## Search found 99 matches

Sat Mar 14, 2020 7:10 pm
Forum: Calculating Work of Expansion
Topic: work
Replies: 3
Views: 80

### Re: work

When something is reversible, it is also isothermal.
Sat Mar 14, 2020 7:07 pm
Forum: Balancing Redox Reactions
Topic: balancing h and o
Replies: 7
Views: 169

### Re: balancing h and o

When balancing in basic solution don't forget to use OH^-
Sat Mar 14, 2020 7:04 pm
Forum: *Nucleophiles
Topic: FInal
Replies: 6
Views: 252

### Re: FInal

I would go over the outlines that Lavelle has posted on his website, and make sure you understand each bullet point.
Sat Mar 14, 2020 7:03 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: order of reaction
Replies: 6
Views: 128

### Re: order of reaction

This video is pretty good at explaining the concepts.
Sat Mar 14, 2020 10:07 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Lyndon Review: 1D
Replies: 5
Views: 140

### Lyndon Review: 1D

Hi for problem 1D in the review, will Ecell decrease or stay the same?

true/false Ecell will increase if the size of the anode metal is increased.
Sun Mar 08, 2020 9:21 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Downs Process
Replies: 4
Views: 111

### Re: Downs Process

No, you only need to know what is on the Electrochemistry outline.
https://lavelle.chem.ucla.edu/wp-conten ... rochem.pdf
Sun Mar 08, 2020 9:19 pm
Forum: General Science Questions
Topic: Slope
Replies: 4
Views: 109

### Re: Slope

Depending on what order your reaction is, your rate law will be different. For zero-order and first-order reactions, the slope is equal to -k, but for second-order reactions, the slope is just k. The trick is just distinguishing which value is k when using a rate law. How can you tell the differenc...
Sun Mar 08, 2020 9:06 pm
Forum: General Rate Laws
Topic: units
Replies: 12
Views: 117

### Re: units

K = equilibrium constant has no units
k = rate constant units fluctuate between orders

0 order units: M/s, M/min, M/hr, etc.
1st order units: s-1, min-1, hr-1, etc.
2nd order units: M-1s-1, M-1min-1, M-1hr-1, etc.
Sun Mar 08, 2020 9:00 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Exothermic vs. Endothermic
Replies: 14
Views: 156

### Re: Exothermic vs. Endothermic

This is a good video explaining exothermic vs endothermic reactions.
Sun Mar 08, 2020 8:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum
Replies: 10
Views: 98

### Re: Platinum

Juliet Stephenson 4E wrote:What defines a solid conductor?

A solid conductor is a metal in solid state.
Sun Mar 08, 2020 8:38 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: how?
Replies: 3
Views: 58

### Re: how?

Are you referring to n = moles and k = Rate?
Sat Mar 07, 2020 5:21 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: the intermediate in a reaction
Replies: 10
Views: 183

### Re: the intermediate in a reaction

Intermediates are produced in one step and consumed in a later step, so they do not appear in the overall reaction equation or overall rate law
Sat Mar 07, 2020 5:19 pm
Forum: General Science Questions
Replies: 23
Views: 594

TimVintsDis4L wrote:I wouldn't be surprised if we get our tests back on Wednesday as the Ta's might have to work on the final so they get the tests over with first.

Do the TAs make our final or Dr. Lavelle?
Sat Mar 07, 2020 5:14 pm
Forum: General Science Questions
Topic: Reducing Math Errors
Replies: 7
Views: 178

### Re: Reducing Math Errors

Whenever you do your homework, always use the same instruments (pen and calculator) that you plan to use on the test. It'll eventually become muscle memory.
Sat Mar 07, 2020 5:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: galvanic cells
Replies: 8
Views: 145

### Re: galvanic cells

You want the value to be positive because that means the reaction is spontaneous.
Sun Feb 23, 2020 9:08 pm
Forum: Balancing Redox Reactions
Topic: Hydroxide and H+
Replies: 6
Views: 69

