Search found 49 matches

by Iris Bai 2K
Mon Feb 18, 2019 10:16 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Max Work
Replies: 2
Views: 7

Re: Max Work

Isothermal, reversible reactions allow for the maximum amount of work to be done.
by Iris Bai 2K
Mon Feb 18, 2019 10:14 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 7th edition 4I. 5
Replies: 2
Views: 14

Re: 7th edition 4I. 5

There are two values for delta S (one for hot and one for cold), and delta S total is just the sum of the two delta S values.
by Iris Bai 2K
Mon Feb 18, 2019 10:13 pm
Forum: Administrative Questions and Class Announcements
Topic: 14BL and 14C
Replies: 5
Views: 27

Re: 14BL and 14C

I'm taking LS 7B, a cluster, Chem 14B and BL this quarter and I don't think it's that bad. BL is mostly busy work so you don't have to spend a lot of time studying. I usually spend about 3 hours a week outside of class on the labs.
by Iris Bai 2K
Mon Feb 18, 2019 10:08 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Molar Gibbs free energy
Replies: 3
Views: 12

Re: Molar Gibbs free energy

Standard usually means at 1mol, 1 atm, and 298 K, and molar only requires 1 mol I think.
by Iris Bai 2K
Sun Feb 10, 2019 5:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 6th Edition, 8.99
Replies: 1
Views: 32

Re: 6th Edition, 8.99

If the specific heat capacity is the same as water, it shouldn't be negative. The constant is on the formula sheet. Usually, a problem will tell you that one reactant is in excess; if it doesn't, you probably need to find the limiting reactant.
by Iris Bai 2K
Sun Feb 10, 2019 5:34 pm
Forum: Ideal Gases
Topic: Calculating Pressure of a Gas Mixture Using PV=nRT
Replies: 2
Views: 15

Re: Calculating Pressure of a Gas Mixture Using PV=nRT

Yes, but you can also just add the moles of helium and krypton together before calculating anything. The answer wont change.
by Iris Bai 2K
Sun Feb 10, 2019 5:33 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: equations for q
Replies: 4
Views: 16

Re: equations for q

You use q=nC(delta)T when you are given the amount of moles, and q=mCdeltaT when you are given the mass, I don't think q=C(delta)T should really be used.
by Iris Bai 2K
Mon Feb 04, 2019 12:20 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 4
Views: 18

Re: Bond Enthalpies

I don't think so unless you know the structures in your head.
by Iris Bai 2K
Sat Feb 02, 2019 12:14 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: breaking double bonds?
Replies: 6
Views: 29

Re: breaking double bonds?

Dr. Lavelle said in lecture that double bonds have to break completely in order to form a single bond between the same two atoms. It's probably because a single bond isn't actually half the energy of a double bond, so you can't just break one of the bonds in a double bond.
by Iris Bai 2K
Fri Feb 01, 2019 4:18 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: CP/V
Replies: 2
Views: 28

Re: CP/V

C is just heat capacity, and Cp molar heat capacity at constant pressure while Cv is molar heat capacity at constant volume.
by Iris Bai 2K
Thu Jan 31, 2019 1:05 pm
Forum: Phase Changes & Related Calculations
Topic: HW problem 8.5
Replies: 3
Views: 20

Re: HW problem 8.5

Both changes in energy are acting on the gas, so the change in energy of the gas is just the addition of the two values.
by Iris Bai 2K
Thu Jan 31, 2019 1:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpy
Replies: 4
Views: 27

Re: Standard Enthalpy

The standard enthalpy of formation of O2 is 0, not the standard enthalpy (idk if that's even a thing). It's because oxygen is found naturally as a diatomic molecule, so it doesn't take energy to "form" it the way it's found in nature.
by Iris Bai 2K
Fri Jan 25, 2019 11:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method 2
Replies: 3
Views: 24

