Search found 61 matches

by josephyim1L
Tue Mar 12, 2019 11:46 pm
Forum: General Rate Laws
Topic: rate laws and graphs
Replies: 3
Views: 57

rate laws and graphs

Is it important that we understand/are able to implement graphs of rate laws and integrated rate laws for solving problems?
by josephyim1L
Tue Mar 12, 2019 11:44 pm
Forum: General Rate Laws
Topic: reaction rate(s)?
Replies: 4
Views: 185

reaction rate(s)?

what is the difference between a reaction rate and rate law?
by josephyim1L
Tue Mar 12, 2019 11:43 pm
Forum: General Rate Laws
Topic: reaction rate vs. unique reaction rate
Replies: 3
Views: 58

reaction rate vs. unique reaction rate

What is the difference between reaction rate (change in reaction/change in time) vs. unique reaction rate?
by josephyim1L
Thu Mar 07, 2019 11:01 pm
Forum: General Rate Laws
Topic: 15.5
Replies: 2
Views: 82

15.5

Can someone explain: 15.5 Ethene is a minor but important component of natural gas, and its combustion has been thoroughly studied. At a certain temperature and pressure, the unique rate of the combustion reaction C2H4(g) + 3 O2(g) 2 CO2(g) 2 H2O(g) is 0.44 mol/L/s. (a) What is the rate at which oxy...
by josephyim1L
Thu Mar 07, 2019 11:00 pm
Forum: General Rate Laws
Topic: 15.3
Replies: 3
Views: 69

15.3

Can someone explain this to me: 15.3 In 20. s, the concentration of nitrogen dioxide, NO2, decreases from 450 mmol/L to 320 mmol/L in the reaction 2 NO2(g) 2 NO(g) O2(g). (a) Determine the rate of reaction of NO2. (b) Determine the rate of formation of O2. (c) What is the unique rate of the reaction?
by josephyim1L
Thu Mar 07, 2019 10:59 pm
Forum: General Rate Laws
Topic: 15.1
Replies: 3
Views: 62

15.1

Can someone explain: 15.1 Complete the following statements relating to the production of ammonia by the Haber process, for which the overall reaction is N2(g) + 3 H2(g) S 2 NH3(g). (a) The rate of consumption of N2 is ________________ times the rate of consumption of H2. (b) The rate of formation o...
by josephyim1L
Thu Feb 28, 2019 2:37 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.91
Replies: 1
Views: 38

14.91

Can someone explain 14.91 in the 6th edition to me please:

14.91 A voltaic cell functions only when the electrical circuit
is complete. In the external circuit the current is carried by the flow of electrons through a metal wire. Explain how the current is carried through the cell itself.
by josephyim1L
Thu Feb 28, 2019 2:35 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: question
Replies: 2
Views: 53

question

Is a porous disc the same as a salt bridge?
by josephyim1L
Thu Feb 28, 2019 2:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Understanding cell diagrams
Replies: 2
Views: 50

Understanding cell diagrams

What is the role of the inert metal and how should it be put into the skeletal diagrams? Ex: Pt(s)
by josephyim1L
Thu Feb 28, 2019 2:32 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.17
Replies: 3
Views: 88

11.17

Can someone walk through this question with me: 11.17 (a) Calculate the reaction Gibbs free energy of N2(g) ->3 H2(g) S 2 NH3(g) when the partial pressures of N2, H2, and NH3 are 4.2 bar, 1.8 bar, and 21 bar, respectively, and the temperature is 400. K. For this reaction, K = 41 at 400. K. (b) Indic...
by josephyim1L
Thu Feb 28, 2019 2:30 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Calculations using the Van't Hoff Equation
Replies: 2
Views: 108

Calculations using the Van't Hoff Equation

What are the different applications of the Van't Hoff Equation? Example from the homework: 11.15 (a) Calculate the reaction Gibbs free energy of I2(g) S 2 I(g) at 1200. K (K = 6.8) when the partial pressures of I2 and I are 0.13 bar and 0.98 bar, respectively. (b) What is the spontaneous direction o...
by josephyim1L
Thu Feb 28, 2019 2:26 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity
Replies: 4
Views: 103

