Search found 50 matches

by Bella Townsend
Tue Mar 17, 2020 10:19 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Kelvin or Celsius?
Replies: 47
Views: 960

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.
by Bella Townsend
Tue Mar 17, 2020 10:17 pm
Forum: *Enzyme Kinetics
Topic: catalyst
Replies: 5
Views: 609

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.
by Bella Townsend
Tue Mar 17, 2020 10:14 pm
Forum: First Order Reactions
Topic: molecularity
Replies: 3
Views: 131

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.
by Bella Townsend
Tue Mar 17, 2020 10:03 pm
Forum: *Enzyme Kinetics
Topic: K and Catalyst
Replies: 3
Views: 71

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.
by Bella Townsend
Tue Mar 17, 2020 10:01 pm
Forum: General Rate Laws
Topic: rate in an uncontrolled solution
Replies: 2
Views: 139

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.
by Bella Townsend
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: 71

Re: 6M 2

In the overall reaction the electrons in the cathode and anode half reactions cancel out.
by Bella Townsend
Tue Mar 17, 2020 9:55 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Profile
Replies: 2
Views: 74

Re: Reaction Profile

The problem does not depend on the size of the intermediate, just the other reactants
by Bella Townsend
Tue Mar 17, 2020 9:53 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: comparison
Replies: 3
Views: 114

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.
by Bella Townsend
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: 2
Views: 57

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.
by Bella Townsend
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: 78

Re: concentration

the concentration affects the cell potential, and subsequently affects the reaction overall.
by Bella Townsend
Tue Mar 17, 2020 9:40 pm
Forum: General Rate Laws
Topic: 7C.7
Replies: 2
Views: 60

Re: 7C.7

The second part is not counted. The rate of reaction is determined by the slow reaction.
by Bella Townsend
Tue Mar 17, 2020 9:37 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics
Replies: 2
Views: 126

Re: Kinetics

In general short reactions favor kinetic control, while long reactions favor thermodynamic control.
by Bella Townsend
Tue Mar 17, 2020 9:36 pm
Forum: Zero Order Reactions
Topic: Rate
Replies: 1
Views: 112

Rate

Why does increasing the concentration of the reactants not speed up the rate of the reaction for a zero order reaction?
by Bella Townsend
Tue Mar 17, 2020 9:33 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: catalyst vs intermediate
Replies: 3
Views: 45

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.
by Bella Townsend
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: 2
Views: 295

Concentration Cells

Do concentration cells ever have a positive Ecell? Can a cell be both galvanic and a concentration cell?
by Bella Townsend
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: 115

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.
by Bella Townsend
Tue Mar 17, 2020 9:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Work+Gibbs Free Energy
Replies: 3
Views: 89

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
by Bella Townsend
Tue Mar 17, 2020 9:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Ecell Potential
Replies: 2
Views: 71

Re: Ecell Potential

Changes in temperature, concentration, and pressure affect ecell potential.
by Bella Townsend
Thu Mar 05, 2020 7:32 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: catalyst
Replies: 4
Views: 57

Re: catalyst

I have this question as well.
by Bella Townsend
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: 70

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...
by Bella Townsend
Fri Feb 21, 2020 9:42 pm
Forum: Calculating Work of Expansion
Topic: when work is 0
Replies: 5
Views: 120

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.
by Bella Townsend
Fri Feb 21, 2020 9:39 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: E values
Replies: 2
Views: 46

Re: E values

In the very back of the book in appendix 2, right after standard enthalpies and entropies
by Bella Townsend
Fri Feb 21, 2020 9:31 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Pure Elements
Replies: 2
Views: 48

Pure Elements

Why do pure elements generally have a oxidation number of zero?
by Bella Townsend
Fri Feb 21, 2020 9:27 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: dG vs dG knot
Replies: 2
Views: 38

dG vs dG knot

What is the relationship between deltaG and deltaG knot?
by Bella Townsend
Fri Feb 21, 2020 9:25 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Equation
Replies: 1
Views: 33

