## Search found 64 matches

Mon Mar 12, 2018 4:41 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: Relation between k and activation energy
Replies: 6
Views: 2014

### Re: Relation between k and activation energy

As activation energy decreases, it reduces the energy barrier required for the reaction to proceed therefore the rate constant increases, causes the overall rate of the reaction to increase. Also, if the activation energy is higher, the dependence of the rate constant on temperature increases, meani...
Sun Mar 04, 2018 9:18 pm
Forum: First Order Reactions
Topic: 15.23 c
Replies: 2
Views: 197

### Re: 15.23 c

You can also do the ln(.083/.115)/-115s and you would get the same rate law just know that you have to divide by a negative time to find the rate constant.
Sun Mar 04, 2018 9:15 pm
Forum: First Order Reactions
Replies: 4
Views: 248

Not sure, one of the reactants can be zero order, or it can be a slow step where on of the reactants doesn't necessarily affect the rate.
Mon Feb 26, 2018 1:08 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy???
Replies: 7
Views: 428

### Activation Energy???

Can someone please explain how activation energy has a role in playing during the rate of the reaction and how the overall procedure is affected?
Mon Feb 26, 2018 1:06 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.13c
Replies: 4
Views: 220

### Re: 14.13c

Because the Cl atom is being reduced in this case, therefore it will be the cathode, whereas the anode is increasing therefore it will be the reducing agent in this case so it will be on the left.
Mon Feb 26, 2018 1:04 am
Forum: Balancing Redox Reactions
Topic: Water in balancing reactions
Replies: 4
Views: 269

### Re: Water in balancing reactions

Yes always, however when balancing these reactions make sure that all of the Hydrogens AND Oxygens are balanced, otherwise the reaction will be out of place
Mon Feb 12, 2018 7:26 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Calorimetry
Replies: 2
Views: 184

### Re: Calorimetry

I feel like you would have to do 3, because the ice is changing from lets say -5 degrees celcius to 0 and then melting and then changing from 0 celcius to the final temperature of the water so I feel like you would have three q equations on one side and set that equal to negative of q of the water w...
Tue Feb 06, 2018 11:37 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: G for non-equilibrium
Replies: 2
Views: 181

### Re: G for non-equilibrium

K would be the equilibrium constant and Q is the constant used to understand the ratio between product and reactants at a certain time, therefore, when you use this equation the Gibbs free energy at standard state, can be equal to -RTlnK so you can all of these together and find the Gibbs Free Energ...
Tue Feb 06, 2018 11:35 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: temperature
Replies: 5
Views: 286

### Re: temperature

The things is, even in his solutions for past exams he just puts 273 instead of 273.15, so can someone please ask?
Tue Feb 06, 2018 11:30 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: temperature
Replies: 5
Views: 286

### Re: temperature

The things is, even in his solutions for past exams he just puts 273 instead of 273.15, so can someone please ask?
Tue Feb 06, 2018 11:29 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: constant pressure and constant volume
Replies: 3
Views: 166

### Re: constant pressure and constant volume

It depends what the question is going to be asking, but if it asks for an ideal gas the CV is 3/2R and the CP is 5/2R, or at least that's what my TA told me.
Tue Feb 06, 2018 11:24 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Tendency of processes
Replies: 2
Views: 167

### Re: Tendency of processes

When the Gibbs Free Energy of the reaction is less than 0, that means the forward reaction will be favorable, therefore making it spontaneous.
Mon Feb 05, 2018 1:25 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Net Increases in Amount of Gas
Replies: 3
Views: 212

### Re: Net Increases in Amount of Gas

I don't think Dr. Lavelle will ask us any questions where it becomes that difficult, but there is a question in the homework where there are equal moles of gas on both sides of the reaction, and you'd assume that the entropy decreases, but when you use the Gib's free energy values and calculate it, ...
Mon Feb 05, 2018 1:22 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G equal Zero [ENDORSED]
Replies: 4
Views: 266

### Re: Delta G equal Zero[ENDORSED]

Do you mean spontaneous? So for a reaction to be spontaneous the Delta G is negative while the Delta Stotal is positive for it to be spontaneous. I'm not sure what you mean by reversible, unless you are talking about if the forward reaction is favorable. Can you elaborate? Hope this helps.
Mon Feb 05, 2018 1:19 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: test question 7 [ENDORSED]
Replies: 6
Views: 398

