Search found 50 matches
- Tue Mar 17, 2020 10:19 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Kelvin or Celsius?
- Replies: 86
- Views: 1434
Re: Kelvin or Celsius?
Typically, you only ever use celsius is there is a change in temperature (delta T) because then the units don't matter. The difference will be the same.
- Tue Mar 17, 2020 10:17 pm
- Forum: *Enzyme Kinetics
- Topic: catalyst
- Replies: 9
- Views: 739
Re: catalyst
One of the key features of an enzyme which is used as a catalyst is that it is not used up in the reaction. Therefore, it is not in the overall reaction.
- Tue Mar 17, 2020 10:14 pm
- Forum: First Order Reactions
- Topic: molecularity
- Replies: 3
- Views: 186
Re: molecularity
The order of the reaction depends on the pressures or concentrations of the reactants, while molecularity is the amount of different molecules in the reactants.
- Tue Mar 17, 2020 10:03 pm
- Forum: *Enzyme Kinetics
- Topic: K and Catalyst
- Replies: 3
- Views: 104
Re: K and Catalyst
When add all the steps/reaction mechanisms the catalysts and intermediates cancel out, which means they do not affect the K of the reaction.
- Tue Mar 17, 2020 10:01 pm
- Forum: General Rate Laws
- Topic: rate in an uncontrolled solution
- Replies: 2
- Views: 199
Re: rate in an uncontrolled solution
You could probably recreate a similar solution with controlled reactants to compare to the pond or other uncontrolled solution.
- Tue Mar 17, 2020 9:56 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6M 2
- Replies: 2
- Views: 110
Re: 6M 2
In the overall reaction the electrons in the cathode and anode half reactions cancel out.
- Tue Mar 17, 2020 9:55 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Reaction Profile
- Replies: 2
- Views: 99
Re: Reaction Profile
The problem does not depend on the size of the intermediate, just the other reactants
- Tue Mar 17, 2020 9:53 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: comparison
- Replies: 3
- Views: 170
Re: comparison
through kinetic control the reaction depends on the amount of reactions, but through thermodynamic control the reaction also depends on the concentration of the products.
- Tue Mar 17, 2020 9:47 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: pH meter
- Replies: 11
- Views: 119
Re: pH meter
A pH meter measures the acidity of a solution. This can be helpful in an electrical cell (galvanic or concentration) to determine potential, because potential is based on the flow of electrons is related to the concentration of H+ ions as we have seen in redox reactions.
- Tue Mar 17, 2020 9:42 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: concentration
- Replies: 3
- Views: 138
Re: concentration
the concentration affects the cell potential, and subsequently affects the reaction overall.
- Tue Mar 17, 2020 9:40 pm
- Forum: General Rate Laws
- Topic: 7C.7
- Replies: 2
- Views: 101
Re: 7C.7
The second part is not counted. The rate of reaction is determined by the slow reaction.
- Tue Mar 17, 2020 9:37 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Kinetics
- Replies: 9
- Views: 209
Re: Kinetics
In general short reactions favor kinetic control, while long reactions favor thermodynamic control.
- Tue Mar 17, 2020 9:36 pm
- Forum: Zero Order Reactions
- Topic: Rate
- Replies: 1
- Views: 166
Rate
Why does increasing the concentration of the reactants not speed up the rate of the reaction for a zero order reaction?
- Tue Mar 17, 2020 9:33 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: catalyst vs intermediate
- Replies: 3
- Views: 83
Re: catalyst vs intermediate
In the mechanism steps of a reaction, a catalyst shows up first as a product, but an intermediate shows up first as a reactant.
- Tue Mar 17, 2020 9:29 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration Cells
- Replies: 4
- Views: 402
Concentration Cells
Do concentration cells ever have a positive Ecell? Can a cell be both galvanic and a concentration cell?
- Tue Mar 17, 2020 9:27 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: What to do if R>P for two equations
- Replies: 4
- Views: 165
Re: What to do if R>P for two equations
You can tell by see which one has least gas molecules on right. This makes the reaction more favorable toward the reactants.
- Tue Mar 17, 2020 9:24 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Work+Gibbs Free Energy
- Replies: 3
- Views: 139
Re: Work+Gibbs Free Energy
The Gibbs free energy of a reversible reaction is equal to the max work that can be done at const. temperature and pressure
- Tue Mar 17, 2020 9:18 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Ecell Potential
- Replies: 3
- Views: 110
Re: Ecell Potential
Changes in temperature, concentration, and pressure affect ecell potential.
- Thu Mar 05, 2020 7:32 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: catalyst
- Replies: 4
- Views: 104
Re: catalyst
I have this question as well.
- Thu Mar 05, 2020 7:28 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6.61
- Replies: 2
- Views: 101
6.61
In a neuron, the concentration of K+ ions inside the cell is about 20-30 times as great as the outside. What potential difference between the inside and outside of the cell would you expect to measure if the difference is only due to the imbalance of potassium ions? The solution manual says that sin...