Spontaneity

How do I determine if a reaction is spontaneous or non spontaneous? E.g. is water melting spontaneous? How do I think through these different scenarios given?
by josephyim1L
Tue Feb 19, 2019 12:33 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: entropy and enthalpy
Replies: 5
Views: 113

entropy and enthalpy

are entropy and enthalpy always correlated?
by josephyim1L
Tue Feb 19, 2019 12:32 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: altering gibbs free energy equations
Replies: 2
Views: 55

altering gibbs free energy equations

can someone explains the conditions for measuring gibbs free energy?
by josephyim1L
Tue Feb 19, 2019 12:29 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy
Replies: 7
Views: 107

Gibbs free energy

Can someone explain the difference between Gibbs free energy and enthalpy/entropy/heat?
by josephyim1L
Sat Feb 09, 2019 9:08 pm
Forum: Phase Changes & Related Calculations
Topic: heat of a phase change
Replies: 5
Views: 106

heat of a phase change

what is the formula for finding the heat of a phase change?
by josephyim1L
Sat Feb 09, 2019 9:07 pm
Forum: Phase Changes & Related Calculations
Topic: Example 8.41
Replies: 1
Views: 48

Example 8.41

A 50.0 g ice cube at 0.0° C is added to a glass containing 400.0 g of water at 45.0° C.
What is the final temperature of the system? Assume that no heat is lost to the surroundings.
can someone explain how to work out this problem...
by josephyim1L
Thu Jan 31, 2019 1:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: steam vs. water
Replies: 5
Views: 103

steam vs. water

Can someone explain why burns from steam cause more damage than burns from hot water?
by josephyim1L
Thu Jan 31, 2019 1:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: understanding calculating reaction enthalpy
Replies: 2
Views: 51

understanding calculating reaction enthalpy

What does calculation of a reaction enthalpy refer to? Does it refer specifically to the heat of a reaction? I'm having trouble understanding this concept

Also, of the 3 methods Dr. lavelle described in class, which is the most-frequently used/"best method"?
by josephyim1L
Thu Jan 31, 2019 1:13 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: open, closed, isolated system and calculating internal work
Replies: 1
Views: 58

open, closed, isolated system and calculating internal work

2 questions: how do the thermodynamic equations change depending on the type of system used (closed, open, isolated...)

also, why does internal energy change = heat + work?
by josephyim1L
Thu Jan 24, 2019 9:40 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: adjusting temperature/pressure/volume
Replies: 2
Views: 55

adjusting temperature/pressure/volume

what is the best "guiding principle" for how to answer questions implying "Le Chatelier's Principle"/change in physical conditions? Will questions that ask about temperature always give whether or not the question is exothermic or endothermic?
by josephyim1L
Thu Jan 24, 2019 9:37 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Strong Acids and Bases
Replies: 5
Views: 120

Re: Strong Acids and Bases

For acid and base reactions, what is the general chemical equation? I know that for common acids and bases the acid/base loses/gains a hydrogen and water will either gain or lose a proton, but is there a general guideline to know in preparation for the test?
by josephyim1L
Thu Jan 24, 2019 9:29 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pKa and pKb
Replies: 2
Views: 54

pKa and pKb

How do I understand the differences between pOH and pKb? Are they interchangeable?
by josephyim1L
Thu Jan 17, 2019 1:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: homework help
Replies: 1
Views: 35

homework help

Can someone explain the following question to me: 11.41 A 25.0-g sample of ammonium carbamate, NH4(NH2CO2), was placed in an evacuated 0.250-L flask and kept at 25 C. At equilibrium, 17.4 mg of CO2 was present. What is the value of Kc for the decomposition of ammonium carbamate into ammonia and carb...
by josephyim1L
Tue Jan 15, 2019 1:26 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: question from module
Replies: 4
Views: 95

question from module

13. State whether the equilibrium shifts towards products, reactants, or neither when the given change occurs. 2 HI(g) + Cl2(g) ⇌ 2 HCl(g) + I2(s) delta H° = -238.0 kJ.mol-1 i. The volume of the system is compressed. ii. The temperature of the system is decreased. Can someone explain the answer to t...
by josephyim1L
Sun Jan 13, 2019 4:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solids in calculating equilibrium constant? [ENDORSED]
Replies: 8
Views: 158

solids in calculating equilibrium constant? [ENDORSED]

