Search found 59 matches
- Fri Mar 16, 2018 11:01 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Knowing what has a higher heat capacity
- Replies: 2
- Views: 552
Re: Knowing what has a higher heat capacity
What is the equipartition theorem?
- Fri Mar 16, 2018 5:41 pm
- Forum: General Rate Laws
- Topic: Substitution Reactions
- Replies: 2
- Views: 396
Substitution Reactions
What is the leaving group in a substitution reaction?
- Tue Mar 13, 2018 1:05 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: reaction profile
- Replies: 3
- Views: 440
Re: reaction profile
Generally, the activation energies for a forward and reverse reaction will be different if the reaction is not at equilibrium because one reaction will be endothermic and the other will be exothermic, so each side requires a different amount of energy.
- Tue Mar 13, 2018 12:58 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 15.89
- Replies: 2
- Views: 405
Re: 15.89
Also, how do you know between Step 1 and Step 3 which step is faster?
- Tue Mar 13, 2018 12:11 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 15.79
- Replies: 3
- Views: 461
Re: 15.79
For 15.79 part A, the answer states that CH3CH=CHCH2Br is the product because "the positive charge on the reactive intermediate is on a primary carbon atom". How can you determine that it is a product of higher temperature from this information?
- Sun Mar 11, 2018 3:33 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Buffer Solutions
- Replies: 2
- Views: 392
Buffer Solutions
Do we have to know about buffer solutions and how to find their voltage for the final?
- Sun Mar 11, 2018 3:29 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Reading a Cell Diagram
- Replies: 4
- Views: 773
Reading a Cell Diagram
How do you read a cell diagram from left to right? On the anode side and cathode side, how do you know which molecules are the reactants and products?
- Sun Mar 11, 2018 3:20 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Heat Required to Heat a Substance
- Replies: 5
- Views: 672
Heat Required to Heat a Substance
One of the practice problems states: "Which requires more heat: 1 mol H2(g) or 1 mol butane (g). How are we supposed to figure out which one requires more heat?
- Sat Mar 10, 2018 7:02 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Equations: ln Q vs. log Q [ENDORSED]
- Replies: 5
- Views: 1702
Equations: ln Q vs. log Q [ENDORSED]
Some of the thermodynamic equations have log Q and some have ln Q. Are these functions interchangeable or do we just have to apply whichever function the equation specifies?
- Sat Mar 10, 2018 6:50 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Steady-state vs. Pre-equilibrium [ENDORSED]
- Replies: 2
- Views: 494
Re: Steady-state vs. Pre-equilibrium [ENDORSED]
During lecture, he mentioned that the steady-state approach assumes a constant intermediate concentration in the rate-limiting step and that the pre-equilibrium approach relies on the reaction before the rate-limiting step is at equilibrium, requiring the equilbrium constant. Therefore, it may be le...
- Sat Mar 10, 2018 6:44 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Example 15.8 [ENDORSED]
- Replies: 2
- Views: 457
Re: Example 15.8 [ENDORSED]
That information should be given to you.
- Sat Mar 10, 2018 6:43 pm
- Forum: Balancing Redox Reactions
- Topic: 15.114
- Replies: 2
- Views: 432
Re: 15.114
There is no question 114. Did you mean question 41?
- Sat Mar 10, 2018 6:41 pm
- Forum: Balancing Redox Reactions
- Topic: 14.5 Part a
- Replies: 4
- Views: 594
Re: 14.5 Part a
The reason that OH- is not included is because they cancel out when you balance the redox reaction.
- Sat Mar 10, 2018 6:31 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Change in Enthalpy vs. Change in Entropy [ENDORSED]
- Replies: 2
- Views: 606
Change in Enthalpy vs. Change in Entropy [ENDORSED]
In one of the practice problems I was doing, I noticed that although heat is conserved from the system to the surroundings: delta H (system) = - (delta H surroundings), the same idea does not apply for entropy. For example, although enthalpy is conserved, the entropy lost by a system and gained by t...
- Sun Feb 25, 2018 2:05 pm
- Forum: General Rate Laws
- Topic: Writing the Rate Law
- Replies: 3
- Views: 446
Writing the Rate Law
Do we have to write the phase of the molecule when writing the specific rate law?
- Wed Feb 21, 2018 12:47 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.23a
- Replies: 2
- Views: 365
Re: 14.23a
Why are there two ions on the right side: NO3- and H+ ?
- Wed Feb 21, 2018 12:01 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.15a
- Replies: 4
- Views: 521
Re: 14.15a
Also, shouldn't AgBr(s) be incorporated into both half-reactions?
