Search found 46 matches

by Andres Merlos 2L
Sun Mar 08, 2020 9:08 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: pre-exponential factor
Replies: 3
Views: 30

Re: pre-exponential factor

It is the frequency of collisions.
by Andres Merlos 2L
Sun Mar 08, 2020 9:07 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 16
Views: 592

Re: Catalysts

Catalysts reduce the activation energy.
by Andres Merlos 2L
Sun Mar 08, 2020 9:03 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Where do we find the values for A?
Replies: 5
Views: 101

Re: Where do we find the values for A?

It's pretty much like finding a missing variable for any standard equation. As long as you have the temperature, activation energy, gas constant, and gas constant, you can solve for A. A is the frequency of collisions.
by Andres Merlos 2L
Sun Mar 08, 2020 8:56 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Intermediate Species
Replies: 9
Views: 73

Re: Intermediate Species

An intermediate species is not part of the overall reaction equation, but it does play a role in the mechanisms of it. It is formed and consumed in the middle of the reaction.
by Andres Merlos 2L
Sun Mar 08, 2020 8:44 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation
Replies: 4
Views: 59

Re: Arrhenius Equation

With factors like temperature, frequency of collisions, catalyst presence, and activation energy, you can determine the rate of reaction.
by Andres Merlos 2L
Sun Mar 08, 2020 8:11 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A in the Arrhenius Equation
Replies: 3
Views: 46

Re: A in the Arrhenius Equation

A stands for the frequency of collisions.
by Andres Merlos 2L
Sun Mar 01, 2020 5:53 pm
Forum: General Rate Laws
Topic: Reaction Rates
Replies: 5
Views: 74

Re: Reaction Rates

It's almost like slowing down while running. Although you have slowed down, you are still moving forward, you wouldn't be going backwards. Similar to this, reaction rates are always positive because in a forward reaction, the reaction does not go backwards.
by Andres Merlos 2L
Sun Mar 01, 2020 5:49 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Diamond
Replies: 6
Views: 108

Diamond

Why is it that diamond is kinetically stable and controlled with respect to graphite if the reaction for this to happens takes so long under STP? Is it because it is quicker, relative to graphite?
by Andres Merlos 2L
Sun Mar 01, 2020 5:32 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: how can you tell
Replies: 11
Views: 146

Re: how can you tell

Thermodynamic-controlled reactions are usually long, while kinetic-controlled reactions are relatively quick.
by Andres Merlos 2L
Sun Mar 01, 2020 5:21 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: intermediate
Replies: 22
Views: 664

Re: intermediate

Intermediates are produced then consumed, during some part of the reaction. It cannot exist in rate law because they are not a part of the overall equation.
by Andres Merlos 2L
Sun Mar 01, 2020 5:17 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Activation Energy
Replies: 16
Views: 575

Re: Activation Energy

Activation energy is the amount of energy needed to turn reactants to products. This is depicted on a diagram with the highest hump.
by Andres Merlos 2L
Sat Feb 22, 2020 10:08 pm
Forum: Balancing Redox Reactions
Topic: Basic conditions
Replies: 6
Views: 75

Re: Basic conditions

In a basic solution, you would use hydroxide (OH-) to balance out the hydrogens (H). This is different from acidic solutions, in which you would use (H3O+) to balance out any hydrogens (H).
by Andres Merlos 2L
Sat Feb 22, 2020 9:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: property of E
Replies: 6
Views: 42

Re: property of E

E is an intensive property, so it does not depend on the amount of times the reaction occurs. The voltage difference will remain the same, because of this.
by Andres Merlos 2L
Sat Feb 22, 2020 9:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard Cell Potentials
Replies: 4
Views: 48

Re: Standard Cell Potentials

The anode is typically on the left, while the cathode is on the right. It would be the potential on the right (cathode) minus the potential on the left (anode).
by Andres Merlos 2L
Sat Feb 22, 2020 9:56 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 10
Views: 116

Re: Salt Bridge

The salt bridge is needed to allow ions to flow freely, which will free any charge buildup. It is important for this to occur, because it allows the flow of electrons to be maintained.
by Andres Merlos 2L
Sat Feb 22, 2020 8:43 pm
Forum: Balancing Redox Reactions
Topic: Redox in Acid/ Basic Solutions
Replies: 8
Views: 86

Re: Redox in Acid/ Basic Solutions

The main difference comes from how you balance the equation. For basic solutions, you would balance out the equation by adding hydroxide ions (OH-). For acidic solutions, you would balance out the equation by adding protons (H+).
by Andres Merlos 2L
Sun Feb 16, 2020 3:28 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equilibrium
Replies: 5
Views: 58

