Search found 61 matches
- Tue Mar 12, 2019 11:46 pm
- Forum: General Rate Laws
- Topic: rate laws and graphs
- Replies: 4
- Views: 527
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?
- Tue Mar 12, 2019 11:44 pm
- Forum: General Rate Laws
- Topic: reaction rate(s)?
- Replies: 4
- Views: 688
reaction rate(s)?
what is the difference between a reaction rate and rate law?
- Tue Mar 12, 2019 11:43 pm
- Forum: General Rate Laws
- Topic: reaction rate vs. unique reaction rate
- Replies: 3
- Views: 381
reaction rate vs. unique reaction rate
What is the difference between reaction rate (change in reaction/change in time) vs. unique reaction rate?
- Thu Mar 07, 2019 11:01 pm
- Forum: General Rate Laws
- Topic: 15.5
- Replies: 2
- Views: 320
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...
- Thu Mar 07, 2019 11:00 pm
- Forum: General Rate Laws
- Topic: 15.3
- Replies: 3
- Views: 438
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?
- Thu Mar 07, 2019 10:59 pm
- Forum: General Rate Laws
- Topic: 15.1
- Replies: 3
- Views: 333
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...
- Thu Feb 28, 2019 2:37 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.91
- Replies: 1
- Views: 277
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.
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.
- Thu Feb 28, 2019 2:35 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: question
- Replies: 2
- Views: 299
question
Is a porous disc the same as a salt bridge?
- Thu Feb 28, 2019 2:34 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Understanding cell diagrams
- Replies: 2
- Views: 340
Understanding cell diagrams
What is the role of the inert metal and how should it be put into the skeletal diagrams? Ex: Pt(s)
- Thu Feb 28, 2019 2:32 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 11.17
- Replies: 3
- Views: 495
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...
- 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: 425
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...
- Thu Feb 28, 2019 2:26 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneity
- Replies: 4
- Views: 459
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?
- Tue Feb 19, 2019 12:33 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: entropy and enthalpy
- Replies: 5
- Views: 587
entropy and enthalpy
are entropy and enthalpy always correlated?
- Tue Feb 19, 2019 12:32 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: altering gibbs free energy equations
- Replies: 2
- Views: 314
altering gibbs free energy equations
can someone explains the conditions for measuring gibbs free energy?
- Tue Feb 19, 2019 12:29 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs free energy
- Replies: 7
- Views: 750
Gibbs free energy
Can someone explain the difference between Gibbs free energy and enthalpy/entropy/heat?
- Sat Feb 09, 2019 9:08 pm
- Forum: Phase Changes & Related Calculations
- Topic: heat of a phase change
- Replies: 5
- Views: 519
heat of a phase change
what is the formula for finding the heat of a phase change?
- Sat Feb 09, 2019 9:07 pm
- Forum: Phase Changes & Related Calculations
- Topic: Example 8.41
- Replies: 1
- Views: 242
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...
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...
- 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: 1341
steam vs. water
Can someone explain why burns from steam cause more damage than burns from hot water?
- 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: 367
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"?
Also, of the 3 methods Dr. lavelle described in class, which is the most-frequently used/"best method"?
- 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: 244
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?
also, why does internal energy change = heat + work?
- 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: 242
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?
- 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: 482
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?
- 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: 267
pKa and pKb
How do I understand the differences between pOH and pKb? Are they interchangeable?
- Thu Jan 17, 2019 1:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: homework help
- Replies: 1
- Views: 218
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...
- 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: 388
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...
- Sun Jan 13, 2019 4:19 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: solids in calculating equilibrium constant? [ENDORSED]
- Replies: 8
- Views: 810
solids in calculating equilibrium constant? [ENDORSED]
Are solids included in the calculation for the equilibrium constant when using partial pressure?
- Wed Jan 09, 2019 5:18 pm
- Forum: Ideal Gases
- Topic: units for PV=nRT
- Replies: 5
- Views: 614
units for PV=nRT
What are the units that we are supposed to use for each element of PV=nRT?
- Wed Jan 09, 2019 5:18 pm
- Forum: Ideal Gases
- Topic: ideal gas constant
- Replies: 4
- Views: 701
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) ?
- Wed Jan 09, 2019 5:17 pm
- Forum: Ideal Gases
- Topic: post assessment questions
- Replies: 2
- Views: 348
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 ] =...
- Thu Dec 06, 2018 1:42 am
- Forum: Naming
- Topic: in prep for the final
- Replies: 1
- Views: 88
in prep for the final
is it best to memorize the different names of common compounds/others such as oxalate and diethylene and carbonato....?
- Thu Dec 06, 2018 1:41 am
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: in preparation for the exam...
- Replies: 1
- Views: 233
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...
- 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: 20828
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?
- Thu Dec 06, 2018 1:36 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Defining Acids and Bases
- Replies: 1
- Views: 358
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...