### Re: Hydroxide and H+

In neutral solutions, you should use H2O to balance the hydrogens.
Sun Feb 23, 2020 9:04 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Equations
Replies: 7
Views: 93

### Re: Balancing Redox Equations

I remember with the acronym OIL RIG.
OIL: oxidation is losing elections
RIG: reduction is gaining elections
Sun Feb 23, 2020 8:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: l vs ll
Replies: 5
Views: 53

### Re: l vs ll

A single line represents interface between phases in contact with each other including a porous wall. A double line represents a salt bridge.
Sun Feb 23, 2020 8:49 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2
Replies: 5
Views: 92

### Re: Test 2

It will be everything left from thermochemistry that we did not cover on the midterm and electrochemistry.
Sun Feb 23, 2020 8:39 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Spontaneity
Replies: 7
Views: 134

### Re: Spontaneity

Spontaneous processes don't necessarily happen quickly, it just means that over time there is a tendency for that reaction to occur. The equation that relates spontaneity to the cell potential difference is deltaGknot = -nFEknot. This makes sense, because the more positive the E value of cell poten...
Sun Feb 23, 2020 8:35 pm
Forum: Balancing Redox Reactions
Topic: Half reactions
Replies: 17
Views: 249

### Re: Half reactions

Are you referring to when you have to balance the half reactions?
Sun Feb 23, 2020 8:34 pm
Forum: Balancing Redox Reactions
Topic: Determining direction of flow
Replies: 15
Views: 224

### Re: Determining direction of flow

The direction of flow is always from the anode to the cathode.
Sun Feb 23, 2020 8:30 pm
Forum: Balancing Redox Reactions
Topic: Polyatomic Ions
Replies: 4
Views: 41

### Polyatomic Ions

Are there any polyatomic ions that we should memorize or will we be provided with the charges of the ions?
Sun Feb 23, 2020 8:24 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2
Replies: 15
Views: 268

### Re: Test 2

Angela Wu-2H wrote:Will test 2's difficulty be more like test 1's difficulty or the midterm's difficulty?

I heard that in the past quarters, test 2 has been harder than test 1.
Tue Feb 11, 2020 11:52 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4.7
Replies: 2
Views: 46

### Re: 4.7

You need to first write out your balanced equation. The equation that you're going to want to use is w=-PdeltaV. You know that PdeltaV=deltanRT (ideal gas law).
From there, you can find that the delta n of the gaseous products is (6-7.5=1.5), and then you just plug in the other values.
Mon Feb 10, 2020 12:06 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4D.3
Replies: 2
Views: 39

### 4D.3

The reaction of 1.40 g of carbon monoxide with excess water vapor to produce carbon dioxide and hydrogen gases in a bomb calorimeter causes the temperature of the calorimeter assembly to rise from 22.113 8 C to 22.799 8 C. The calorimeter assembly is known to have a total heat capacity (calorimeter ...
Sun Feb 09, 2020 8:44 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Intensive vs. Extensive
Replies: 15
Views: 345

### Re: Intensive vs. Extensive

Intensive properties do not depend on the quantity of matter. Examples include density, state of matter, and temperature. Extensive properties do depend on sample size. Examples include volume, mass, and size
Sun Feb 09, 2020 8:37 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal and Reversible
Replies: 6
Views: 44

### Isothermal and Reversible

When a process is reversible, is it also isothermal?
Sun Feb 09, 2020 8:31 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: State Functions
Replies: 5
Views: 71

### State Functions

Hi, I vaguely remember in Lyndon's review session about an acronym to help remember all the state functions. Can anyone refresh my memory?
Sun Feb 09, 2020 8:27 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: spontaneity
Replies: 18
Views: 169

### Re: spontaneity

A reaction is spontaneous if delta G is negative and is not spontaneous if delta G is positive.
Sun Feb 02, 2020 11:25 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Types of Systems
Replies: 7
Views: 158

