Search found 50 matches

by Grace Boyd 2F
Wed Mar 07, 2018 9:57 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.69 [ENDORSED]
Replies: 1
Views: 100

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...
by Grace Boyd 2F
Wed Mar 07, 2018 9:54 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.67 [ENDORSED]
Replies: 1
Views: 96

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...
by Grace Boyd 2F
Wed Mar 07, 2018 9:52 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.63
Replies: 5
Views: 138

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 ...
by Grace Boyd 2F
Mon Mar 05, 2018 7:43 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: "Slow" Step Only?
Replies: 4
Views: 141

"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.
by Grace Boyd 2F
Mon Mar 05, 2018 7:42 pm
Forum: First Order Reactions
Topic: 15.29
Replies: 3
Views: 152

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...
by Grace Boyd 2F
Mon Mar 05, 2018 7:40 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.47
Replies: 1
Views: 64

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 ...
by Grace Boyd 2F
Tue Feb 27, 2018 8:42 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalytic Reactions
Replies: 2
Views: 88

Catalytic Reactions

What is a good example of a catalytic reaction? What makes a reaction qualify as catalytic?
by Grace Boyd 2F
Tue Feb 27, 2018 8:41 pm
Forum: General Rate Laws
Topic: Elementary Reactions
Replies: 4
Views: 117

Elementary Reactions

What exactly are elementary reactions? How do I write rate laws for these types of reactions?
by Grace Boyd 2F
Tue Feb 27, 2018 8:39 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Profile
Replies: 1
Views: 64

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!
by Grace Boyd 2F
Tue Feb 20, 2018 8:18 pm
Forum: Balancing Redox Reactions
Topic: oxidation
Replies: 4
Views: 131

Re: oxidation

Any element connected to itself (for example, O2, H2, F2, etc.) has an oxidation state of 0.
by Grace Boyd 2F
Tue Feb 20, 2018 8:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram/equation
Replies: 2
Views: 72

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.
by Grace Boyd 2F
Tue Feb 20, 2018 8:12 pm
Forum: Balancing Redox Reactions
Topic: Oxidation States
Replies: 2
Views: 86

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.
by Grace Boyd 2F
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: 112

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!
by Grace Boyd 2F
Tue Feb 13, 2018 9:25 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Qrev
Replies: 2
Views: 124

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!
by Grace Boyd 2F
Tue Feb 13, 2018 9:21 pm
Forum: Calculating Work of Expansion
Topic: Formula for reversible vs irreversible
Replies: 1
Views: 79

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?
by Grace Boyd 2F
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: 208

"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?
by Grace Boyd 2F
Mon Feb 05, 2018 6:02 pm
Forum: Balancing Redox Reactions
Topic: acronym for reduction
Replies: 5
Views: 175

Re: acronym for reduction

GER: Gain Electrons Reduction. This pairs great with LEO, Loss Electrons Oxidation. "LEO GER" sounds like Leo, a lion, grrring!
by Grace Boyd 2F
Mon Feb 05, 2018 6:01 pm
Forum: Balancing Redox Reactions
Topic: Salt Bridges
Replies: 14
Views: 223

Salt Bridges

What exactly do salt bridges do? I'm sort of struggling with this concept. Thank you!
by Grace Boyd 2F
Mon Jan 29, 2018 4:31 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy: State Function? [ENDORSED]
Replies: 4
Views: 183

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!
by Grace Boyd 2F
Mon Jan 29, 2018 4:30 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy: State Function?
Replies: 3
Views: 109

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!
by Grace Boyd 2F
Mon Jan 29, 2018 4:29 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: sign of entropy
Replies: 11
Views: 198

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!
by Grace Boyd 2F
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: 188

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!
by Grace Boyd 2F
Tue Jan 23, 2018 7:47 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Predicting entropy
Replies: 1
Views: 101

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!
by Grace Boyd 2F
Tue Jan 23, 2018 7:41 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy factors [ENDORSED]
Replies: 2
Views: 95

Entropy factors [ENDORSED]

Could someone please explain to me how temperature, volume, and state of matter affect the entropy of a substance? Thank you!
by Grace Boyd 2F
Tue Jan 23, 2018 7:39 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Burning Fossil Fuels
Replies: 1
Views: 91