### Re: test question 7[ENDORSED]

First you have to set both equations equal to one another, so you are trying to find the final temperature right? So you multiply the enthalpy of fusion of ice times the moles of ice plus the energy needed to cause the melted ice, now water to reach the final temperature. You take that equation and ...
Wed Jan 31, 2018 12:51 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Comparing 9.1 and 9.3
Replies: 3
Views: 221

### Re: Comparing 9.1 and 9.3

It will be negative because you switch the sign in this problem, therefore it makes sense to put it there.
Wed Jan 31, 2018 12:50 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.5
Replies: 5
Views: 253

### Re: 9.5

Since it is at 800K, the energy is leaving the system therefore that energy is negative, whereas the surroundings absorbs energy therefore it is positive, therefore it makes sense to put the negative there.
Thu Jan 25, 2018 9:04 pm
Forum: Administrative Questions and Class Announcements
Topic: Out of Topic
Replies: 3
Views: 292

### Out of Topic

This may not seem like a relevant question to ask here, but does anyone know when Dr. Lavelle's office hours are?
Thu Jan 25, 2018 12:07 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Monatomic Gas
Replies: 5
Views: 358

### Re: Monatomic Gas

R is the constant that we use in this case, which is 8.3145 J/K*mol
Thu Jan 25, 2018 12:05 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy of a gas
Replies: 2
Views: 214

### Re: Entropy of a gas

Since the volume decreases, there is less space in the container or wherever the gas is contained, therefore the gas has less possible states therefore the degeneracy for the gases decreases and that means that the entropy of the gas decreases.
Thu Jan 25, 2018 12:03 pm
Forum: Phase Changes & Related Calculations
Topic: 8.87
Replies: 2
Views: 135

### Re: 8.87

So you have to add all of the energy required to convert the ice to water, so you take the enthalpy of fusion for the ice and add it to the energy change associated with the ice changing to 0 degrees. Then once it is water, you take the amount of energy from 0-100 degrees and then add the heat of va...
Tue Jan 23, 2018 12:00 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW #41 vs #21
Replies: 3
Views: 230

### Re: HW #41 vs #21

It doesn't matter where you place the negative sign, because it will lead you to the same final answer. As long as you remember to put the negative somewhere during your calculation you should be fine. Just remember: qsystem+qsurroundings=0 Therefore when the system releases heat it is absorbed by t...
Sun Jan 21, 2018 3:35 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Intensive vs. Extensive
Replies: 3
Views: 400

### Re: Intensive vs. Extensive

In addition, things like Enthalpy, Internal Energy, Temperature, Volume, Density and Heat Capacity are all state functions, however heat capacity itself is an extensive property because it depends on the mass, therefore is something has more mass it will have a higher heat capacity.
Sun Jan 21, 2018 3:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework problem 8.59
Replies: 5
Views: 1098

### Re: Homework problem 8.59

Any gas at its most stable state is regarded as having an enthalpy of formation as equal to 0 because it becomes insignificant.
Sun Jan 21, 2018 3:14 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.25
Replies: 1
Views: 119

### Re: 8.25

The calorimeter is being calibrated, therefore when it is calibrated the specific heat capacity of the calorimeter is being redefined, therefore you need to find the heat capacity of the calorimeter, then it states that there is a neutralization reaction and all that does it cause the temperature to...
Sun Jan 21, 2018 3:08 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Assigning system/surroundings
Replies: 5
Views: 334

### Re: Assigning system/surroundings

The metal would be the system and the water would be the surroundings because in this case the water is absorbing energy from the metal as it is placed in it.
Sun Jan 21, 2018 3:03 pm
Forum: Calculating Work of Expansion
Topic: work done on and by the system
Replies: 12
Views: 707

### Re: work done on and by the system

WORK itself is NEGATIVE when the system itself performs work on the surroundings, therefore logically WORK will be POSITIVE when work is done on the system.
Tue Jan 16, 2018 4:10 pm
Forum: Phase Changes & Related Calculations
Topic: 8.15 b
Replies: 3
Views: 188

### Re: 8.15 b

In the chapter, it says an adibiatic system, it is an closed system, meaning that energy can be exchanged with the system in the form of work, meaning that q=0. Read the little section in the chapter where it discusses the adibiatic system near the beginning of the chapter, that should help in under...
Tue Jan 16, 2018 4:07 pm
Forum: Calculating Work of Expansion
Topic: Expansion/Contraction
Replies: 2
Views: 164

