: 2
Views: 338

### Re: Change in Enthalpy vs. Change in Entropy[ENDORSED]

Conservation of anything implies that it cannot be created nor destroyed. However, Entropy is not conserved because it's something that is generated from the "disorder" of systems. Also note that the second law of Thermodynamics states that entropy within an isolated system will keep incre...
Sat Mar 10, 2018 6:32 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.111 [ENDORSED]
Replies: 3
Views: 281

### Re: 11.111[ENDORSED]

It's actually 10= e^-(deltaG1)/RT divided by e^- (deltaG2 /RT) because 10=k1/k2
When e^x/ e^y, it becomes e^(x-y)

so then it's e^(-deltaG1 + deltaG2 /RT)
Sun Mar 04, 2018 6:57 pm
Forum: General Rate Laws
Topic: 15.15
Replies: 2
Views: 185

### Re: 15.15

If you increase or decrease a concentration and its rate of reaction also increases or decreases at the same rate, you have a first order reaction
Sun Mar 04, 2018 6:53 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: order of reactant importance
Replies: 2
Views: 210

### Re: order of reactant importance

The order of reactants predicts how many molecules collide together within a reaction. From the order of reactions, you can also figure out whether the concentration of a substance plays a big role in the reaction rate. They allow conclusions to be drawn about the reaction mechanism, and may help to...
Sun Mar 04, 2018 6:19 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Collision Frequency
Replies: 1
Views: 152

### Re: Collision Frequency

hmm Interesting question! Collision frequency deals with an average rate at which 2 molecules colliding each other within a definite space (this is to help predict the average number of collisions that happen) I found this website online that talks more in depth into collision frequency if you wanna...
Sat Feb 24, 2018 4:57 pm
Forum: Balancing Redox Reactions
Topic: 14.5 a)
Replies: 5
Views: 284

### Re: 14.5 a)

Side note: you can add H3O+ (instead of H+) to acidic solutions that needs an O
Sat Feb 24, 2018 4:52 pm
Forum: General Rate Laws
Topic: Reaction Rate
Replies: 3
Views: 208

### Re: Reaction Rate

The reaction rate depends only on concentration of reactants because the initial rate is the maximum rate where few products are being produced (it's easier to study only the forward/irreversible reaction) Also note that the rate of reaction depends on: constant k, concentration of Reactants, and or...
Sat Feb 24, 2018 4:26 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: negative order
Replies: 2
Views: 159

### Re: negative order

A negative order implies that the concentration appears in the denominator of the rate law.
Sat Feb 24, 2018 4:15 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Finding Standard Potential Through Compiling Half-Reactions
Replies: 2
Views: 179

### Re: Finding Standard Potential Through Compiling Half-Reactions

Gibbs free energy is a state function, which means that it takes in account of only the initial and final states of the system. Because it's a state function, we can assume that deltaGs of 2 half reactions can be added together to form the deltaG of the final reaction.
Wed Feb 14, 2018 12:39 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Review Session Question
Replies: 2
Views: 188

### Re: Review Session Question

F, because we don't necessarily have to have a temperature change when having an exothermic process. This is seen in phase changes where temp stays constant, but heat is still transferred.
Tue Feb 13, 2018 2:09 pm
Forum: Phase Changes & Related Calculations
Topic: Exothermic Reaction
Replies: 3
Views: 222

### Re: Exothermic Reaction

Removing heat, in this case, doesn't have to change the temperature. If you look at the phase transition graph, you can see that temperature does not change during phase changes (e.i solid melting or liquid vaporizing). Freezing water would be an exothermic process but during the time that the phase...
Sat Feb 10, 2018 6:10 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: When to use Cv and Cp with entropy
Replies: 1
Views: 283

### Re: When to use Cv and Cp with entropy

For Temperature-dependence entropy,
Cv is used when there is constant volume and changing temperature and the equation you would use is: ΔS = n(Cm,v)ln(T2/T1)
Cp is used for constant pressure and changing temperature and the equation you'd use is: ΔS = n(Cm,p)ln(T2/T1)
Sat Feb 10, 2018 6:02 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13
Replies: 4
Views: 213

