Search found 29 matches
- Sat Mar 17, 2018 2:11 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 8.103
- Replies: 3
- Views: 730
Re: 8.103
(3/2)*R deals with an ideal gas at a constant volume
- Sat Mar 17, 2018 2:10 am
- Forum: Phase Changes & Related Calculations
- Topic: Endothermic/exothermic
- Replies: 4
- Views: 1227
Re: Endothermic/exothermic
Exothermic processes give off heat while endothermic processes absorb heat. It is important to identify which you consider to be the system and which are the surroundings.
- Sat Mar 17, 2018 2:07 am
- Forum: Balancing Redox Reactions
- Topic: Ranking elements
- Replies: 8
- Views: 1189
Re: Ranking elements
By looking at standard reduction potentials, you can determine the reducing or oxidizing power. The more positive the potential, the greater the electron pulling power of the reduction half-reaction which means it is more likely to be reduced.
- Sat Mar 17, 2018 2:05 am
- Forum: First Order Reactions
- Topic: k
- Replies: 16
- Views: 1660
Re: k
Usually the problem will specify a unit of time and we would want to use that same unit of time for K. Otherwise, using units of time as seconds is usually a safe bet.
- Sat Mar 17, 2018 2:03 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Identifying a catalyst in a reaction
- Replies: 4
- Views: 13376
Re: Identifying a catalyst in a reaction
Intermediates will always be consumed while catalysts are not consumed.
- Sat Mar 17, 2018 2:02 am
- Forum: Balancing Redox Reactions
- Topic: Half-Reactions Sheet
- Replies: 5
- Views: 750
Re: Half-Reactions Sheet
We will likely be given the half reactions and the potentials along with them similar to our test.
- Sat Mar 17, 2018 2:01 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibb's Energy and Work
- Replies: 4
- Views: 830
Re: Gibb's Energy and Work
Gibbs free energy does not apply only to nonexpansion work
- Sat Mar 17, 2018 2:00 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 9.1
- Replies: 5
- Views: 952
Re: 9.1
Heat is leaving the body so you regard the body as the "system" and therefore q is negative
- Sat Mar 17, 2018 1:59 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Why is entropy extensive?
- Replies: 5
- Views: 5403
Re: Why is entropy extensive?
Extensive is dependent while intensive is independent
- Sat Mar 17, 2018 1:58 am
- Forum: Balancing Redox Reactions
- Topic: determining cathode from anode
- Replies: 11
- Views: 1939
Re: determining cathode from anode
Calculate cathode - anode substituting both numbers and the combination that gives the most positive output is the correct one
- Fri Mar 16, 2018 7:19 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Finding n
- Replies: 15
- Views: 1901
Re: Finding n
n is the number of electrons
- Fri Mar 16, 2018 7:18 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Standard Gibbs
- Replies: 3
- Views: 766
Re: Standard Gibbs
The sign indicates standard state which means it is taking place under standard conditions (aka 25 degrees Celsius and 1 atm)
- Fri Mar 16, 2018 7:17 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: 3537
Re: S=klnW
Residual enthalpy can be calculated when a reaction is taking place at a very low temperature almost close to 0
- Fri Mar 16, 2018 7:16 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isothermal system
- Replies: 5
- Views: 1259
Re: Isothermal system
The term free expansion implies work is = 0 and in that case q would also be zero as the deltaU value needs to remain 0
- Fri Mar 16, 2018 7:15 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Midterm #6A
- Replies: 2
- Views: 678
Re: Midterm #6A
A was the more precise answer but if you put B, you were given points back.
- Fri Mar 16, 2018 7:14 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: State functions?
- Replies: 9
- Views: 1356
Re: State functions?
It is important to know the difference between state functions and those that aren't state functions. Entropy and enthalpy are state functions while heat and work are not.
