## Search found 60 matches

Mon Mar 11, 2019 11:00 pm
Forum: First Order Reactions
Topic: Units of Rate Constant
Replies: 5
Views: 250

### Re: Units of Rate Constant

I would match the units with whatever is given in the problem. This is what the solutions manual seems to do as well.
Mon Mar 11, 2019 10:57 pm
Forum: Second Order Reactions
Topic: Slope of k
Replies: 2
Views: 125

### Re: Slope of k

When you integrate 1/[A], you get a negative sign so the slope of k switches from negative to positive.
Mon Mar 11, 2019 10:51 pm
Forum: Second Order Reactions
Topic: half-life for second order
Replies: 3
Views: 139

### Re: half-life for second order

The half life equations are all on the equation sheet.
Thu Mar 07, 2019 3:52 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework for Week 9
Replies: 3
Views: 178

### Re: Homework for Week 9

I think kinetics since that is what we have been covering for the past week. Also since our final is coming up, practicing kinetics will probably be useful. Though I think questions on the Nernst equation would also be acceptable since it wasn't covered in Test 2.
Thu Mar 07, 2019 3:47 pm
Forum: First Order Reactions
Topic: First order graph
Replies: 7
Views: 297

### Re: First order graph

The x-intercept would tell you the time at which all of your reactant A runs out.
Thu Mar 07, 2019 3:46 pm
Forum: Van't Hoff Equation
Topic: test 2
Replies: 7
Views: 562

### Re: test 2

I found the Kw2 value using the Van't Hoff equation. I square rooted the Kw2 value to find the H3O+ concentration at the new "neutral" pH value. I used -log[H3O+] to find the pH value and compared it with the pH value given in the question. My new pH value ended up being 7.27 and 7.0 is le...
Tue Feb 26, 2019 7:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Moles of electrons?
Replies: 6
Views: 211

### Re: Moles of electrons?

I usually balance out the half reactions. If the redox rxn that is given is balanced, you only need to balance one of the half reactions to see how many moles of electrons you need.
Tue Feb 26, 2019 7:14 pm
Forum: Balancing Redox Reactions
Topic: Basic redox reactions
Replies: 3
Views: 159

### Re: Basic redox reactions

In basic redox reactions, you don't balance with H+. You balance with OH-
Tue Feb 26, 2019 7:13 pm
Forum: Balancing Redox Reactions
Topic: 6K.5 7th edition
Replies: 1
Views: 116

### Re: 6K.5 7th edition

You separate the two reactions. Br2(l) -> BrO3(^-1) (aq) and Br2(l) -> Br(^-1) (aq) and balance each separately.
Thu Feb 21, 2019 2:47 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Max Work
Replies: 5
Views: 198

### Re: Max Work

Isothermal, reversible reactions. The area under the curve of a Pressure v. Volume graph of a reversible reaction is greater than that of an irreversible reaction.
Thu Feb 21, 2019 2:40 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Units for Gibbs
Replies: 8
Views: 332

### Re: Units for Gibbs

It shouldn't matter. However almost all of the answers in the textbook are given in kJ.
Thu Feb 21, 2019 2:39 pm
Forum: Balancing Redox Reactions
Topic: Oxidation States
Replies: 10
Views: 383

### Re: Oxidation States

Some elements have too many possible oxidation states to memorize. They should be calculable from the reaction.
Wed Feb 13, 2019 10:08 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U equal to zero
Replies: 2
Views: 121

### Re: Delta U equal to zero

Delta U is equal to 0 for reversible processes.
Wed Feb 13, 2019 10:06 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: ΔS=q/t
Replies: 8
Views: 376

### Re: ΔS=q/t

ΔS=ΔH/T at constant pressure and temperature.
Wed Feb 13, 2019 10:05 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ΔU= 3/2nRT
Replies: 5
Views: 297

### Re: ΔU= 3/2nRT

I haven't really come across any problems using this equation.
Thu Feb 07, 2019 10:46 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: q= -w
Replies: 8
Views: 226

