## Search found 71 matches

Sat Mar 16, 2019 2:25 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Vant Hoff equation on formula sheet
Replies: 6
Views: 644

### Vant Hoff equation on formula sheet

Hi! Will the Vant Hoff equation be on the formula sheet? It was for test 2, but is not on the "constants and equations" sheet from Dr. Lavelle's website.
Sat Mar 16, 2019 1:37 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Finding the Largest Standard Cell Potential
Replies: 1
Views: 93

### Re: Finding the Largest Standard Cell Potential

The species with the most positive reduction potential will be reduced. The species with the most negative reduction potential will be oxidized.
Sat Mar 16, 2019 1:35 pm
Forum: Balancing Redox Reactions
Topic: How to tell if its in acidic or basic
Replies: 6
Views: 206

### Re: How to tell if its in acidic or basic

They'll tell us. If the balanced redox reaction has H+ in it, it's acidic. If it has OH- in it, it's basic.
Wed Mar 13, 2019 11:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibruim Assessment
Replies: 5
Views: 256

### Re: Equilibruim Assessment

You should try using an ICE chart using the initial concentrations given as well as the concentration of NH3 at equilibrium. Hope this helps!
Wed Mar 13, 2019 11:55 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: cell diagrams
Replies: 6
Views: 287

### Re: cell diagrams

You usually won't need to include liquids (because H2O is the most common liquid in our equations, and because aqueous implies in solution, including H2O would be redundant), but if you did, it would be solid|liquid|aqueous||aqueous|liquid|solid.
Wed Mar 13, 2019 11:52 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Replies: 2
Views: 326

Adiabatic systems have constant temperature. Isochoric systems have constant volume.
Wed Mar 13, 2019 11:50 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: K = k/k'
Replies: 3
Views: 145

### Re: K = k/k'

Yes, k' is the reverse reaction.
Wed Mar 13, 2019 11:48 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Bomb calorimeter
Replies: 6
Views: 478

### Re: Bomb calorimeter

A bomb calorimeter is a closed system, meaning that matter cannot be exchanged with surroundings, but heat can. A coffee cup calorimeter is an isolated system, which means that no matter and no heat is exchanged with surroundings. Hope this helps!
Sun Mar 10, 2019 6:42 pm
Forum: General Rate Laws
Topic: Rate constant k
Replies: 5
Views: 257

### Re: Rate constant k

Every reaction has a unique k. Also, you should know how to find the units of k based on the fact that rate = M/s.
Sun Mar 10, 2019 6:41 pm
Forum: General Rate Laws
Topic: Rate Laws
Replies: 8
Views: 261

### Re: Rate Laws

They're given on the formula sheet, but they won't be labelled, so you should be familiar with them.
Sun Mar 10, 2019 6:39 pm
Forum: General Rate Laws
Topic: Reaction Order
Replies: 5
Views: 221

### Re: Reaction Order

We can determine if a reaction is first or second order using the equation rate = k[A]^n[B]^m. If n and m add up to one, it is a first order reaction. If n and m add to two, it is a second order reaction. Also, if a reaction is first order, then the graph of ln[A] vs t will have a slope of -k. If a ...
Sun Mar 03, 2019 6:52 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Q
Replies: 3
Views: 154

### Re: Q

I don't think you should mix partial pressures and concentrations -- Kc is when using concentrations and Kp is when using partial pressures. Hope this helps!
Sat Mar 02, 2019 1:41 pm
Forum: Balancing Redox Reactions
Topic: Creating a cell diagram
Replies: 8
Views: 325

### Re: Creating a cell diagram

Makenzie is right, don't include H2O but do include H+ and OH-, because their aqueous state implies that they are in water.
Wed Feb 27, 2019 9:08 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge vs Porous Disk
Replies: 1
Views: 77

### Re: Salt Bridge vs Porous Disk

They serve the same purpose, except salt bridges are represented by double bars and porous disks are represented by single bars in cell diagrams.
Wed Feb 27, 2019 1:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reducing power
Replies: 2
Views: 95

### Re: Reducing power

If something has a high reducing power then it will act as a reducing agent.
Wed Feb 27, 2019 1:06 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: n
Replies: 8
Views: 343

