## Search found 53 matches

Sat Mar 14, 2020 12:43 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: reaction mechanisms
Replies: 2
Views: 22

### Re: reaction mechanisms

In class Lavelle explained in the sense of throwing people throwing a ball trying to aim to hit the other ball. The probability of hitting eachother's ball is much more likely if you have two people, while with three people throwing three balls the likelihood of them all colliding with each other at...
Sat Mar 14, 2020 12:40 pm
Forum: General Rate Laws
Topic: Study Resources for Kinetics
Replies: 1
Views: 31

### Re: Study Resources for Kinetics

Khan academy has a whole section on kinetics with lots of good videos and resources!
Sun Mar 08, 2020 9:31 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: molecularity
Replies: 5
Views: 30

### Re: molecularity

Yes I believe so
Sun Mar 08, 2020 9:29 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A
Replies: 8
Views: 53

### Re: A

A represents the reactant molar concentration. If its [a]0 then it's the initial concentration.
Sun Mar 08, 2020 9:17 pm
Forum: General Science Questions
Topic: Slope
Replies: 4
Views: 101

### Re: Slope

One thing to get the slope is just to plot the concentration values and examine the straight line to see what the value of the slope is, as you would in a normal graphing class. This can also be done by using the integrated rate laws and using y=mx+b to derive m and see if its negative/positive.
Sun Mar 08, 2020 7:37 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Types of Batteries
Replies: 3
Views: 60

### Re: Types of Batteries

Like what was said above I think non rechargeable batteries have reactions that are one way (irreversible) while rechargeable batteries contain reversible reactions. The difference in products is that usually for stuff that needs a lot of power you would use rechargeable batteries and for stuff that...
Sun Mar 08, 2020 7:14 pm
Forum: Zero Order Reactions
Topic: examples of zero order reactions?
Replies: 6
Views: 52

### Re: examples of zero order reactions?

One example is:

2N2O⟶2N2(g)+O2(g)

And the rate will just = k, you won't multiply by any of the products or reactants.
Mon Mar 02, 2020 9:29 pm
Forum: Balancing Redox Reactions
Topic: Balancing redox (from worksheet 6-8 workshop)
Replies: 2
Views: 51

### Re: Balancing redox (from worksheet 6-8 workshop)

Was there an answer given I can check my work with?
Mon Mar 02, 2020 8:28 pm
Forum: Balancing Redox Reactions
Topic: Balancing redox (from worksheet 6-8 workshop)
Replies: 2
Views: 51

### Balancing redox (from worksheet 6-8 workshop)

Would someone be able to explain to me how they found the half reaction for Cr and then how they balanced the full redox rxn. Thank you so much!

H+(aq) + (Cr2O7)-2(aq) + C2H5OH(aq) ---> (Cr)3+(aq) + C2H4O(aq) + H2O(l)
Sun Mar 01, 2020 9:10 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: kinetically stable?
Replies: 10
Views: 126

### Re: kinetically stable?

This just means the reaction energy barrier is very high and but deltaG is negative
Sun Mar 01, 2020 8:51 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: reaction supported through kinetics
Replies: 2
Views: 55

### Re: reaction supported through kinetics

He meant that this reaction was more dependent on kinetics because diamond is kinetically stable with respect to graphite but unstable with respect to thermodynamics. It will take longer for the reaction to happen because of the high activation energy barrier that has to be overcome.
Sun Mar 01, 2020 8:43 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Oxidation Numbers
Replies: 5
Views: 33

### Re: Oxidation Numbers

The n is how many electrons are gained or released in a reaction so with some it will just be the coefficient of e when you split it up into half reactions. Here is a good website for simple rules about oxidation numbers. Hope that helps. https://www.thoughtco.com/rules-for-assigning-oxidation-numbe...
Sun Mar 01, 2020 8:28 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Spontaneity
Replies: 4
Views: 69

### Re: Spontaneity

This is due to kinetic stability. For diamond to become graphite, there is a large activation energy barrier that needs a lot of energy to overcome and ultimately prevents the conversion to graphite in a forward direction
Sun Mar 01, 2020 8:23 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrochemical Series
Replies: 5
Views: 44

### Re: Electrochemical Series

an electrochemical series is just the order of redox reactions by their standard cell potentials
I don't remember exactly learning it in class either but we have used the concept of cell potentials?
Sun Mar 01, 2020 8:21 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation
Replies: 3
Views: 32

### Re: Nernst Equation

Also once you set the two equations equal to each other and E is on one side you can substitute the delta Go/-nF for Eo)
Sun Mar 01, 2020 8:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: test 2 topics
Replies: 11
Views: 83

### Re: test 2 topics

The second half of outline4 and then outline 5.
Sun Mar 01, 2020 8:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 6
Views: 41

