Search found 50 matches
- Wed Mar 07, 2018 9:57 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: 15.69 [ENDORSED]
- Replies: 1
- Views: 299
15.69 [ENDORSED]
A reaction rate increases by a factor of 1000. in the presence of a catalyst at 25 degrees Celsius. The activation energy of the original pathway is 98 kJ/mol. What is the activation energy of the new pathway, all other factors being equal? In practice, the new pathway also has a different pre-expon...
- Wed Mar 07, 2018 9:54 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: 15.67 [ENDORSED]
- Replies: 1
- Views: 319
15.67 [ENDORSED]
The presence of a catalyst provides a reaction pathway in which the activation energy of a certain reaction is reduced from 125 kJ/mol to 75 kJ/mol. (a) By what factor does the rate of the reaction increase at 298 K, all other factors being equal? (b) By what factor would the rate change if the reac...
- Wed Mar 07, 2018 9:52 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 15.63
- Replies: 5
- Views: 1182
15.63
The rate constant of the reaction between CO2 and OH- in aqueous solution to give the HCO3- ion is 1.5 x 10^10 L*mol-1*s-1 at 25 Celsius. Determine the rate constant at blood temperature (37 degrees C) given that the activation energy for the reaction is 38 kJ/mol. Could someone please explain step ...
- Mon Mar 05, 2018 7:43 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: "Slow" Step Only?
- Replies: 4
- Views: 641
"Slow" Step Only?
Why do we only consider reactants in the slow step when determining the rate law? Why don't we include the fast step reactants? Thank you.
- Mon Mar 05, 2018 7:42 pm
- Forum: First Order Reactions
- Topic: 15.29
- Replies: 3
- Views: 693
15.29
Hi, I am really confused by this question. For the first-order reaction A-->3B+C, when concentration initial of A = 0.015mol/L, the concentration of B increases to 0.018 mol/L in 3.0 min. a) What is the rate constant for the reaction expressed as the rate of loss of A? b) How much time would be need...
- Mon Mar 05, 2018 7:40 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 15.47
- Replies: 1
- Views: 267
15.47
Textbook question 15.47 asks us to write the overall reaction for the following proposed mechanism and identify the reaction intermediates. But, instead of giving our steps in the form of regular equations we are given molecules drawn out by structure. The textbook solution then has the equation in ...
- Tue Feb 27, 2018 8:42 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalytic Reactions
- Replies: 2
- Views: 340
Catalytic Reactions
What is a good example of a catalytic reaction? What makes a reaction qualify as catalytic?
- Tue Feb 27, 2018 8:41 pm
- Forum: General Rate Laws
- Topic: Elementary Reactions
- Replies: 4
- Views: 612
Elementary Reactions
What exactly are elementary reactions? How do I write rate laws for these types of reactions?
- Tue Feb 27, 2018 8:39 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Reaction Profile
- Replies: 1
- Views: 258
Reaction Profile
Could someone please step by step explain to me how to draw a reaction profile? I am really confused by the book's explanation. Thank you!
- Tue Feb 20, 2018 8:18 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation
- Replies: 4
- Views: 723
Re: oxidation
Any element connected to itself (for example, O2, H2, F2, etc.) has an oxidation state of 0.
- Tue Feb 20, 2018 8:15 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell diagram/equation
- Replies: 2
- Views: 340
Re: Cell diagram/equation
One thing to keep In mind is that if you multiply the entire equation by a coefficient, the Ecell value does not multiply by that coefficient! The only reason the Ecell would change is if you reverse the reaction and the equation is multiplied by -1.
- Tue Feb 20, 2018 8:12 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation States
- Replies: 2
- Views: 370
Re: Oxidation States
Remember that oxygen is most commonly 2- because this element in this state comes up very often! Also, remember that Hydrogen is +1. H and O are two elements that you definitely want to make sure you know.
- Tue Feb 13, 2018 9:29 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bonds formed - negative?
- Replies: 3
- Views: 1686
Bonds formed - negative?
When we are using bond enthalpies to find the overall enthalpy, why is there a negative sign in front of bonds formed? This seems counterintuitive to me. I would think that bonds broken would be negative. Thanks!
- Tue Feb 13, 2018 9:25 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Qrev
- Replies: 2
- Views: 1056
Qrev
What does Qrev mean in the equation Qrev/T ? I know this is probably a very basic question but I always just assume it means heat and ignore the "rev" part. Thank you!