### Re: n

"n" is the number of electrons transferred in a balanced redox reaction. For example, in the reduction of Ce4+ to Ce3+ with I-, there are 2 electrons being transferred, so n = 2.
Wed Feb 27, 2019 1:01 pm
Forum: Balancing Redox Reactions
Topic: salt bridge vs porous disk
Replies: 4
Views: 493

### Re: salt bridge vs porous disk

They basically serve the same purpose except that that with the salt bridge, there are two beakers connected with a tube filled with gel that allows the salts to move, whereas with the porous disk, the salts can transport to either side of the disk because it's porous. Salt bridges are represented w...
Wed Feb 13, 2019 11:32 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Change in Internal Energy
Replies: 3
Views: 191

### Re: Change in Internal Energy

The change in internal energy is equal to zero when the system is isothermal.
Wed Feb 13, 2019 11:10 am
Forum: Calculating Work of Expansion
Topic: Work of the system
Replies: 3
Views: 185

### Re: Work of the system

You can assume that the work of the system is zero when the system is at constant pressure and is not changing volume.
Wed Feb 13, 2019 11:06 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy and Enthalpy
Replies: 3
Views: 129

### Re: Internal Energy and Enthalpy

The change in internal energy (delta U) is equal to q + w, and when the system is at constant pressure, then q = delta H, which is enthalpy.
Wed Feb 13, 2019 11:04 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: DeltaS total
Replies: 2
Views: 83

### Re: DeltaS total

Delta S total is equal to Ssys + Ssurr, and delta S equals zero when the system is undergoing reversible expansion or is at equilibrium.
Wed Feb 13, 2019 11:02 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: delta S
Replies: 7
Views: 347

### Re: delta S

Delta S of the system equals zero when there is no heat entering the system, because detla S = q(reversible)/T.
Tue Feb 12, 2019 8:23 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: When is delta S = 0?
Replies: 3
Views: 3152

### Re: When is delta S = 0?

Delta S equals zero when there is no heat entering the system, because delta S = q(reversible)/T. Hope this helps!
Wed Feb 06, 2019 10:24 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Irreversible/Reversible Processes
Replies: 3
Views: 149

### Re: Irreversible/Reversible Processes

Isothermal reversible reactions do more work than irreversible reactions, because isothermal reactions have to work against more external pressure than irreversible reactions. Dr. Lavelle gave the example of a boulder at the top of a hill; work has to be done for the boulder to go up the hill, while...
Wed Feb 06, 2019 10:20 am
Forum: Calculating Work of Expansion
Topic: Work
Replies: 5
Views: 211

### Re: Work

Yep! For example, if a system has constant pressure, we know that delta(V) = 0, so the work is zero.
Wed Feb 06, 2019 10:18 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: enthalpy unit
Replies: 3
Views: 158

### Re: enthalpy unit

Most of the problems we do require enthalpy in joules, because delta(H) = detla(U) + pV, where detla(U) is in joules and pV can easily be converted into joules with the constant 101.325 J/(atm*L). Also, delta(H) is just H[final] - H[initial], both of which are in joules. Hope this helps!
Wed Feb 06, 2019 10:14 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Constant Pressure Calorimeter
Replies: 5
Views: 507

### Re: Constant Pressure Calorimeter

Bomb calorimeters (which a lot of problems include) are considered isolated, because no matter can be added and external heat does not have an effect on the internal system. Hope this helps!
Mon Feb 04, 2019 10:08 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Thermos
Replies: 4
Views: 174

### Re: Thermos

A really good thermos that does not let any heat in or out is considered an isolated system, because neither matter nor energy can be inputted into the system. Hope this helps!
Mon Feb 04, 2019 10:06 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed Systems
Replies: 6
Views: 204

### Re: Closed Systems

Closed systems can exchange heat but not matter, while isolated systems can exchange neither matter nor heat. An example of a closed system is a water bottle, and an example of an isolated system is a bomb calorimeter. Hope this helps!
Sun Feb 03, 2019 11:19 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: qv vs qp
Replies: 9
Views: 443

### Re: qv vs qp

Qv is heat at constant volume, while Qp is heat at constant pressure. At constant volume, delta(U) = Qv, because no work is being done on the system. At constant pressure, delta(U) = delta(H) - p(delta(V)). Hope this helps!
Wed Jan 23, 2019 4:24 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Ka and pH
Replies: 6
Views: 218