### Re: Expansion/Contraction

What the book means when the change in internal energy equals q which is the heat transferred to a system or released, when it says no expansion or contraction occurs in the form of work, therefore when there is no work happening through expansion or contraction, then the internal energy should equa...
Fri Jan 12, 2018 6:18 pm
Forum: Phase Changes & Related Calculations
Topic: Hess Law [ENDORSED]
Replies: 5
Views: 325

### Re: Hess Law[ENDORSED]

You would change the sign in that case because it is now the reverse of the reaction, therefore the enthalpy of the equation is now reversed you essentially multiply by -1
Fri Jan 12, 2018 6:14 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Problem 8.31
Replies: 3
Views: 179

### Re: Problem 8.31

So at constant pressure for a monoatomic molecule, you have to look at the Cpm and Cvm values on a chart that is located somewhere near the middle of the chapter. The Cpm in this case would be 5/2R and the Cvm would be 3/2R, I'm sure Lavelle will be going over this more in depth next week during lec...
Fri Jan 12, 2018 6:09 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity vs Specific Heat
Replies: 2
Views: 164

### Re: Heat Capacity vs Specific Heat

Yes for instance there is the heat capacity of a calorimeter or something that is storing the solution. Otherwise I'm not entirely sure.
Fri Jan 12, 2018 6:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Are there any periodic trends for enthalpy?
Replies: 4
Views: 207

### Re: Are there any periodic trends for enthalpy?

There are trends for bond enthalpies, in the sense that if there are generally more molecules, for instance NO vs NO3, NO3 will have a higher bond enthalpies to account for the additional oxygen molecules that are attached to the Nitrogen. Otherwise I don't think so.
Thu Jan 11, 2018 10:12 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Celsius the same as Kelvin? [ENDORSED]
Replies: 9
Views: 2543

### Re: Celsius the same as Kelvin?[ENDORSED]

Not necessarily, the change is basically the same so it doesn't matter which unit you use. Only the individual units need be specified in this case. Since the equation uses the change in Temperature, or delta T it is merely the difference.
Thu Jan 11, 2018 10:10 am
Forum: Phase Changes & Related Calculations
Topic: qp=deltaH
Replies: 8
Views: 526

### Re: qp=deltaH

qp is the heat released or absorbed at constant pressure, you would use this format in certain situations when looking at systems at constant pressure whereas the other equation where it is just q is the heat released or absorbed under certain conditions not necessarily at constant pressure. I recom...
Mon Jan 08, 2018 3:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: The First Law: Problem 8.3
Replies: 2
Views: 214

### The First Law: Problem 8.3

For problem 8.3, it asks if the work is positive or negative with respect to the air in the pump, the answer is that it is positive is that because the air is compressed? So if it said hypothetically that air was expanded then work would be negative with respect to the air right?
Thu Dec 07, 2017 2:15 pm
Forum: Conjugate Acids & Bases
Topic: HW 12.3
Replies: 3
Views: 338

### Re: HW 12.3

For instance if you have NO3- the conjugate acid would be HNO3, but if you have the weak base NH3 then you will have the conjugate acid ammonium which is NH4+. just remember for conjugate base minus one H and for the conjugate acid add one H.
Thu Dec 07, 2017 2:12 pm
Forum: Conjugate Acids & Bases
Topic: HW 12.33?
Replies: 1
Views: 166

### Re: HW 12.33?

Because it is being diluted from 5ml to 500ml so you have to do the equation backwards so that you can find the initial amount of moles that were used to create that initial molarity and then you can find the amount of grams that was originally used.
Thu Dec 07, 2017 2:07 pm
Forum: Bronsted Acids & Bases
Topic: Determining the Stronger Acid
Replies: 2
Views: 252

### Re: Determining the Stronger Acid

If the compound has the same amount of oxygen atoms, simply look at which atom is more electronegative. This is a much simpler approach because it is more stabilized with the electronegative atom. For example, if you have HCl and HI, the HydroIodic Acid is much stronger because it was weaker forces ...
Thu Nov 30, 2017 12:12 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Part 1B Post-Module Assessment #26
Replies: 2
Views: 168