### Re: 9.13

It only states "nitrogen gas" without giving any amount of mols, so I think you can just use 1 mol for that one
Sat Feb 10, 2018 4:36 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Clausius Inequality [ENDORSED]
Replies: 2
Views: 212

### Re: Clausius Inequality[ENDORSED]

Hmm I do not think it would be on the midterm

But it's related to ΔS = qrev/T in which you would replace qrev with qirrev

the inequality is: ΔS >= qirrev/T
Sat Feb 03, 2018 12:30 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: Residual Entropy [ENDORSED]
Replies: 2
Views: 245

### Re: Residual Entropy[ENDORSED]

Lower dipole moments mean that molecules are able to move more freely as opposed to being held tightly by stronger dipole moments. Moving freely= more positions can be occupied --> higher residual entropy
Sat Feb 03, 2018 11:47 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy vs. Potential Energy
Replies: 2
Views: 1163

### Re: Gibbs Free Energy vs. Potential Energy

Potential energy, in chemistry, is referred to as energy that can be able to convert to other forms of energy (ex: kinetic) PE id shown when a ball is on the top step of the stairs, accumulating a high potential energy up there due to its location. The ball only needs a soft push to have it rolling ...
Sat Feb 03, 2018 11:37 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy vs. Potential Energy
Replies: 2
Views: 1163

### Re: Gibbs Free Energy vs. Potential Energy

Gibbs Free Energy is the energy available to do work and the equation associated with it is: △G = △H – T△S in relations to enthalpy, temperature, and entropy Because most reactions occur in constant pressure and Temperature, scientists like using Gibbs when △G = 0: the system is in equilibrium when ...
Sat Jan 27, 2018 12:06 am
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: Calculating degeneracy(W)
Replies: 3
Views: 379

### Re: Calculating degeneracy(W)

From my notes, I have
W = 2^N where N is the number of particles
Fri Jan 26, 2018 10:48 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: reversible and irreversible reactions
Replies: 4
Views: 264

### Re: reversible and irreversible reactions

I believe for the purpose of the class, they might tell you whether it's reversible or not and you'd plug in the associated equation. But maybe this link can help you in identifying some of the common example processes of each http://www.idc-online.com/technical_references/pdfs/mechanical_engineerin...
Fri Jan 26, 2018 10:37 pm
Forum: Phase Changes & Related Calculations
Topic: When to use Kelvin or Celsius
Replies: 10
Views: 1972

### Re: When to use Kelvin or Celsius

If no preference stated, I think we should use Kelvin since it's more applicable to a lot of thermodynamic problems.
Sat Jan 20, 2018 6:19 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: 8.5
Replies: 3
Views: 274

### Re: 8.5

Delta U (change in internal energy)= q (heat) + w (work)
It said the piston is doing the work of 340 KJ ONTO the gas in the system.
Since we're focusing on the gas, this means that the gas is receiving positive work done to it (+340 KJ)
so, U= 524 KJ heat + 340 KJ work = 864 KJ
Sat Jan 20, 2018 6:13 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs. Irreversible Process
Replies: 2
Views: 580

### Re: Reversible vs. Irreversible Process

Systems at equilibrium are reversible processes. Imagine you have a gas of 4 atm INTERNAL pressure in a container + a piston pushing down on it with 4 atm EXTERNAL pressure. Since both pressures are equally putting force against each other, the system can't expand much. With that, the changes in V s...
Fri Jan 19, 2018 12:37 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: HW Q.8.49 [ENDORSED]
Replies: 2
Views: 117

### HW Q.8.49[ENDORSED]

Can someone explain to me why we use PV=nRT for this problem? I'm just a little confused on when we can use the ideal gas law. Thank you
Wed Jan 10, 2018 9:59 am
Forum: Calculating Work of Expansion
Topic: Work for reversible vs irreversible process
Replies: 3
Views: 225

### Re: Work for reversible vs irreversible process

Reversible processes are idealized as being fast and efficient. They have more external pressure pushed upon them. Therefore, they perform really slow in transforming all heat into work (constantly maximizing work). However, no real processes are reversible since it just takes way too much time. We ...
Wed Jan 10, 2018 9:41 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: systems [ENDORSED]
Replies: 5
Views: 351