### Re: Ka and pH

Hi! I don't think so, but it is helpful to remember that when pH is lower, Ka is smaller and when pOH is lower, Kb is smaller.
Wed Jan 23, 2019 4:23 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endothermic vs. Exothermic
Replies: 8
Views: 375

### Re: Endothermic vs. Exothermic

Hi! Another thing to think about is that exothermic reactions heat up their surrounding areas, while endothermic reactions cool down surrounding areas.
Wed Jan 23, 2019 4:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: State property
Replies: 3
Views: 137

### Re: State property

Some more examples of state properties are energy, pressure, volume, temperature, density, and heat capacity. An example of something that is not state properties is work done. Hope this helps!
Wed Jan 23, 2019 4:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs Kc
Replies: 3
Views: 142

### Re: K vs Kc

It shouldn't give you a different answer for K, but typically concentrations are used to find the K of solutions and partial pressures are used to find the K of gases. You can calculate partial pressure by using concentrations and the formula PV = nRT. Hope this helps!
Wed Jan 23, 2019 4:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Specific Notation
Replies: 5
Views: 294

### Re: Specific Notation

You should get the same K value regardless of which notation you use; however, partial pressure is usually used for gases and concentration is usually used for solutions. Hope this helps!
Wed Jan 23, 2019 4:14 pm
Forum: Ideal Gases
Topic: OH and H3O
Replies: 10
Views: 722

### Re: OH and H3O

Yes, OH- and H3O+ do indicate whether something is an acid or a base. This is because OH- is formed when bases are combined with water and H3O+ is formed when acids are combined with water. It might be helpful to draw out the lewis structures of these reactions so that you can visualize the proton d...
Wed Jan 23, 2019 4:11 pm
Forum: Phase Changes & Related Calculations
Topic: Endothermic or Exothermic
Replies: 20
Views: 924

### Re: Endothermic or Exothermic

Condensation is exothermic. For example, like Dr. Lavelle said in lecture, when steam condenses from vapor to liquid, it releases heat. This is why steam burns are worse than burns from liquid water.
Wed Jan 23, 2019 4:09 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pKa, Ka, and relative acid strength
Replies: 3
Views: 399

### Re: pKa, Ka, and relative acid strength

You're right! Because pKa is the -log of Ka, when Ka is larger and the acid is stronger, pKa is decreased.
Wed Jan 23, 2019 4:07 pm
Forum: Phase Changes & Related Calculations
Topic: Water turning into ice rapidly
Replies: 2
Views: 79

### Re: Water turning into ice rapidly

I think this might have to do with how water bonds in a certain pattern when it forms ice (hexagon shapes)
Thu Jan 17, 2019 3:07 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.9
Replies: 2
Views: 152

### Re: 6B.9

Hi! To find the concentration of OH- you need to take the -log[H30+] then take the difference between that and 14 to find pOH. Then raise 10^(-pOH) to find [OH-]. This gives you 1.50*10^-14. Hope this helps!
Sat Dec 08, 2018 1:38 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: oxidation state calculation
Replies: 1
Views: 119

### Re: oxidation state calculation

Hi! The coordination numbers of the TMs are 4, 2, 6, 6. The oxidation state is the charge of the TM, while the coordination number is the number of bonds that the TM has to ligands. Hope this helps!
Wed Dec 05, 2018 11:26 pm
Forum: Bronsted Acids & Bases
Topic: Water as an Acid or Base
Replies: 4
Views: 249

### Re: Water as an Acid or Base

Water is amphoteric, meaning that it can act as both an acid and a base. It's useful to look at the other reactant in order to determine whether water is acting as an acid or as a base. For example combining water and hydrochloric acid (HCl), water acts as a base by accepting protons. Hope this helps!
Wed Dec 05, 2018 11:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar or nonpolar
Replies: 4
Views: 204

### Re: Polar or nonpolar

Wed Dec 05, 2018 11:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape
Replies: 4
Views: 138

### Re: Molecular Shape

Hi! IF5 would not have trigonal pyramidal shape because that would mean it would be AX3E (three bonds, one lone pair).
Wed Nov 28, 2018 6:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Why is AX3E2 not trigonal planar?
Replies: 2
Views: 263