### Re: q= -w

Isothermal systems have a net energy change of zero so the work must be equal to the opposite of the amount of heat.
Thu Feb 07, 2019 10:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Open vs Closed System
Replies: 13
Views: 1049

### Re: Open vs Closed System

Another example of an isolated system would be a thermos.
Thu Feb 07, 2019 10:41 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar Heat Capacity
Replies: 3
Views: 151

### Re: Molar Heat Capacity

The equation Cp = Cv + R shows us that the heat capacity at constant pressure is higher than the heat capacity at constant volume.
Thu Jan 31, 2019 10:53 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Open, closed, or isolated systems
Replies: 10
Views: 5442

### Re: Open, closed, or isolated systems

An open system can exchange matter and energy. A closed system can exchange energy (e.g. heat) but not matter. An isolated system cannot exchange energy or matter.
Thu Jan 31, 2019 10:49 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Thermo Test/Midterm
Replies: 9
Views: 282

### Re: Thermo Test/Midterm

I think we would be expected to know them. We covered the material in 14A.
Thu Jan 31, 2019 10:47 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Gibbs
Replies: 5
Views: 231

### Re: Gibbs

Exergonic means that no work needs to be done for the reaction to occur. So the reaction is spontaneous.
Thu Jan 24, 2019 6:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units
Replies: 2
Views: 136

### Re: Units

For Kp we use bar or atm and for Kc we use mol/L for gases.
Thu Jan 24, 2019 6:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: PV= RnT
Replies: 2
Views: 186

### Re: PV= RnT

It is called the ideal gas law and it relates the pressure, volume, mols, and temperature of a gas.
Thu Jan 24, 2019 6:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH
Replies: 9
Views: 429

### Re: pH

pH tells us the acidity or basicity of a solution by measuring the concentration of hydrogen ions. We calculate it by taking the negative log of the concentration of hydronium ions. (pH = -log[H3O+])
Fri Jan 18, 2019 11:34 am
Forum: Ideal Gases
Topic: [Products] over [Reactants] cancellations
Replies: 3
Views: 160

### Re: [Products] over [Reactants] cancellations

It is a tool to make calculations easier. The concentration of the reactant is not significantly changed by subtracting the small x. Dr. Lavelle gave an example in class about a millionaire. If a millionaire gives \$1000 to someone, it does not really affect the total amount of money the millionaire ...
Fri Jan 18, 2019 11:25 am
Forum: Administrative Questions and Class Announcements
Topic: Studying for First Discussion Test
Replies: 10
Views: 346

### Re: Studying for First Discussion Test

I solve all of the homework problems before tests because this helped me last quarter in 14A. I am also going to redo the video module problems.
Fri Jan 18, 2019 11:23 am
Forum: Ideal Gases
Topic: Chemistry Community Posting
Replies: 7
Views: 256

### Re: Chemistry Community Posting

I believe it is by the end of the week on Sunday.
Wed Jan 09, 2019 10:59 pm
Forum: Ideal Gases
Topic: Units
Replies: 19
Views: 409

### Re: Units

The R constant's units are in Kelvin, so Kelvin should be used for temperature.
Wed Jan 09, 2019 10:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: how to write the formula for K
Replies: 6
Views: 170

### Re: how to write the formula for K

It depends on the state of the molecules in the equation. If they are gases then use P for partial pressure.
Wed Jan 09, 2019 10:56 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: "Shifting"
Replies: 15
Views: 1060

### Re: "Shifting"

Dr. Lavelle told us to use the phrases "favor the products" and "favor the reactants."
Wed Dec 05, 2018 10:32 pm
Forum: Naming
Topic: 7th edition 9.C1
Replies: 2
Views: 197

### Re: 7th edition 9.C1

You use cobaltate and ferrate if the complex is an anion and cobalt and iron if the complex is a cation.
Wed Dec 05, 2018 10:30 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar or nonpolar
Replies: 4
Views: 183