- Tue Feb 20, 2018 11:34 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Pt in Cell diagrams
- Replies: 4
- Views: 669
Re: Pt in Cell diagrams
Aren't the oxidized and reduced species always in the same solution?
- Tue Feb 20, 2018 7:26 pm
- Forum: Balancing Redox Reactions
- Topic: Writing Half-Reactions
- Replies: 6
- Views: 903
Writing Half-Reactions
If asked to give the half-reactions of an electrochemical process, do we have to flip the anode, or do we give both equations in cathode form?
- Tue Feb 20, 2018 7:05 pm
- Forum: Balancing Redox Reactions
- Topic: 14.11d [ENDORSED]
- Replies: 2
- Views: 396
Re: 14.11d [ENDORSED]
How do you determine if a reaction is acidic or basic?
- Sun Feb 11, 2018 11:30 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Cp v. Cv!
- Replies: 5
- Views: 812
Re: Cp v. Cv!
In which cases would we use Cp?
- Sat Feb 10, 2018 12:13 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G for diatomic molecules [ENDORSED]
- Replies: 2
- Views: 567
Delta G for diatomic molecules [ENDORSED]
Is the Gibbs free energy for diatomic molecules always equal to zero? Why?
- Sat Feb 10, 2018 12:11 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 9.63
- Replies: 2
- Views: 402
9.63
This question asks to determine which compounds are stable in terms of decomposition into elements under standard conditions. The answer referenced the Gibbs free energy of formation and stated that if the Gibbs free energy is positive then the reaction is not favorable and if it is negative, then i...
- Fri Feb 09, 2018 11:56 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: 9.75 [ENDORSED]
- Replies: 1
- Views: 471
9.75 [ENDORSED]
Question 9.75 on the homework asks to explain whether a crystal of octahedral cis-MX2Y4 would have a higher molar entropy from the trans isomer and then explain why or why not.The answer calculated the actual molar entropies for both isomers and then compared them to find out that the cis isomer had...
- Mon Jan 29, 2018 12:07 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy vs. Enthalpy [ENDORSED]
- Replies: 2
- Views: 481
Entropy vs. Enthalpy [ENDORSED]
What is the direct relationship between entropy and enthalpy. Are they directly proportional?
- Mon Jan 29, 2018 12:01 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 9.1
- Replies: 3
- Views: 484
Re: 9.1
The standard unit of temperature is Kelvin, so anytime the temperature is constant, use Kelvin. For changes in temperature, the change you get using Celsius and Kelvin are the same so you can just use Celsius. If you're not sure, just use Kelvin.
- Sun Jan 28, 2018 11:54 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Microstates [ENDORSED]
- Replies: 3
- Views: 612
Re: Microstates [ENDORSED]
A microstate is the arrangement of the molecules in a sample, or the various ways the molecules can be distributed differently over the available energy levels. "W" measures the number of microstates than a particular atom/molecules has. Essentially, the more microstates that a particular ...
- Sun Jan 28, 2018 6:12 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 9.7 and 9.11 formula differences
- Replies: 4
- Views: 569
Re: 9.7 and 9.11 formula differences
For 9.11, the solutions manual states that "since P is the inverse of V for ideal gases, we can write: delta S = n*R*ln(P1/P2).
How can you derive this?
How can you derive this?
- Sun Jan 28, 2018 6:07 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 9.13
- Replies: 3
- Views: 386
Re: 9.13
Why do we have to calculate the separate entropies for change in temperature and change in volume and add them up to create the total entropy? Is there any way to combine these two changes into one equation?
- Tue Jan 23, 2018 1:00 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.67
- Replies: 3
- Views: 483
Re: 8.67
C(gr) just means that the natural form of carbon is in solid graphite.
- Mon Jan 22, 2018 1:45 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.93 Part C
- Replies: 1
- Views: 203
8.93 Part C
This question asks for the change in internal energy of the system. It was calculated in Part A that the work was +3.72kJ and in Part B that the delta H was -3267.55kJ/mol. I'm a bit confused on why the work is positive in Part C. I understand that the work would be positive in Part A because it ask...
- Sun Jan 21, 2018 9:30 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.67
- Replies: 3
- Views: 483
Re: 8.67
In 8.67 part B, the desired reaction is C(gr)+2H2(g)+(1/2)O2(g) --> CH3OH(l)
What is C(gr)?
What is C(gr)?
