Search found 30 matches

by Cynthia Bui 2H
Sat Mar 17, 2018 5:39 pm
Forum: Balancing Redox Reactions
Topic: Test 2 #1
Replies: 6
Views: 330

Re: Test 2 #1

O2 by itself has a charge of 0 but in a compound/molecule you consider how O's charge is 2- so it goes from 0 to 4- charge.
by Cynthia Bui 2H
Sat Mar 17, 2018 5:35 pm
Forum: Balancing Redox Reactions
Topic: Eletro chem Test
Replies: 4
Views: 258

Re: Eletro chem Test

I'm not quite sure if this is what you wanted but if for the second one its from H3O+ to O2, then the O is going from 1+ to 0, so it would be reduced and the oxidizing agent.
by Cynthia Bui 2H
Sat Mar 17, 2018 5:33 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolysis
Replies: 2
Views: 621

Re: Electrolysis

Yes, electrolysis is when an electric current is used to drive a non spontaneous reaction which is often when e- need to flow towards the anode for this to occur. The current is simply directed towards the anode (or site w lower E cell) to provide the right energy.
by Cynthia Bui 2H
Sat Mar 17, 2018 5:26 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolysis
Replies: 5
Views: 704

Re: Electrolysis

Electrons provide the activation energy that is normally too high for the reaction to be spontaneous.
by Cynthia Bui 2H
Sat Mar 17, 2018 5:25 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test #2 Question 5
Replies: 5
Views: 208

Re: Test #2 Question 5

In terms of their oxidizing power, it means that the more it will take e- the stronger its oxidizing power, so the greater and more positive E is the greater it's oxidizing power.
by Cynthia Bui 2H
Sat Mar 17, 2018 5:20 pm
Forum: Balancing Redox Reactions
Topic: Reducing and oxidizing agents
Replies: 1
Views: 180

Re: Reducing and oxidizing agents

The reducing agent is the one that causes another molecule to be reduced, meaning the other molecule GAINS an electron and the reducing agent is the one that gave an electron (or more) up. So, looking at AgF, for it to be neutral, Ag had to be 1+ and it shows when they separate, Ag is neutral, so it...
by Cynthia Bui 2H
Sat Mar 17, 2018 5:16 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: State functions?
Replies: 9
Views: 426

Re: State functions?

They're both state functions. Because of that you can add their quantities together to get a total or final entropy or enthalpy.
by Cynthia Bui 2H
Sat Mar 17, 2018 5:10 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: reversible system
Replies: 9
Views: 425

Re: reversible system

deltaS total = 0
by Cynthia Bui 2H
Sat Mar 17, 2018 5:09 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Difference between calculations
Replies: 1
Views: 188

Re: Difference between calculations

I don't think there is one. It mainly depends on the numbers you have available to you.
by Cynthia Bui 2H
Sat Mar 17, 2018 5:07 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: S=klnW
Replies: 7
Views: 1098

Re: S=klnW

This is total entropy, not change in entropy which is what we normally tend to calculate. You would use this when given a number of molecules and the possible orientations they can lay in and such. For example if a solid had 64 molecules and the molecules can like in any 4 directions, W= 4^64
by Cynthia Bui 2H
Sat Mar 17, 2018 11:51 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: mass in q = m(c) delta t
Replies: 5
Views: 410

Re: mass in q = m(c) delta t

Depends on the heat capacity you use. Always write out your units to make sure you're using the right value!
by Cynthia Bui 2H
Sat Mar 17, 2018 11:48 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Step in Reaction Mechanisms
Replies: 7
Views: 302

Re: Slow Step in Reaction Mechanisms

If the slow step is first, the reaction is determined by the slow step but if it is second, you use the pre-equilibrium steps we learned.
by Cynthia Bui 2H
Sat Mar 17, 2018 11:46 am
Forum: Zero Order Reactions
Topic: graph of 0 order
Replies: 10
Views: 474

Re: graph of 0 order

The line would be parallel to the x-axis.
by Cynthia Bui 2H
Sat Mar 17, 2018 11:45 am
Forum: First Order Reactions
Topic: Negative Orders
Replies: 5
Views: 267

Re: Negative Orders

A reaction can be negative with respect to one reactant but I don't think all reactants can have a negative order. The overall order for a reaction has to be at least 0.
by Cynthia Bui 2H
Sat Mar 17, 2018 11:43 am
Forum: First Order Reactions
Topic: Slope of 1st order RXNs
Replies: 9
Views: 429