- Tue Feb 13, 2018 9:21 pm
- Forum: Calculating Work of Expansion
- Topic: Formula for reversible vs irreversible
- Replies: 1
- Views: 274
Formula for reversible vs irreversible
Which equation is for reversible work and which is for irreversible? Also, how can I tell if a problem is asking about reversible or irreversible work if It doesn't explicitly state?
- Mon Feb 05, 2018 6:56 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: "Favorability"
- Replies: 5
- Views: 796
"Favorability"
I was wondering what it means when an outcome is favorable. I know what qualifies for the outcome to be favorable, but what does being favorable tell us about the outcome?
- Mon Feb 05, 2018 6:02 pm
- Forum: Balancing Redox Reactions
- Topic: acronym for reduction
- Replies: 5
- Views: 2324
Re: acronym for reduction
GER: Gain Electrons Reduction. This pairs great with LEO, Loss Electrons Oxidation. "LEO GER" sounds like Leo, a lion, grrring!
- Mon Feb 05, 2018 6:01 pm
- Forum: Balancing Redox Reactions
- Topic: Salt Bridges
- Replies: 14
- Views: 1288
Salt Bridges
What exactly do salt bridges do? I'm sort of struggling with this concept. Thank you!
- Mon Jan 29, 2018 4:31 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy: State Function? [ENDORSED]
- Replies: 4
- Views: 2791
Gibbs Free Energy: State Function? [ENDORSED]
I was wondering if someone could explain to me why Gibbs Free Energy is considered a state function. Thank you!
- Mon Jan 29, 2018 4:30 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy: State Function?
- Replies: 3
- Views: 458
Gibbs Free Energy: State Function?
I was wondering if someone could explain to me why Gibbs Free Energy is considered a state function. Thank you!
- Mon Jan 29, 2018 4:29 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: sign of entropy
- Replies: 11
- Views: 1634
Re: sign of entropy
As Dr. Lavelle explained today in lecture, the sign of entropy depends on the direction of heat flow. If the system loses heat, the entropy will have a negative sign in front of it. If the surroundings gain heat, the entropy will have a positive sign. I hope this helps!
- Mon Jan 29, 2018 4:25 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Entropy Change factors
- Replies: 6
- Views: 780
Entropy Change factors
I was wondering if someone could explain to me why more complex molecules have a greater standard entropy value than less complex molecules. Thank you!
- Tue Jan 23, 2018 7:47 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Predicting entropy
- Replies: 1
- Views: 252
Predicting entropy
I was wondering how we predict entropy, like for example if given two systems which of the two systems has the greater entropy, given their compositions and conditions. Could someone explain this? Thank you!
- Tue Jan 23, 2018 7:41 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy factors [ENDORSED]
- Replies: 2
- Views: 380
Entropy factors [ENDORSED]
Could someone please explain to me how temperature, volume, and state of matter affect the entropy of a substance? Thank you!
- Tue Jan 23, 2018 7:39 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Burning Fossil Fuels
- Replies: 1
- Views: 169
Burning Fossil Fuels
I was wondering if someone could explain this key concept to me for the week 3 test:
Understand the environmental impact of burning fossil fuels, and the use of alternative fuels.
Thank you!
Understand the environmental impact of burning fossil fuels, and the use of alternative fuels.
Thank you!
- Wed Jan 10, 2018 6:05 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Predicting Molar Heat Capacity
- Replies: 2
- Views: 318
Predicting Molar Heat Capacity
How do I predict molar heat capacity in relation to another molecular substance? For example, chapter 8 question 29 asks whether NO or NO2 would have a higher molar heat capacity. How do I predict this? Thank you!
- Wed Jan 10, 2018 6:03 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 8.41 [ENDORSED]
- Replies: 7
- Views: 3123
8.41 [ENDORSED]
A 50.0-g ice cube at 0.0 degrees Celsius is added to a glass containing 400.0g of water at 45.0 degrees Celsius. What is the final temperature of the system (use tables 8.2 and 8.3)? Assume that no heat is lost to the surroundings. I was wondering if anyone could help me with the steps to approach t...
- Wed Jan 10, 2018 5:48 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heat Capacity vs Specific Heat Capacity
- Replies: 3
- Views: 354
Heat Capacity vs Specific Heat Capacity
I was wondering what the difference between heat capacity and specific heat capacity is. The book explains this a little but I was wondering if someone could put it in their own words to help clarify. Thank you!
- Sat Dec 09, 2017 8:38 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: #33 on Practice test
- Replies: 1
- Views: 459
#33 on Practice test
Hi, I was wondering if someone could explain the answer to this question:
NH4HS (s) <-- --> NH3 (g) + H2S (g)
Describe and explain what will happen to the reaction if the system is compressed.
