Search found 59 matches

by Joon Chang 2F
Sat Mar 16, 2019 4:32 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst
Replies: 14
Views: 179

Re: Nernst

Megan_Ervin_1F wrote:do you think we have to know how to derive the nernst equation for our final?

Outline 5 says "Know how to derive the Nernst equation and use it to calculate the cell potential as a function of concentration" so I'm pretty sure.
by Joon Chang 2F
Fri Mar 08, 2019 11:28 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 2
Views: 68

Re: Molecularity

Yes I think a reaction that involves four molecules colliding simultaneously would be called a tetramolecular reaction. Given that termolecular reactions are uncommon due to three molecules having to collide simultaneously, tetramolecular reactions would be very rare.
by Joon Chang 2F
Fri Mar 08, 2019 11:12 pm
Forum: General Rate Laws
Topic: coefficient question
Replies: 2
Views: 63

Re: coefficient question

Yes for differential rate laws, the stoichiometric coefficients are written under 1.

by Joon Chang 2F
Fri Mar 08, 2019 10:41 pm
Forum: First Order Reactions
Topic: half-life for second order
Replies: 1
Views: 53

Re: half-life for second order


(At ) so

or
by Joon Chang 2F
Sun Mar 03, 2019 11:39 pm
Forum: General Rate Laws
Topic: m and n
Replies: 2
Views: 50

Re: m and n

Order of reaction is the power a concentration of something is raised to in the rate law (rate law is the equation for instantaneous reaction rate at certain concentration). Overall reaction order is the sum of the powers of the concentrations in the rate law. The variables "n" and "m...
by Joon Chang 2F
Wed Feb 27, 2019 10:43 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Question for Test 2
Replies: 4
Views: 91

Re: Question for Test 2

The equation is on the equation sheet so if you know how to use it you should be fine.
by Joon Chang 2F
Wed Feb 27, 2019 10:41 am
Forum: Balancing Redox Reactions
Topic: Balancing Hydrogen
Replies: 2
Views: 51

Re: Balancing Hydrogen

In acidic solution balance H by using H+. In basic solution balance H by adding H2O to the side that needs H and add OH to the other side.
by Joon Chang 2F
Sun Feb 24, 2019 10:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electron Flow Diagram
Replies: 1
Views: 42

Re: Electron Flow Diagram

Electrons produced by oxidation at the anode (-) travel to the cathode (+) where they cause reduction. The salt bridge is used to complete the circuit by allowing ions to flow.
by Joon Chang 2F
Sun Feb 24, 2019 10:33 pm
Forum: Balancing Redox Reactions
Topic: Salt Bridge
Replies: 5
Views: 67

Re: Salt Bridge

It allows ions to flow and maintains neutrality. Negative ions move to the anode side to help keep electrons flowing to the cathode side.
by Joon Chang 2F
Sun Feb 24, 2019 10:27 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: What is E?
Replies: 4
Views: 77

Re: What is E?

E is electromotive force or the potential difference in charge between two points. E(nought) is E under standard conditions (all solutes present at 1 molL^-1 and all gases at 1 bar). It can also be thought of as the measure of the electron-pulling power of a single electrode.
by Joon Chang 2F
Fri Feb 15, 2019 11:05 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: gibbs free energy
Replies: 10
Views: 150

Re: gibbs free energy

MadelineHlobik wrote:How do you calculate Gibbs free energy?

by Joon Chang 2F
Fri Feb 15, 2019 10:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy idea
Replies: 2
Views: 50

Re: Gibbs free energy idea

Gibbs free energy is the energy of a system that is free to do work at constant temperature and pressure.
by Joon Chang 2F
Wed Feb 13, 2019 4:23 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Isolated system
Replies: 10
Views: 321

Re: Isolated system

It is sealed and insulated so it is unable to exchange matter and energy with its surroundings.
by Joon Chang 2F
Sun Feb 10, 2019 9:54 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: q and delta H
Replies: 3
Views: 62

Re: q and delta H

q=H=nCpT at constant pressure
by Joon Chang 2F
Sun Feb 10, 2019 9:49 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: DeltaU=q+w
Replies: 5
Views: 80

Re: DeltaU=q+w

q and w are both path functions and both represent transfers of energy between systems and their surroundings.
by Joon Chang 2F
Sun Feb 10, 2019 9:29 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Term Differences (Heat, Enthalpy, Temperature, and Work)
Replies: 4
Views: 224

Re: Term Differences (Heat, Enthalpy, Temperature, and Work)

Heat is the transfer of energy as a result of a temperature difference. Enthalpy is the amount of heat released or absorbed at constant pressure. Temperature is a measure of the average heat or thermal energy of the molecules in a substance. Work is the process of achieving motion against an opposin...
by Joon Chang 2F
Sun Feb 03, 2019 10:48 pm
Forum: Calculating Work of Expansion
Topic: L*atm
Replies: 2
Views: 48