### Re: Types of Systems

Can someone please give an example of an isolated system that is not a bomb calorimeter or a hydroflask?
Sun Feb 02, 2020 11:23 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: degeneracy
Replies: 7
Views: 55

### Re: degeneracy

Degeneracy is defined as having two or more quantum states in a quantized energy level. For example, 2p would have three degenerate orbitals, 2px 2py 2pz, because they are in the same n=2 energy level.
Sun Feb 02, 2020 11:20 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Forming bonds
Replies: 8
Views: 70

### Re: Forming bonds

When bonds form, you have an exothermic process.
When bonds break, you have an endothermic process.
Sun Feb 02, 2020 11:12 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Combustion
Replies: 5
Views: 43

### Re: Combustion

Water boils at 100 degrees Celsius also known as 373.15 degrees Kelvin
Sun Feb 02, 2020 11:10 pm
Forum: Calculating Work of Expansion
Topic: Integrals
Replies: 4
Views: 41

### Re: Integrals

I believe we will need to be able to calculate an integral because the pre-requisites to the class include math 31b or ls 30b.
Sun Feb 02, 2020 11:04 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: standard enthalpy of formation
Replies: 1
Views: 29

### Re: standard enthalpy of formation

This is because it takes no energy to form a naturally-occurring compound.
Sun Feb 02, 2020 11:03 pm
Forum: Calculating Work of Expansion
Topic: temperature
Replies: 7
Views: 66

### Re: temperature

Kelvin = Celsius + 273.15

Celsius = Kelvin - 273.15

Because the difference between Celsius and Kelvin is addition/subtration; the difference/sum will always be the same.
Sun Feb 02, 2020 11:01 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneous vs. Energetically Favorable
Replies: 3
Views: 24

### Spontaneous vs. Energetically Favorable

What is the difference between “spontaneous” and “energetically favorable”?
Sun Feb 02, 2020 10:53 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated system
Replies: 10
Views: 176

### Re: Isolated system

Wait, but I assumed that heat would still technically be able to escape from a hydroflask to the surroundings. Are there any other examples that would be an isolated system?
Sun Feb 02, 2020 10:49 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter
Replies: 5
Views: 55

### Re: Calorimeter

Can someone please explain what Dr. Lavelle was showing through his diagrams of Calorimeters?
Mon Jan 20, 2020 12:51 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw
Replies: 2
Views: 22

### Re: Kw

Ka × Kb = Kw = 10-14 at 25 °C
Mon Jan 20, 2020 12:48 am
Forum: Administrative Questions and Class Announcements
Topic: TeST 1
Replies: 5
Views: 62

### Re: TeST 1

Mon Jan 20, 2020 12:46 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: q vs k
Replies: 9
Views: 51

### Re: q vs k

Q is the reaction quotient and expresses the relative ratio of products to reactants at a given instant. On the other hand, K is the equilibrium constant and is used to calculate the final concentrations at equilibrium for a reaction using an ICE table. If Q and K equal each other, the reaction is a...
Mon Jan 13, 2020 4:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solid and Liquid
Replies: 5
Views: 54

### Re: Solid and Liquid

Solids and liquids are not included in the K expression as they do not change their concentrations in a reaction as they are pure substances. Essentially, their value is 1 resulting in the K expression only including aqueous solutions. As well as gases!! Wait, I thought gases were included in the K...
Mon Jan 13, 2020 4:04 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: "Quick way" part in Lecture
Replies: 7
Views: 80

### Re: "Quick way" part in Lecture

The quick way is to count the number of moles on each side of the reaction equation and compare which side has the greater number of moles to determine which way the reaction will favor. N2(g) + 3H2(g) <=> 2NH3(g) Reactants: 1 mol of N2 + 3 mols of H2 Products: 2 mols of NH3 4 mols of reactant to 2 ...
Fri Jan 10, 2020 3:49 pm
Forum: Ideal Gases
Topic: R in PV=nRT
Replies: 34
Views: 744