- Fri Feb 21, 2020 9:42 pm
- Forum: Calculating Work of Expansion
- Topic: when work is 0
- Replies: 5
- Views: 176
Re: when work is 0
In a reversible reaction there is more work done than in a irreversible reaction. In a reversible reaction the change in temperature is zero, aka an isothermal reaction.
- Fri Feb 21, 2020 9:39 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: E values
- Replies: 2
- Views: 73
Re: E values
In the very back of the book in appendix 2, right after standard enthalpies and entropies
- Fri Feb 21, 2020 9:31 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Pure Elements
- Replies: 2
- Views: 78
Pure Elements
Why do pure elements generally have a oxidation number of zero?
- Fri Feb 21, 2020 9:27 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: dG vs dG knot
- Replies: 2
- Views: 58
dG vs dG knot
What is the relationship between deltaG and deltaG knot?
- Fri Feb 21, 2020 9:25 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Equation
- Replies: 1
- Views: 54
Equation
What is the original equation that lnK2/lnK1=-dH/R * (1/T2-1/T1) is derived from?
- Mon Feb 10, 2020 5:45 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Review Session #3b
- Replies: 2
- Views: 41
Review Session #3b
3B) Dr. Lavelle picks up the ice cream that he has just heated up (-2.8 oC) and accidentally drops it on the ground and can’t eat it. Tears streaming down his face, he watches as half of it melts away when he realizes that from the moment he dropped the ice cream until now, it has received exactly 2...
- Mon Feb 10, 2020 2:44 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: 4C.3
- Replies: 7
- Views: 117
Re: 4C.3
Some equations you need to know for this equation is when you are calculating the Cpm for a molecule of one type of atom like an ideal gas you use q=n*5/2R*deltaT when you are calculating the Cvm for a molecule of one type of atom like an ideal gas you use q=n*3/2R*deltaT The rest is given to you 76...
- Mon Feb 10, 2020 2:30 pm
- Forum: Administrative Questions and Class Announcements
- Topic: HW 6
- Replies: 3
- Views: 55
HW 6
What sections do we do for homework this week?
- Fri Feb 07, 2020 5:29 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Calculating entropy using positive or negative delta H
- Replies: 2
- Views: 48
Re: Calculating entropy using positive or negative delta H
When enthalpy is positive and delta H is greater than zero, this means that a system absorbed heat, this is a non spontaneous reaction, and the system is doing work on the surroundings when work is negative. When enthalpy is negative and delta H is less than zero, this means that a system released h...
- Fri Feb 07, 2020 4:25 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Delta in enthalpy and not entropy
- Replies: 6
- Views: 75
Re: Delta in enthalpy and not entropy
you can calculate the change in both enthalpy and entropy. Both enthalpy and entropy are state functions
- Fri Feb 07, 2020 4:21 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: HW 4.15
- Replies: 2
- Views: 64
Re: HW 4.15
you would use the equation deltaS=nRln(Tfinal-Tinitial)
- Fri Feb 07, 2020 4:19 pm
- Forum: Phase Changes & Related Calculations
- Topic: Negative Work
- Replies: 18
- Views: 411
Re: Negative Work
a rule of thumb is:
Expansion is work done by the system
Compression is work done on the system
Expansion is work done by the system
Compression is work done on the system
- Fri Feb 07, 2020 4:16 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: gibbs free energy of formation
- Replies: 3
- Views: 47
Re: gibbs free energy of formation
Gibbs free energy with a negative value, is a spontaneous reaction that produces more stable reactants compared to that of a non spontaneous reaction.
At a substances lowest energy state is its most stable configuration.
At a substances lowest energy state is its most stable configuration.
- Fri Jan 31, 2020 9:34 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 4B.13
- Replies: 2
- Views: 56
Re: 4B.13
w=-nRTln(v2/v1) is the right equation but first you have to use the equation PV=nRT to find the number of moles
n=PV/RT
1.79 x4.29/0.08206 x 305 x ln 6.59/4.29
=-326J
n=PV/RT
1.79 x4.29/0.08206 x 305 x ln 6.59/4.29
=-326J
- Fri Jan 31, 2020 9:11 pm
- Forum: Calculating Work of Expansion
- Topic: Difference between irreversible/reversible reaction?
- Replies: 2
- Views: 41
Re: Difference between irreversible/reversible reaction?
irreversible reaction occur at thermodynamic equilibrium, while reversible reactions do not maintain thermodynamic equilibrium. irreversible reaction are where the products formed do not combine to give the reactants I looked up a reaction online that is an example potassium chlorate decomposes on h...