Re: Equilibrium

Delta G is 0 at equilibrium, but delta S and delta H could be nonzero in order for delta G to be 0. This is as long as the equation results in 0.
by Andres Merlos 2L
Sun Feb 16, 2020 3:27 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equilibrium
Replies: 15
Views: 137

Re: Equilibrium

Neither reverse nor forward reaction is favored at equilibrium, so at delta G naught 0, the reaction is neither spontaneous nor non-spontaneous. This would mean neither reaction is favored, so it would be at equilibrium.
by Andres Merlos 2L
Sun Feb 16, 2020 3:23 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free energy concept
Replies: 16
Views: 195

Re: Gibbs Free energy concept

Gibbs Free Energy is the amount of energy available to do work. A negative value would indicate spontaneity. A positive value would indicate non-spontaneity.
by Andres Merlos 2L
Sun Feb 16, 2020 3:16 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Why are exothermic reactions generally spontaneous?
Replies: 16
Views: 225

Re: Why are exothermic reactions generally spontaneous?

This is mainly because a reaction that is spontaneous would not require heat input. They release energy upon completion.
by Andres Merlos 2L
Sun Feb 16, 2020 3:13 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: maximum work
Replies: 5
Views: 86

Re: maximum work

Maximum work refers to work done by a system during a reversible reaction. As such, maximum work, when none is lost as heat, would be theoretical.
by Andres Merlos 2L
Sun Feb 09, 2020 12:45 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Molar Entropy
Replies: 4
Views: 47

Re: Molar Entropy

Molar entropy is the entropy content of 1 mole of a substance. Entropy is the degree of disorder, or the energy unavailable for doing work.
by Andres Merlos 2L
Sun Feb 09, 2020 12:43 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Energy Change
Replies: 4
Views: 34

Re: Energy Change

A spontaneous reaction is favorable, and this occurs when deltaG is negative. It will proceed forward because of this.
by Andres Merlos 2L
Sun Feb 09, 2020 12:42 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous Reaction
Replies: 8
Views: 56

Re: Spontaneous Reaction

Yes, when the deltaG is negative, this gives a spontaneous and more favorable reaction.
by Andres Merlos 2L
Sun Feb 09, 2020 12:40 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: gibbs free energy of formation
Replies: 3
Views: 43

Re: gibbs free energy of formation

If Gibbs Free Energy is negative, it is more stable because it refers to spontaneity of a reaction. Spontaneous reactions tend to yield more stable products as they are not "forced" to undergo a reaction, in contrast to a non-spontaneous reaction.
by Andres Merlos 2L
Sun Feb 09, 2020 12:36 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy
Replies: 4
Views: 82

Re: Gibbs free energy

Gibbs free energy is the energy in a chemical reaction that can be used to do work. Since enthalpy is the total heat content of a system, you would subtract entropy, which is the unavailable energy that is used for work, with temperature. This gives us the energy that can be used for work.
by Andres Merlos 2L
Sun Feb 02, 2020 6:16 pm
Forum: Calculating Work of Expansion
Topic: Work positive or negative
Replies: 5
Views: 57

Re: Work positive or negative

If the system is doing work, you would have a negative value because energy is being used. This is because the system loses something, energy, resulting in the negative value we see. If work is being done on the system, you would receive a positive value because the energy is directed towards the sy...
by Andres Merlos 2L
Sun Feb 02, 2020 6:14 pm
Forum: Calculating Work of Expansion
Topic: Reversible Process
Replies: 2
Views: 40

Re: Reversible Process

Yes, a constant pressure accounts for an irreversible reaction. A reversible reaction, in that case, could have a non-constant pressure.
by Andres Merlos 2L
Sun Feb 02, 2020 5:50 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Pressure in an open beaker
Replies: 12
Views: 103

Re: Pressure in an open beaker

An open beaker system allows the exchange of pressure between its surroundings and the system. Since the atmosphere is relatively large, the pressure of the beaker will not have an effect on it, almost like a drop-in-the-bucket type deal. We can then infer a constant pressure because of this.
by Andres Merlos 2L
Sun Feb 02, 2020 5:47 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs isolated systems
Replies: 24
Views: 198

Re: Closed vs isolated systems

A closed system cannot exchange matter with its surroundings, but it can exchange energy. An isolated system cannot exchange matter or energy.
by Andres Merlos 2L
Sun Feb 02, 2020 5:42 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: entropy?
Replies: 4
Views: 63

Re: entropy?