- Sun Jan 21, 2018 9:14 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.67
- Replies: 3
- Views: 483
8.67
For the reaction 1H2+(1/2)O2--> 1H2O(liquid), the final calculation of the bond enthalpies comes to 242kJ/mol. From the tables in the textbook, the answer would work out to be a +242kJ/mol, but the solutions manual states that it is negative. Why? Also, why do you have subtract 44 kJ/mol to get the ...
- Sat Jan 20, 2018 4:51 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Change Question
- Replies: 3
- Views: 406
Re: Phase Change Question
Generally, when you have to find the energy required for a phase change, use the formula Energy (q) = (mass of sample)*(heat of fusion/vaporization of substance in J/g)
- Sun Dec 10, 2017 5:28 pm
- Forum: Bronsted Acids & Bases
- Topic: Strong Acids and Bases [ENDORSED]
- Replies: 3
- Views: 830
Strong Acids and Bases [ENDORSED]
Do strong acids and bases always dissociate 100%? Are there any cases in which they won't dissociate completely?
- Sun Dec 10, 2017 1:26 am
- Forum: Dipole Moments
- Topic: SiO2
- Replies: 2
- Views: 673
SiO2
Why is SiO2 polar?
- Sat Dec 09, 2017 10:41 pm
- Forum: Dipole Moments
- Topic: Stability of Cl2
- Replies: 1
- Views: 722
Stability of Cl2
Why is Cl2+ more stable than Cl2? I thought that since Cl2+ is a radical, it would be less stable than Cl2.
- Sat Dec 09, 2017 5:57 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Change in Equilibrium Constant
- Replies: 2
- Views: 418
Change in Equilibrium Constant
Does the equilibrium constant change when the stoichiometric constants in the equation are halved?
- Sat Dec 09, 2017 5:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.89
- Replies: 1
- Views: 475
Re: 11.89
There is a coefficient 2 because when you compare the changes in pressure for A, B, and C, you find that the ratio is: A:B:C =10:5:10 =2:1:2 Therefore, there are 2 molecules of A, 1 molecule of B, and 2 molecules of C. The balanced chemical reaction would be: 2A(g) + B(g) <--> 2C(g) To address why e...
- Thu Dec 07, 2017 4:30 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: 12.25
- Replies: 1
- Views: 281
12.25
Q: Calculate the initial molarity of Ba(OH)2 and the molarities of Ba+2, OH-, and H30+ in an aqueous solution that contains 0.43 grams of Ba(OH)2 in 0.100L of solution. For this question, I understand how to find the molarity, but I'm confused on how to set up the dissociation equation. How do you k...
- Sun Nov 19, 2017 12:34 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Polar or non-polar molecule
- Replies: 2
- Views: 399
Polar or non-polar molecule
For the molecule CH2Cl2, why is the molecule polar, when the Chlorines could be next to each other or opposite each other? Can there be cis and trans variations?
- Sun Nov 19, 2017 12:29 pm
- Forum: Hybridization
- Topic: Forming the hybridization
- Replies: 1
- Views: 264
Forming the hybridization
When naming the hybridization of an atom, why do you put the superscript only after the p, for example, bromine is sp^3d, even though d has two electrons?
- Sat Nov 11, 2017 2:04 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polar Bonds vs. Polar Molecules [ENDORSED]
- Replies: 5
- Views: 5932
Polar Bonds vs. Polar Molecules [ENDORSED]
What is the difference between polar bonds and polar molecules?
- Sat Nov 11, 2017 2:02 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shape Memorization [ENDORSED]
- Replies: 7
- Views: 1968
Re: Shape Memorization [ENDORSED]
Re: What is the difference between trigonal planar and trigonal bipyramidal? Trigonal planar has the VSEPR formula of AX3E0, meaning that the molecule has 3 bonded pairs and 0 lone pairs on the central atom, making the bond angles each 120 degrees. Ex) BH3 Trigonal bipyramidal has a VSEPR formula of...
- Sat Nov 11, 2017 12:52 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR Theory [ENDORSED]
- Replies: 2
- Views: 397
VSEPR Theory [ENDORSED]
The second rule of the VSEPR Theory Staes that there is not distinction between single and multiple bonds: a multiple bond is treated as a single region of high electron concentration. Does this mean that the probability of finding an electron in that area is greater than that of having a single bon...
- Sun Nov 05, 2017 10:48 am
- Forum: Resonance Structures
- Topic: Homework Question 3.45
- Replies: 1
- Views: 259
Homework Question 3.45
Question 3.45 reads: Draw the lewis structure that contributes to the resonance hybrid of nitric chloride (ClN02) with N as the central atom. My 3 lewis structures were as follows: A) N with a double bond on 0 and single bond on Cl and the other O B) N with a double bond on the opposite O and a sing...