Re: L*atm

It is on the Constants and Formulas page on the website, but it was not on the Constants and Formulas page on test 1. Then again, several constants and formulas were omitted from test 1's formula page. Its required for many of the work problems, so I think it would be best to memorize it.
by Joon Chang 2F
Sun Feb 03, 2019 10:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Delta H and q
Replies: 3
Views: 73

Re: Delta H and q

H=q at constant pressure and with no nonexpansion work.
by Joon Chang 2F
Sun Feb 03, 2019 10:35 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: w=PdeltaV
Replies: 5
Views: 112

Re: w=PdeltaV

V=(Area of Base)(height)=A*D
by Joon Chang 2F
Fri Jan 25, 2019 10:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard enthalpy of formation
Replies: 2
Views: 50

Re: Standard enthalpy of formation

Standard enthalpy of formation is basically standard reaction enthalpy for one mole of substance formed from its standard states (most stable form).
by Joon Chang 2F
Fri Jan 25, 2019 10:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.3 6th Edition
Replies: 1
Views: 38

Re: 8.3 6th Edition

Work due to a change in volume is called expansion work. The equation is w= -P_{ex}\Delta V where P is pressure, and Delta V is change in volume. For part a) you are given the pressure and the dimensions to find the volume of the pump. Volume of cylinder is \pi r^{2}h . So you find the volume of the...
by Joon Chang 2F
Fri Jan 25, 2019 10:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method 2
Replies: 3
Views: 68

Re: Method 2

Bond enthalpies of diatomic molecules are able to be measured because they are only between two types of atoms, whereas enthalpies of other bonds are averages from different molecules. The bond enthalpy of the diatomic molecule H2 is +436 kJ. This enthalpy is able to be measured consistently because...
by Joon Chang 2F
Sun Jan 20, 2019 11:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.3 6th edition
Replies: 3
Views: 65

Re: 11.3 6th edition

I think they put 7N2 instead of 5N2 on mistake. However, you should always balance the equation first.
by Joon Chang 2F
Sun Jan 20, 2019 10:44 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changing partial pressure of components vs changing pressure of system
Replies: 2
Views: 76

Re: Changing partial pressure of components vs changing pressure of system

Changing the pressure of the reaction vessel will drive the reaction in the direction where the number of molecules will decrease. If pressure is increased by compression and there are more moles of gas on the left, the reaction will shift right.
by Joon Chang 2F
Sun Jan 20, 2019 10:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th edition 6A.19
Replies: 1
Views: 38

Re: 7th edition 6A.19

The concentration of H30+ is 3.1 mmol/L. I think that is where you are getting the calculation error.
by Joon Chang 2F
Sun Jan 13, 2019 3:25 pm
Forum: Ideal Gases
Topic: How much of Ch.5 are we expected to know?
Replies: 3
Views: 72

Re: How much of Ch.5 are we expected to know?

The outline just says know where the Ideal Gas Law can be used and how to solve for unknowns using it.
by Joon Chang 2F
Sun Jan 13, 2019 3:14 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Converting Qc to Qp [ENDORSED]
Replies: 3
Views: 80

Converting Qc to Qp [ENDORSED]

I know that Q is calculated in the same way as K, so does that mean conversions are done the same way using P=(conc.)RT?
by Joon Chang 2F
Sun Jan 13, 2019 3:07 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Result of Only Adding One of the Reactants
Replies: 4
Views: 50

Result of Only Adding One of the Reactants

Can someone explain what will happen if only one of the reactants is added to a chemical equation?
For example, in the equation 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g), if only NH3 is added to the equation, will equilibrium shift toward the products?
by Joon Chang 2F
Tue Dec 04, 2018 7:37 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Definitions of Acids and Bases
Replies: 1
Views: 166

Re: Definitions of Acids and Bases

Lewis Acid - Electron Acceptor, Brønsted acid - Proton Donor
Lewis Base - Electron Donor, Brønsted Base - Proton Acceptor
by Joon Chang 2F
Tue Dec 04, 2018 7:29 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH scale
Replies: 2
Views: 59

Re: pH scale

pH of 8-14 would have an H30+ concentration of (10^-8) mol/L to (10^-14) mol/L. This shows that larger pH numbers mean there are less H30+ due to the negative power of 10.
by Joon Chang 2F
Tue Dec 04, 2018 7:24 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: ph vs pOH
Replies: 5
Views: 106

Re: ph vs pOH

Sophia Ding 1D wrote:Just to clarify then, is the sum of pH + pOH always equal 14 then?
For all aqueous solutions at 25 degrees Celsius
by Joon Chang 2F
Tue Dec 04, 2018 7:13 pm
Forum: Naming
Topic: Oxidation Number
Replies: 2
Views: 64

