## Search found 29 matches

Mon Mar 12, 2018 6:37 pm
Forum: General Rate Laws
Topic: HW 15.55
Replies: 1
Views: 112

### Re: HW 15.55

This comes down to the equation for equillibrium constant K. K=\frac{k}{k{}'} Where k is the rate constant for the forward reaction and k' is the rate constant for the reverse reaction. When k is larger it creates an overall larger K. However, if k' was larger, since its in the denominator it wo...
Mon Mar 12, 2018 6:26 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Step in Reaction Mechanisms
Replies: 7
Views: 2338

### Re: Slow Step in Reaction Mechanisms

If i read it correctly Johann was also trying to ask what happens when the first reaction is a slow, but it is not the slow step: Do we treat as a pre-equilibrium because it is relatively "fast"
or can we not assume this?
Mon Mar 12, 2018 6:18 pm
Forum: Reaction Mechanisms, Reaction Profiles
Replies: 1
Views: 120

As far as I am aware it was stated that we do not need to know steady state approximation to determine rate law on this final. However, we will need to know how to use the pre-equilibrium condition and how to find rate law with it.
Mon Mar 12, 2018 6:15 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-equiliibrium?
Replies: 3
Views: 260

### Re: Pre-equiliibrium?

Looking more into it a simple way to think about it is that the first step is producing so much intermediate that the rate determining step (slow step) cannot keep up, resulting in a sort of equilibrium taking place within the first step, where the extra intermediate is being formed and then turned ...
Mon Mar 12, 2018 6:07 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-equiliibrium?
Replies: 3
Views: 260

### Re: Pre-equiliibrium?

Pre-equilibrium is when the reactants and intermediates are in equilibrium. We are assuming that the consumption of the intermediate in the slow step is insignificant relative to its rate of formation/decomposition in the first step.
Mon Mar 12, 2018 4:55 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Functional Groups
Replies: 7
Views: 1026

### Re: Functional Groups

According to chem_mod on another post about functional groups on the final we should be able to identify the functional groups given the structure like we did in lecture today.
Mon Mar 12, 2018 12:55 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Michelis-Menten Mechanism?
Replies: 2
Views: 158

### Re: Michelis-Menten Mechanism?

Yes, it helps us understand the changes in concentration of the enzymes and substrates overtime. Specifically it points out the concept of saturation and how the during an enzyme-substrate reaction the rate switches "dependency" as the ratio of enzyme to substrate changes. When there is lo...
Mon Mar 12, 2018 12:45 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy Temperature Dependence
Replies: 5
Views: 629

### Re: Activation Energy Temperature Dependence

Adding on: Although it is mostly independent, what you did point does happen to a certain extent which is why the book states "Both A and Ea are nearly independent"
Mon Mar 12, 2018 12:40 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy Temperature Dependence
Replies: 5
Views: 629

### Re: Activation Energy Temperature Dependence

Activation energy is technically the minimum amount of Kinetic Energy needed for a a collision to result in a reaction (according to the collision theory). The higher the temperature the more Kinetic energy is present meaning the higher the likelihood we will reach this level and end up with a react...
Mon Mar 12, 2018 12:25 pm
Forum: *Enzyme Kinetics
Topic: Catalysts
Replies: 11
Views: 925

### Re: Catalysts

Yes, catalysts speed up both the forward and reverse reactions. This is why the catalyst does not effect the equilibrium composition even though it is changing the rate of the reaction.
Sun Mar 11, 2018 10:42 pm
Forum: *Enzyme Kinetics
Topic: Two Paths
Replies: 5
Views: 795

### Re: Two Paths

Yes there are multiple paths, the original reaction may still continue next to the catalyzed reaction but the rate is determined by the faster path (as it governs the overall rate of formation of products). The slow rate determining elementary reaction will not control the rate if it can go through ...
Sun Mar 11, 2018 10:36 pm
Forum: *Enzyme Kinetics
Topic: Kinetics and Enzymes
Replies: 7
Views: 741

### Re: Kinetics and Enzymes

Chemical Kinetics is the study of the rate and process in which the reaction takes place, therefore as enzymes are biological catalysts that will speed up reactions, understanding how they affect reactions is important to understanding kinetics. They will speed up reactions when they are activated b...
Sat Feb 24, 2018 4:16 pm
Forum: Balancing Redox Reactions
Topic: Balancing number of electrons
Replies: 10
Views: 535

### Re: Balancing number of electrons

Yes, there is no need to go higher than the least common multiple because the sole goal is to just cancel them out. Furthermore, we want to keep the reaction as a whole in its simplest form as it is a representation, so to have extra molecules in this equation will be superfluous.
Sat Feb 24, 2018 4:03 pm
Forum: Balancing Redox Reactions
Topic: 14.5 a)
Replies: 5
Views: 282

### Re: 14.5 a)

As they said before it is because the reaction is taking place in a basic solution. If that is confusing to add OH- what you can do is go through the problem normally, like add H+, balancing out the Hs and then at the end of the problem you just add one OH- on each side for every H+. Then you combin...
Sat Feb 24, 2018 2:55 pm
Forum: Balancing Redox Reactions
Topic: Writing and Balancing Half Reactions
Replies: 6
Views: 444

