Search found 41 matches

by LMendoza 2I
Tue Mar 20, 2018 10:59 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: catalysts
Replies: 3
Views: 398

Re: catalysts

Also, unlike an intermediate which is immediately used right after it's formation, a catalyst only shows up at the very beginning but is used up until the very end of the reaction and it does not interfere or interact with any of the other molecules being formed in the overall reaction.
by LMendoza 2I
Tue Mar 20, 2018 10:13 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Potential sign
Replies: 4
Views: 244

Re: Cell Potential sign

Reversing a half-reaction means your cell potential's sign will be reversed. If the cell potential sign is not already negative, then yes reversing the sign will make the cell potential negative.
by LMendoza 2I
Sat Mar 17, 2018 7:49 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy change in volume or pressure
Replies: 1
Views: 203

Entropy change in volume or pressure

In deltaS=nRln(V2/V1) is temperature and pressure constant or also changing? Similarly, in deltaS=nRln(P1/P2) is temperature and volume constant or changing?
by LMendoza 2I
Sat Mar 17, 2018 7:43 pm
Forum: General Rate Laws
Topic: 15.13
Replies: 1
Views: 267

Re: 15.13

The question explicitly states that the rate law is first-order in each reactant and the overall order of the reaction rate is a second-order process.
by LMendoza 2I
Sat Mar 17, 2018 12:25 am
Forum: Balancing Redox Reactions
Topic: 14.15 Cell Diagram
Replies: 1
Views: 203

14.15 Cell Diagram

The cell diagram for this redox reaction is Pt(s)|OH-(aq)|02(g)||02(g)|H+(aq)|Pt(s) but why is the H+ included on the cathode side of the cell diagram?
by LMendoza 2I
Thu Mar 15, 2018 7:26 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.101 (b)
Replies: 2
Views: 177

9.101 (b)

A heat pump heats a house in winter by extracting heat from the cold outdoors and releasing it into the warm interior. For the transfer of a given amount of heat, (a) how do the entropies of the interior and exterior of the house change (increase or decrease)? (b) Which change is greater? Assume tha...
by LMendoza 2I
Thu Mar 15, 2018 7:13 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 2
Views: 146

Re: Molecularity

For any elementary reactions you will need to know if a reaction is unimolecular, bimolecular, or termolecular. -An elematary reaction is unimolecular when only one reactant molecule participates. Ex: 03->02 + 0 -An elematary reaction is bimolecular when two reactant molecules come together to react...
by LMendoza 2I
Tue Mar 13, 2018 10:42 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific Heat Capacity vs. deltaHfus and deltaHvap
Replies: 2
Views: 227

Specific Heat Capacity vs. deltaHfus and deltaHvap

What's the difference between the specific heat capacity and deltaHfus/vap?
by LMendoza 2I
Sun Mar 04, 2018 5:17 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst, Equation, and Rate Law
Replies: 4
Views: 484

Re: Catalyst, Equation, and Rate Law

Hey, A catalyst is accounted for in the rate law because it speeds up the reaction. It isn't considered in a balanced chemical equation because it doesn't undergo any change, nor does it affect any of the reactants in anyway besides increasing the speed of the reaction. So basically, does the catal...
by LMendoza 2I
Sun Mar 04, 2018 5:08 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy and Temperature Dependence of Rates
Replies: 2
Views: 96

Re: Activation Energy and Temperature Dependence of Rates

Also quick remark, the larger the activation energy is the higher the temperature will need to be to provide sufficient energy to overcome the high activation energy. So high activation energies really depend on strong temperatures.
by LMendoza 2I
Sun Mar 04, 2018 3:12 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.67 b
Replies: 1
Views: 70

15.67 b

Why is the rate enhancement lower at high temperatures?
by LMendoza 2I
Tue Feb 27, 2018 9:17 pm
Forum: Second Order Reactions
Topic: 15.35
Replies: 1
Views: 107

15.35

In part a of this question, when using the equation kt=1/[A]t - 1/[A]0 and rearranging it to find t as t=(1/[A]t - 1/[A]0)/k why do we need to divide [A]t by 1/16 ?
by LMendoza 2I
Tue Feb 27, 2018 9:08 pm
Forum: Second Order Reactions
Topic: 15.35
Replies: 2
Views: 131

Re: 15.35

You can also use the half life equation for a second-order reaction (t1/2=1/k[A]0) and rearrange it so that you can get k (k=1/[A]0*t1/2).
by LMendoza 2I
Sun Feb 25, 2018 11:59 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Strongly Reducing Metals
Replies: 5
Views: 184