### Re: R in PV=nRT

Dr. Lavelle's website also provides the constants and formulas that we will receive for test and exams.

https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf
Fri Jan 10, 2020 3:45 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: HW 5J.5
Replies: 8
Views: 61

### Re: HW 5J.5

Only gaseous and aqueous forms of reactants and products are used in an equilibrium constant expression.
Fri Jan 10, 2020 3:41 pm
Forum: Student Social/Study Group
Topic: Chemistry Community Confessions
Replies: 2
Views: 71

### Re: Chemistry Community Confessions

This would be fun idea though!
Fri Jan 10, 2020 3:27 pm
Forum: Ideal Gases
Topic: Chatelier’s Principle
Replies: 8
Views: 76

### Re: Chatelier’s Principle

I believe Le Chatelier’s principle is found in section 5J on page 426.
Fri Jan 10, 2020 3:21 pm
Forum: Student Social/Study Group
Topic: Homework for Week 1
Replies: 6
Views: 81

### Re: Homework for Week 1

I believe chemistry community posts are due by 11:59 pm on Sunday.
Mon Dec 09, 2019 9:37 am
Forum: Bronsted Acids & Bases
Topic: amphoteric
Replies: 7
Views: 241

### Re: amphoteric

All amphiprotic species must be amphoteric, but the converse is not true.
Mon Dec 09, 2019 9:35 am
Forum: Student Social/Study Group
Topic: Practice Final
Replies: 17
Views: 611

### Re: Practice Final

Where have people been able to find old tests?
Mon Dec 09, 2019 9:33 am
Forum: Sigma & Pi Bonds
Topic: Carbon's hybridization
Replies: 3
Views: 296

### Re: Carbon's hybridization

Are the numbers before hybridization just the period the element is in?
Sat Dec 07, 2019 2:33 pm
Forum: Lewis Acids & Bases
Topic: 6A.15
Replies: 2
Views: 64

### 6A.15

Can someone please explain how I can figure out if something is a Lewis acid or base? And how do I know what the product will be? Draw the Lewis structure or symbol of each reactant, identify the Lewis acid and the Lewis base, and then draw the Lewis structure of the product (a complex) for the foll...
Sun Dec 01, 2019 12:31 pm
Forum: *Stereochemistry
Topic: Lecture on 11/22 (Friday) & 11/27 (Wednesday)
Replies: 1
Views: 100

### Re: Lecture on 11/22 (Friday) & 11/27 (Wednesday)

The lecture on 11/22 was on Naming Coordinate Compounds and Acids and Bases.
The lecture on 11/27 was a continuation of Acids and Bases (mainly how to find pH), Relative Acidity, and pKa.
Sun Dec 01, 2019 12:24 pm
Forum: Lewis Acids & Bases
Topic: Lewis vs. Bronsted
Replies: 3
Views: 37

### Re: Lewis vs. Bronsted

I believe you should be able to know what the difference is between the two for the exam.
Sun Dec 01, 2019 12:14 pm
Forum: Bronsted Acids & Bases
Topic: 6A.11
Replies: 2
Views: 39

### Re: 6A.11

See Attachment
Sun Dec 01, 2019 12:10 pm
Forum: Lewis Acids & Bases
Topic: bronsted/lewis
Replies: 1
Views: 39

### Re: bronsted/lewis

All Bronsted-Lowry bases are also Lewis bases, but the reverse is not true. Same for Bronsted-Lowry acids and Lewis acids. A Lewis acid is anything that accepts a pair of electrons, while a Bronsted acid accepts pairs of electrons only from hydrogen. A Lewis base is anything that donates a pair of e...
Sun Dec 01, 2019 12:04 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: drawing
Replies: 1
Views: 46