Entropy is a degree of disorder. We need both the change in entropy and the change in internal energy to be able to fully describe how a system will change. We need entropy because its degree would allow us to determine how spontaneous something is.
by Andres Merlos 2L
Sun Jan 26, 2020 4:41 pm
Forum: Phase Changes & Related Calculations
Topic: phase changes
Replies: 6
Views: 56

Re: phase changes

The exothermic phase changes we are currently discussing are condensation, freezing, and deposition. The endothermic phase changes are vaporization, melting, and sublimation.
by Andres Merlos 2L
Sun Jan 26, 2020 4:35 pm
Forum: Phase Changes & Related Calculations
Topic: Phase changes: endothermic vs exothermic
Replies: 12
Views: 169

Re: Phase changes: endothermic vs exothermic

Yes, it is important to note that the reverse of those reactions are condensation, freezing, and deposition, respectively. Condensation, freezing, and deposition are bond forming, which is why they would be exothermic. Bond breaking, on the other hand, would include vaporization, melting, and sublim...
by Andres Merlos 2L
Sun Jan 26, 2020 4:31 pm
Forum: Phase Changes & Related Calculations
Topic: State property
Replies: 6
Views: 55

Re: State property

A state property "is not dependent on path taken to obtain that state." Examples would include E(nergy), P(ressure), V(olume), T(emperature), Density, and Heat Capacity.
by Andres Merlos 2L
Sun Jan 26, 2020 4:28 pm
Forum: Phase Changes & Related Calculations
Topic: What is a state function?
Replies: 3
Views: 48

What is a state function?

So from the lecture, there is a point that enthalpy is a state function, therefore it must be additive, but I'm not quite sure what a state function is. Can anyone explain?
by Andres Merlos 2L
Sun Jan 26, 2020 4:20 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Lewis Structures Method 2
Replies: 6
Views: 55

Re: Lewis Structures Method 2

It is useful to draw out the lewis structures when attempting to visualize the forming and breaking of bonds in the products or reactants. It's not necessary, but it does give you some peace of mind to justify reasoning.
by Andres Merlos 2L
Sun Jan 19, 2020 1:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Difference between K and Q?
Replies: 11
Views: 102

Re: Difference between K and Q?

They look very similar because the only difference between the two constants is when you should use them. You use K when the reaction is at equilibrium, and you use Q at any stage of the reaction. You can compare the two constants to determine which way the reaction is shifting.
by Andres Merlos 2L
Sun Jan 19, 2020 1:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acids and Bases Ice Box
Replies: 5
Views: 55

Re: Acids and Bases Ice Box

Alison Trinh 1E wrote:What is the purpose of an ICE Box?


It is a step-by-step procedure that is used to put concentrations in terms of x, which you can then solve using approximation or the quadratic formula. You can then find a various amount of information with x such as KA, pH, etc.
by Andres Merlos 2L
Sun Jan 19, 2020 1:10 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure
Replies: 5
Views: 41

Re: Pressure

It depends entirely on the number of moles on the different sides of the equation. An increase in pressure will favor the side with less gaseous moles.
by Andres Merlos 2L
Sun Jan 19, 2020 1:05 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.5
Replies: 2
Views: 21

Re: 5J.5

I got the same answer as well. There was no change for d because both sides of the equation have the same number of gaseous moles.
by Andres Merlos 2L
Sun Jan 19, 2020 1:00 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5% rule
Replies: 10
Views: 109

Re: 5% rule

The 5% rule generally applies to approximation when trying to find x, after performing an ICE table. Instead of using the quadratic formula, you can disregard x relative to the initial if what you get from the approximation is less than 5% of the initial value. The procedure to finding that value is...
by Andres Merlos 2L
Sat Jan 11, 2020 4:14 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction quotient
Replies: 8
Views: 73

Re: Reaction quotient

Q is the reaction quotient, which can be used anytime during a reaction dealing with gases. K is the equilibrium constant, so it can only be calculated once the reaction is at equilibrium.
by Andres Merlos 2L
Sat Jan 11, 2020 4:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K values
Replies: 4
Views: 57

Re: K values

If K=1, that would mean the amount of products and reactants are equal. This is rare because the forward and reverse reactions would have to reach equilibrium at this intermediate value.
by Andres Merlos 2L
Sat Jan 11, 2020 4:00 pm
Forum: Ideal Gases
Topic: Solids and liquids [ENDORSED]
Replies: 6
Views: 73

Re: Solids and liquids [ENDORSED]

Since liquids are considered a pure substance, the molar concentration would not change in a reaction. We do not consider them in the equilibrium constant because of this.
by Andres Merlos 2L
Sat Jan 11, 2020 3:56 pm
Forum: Ideal Gases
Topic: R in PV=nRT
Replies: 34
Views: 666

Re: R in PV=nRT

R refers to the gas constant which depends on the units you are using for your equation.
by Andres Merlos 2L
Sat Jan 11, 2020 3:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.1 [ENDORSED]
Replies: 4
Views: 51

Re: 5G.1 [ENDORSED]

So for this exercise, you have to determine which statements are true or false. If I am correct, you are referring to part c of 5G.1. The statement that if you start with a higher pressure of reactant, the equilibrium will be larger, is false.

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