Search found 81 matches

by Viviana Velasquez
Thu Feb 20, 2020 11:28 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Purpose of Salt Bridge
Replies: 12
Views: 30

Purpose of Salt Bridge

Can someone explain what the salt bridge does and how it achieves it's purpose?
by Viviana Velasquez
Thu Feb 20, 2020 11:26 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cathode to the Right Rule
Replies: 6
Views: 19

Re: Cathode to the Right Rule

The cathode will typically be placed on the right, but you should double check anyways because I have seen diagrams where they are flipped. However, Lavelle made it seem like it will always be on the right for this class.
by Viviana Velasquez
Thu Feb 20, 2020 11:21 am
Forum: Balancing Redox Reactions
Topic: Understanding Half-Reactions
Replies: 11
Views: 31

Re: Understanding Half-Reactions

The half reactions separates the oxidation and reduction that is happening in the reaction. Also it makes it a lot easier to balance if you split them up.
by Viviana Velasquez
Thu Feb 20, 2020 11:20 am
Forum: Balancing Redox Reactions
Topic: Balancing half reactions
Replies: 11
Views: 28

Re: Balancing half reactions

Yes, you have to cancel out the electrons on both sides. Most times you'll have to multiply at least one of the half reactions in order to get the same amount of electrons on each side to be able to cancel them out.
by Viviana Velasquez
Thu Feb 20, 2020 11:18 am
Forum: Balancing Redox Reactions
Topic: Reduction vs. oxidation
Replies: 29
Views: 66

Re: Reduction vs. oxidation

Oxidation is losing electrons and reduction is gaining electrons (OIL RIG). If the positive charge decreases, it is being reduced. If the positive charge increases, it is being oxidized.
by Viviana Velasquez
Wed Feb 19, 2020 12:13 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: rxn gibbs free energy
Replies: 5
Views: 23

Re: rxn gibbs free energy

For a reaction to be spontaneous, delta G has to be negative. When delta G is negative, it means the forward reaction is favored and products are formed. When delta G is positive, the opposite happens and reactants are formed.
by Viviana Velasquez
Wed Feb 19, 2020 12:10 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equilibrium
Replies: 15
Views: 50

Re: Equilibrium

Since K=1 at equilibrium and the equation is RTln(K), ln(1)=0 making Delta G=0
by Viviana Velasquez
Wed Feb 19, 2020 12:08 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm Curve
Replies: 45
Views: 249

Re: Midterm Curve

He does not curve but they are super generous with points and your grade depends on points, not percentage.
by Viviana Velasquez
Wed Feb 19, 2020 12:07 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: importance of -RTlnk
Replies: 7
Views: 29

Re: importance of -RTlnk

I think its importance is linked back to the way temperature affects it
by Viviana Velasquez
Wed Feb 19, 2020 12:05 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta G vs. delta G naught
Replies: 6
Views: 20

Re: delta G vs. delta G naught

Delta g naught is under standard condition unlike delta G that can be any condition
by Viviana Velasquez
Sun Feb 09, 2020 4:04 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneous rxns
Replies: 3
Views: 20

Re: Spontaneous rxns

There are cases where entropy increases due to an increase in volume, but I am not sure if that is the case for all reactions or if the assumption can be made
by Viviana Velasquez
Sun Feb 09, 2020 4:02 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: change in entropy
Replies: 3
Views: 13

Re: change in entropy

You can us delta H instead of q because at constant pressure, q(p)= delta H
by Viviana Velasquez
Sun Feb 09, 2020 3:58 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cv Cp
Replies: 3
Views: 16

Re: Cv Cp

You use it depending on whether you are solving for heat at constant pressure or constant volume. Often times the problem will tell you directly whether it is constant pressure or volume and other times you will have to read the problem carefully and deduce which one it is at.
by Viviana Velasquez
Sun Feb 09, 2020 3:53 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Entropy units
Replies: 5
Views: 28

Re: Entropy units

I think either Joules or kilo joules is fine as long as you stay consistent throughout the entire problem to make sure no calculation mistakes are made. I would just make sure to read if the question asks for any units in specific
by Viviana Velasquez
Sun Feb 09, 2020 3:50 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free energy
Replies: 5
Views: 29

Re: Free energy

I think the standard free energy conditions is the one measured in the lab and the regular free energy change occurs in real life systems
by Viviana Velasquez
Mon Feb 03, 2020 7:34 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Combustion
Replies: 5
Views: 20