A: Shifts left
Why is this? I was trying to follow at the review session but was lost.
Thanks!
NH4HS (s) <-- --> NH3 (g) + H2S (g)
Describe and explain what will happen to the reaction if the system is compressed.
A: Shifts left
Why is this? I was trying to follow at the review session but was lost.
Thanks!
- Sat Dec 09, 2017 8:35 pm
- Forum: Biological Examples
- Topic: #22 on Practice Test
- Replies: 1
- Views: 341
#22 on Practice Test
Hi, I am pretty confused with this question:
A protein-like histidine can bind at one site to the heme complex iron to form myoglobin. How many O2 molecules can myoglobin bind?
The answer is 1, but I don't really understand why that is the answer. Could someone help? Thanks!
A protein-like histidine can bind at one site to the heme complex iron to form myoglobin. How many O2 molecules can myoglobin bind?
The answer is 1, but I don't really understand why that is the answer. Could someone help? Thanks!
- Sun Dec 03, 2017 12:59 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Percentage ionization
- Replies: 1
- Views: 252
Percentage ionization
Is there a formula for calculating the percentage ionization of a weak acid or base? How do I approach problems where I have to calculate the percent dissociation of a weak acid or base? Thank you!
- Fri Dec 01, 2017 11:24 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Conceptual question about pH / pOH [ENDORSED]
- Replies: 1
- Views: 347
Conceptual question about pH / pOH [ENDORSED]
Could someone please explain to me why solutions of weak acids have higher pH values than solutions of strong acids at the same concentration? I am struggling with this concept. Thank you!
- Sun Nov 26, 2017 9:31 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.39
- Replies: 2
- Views: 332
Re: 11.39
Sorry about the typo.
- Sun Nov 26, 2017 9:10 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.39
- Replies: 2
- Views: 332
11.39
"Use the information in table 11.2 to determine the value of K at 500 K for the reaction 2 BrCl(g) + H2(g) = Br2(g) + 2 HCl (g) " The equations given in table 11.2 are: 2 BrCl(g) = Br2(g) + Cl2(g) K=377 H2(g) + Cl2(g) = 2HCl(g). K=4.0x10^31 I am wondering why in the solutions it says that ...
- Sat Nov 25, 2017 2:25 pm
- Forum: Naming
- Topic: Table 17.4 [ENDORSED]
- Replies: 2
- Views: 361
Table 17.4 [ENDORSED]
For some of the anionic ligands, they have more than one name in table 17.4. Can we use either name, or is one preferred over the other? For example, CN- has both isocyano and cyanido-KN. Should we be prepared to know both names?
- Tue Nov 21, 2017 12:53 am
- Forum: Conjugate Acids & Bases
- Topic: Strong vs Weak Acids/bases
- Replies: 4
- Views: 889
Strong vs Weak Acids/bases
What is the difference between solutions of strong vs weak acids/bases? The textbook lists a lot of variations and I was wondering what the most critical ones are to fully understand for this course.
- Tue Nov 21, 2017 12:50 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Determining the direction of reaction
- Replies: 1
- Views: 221
Determining the direction of reaction
How do I determine the direction of a reaction, given K and the concentrations of all reactants and
products? Thank you!
products? Thank you!
- Mon Nov 13, 2017 10:38 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: "more or less than 109.5 degrees"?
- Replies: 4
- Views: 1906
"more or less than 109.5 degrees"?
Hi,
In the homework and in class I have a hard time following when we are asked whether or not the angle will be greater or less than 109.5 degrees. How is this answer determined? I can never tell! I think I am missing the concept here. Thank you for your help!
In the homework and in class I have a hard time following when we are asked whether or not the angle will be greater or less than 109.5 degrees. How is this answer determined? I can never tell! I think I am missing the concept here. Thank you for your help!
- Mon Nov 13, 2017 10:35 pm
- Forum: Hybridization
- Topic: How does hybridization arise?
- Replies: 1
- Views: 215
How does hybridization arise?
I was wondering exactly how hybridization arises from atomic orbitals. The textbook is sort of confusing me, could someone try explaining it to me? I appreciate it!
- Thu Nov 09, 2017 12:08 pm
- Forum: DeBroglie Equation
- Topic: Diffraction Patterns
- Replies: 2
- Views: 351
Diffraction Patterns
Hi, I was wondering what causes a diffraction pattern? Could someone explain how they come about? Thanks!