### Re: Why is AX3E2 not trigonal planar?

I think that the lone pairs are further away from everything if they are in the t-shaped position -- if you had a trigonal planar molecule with two lone pairs at axial positions then it would look kinda like trigonal bipyramidal, but because lone pairs repel more than bonds, it wouldn't work out to ...
Wed Nov 28, 2018 6:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Tetrahedral
Replies: 2
Views: 124

### Re: Tetrahedral

Yes, it does!
Thu Nov 22, 2018 11:35 am
Forum: Determining Molecular Shape (VSEPR)
Topic: I3- molecular shape
Replies: 2
Views: 166

### I3- molecular shape

Hi Chemistry Community! Is I3- bent or linear shape? It seems like it should be bent, because one side has 2 lone pairs, whereas the other only has one; however, it could be like tetrahedral. Thanks!
Thu Nov 22, 2018 11:20 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw vs Tetrahedral Bipyramidal
Replies: 2
Views: 231

### Seesaw vs Tetrahedral Bipyramidal

Hi Chemistry Community!

What's the difference between seesaw and tetrahedral bipyramidal molecular shape? Thanks!
Thu Nov 22, 2018 10:34 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent - Lone Pairs
Replies: 8
Views: 418

### Re: Bent - Lone Pairs

Yes, for example, NO2 and O3 both have one lone pair and have bent molecular shape.
Thu Nov 22, 2018 10:27 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Sixth Edition. Question 4.109
Replies: 4
Views: 266

### Re: Sixth Edition. Question 4.109

Hi Danya! You're right, it's because oxygen has two lone pairs, which means that the structure has tetrahedral shape and bond angles of 109.5 degrees.
Thu Nov 22, 2018 10:25 am
Forum: Hybridization
Topic: Octet Expansion and d-Orbitals
Replies: 8
Views: 297

### Re: Octet Expansion and d-Orbitals

Hi Danya! You're right about elements with n=3 or higher can have an expanded octet because they have access to the d-orbital. I'm pretty sure that Silicon can have an expanded octet. As for Aluminum, while it can have an expanded octet, it often has a sextet. For example, Aluminum has a sextet in A...
Wed Nov 14, 2018 11:13 pm
Forum: Electronegativity
Topic: Homework Question 2D.11
Replies: 1
Views: 66

### Homework Question 2D.11

Hi Chemistry Community! I was wondering why N3+ has a higher polarizability than O2-? I thought that the ionic radius decreases across a period. Thanks!
Sun Nov 11, 2018 5:34 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Electronegativity
Replies: 6
Views: 279

### Re: Electronegativity

Oxygen is the most electronegative. O, N, and F are the most electronegative elements, which is why they tend to participate in London forces.
Sun Nov 11, 2018 5:31 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: Dipole Moment
Replies: 2
Views: 148

### Re: Dipole Moment

Hi! Dipole moments occur when a molecule has partially negative and a partially positive end. For example, H2O molecules are polar and have dipole moments during which the positive H ends are attracted to the negative O ends of different particles.
Sun Nov 11, 2018 5:28 pm
Forum: Lewis Structures
Topic: Exceptions to Octet Rule
Replies: 5
Views: 325

### Re: Exceptions to Octet Rule

Hi! All elements above period 3 can have an expanded octet.
Sat Nov 03, 2018 10:14 pm
Forum: Trends in The Periodic Table
Topic: Second and First Ionization Energy
Replies: 2
Views: 144

### Second and First Ionization Energy

Hi Chemistry Community! Why is the second ionization energy larger than the first ionization energy? Thanks!
Sat Nov 03, 2018 9:46 pm
Forum: Trends in The Periodic Table
Topic: Cation and Anion Ionic Radius
Replies: 3
Views: 81

### Cation and Anion Ionic Radius

Hi Chemistry Community! Why are anions larger than their parent atoms? And why are cations smaller? Thanks!
Tue Oct 30, 2018 11:29 pm
Forum: Ionic & Covalent Bonds
Topic: Ground states (homework problem 2A.11)
Replies: 2
Views: 112

### Ground states (homework problem 2A.11)

Hi chemistry community, why is the metal (M) M^3+ with the ground state [Ar]3d^6 Co^3+? How did you get that answer? Thanks!
Tue Oct 30, 2018 11:26 pm
Forum: Ionic & Covalent Bonds
Topic: Grounds states with f orbitals (2A.5)
Replies: 1
Views: 71