Are solids included in the calculation for the equilibrium constant when using partial pressure?
by josephyim1L
Wed Jan 09, 2019 5:18 pm
Forum: Ideal Gases
Topic: units for PV=nRT
Replies: 5
Views: 108

units for PV=nRT

What are the units that we are supposed to use for each element of PV=nRT?
by josephyim1L
Wed Jan 09, 2019 5:18 pm
Forum: Ideal Gases
Topic: ideal gas constant
Replies: 4
Views: 80

ideal gas constant

what is the R value for PV=nRT that we are using in order to solve for partial pressure or concentration (n/V) ?
by josephyim1L
Wed Jan 09, 2019 5:17 pm
Forum: Ideal Gases
Topic: post assessment questions
Replies: 2
Views: 67

post assessment questions

Can someone explain this question to me: 15. Carbonyl chloride (COCl2 ), also called phosgene, was used in World War I as a poisonous gas. The equilibrium concentrations for the reaction between carbon monoxide and molecular chlorine to form carbonyl chloride at 74℃ are [CO] = 1.2 x 10-2 M, [Cl2 ] =...
by josephyim1L
Thu Dec 06, 2018 1:42 am
Forum: Naming
Topic: in prep for the final
Replies: 1
Views: 34

in prep for the final

is it best to memorize the different names of common compounds/others such as oxalate and diethylene and carbonato....?
by josephyim1L
Thu Dec 06, 2018 1:41 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: in preparation for the exam...
Replies: 1
Views: 78

in preparation for the exam...

i'm a bit confused, working through the material since the last test, on how exactly to approach questions involving acids and bases, are there any particular things to look out for in these kinds of questions? What is the best way to identify an acid/base? Is it best just to memorize the most basic...
by josephyim1L
Thu Dec 06, 2018 1:38 am
Forum: Administrative Questions and Class Announcements
Topic: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]
Replies: 118
Views: 7670

Re: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]

how might one solve question 34? Should the overall concentration be found or is it only necessary to find the concentration of HCL is 1 Liter of water?
by josephyim1L
Thu Dec 06, 2018 1:36 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Defining Acids and Bases
Replies: 1
Views: 84

Defining Acids and Bases

Hi, I had a couple of questions regarding acids and bases... I have a lot of trouble identifying acids and bases and being able to identify whether or not something is acidic, polyprotic, amphiprotic, amphoteric, etc. Is there a systematic way of identify acids and bases in a reaction and based on t...
by josephyim1L
Tue Nov 27, 2018 12:06 am
Forum: Determining Molecular Shape (VSEPR)
Topic: polarity vs. nonpolarity
Replies: 8
Views: 162

polarity vs. nonpolarity

what's the easiest and most systematic way of determining if a molecular structure is polar/nonpolar? Do I have to look at the Lewis structure or know the VSEPR structure?
by josephyim1L
Tue Nov 27, 2018 12:04 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: ligands and dentates
Replies: 3
Views: 77

ligands and dentates

Can someone explain what a ligand is, how to identify it, and what it means that a ligand binds at "monodentate" or "bidentate"?
by josephyim1L
Tue Nov 27, 2018 12:03 am
Forum: Hybridization
Topic: hybridization
Replies: 1
Views: 76

hybridization

Can someone explain the differing hybrid orbitals and examples of each?

also, I'm not quite sure I understand how to determine which orbitals get hybridized and which ones remain at their original energy levels...

For the test do we have to know all the way up to d2sp3?
by josephyim1L
Tue Nov 20, 2018 11:56 pm
Forum: Hybridization
Topic: predicting hybrids
Replies: 3
Views: 54

predicting hybrids

What's the easiest way to predict the type of hybrid orbital while predicting the molecular shape?
by josephyim1L
Tue Nov 20, 2018 11:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: predicting dipole moments
Replies: 4
Views: 97

predicting dipole moments

What's the easiest, systematic way to predict intermolecular interactions?
by josephyim1L
Tue Nov 20, 2018 11:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR
Replies: 3
Views: 131

VSEPR

What does VSEPR imply about gases?
by josephyim1L
Wed Nov 14, 2018 6:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bent structure? also, intermolecular interactions
Replies: 3
Views: 48

bent structure? also, intermolecular interactions

i notice that certain carbon-containing molecules have the "bent" shape, what is a "bent" shape and how do we determine it?

