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: 301

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: 189

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: 234

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: 207

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: 214

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: 207

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
Replies: 4
Views: 402

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: 326

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: 653

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
Replies: 2
Views: 230

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: 218

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: 197

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: 294

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: 336

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: 204

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: 144

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: 244

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: 347

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: 403

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: 217

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: 410

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: 228

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: 180

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: 163

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: 156

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: 217

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: 329

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: 310

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?
Sun Jan 28, 2018 6:07 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13
Replies: 3
Views: 212

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: 237

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: 114

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: 237

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)?
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: 237

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: 211

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: 612

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: 274

SiO2

Why is SiO2 polar?
Sat Dec 09, 2017 10:41 pm
Forum: Dipole Moments
Topic: Stability of Cl2
Replies: 1
Views: 377

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: 291

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: 289

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: 202

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: 252

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: 159

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: 1745

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: 938

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: 202

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: 163

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: 384

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: 154

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: 3114

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: 287

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: 182

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: 235

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: 402

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: 8039
Views: 1411197

Re: Post All Chemistry Jokes Here

Q: What did sodium tell chlorine when they met?
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: 249

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: 830

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: 895

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: 590

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: 1145

Re: Significant Figures[ENDORSED]

Generally, how many significant figures are needed when rounding percentages?