### Re: drawing

Basically the same steps as a Lewis structure, but remember that the transition metals do not always follow the octet rule. You should pay attention to what atoms are bonded to the transition metal/Lewis acid and adding lone pairs and determining the formal charge is helpful.
Tue Nov 26, 2019 1:17 pm
Forum: Lewis Acids & Bases
Topic: Lewis vs Bronsted Acids and Bases
Replies: 3
Views: 33

### Lewis vs Bronsted Acids and Bases

Can someone please clarify the difference between Lewis Acids and Bases and Bronsted Acids and Bases?
Tue Nov 26, 2019 1:14 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Exam
Replies: 5
Views: 85

### Re: Final Exam

Does anyone know if there will be a curve on the final?
Tue Nov 26, 2019 1:13 pm
Forum: Administrative Questions and Class Announcements
Topic: finals
Replies: 5
Views: 87

### Re: finals

Will there be a curve on the final?
Tue Nov 26, 2019 1:04 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 9 Homework
Replies: 2
Views: 48

### Re: Week 9 Homework

Our hw 9 is due with our hw 10 so you should email your TA to find out the exact details.
Fri Nov 22, 2019 12:07 am
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.5
Replies: 5
Views: 82

### 2E.5

2E.5 (a) What is the shape of a ClO2+ ion?

How can you tell if something is bent or trigonal planar? Thanks!
Sun Nov 17, 2019 7:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar and Nonpolar
Replies: 6
Views: 210

### Polar and Nonpolar

2E.25 Draw the Lewis structure and predict whether each of the following molecules is polar or nonpolar: (a) CH2Cl2; (b) CCl4; (c) CS2; (d) SF4.

How can I tell if molecules are polar or nonpolar?
Sun Nov 17, 2019 7:44 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 2
Replies: 19
Views: 331

### Re: Test 2

This has probably already been said, but can someone list all the topics that will be covered on this upcoming test
Sun Nov 17, 2019 7:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2F.17
Replies: 1
Views: 42

### Re: 2F.17

First, I would draw out the lewis structure which should have the carbon in the middle with single bonds to two hydrogens and a double bond to an oxygen with two lone pairs.

Carbon and Oxygen are both sp2 hybridized

The H-C-O bond angle is 120 degrees

3 sigma bonds and 1 pi bond
Sun Nov 17, 2019 6:55 pm
Forum: Hybridization
Topic: 2.57
Replies: 1
Views: 39

### Re: 2.57

That's what I got!
Sun Nov 17, 2019 6:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.25
Replies: 3
Views: 51

### Re: 2E.25

Although CH2Cl2 is symmetrical, the differing polarities of the C–H and C–Cl bonds means the effect of the polar bonds is not cancelled, so the molecule is polar

SF4 has 4 bonds with one lone pair which makes it polar.
Sun Nov 17, 2019 6:41 pm
Forum: Electronegativity
Topic: Electron affinity
Replies: 2
Views: 144

### Re: Electron affinity

Electronegativity is the tendency of an atom to attract electrons, while electron affinity is the amount of energy released when an electron is added to a neutral atom.
Sun Nov 17, 2019 6:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2F.17
Replies: 2
Views: 45

### Re: 2F.17

First, I would draw out the lewis structure which should have the carbon in the middle with single bonds to two hydrogens and a double bond to an oxygen with two lone pairs.

Carbon and Oxygen are both sp2 hybridized

The H-C-O bond angle is 120 degrees

3 sigma bonds and 1 pi bond
Sun Nov 17, 2019 6:31 pm
Forum: Hybridization
Topic: Sigma and Pi bonds
Replies: 2
Views: 34

### Re: Sigma and Pi bonds

A sigma bond is a bond formed by the overlap of orbitals in an end-to-end fashion, with the electron density concentrated between the nuclei of the bonding atoms. A pi bond is a bond formed by the overlap of orbitals in a side-by-side fashion with the electron density concentrated above and below th...
Mon Nov 04, 2019 4:12 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Electron Configuration
Replies: 5
Views: 105