### Re: systems[ENDORSED]

Energy is transferred, but the amount of mercury (matter) is still the same. Closed systems are involved in only heat exchange with the surrounding.
Wed Jan 10, 2018 9:34 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: R in the equation
Replies: 2
Views: 173

### Re: R in the equation

R is the gas constant which is 8.3145 J/ K * mol or 0.08206 L * atm/ (k* mol) depending on the units the questions give you
Thu Dec 07, 2017 8:51 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Lewis Structure of Coordination Compounds
Replies: 1
Views: 144

### Re: Lewis Structure of Coordination Compounds

I would keep them together so that it's easier to see the type and amount of ligands you have bound to a metal.
Thu Dec 07, 2017 8:44 pm
Forum: Bronsted Acids & Bases
Topic: 12.7
Replies: 1
Views: 118

### Re: 12.7

Oxyacids are just acids that contain Oxygen. Page 477 will show you a whole list of them.

Hope this helps!
Thu Nov 30, 2017 11:48 pm
Forum: Naming
Topic: Chromium as a cation
Replies: 2
Views: 233

### Re: Chromium as a cation

Chromium has oxidation numbers tied next to it. For example, Cr3+ would be Chromium (III)
Thu Nov 30, 2017 11:36 pm
Forum: Naming
Topic: HW 29 part C
Replies: 4
Views: 301

### Re: HW 29 part C

Hi,
It's because cyanido is a ligand and cobalt is a metal. You'd put the ligands in ABC order, but metal you put at the end with oxidation numbers.
Fri Nov 24, 2017 5:37 pm
Forum: Naming
Topic: 17.31 d
Replies: 2
Views: 183

### Re: 17.31 d

I'm wondering the same thing...maybe on the test, put Sodium diaquabis(oxalato)ferrate(III) since it follows the rule more? What does everyone else think?
Thu Nov 23, 2017 11:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Expanded octet
Replies: 6
Views: 392

### Re: Expanded octet

For expanded octet, you should know that elements in period 3 and above are able to have beyond a full set of valence electrons and that Boron has less than an octet.
Sun Nov 19, 2017 5:06 pm
Forum: Hybridization
Topic: Shape of Hybrid Orbitals?
Replies: 2
Views: 233

### Re: Shape of Hybrid Orbitals?

I think that 2sp--> linear, 3sp^2 ----> Trigonal Planar, 4sp^3----> Tetrahedral, 5sp^3d ----> Trigonal bipyramidal, 6sp^3d^2 ----> Octahedral
Sun Nov 19, 2017 5:00 pm
Forum: Naming
Topic: HW 29 part C
Replies: 4
Views: 301

### Re: HW 29 part C

If the complex negative charge, -ate is added to the end of the metal's name (in this case Co).
As for Cyanido vs cyano, they're the same ligand, so I think you can use them both. Correct me if I'm wrong, but hope this helps!
Sat Nov 11, 2017 3:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Theory [ENDORSED]
Replies: 2
Views: 202

### Re: VSEPR Theory[ENDORSED]

I believe the rule meant that while the electron density in the area of the multiple bonds is greater than a single bond's, the area/region would still be the same.

I'm also wondering the same thing for Rakhi's 2nd question
Sat Nov 11, 2017 3:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar Bonds vs. Polar Molecules [ENDORSED]
Replies: 5
Views: 1752

### Re: Polar Bonds vs. Polar Molecules[ENDORSED]

Ionic bonds form when the difference in electronegativity is large between the molecules. However, sometimes the electronegativity difference in molecules is not large enough to form ionic bonds. The electrons are not shared equally, creating partially negative and partially positive regions. These ...
Sat Nov 04, 2017 11:21 pm
Forum: Bond Lengths & Energies
Topic: Bond Lengths [ENDORSED]
Replies: 8
Views: 720

### Re: Bond Lengths[ENDORSED]

To elaborate on Christian's post,
Triple bonds are strongest, followed by doubles and single bonds. Bond length decreases as bond strength increases. Shorter bond lengths do not need to be long because attractions pull electrons closer.
Sat Nov 04, 2017 10:33 pm
Forum: Ionic & Covalent Bonds
Topic: Homework Prob 3.37
Replies: 2
Views: 184