### Re: Cell Diagrams

The only order that matters is anode on the left and cathode on the right, and having aqueous next to salt bridge.
Sun Feb 23, 2020 9:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.1
Replies: 4
Views: 58

### Re: 6M.1

The textbook just does it using the positive reduction value for the anode instead of the one we went over in class. The two equations are ultimately the same, but it just gets confusing with the signs.
E= -E(anode) + E(cathode)
E= E(cathode) - (E(anode))
Sun Feb 23, 2020 9:14 pm
Forum: Balancing Redox Reactions
Topic: Alkaline
Replies: 3
Views: 39

### Re: Alkaline

The process doesn't differ much.
This video is helpful for balancing!
Sun Feb 23, 2020 9:10 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Calculating pH using Nernst Equation
Replies: 2
Views: 35

### Re: Calculating pH using Nernst Equation

This is the equation at standard temperature
Ecell=E∘cell− ((0.0592 V)/n) (log Q)
Sun Feb 23, 2020 8:58 pm
Forum: Balancing Redox Reactions
Topic: Gas Rxns
Replies: 2
Views: 55

### Re: Gas Rxns

Yes redox reactions can happen in any phase including gas, and you can balance them with water. Example: Cr2O2−7(aq)+HNO2(aq) → Cr3+(aq)+NO3−(aq) You put the rxn into half rxns and balance them HNO2(aq)→NO3−(aq) Cr2O2−7(aq)→2Cr3+(aq) Then balance both the rxns with H20 Cr2O2−7(aq)→2Cr3+(aq)+7H2O(l) ...
Sun Feb 23, 2020 8:44 pm
Forum: Ideal Gases
Topic: Conjugate acid and bases
Replies: 7
Views: 167

### Re: Conjugate acid and bases

A conjugate acid has one one more + charge and H atom than the matching base while conjugate base contains one more - charge and one less H atom than the matching acid.
Sun Feb 23, 2020 8:40 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Spontaneity
Replies: 8
Views: 81

### Re: Spontaneity

Yes your delta G will be negative based on the equation ΔG∘=−nFEcell
Tue Feb 11, 2020 1:55 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: State of matter affect entropy
Replies: 3
Views: 37

### State of matter affect entropy

How does the standard entropy of a reaction depend on the state of a molecule(like whether it's a liquid or gas)? This question was asked much earlier but not really a concise answer was given. Thanks!
Sun Feb 09, 2020 9:43 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: deltaU=deltaH= negative
Replies: 2
Views: 28

### Re: deltaU=deltaH= negative

Negative H means an exothermic reaction which means a net release of heat from reactants to products. This will cause the reactants to have less heat and therefore will be favored.
Sun Feb 09, 2020 9:39 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity of Ideal Gases
Replies: 1
Views: 28

### Re: Heat Capacity of Ideal Gases

I think they come from a formula in the first law of thermodynamics saying that the internal energy = 3/2nRT, which in turn comes from the kinetic energy equation. From there I unfortunately don't know how to further derive.
Sun Feb 09, 2020 9:33 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Writing balanced equation for formation reactions
Replies: 4
Views: 28

### Re: Writing balanced equation for formation reactions

It might be because they are asking for the formation of 1 mol of a specific product or reactant so you would use fractions to keep that product's coefficient 1. I know in discussion last week that's what the TA did to balance an equation for calculating work.
Sun Feb 09, 2020 9:29 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: X is to small
Replies: 8
Views: 144

### Re: X is to small

I believe they should always give you K but I'm not completely sure. Also in the review session today, the K was smaller than 10^-3 but we still couldn't discard the x so I'm slightly confused.
Sun Feb 09, 2020 9:18 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs LS7A
Replies: 2
Views: 20

### Re: Gibbs LS7A

For your second question: Changing the concentrations of products and reactants would change Q which is apart of the second equation
Sun Feb 09, 2020 9:15 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: constant p
Replies: 4
Views: 43

### Re: constant p

Enthalpy (which equals H) is amount of heat released divided by what is absorbed(at constant pressure)
Sun Feb 09, 2020 12:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc when stoichiometric constants are changed
Replies: 1
Views: 33

### Kc when stoichiometric constants are changed

In the question from review guide it ask what the Kc will be when the constants are halved. I think the new Kc will just be square root(Kc). Is this true, and if so is it still true if the temperature isn't at 400 K? Thanks!
(Refer to pizza rolls question 1d)
Sun Feb 02, 2020 10:03 pm
Forum: Calculating Work of Expansion
Topic: Enthalpy
Replies: 5
Views: 29

### Re: Enthalpy

It means that it will keep constant independent of the state of the system. So if it is liquid or solid it will stay the same enthalpy.
Sun Feb 02, 2020 10:00 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Steam burns
Replies: 8
Views: 71