### Re: Part 1B Post-Module Assessment #26

Solvents are not included in the reaction quotient or equilibrium constant, because there is way for you to measure the concentration of a pure solid displaced in some liquid. Just know that liquids and solids are not used or even considered when doing ice boxes or calculating the equilibrium quotie...
Thu Nov 30, 2017 12:10 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Quotient
Replies: 3
Views: 384

### Re: Quotient

Q itself, is the reaction quotient for the reaction given with whatever initial numbers that you are given. Whereas K is the equilibrium quotient, which is the ratio of the concentration/partial pressure of the products and reactants.
Thu Nov 30, 2017 12:08 am
Forum: Hybridization
Topic: 4.95
Replies: 3
Views: 286

### Re: 4.95

It just means where-ever the arrow is pointing, that atom has an hybridization of sp2.
Thu Nov 30, 2017 12:08 am
Forum: Naming
Topic: Self Test 17.3B (a)
Replies: 1
Views: 190

### Re: Self Test 17.3B (a)

The bromine itself has a -1 charge, and the sulfate has a -2 charge, therefore combined it has a -3 charge. It is meant to be +3 because subtract 1 and you get 2 which cancels out with the negative 2 from the sulfate ion. The answers in the back sometimes have small errors, but yes, you are correct.
Thu Nov 30, 2017 12:04 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Pi and sigma bonds [ENDORSED]
Replies: 7
Views: 441

### Re: Pi and sigma bonds[ENDORSED]

Sigma bonds can rotate, however Pi bonds cannot rotate because there are two distinct sigma bonds there, therefore forming a pi bond. If you attempted to rotate the compound, then the Pi bond would therefore break. Sigma Bonds are formed when the electron density is at the center of the bond, and it...
Thu Nov 30, 2017 12:02 am
Forum: Naming
Topic: aqua = (OH2) or (H20)
Replies: 2
Views: 280

### Re: aqua = (OH2) or (H20)

This is because when you write out the chemical name, the Oxygen in water is supposed to be bonding to the central atom, and it is therefore meant to be written as (OH2), however since the ammonium is placed first when naming the compound, the ammonium attaches to the central atomic, but in most cas...
Wed Nov 29, 2017 11:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Square Planar
Replies: 3
Views: 253

### Re: Square Planar

The electron arrangement is AX4E2, therefore it forms a square shape because the dipole moments are all cancelled out, therefore it form a 90 degree angle with the adjacent atoms and also forms a linear 180 degree angle with the central atom and the two adjacent atoms.
Tue Nov 28, 2017 5:21 pm
Forum: Biological Examples
Topic: Other Biological Examples
Replies: 5
Views: 558

### Re: Other Biological Examples

I also believe that Cobalt gives Vitamin B12 its red color, Also iron for instance with myoglobin and hemoglobin helps transport oxygen throughout the blood stream.
Tue Nov 28, 2017 1:25 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q [ENDORSED]
Replies: 7
Views: 682

### Re: Q[ENDORSED]

Q is the ratio of the products and the reactants with the initial concentrations or whatever data the problem gives you, whereas K is the equilibrium concentration for the reaction, which does not change with changes to pressure and concentration, however it does change with change to temperature.
Tue Nov 28, 2017 1:23 pm
Forum: Biological Examples
Topic: Fe and proteins
Replies: 6
Views: 780

### Re: Fe and proteins

Also, Fe is the central metal in the heme complex, but it helps the complex carry oxygen throughout the bloodstream.
Sat Nov 25, 2017 8:30 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Temperature and K [ENDORSED]
Replies: 3
Views: 269

### Temperature and K[ENDORSED]

How is the equilibrium composition affected by temperature?
Sat Nov 18, 2017 1:21 pm
Forum: Dipole Moments
Topic: How do Dipole moments determine polarity?
Replies: 4
Views: 395

### Re: How do Dipole moments determine polarity?

If they don't cancel, then it is polar moment, but if the dipoles do cancel then it is nonpolar, but how do you determine dipole moments?
Thu Nov 16, 2017 7:18 pm
Forum: Hybridization
Topic: Quick Hybridization Question
Replies: 1
Views: 145

### Quick Hybridization Question

Let's say for example you have an arrangement of atoms that is Ax3E2, which means that it is T-Shaped, therefore the electron arrangement is Trigonal Bypyramidal and the hybridzation is sp3d right?
Thu Nov 16, 2017 7:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Chapter 4 Question 17 Part D
Replies: 1
Views: 176