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!
by Grace Boyd 2F
Wed Jan 10, 2018 6:05 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Predicting Molar Heat Capacity
Replies: 2
Views: 132

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!
by Grace Boyd 2F
Wed Jan 10, 2018 6:03 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 8.41 [ENDORSED]
Replies: 2
Views: 335

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...
by Grace Boyd 2F
Wed Jan 10, 2018 5:48 pm
Forum: Phase Changes & Related Calculations
Topic: Heat Capacity vs Specific Heat Capacity
Replies: 3
Views: 135

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!
by Grace Boyd 2F
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: 237

#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!
by Grace Boyd 2F
Sat Dec 09, 2017 8:35 pm
Forum: Biological Examples
Topic: #22 on Practice Test
Replies: 1
Views: 223

#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!
by Grace Boyd 2F
Sun Dec 03, 2017 12:59 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Percentage ionization
Replies: 1
Views: 113

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!
by Grace Boyd 2F
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: 130

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!
by Grace Boyd 2F
Sun Nov 26, 2017 9:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.39
Replies: 2
Views: 113

Re: 11.39

Sorry about the typo.
by Grace Boyd 2F
Sun Nov 26, 2017 9:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.39
Replies: 2
Views: 113

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 ...
by Grace Boyd 2F
Sat Nov 25, 2017 2:25 pm
Forum: Naming
Topic: Table 17.4 [ENDORSED]
Replies: 2
Views: 161

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?
by Grace Boyd 2F
Tue Nov 21, 2017 12:53 am
Forum: Conjugate Acids & Bases
Topic: Strong vs Weak Acids/bases
Replies: 4
Views: 200

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.
by Grace Boyd 2F
Tue Nov 21, 2017 12:50 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Determining the direction of reaction
Replies: 1
Views: 73

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!
by Grace Boyd 2F
Mon Nov 13, 2017 10:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: "more or less than 109.5 degrees"?
Replies: 4
Views: 256

"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!
by Grace Boyd 2F
Mon Nov 13, 2017 10:35 pm
Forum: Hybridization
Topic: How does hybridization arise?
Replies: 1
Views: 106

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!
by Grace Boyd 2F
Thu Nov 09, 2017 12:08 pm
Forum: DeBroglie Equation
Topic: Diffraction Patterns
Replies: 2
Views: 170

Diffraction Patterns

Hi, I was wondering what causes a diffraction pattern? Could someone explain how they come about? Thanks!
by Grace Boyd 2F
Tue Nov 07, 2017 11:11 am
Forum: Bond Lengths & Energies
Topic: Bond Dissociation Energy/Bond Multiplicity
Replies: 1
Views: 239

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...
by Grace Boyd 2F
Mon Oct 30, 2017 5:19 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Indeterminacy (Uncertainty) Equation
Replies: 2
Views: 269

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...
by Grace Boyd 2F
Sun Oct 29, 2017 10:18 pm
Forum: Trends in The Periodic Table
Topic: Factors Affecting Energy of an Electron
Replies: 3
Views: 208

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!
by Grace Boyd 2F
Sun Oct 29, 2017 3:24 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: +/- x meters ? [ENDORSED]
Replies: 2
Views: 185

+/- 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!
by Grace Boyd 2F
Tue Oct 24, 2017 1:25 am
Forum: Trends in The Periodic Table
Topic: 2.75
Replies: 2
Views: 119

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!
by Grace Boyd 2F
Tue Oct 24, 2017 1:21 am
Forum: Trends in The Periodic Table
Topic: Concept question (2.81)
Replies: 1
Views: 104

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 ...
by Grace Boyd 2F
Tue Oct 17, 2017 12:17 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Module- definition of spectroscopic experiment?
Replies: 2
Views: 291

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. ...
by Grace Boyd 2F
Mon Oct 09, 2017 9:58 pm
Forum: Properties of Light
Topic: Textbook problem Chapter 1 #8
Replies: 1
Views: 113

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...
by Grace Boyd 2F
Tue Oct 03, 2017 1:37 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molarity Module Question 24?
Replies: 2
Views: 129

Re: Molarity Module Question 24?

Thank you so much! That makes sense now!!
by Grace Boyd 2F
Tue Oct 03, 2017 12:14 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molarity Module Question 24?
Replies: 2
Views: 129

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...

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