- Fri Jan 31, 2020 9:04 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: 4A.5
- Replies: 1
- Views: 37
Re: 4A.5
For a, the equation for irreversible expansion is w=-PdeltaV w=-(1atm)(1.2L) w=-122J for b, w=-nRTln(v2/v1) w=-(0.2mol)(8.314)(298.15K)(ln2.40L/1.2L) w=-344J Reversible expansion does more work than irreversible expansion, because when a system does reversible expansion it has to go outside of the t...
- Fri Jan 31, 2020 8:54 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes
- Replies: 17
- Views: 187
Re: Phase Changes
If you look at a heating curve, the slanted lines represent the temperature increasing, and the flat lines represent the phase change where there is no change in temperature. For example, on the first straight line, the leftmost point represents solid water at 0 degrees celsius, and on the most righ...
- Fri Jan 31, 2020 8:44 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 4A.13
- Replies: 4
- Views: 50
Re: 4A.13
Due to the law of conservation of energy, the q of the system is equal to the -q of the surroundings. So when you use a bomb calorimeter, you combust the substance inside. Therefore, the q of the substance is equal to the -q of the bomb calorimeter.
- Fri Jan 31, 2020 8:40 pm
- Forum: Phase Changes & Related Calculations
- Topic: DELTA H Vs Q
- Replies: 7
- Views: 95
Re: DELTA H Vs Q
Delta H is Kilojoules per mole because it is the amount of heat that is required for a particular substance to form, vaporize, sublimate etc.
Q is KJ to measure heat transferred between two systems
Q is KJ to measure heat transferred between two systems
- Fri Jan 24, 2020 8:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q and K
- Replies: 4
- Views: 65
Re: Q and K
K is the constant of a certain reaction when it is in equilibrium
Q is the quotient of products and reactants at any stage of a reaction
Q=K the reaction is at equilibrium
Q>K the reaction favors the reactants
Q<K the reaction favors the products
Q is the quotient of products and reactants at any stage of a reaction
Q=K the reaction is at equilibrium
Q>K the reaction favors the reactants
Q<K the reaction favors the products
- Fri Jan 24, 2020 8:32 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy
- Replies: 2
- Views: 44
Re: Enthalpy
it is exactly the same, we are just apply it to phase changes now
- Fri Jan 24, 2020 8:29 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: State Properties and q vs H
- Replies: 2
- Views: 60
Re: State Properties and q vs H
there are multiple ways to calculate enthalpy, but only one way to calculate heat
- Fri Jan 24, 2020 8:23 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: k<10^-3
- Replies: 9
- Views: 114
Re: k<10^-3
the scale is relative. the smaller the K value the stronger the acid.
- Fri Jan 24, 2020 8:17 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: state functions and properties
- Replies: 11
- Views: 3036
Re: state functions and properties
there are multiple ways to get to the right conclusion with a state function. Multiple variables contribute to the calculation of a state function.
in a path function, how you get the answer matters. There is only one way to calculate a path function
in a path function, how you get the answer matters. There is only one way to calculate a path function
- Fri Jan 24, 2020 8:05 pm
- Forum: Phase Changes & Related Calculations
- Topic: Delta G vs. Delta H
- Replies: 3
- Views: 42
Re: Delta G vs. Delta H
Endergonic and endothermic have the same meaning, endergonic refers to gibs free energy and endothermic refers to the enthalpy.
- Fri Jan 17, 2020 1:46 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Homework question 5J.5
- Replies: 3
- Views: 38
Re: Homework question 5J.5
for the reaction 2HD(g)+H2(g)⇌D2(g), H2 is an inert gas and it does not affect the reaction. Typically noble gases in reactions are inert gases. the reaction Cl2(g)⇌2Cl(g) goes from 1 mole Cl in the reactants, and 2 moles Cl in the products. Le chatelier's principles says that the reaction goes to t...
- Fri Jan 17, 2020 1:41 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert Gas
- Replies: 7
- Views: 102
Re: Inert Gas
Inert gases do not react, and therefore do not affect the partial pressures of the other products and reactants.
Inert gases do not affect the volume and pressure of the reaction.
Inert gases do not affect the volume and pressure of the reaction.
- Fri Jan 17, 2020 1:38 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Temperature Change
- Replies: 9
- Views: 233
Re: Temperature Change
Adding heat is like adding another reactant and when you increase the number of reactants the reaction shifts to the right.
Releasing heat is adding to the products side of the reactions, when you increase the products, the reaction shifts to the left.
Releasing heat is adding to the products side of the reactions, when you increase the products, the reaction shifts to the left.
- Fri Jan 17, 2020 1:31 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Value of Kw
- Replies: 6
- Views: 54
Re: Value of Kw
Kw= Ka x Kb
Ka and Kb have to be a conjugate acid and base pair
Ka and Kb have to be a conjugate acid and base pair
- Fri Jan 17, 2020 1:29 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Partial Pressure
- Replies: 19
- Views: 150
Re: Partial Pressure
I'm confused on the meaning on Kc and the difference between Kc and K with other subscripts.