## Search found 30 matches

Sat Mar 17, 2018 1:39 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: catalyst
Replies: 4
Views: 316

### Re: catalyst

Some catalysts provide a way for the reacting species to undergo productive collisions more frequently, therefore less energy is needed to initiate the reaction. (Same thing as lowering the activation energy).
Sat Mar 17, 2018 1:37 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Question 14.41
Replies: 6
Views: 325

### Re: Question 14.41

The flow of electrons is not the same as the "flow" of the Cu2+. The electrons will flow towards the side with higher concentration of Cu2+ so that the copper ions there can get reduced to form Cu(s) and therefore reducing the concentration of Cu2+ in that cell.
Sat Mar 17, 2018 1:34 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: reversible system
Replies: 2
Views: 253

### Re: reversible system

Yes because whatever entropy the system loses is gained by the surroundings, so the entropy change of the universe is zero.
Fri Mar 09, 2018 5:59 pm
Forum: First Order Reactions
Topic: Log vs ln
Replies: 9
Views: 509

### Re: Log vs ln

Use ln, ln is used in the integrated law for a reason because it makes life easier for you. If you convert it to log then you 'll go through an extra step that you never needed to do in the first place.
Fri Mar 09, 2018 5:57 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 5
Views: 216

### Re: Catalysts

Since the rate of reaction and also activation energy depends on successful collision of molecules in the correct orientation, we can think of catalysts as things that helps the reactants collide more frequently in the correct orientation. Some catalyst such as many metals actually allow reactants t...
Fri Mar 09, 2018 5:54 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation [ENDORSED]
Replies: 7
Views: 286

### Re: Arrhenius Equation[ENDORSED]

Whenever you see a kinetics question that involves temperature change, you're most likely gonna use the Arrhenius equation.
Fri Mar 02, 2018 2:50 pm
Forum: First Order Reactions
Topic: Pseudo First Order Reaction
Replies: 5
Views: 544

### Re: Pseudo First Order Reaction

A regular first order reaction is just what it is. A pseudo first order reaction means that the reaction is not actually first order because there are other reactants whose concentration will affect the rate of reaction. However, we can calculate what is the order of reaction for a certain reactant ...
Fri Mar 02, 2018 2:47 pm
Forum: Zero Order Reactions
Topic: Zero Order Reactions in Real Life [ENDORSED]
Replies: 3
Views: 219

### Re: Zero Order Reactions in Real Life[ENDORSED]

Normally we use very little catalyst for a particular reaction. If The entire surface of the catalyst is covered with reacting reactants, then no matter what is the concentration of the reactant, the rate will not increase.
Fri Mar 02, 2018 2:45 pm
Forum: Zero Order Reactions
Topic: Units of k [ENDORSED]
Replies: 13
Views: 436

### Re: Units of k[ENDORSED]

The unit of the rate of reaction is mol•L^-1•S^-1, so you just have to manipulate the unit of K so that when put into the equation will give you mol•L^-1•S^-1.
Fri Feb 23, 2018 3:29 pm
Forum: General Rate Laws
Replies: 6
Views: 1270

Yes because the reactants would be decreasing, to get a positive value for rate of reaction we have to have a negative sign ahead of it.
Fri Feb 23, 2018 3:28 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Diamond and graphite
Replies: 8
Views: 677

### Re: Diamond and graphite

Kinetically stable just means that the reaction from diamond to graphite is too slow to be accounted for normally.
Fri Feb 23, 2018 3:27 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Instantaneous Rate
Replies: 4
Views: 273

### Re: Instantaneous Rate

Knowing the initial rate is also important because it allows us to analyse how the reaction mechanism works and that would help us in understanding the rate of reaction after the initial time.
Fri Feb 16, 2018 3:06 pm
Forum: Balancing Redox Reactions
Topic: Oxidized vs oxidizing agent
Replies: 5
Views: 208

### Re: Oxidized vs oxidizing agent

The species that is oxidized is the reduction agent, the one that is reduced is the oxidizing agent. This is because if something oxidizes another thing, it must be itself reduced, vice versa.
Fri Feb 16, 2018 3:05 pm
Forum: Balancing Redox Reactions
Topic: Salt Bridge Versus Pourous Disk
Replies: 6
Views: 272

### Re: Salt Bridge Versus Pourous Disk

I am of the impression that there is no major difference between the two, I may be wrong though.
Fri Feb 16, 2018 3:04 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Water in cell diagram
Replies: 3
Views: 155

### Re: Water in cell diagram

The above are true but we have to also take note that water dissociates into H+ and OH- ions, during electrolysis, they may be discharged.
Fri Feb 09, 2018 4:09 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Oxidation Numbers
Replies: 4
Views: 468