Re: Method 2

Because diatomic molecules are not bonded to anything else, the bond enthalpies measured for those bonds are the most accurate. If that same bond occurs in a larger molecule, the bond enthalpy for the same bond in the larger molecule may be slightly different.
by Iris Bai 2K
Fri Jan 25, 2019 11:06 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Equations, Adams Disc 1A
Replies: 2
Views: 28

Re: Equations, Adams Disc 1A

We'll probably be given all the values we need to do the problems
by Iris Bai 2K
Wed Jan 16, 2019 9:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE
Replies: 5
Views: 24

Re: ICE

X is just a variable used to find the value you are looking for. I would set X as whatever concentration the question is asking you to find.
by Iris Bai 2K
Wed Jan 16, 2019 9:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: States
Replies: 1
Views: 17

Re: States

Solids have no concentration and liquids only have concentration if they are in a solvent (if the solvent is water it's aqueous not liquid). I'm not sure what you mean by water and gas. Concentration is usually found in moles of solute/liters of solvent.
by Iris Bai 2K
Sun Jan 13, 2019 2:06 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.43 in 6th Edition
Replies: 2
Views: 19

Re: 11.43 in 6th Edition

I would complete the ICE table using partial pressures and convert your answer to molar concentrations afterwards.
by Iris Bai 2K
Tue Jan 08, 2019 11:09 pm
Forum: Ideal Gases
Topic: Q and Spontaneity
Replies: 1
Views: 30

Re: Q and Spontaneity

If Q is less than K, that means there is a higher concentration of reactants than products compared to the respective concentrations at equilibrium. Since all systems want to be at equilibrium, this scenario would favor the forward reaction in order to decrease the reactant concentration, making the...
by Iris Bai 2K
Mon Jan 07, 2019 9:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Aqueous in K expression
Replies: 4
Views: 30

Re: Aqueous in K expression

The K expression includes anything thats aqueous or gaseous.
by Iris Bai 2K
Fri Dec 07, 2018 12:56 pm
Forum: Calculating the pH of Salt Solutions
Topic: pH on final
Replies: 3
Views: 42

Re: pH on final

I'm pretty sure we just need to know how to calculate pH given an H+ concentration or how to calculate H+ concentration given a pH.
by Iris Bai 2K
Fri Dec 07, 2018 12:51 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Difference Between Ka and Kb
Replies: 2
Views: 27

Re: Difference Between Ka and Kb

Ka is the equilibrium constant for acids, and Ka is the equilibrium constant for bases. For an acid that is ionized, you would fine Ka, not Kb.
by Iris Bai 2K
Tue Dec 04, 2018 2:08 pm
Forum: Identifying Acidic & Basic Salts
Topic: Determining if a salt is basic or acidic?
Replies: 1
Views: 77

Re: Determining if a salt is basic or acidic?

I'm not sure about the justification equation, but to determine whether a compound is acidic or basic, you look at the conjugate acid/base in each salt. For example, in NH4Br is made of NH4+ and Br-. The conjugate base would be NH3 (weak base), and the conjugate acid would be HBr (strong acid). Ther...
by Iris Bai 2K
Sat Dec 01, 2018 3:30 am
Forum: Naming
Topic: Neutral ligand
Replies: 2
Views: 42

Re: Neutral ligand

The oxidation number of the metal will be the same as the charge of the complex.
by Iris Bai 2K
Sat Dec 01, 2018 3:29 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Substitution Reaction
Replies: 1
Views: 34

Re: Substitution Reaction

I remember in lecture Dr. Lavelle said that CN- ions are more attractive to central ions than H2O, so they replace the water. I'm pretty sure it's because CN- has a full charge, so it will be more attracted to the cation in the center. Water is a neutral molecule, so the first coordination complex h...
by Iris Bai 2K
Sat Nov 24, 2018 6:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Single vs Double bond electron diffusity
Replies: 2
Views: 40

Re: Single vs Double bond electron diffusity

Double and triple bonds would cause more repulsion between itself and other bonded or lone electrons in the molecule. I wouldn't really say it takes up more space, but it will cause other electrons to be further away.
by Iris Bai 2K
Sat Nov 24, 2018 6:44 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi bonds
Replies: 5
Views: 56