In a separate vein, what is the quickest and easiest way to determine the type of molecular interactions that molecules experience?
by josephyim1L
Wed Nov 14, 2018 6:03 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape
Replies: 4
Views: 110

Re: Molecular Shape

Once the lewis structure is determined, the molecular shape is ultimately determined by the principle of stability. Due to electron-electron repulsion, the differing bond-pairs or lone-pair electrons want to be distanced as far away as possible on a 3 dimensional plane, this is manifested in the dif...
by josephyim1L
Wed Nov 14, 2018 6:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electrons and VSEPR
Replies: 4
Views: 73

Re: Electrons and VSEPR

Do lone pair electrons influence the name of the molecular shape? In the molecular geometries such as seesaw, don't lone pairs affect the name given to it, or is it just the bound electrons that influence it? lone pair electrons influence the shape of the molecular shape but don't impact the actual...
by josephyim1L
Wed Nov 07, 2018 4:26 pm
Forum: Lewis Structures
Topic: reactivity of radicals
Replies: 2
Views: 99

reactivity of radicals

Can someone explain to me the reactive potential of radicals in comparison with that of halogens? Which are more reactive?
by josephyim1L
Wed Nov 07, 2018 4:21 pm
Forum: Bond Lengths & Energies
Topic: bond lengths and strengths
Replies: 9
Views: 175

bond lengths and strengths

Can someone explain to me why single bonds are weaker than double bonds which are weaker than triple bonds? Shouldn't single bonds be the strongest?
by josephyim1L
Wed Nov 07, 2018 4:18 pm
Forum: Dipole Moments
Topic: dispersion forces vs. london forces
Replies: 2
Views: 52

dispersion forces vs. london forces

What's the difference between london forces and dispersion forces?
by josephyim1L
Wed Oct 31, 2018 5:12 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge of a compound
Replies: 3
Views: 119

Formal Charge of a compound

Does the overall formal charge of an atom (addition of formal charges of individual atoms) always have to add up to the overall charge of the compound? If the overall charge of the compound is +1 does the addition of the fc of each atom have to add up to +1?
by josephyim1L
Wed Oct 31, 2018 5:10 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and the Octet Rule
Replies: 6
Views: 207

Formal Charge and the Octet Rule

In determining the preferred Lewis Structure diagram for a given molecule, what is more important to consider: achieving and maintaining an octet or having a formal charge of 0?

Will there ever be a case when a formal charge of no 0 (1,2,-1,-2) will be preferred to having an octet?
by josephyim1L
Wed Oct 31, 2018 5:08 pm
Forum: Lewis Structures
Topic: Lewis Structures and adding multiple bonds
Replies: 2
Views: 65

Lewis Structures and adding multiple bonds

The textbook doesn't do a very good job of showing how to determine if a double bond should be added, can someone clarify how to know if a double bond or triple bond should be added for a Lewis structure?
by josephyim1L
Wed Oct 24, 2018 12:04 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: wavelength/frequency impact on determinacy?
Replies: 2
Views: 99

wavelength/frequency impact on determinacy?

How might a change in wavelength/frequency impact the heisenberg indeterminacy principle?
by josephyim1L
Wed Oct 24, 2018 12:01 am
Forum: Photoelectric Effect
Topic: ejecting electrons in quantized energy levels
Replies: 2
Views: 115

ejecting electrons in quantized energy levels

In "ejecting electrons" during the photoelectric experiment, doesn't the ability of the electron to be excited with kinetic energy contradict the rule that electrons only absorb energy in quantized amounts?
by josephyim1L
Tue Oct 23, 2018 10:29 pm
Forum: *Particle in a Box
Topic: Energy of shells vs. subshells
Replies: 2
Views: 295

Energy of shells vs. subshells

Does the energy of a 2s electron lower than the energy of a 2p orbital? In essence, can electrons with the same principle quantum number have higher or lower energy levels than each other?
by josephyim1L
Wed Oct 17, 2018 9:38 pm
Forum: *Shrodinger Equation
Topic: dz orbital
Replies: 2
Views: 51

dz orbital

In class today, Lavelle mentioned that the cone around the dz orbital is a nodal plane as well as an area of reactivity, can someone explain this in more detail?
by josephyim1L
Wed Oct 17, 2018 9:37 pm
Forum: *Shrodinger Equation
Topic: examples?
Replies: 1
Views: 84

examples?