- Wed Mar 14, 2018 1:26 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Test 1 #3
- Replies: 4
- Views: 1255
Re: Test 1 #3
since the problem says "same temperature" we can infer it is isothermal which means deltaU is zero. Expansion work is occurring as the balloon grows
- Tue Mar 13, 2018 11:23 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: change in internal energy
- Replies: 3
- Views: 700
Re: change in internal energy
Separating the steps allows us to perform two different calculations which would give us the final correct answer. It is impossible to calculate them simultaneously as there is not an equation we have learned to allow us to deal with both forms of energy change at the same time.
- Tue Mar 13, 2018 11:21 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: The First Law
- Replies: 6
- Views: 991
Re: The First Law
The only way to change the internal energy of a closed system is to transfer energy into it as heat or work
- Tue Mar 13, 2018 11:15 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: enthalpy of sublimation
- Replies: 5
- Views: 969
Re: enthalpy of sublimation
Hsub can also be deltaH(fusion) + deltaH(vaporization)
- Tue Mar 13, 2018 11:14 pm
- Forum: First Order Reactions
- Topic: Help on 15.3
- Replies: 7
- Views: 1099
Re: Help on 15.3
if you convert all given mmol values to mol values and then run the calculation, you should get the correct answer as given in the solutions manual
- Tue Mar 13, 2018 11:12 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow and Fast Steps
- Replies: 2
- Views: 585
Re: Slow and Fast Steps
We may be given K values or will be told which is step is the fast or slow one. Always remember the slow step is the rate-determining step.
- Tue Mar 13, 2018 11:10 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Reversible or irreversible?
- Replies: 2
- Views: 727
Re: Reversible or irreversible?
We know the reaction is isothermal because it takes place in a thermally insulated vessel. At a constant temperature, these reactions are usually reversible
- Tue Mar 13, 2018 11:08 pm
- Forum: General Rate Laws
- Topic: Unique Reaction Rates [ENDORSED]
- Replies: 45
- Views: 166022
Re: Unique Reaction Rates [ENDORSED]
The unique reaction rate depends on the coefficients of the reaction
- Fri Feb 23, 2018 10:58 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Nernst Equation
- Replies: 6
- Views: 954
Re: Nernst Equation
Be sure to remember with nr that the unit "mol" isn't incorporated
- Fri Feb 16, 2018 11:05 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Units of S and H
- Replies: 4
- Views: 866
Re: Units of S and H
Hi Megan!
Although sometimes understanding the units can be quite difficult, in class, Dr. Lavelle mentioned either unit would be correct.
Just be sure to make the units for your Gibbs Free Energy of formation to be in "per mole".
Good luck!
Although sometimes understanding the units can be quite difficult, in class, Dr. Lavelle mentioned either unit would be correct.
Just be sure to make the units for your Gibbs Free Energy of formation to be in "per mole".
Good luck!
- Mon Feb 12, 2018 4:39 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy and Spontaneity
- Replies: 2
- Views: 508
Re: Gibbs Free Energy and Spontaneity
Yes with a positive deltaG, the reaction is not spontaneous in the forward direction but will be spontaneous if reversed.
With a negative deltaG, the reaction IS spontaneous in the forward direction but not so if reversed.
With a negative deltaG, the reaction IS spontaneous in the forward direction but not so if reversed.
- Mon Feb 12, 2018 4:36 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Calculations on Internal Energy
- Replies: 4
- Views: 706
Re: Calculations on Internal Energy
Calculations about internal energy and work were omitted from the first test because Dr. Lavelle felt we had not covered it as well as we needed to at the time.
He expects us to be able to do calculations for both internal energy and work on the midterm!
He expects us to be able to do calculations for both internal energy and work on the midterm!
- Mon Feb 12, 2018 4:33 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Useful Summary of Thermodynamic Definitions
- Replies: 55
- Views: 18750
Re: Useful Summary of Thermodynamic Definitions
To clarify, intensive properties are ratios. For example, density would be an intensive property because it is mass/volume. Where mass and volume are both extensive properties.