Re: Sigma and Pi bonds

I think they will just ask us to identify how many sigma or pi bonds there are in a molecule.
by Iris Bai 2K
Wed Nov 21, 2018 12:07 am
Forum: Hybridization
Topic: predicting hybrids
Replies: 3
Views: 28

Re: predicting hybrids

The number of bonded pairs in the molecule is the same as the number of orbitals in the hybridized orbital. For example, if there are 3 bonded pairs, then the hybridization is sp2. If there are 4, then it's sp3, and so on.
by Iris Bai 2K
Wed Nov 21, 2018 12:04 am
Forum: Hybridization
Topic: Electron Density vs Shape?
Replies: 6
Views: 48

Re: Electron Density vs Shape?

Electron density includes both lone pairs and bonding electrons. Accounting for all the areas of electron density gives you the molecular orbital geometry. VSEPR geometry only accounts for the bonded electrons.
by Iris Bai 2K
Thu Nov 15, 2018 3:55 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: Polar and Dipole
Replies: 3
Views: 63

Re: Polar and Dipole

If a molecule is polarized, there is a positive and negative dipole. If not, there are no dipoles except instantaneous dipoles.
by Iris Bai 2K
Thu Nov 15, 2018 3:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.3 part B 6th edition
Replies: 1
Views: 23

Re: 4.3 part B 6th edition

I don't think it matters in this question because they don't specify which isomer we need to draw. The orientation that you draw the molecule in doesn't matter because the molecule is always moving.
by Iris Bai 2K
Thu Nov 15, 2018 3:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Double Bonds in VSEPR
Replies: 5
Views: 32

Re: Double Bonds in VSEPR

If there's a double bond you should still draw the double bond in the VSEPR model, but it would not change the shape.
by Iris Bai 2K
Mon Nov 12, 2018 12:10 am
Forum: Formal Charge and Oxidation Numbers
Topic: 3.53 6th edition
Replies: 4
Views: 70

Re: 3.53 6th edition

Use the formula FC=V-(L+S) to determine the formal charge. The structure that has more atoms with a formal charge of 0 has lower energy.
by Iris Bai 2K
Mon Nov 12, 2018 12:05 am
Forum: Coordinate Covalent Bonds
Topic: Shape of the Molecule Contributes to Strength of Interaction
Replies: 2
Views: 63

Re: Shape of the Molecule Contributes to Strength of Interaction

Pentane is just a string of 5 carbon molecules bonded to hydrogen atoms with single bonds. 2,2-Dimethylpropane is a string of 3 carbon atoms with two methyl groups attached to the second carbon in the chain (it looks like a + sign) with hydrogens bonded to the outer carbon atoms. The have the same m...
by Iris Bai 2K
Mon Nov 12, 2018 12:01 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Chapter 4 Homework Number 1
Replies: 6
Views: 47

Re: Chapter 4 Homework Number 1

yes. depending on how many lone pairs there are, the bond angles will change.
by Iris Bai 2K
Mon Nov 05, 2018 4:44 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 6 HOmework
Replies: 4
Views: 103

Re: Week 6 HOmework

yes
by Iris Bai 2K
Fri Nov 02, 2018 9:31 am
Forum: Quantum Numbers and The H-Atom
Topic: Spin Quantum Number
Replies: 1
Views: 34

Re: Spin Quantum Number

If it's the first electron to go in that orbital, the spin number is -1/2. If it's the second electron to go in that orbital, the spin number is +1/2. More simply, if the atom is in the first half of the block it's in, the electron will have a spin number of -1/2, and vice versa.
by Iris Bai 2K
Fri Nov 02, 2018 8:44 am
Forum: Lewis Structures
Topic: 2B. 9 7th edition chemical formula of sodium hypochloride
Replies: 1
Views: 45