Re: Combustion

Yes at 25 degrees it is in liquid form. If they were to not give you a temperature I would say its safe to assume its in liquid form.
by Viviana Velasquez
Mon Feb 03, 2020 7:29 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Value of q
Replies: 11
Views: 56

Re: Value of q

The system's q is equal to the -q of the surroundings
by Viviana Velasquez
Mon Feb 03, 2020 7:22 pm
Forum: Calculating Work of Expansion
Topic: Calculus on The Midterm
Replies: 8
Views: 28

Re: Calculus on The Midterm

I don't think its necessary, but I think he was trying to show how the equation is derived.
by Viviana Velasquez
Mon Feb 03, 2020 7:20 pm
Forum: Calculating Work of Expansion
Topic: Intergral
Replies: 6
Views: 22

Re: Intergral

I think he was just showing how the equation is derived.
by Viviana Velasquez
Sun Jan 26, 2020 6:50 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: biological examples
Replies: 7
Views: 42

Re: biological examples

I don't remember going over this either. I feel like he might have specifically gone over it in class since that is what he did last quarter in 14A.
by Viviana Velasquez
Sun Jan 26, 2020 6:47 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic reaction
Replies: 18
Views: 44

Re: Exothermic reaction

Increasing the temperature will shift the reaction to the left and decreasing it will shift it to the right. This has to do with the fact that exothermic reactions have heat as a product
by Viviana Velasquez
Sun Jan 26, 2020 6:43 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Gas Constant
Replies: 13
Views: 29

Gas Constant

Which gas constant are we expected to use for the equation PV=nRT?
by Viviana Velasquez
Sun Jan 26, 2020 6:42 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changing K
Replies: 13
Views: 51

Re: Changing K

Only temperature can change the value of K.
by Viviana Velasquez
Sun Jan 26, 2020 6:37 pm
Forum: Phase Changes & Related Calculations
Topic: Why does steam cause burns?
Replies: 29
Views: 108

Re: Why does steam cause burns?

He explained that because steam experiences a phase change when it comes into contact with skin, it releases a big amount of heat and therefore causes severe burns.
by Viviana Velasquez
Sun Jan 19, 2020 6:47 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Strong Acids/Bases vs. Weak Acids/Bases
Replies: 9
Views: 26

Re: Strong Acids/Bases vs. Weak Acids/Bases

In 14A we had to memorize a list from the textbook, so I'm assuming you just have to refresh your memory on those for this course
by Viviana Velasquez
Sun Jan 19, 2020 6:45 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pKa
Replies: 13
Views: 23

Re: pKa

They're inversely related:
lower pKa= stronger acid
higher pKa= weaker acid
by Viviana Velasquez
Sun Jan 19, 2020 6:42 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Solids and Liquids
Replies: 6
Views: 23

Re: Solids and Liquids

Lavelle mentioned that it had something to do with their concentrations not changing so they were insignificant.
by Viviana Velasquez
Sun Jan 19, 2020 6:37 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE Tables
Replies: 13
Views: 35

Re: ICE Tables

It's usually because it is in liquid form, but you only include H2O when it is aqueous or gas form.
by Viviana Velasquez
Sun Jan 19, 2020 6:34 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: X was ignored
Replies: 27
Views: 82

Re: X was ignored

X was ignored since K was so small (less than 10^-3) and X would make such a small change to .10
by Viviana Velasquez
Sun Jan 12, 2020 9:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: memorization
Replies: 12
Views: 38

Re: memorization

It's unlikely that we will have to memorize them, but I suggest asking your TA just to be sure.
by Viviana Velasquez
Sun Jan 12, 2020 9:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K and Q
Replies: 10
Views: 26

Re: K and Q

K is the equilibrium constant and Q tells you the constant of the equation when it is not at equilibrium. Q helps you judge whether it is a forward or backwards reaction.
by Viviana Velasquez
Sun Jan 12, 2020 9:00 pm
Forum: Ideal Gases
Topic: converting Kc to Kp
Replies: 13
Views: 76

Re: converting Kc to Kp

Naren_Ramesh_4F wrote:When asked the equilibrium constant of a chemical reaction involving gases, do we solve for Kc or Kp?