Can someone give an example of the Shrodinger Equation or the spdf orbitals being used in a practice problem? I'm having a hard time understanding applications of the orbitals and the very abstract equations.
by josephyim1L
Wed Oct 17, 2018 9:35 pm
Forum: *Shrodinger Equation
Topic: Shrodinger Equation;
Replies: 1
Views: 67

Shrodinger Equation;

Can someone explain the primary significance of H(psi) = E(psi) and its relationship to finding the density probability of an electron. How this equation relates to the orbitals explained in class was very confusing.
by josephyim1L
Wed Oct 10, 2018 6:42 pm
Forum: Properties of Electrons
Topic: Context?
Replies: 3
Views: 86

Context?

Hi,

Can someone give context regarding increases and decreases in electron level? I'm having a hard time understanding the emission/line/atomic spectra (the graph that was shown in class that had the Balmer and Lyman series with the lines on it?
by josephyim1L
Wed Oct 10, 2018 6:37 pm
Forum: Properties of Electrons
Topic: Bohr frequency condition equation
Replies: 2
Views: 112

Bohr frequency condition equation

∆E = hv

Hi, for the above equation; can someone explain or give application to finding finding the change in energy level of an electron (∆E)? I'm having a hard time understanding what ∆E means and the nature of its behavior (quantized increases/decreases in energy level).
by josephyim1L
Wed Oct 10, 2018 6:32 pm
Forum: Properties of Electrons
Topic: atomic spectra
Replies: 2
Views: 60

atomic spectra

Hi, Can someone explain to me the whole concept behind electrons being excited to higher energy levels? I understand that incoming EM radiation excites an electron to a higher energy level, but Monday's lecture revolved around "ejecting" electrons. What is the difference between ejecting e...
by josephyim1L
Wed Oct 03, 2018 4:55 pm
Forum: Limiting Reactant Calculations
Topic: finding grams of product
Replies: 2
Views: 85

finding grams of product

For limiting reactant questions; once I've found the ratio; maybe if I have .3 moles of a substance in a 1:3 ratio with the product, i will produce at most .3 moles of the product. Now I want to find how many grams that it, do I use the molar mass of the product times 3, since its a 1:3 ratio? Or do...
by josephyim1L
Mon Oct 01, 2018 5:12 pm
Forum: Empirical & Molecular Formulas
Topic: Solving For Empirical and Molecular Formulas
Replies: 4
Views: 130

Solving For Empirical and Molecular Formulas

Im a bit confused on how to use different methods to solve for empirical and molecular formulas... Is it necessary to find the percent composition in order to find the empirical formula? For example, the question involving 339.20 g of cobalt and fluorine gas to produce 996.08 g of a product, and i'm...
by josephyim1L
Mon Oct 01, 2018 5:08 pm
Forum: Administrative Questions and Class Announcements
Topic: Tutoring? [ENDORSED]
Replies: 61
Views: 53539

Re: Tutoring? [ENDORSED]

Please try use all the free resources I am offering students in my classes: Peer Facilitated Learning Sessions https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=157&t=15397&sid=5b2d5158e781ed3535e1ecb3d1e0be81 Teaching Assistant Office Hours https://lavelle.chem.ucla.edu/forum/viewtopic.p...
by josephyim1L
Mon Oct 01, 2018 5:04 pm
Forum: Empirical & Molecular Formulas
Topic: Chemical Equations?
Replies: 4
Views: 178

Chemical Equations?

I don't quite understand what the coefficients in a chemical equation represent. Today in class, Professor Lavelle mentioned that the coefficients represent moles, and that the # of moles aren't the same, but the number of atoms are... Don't the coefficients for each element or molecule just represe...

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