Re: 2B. 9 7th edition chemical formula of sodium hypochloride

Since he doesn't require us to memorize the polyatomic ions, I'm pretty sure he'll give us the formulas on the tests.
by Iris Bai 2K
Mon Oct 29, 2018 9:02 pm
Forum: Electronegativity
Topic: Periodic Trends
Replies: 10
Views: 138

Re: Periodic Trends

All size ones generally increase to the bottom left, and all reactivity ones generally increase to the top right, but understanding the reasoning makes it a lot easier.
by Iris Bai 2K
Mon Oct 29, 2018 6:29 pm
Forum: Trends in The Periodic Table
Topic: 1f.19
Replies: 1
Views: 42

Re: 1f.19

S-block metals have lower ionization energies, which makes it easier for them to give electrons and form compounds.
by Iris Bai 2K
Mon Oct 29, 2018 6:27 pm
Forum: Ionic & Covalent Bonds
Topic: Ion formation and unpaired e-
Replies: 2
Views: 32

Re: Ion formation and unpaired e-

When the d orbital can be half filled or completely filled, the electrons will try to fill the orbital instead of going to the s orbital. It's similar to the Cr and Cu examples Dr. Lavelle gave in lecture.
by Iris Bai 2K
Wed Oct 17, 2018 2:57 pm
Forum: Einstein Equation
Topic: Energy Equations
Replies: 4
Views: 32

Re: Energy Equations

You use E=hv when looking at light as a wave, and you use E=pc when looking at light as a particle.
by Iris Bai 2K
Wed Oct 17, 2018 2:54 pm
Forum: Photoelectric Effect
Topic: Speed of Light
Replies: 5
Views: 76

Re: Speed of Light

Light travels faster than anything else, so it's not possible for anything to be faster than the speed of light.
by Iris Bai 2K
Wed Oct 17, 2018 2:53 pm
Forum: Properties of Light
Topic: Intensity vs. Amplitude
Replies: 5
Views: 48

Re: Intensity vs. Amplitude

A photon of light is a fixed amount for each electron in each element, so there is no change in intensity of a particular photon.
by Iris Bai 2K
Tue Oct 09, 2018 11:13 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: molar masses on the test
Replies: 7
Views: 138

Re: molar masses on the test

We're given a periodic table, so all the molar masses should be on there.
by Iris Bai 2K
Tue Oct 09, 2018 11:13 pm
Forum: Significant Figures
Topic: Test 1
Replies: 3
Views: 120

Re: Test 1

Constants will be given.
by Iris Bai 2K
Sun Oct 07, 2018 10:34 pm
Forum: Balancing Chemical Reactions
Topic: 7th edition L.35
Replies: 5
Views: 158

Re: 7th edition L.35

I think Dr. Lavelle mentioned during a lecture that O2 is sometimes left out of the reactants if it's an unbalanced equation, so you would have to add that in as a reactant. The balanced equation would then be 6FeBr2+ 6Na2CO3 + O2--> 12NaBr + 6CO2 +2Fe3O4.
by Iris Bai 2K
Thu Oct 04, 2018 11:57 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reactant
Replies: 8
Views: 108

Re: Limiting Reactant

I'm pretty sure you need to do both calculations.
by Iris Bai 2K
Mon Oct 01, 2018 12:21 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reactant Calculation Question [ENDORSED]
Replies: 2
Views: 70

Re: Limiting Reactant Calculation Question [ENDORSED]

You would multiply the 1.56 mol reactant by 4 mol product/5 mol reactant. This uses stoichiometry to convert the moles of reactant into moles of product.
by Iris Bai 2K
Mon Oct 01, 2018 12:13 pm
Forum: Empirical & Molecular Formulas
Topic: Tin (IV) Dioxide [ENDORSED]
Replies: 1
Views: 63

Re: Tin (IV) Dioxide [ENDORSED]

Tin has different oxidation states, so the IV is needed to show that tin has a +4 charge and not a +2 charge.

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