You would solve for Kp since the P stands for partial pressure. Remember that if they ask for the equilibrium constant of a gas always assume you use Kp unless stated otherwise.
by Viviana Velasquez
Sun Jan 12, 2020 8:58 pm
Forum: Ideal Gases
Topic: Test 1
Replies: 7
Views: 52

Re: Test 1

The best way to study for the test is to make sure you know what's on his outlines. He goes based off of that for the most part.
by Viviana Velasquez
Sun Jan 12, 2020 8:57 pm
Forum: Ideal Gases
Topic: Kc and Kp
Replies: 8
Views: 19

Re: Kc and Kp

Kc is the equilibrium constant in concentrations and Kp is the equilibrium constant for gases which is in partial pressure.
by Viviana Velasquez
Sat Dec 07, 2019 9:51 pm
Forum: Biological Examples
Topic: Chemotherapy drugs
Replies: 7
Views: 60

Re: Chemotherapy drugs

There are more examples, but this one was talked about heavily in class and at various review sessions.
by Viviana Velasquez
Sat Dec 07, 2019 9:47 pm
Forum: Biological Examples
Topic: Final
Replies: 6
Views: 66

Re: Final

I know some of the more important ones are DNA bonding and cisplatin (the chemotherapy drug talked about in class).
by Viviana Velasquez
Sat Dec 07, 2019 9:45 pm
Forum: Bronsted Acids & Bases
Topic: Hydrogen Bonding
Replies: 10
Views: 65

Re: Hydrogen Bonding

I think it would just be considered an intermolecular force.
by Viviana Velasquez
Sat Dec 07, 2019 9:41 pm
Forum: Bronsted Acids & Bases
Topic: Strong Vs. Weak Acids and Bases
Replies: 2
Views: 26

Re: Strong Vs. Weak Acids and Bases

It would be helpful! Here are a few
Strong Acids: HCl, H2SO4, HNO3, HI, HBr, HClO4, HClO3
Strong Bases: LiOH, NaOH, Ba(OH)2, KOH, Ca(OH)2
by Viviana Velasquez
Sat Dec 07, 2019 9:36 pm
Forum: Lewis Acids & Bases
Topic: Strong bases
Replies: 2
Views: 29

Re: Strong bases

Some strong bases that you should know are :
LiOH, NaOH, Ba(OH)2, KOH, Ca(OH)2
by Viviana Velasquez
Sun Dec 01, 2019 8:06 pm
Forum: Administrative Questions and Class Announcements
Topic: Curve
Replies: 3
Views: 61

Re: Curve

Is it true that we only need 250 points to pass the class?
by Viviana Velasquez
Sun Dec 01, 2019 7:45 pm
Forum: Conjugate Acids & Bases
Topic: Naming Coordinate Compounds
Replies: 2
Views: 21

Re: Naming Coordinate Compounds

Yeah the best way to do it is just to practice a bunch. There's charts with the naming rules that might be helpful if you memorize.
by Viviana Velasquez
Sun Dec 01, 2019 7:36 pm
Forum: Lewis Acids & Bases
Topic: Proton acceptor and proton donor?
Replies: 33
Views: 139

Re: Proton acceptor and proton donor?

The proton acceptor would be the base and the proton donor is the acid.
by Viviana Velasquez
Sun Dec 01, 2019 7:19 pm
Forum: Dipole Moments
Topic: Hydrogen Bonding
Replies: 17
Views: 194

Re: Hydrogen Bonding

Yes, hydrogen bonding only occurs when H is bonded with N, O, or F.
by Viviana Velasquez
Sun Dec 01, 2019 7:15 pm
Forum: Hybridization
Topic: Applying Hybridization
Replies: 2
Views: 33

Applying Hybridization

I'm having trouble understanding when to use hybridization or when it's being used, can someone explain?
by Viviana Velasquez
Sun Nov 17, 2019 4:16 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 10
Views: 65

Bond Length

How do we determine bond lengths?
by Viviana Velasquez
Sun Nov 17, 2019 4:12 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: AXE formula
Replies: 32
Views: 1714

Re: AXE formula

Yes, you should be able to determine the shape of a molecule based on the AXE formula.
by Viviana Velasquez
Sun Nov 17, 2019 4:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole moments
Replies: 4
Views: 27

Re: Dipole moments

The atom points in the direction of the more electronegative atom.
by Viviana Velasquez
Sun Nov 17, 2019 4:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 1
Views: 14

Bond Angles

How do you determine the bond angle? Do we have to know the exact angle measurement or just as long as we phrase it as "less than ___"?
by Viviana Velasquez
Sun Nov 10, 2019 9:48 pm
Forum: Bond Lengths & Energies
Topic: test 2
Replies: 16
Views: 92

Re: test 2

I think it will probably be on what we learn after the midterm and maybe include chemical bonding.
by Viviana Velasquez
Sun Nov 10, 2019 9:44 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: The exceptions
Replies: 6
Views: 67

Re: The exceptions

Copper and Chromium are two exceptions.
by Viviana Velasquez
Sun Nov 10, 2019 9:42 pm
Forum: Lewis Structures
Topic: Does the shape that I draw the Lewis structure matter?
Replies: 14
Views: 71

Re: Does the shape that I draw the Lewis structure matter?