### Re: Polar or nonpolar

The molecule is polar regardless of the location of the Cl atoms because the molecule is tetrahedral-shaped. The position of Cl would matter and affect polarity if the shape was square planar.
Wed Dec 05, 2018 10:29 pm
Forum: Naming
Topic: Spelling
Replies: 4
Views: 168

### Re: Spelling

I believe it is ammine.
Thu Nov 29, 2018 2:52 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing power and polarizability
Replies: 4
Views: 230

### Re: Polarizing power and polarizability

Polarizability is usually used to describe anions and polarizing power is usually used for cations.
Thu Nov 29, 2018 2:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Formula: Central Atom
Replies: 4
Views: 171

### Re: VSEPR Formula: Central Atom

You consider one of the iodine atoms the central atom and the VSEPR formula predicts the shape around the central atom. For I3-, the VSEPR formula is AX2E3.
Thu Nov 29, 2018 2:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AX2E2
Replies: 14
Views: 1024

### Re: AX2E2

Its bond angles are less than 109.5 because of the presence of lone pairs.
Fri Nov 23, 2018 1:55 pm
Forum: Bond Lengths & Energies
Topic: H bonding
Replies: 14
Views: 701

### Re: H bonding

Dr. Lavelle's examples in class were H2O and H2S. H2O has a higher melting point at 0°C and higher boiling point at 100°C compared to H2S which has a melting point of -80°C and boiling point of -60°C. Since H2O has hydrogen bonds, the melting point and boiling point increase.
Fri Nov 23, 2018 1:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Drawing Structures on Test
Replies: 11
Views: 347

### Re: Drawing Structures on Test

I believe Dr. Lavelle said we only need to know how to draw Lewis structures, which would mean we don't need to draw the wedges. He said we would need to be able to name their shapes instead.
Fri Nov 23, 2018 1:46 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 3
Replies: 10
Views: 378

### Re: Test 3

Like said above, most of the homework problems and examples we covered in class don't have any major calculation elements, so I don't think Test 3 will.
Thu Nov 15, 2018 12:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: See-Saw Shape
Replies: 3
Views: 210

### Re: See-Saw Shape

Here is a visual of an example of a molecule with a see-saw shape.
Thu Nov 15, 2018 11:14 am
Forum: SI Units, Unit Conversions
Topic: bond angles
Replies: 5
Views: 606

### Re: bond angles

You arrange the bonding pairs and lone pairs around the central atom in a way that minimizes electron pair repulsion. For molecules where there is no lone pair around the central atom, the bond angles are 180 degrees for molecules with 2 bonding pairs around the central atom, 120 degrees for 3 bondi...
Thu Nov 15, 2018 11:10 am
Forum: SI Units, Unit Conversions
Topic: VSEPR model
Replies: 5
Views: 431

### Re: VSEPR model

It's the model we use to predict shapes of molecules and polyatomic ions.
Fri Nov 09, 2018 12:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Different Shapes
Replies: 4
Views: 129

### Re: Different Shapes

You can find the shape by drawing a Lewis structure to determine the number of bonding pairs around the central atom.
Fri Nov 09, 2018 12:09 pm
Forum: Dipole Moments
Topic: Bond Lengths
Replies: 3
Views: 152

### Re: Bond Lengths

Exact lengths have to be given, but you can figure out comparatively which bond lengths are longer or shorter. For example, a single bond would have a longer bond length than a triple bond.
Fri Nov 09, 2018 12:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shapes
Replies: 4
Views: 145

### Re: Molecular Shapes

They depend on both the bonding pairs and the lone pairs.
Thu Nov 01, 2018 11:35 am
Forum: Ionic & Covalent Bonds
Topic: 2A.19 7th edition
Replies: 3
Views: 161

### Re: 2A.19 7th edition

Electrons are removed from the 4s orbital before 3d electrons are removed, so you get [Ar]3d^8 instead of [Ar]3d^6 4s^2.
Thu Nov 01, 2018 11:24 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Filling of Orbitals
Replies: 3
Views: 176