### Chapter 4 Question 17 Part D

hy is a hydronium ion supposed to be linear even if it has two lone pairs on the central atom? Why is it also less than 109.5 degrees? Can someone please explain to me it is linear?
Sun Nov 12, 2017 12:16 am
Forum: Coordinate Covalent Bonds
Topic: Ionic and Covalent Bonds
Replies: 2
Views: 362

### Ionic and Covalent Bonds

How would I tell the difference between a covalent and an ionic bond?
Wed Nov 08, 2017 3:56 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: d orbital or s orbital first?
Replies: 5
Views: 388

### Re: d orbital or s orbital first?

Until you reach element 19 or 20, the S will generally come before d because it is in lower energy, once the d orbital starts to get filled up, it loses its energy and is less energy than the 4s orbital, for example, scandium would have the configuration of 3d13s2 if it was coming from Argon. Make s...
Wed Nov 08, 2017 3:53 pm
Forum: Ionic & Covalent Bonds
Topic: How to easily tell between Ionic and Covalent bonds?
Replies: 8
Views: 631

### Re: How to easily tell between Ionic and Covalent bonds?

Non-metals bonding with non-metals tend for form covalent bonds because the electrons themselves are being shared between both atoms. An ionic bond occurs between a metal and a nonmetal where the electrons are transferred from one electron to the other.
Sun Oct 29, 2017 7:54 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy [ENDORSED]
Replies: 5
Views: 397

### Re: Ionization Energy[ENDORSED]

As you go across a period the ionization energy is going to increase the the nuclear charge is increasing also the z effective charge increases making it harder for the electrons to be pulled from certain elements. However, the ionization energy decreases going down a period because there are more s...
Thu Oct 19, 2017 10:23 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes/ Subshells
Replies: 1
Views: 750

### Nodal Planes/ Subshells

Can someone please explain what n, l, and ml mean? Also can someone please explain what a nodal plane is?
Thu Oct 19, 2017 10:20 pm
Forum: Properties of Light
Topic: Color of visible light
Replies: 11
Views: 748

### Re: Color of visible light

All you need to know is that visible light is from the spectrum 400-700nm, you won't have to memorize which wavelength relates to which color in the visible spectrum.
Thu Oct 19, 2017 10:10 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation
Replies: 7
Views: 515

### Re: Rydberg Equation

N1 is supposed to be the initial energy level it starts at, for instance if we say if it is the Lyman Series, then N1 starts at energy level 1 so then it absorbs energy and it excited to a higher energy level. You can use that equation to find the frequency required to make each jump, however Lavell...
Wed Oct 11, 2017 8:59 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Online Assessment Q34
Replies: 1
Views: 191

### Re: Photoelectric Effect Online Assessment Q34

This problem is discussing the photoelectric effect meaning that the energy per photon of energy reaches the minimum energy requirement to free and electron from the piece of metal. Once it reaches this minimum energy requirement or the threshold energy level, if the energy per photon exceeds the th...
Wed Oct 11, 2017 8:50 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post Assessment Question 41
Replies: 2
Views: 354

### Atomic Spectra Post Assessment Question 41

I'm not sure how to solve this problem and where to start to begin eliminating answer choices? Can someone help me with this problem? 41. For the hydrogen atom which statement is true? A. The transition from n = 5 to n = 3 involves greater energy than one from n = 4 to n = 2. B. The transition from ...
Fri Oct 06, 2017 2:18 am
Forum: Balancing Chemical Reactions
Topic: M9 Part A
Replies: 2
Views: 237

### Re: M9 Part A

To find the net ionic, you have to first understand what product is going to become a solid and which reactants are soluble meaning they became aqueous, so, the precipitate which is blue copper hydroxide is actually a solid and the reactants are soluble. The copper nitrate is soluble and so is the s...
Thu Oct 05, 2017 1:29 pm
Forum: Limiting Reactant Calculations
Topic: Question M.1 [ENDORSED]
Replies: 5
Views: 1229

### Re: Question M.1[ENDORSED]

Since you already know that hypochlorite is in excess, you assume that ammonia is the limiting reactant, therefore convert the 35g of ammonia to grams of hydrazine and then you will find the theoretical yield. Once you find the theoretical yield, you take the actual yield which is 25.2 grams produce...