Shape will probably matter when we go over that lecture, but right now it does not matter.
by Viviana Velasquez
Sun Nov 10, 2019 9:40 pm
Forum: Lewis Structures
Topic: Midterm grades
Replies: 26
Views: 249

Re: Midterm grades

I believe it is Wednesday, but if not then by Friday.
by Viviana Velasquez
Tue Nov 05, 2019 12:13 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Magnetic Quantum numbers
Replies: 4
Views: 50

Magnetic Quantum numbers

What are magnetic quantum numbers and how do you find them?
by Viviana Velasquez
Wed Oct 30, 2019 11:39 pm
Forum: Properties of Electrons
Topic: Knowing masses
Replies: 2
Views: 52

Knowing masses

Are expected to memorize the masses of electrons, protons, and neutrons? Only asking because the homework has problems where these values are not given in the problem.
by Viviana Velasquez
Wed Oct 30, 2019 2:33 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: d block before s block
Replies: 3
Views: 24

d block before s block

Can somebody explain why you would put 3d^6 4s^2 instead of the other way around?
by Viviana Velasquez
Wed Oct 30, 2019 2:30 am
Forum: Photoelectric Effect
Topic: When energy is equal to work function
Replies: 9
Views: 90

Re: When energy is equal to work function

When the energy of the photon is equal to the work function, the electron will be ejected. However, there will no excess energy (kinetic energy).
by Viviana Velasquez
Wed Oct 30, 2019 2:27 am
Forum: Photoelectric Effect
Topic: Increasing Light Intensity Photoelectric Effect
Replies: 7
Views: 38

Re: Increasing Light Intensity Photoelectric Effect

Yes, as long as the frequency is equal to or greater than the threshold energy needed to eject an electron, increasing the light intensity will increase the # of electrons ejected. It won't affect the kinetic energy.
by Viviana Velasquez
Wed Oct 30, 2019 2:22 am
Forum: *Black Body Radiation
Topic: Info for Midterm
Replies: 7
Views: 119

Info for Midterm

What exactly do we need to know about black body radiation for the midterm?
by Viviana Velasquez
Wed Oct 30, 2019 2:20 am
Forum: Ionic & Covalent Bonds
Topic: Homework for Week 5
Replies: 8
Views: 57

Homework for Week 5

Do we need to do homework for chemical bonding this week or can we still do quantum to review?
by Viviana Velasquez
Sat Oct 26, 2019 5:55 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy
Replies: 7
Views: 81

Re: Ionization Energy

The ionization energy of the second electron is always higher because when you remove an electron, the pull between protons and electrons become stronger (requiring more energy to remove)
by Viviana Velasquez
Sat Oct 26, 2019 5:44 pm
Forum: Resonance Structures
Topic: Formal Charge
Replies: 13
Views: 523

Re: Formal Charge

Usually, you want the central atom to be the one with the formal charge of 0 if it is not possible for all atoms to have a formal charge of zero.
by Viviana Velasquez
Sat Oct 26, 2019 5:31 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 8
Views: 57

Re: Drawing Lewis Structures

Hydrogen is an exception. It will never be the central atom.
by Viviana Velasquez
Sat Oct 26, 2019 5:25 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration
Replies: 1
Views: 31

Electron Configuration

Can somebody break down how to figure out electron configuration?
by Viviana Velasquez
Sat Oct 26, 2019 1:57 am
Forum: Trends in The Periodic Table
Topic: Ionization energy
Replies: 12
Views: 99

Ionization energy

Are we expected to know a specific formula for ionization energy or only the general trends of ionization energy?
by Viviana Velasquez
Sun Oct 20, 2019 10:14 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Spin up and spin down
Replies: 13
Views: 111

Re: Spin up and spin down

Do we always assume that it's spin up and spin down for this class?
by Viviana Velasquez
Sun Oct 20, 2019 9:54 pm
Forum: Properties of Light
Topic: Midterm Exam
Replies: 21
Views: 190