Re: Strongly Reducing Metals

When a metal is the reducing agent it generally means that this metal is being oxidized so the reduction potential of this metal would have to be more negative since the strongest oxidation elements have the lowest reduction potentials.
by LMendoza 2I
Sun Feb 25, 2018 11:33 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.41b. Homework b
Replies: 2
Views: 149

Re: 14.41b. Homework b

You want to find the simplest form of this balanced half-reaction. Therefore, the simplest form of this balanced half-reaction is when n=1.
by LMendoza 2I
Thu Feb 22, 2018 8:55 am
Forum: Balancing Redox Reactions
Topic: 14.85 [ENDORSED]
Replies: 1
Views: 98

14.85 [ENDORSED]

How do we know how to order the following metals; Fe, Ag, Au, Zn, Cu, Ni, Co, and Al from strongest to lowest reducing metal?
by LMendoza 2I
Tue Feb 13, 2018 6:17 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.45
Replies: 3
Views: 142

Re: 9.45

Do you use -deltaHfus for the system since it's releasing heat because it is freezing?
by LMendoza 2I
Mon Feb 12, 2018 8:30 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: Boltzmann Equation
Replies: 3
Views: 280

Re: Boltzmann Equation

Yes you are correct. As the temperature increases, molecules occupy more energy states so there is a higher degeneracy W.
by LMendoza 2I
Mon Feb 12, 2018 8:21 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Gas Constant, R
Replies: 6
Views: 219

Re: Gas Constant, R

It depends on the formula you use and the units within the formula you use and values you are given.
by LMendoza 2I
Mon Feb 12, 2018 8:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.77
Replies: 2
Views: 123

8.77

How does the Kekule structure with 6 resonance-stabilized bonds look like and why is this structure more stable?
by LMendoza 2I
Sat Feb 03, 2018 10:07 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Entropy and Work
Replies: 2
Views: 134

Entropy and Work

What's the main relationship between entropy and work that is not done as heat?
by LMendoza 2I
Sat Feb 03, 2018 10:04 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: G at minimum
Replies: 6
Views: 163

Re: G at minimum

So if Gibbs Free Energy is at a maximum or minimum, it means that the reaction is at equilibrium?
by LMendoza 2I
Tue Jan 30, 2018 12:54 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 9.19
Replies: 3
Views: 146

9.19

In this question you are using S=nCpln(T2/T1):

The final units are J.K-1.mol-1 but how do the mol units not cancel out when you are multiplying (1.00mol H2O) by the molar heat capacity which has the units (J.K-1.mol-1)?
by LMendoza 2I
Tue Jan 30, 2018 12:37 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.27 D
Replies: 3
Views: 120

9.27 D

Question: Which substance in each of the following pairs has the highest molar entropy at 298K; (d)1.0 mol Ar(g) at 1.00atm or 1.0molAr(g) at 2.00atm? According to the solution's manual 1 mol of Ar(g) at 1.00atm has a higher molar entropy because Ar(g) at 1.00atm would occupy a larger volume but I'm...
by LMendoza 2I
Mon Jan 29, 2018 10:49 pm
Forum: General Science Questions
Topic: Significant Figures
Replies: 2
Views: 300

Re: Significant Figures

You have to convert the 20 degrees celsius into kelvins and once you do this your temperature will be 293 kelvins. Since 100 J.s-1 and 293K both consist of 3 significant figures, then so should your answer (0.341J.K-1.s-1).
by LMendoza 2I
Mon Jan 29, 2018 10:38 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Adiabatic and enthalpy related?
Replies: 2
Views: 112

Re: Adiabatic and enthalpy related?

I would assume that enthalpy is not related to an adiabatic system since energy cannot be transferred through heat in an adiabatic system but only as work. Since enthalpy occurs when heat is absorbed or released, it can't be possible for an adiabatic system to be related with enthalpy.
by LMendoza 2I
Fri Jan 19, 2018 8:15 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q 8.25
Replies: 1
Views: 93

Q 8.25

In the reaction of this question, why is the heat of the reaction and the heat of the calorimeter equal to 0 (qreaction+qcalorimeter=0)?
by LMendoza 2I
Fri Jan 19, 2018 8:05 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7348
Views: 891020

Re: Post All Chemistry Jokes Here

If Avogadro calls, tell him to leave his number.
by LMendoza 2I
Fri Jan 19, 2018 7:52 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated vs. Adiabatic system
Replies: 8
Views: 528

Isolated vs. Adiabatic system

What are the main differences between an isolated and adiabatic system?
by LMendoza 2I
Fri Jan 19, 2018 11:27 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: W=-(Pex)(deltaV)
Replies: 5
Views: 232