- Sun Nov 05, 2017 10:16 am
- Forum: Resonance Structures
- Topic: Resonance Structures
- Replies: 3
- Views: 638
Resonance Structures
How can you determine the maximum number of resonance structures that a molecular can have?
- Wed Nov 01, 2017 4:20 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture on 11/23
- Replies: 1
- Views: 190
Lecture on 11/23
Is there a lecture on Wednesday, November 23?
- Sun Oct 29, 2017 10:57 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Homework 2.37 [ENDORSED]
- Replies: 7
- Views: 5362
Re: Homework 2.37 [ENDORSED]
Z subscript eff stands for the effective nuclear charge. Effective nuclear charge is related to a reduced electrostatic attraction of outer electrons because of shielding of outer electrons by the electrons that are closer to the nucleus. Effective nuclear charge is affected by how many electrons ar...
- Sun Oct 29, 2017 9:46 am
- Forum: Trends in The Periodic Table
- Topic: Carbon Electron Affinity [ENDORSED]
- Replies: 3
- Views: 458
Re: Carbon Electron Affinity [ENDORSED]
Since Oxygen has a lower electron affinity than carbon, does this exception carry forth to all the elements in group 15 since the subshell would be filled the same, or it it exclusive to oxygen?
- Sun Oct 22, 2017 10:21 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Magnetic Quantum numbers vs. Spin Magnetic
- Replies: 2
- Views: 550
Magnetic Quantum numbers vs. Spin Magnetic
In terms of behavior of the electron in the atom, what behavior does the magnetic quantum number explain vs. the spin magnetic quantum number? What does "spin up or down mean" in terms of the electron's behavior?
- Sun Oct 22, 2017 10:15 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Quantum Numbers - Magnetic Quantum Number
- Replies: 2
- Views: 407
Quantum Numbers - Magnetic Quantum Number
The magnetic quantum number was defined as the number that "labels different orbitals of a subshell" from lecture on Wednesday. The allowed values are l, l-1.....-l If that number is supposed to differentiate particular orbitals, how can it be negative?
- Sun Oct 22, 2017 10:03 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 4s to 3d
- Replies: 5
- Views: 695
Re: 4s to 3d
Leanne, I'm a bit confused on your statement. You say that when 3d is completely filled, then it is lower in energy than 4s? How can this be the case when you're adding electrons? Don't more electrons mean greater energy?
- Sun Oct 22, 2017 9:58 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3043183
Re: Post All Chemistry Jokes Here
Q: What did sodium tell chlorine when they met?
A: I've got my ion you.
A: I've got my ion you.
- Sun Oct 15, 2017 2:15 pm
- Forum: Properties of Light
- Topic: 1.21- understanding how light acts as a wave
- Replies: 2
- Views: 414
1.21- understanding how light acts as a wave
1.21 Q: Pick the observation that best supports the idea that electromagnetic radiation has the properties of particles. Explain reasoning. A: photoelectric effect because if light were acting as a wave then the intensity would be proportional to amplitude (size) of the wave and bigger waves means g...
- Thu Oct 12, 2017 8:26 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect: Post Module Assessment Q. 28, 29, and 30
- Replies: 12
- Views: 1411
Re: Photoelectric Effect: Post Module Assessment Q. 28, 29, and 30
For 29, why do you divide by the number of atoms in a mole?
- Mon Oct 09, 2017 11:54 pm
- Forum: Properties of Light
- Topic: Chapter 1, problem 3 [ENDORSED]
- Replies: 10
- Views: 1462
Re: Chapter 1, problem 3 [ENDORSED]
For this question, my reasoning was that the answer would be A) the speed of the radiation decreases as frequency of electromagnetic radiation decreases, because a higher frequency means that more waves are traveling per second or more cycles per second. The solutions manual, however, states that A)...
- Fri Oct 06, 2017 3:36 pm
- Forum: Balancing Chemical Reactions
- Topic: Combustion [ENDORSED]
- Replies: 6
- Views: 983
Re: Combustion [ENDORSED]
In a combustion reaction, are the products of H2O and CO2 always in the gas form? Are there any instances in which they would be in liquid form? Also, is combustion always with gaseous 02?
- Fri Oct 06, 2017 3:32 pm
- Forum: SI Units, Unit Conversions
- Topic: Significant Figures [ENDORSED]
- Replies: 9
- Views: 2065
Re: Significant Figures [ENDORSED]
Generally, how many significant figures are needed when rounding percentages?