Re: Midterm Exam

If the class isn't curved, how many points are needed to pass the class? I remember reading something about using the class average at the end and needing at least 50% on the syllabus.
by Viviana Velasquez
Sun Oct 20, 2019 9:50 pm
Forum: Properties of Light
Topic: What are the units of hertz
Replies: 41
Views: 239

Re: What are the units of hertz

Hz would be s^-1 which implies 1 cycle per second
by Viviana Velasquez
Sun Oct 20, 2019 9:49 pm
Forum: Properties of Light
Topic: homework 1A.3
Replies: 8
Views: 62

Re: homework 1A.3

When frequency decreases, the wavelength would increase because you'd be dividing the speed of light by a smaller frequency. wavelength= (speed of light)/(frequency)
by Viviana Velasquez
Sun Oct 20, 2019 9:46 pm
Forum: Properties of Light
Topic: Next test
Replies: 23
Views: 214

Re: Next test

We should be getting an equation sheet with constants as well, if I'm not mistaken.
by Viviana Velasquez
Sun Oct 13, 2019 10:26 pm
Forum: Properties of Electrons
Topic: Photons
Replies: 5
Views: 39

Re: Photons

So only the change in energy of a photon can be negative?
by Viviana Velasquez
Sun Oct 13, 2019 4:04 pm
Forum: Properties of Electrons
Topic: Photons
Replies: 5
Views: 39

Photons

Can somebody explain why the energy of a photon is always positive?
by Viviana Velasquez
Sun Oct 13, 2019 3:55 pm
Forum: Molarity, Solutions, Dilutions
Topic: M1V1=M2V2
Replies: 11
Views: 142

Re: M1V1=M2V2

This equation can be used when you are given any of the three values needed for the completion of the equation. For example if you are asked to find the V1, you will need to have M1, M2, and V2 in order to be able to use this equation.
by Viviana Velasquez
Sun Oct 13, 2019 3:52 pm
Forum: Empirical & Molecular Formulas
Topic: Converting from grams to percentage
Replies: 11
Views: 107

Re: Converting from grams to percentage

You should convert the grams to a percentage when you are given the amount of grams of each element and the total mass of the compound to find the mass percentage composition. Then assuming you have 100 g, you would convert the percentage to grams and then moles. Sometimes the mass percentage compos...
by Viviana Velasquez
Sun Oct 13, 2019 3:45 pm
Forum: Significant Figures
Topic: How many significant figures are in 7.00 x 10^2?
Replies: 12
Views: 150

Re: How many significant figures are in 7.00 x 10^2?

You would have 3 significant figures because the zeros after the decimal are counted as significant figures.
by Viviana Velasquez
Sun Oct 06, 2019 8:15 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Theoretical vs. Actual Yield
Replies: 38
Views: 479

Re: Theoretical vs. Actual Yield

The theoretical yield is what you're supposed to get if there are no errors or other factors that affect the experiment. However sometimes factors such as the experiment sticking to the side of the test tube will reduce the amount of yield (actual yield).
by Viviana Velasquez
Sun Oct 06, 2019 8:06 pm
Forum: Balancing Chemical Reactions
Topic: H.19
Replies: 2
Views: 23

H.19

Hi, I could use some help doing homework problem H.19:
Write balanced equation for the combustion of the solid C11H18N2O5 to carbon dioxide gas, liquid water, and nitrogen gas.
by Viviana Velasquez
Sun Oct 06, 2019 7:56 pm
Forum: Administrative Questions and Class Announcements
Topic: using older edition textbook
Replies: 8
Views: 88

Re: using older edition textbook

I've heard the 6th edition and the 7th edition are pretty much the same, but you might want to ask your TA to be sure that you can use any other edition besides the 7th.
by Viviana Velasquez
Sun Oct 06, 2019 7:53 pm
Forum: SI Units, Unit Conversions
Topic: Sig figs
Replies: 5
Views: 43

Re: Sig figs

That .0 makes the difference between only using one sig fig and using 3 sig figs.
by Viviana Velasquez
Sun Oct 06, 2019 7:42 pm
Forum: Significant Figures
Topic: Number of significant figures
Replies: 5
Views: 37

Re: Number of significant figures

You're supposed to go based off the value with lowest significant figures given in the problem. For example, if you were given the values 6.38 and 43.58 in a homework problem, your final answer should include 3 significant figures.

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