### Re: Writing and Balancing Half Reactions

https://youtu.be/v5sDNmYCaqo

I got those steps from this video, it really helped me understand it better
Sat Feb 24, 2018 2:53 pm
Forum: Balancing Redox Reactions
Topic: Writing and Balancing Half Reactions
Replies: 6
Views: 444

### Re: Writing and Balancing Half Reactions

1) Determine Oxidation Numbers 2) Figure out the changes in oxidation 3) Write out the half-reactions 4) Balance the reactions a) Balance the atoms other than H and O b) Add H2O to balance O, and H+ to balance H c) Balance the charges with e- e) Multiply half-reactions to make e- equal on both sides...
Sat Feb 24, 2018 2:46 pm
Forum: Balancing Redox Reactions
Topic: 14.5 part d
Replies: 7
Views: 397

### Re: 14.5 part d

I was confused about this, too. Wouldn't adding H+ ions indicate that the reaction is taking place in an acidic solution rather than a basic solution, though? Yeah I was confused about this process too but all you need to do is balance with the H+ and then to make it so it takes place in a Basic so...
Sat Feb 24, 2018 2:40 pm
Forum: Balancing Redox Reactions
Topic: Half Reaction Order
Replies: 9
Views: 2160

### Re: Half Reaction Order

Mathematically it may not matter, however, it would be more correct to keep the equations true to whether it is being reduced or oxidized. Furthermore, it would help you better keep track of what is occurring in a reaction so you can answer any concept related questions more efficiently.
Sun Jan 28, 2018 10:35 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity
Replies: 8
Views: 562

### Re: Heat Capacity

The reason that a greater slope equals a lower heat capacity is because if you think about it, a lower heat capacity means it can hold less heat comfortably. Therefore, any heat added would effect the substance more rapidly than one that had a higher capacity for it, causing it to have a higher rate...
Sun Jan 28, 2018 9:48 pm
Forum: Phase Changes & Related Calculations
Topic: The universe
Replies: 9
Views: 511

### Re: The universe

The universe is an isolated system because neither matter or energy can be exchanged/transferred in or out. Yes, there are no rigid walls or insulation but it is still considered an isolated system as the most important definition is that matter and energy cannot be exchanged. The universe includes ...
Sun Jan 28, 2018 9:44 pm
Forum: Phase Changes & Related Calculations
Topic: Endothermic or Exothermic
Replies: 20
Views: 862

### Re: Endothermic or Exothermic

Condensation is exothermic. One reason we know this is because its counterpart phase change is vaporization and vaporization is endothermic. A more direct reason would be that in condensation the particles are beginning to move a lot slower, vibrate a lot less and more hydrogen bonds are forming. Th...
Sun Jan 21, 2018 10:27 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.77
Replies: 1
Views: 89

### 8.77

In this question, what determines which molecule has lower molar energy? How do bond energies relate to molar energy?
Sun Jan 21, 2018 10:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.77
Replies: 2
Views: 181

### 8.77

In this question, what determines which molecule has lower molar energy? How do bond energies relate to molar energy?
Sun Jan 21, 2018 10:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat of Combustion & Heat of Formation
Replies: 3
Views: 218

### Re: Heat of Combustion & Heat of Formation

The rxn enthalpy allows us to find change in enthalpy of rxns that go from one standard state to another standard state. Combustion enthalpies give us the change in enthalpy per mole for combustion reactions. And enthalpy of formation gives us the rxn enthalpy per mole for the i tidal formation of a...
Sun Jan 21, 2018 9:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat of Combustion & Heat of Formation
Replies: 3
Views: 218

### Re: Heat of Combustion & Heat of Formation

The rxn enthalpy allows us to find change in enthalpy of rxns that go from one standard state to another standard state. Combustion enthalpies give us the change in enthalpy per mole for combustion reactions. And enthalpy of formation gives us the rxn enthalpy per mole for the i tidal formation of a...
Sun Jan 21, 2018 9:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: bond enthalpies
Replies: 3
Views: 242

### Re: bond enthalpies

We have to consider it in a gas form because bond enthalpy is the dissociation of a species in its gas phase. Therefore we have to use the vaporization or sublimation values because that is how liquids and solids become gases respectively
Sun Jan 14, 2018 11:54 pm
Forum: Phase Changes & Related Calculations
Topic: Temperature during phase change
Replies: 2
Views: 140

### Re: Temperature during phase change

The reason it remains constant during a phase change is because the energy is being used to break or form bonds, therefore, none of the energy is being used to increase the overall kinetic energy of the system. Once the phase change is complete the added heat or energy can now start applying towards...
Sun Jan 14, 2018 11:41 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: work vs heat
Replies: 4
Views: 196

### Re: work vs heat

Those two equations are separate in the sense that Delta U = q is saying "change in internal energy equals heat when heat is transferred and everything else stays the same" and then Delta U = w is saying "change in internal energy equals work when work done is the only thing changing....
Sun Jan 14, 2018 11:11 pm
Forum: Phase Changes & Related Calculations
Topic: Open/Closed/Isolated
Replies: 11
Views: 582

### Re: Open/Closed/Isolated

Liam Maxwell 2E wrote:what actually constitutes the difference between an open and closed system?

In an open system there is a transfer of both mass and heat, but in a closed system there is only a transfer of heat.