- Tue Nov 07, 2017 11:11 am
- Forum: Bond Lengths & Energies
- Topic: Bond Dissociation Energy/Bond Multiplicity
- Replies: 1
- Views: 1541
Bond Dissociation Energy/Bond Multiplicity
I saw this key concept on the syllabus and was wondering if someone could explain this concept to the extent I should understand for the midterm. I'm a bit confused on what bond multiplicity means in particular. Thanks! "Explain how bond dissociation energy is related to bond multiplicity, atom...
- Mon Oct 30, 2017 5:19 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg Indeterminacy (Uncertainty) Equation
- Replies: 2
- Views: 759
Re: Heisenberg Indeterminacy (Uncertainty) Equation
Delta x is the diameter of the atom, so to begin, you would double the 0.05 nm radius and get 0.1 nm. From there, you multiply 0.1 nm by 0.01 (the decimal form of 1%). Remember to put your nm in meters first! So your equation would be (1.0x10^-10m)(0.01) and that would give you the uncertainty in de...
- Sun Oct 29, 2017 10:18 pm
- Forum: Trends in The Periodic Table
- Topic: Factors Affecting Energy of an Electron
- Replies: 3
- Views: 1303
Factors Affecting Energy of an Electron
I was going through the key concepts we should know for test three and came across this one.
Describe the factors affecting the energy of an electron in a many-electron atom.
I am unsure what factors affect the energy of a multi-electron atom and was wondering if someone could explain. Thank you!
Describe the factors affecting the energy of an electron in a many-electron atom.
I am unsure what factors affect the energy of a multi-electron atom and was wondering if someone could explain. Thank you!
- Sun Oct 29, 2017 3:24 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: +/- x meters ? [ENDORSED]
- Replies: 2
- Views: 476
+/- x meters ? [ENDORSED]
I have a question about Heisenberg's Indeterminacy Equation. In my discussion, I believe it was mentioned that if the meters are given as +/- __meters, you double this amount for the total delta x position. Is this correct? I just want to confirm before Test 3. Thank you!
- Tue Oct 24, 2017 1:25 am
- Forum: Trends in The Periodic Table
- Topic: 2.75
- Replies: 2
- Views: 367
2.75
"Why are s-block metals typically more reactive than p-block metals?"
I was wondering if someone could explain what the textbook means with the word "reactive" in this case (more reactive with what?) as well as the correct answer to why s-block metals are more reactive. Thank you!
I was wondering if someone could explain what the textbook means with the word "reactive" in this case (more reactive with what?) as well as the correct answer to why s-block metals are more reactive. Thank you!
- Tue Oct 24, 2017 1:21 am
- Forum: Trends in The Periodic Table
- Topic: Concept question (2.81)
- Replies: 1
- Views: 244
Concept question (2.81)
Hi, this is more of a conceptual question but I am pretty confused by it and was wondering if anyone could please explain the answer to me. "Ionization energies usually increase on going from left to right across the periodic table. The ionization energy for oxygen, however, is lower than that ...
- Tue Oct 17, 2017 12:17 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Module- definition of spectroscopic experiment?
- Replies: 2
- Views: 606
Module- definition of spectroscopic experiment?
“Choose the right description for the experimental setup in a spectroscopic experiment using a sample of hydrogen gas atoms as an example. A. Light with many wavelengths is shone on the hydrogen sample. A detector measures wavelengths of light which are absorbed or emitted by the hydrogen atoms. B. ...
- Mon Oct 09, 2017 9:58 pm
- Forum: Properties of Light
- Topic: Textbook problem Chapter 1 #8
- Replies: 1
- Views: 213
Textbook problem Chapter 1 #8
"b) Radioastronomers use 1420. -MHz waves to look at interstellar clouds of hydrogen atoms. What is the wavelength of this radiation?" My question is regards to the negative sign in front of MHz. The textbook has a hyphen before the MHz label, and I am unsure of if this is a typo or if neg...
- Tue Oct 03, 2017 1:37 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Molarity Module Question 24?
- Replies: 3
- Views: 377
Re: Molarity Module Question 24?
Thank you so much! That makes sense now!!
- Tue Oct 03, 2017 12:14 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Molarity Module Question 24?
- Replies: 3
- Views: 377
Molarity Module Question 24?
"Calculate the volume of 0.642 M KOH (aq) needed to prepare 1 L of 0.101 M KOH (aq)." I tried doing this problem using the M1V1=M2V2 equation, and plugged in (0.642 M)(V)=(1 L)(0.101 M) and got 6.356 L as my final answer. On the online module, this is not an option, so I must be doing some...