### Re: Homework Prob 3.37

For better understanding,
We know E is an atom that is able to take in more than 4 bonds (as we can see in the structure). Atoms in period 3 or later can accommodate for additional electrons (more than the full 8 electron set!)
Sun Oct 29, 2017 1:43 am
Forum: Quantum Numbers and The H-Atom
Topic: Trouble on a question I seen on the internet relating to this topic we learned in class!
Replies: 3
Views: 322

### Re: Trouble on a question I seen on the internet relating to this topic we learned in class!

Hi, I have a different answer for this problem. 1) So I started with Argon since it was in brackets [] 2) the next configuration is 3d10, so I counted 10 elements after Argon--> landed on Nickel 3) the last configuration is 4s2, so I counted 2 more after Ni --> landed on Zinc So zinc is my answer
Sun Oct 29, 2017 1:16 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Equal or greater than or equal to sign?
Replies: 3
Views: 246

### Re: Equal or greater than or equal to sign?

Hi!
I can't quite grasp the concept of this. Can someone clearly explain why the Heisenberg equation is delta X and P is greater than or equal to H bar? Why is it greater than/ equal to?
Sat Oct 21, 2017 10:35 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectroscopy Conceptually
Replies: 3
Views: 273

### Re: Atomic Spectroscopy Conceptually

Hi, You can imagine excited electron movements similar to when you pluck guitar strings. When you pluck on a string, the string vibrates, creating an image of rapid side-to-side movements. This is like electrons in which they move up an energy level and then back down to its original state - this pr...
Sat Oct 21, 2017 10:17 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Principle Quantum Number [ENDORSED]
Replies: 3
Views: 243

### Re: Principle Quantum Number[ENDORSED]

Hi, The principle quantum number (n) is what determines the size of an orbital. Based on my understanding, more energy is needed to be absorbed to excite an electron from the orbital that is closer to the nucleus (n=1) to a farther orbital (n=2). Thus, orbitals for which n=2 is larger than n=1 becau...
Sat Oct 14, 2017 5:13 pm
Forum: Properties of Light
Topic: Electromagnetic Spectrum [ENDORSED]
Replies: 2
Views: 219

### Re: Electromagnetic Spectrum[ENDORSED]

I agree with Deborah. It might be helpful to know the general area like Radio<< microwave<<infrared<< visible<<UV<<X-ray<<gamma rays *Radiowaves have low frequency/longest wavelength *Gamma rays have high frequency/ shortest wavelength I found this funny acronym if you guys would like t use it: Rabb...
Sat Oct 14, 2017 4:38 pm
Forum: Properties of Light
Topic: Photoelectric Experiments:Light [ENDORSED]
Replies: 4
Views: 368

### Re: Photoelectric Experiments:Light[ENDORSED]

Piggybacking on the first respond-- But yes, photoelectric experiments typically use ultraviolet light and sometimes visible light (if used on alkali metals). This is because the photons of UV lights have enough energy to be able to break the binding force of electron emission from a metal's surface...
Mon Oct 02, 2017 3:09 pm
Forum: Limiting Reactant Calculations
Replies: 6
Views: 1250

### Re: Avogadros Number

The Avogadro's number is 6.022 x 10^23 and this number is what defines 1 mole. A "Mole" is similar to the use of "dozen" (12) or "gross" (144). All of these numbers are used to group a certain amount of stuff (such as electrons, atoms, molecules,etc). ** I'd like to not...
Mon Oct 02, 2017 2:43 pm
Forum: Molarity, Solutions, Dilutions
Topic: Help with homework problem E3
Replies: 3
Views: 313

### Re: Help with homework problem E3

Hi, So the picture illustrated that there are 9 galliums atoms on the left and it is asking how many Astatine atoms should be put in to balance out the scale. 1) Given n= # of moles, M= molar mass the equation should be n(1)xM(1) = n(2)xM(2) 2) Find the molar mass of Ga ---> 69.7 g/mol Find molar ma...

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