Re: W=-(Pex)(deltaV)

There is a negative sign in this equation because energy is being lost as work when the system is expanding and this causes the internal energy of the system to decrease.
by LMendoza 2I
Fri Jan 19, 2018 11:15 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.29
Replies: 4
Views: 127

Re: 8.29

The more bonds there is, the harder it is to break them. Therefore, more heat would be required and the heat capacity would be higher.
by LMendoza 2I
Fri Jan 19, 2018 11:11 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 8.1 question
Replies: 8
Views: 271

Re: 8.1 question

Coffee in a thermos bottle would not exchange heat with it's surroundings because a thermos bottle is an isolated system. Therefore, it cannot exchange energy or matter with it's surroundings. However, the amount of time the temperature of the coffee remains hot can really depend on the type of ther...
by LMendoza 2I
Sun Dec 10, 2017 1:38 am
Forum: Calculating the pH of Salt Solutions
Topic: When to use ICE table?
Replies: 3
Views: 1563

When to use ICE table?

Hi, so I’m confused about when I should use an ice table to find acid and base equilibrium concentrations. I know you should use it when only given one molar concentration of an acid/base but other than that should I only use it when finding concentrations of weak acids and bases?
by LMendoza 2I
Sun Dec 03, 2017 11:23 pm
Forum: Identifying Acidic & Basic Salts
Topic: 12.51
Replies: 1
Views: 235

12.51

Determine which acid in each of the following pairs is stronger and explain why: (a) HF or HCl; (b) HClO or HClO2; (c) HBrO2 or HClO2; (d) HClO4 or H3PO4; (e) HNO3 or HNO2; (f) H2CO3 or H2GeO3. For this question, I'm having trouble understanding why acids that contain a more electronegative atom typ...
by LMendoza 2I
Mon Nov 20, 2017 9:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Part D; Question 17.33
Replies: 1
Views: 147

Part D; Question 17.33

Why is it that Oxalate is a bidentate ligand and can only have a metal bond to two of its oxygen atoms when it originally has 4 oxygen atoms that all contain lone pairs?
by LMendoza 2I
Fri Nov 17, 2017 10:12 pm
Forum: Hybridization
Topic: Chelate
Replies: 2
Views: 157

Chelate

Hi, can someone explain to me a little more what the concept of chelating ligands is and what is it's significance?
by LMendoza 2I
Mon Nov 06, 2017 12:01 am
Forum: Ionic & Covalent Bonds
Topic: 3.77 [ENDORSED]
Replies: 1
Views: 103

3.77 [ENDORSED]

For each bond determine which compound has bonds with greater ionic character:
a)HCL or HI
b)CH4 or CF4
c)CO2 or CS2

Why does HCL in question a have the greater ionic character?
by LMendoza 2I
Fri Oct 27, 2017 9:34 pm
Forum: Resonance Structures
Topic: Delocalized Structures [ENDORSED]
Replies: 2
Views: 152

Delocalized Structures [ENDORSED]

Why is it that delocalized lewis structures are more stable? Also, why does it matter if a structure is more or less stable?
by LMendoza 2I
Sun Oct 15, 2017 11:28 pm
Forum: Quantum Numbers and The H-Atom
Topic: Wave Properties of Electron and the De Broglie Equation Post Assessment, Q.35
Replies: 2
Views: 210

Wave Properties of Electron and the De Broglie Equation Post Assessment, Q.35

Calculate the wavelength of a 275 kg single-seat electric car traveling at a speed of 125 km.hr-1. Do electric cars have wavelike properties? A. λ = 6.94 x 10-38 m , Yes B. λ = 6.94 x 10-38 m , No C. λ = 1.93 x 10-38 m , Yes D. λ = 1.93 x 10-38 m , No I know how to calculate the wavelength of this e...
by LMendoza 2I
Fri Oct 13, 2017 7:57 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post-Assessment Q. 29 [ENDORSED]
Replies: 2
Views: 267

Re: Atomic Spectra Post-Assessment Q. 29 [ENDORSED]

Hi, so how do you calculate the energy per photon? I tried calculating the energy per photon but I got a different answer.
by LMendoza 2I
Thu Oct 05, 2017 3:50 pm
Forum: Limiting Reactant Calculations
Topic: Determining Limiting Reactant
Replies: 6
Views: 486

Determining Limiting Reactant

Does anyone know if the limiting reactant will always be the product with the least amount of moles but when converted into grams, will the LR be the product with the greatest amount of theoretical grams?

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