### Midterm Electron Configuration

On the midterm, will we need to find the electron configurations of elements past the f-blocks?
Sun Nov 03, 2019 9:24 pm
Forum: Resonance Structures
Topic: 2B.15
Replies: 2
Views: 58

### 2B.15

2B.15 Draw the Lewis structures that contribute to the resonance hybrid of nitryl chloride, ClNO2 (N is the central atom).
Sun Nov 03, 2019 9:22 pm
Forum: Octet Exceptions
Topic: 2C.11
Replies: 1
Views: 44

### 2C.11

2C.11 Draw the Lewis structure and state the number of lone pairs on xenon, the central atom of each of the following molecules:
(a) XeOF2; (b) XeF4; (c) XeOF4.
Sun Nov 03, 2019 9:21 pm
Forum: Octet Exceptions
Topic: 2C.17
Replies: 1
Views: 46

### 2C.17

2C.17 Select from each of the following pairs of Lewis structures the one that is likely to make the dominant contribution to a resonance hybrid. Explain your selection. (pg. 94)

Can someone explain resonance hybrids and this problem?
Sun Nov 03, 2019 9:10 pm
Forum: Hybridization
Topic: Noble Configuration vs. Full
Replies: 7
Views: 93

### Re: Noble Configuration vs. Full

I believe that you can write the full configuration or the noble gas configuration. Either works
Sun Nov 03, 2019 9:09 pm
Forum: Electronegativity
Topic: Trends of the Periodic Table
Replies: 3
Views: 83

### Re: Trends of the Periodic Table

I believe they are atomic radius, ionization energy, electronegativity, and electron affinity.
Sun Oct 27, 2019 1:00 am
Forum: Sigma & Pi Bonds
Topic: Single vs. Double bonds
Replies: 15
Views: 272

### Single vs. Double bonds

Why are single bonds longer than double bonds?
Sun Oct 27, 2019 12:59 am
Forum: Formal Charge and Oxidation Numbers
Topic: 2B. 23
Replies: 2
Views: 69

### 2B. 23

2B.23 Determine the formal charge on each atom in the following molecules. Identify the structure of lower energy in each pair. (The pictures are in the textbook on page 87)

Can someone please explain formal charges to me?
Sun Oct 27, 2019 12:56 am
Forum: Ionic & Covalent Bonds
Topic: 2A.23
Replies: 5
Views: 67

### 2A.23

On the basis of the expected charges on the monatomic ions, give the chemical formula of each of the following compounds: (a) magnesium arsenide; (b) indium(III) sulfide; (c) aluminum hydride; (d) hydrogen telluride; (e) bismuth(III) fluoride.
Sun Oct 27, 2019 12:52 am
Forum: Properties of Light
Topic: Rydberg Equation
Replies: 3
Views: 69

### Rydberg Equation

Can someone please explain the constants in the Rydberg Equation and when I would use it?
Sun Oct 27, 2019 12:47 am
Forum: Properties of Light
Topic: Light vs. Particles
Replies: 2
Views: 64

### Light vs. Particles

Can someone please clarify which equations should be used for light and which ones should be used for particles?
Sun Oct 20, 2019 3:18 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: 1D. 25
Replies: 4
Views: 51

### 1D. 25

1D.25 Which of the following subshells cannot exist in an atom: (a) 2d; (b) 4d; (c) 4g; (d) 6f?

Can someone please explain this problem to me?
Sun Oct 20, 2019 3:11 pm
Forum: Balancing Chemical Reactions
Topic: Balancing equations.
Replies: 35
Views: 637

### Re: Balancing equations.

Balance metals, then non-metals, and finally oxygen.