Equation

What is the original equation that lnK2/lnK1=-dH/R * (1/T2-1/T1) is derived from?
by Bella Townsend
Mon Feb 10, 2020 5:45 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Review Session #3b
Replies: 2
Views: 36

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...
by Bella Townsend
Mon Feb 10, 2020 2:44 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4C.3
Replies: 7
Views: 104

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...
by Bella Townsend
Mon Feb 10, 2020 2:30 pm
Forum: Administrative Questions and Class Announcements
Topic: HW 6
Replies: 3
Views: 49

HW 6

What sections do we do for homework this week?
by Bella Townsend
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: 39

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...
by Bella Townsend
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: 58

Re: Delta in enthalpy and not entropy

you can calculate the change in both enthalpy and entropy. Both enthalpy and entropy are state functions
by Bella Townsend
Fri Feb 07, 2020 4:21 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW 4.15
Replies: 2
Views: 56

Re: HW 4.15

you would use the equation deltaS=nRln(Tfinal-Tinitial)
by Bella Townsend
Fri Feb 07, 2020 4:19 pm
Forum: Phase Changes & Related Calculations
Topic: Negative Work
Replies: 18
Views: 301

Re: Negative Work

a rule of thumb is:
Expansion is work done by the system
Compression is work done on the system
by Bella Townsend
Fri Feb 07, 2020 4:16 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: gibbs free energy of formation
Replies: 3
Views: 43

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.
by Bella Townsend
Fri Jan 31, 2020 9:34 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4B.13
Replies: 2
Views: 49

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
by Bella Townsend
Fri Jan 31, 2020 9:11 pm
Forum: Calculating Work of Expansion
Topic: Difference between irreversible/reversible reaction?
Replies: 2
Views: 39

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...
by Bella Townsend
Fri Jan 31, 2020 9:04 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4A.5
Replies: 1
Views: 34

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...
by Bella Townsend
Fri Jan 31, 2020 8:54 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 17
Views: 141

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...
by Bella Townsend
Fri Jan 31, 2020 8:44 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4A.13
Replies: 4
Views: 39

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.
by Bella Townsend
Fri Jan 31, 2020 8:40 pm
Forum: Phase Changes & Related Calculations
Topic: DELTA H Vs Q
Replies: 7
Views: 62

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
by Bella Townsend
Fri Jan 24, 2020 8:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q and K
Replies: 4
Views: 55

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
by Bella Townsend
Fri Jan 24, 2020 8:32 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy
Replies: 2
Views: 27

Re: Enthalpy

it is exactly the same, we are just apply it to phase changes now
by Bella Townsend
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: 56

Re: State Properties and q vs H

there are multiple ways to calculate enthalpy, but only one way to calculate heat
by Bella Townsend
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: 105

Re: k<10^-3

the scale is relative. the smaller the K value the stronger the acid.
by Bella Townsend
Fri Jan 24, 2020 8:17 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: state functions and properties
Replies: 11
Views: 2427

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
by Bella Townsend
Fri Jan 24, 2020 8:05 pm
Forum: Phase Changes & Related Calculations
Topic: Delta G vs. Delta H
Replies: 3
Views: 38

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.
by Bella Townsend
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: 34

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...
by Bella Townsend
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: 55

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.
by Bella Townsend
Fri Jan 17, 2020 1:38 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Temperature Change
Replies: 9
Views: 181

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.
by Bella Townsend
Fri Jan 17, 2020 1:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Value of Kw
Replies: 6
Views: 51

Re: Value of Kw

Kw= Ka x Kb
Ka and Kb have to be a conjugate acid and base pair
by Bella Townsend
Fri Jan 17, 2020 1:29 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Partial Pressure
Replies: 19
Views: 131

Re: Partial Pressure

I'm confused on the meaning on Kc and the difference between Kc and K with other subscripts.

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