Re: Oxidation Number

"Describe coordination compounds for the transition metal ions in terms of coordination number,
oxidation number, and types of ligands." This is under Outline 6 and it is in the syllabus so I think it could be on the finals.
by Joon Chang 2F
Tue Dec 04, 2018 7:10 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligand Binding Places
Replies: 2
Views: 83

Re: Ligand Binding Places

You can draw the lewis structure and determine what the structure is and where the lone pairs are located. See if the lone pairs are pointing in the same direction then determine if they can both bond to the cental metal ion.
by Joon Chang 2F
Tue Dec 04, 2018 6:56 pm
Forum: Bronsted Acids & Bases
Topic: acidity
Replies: 4
Views: 135

Re: acidity

Long A-H bonds are more acidic than shorter bonds because the longer bond is easier to break and easier to remove the H+.
by Joon Chang 2F
Sat Nov 24, 2018 8:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar/apolar
Replies: 1
Views: 44

Re: Polar/apolar

No CH4 is nonpolar because the dipole moments between C and H cancel out evenly.
by Joon Chang 2F
Sat Nov 24, 2018 8:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: What is VSPER
Replies: 14
Views: 108

Re: What is VSPER

VSEPR is the Valence Shell Electron Pair Repulsion theory and it basically is a way to describe molecular shapes using rules of electron repulsion. Memorizing the rules will certainly help in drawing and naming the structures.
by Joon Chang 2F
Sat Nov 24, 2018 8:35 pm
Forum: Hybridization
Topic: Hybridization 4.75
Replies: 2
Views: 63

Re: Hybridization 4.75

The compound is CH4O. The bond angles about the carbon and oxygen are 109.5 degrees because the carbon, 3 hydrogens, and oxygen form a tetrahedral shape with carbon in the center. The hybridization of the carbon and oxygen atoms are both sp3 because they each have 4 regions of electron density. The ...
by Joon Chang 2F
Sat Nov 24, 2018 8:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape 4.45
Replies: 3
Views: 55

Re: Molecular Shape 4.45

Formaldehyde is trigonal planar so it has angles of 120 degrees. It has a hybridization of sp2 and has 3 sigma and 1 pi bonds.
by Joon Chang 2F
Sat Nov 24, 2018 8:15 pm
Forum: Hybridization
Topic: Sigma/Pi Bonds
Replies: 5
Views: 83

Re: Sigma/Pi Bonds

First draw the Lewis structure. Then determine what bonds there are according to the types of bonds. A single bond is a sigma, double bond has one sigma and one pi, triple bond has one sigma and two pi.
by Joon Chang 2F
Sun Nov 18, 2018 5:32 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge of Central Atom
Replies: 4
Views: 282

Re: Formal Charge of Central Atom

Yes the formal charge for Cl in ClO2+ should be +1 because it has a lone pair.
by Joon Chang 2F
Sun Nov 18, 2018 5:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.3 6th edition
Replies: 2
Views: 64

Re: 4.3 6th edition

First draw the Lewis Structures for the molecules. Then determine how many areas of electron density are on the central atom. Choose the shape that pertains to that number of areas of electron density and draw.
by Joon Chang 2F
Sun Nov 18, 2018 5:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.1 6th edition
Replies: 1
Views: 33

Re: 4.1 6th edition

a) Must have lone pairs of electrons because in order to have the bent shape, there must be one or more lone pairs contributing to the repulsion of the other atoms.
b) May have lone pairs. The linear shape could have zero lone pairs or multiple lone pairs all in the same axial plane.
by Joon Chang 2F
Sat Nov 10, 2018 9:05 pm
Forum: Bond Lengths & Energies
Topic: 2D 15)
Replies: 3
Views: 119

Re: 2D 15)

A) CF4 would have the strongest CX bond. Larger atoms mean there will be a larger distance between the atoms (longer bond length) which means the bonds will be weaker. The size of the atoms increases as you go from CF4 to CCl4 and CBr4, therefore the ones with the smallest size, CF4, would have the ...
by Joon Chang 2F
Sat Nov 10, 2018 8:43 pm
Forum: Student Social/Study Group
Topic: Last Friday's Lecture
Replies: 4
Views: 162

Re: Last Friday's Lecture

I believe Sapling Learning is the online practice problem system that has practice problems with solutions. It was included in the package for the textbook at the UCLA bookstore.
by Joon Chang 2F
Sat Nov 10, 2018 8:08 pm
Forum: SI Units, Unit Conversions
Topic: Angstrom and SI Units
Replies: 2
Views: 346

Re: Angstrom and SI Units

No it is not an SI prefix. The closest SI prefix is the nanometer (10^-9m).
by Joon Chang 2F
Sat Oct 27, 2018 10:02 pm
Forum: Lewis Structures
Topic: Periodic Table Trends
Replies: 5
Views: 114