Re: Slope of 1st order RXNs

Slope is -K, a downward sloping graph.
by Cynthia Bui 2H
Sat Mar 17, 2018 11:42 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Bomb Calorimeter
Replies: 6
Views: 403

Re: Bomb Calorimeter

No, they're not considered vacuums.
by Cynthia Bui 2H
Fri Mar 16, 2018 9:39 pm
Forum: *Alkanes
Topic: Final
Replies: 13
Views: 1180

Re: Final

Yeah, he had this one slide with their names that you had to identify. They were alcohol, ether, aldehyde, ketone, carboxylic acid, and amine.
by Cynthia Bui 2H
Fri Mar 16, 2018 9:35 pm
Forum: Photoelectric Effect
Topic: Test 2, #7a
Replies: 2
Views: 194

Re: Test 2, #7a

Any energy that is not used to eject the electron (assuming the photon's energy is above the threshold) goes towards the electron's kinetic energy. So, normally, KE = Photon's E - threshold E, but you just need to rearrange to get the threshold energy.

Threshold = Photon's E - KE
by Cynthia Bui 2H
Fri Mar 16, 2018 9:15 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Finding n
Replies: 15
Views: 761

Re: Finding n

n = number of electrons
by Cynthia Bui 2H
Thu Feb 01, 2018 10:33 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: phase change change in entropy
Replies: 2
Views: 87

Re: phase change change in entropy

We can change q to deltaH because in reversible situations, the change in potential thermal energy IS the amount of heat transferred. Even though they are different things in these cases they are equivalent.
by Cynthia Bui 2H
Thu Feb 01, 2018 10:30 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: what exactly is free energy?
Replies: 5
Views: 212

Re: what exactly is free energy?

Like everyone's said, it's the energy available to do work. So when it change in G is negative, the reaction is spontaneous because that means there was enough energy to complete the reaction after accounting for changes in entropy.
by Cynthia Bui 2H
Thu Feb 01, 2018 10:25 am
Forum: Environment, Fossil Fuels, Alternative Fuels
Topic: Concept of "Cold"
Replies: 4
Views: 951

Re: Concept of "Cold"

You feel cold when heat is flowing out of you and feel warm/hot when heat is flowing into you (say your hand when you hold a hot cup of tea). The temperature decreases when you add ice because heat is being transferred into the ice away from the liquid, lowering the temperature of the liquid.
by Cynthia Bui 2H
Thu Feb 01, 2018 10:22 am
Forum: Biological Examples (*DNA Structural Transitions, etc.)
Topic: Heat Capacity [ENDORSED]
Replies: 4
Views: 856

Re: Heat Capacity [ENDORSED]

The more degrees of freedom a molecule has the higher its heat capacity.
by Cynthia Bui 2H
Thu Feb 01, 2018 10:17 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Celsius or Kelvin
Replies: 5
Views: 183

Re: Celsius or Kelvin

Definitely Kelvin.
by Cynthia Bui 2H
Thu Feb 01, 2018 10:15 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm
Replies: 6
Views: 233

Re: Midterm

From what I know, the content from Outline 1 and Outline 2 on his website will be covered in the midterm. No electrochemistry.
by Cynthia Bui 2H
Thu Feb 01, 2018 10:11 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Lunchbox?
Replies: 3
Views: 186

Lunchbox?

Would an insulated lunchbox be an isolated system? Curious because I misread the test question as a "pack" being a lunch pack/box instead of an... actual cold pack. Whoops.
by Cynthia Bui 2H
Sat Jan 20, 2018 9:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Pressure's Relationship with Volume
Replies: 2
Views: 111

Re: Pressure's Relationship with Volume

And to expand on what Sungyoon said, the system does not want to change. It wants to stay at a certain equilibrium of conditions, so when the volume is decreased, the temperature will decrease so that the pressure remains constant. By decreasing the temp, the molecules will collide at the same rate ...
by Cynthia Bui 2H
Sat Jan 20, 2018 9:31 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy
Replies: 2
Views: 117

Re: Enthalpy

The change in enthalpy isn't the change in heat without work, it refers to the transfer of heat at a constant pressure, which implies that work is being done. Enthalpy is the total energy content of a system so the change in enthalpy is equal to the change in internal energy due to transfer of heat ...

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