Sun Oct 20, 2019 3:07 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Period Trends
Replies: 2
Views: 43

### Re: Period Trends

Yep!
Sun Oct 20, 2019 2:47 pm
Forum: DeBroglie Equation
Topic: Module Question 35
Replies: 1
Views: 52

### Re: Module Question 35

First use the De Broglie equation:
λ = h/mv, where λ is wavelength, h is Planck's constant, m is the mass of a particle (g), moving at a velocity v (m/s)

Change and check units
125km/hr = 34.72m/s

λ = (6.6261 x 10^-34 m^2 kg/s)/ (275kg x 34.72m/s)
λ = 6.94 x 10-38 m
Sat Oct 19, 2019 2:02 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Balmer vs. Lyman Series
Replies: 4
Views: 68

### Balmer vs. Lyman Series

Can anyone help clarify what the differences between the Balmer and Lyman series and what they are used for?
Sun Oct 13, 2019 1:54 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: D.19
Replies: 2
Views: 65

### D.19

D.19 How many orbitals are present in the (a) 4p-subshell; (b) 3d-subshell; (c) 1s-subshell; (d) 4f-subshell of an atom?

Can someone also explain why 3d is filled before 4s?
Sun Oct 13, 2019 1:44 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: First Test Result
Replies: 5
Views: 189

### Re: First Test Result

Following!
Sun Oct 13, 2019 1:01 pm
Forum: Photoelectric Effect
Topic: 1B.25
Replies: 2
Views: 75

### Re: 1B.25

You should use Heisenberg's Indeterminacy Equation, delta p x delta x >= h/(4pi) First, change the diameter from 350pm to meters, 3.50 x 10^-10 m. Then plug in all known values into the Heisenberg equation to solve for Delta p. delta p = 6.63x10^-34/ (4pi x 3.50x10^-10m) Then, just use delta p = del...
Sun Oct 13, 2019 12:55 pm
Forum: Properties of Light
Topic: 1A.11
Replies: 3
Views: 109

### Re: 1A.11

Can someone also explain why for the Lyman series the lowest energy level is n=1; for the Balmer series the lowest n=2; for the Paschen series it's n=3; and for the Brackett series n=4?
Wed Oct 09, 2019 2:23 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Test 1 [ENDORSED]
Replies: 107
Views: 5286

### Re: Test 1[ENDORSED]

Are there any specific equations we need to memorize for future tests? Or are equation sheets usually provided
Thu Oct 03, 2019 3:39 pm
Forum: Significant Figures
Topic: Sig Figs and Rounding
Replies: 4
Views: 119

### Re: Sig Figs and Rounding

Round significant figures at the end
Thu Oct 03, 2019 3:38 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical Homework Problem Help
Replies: 1
Views: 61

### Re: Empirical Homework Problem Help

996.08g = 339.20g Co + 656.88g F Find the mass % of each of the elements in the compound (339.20g Co) / (996.08g total) = 34.05% Cobalt (656.88g F) / (996.08g total) = 65.95% Fluorine Convert to moles (34.05g Co) / (58.93g / mol Co) = 0.5778 mol Co (65.98g F) / (19g / mol F) = 3.473 mol F Divide by ...
Thu Oct 03, 2019 3:31 pm
Forum: SI Units, Unit Conversions
Topic: Discussion Credit
Replies: 7
Views: 148

### Re: Discussion Credit

I think it's 5 times a week, and you can choose whether to pose or answer questions.
Thu Oct 03, 2019 3:28 pm
Forum: Balancing Chemical Reactions
Topic: Net Moles
Replies: 2
Views: 82

### Re: Net Moles

All the reactants and products are in gas phase, thus the net number of moles of gas produced should be the sum of coefficient of the product - the sum of coefficient of the reactants.
36-30=6
Thu Oct 03, 2019 3:23 pm
Forum: Limiting Reactant Calculations
Topic: Fundamentals M15
Replies: 3
Views: 63

### Re: Fundamentals M15

(a) First balance the chemical equation: Al + Cl2 -> AlCl3. It should look like this once it's balanced: 2Al + 3Cl2 -> 2AlCl3 (b)You need to find to the limiting reactant so you should convert the masses of the reactants to moles and then compare the ratios of the stoichiometric coefficients to thos...