Re: Periodic Table Trends

Electron Affinity is the energy released when an electron is added to a gas phase atom. A positive electron affinity means energy is released when an electron is added and a negative electron affinity means energy is needed to add an electron. Electronegativity is the electron pulling-power of an at...
by Joon Chang 2F
Sat Oct 27, 2018 9:51 pm
Forum: Trends in The Periodic Table
Topic: P-block elements
Replies: 3
Views: 130

Re: P-block elements

In the p-block, the metals form cations by losing their valence electrons and the nonmetals form anions by gaining enough valence electrons to fill their p-orbital.
by Joon Chang 2F
Sat Oct 27, 2018 9:40 pm
Forum: Lewis Structures
Topic: Periodic Table Trends
Replies: 5
Views: 114

Re: Periodic Table Trends

The different trends are atomic radius (Increase down a group, decrease across period), ionic radius (increase down a group, decrease across period), ionization energy (decrease down a group, increase across a period), and electron affinity (generally highest for elements in the top right of periodi...
by Joon Chang 2F
Fri Oct 19, 2018 9:42 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum number M [ENDORSED]
Replies: 7
Views: 209

Re: Quantum number M [ENDORSED]

Can anyone clarify the meaning/concept of quantum number m? Quantum number m s is the spin magnetic quantum number . It represents the spin state of the electron, which can be thought of as the electron spinning either clockwise or counterclockwise. It basically indicates what direction the electro...
by Joon Chang 2F
Fri Oct 19, 2018 8:55 pm
Forum: DeBroglie Equation
Topic: DeBroglie wavelike properties question
Replies: 4
Views: 121

Re: DeBroglie wavelike properties question

According to the lecture, all moving particles with momentum have wavelike properties, but the wavelike properties are only noticed for objects with small mass and high velocity. Professor Lavelle also stated a baseball has wavelike properties but the wavelength is so small it is smaller than what i...
by Joon Chang 2F
Fri Oct 19, 2018 8:30 pm
Forum: *Black Body Radiation
Topic: Test
Replies: 9
Views: 502

Re: Test

The test is on Outline 2: The Quantum World. Black body radiation is not one of the topics listed on Outline 2 so I believe it will not be on the test.
by Joon Chang 2F
Fri Oct 12, 2018 12:01 am
Forum: Balancing Chemical Reactions
Topic: L.5 Part B Sixth Edition [ENDORSED]
Replies: 5
Views: 196

Re: L.5 Part B Sixth Edition [ENDORSED]

The answer is in the book is in g. Other than your final step of converting g to kg, your steps are correct. 3.500x10^3 kg * (1000g/1kg) = 3.500x10^6 g 3.500x10^6 g * (1mol Al/26.982g) = 129716.107 mol Al 129716.107 mol Al *(5mol Al2O3 / 10mol Al) = 64858.054 mol Al2O3 64858.054 mol Al2O3 * (101.961...
by Joon Chang 2F
Thu Oct 11, 2018 11:46 pm
Forum: Properties of Electrons
Topic: HW problem Focus 1 B5 7th edition
Replies: 2
Views: 61

Re: HW problem Focus 1 B5 7th edition

1keV=1,000 eV = 1.60218x10^-19 J. Use this to convert the units and solve using .
by Joon Chang 2F
Thu Oct 11, 2018 11:31 pm
Forum: Properties of Light
Topic: Kinetic energy equation
Replies: 4
Views: 61

Re: Kinetic energy equation

The mass of an electron is 9.10938 × 10^-31 kilograms. This will probably be given on the constants page of the tests.
by Joon Chang 2F
Fri Oct 05, 2018 11:01 am
Forum: Significant Figures
Topic: Significant Figures for E.21 (b)
Replies: 4
Views: 109

Re: Significant Figures for E.21 (b)

I was confused about this problem as well. I just left the answer with the number of significant figures given in the problem.
by Joon Chang 2F
Fri Oct 05, 2018 10:42 am
Forum: Significant Figures
Topic: Sig Figs
Replies: 5
Views: 111

Re: Sig Figs

Ya just do the calculations first and determine sig figs at the end using the fewest amount of "given" sig figs.
by Joon Chang 2F
Fri Oct 05, 2018 10:39 am
Forum: Limiting Reactant Calculations
Topic: Compensating for Mole Ratios in Limiting Reactants
Replies: 3
Views: 107

Re: Compensating for Mole Ratios in Limiting Reactants

First you find molar mass of both reactants and calculate the number of moles of both reactants using this molar mass. Molar Mass of NH3= 17.031gmol-1. Molar Mass of O2=31.998gmol-1. Moles of NH3= 21.4g/17.031gmol-1 = 1.2565mol NH3. Moles of O2= 42.5g/31.998gmol-1 = 1.3282mol O2. Now you use the bal...

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