## Search found 30 matches

Tue Mar 13, 2018 4:20 pm
Forum: Phase Changes & Related Calculations
Topic: Test #1
Replies: 4
Views: 368

### Re: Test #1

Yes, because going from liquid to gas, heat must be transferred, and looking at a heating curve I think heat is supplied because heat must be supplied for a liquid to turn into a gas.
Tue Mar 13, 2018 4:16 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test 2 #6b
Replies: 2
Views: 194

### Re: Test 2 #6b

The Ag in AgF has a charge of +1, and it goes to Ag, whose charge is 0. Therefore it gains an electron (reduction) so AgF would be an oxidizing agent.
Tue Mar 13, 2018 4:12 pm
Forum: Balancing Redox Reactions
Topic: Test 2 #1
Replies: 6
Views: 448

### Re: Test 2 #1

I think O2 is reduced because the charge on the oxygens in O2 is both 0, because that is a neutral molecule. Therefore each gains two electrons (reduction) because the oxygens in CO2 are both -2.
Fri Mar 09, 2018 9:20 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: oxidizing power
Replies: 2
Views: 199

### Re: oxidizing power

The reduction potential is how likely the substance is going to be reduced, so if the reduction potential is greater it also means that it is more likely to oxidize the other substance.
Fri Mar 09, 2018 9:18 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Elementary Reactions Differential Rate Law
Replies: 2
Views: 161

### Re: Elementary Reactions Differential Rate Law

We can't find the rate law for a complete reaction because we don't know the whole process the reaction took to reach the final products. Unlike for thermodynamics, kinetics is not a state property, so the path it takes counts. Therefore it must be broken up into elementary steps.
Fri Mar 09, 2018 3:23 pm
Forum: First Order Reactions
Topic: 15.37C
Replies: 5
Views: 696

### Re: 15.37C

I think it would be safer to use the volume and use the molarity every time, so that you can avoid making mistakes in the future.
Mon Feb 26, 2018 9:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: changing sign of of standard cell potentials
Replies: 4
Views: 286

### Re: changing sign of of standard cell potentials

Yes, because the reverse half reaction of the reduction reaction that you are looking for is the oxidation reaction. Therefore you want the e- to be on the opposite side.
Mon Feb 26, 2018 9:09 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Slowest Elementary Step
Replies: 4
Views: 498

### Re: Slowest Elementary Step

Because in a reaction, multiple steps are happening simultaneously so the step that takes the longest determines the time it takes overall.
Mon Feb 26, 2018 9:06 pm
Forum: Experimental Details
Topic: Collision Theory
Replies: 2
Views: 542

### Re: Collision Theory

Yes, also because in the other phases such as in liquid, the molecules simply slide by each other, not necessarily colliding. In solid phases, the molecules simply vibrate in place.
Mon Feb 26, 2018 9:04 pm
Forum: General Rate Laws
Topic: Examples
Replies: 3
Views: 230

### Re: Examples

Also as discussed in class, radioactive decay is a first-order reaction.
Mon Feb 26, 2018 9:03 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: log (Q)
Replies: 2
Views: 282

### Re: log (Q)

I think if you mean that if Q <1 then log[Q] will be negative and that if Q>1 then log [Q] will be positive, and yes that is true.
Mon Feb 26, 2018 9:00 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Units for Concentration
Replies: 4
Views: 262

### Re: Units for Concentration

Yes, I don't think it matters because you aren't using constants with fixed units and if you are consistent with what you're working with it should be fine.
Fri Feb 16, 2018 3:44 pm
Forum: Balancing Redox Reactions
Topic: Salt Bridge Versus Pourous Disk
Replies: 6
Views: 411

### Re: Salt Bridge Versus Pourous Disk

A porous disk allows exchange of ions (so the concentrations can reach equilibrium) while through a salt bridge only electrons can transfer.
Fri Feb 16, 2018 3:41 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic vs Concentration
Replies: 3
Views: 224

### Re: Galvanic vs Concentration

A galvanic cell means that there's a rxn taking place at the surface of electrodes between an anode and a cathode. A concentration cell means that the components in the anode and cathode are the same compounds/elements. In either case they are spontaneous.
Fri Feb 16, 2018 3:38 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Lecture Example
Replies: 2
Views: 158

