## Search found 65 matches

Fri Mar 15, 2019 10:34 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 4
Views: 266

### Re: Catalysts

Definitely not for the overall rate law. As for the rate law for an elementary step, that's a really good question. My guess is no because I think that the only things in the rate law are supposed to be the reactants in the overall equation.
Fri Mar 15, 2019 10:32 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: K Constant
Replies: 1
Views: 97

### Re: K Constant

K tells you the ratio of products to reactants. When more products are being formed, the forward rate constant is going to greater than the reverse constant. This means that k/k' is going to be greater than one, which aligns with what we would expect from K since there are more products than reactan...
Fri Mar 15, 2019 11:17 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Solution Manual Q
Replies: 1
Views: 92

### Solution Manual Q

I noticed that for a lot of the Nernst equation problems, the solution manual combines partial pressures and concentrations in the expression for Q. For example, in problem 6N.3 Q is written as (.075M)^2(1 atm)/(1.0M)^2(1 atm) Does this mean that in general we don't have to convert the partial press...
Sat Mar 09, 2019 12:37 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: differential rate law equation
Replies: 3
Views: 179

### Re: differential rate law equation

I'm also confused about this. Is there ever a case where we have to use the differential rate law or will we always be able to use the integrated form?
Sat Mar 09, 2019 12:36 pm
Forum: Zero Order Reactions
Topic: Half Life and k
Replies: 11
Views: 700

### Re: Half Life and k

the equation of half life is always t(1/2)=ln2/kr.

The proof for this is given in 7B.2 in the 7th edition textbook.
Sat Mar 09, 2019 12:33 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: zero order
Replies: 2
Views: 120

### Re: zero order

I think it might be zero because it doesn't depend on the concentration of any reactants.
Thu Feb 28, 2019 10:29 pm
Forum: Balancing Redox Reactions
Topic: Problem K3 D
Replies: 2
Views: 134

### Re: Problem K3 D

I was confused about this too. Is it possible that there's a typo in the book? I feel like it should be this:
cl2---> HCLO+2Cl-

It seems weird to have cl2 on both sides of the equation.
Thu Feb 28, 2019 10:23 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Test 2
Replies: 4
Views: 223

### Re: Test 2

For the seventh edition you should look at the following chapters:
Gibbs Free Energy: 4J, 5G, 5J
Electrochem: 6K, 6L, 6M
Thu Feb 28, 2019 10:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Organization of cell diagrams
Replies: 9
Views: 290

### Re: Organization of cell diagrams

What do you do if there's a liquid? I think someone mentioned that Hg(l) is some exception, is that true?
Thu Feb 21, 2019 7:07 pm
Forum: Van't Hoff Equation
Topic: Practice Problems
Replies: 3
Views: 234

### Practice Problems

Did anyone find any practice problems specifically related to Van't Hoff's equation? Is there every a case where you have to use this relationship instead of just calculated the different G values at each temperature and dividing those by RT?
Thu Feb 21, 2019 7:04 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free Energy and Pressure
Replies: 1
Views: 113

### Free Energy and Pressure

Why does the free energy depend on pressure?
Thu Feb 21, 2019 7:03 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free Energy and Work Relationship
Replies: 2
Views: 114

### Free Energy and Work Relationship

What's the relationship between free energy and work?
Wed Feb 13, 2019 9:07 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Replies: 5
Views: 283

Yes. You first assume constant temperature and calculate the change in entropy due to change in volume. Next, assume constant volume and calculate the change in entropy due the change in temperature. Just add these together to find the total change in entropy. (You could also do this the other way a...
Wed Feb 13, 2019 9:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy and qp
Replies: 3
Views: 230

### Re: Enthalpy and qp

Enthalpy is defined as the heat transferred or gained under constant pressure. Therefore, it must be equal to qp.
Tue Feb 12, 2019 3:07 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Reactions
Replies: 8
Views: 635

### Reversible Reactions

Are reversible reactions always isothermal? Can we assume that delta U = 0 for any reversible or isothermal reaction?
Thu Feb 07, 2019 12:20 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4C.3
Replies: 1
Views: 128

### 4C.3

This question states "Calculate the final temperature and the change in enthalpy when 1.15 kJ of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (a) at constant pressure; (b) at constant volume. Treat the gas as ideal." I understand how to calculate the final tempera...
Wed Feb 06, 2019 4:03 pm
Forum: Phase Changes & Related Calculations
Topic: What exactly is 3/2RT and when do we use it?
Replies: 4
Views: 1216