### Re: Oxidation Numbers

Oxidation numbers of O in a compound is most commonly -2, however, in peroxides like H2O2, the oxidation number of oxygen will be different. In this case, it is -1.
Fri Feb 09, 2018 4:07 pm
Forum: Balancing Redox Reactions
Topic: Basic vs. Acidic
Replies: 6
Views: 202

### Re: Basic vs. Acidic

If the concentration of H+ is very high, it may be preferentially reduced to H2 gas. Remember that the cell potential depends on the concentration of the solution.
Fri Feb 09, 2018 4:04 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Conducting Metal
Replies: 3
Views: 116

### Re: Conducting Metal

I don't think so, some half reactions do not involve conducting metals at all. One such reaction would be the standard hydrogen electrode. Between half reactions though, a wire is needed to transfer the charges from one electrode to the other.
Sat Feb 03, 2018 10:18 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Heat transfer to a liquefied gas.
Replies: 2
Views: 157

### Heat transfer to a liquefied gas.

A gas is liquefied in a container due to high pressure, why is there heat transferred if there is now a hole in the container and the pressurized liquid escapes as a gas?
Sat Feb 03, 2018 10:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous
Replies: 14
Views: 463

### Re: Spontaneous

To add on, spontaneous reactions don't just happen. Spontaneous reactions means that products are at a lower energy level than the reactants. To start the reaction though, you might need activation energy. When the activation energy is supplied, the reaction continues to the end. For example, a spar...
Sat Feb 03, 2018 10:13 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: G at minimum
Replies: 6
Views: 199

### Re: G at minimum

When G is at minimum, the reaction is at equilibrium so the system shouldn't have any tendency to do work spontaneously.
Fri Jan 26, 2018 3:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Examples of work being done
Replies: 7
Views: 333

### Re: Examples of work being done

I think that for the purpose of our class, we can think of work done by a system to be a force pushing against the system. If it's a gas, the work done on a system will most likely cause a contraction of the gas.
Fri Jan 26, 2018 3:35 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Changing the energy of a system
Replies: 6
Views: 267

### Re: Changing the energy of a system

Adding more substance in a system will increase the internal energy of the system, since the added amount of substance will have their own energy, that energy is added to the original system.
Fri Jan 26, 2018 3:32 pm
Forum: Calculating Work of Expansion
Topic: Irreversible expansion
Replies: 4
Views: 160

### Re: Irreversible expansion

Irreversible means that the direction of expansion/contraction will not be changes by a tiny amount of change in external pressure. For example, if the gas of 1 atm is expanding against an external surrounding of 1 atm, if the outside pressure increases even a little bit, the gas will go from expand...
Fri Jan 19, 2018 2:21 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: open system
Replies: 6
Views: 291

### Re: open system

All matter have their own internal energy, removing a unit of matter from a system means removing part of the internal energy that the system has.
Fri Jan 19, 2018 2:18 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: the sign of q and w [ENDORSED]
Replies: 6
Views: 252

### Re: the sign of q and w[ENDORSED]

ΔU= q+w does not necessarily mean that q and w are positive, they can take on negative values as well. The sum of the two, regardless of them being positive or negative will be the change in internal energy of the system.
Fri Jan 19, 2018 2:16 pm
Forum: Calculating Work of Expansion
Topic: units for calculating work
Replies: 6
Views: 153

### Re: units for calculating work

Use for volume and atm for pressure. Even if the question gives you a pressure unit that is not in atm, converting to atm might help make answering easier. The conversion between the various pressure units will be on the formula sheet.
Sun Jan 14, 2018 3:38 pm
Forum: Phase Changes & Related Calculations
Topic: Temperature during Phase Change
Replies: 6
Views: 245

### Re: Temperature during Phase Change

The heat supplied to a substance when the substance is at melting/boiling point will go towards breaking the inter-molecular/atomic bonds. Although there are many kind of bonds between molecules such as H Bonds, London Forces, Ionic bonds etc, all of them are bonds. Breaking of bonds is an endotherm...
Sun Jan 14, 2018 3:32 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Closed System
Replies: 7
Views: 303

### Re: Closed System

In the coil of the fridge no matter exits or enter the system but energy can enter/exit the system. In fact it is the job of the coolant to carry heat out of the fridge in order to cool the inside of the fridge.
Sun Jan 14, 2018 3:28 pm
Forum: Phase Changes & Related Calculations
Topic: Steam Burning
Replies: 7
Views: 330

### Re: Steam Burning

Steam burns more because it has to first condense into liquid water when it comes to contact with your skin. The heat released from the condensation is added to the heat released from cooling the liquid water from 100 degree to your body temperature. So more heat is released by steam at 100 degrees ...