### Re: Filling of Orbitals

Electrons are filled in this order: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p. This order can be figured out looking at the periodic table.
Thu Nov 01, 2018 11:12 am
Forum: Ionic & Covalent Bonds
Topic: Electrostatic Potential Energy
Replies: 2
Views: 175

### Re: Electrostatic Potential Energy

We didn't discuss this in class and there weren't any homework questions related to this topic, so I would assume no.
Thu Oct 25, 2018 12:34 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Module #37
Replies: 2
Views: 259

### Re: Atomic Spectra Module #37

I think the second question refers to whether the calculated results will match the experimentally observed results. Since they do confirm the experimentally observed results, the answer would be yes.
Thu Oct 25, 2018 12:29 pm
Forum: DeBroglie Equation
Topic: De Broglie module #35
Replies: 3
Views: 212

### Re: De Broglie module #35

Dr. Lavelle said that we don't have the ability to measure such small wavelengths, so a number as small as 6.94 x 10^-38m can be ignored.
Thu Oct 25, 2018 12:21 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Module Question 20
Replies: 4
Views: 318

### Re: Module Question 20

Multiply your answer by 6.022x10^23 because there are 6.022x10^23 electrons in 1 mol of electrons.
Tue Oct 16, 2018 10:35 pm
Forum: SI Units, Unit Conversions
Topic: Test and Exam Dates
Replies: 10
Views: 583

### Re: Test and Exam Dates

@Veronica Thanksgiving break is Thursday-Friday, November 22-23 during Week 8. We have a 4-day weekend.
Tue Oct 16, 2018 10:30 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Formulas?
Replies: 2
Views: 152

### Re: Formulas?

Dr. Lavelle's Quantum World Lecture Outline on his website specifies which equations we need to know.
Tue Oct 16, 2018 10:28 pm
Forum: DeBroglie Equation
Topic: Mass of electrons
Replies: 4
Views: 213

### Re: Mass of electrons

It's more practical to use kilograms to measure things. Though we measure the weight of small things like electrons in chemistry, kilograms is more useful in measuring everyday objects.
Wed Oct 10, 2018 8:27 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Threshold Energy
Replies: 4
Views: 104

### Re: Threshold Energy

The threshold energy is the work required to remove an electron from a metal surface. The energy of the photon must be greater or equal to the threshold energy in order to remove an electron from the surface. E(photon) - Threshold Energy = Kinetic Energy of Electron
Wed Oct 10, 2018 8:18 pm
Forum: Limiting Reactant Calculations
Topic: How to determine the limiting reactant???? [ENDORSED]
Replies: 8
Views: 1906

### Re: How to determine the limiting reactant????[ENDORSED]

I usually just test all of the reactants to see how much I get of one specific product. Whichever reactant gives me the least product (mol or grams) is the limiting reactant. It is sometimes inefficient when you're only asked to find the limiting reactant, but most problems I've run into end up aski...
Wed Oct 10, 2018 8:13 pm
Forum: Properties of Light
Topic: Light acts as a wave or not?
Replies: 10
Views: 253

### Re: Light acts as a wave or not?

Light acts as both, but we use the quantum model for specific topics and the wave model for others. Dr. Lavelle emphasized on Monday that the wave model does not apply to the photoelectric effect.
Wed Oct 03, 2018 10:29 pm
Forum: Balancing Chemical Reactions
Topic: Balancing reactions tips
Replies: 29
Views: 1183

### Re: Balancing reactions tips

I try to balance all other elements before balancing oxygen and hydrogen. If there are polyatomic ions within the problem, I balance those first, treating them as one unit.
Wed Oct 03, 2018 10:21 pm
Forum: Significant Figures
Topic: Sig Figs
Replies: 6
Views: 211

### Re: Sig Figs

400. or 4.00x10^2 would both work.
Mon Oct 01, 2018 11:36 am
Forum: Significant Figures
Topic: Significant Figures
Replies: 10
Views: 536

### Re: Significant Figures

You get the most accurate answer if you use the true value while you are calculating. Apply significant figures only to your final answer so you don't have rounding error.