### Re: What exactly is 3/2RT and when do we use it?

Internal energy is energy stored as kinetic energy and potential energy that can move in different ways, including translational energy, rotational energy, and vibrational energy. The translational energy is equivalent to 3/2RT and the rotational energy of a nonlinear molecule is also 3/2RT. Both of...
Wed Feb 06, 2019 3:50 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 6th edition 9.3
Replies: 2
Views: 132

### Re: 6th edition 9.3

Convert celsius to kelvin and use the equation deltaS=q/T.

Part a: 65J/298K = .22 J/K
Part b: 65J/373K = .17 J/K

Part b is smaller because the temperature is greater, resulting in a smaller change in entropy (as you can observe from the equation).
Wed Feb 06, 2019 3:34 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 3R/2 vs 5R/2
Replies: 1
Views: 105

### Re: 3R/2 vs 5R/2

When the volume is constant, you should use 3R/2. When the pressure is constant, you should use 5R/2.
Wed Jan 30, 2019 10:28 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW problem 4A.7
Replies: 1
Views: 141

### Re: HW problem 4A.7

Yes exactly. The total heat will be the heat required to raise the copper temperature to 100 degrees Celsius (q(copper)) + the heat required to raise the water to 100 degrees Celsius (q(water)), using the formula you listed for both. For the second part you will just do q(water)/total heat *100% to ...
Wed Jan 30, 2019 10:23 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Studying gases
Replies: 2
Views: 162

### Re: Studying gases

Gases will probably be in a lot of the examples where work is being done because the work done by liquid and solids in a system is generally insignificant. However, they could definitely ask questions about solids and liquids in a closed system where the energy of the system is changed by heating/co...
Wed Jan 30, 2019 10:19 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Forms of U Equations
Replies: 3
Views: 182

### Re: Forms of U Equations

It depends on the what's happening in the problem. U=w+q is always true and can always be used. It just means that the change in the energy of the system is going to depend on the work done by or on the system and the heat released/absorbed. However, in some problems there is no work being done. If ...
Thu Jan 24, 2019 9:27 am
Forum: Ideal Gases
Topic: Ice Table with quadratic equation on bottom
Replies: 3
Views: 123

### Re: Ice Table with quadratic equation on bottom

I believe that's possible. Could you list the problem you are working on?
Thu Jan 24, 2019 9:26 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: help on last module!
Replies: 2
Views: 154

### Re: help on last module!

This has to be a mistake with the question. Adding water would not change the equilibrium concentration.
Thu Jan 24, 2019 9:23 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test 1
Replies: 9
Views: 373

### Re: Test 1

Pretty much all of the formulas and conversions are given. You should know the following relationships:

pOH + pH = pKw
[OH][H30] = Kw
(Ka)(Kb) = Kw
pKa + pKb = pKw
PV = nRT

If you know these then you should be good.
Thu Jan 17, 2019 2:41 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Effect of Pressure [ENDORSED]
Replies: 2
Views: 78

### Re: Effect of Pressure[ENDORSED]

It's important to keep in mind that when counting the number of moles on each side, you are only counting the moles of gas. For example, if the reactant side has 2 moles of gas and 1 mole of a solid while the product side has 3 moles of gas, then the reaction will shift left because the reactants ha...
Thu Jan 17, 2019 2:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Sixth Edition Question 11.87
Replies: 2
Views: 128

### Re: Sixth Edition Question 11.87

If you think about it, gases such as oxygen and nitrogen typically exist as 02 and N2 because that is there lowest energy state. Therefore, in order to break this low energy state, energy has to be put into this system, therefore making it endothermic.
Thu Jan 17, 2019 2:29 pm
Forum: Ideal Gases
Topic: #47 on Chemical Equilibrium 1B Video Module Assessment
Replies: 3
Views: 156

### Re: #47 on Chemical Equilibrium 1B Video Module Assessment

Convert each concentration to a partial pressure using PV=nRT. You are given n/V, R and T so you just need to solve for P.
Sat Jan 12, 2019 5:43 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert Gases
Replies: 2
Views: 66