- Tue Nov 27, 2018 12:06 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: polarity vs. nonpolarity
- Replies: 8
- Views: 623
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?
- Tue Nov 27, 2018 12:04 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: ligands and dentates
- Replies: 3
- Views: 399
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"?
- Tue Nov 27, 2018 12:03 am
- Forum: Hybridization
- Topic: hybridization
- Replies: 1
- Views: 242
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?
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?
- Tue Nov 20, 2018 11:56 pm
- Forum: Hybridization
- Topic: predicting hybrids
- Replies: 3
- Views: 261
predicting hybrids
What's the easiest way to predict the type of hybrid orbital while predicting the molecular shape?
- Tue Nov 20, 2018 11:54 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: predicting dipole moments
- Replies: 4
- Views: 382
predicting dipole moments
What's the easiest, systematic way to predict intermolecular interactions?
- Tue Nov 20, 2018 11:52 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR
- Replies: 3
- Views: 495
VSEPR
What does VSEPR imply about gases?
- Wed Nov 14, 2018 6:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: bent structure? also, intermolecular interactions
- Replies: 3
- Views: 204
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?
In a separate vein, what is the quickest and easiest way to determine the type of molecular interactions that molecules experience?
- Wed Nov 14, 2018 6:03 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Shape
- Replies: 4
- Views: 394
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...
- Wed Nov 14, 2018 6:01 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Electrons and VSEPR
- Replies: 4
- Views: 382
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...
- Wed Nov 07, 2018 4:26 pm
- Forum: Lewis Structures
- Topic: reactivity of radicals
- Replies: 2
- Views: 291
reactivity of radicals
Can someone explain to me the reactive potential of radicals in comparison with that of halogens? Which are more reactive?
- Wed Nov 07, 2018 4:21 pm
- Forum: Bond Lengths & Energies
- Topic: bond lengths and strengths
- Replies: 9
- Views: 902
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?
- Wed Nov 07, 2018 4:18 pm
- Forum: Dipole Moments
- Topic: dispersion forces vs. london forces
- Replies: 2
- Views: 278
dispersion forces vs. london forces
What's the difference between london forces and dispersion forces?
- Wed Oct 31, 2018 5:12 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge of a compound
- Replies: 3
- Views: 425
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?
- Wed Oct 31, 2018 5:10 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge and the Octet Rule
- Replies: 6
- Views: 679
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?
Will there ever be a case when a formal charge of no 0 (1,2,-1,-2) will be preferred to having an octet?
- Wed Oct 31, 2018 5:08 pm
- Forum: Lewis Structures
- Topic: Lewis Structures and adding multiple bonds
- Replies: 2
- Views: 292
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?
- Wed Oct 24, 2018 12:04 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: wavelength/frequency impact on determinacy?
- Replies: 2
- Views: 312
wavelength/frequency impact on determinacy?
How might a change in wavelength/frequency impact the heisenberg indeterminacy principle?
- Wed Oct 24, 2018 12:01 am
- Forum: Photoelectric Effect
- Topic: ejecting electrons in quantized energy levels
- Replies: 2
- Views: 371
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?
- Tue Oct 23, 2018 10:29 pm
- Forum: *Particle in a Box
- Topic: Energy of shells vs. subshells
- Replies: 2
- Views: 893
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?
- Wed Oct 17, 2018 9:38 pm
- Forum: *Shrodinger Equation
- Topic: dz orbital
- Replies: 2
- Views: 195
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?
- Wed Oct 17, 2018 9:37 pm
- Forum: *Shrodinger Equation
- Topic: examples?
- Replies: 1
- Views: 160
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.
- Wed Oct 17, 2018 9:35 pm
- Forum: *Shrodinger Equation
- Topic: Shrodinger Equation;
- Replies: 1
- Views: 225
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.
- Wed Oct 10, 2018 6:42 pm
- Forum: Properties of Electrons
- Topic: Context?
- Replies: 3
- Views: 303
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?
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?
- Wed Oct 10, 2018 6:37 pm
- Forum: Properties of Electrons
- Topic: Bohr frequency condition equation
- Replies: 2
- Views: 705
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).
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).
- Wed Oct 10, 2018 6:32 pm
- Forum: Properties of Electrons
- Topic: atomic spectra
- Replies: 2
- Views: 258
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...
- Wed Oct 03, 2018 4:55 pm
- Forum: Limiting Reactant Calculations
- Topic: finding grams of product
- Replies: 2
- Views: 274
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...
- Mon Oct 01, 2018 5:12 pm
- Forum: Empirical & Molecular Formulas
- Topic: Solving For Empirical and Molecular Formulas
- Replies: 4
- Views: 1874
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...
- Mon Oct 01, 2018 5:08 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Tutoring? [ENDORSED]
- Replies: 121
- Views: 240584
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...
- Mon Oct 01, 2018 5:04 pm
- Forum: Empirical & Molecular Formulas
- Topic: Chemical Equations?
- Replies: 4
- Views: 484
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...