### Grounds states with f orbitals (2A.5)

Hi chemistry community, I'm having some trouble understanding ground states. When is the f orbital part of an element's ground state (for example: 2A.5 part d) Why is the ground state of Ti^3+ is [Xe]4f^14 5d^10?) Is there a trick to know when f orbital is introduced? Thanks!
Sun Oct 28, 2018 10:30 pm
Forum: Ionic & Covalent Bonds
Topic: Difference Between Ionic and Covalent Bonds
Replies: 4
Views: 183

### Re: Difference Between Ionic and Covalent Bonds

Ionic bonds involve one atom losing an electron (cation) and another atom gaining one (anion), while covalent bonds are when two atoms share electrons to form molecules. Hope this helps!
Wed Oct 24, 2018 1:10 pm
Forum: Quantum Numbers and The H-Atom
Topic: Which electrons have most energy?
Replies: 3
Views: 301

### Which electrons have most energy?

Hi Chemistry Community! I thought that the electrons closest to the nucleus (with lowest n-value / at ground state) had the lowest (most negative) energy, but I just saw this in the textbook: "...electron-electron repulsions cause the energy of a 2p-orbital to be higher than that of a 2s-orbita...
Wed Oct 24, 2018 12:46 pm
Forum: Quantum Numbers and The H-Atom
Topic: Radial distribution function on Test 2
Replies: 1
Views: 81

### Radial distribution function on Test 2

Hi Chemistry Community! Will the radial distribution function (P) be on Test 2? Thanks!
Sun Oct 21, 2018 9:23 pm
Forum: Properties of Electrons
Topic: Wave Properties
Replies: 4
Views: 186

### Re: Wave Properties

Yes! They just might not be detectable to us, so they basically don't exist from what we can tell
Sun Oct 21, 2018 9:21 pm
Forum: Student Social/Study Group
Topic: Note Taking
Replies: 32
Views: 2624

### Re: Note Taking

I like taking notes by hand because that's how I remember things the best. To be honest though, it's a little annoying not being able to edit notes like on Google Docs and not being able to search things though.. so I guess it really depends on what is most important to you.
Sun Oct 21, 2018 9:20 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: I'm uncertain about the Uncertainty Principle
Replies: 2
Views: 148

### Re: I'm uncertain about the Uncertainty Principle

I think that it has to with the fact that no one really knows what a particle looks like -- there will always be some amount of uncertainty
Wed Oct 10, 2018 9:34 pm
Forum: SI Units, Unit Conversions
Topic: State of the molecules
Replies: 4
Views: 268

### Re: State of the molecules

I would write it just in case, but I don't think we're expected to know what the states would be unless they're given to us. Good luck!!
Wed Oct 10, 2018 9:31 pm
Forum: SI Units, Unit Conversions
Topic: Scientific Notation
Replies: 7
Views: 389

### Re: Scientific Notation

It would probably be helpful if you had something like 250 mL (2.50 * 10^2 vs 2.5 * 10^2).
Wed Oct 10, 2018 9:25 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical & Molecular Formulas
Replies: 11
Views: 971

### Re: Empirical & Molecular Formulas

Yes, they can! Just make sure you divide the given molar mass by the molar mass of the empirical formula to double check.
Thu Oct 04, 2018 4:31 pm
Forum: Significant Figures
Replies: 3
Views: 76

### Re: Avogadro's Constant Sig Fig?

I would re-do them just to be sure. You should be fine using 6.022 * 10^23.
Thu Oct 04, 2018 4:30 pm
Forum: Administrative Questions and Class Announcements
Topic: Where to find assignments
Replies: 5
Views: 218

### Where to find assignments

So I know that for this week we are turning in any seven of the "Fundamentals" problems in during Friday's lecture, but is there anywhere that the homework assignment (due dates, instructions) will be posted or will we always be choosing seven of the problems on the outline and turning the...
Thu Oct 04, 2018 4:26 pm
Forum: SI Units, Unit Conversions
Topic: Homework Questions [ENDORSED]
Replies: 14
Views: 592

### Re: Homework Questions[ENDORSED]

I did one question from each section just in case, but I'm pretty sure any 7 will be fine! I think that we will usually turn homework in during the discussions.