### Re: Inert Gases

Going off of what what previously said, the inert gas will change the pressure of the system. However, since this pressure isn't as a result of compression (which would decrease the volume and change the concentrations), it won't affect the calculations. Because of this, adding an inert gas will not...
Sat Jan 12, 2019 5:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Effect of Partial Pressure on Concentration
Replies: 2
Views: 91

### Re: Effect of Partial Pressure on Concentration

The partial pressure is different than the overall pressure. Basically, treat partial pressure kind of like concentration. For gases, often you are given the partial pressure instead of the concentration but as far as our calculations go you can treat them almost the same. The overall pressure is wh...
Sat Jan 12, 2019 5:31 pm
Forum: Ideal Gases
Topic: Homework 6th edition Question 11.7
Replies: 1
Views: 62

### Re: Homework 6th edition Question 11.7

I believe that the question is asking which flask shows when the reaction reached equilibrium. So even though the third flask and the fourth flask are both at equilibrium, the third flask better shows when the reaction first reached equilibrium. You can tell that it's at equilibrium at this point be...
Mon Dec 03, 2018 8:57 pm
Forum: Amphoteric Compounds
Topic: Definition
Replies: 6
Views: 276

### Re: Definition

Amphoteric means that a compound can behave as both an acid and a base. In general any of the metalloid oxides can be amphoteric. However, the most important example that you need to know is water... Water as a base: HCl(aq) + H2O(l) --> Cl-(aq) + H3O (aq) Water behaves as a base in this case becaus...
Mon Dec 03, 2018 8:48 pm
Forum: Air Pollution & Acid Rain
Topic: Acid Rain Equations
Replies: 1
Views: 315

### Acid Rain Equations

What were the other equations for the cause of acid rain besides the one with carbon dioxide (CO2 + H2O --> H2CO3)? What are some possible options to reduce acid rain?
Mon Dec 03, 2018 7:41 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Help With 6C.17
Replies: 1
Views: 102

### Help With 6C.17

I'm having trouble with this question:
"Which is the stronger base, the hypobromite ion, BrO-, or morphine, C17H19O3N? Justify your answer."

From the solutions manual I saw that they used the pKb values of the base, but how are you supposed to know the pKb value?
Wed Nov 28, 2018 9:15 am
Forum: Hybridization
Topic: Ethene Hybrid Orbitals
Replies: 4
Views: 296

### Re: Ethene Hybrid Orbitals

There is a total of 3 p-orbitals. In an sp hybridized orbital, one of those p orbitals is combined with the s orbital while the other two remain true p-orbitals. In an sp^2 hybridization, two p orbitals are hybridized with the s orbital, leaving one p-orbital unhybridized. In sp^3, all p orbitals ar...
Wed Nov 28, 2018 9:07 am
Forum: Hybridization
Topic: 2F.1
Replies: 2
Views: 128

### Re: 2F.1

Hybrid orbitals will point in the directions of the different VSEPR models we have learned so just figure out which VSEPR model each hybrid orbital corresponds to.
Mon Nov 26, 2018 6:11 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: Test 3
Replies: 2
Views: 151

### Test 3

Are the intermolecular forces part of 2D? Should we expect to see this on the test?
Fri Nov 23, 2018 12:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sixth Edition. Question 4.109
Replies: 4
Views: 279

### Re: Sixth Edition. Question 4.109

That is correct, since there are only two single bonds with oxygen you can assume that there are two lone pairs that are not shown to finish the octet around oxygen. Therefore, the shape must be bent with an angle of 109 degrees.
Fri Nov 23, 2018 12:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 7th Edition Question 2E. 29
Replies: 2
Views: 50

### Re: 7th Edition Question 2E. 29

In the second example, the dipole moments are pointed away from each other so some of that pull will be cancelled if the vectors are added together. However, if the two dipole vectors are added in the first example, they are pointed in almost the same direction so the magnitude will be larger.
Fri Nov 23, 2018 12:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: I3- ion shape
Replies: 2
Views: 61

### Re: I3- ion shape

It's easier to understand why it's linear if you imagine a bipyramidal structure. Since there are three lone pairs in the I3- ion, imagine that the three central atoms of the bipyramidal structure are removed, leaving only the top, middle, and bottom atoms in a linear formation.
Sun Nov 18, 2018 3:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angle
Replies: 4
Views: 221