### Re: Lecture Example

E cell is positive because there is a log (0.1/1.0), which equals -1.
If you solve the equation, this -1 cancels out the negative in the equation, making it positive.
Fri Feb 09, 2018 12:08 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Entropy
Replies: 7
Views: 375

### Re: Entropy

I'm not exactly sure because you didn't give context, but S^0 m is most likely entropy for the melting point, r is for reactants and f is for final.
Fri Feb 09, 2018 12:06 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode and cathode
Replies: 9
Views: 424

### Re: Anode and cathode

Generally the anode will be on the left and the cathode is on he right. Also, the anode will have a (-) and a cathode will have a (+).
Fri Feb 09, 2018 12:04 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Intensive Property of Standard Cell Potential
Replies: 3
Views: 235

### Re: Intensive Property of Standard Cell Potential

The heat capacity is the one that is extensive, and specific heat capacity is actually intensive. By "cell potential" are you referring to the standard reduction potential (Eo)? Because if so, the reason why you wouldn't change the Eo is because that is the voltage difference between the t...
Thu Feb 01, 2018 9:38 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy change
Replies: 4
Views: 242

### Re: Entropy change

The reaction is spontaneous if the change in entropy of the universe is positive, and this is the sum of the entropy of the system and the surroundings.
Thu Feb 01, 2018 9:36 am
Forum: Phase Changes & Related Calculations
Topic: Phase Change Diagrams: Slopes
Replies: 2
Views: 169

### Re: Phase Change Diagrams: Slopes

The slope of the heating curve is the heat capacity of each phase. For example, the slope of the line of fusion (between ice and water) is the heat capacity of solid water).
Wed Jan 31, 2018 2:01 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Class Example
Replies: 6
Views: 246

### Re: Class Example

That would not be the final answer, because that is when liquid and gas phase both coexist. Therefore the answer is any temp >333K.
Wed Jan 24, 2018 3:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law [ENDORSED]
Replies: 7
Views: 420

### Re: Hess's Law[ENDORSED]

I'm sure it will depend on the question, but I think most questions will give us the reactions with the reaction enthalpies.
Wed Jan 24, 2018 3:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework 8.55
Replies: 2
Views: 114

### Re: Homework 8.55

In case you haven't noticed, 8.55 is not included in the assigned problems of chapter 8
Wed Jan 24, 2018 3:30 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: qp=deltaH
Replies: 2
Views: 3196

### Re: qp=deltaH

qp=delta H because the definition of enthalpy (H) is the amount of heat released/absorbed at a constant pressure. Therefore, q, being heat, equals delta H
Fri Jan 19, 2018 3:47 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Difference between Closed and Isolated
Replies: 10
Views: 1267

### Re: Difference between Closed and Isolated

For example you can heat up a beaker with a lid on it (closed system) and the contents will become warmer, but you can't heat up the contents of an isolated system such as a thermos bottle.
Fri Jan 19, 2018 3:46 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: First law potential energy
Replies: 1
Views: 125

### First law potential energy

I was reading the textbook and came across one of the thinking points in 8.6. This is about a piston that's moving outward, increasing the volume of the ideal gas. It's asking why there's no potential energy change in an isothermal expansion, even when the molecules are moving apart (hence expansion...
Fri Jan 19, 2018 3:28 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Open systems
Replies: 6
Views: 392

### Re: Open systems

Yes I think we will, although not as much as closed systems. For example an open beaker is an open system.
Wed Jan 10, 2018 10:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Equation for a non-state property?
Replies: 4
Views: 213

### Re: Equation for a non-state property?

In a sense it is like finding the total distance traveled by a particle. You add up all the distances (changes) it undergoes and add them together, disregarding negatives.
Wed Jan 10, 2018 10:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Equations
Replies: 6
Views: 359

### Re: Equations

Enthalpy of vaporization = enthalpy of vapor - enthalpy of liquid
Enthalpy of fusion = enthalpy of liquid - enthalpy of solid
Wed Jan 10, 2018 10:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Conceptualizing enthalpy
Replies: 2
Views: 234

### Re: Conceptualizing enthalpy

Q/p is the heat of the system, or the heat required/generated by the formation or breaking of the bonds. The pressure must be constant because according to the ideal gas law, if one part of the system, such as pressure, changes, temperature can also change.