### Re: bond angle

We haven't been given a way to actually calculate the bond angles. However, it's easier to remember the angles if you remember the bond angles associated with each number of electron densities. For example, when there are two areas of electron density the angle will always be 180 degrees, when there...
Sun Nov 18, 2018 3:19 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: polarizing power of a cation
Replies: 3
Views: 150

### Re: polarizing power of a cation

Polarizing power is the power of a cation to distort the shape of an anion by pulling its electrons over. In general, the smaller the ion, the more polarizing power it will have. This means that ions that are towards the top left side of the periodic table and with a greater charge will have a great...
Sun Nov 18, 2018 3:12 pm
Forum: Bond Lengths & Energies
Topic: Dissociation Energy
Replies: 4
Views: 327

### Dissociation Energy

On the outline it says we should know the following: • Explain how covalent bond dissociation energy is related to covalent bond multiplicity, atomic radius, and the presence of unpaired electrons. I understand that covalent bond dissociation is the energy required to break the bond. From my underst...
Tue Nov 13, 2018 5:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining VSEPR bond angles
Replies: 5
Views: 832

### Re: Determining VSEPR bond angles

Each different geometric shape has implied bond angles. For instance, trigonal planar will always be 120 degrees, linear will be 180 degrees, tetrahedral will 109.5 degrees and so on. You won't need to calculate any bond angles, you will just have to figure out the shape and then use the bond angles...
Tue Nov 13, 2018 5:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: The A in the VSEPR Formula [ENDORSED]
Replies: 4
Views: 98

### Re: The A in the VSEPR Formula[ENDORSED]

The purpose of A is just to represent the central atom in the particular molecule that you are looking at.
Tue Nov 13, 2018 5:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles [ENDORSED]
Replies: 2
Views: 136

### Re: Bond Angles[ENDORSED]

If you look at the diagram for an octahedral shape you can see that there are three atoms in the vertical direction that are in a straight line (or 180 degree angle). There's also 4 atoms located in the middle around this vertical line. These 4 atoms will repel each other and each form 90 degree ang...
Tue Nov 06, 2018 12:07 pm
Forum: Electronegativity
Topic: Electronegativity calculation
Replies: 4
Views: 231

### Re: Electronegativity calculation

All we need to know is the trend of electronegativity. You should generally be able to tell which element is more electronegative when comparing between elements. However, you won't need to actually calculate the exact values. If there's a situation where the exact values are important a chart will ...
Tue Nov 06, 2018 11:57 am
Forum: Bond Lengths & Energies
Topic: Resonance Structures
Replies: 4
Views: 184

### Re: Resonance Structures

To expand on that, if there is only one resonance structure, the bond lengths will be exactly the length of a single bond or a double bond, depending on what kind of bond it is. However, if there are multiple resonance structures, the bond length will be somewhere in between the length of a single b...
Tue Nov 06, 2018 11:54 am
Forum: Octet Exceptions
Topic: Octet Exceptions
Replies: 4
Views: 151

### Re: Octet Exceptions

The only elements that the octet always applies to is B, C, N, O, F. The max number of electrons they can have is 8 because there is no 2d orbital, meaning once they fill up the 2s and 2p orbitals there's no room left for any additional bonds. Once you reach period 3, the 3d orbital can be utilized ...
Sat Nov 03, 2018 9:02 pm
Forum: Administrative Questions and Class Announcements
Topic: What the Midterm Will Cover
Replies: 5
Views: 271

### What the Midterm Will Cover

On the Midterm information sheet posted on the website it says that the midterm will cover up to 2C in the 7th edition and 3.11 in the 6th edition. However, in class on Friday and in some of the review sessions we went into the properties of bonds (which is 2D in the 7th edition). Is it possible tha...
Tue Oct 30, 2018 10:43 pm
Forum: Lewis Structures
Topic: Exception to Octet Rule [ENDORSED]
Replies: 3
Views: 147

### Exception to Octet Rule[ENDORSED]

How do you know when an element can have more than eight electrons? Do we just need to memorize the exceptions or is there some way of figuring it out?
Tue Oct 30, 2018 10:40 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 14
Views: 797

### Re: Drawing Lewis Structures

No resonance won't affect the shape in the Lewis structures at all. To show resonance, you will need to draw multiple diagrams to show the different possibilities.
Tue Oct 30, 2018 10:36 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 2
Views: 157

### Re: Electron Affinity

I think he said that with electron affinity there's less of a clear trend as with ionization energy and atomic radius. In general the elements in the upper right side will have the highest electron affinity, but that doesn't guarantee that elements right next to each other or above/below each other ...
Wed Oct 24, 2018 9:10 am
Forum: Properties of Electrons
Topic: colombic potential
Replies: 2
Views: 250

### Re: colombic potential

This will not be on the test. He wanted us to understand the factors that affect electrons in multi-electron atoms, but you won't be asked to solve any equations like this.
Wed Oct 24, 2018 9:08 am
Forum: Properties of Light
Topic: Visible Light Spectrum... ?
Replies: 6
Views: 228

### Re: Visible Light Spectrum... ?

Yes it would be a good idea to memorize the visible light and UV wavelengths, but don't worry too much about memorizing the wavelengths of radio waves, gamma rays, etc because it most likely won't be on the test
Wed Oct 24, 2018 9:04 am
Forum: Properties of Light
Topic: conceptual questions on the test 2?
Replies: 3
Views: 216

### Re: conceptual questions on the test 2?

There most likely will be conceptual questions. You should be able to explain the photoelectric affect, and the atomic spectra, and other things he has put emphasis on
Thu Oct 18, 2018 8:41 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 1D 15
Replies: 2
Views: 63

### Re: 1D 15

Yes, n stands for the principal quantum number, l stands for the orbital angular momentum, and m1 is the magnetic quantum number. n indicates the energy level, l indicates the rate at which the electron circulates around the nucleus, and m1 distinguishes the individual orbitals within a subshell.
Thu Oct 18, 2018 8:37 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2s Orbital
Replies: 2
Views: 179

### Re: 2s Orbital

I believe that the average distance of electrons from the nucleus in the 2s orbital is greater than the average distance of electrons in the 1s orbital. Both orbitals are drawn in a sphere shape showing the potential locations of the electrons, so the 2s sphere will be larger than the 1s sphere.
Thu Oct 18, 2018 8:34 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Problem ID.11
Replies: 3
Views: 140

### Problem ID.11

How do you figure out how many orbitals are subshells with l equal to a specific value?
Mon Oct 08, 2018 3:52 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: How to understand the questions correctly
Replies: 3
Views: 209

### Re: How to understand the questions correctly

In general I think those statements are true. Most of the questions should clearly state what form they want the answer with, and I'm sure it will be very clear on the test.
Mon Oct 08, 2018 3:47 pm
Forum: Balancing Chemical Reactions
Topic: States of Matter
Replies: 11
Views: 505

### Re: States of Matter

With what we are doing currently, the states of matter won't affect any calculations. My TA said that we should include the states whenever possible, and later on they will become more relevant to us.
Mon Oct 08, 2018 3:44 pm
Forum: Limiting Reactant Calculations
Topic: Reactants and Reagents
Replies: 4
Views: 230

### Re: Reactants and Reagents

Reagent refers to an actual physical chemical, while reactant refers to the word or symbol in the equation. If you were doing a physical experiment with real materials, you could refer to those materials as reagents. However, if you are talking about the reaction, you should refer to them as reactan...
Wed Oct 03, 2018 4:38 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Calculating the amount of atoms in a sample
Replies: 2
Views: 105

### Re: Calculating the amount of atoms in a sample

You will start by converting the mass into the number of moles by dividing by the molecular mass of the compound. To convert to formula units from moles, just multiply by Avogadro's constant.
Wed Oct 03, 2018 4:27 pm
Forum: SI Units, Unit Conversions
Topic: Week 1 Homework Assignment [ENDORSED]
Replies: 16
Views: 753

### Re: Week 1 Homework Assignment[ENDORSED]

Does anyone know how the 7 questions will be graded? Should I be showing every single step and make sure my work is super clear, or is it more based on completion?
Wed Oct 03, 2018 4:19 pm
Forum: Limiting Reactant Calculations
Topic: Finding theoretical yield
Replies: 6
Views: 406

### Re: Finding theoretical yield

The molar ratio between the two reactants is essential for determining the limiting reactant. However, once you find the limiting reactant you do not need to use the molar ratio between the reactants to determine the theoretical yield. You will be using the molar ratio between the limiting reactant ...