### Re: Steam burns

It is because of latent heat of vaporization, so steam has a lot more heat energy, so much it makes more severe burns than boiling water does.
Sun Feb 02, 2020 9:56 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: Degeneracy
Replies: 4
Views: 31

### Re: Degeneracy

Degeneracy means if it corresponds with two or more states of a quantum system that are measurable
Sun Feb 02, 2020 9:05 pm
Forum: Calculating Work of Expansion
Topic: Internal energy
Replies: 5
Views: 38

### Re: Internal energy

Internal energy is the total energy of a closed system
Sun Feb 02, 2020 9:03 pm
Forum: Calculating Work of Expansion
Topic: systems at equilibrium
Replies: 1
Views: 14

### Re: systems at equilibrium

It’s important so all the forces can balance so you can calculate all the energy from work. This is because you have to multiply the force by the distance to get work
Sat Feb 01, 2020 3:49 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Energy of Systems
Replies: 4
Views: 38

### Re: Energy of Systems

The first way is to add or remove the amount of substance in a system. This can only be used for an open system. The second way is to heat or cool the system, which can be used for a closed system. The third way is do either do work on the system or let the system do the work on the surroundings. Th...
Sun Jan 26, 2020 3:13 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: exo thermic
Replies: 11
Views: 155

### Re: exo thermic

In addition, icreasing the temperature will shift the reaction equilibrium to the left.
Sun Jan 26, 2020 3:10 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: endothermic
Replies: 8
Views: 48

### Re: endothermic

When the temperature is increased in an endothermic reaction, the equilibrium constant increases.
Sun Jan 26, 2020 3:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4D.3
Replies: 1
Views: 49

### Re: 4D.3

After you've found your balanced equation, you have to find internal energy. This can be represented as U = q+w. Because it says bomb calorimeter you know that volume is constant so w=0. Then you have to calculate how much heat was released when the carbon monoxide was burned to find q. The equation...
Sun Jan 26, 2020 2:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Textbook question 4C.3
Replies: 2
Views: 69

### Re: Textbook question 4C.3

The answers should be that at constant pressure your temperature = 343 and at constant volume your temperature = 373
Sun Jan 26, 2020 2:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: adding enthalpy of phase changes
Replies: 2
Views: 22

### Re: adding enthalpy of phase changes

I think he means that you have to add it to the final delta h of the reaction. In the example he wrote below he said for Br2 --> 2Br the deltaH= deltaH of vaporization + deltaH of the bonds. Hope that helps
Sun Jan 26, 2020 2:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method Two
Replies: 2
Views: 26

### Re: Method Two

Method 2 uses bond enthalpies to calculate the change in H of the reaction. The left side of the enthalpy equation represents the bonds broken(reactants) and therefore show the energy required, a positive value. The right side will be your the bonds formed(the products) and therefore show the energy...
Sun Jan 19, 2020 9:19 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: H20 in the ICE table
Replies: 26
Views: 231

### Re: H20 in the ICE table

Yes, you will only use the other three compounds in an ICE table.
Sun Jan 19, 2020 9:18 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5% rule
Replies: 4
Views: 48

### Re: 5% rule

To calculate it you just do (equilibrium concentration/initial concentration) * 100. It is valid if it's less than 5%.
If you get around 5% professor Lavelle said it might be due to approximation during calculations so you should try to do them again.
Sun Jan 19, 2020 9:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: composite chemical equations
Replies: 2
Views: 31

### Re: composite chemical equations

There is also a helpful explanation of how composite k multiplication is done in section 5H.2 Composite Equations, pg. 411.
Sun Jan 19, 2020 9:02 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 7
Views: 55

### Re: Le Chatelier's Principle

It is applicable to an reaction where one or more physical parameters changes (including temperature, concentration, and pressure). It tells us what happens but not why it happens.
Sun Jan 19, 2020 8:46 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Relationship between pressure and volume
Replies: 10
Views: 86

### Re: Relationship between pressure and volume

You can look at PV=NRT to know the answer to this. If you keep temperature and moles constant and double pressure, then the volume has to halve. It gets trickier if you change more than one variable.
Sun Jan 12, 2020 6:58 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction Quotient Units
Replies: 10
Views: 60

### Re: Reaction Quotient Units

Usually we will assume the units for concentrations will be in mol/L if not stated, and the ratio of that cancels out the units. Therefore the reactant quotient is unitless.
Sun Jan 12, 2020 6:53 pm
Forum: Ideal Gases
Topic: partial pressures
Replies: 7
Views: 69

### Re: partial pressures

Just to add on to the previous reply, the only reason k will change will be because of a change in temperature.
Sun Jan 12, 2020 6:37 pm
Forum: Ideal Gases
Topic: Ideal Gas Law
Replies: 3
Views: 43

### Re: Ideal Gas Law

The ideal gas law deviates because of two things usually. Primarily, intermolecular forces are always present and although very small/negligible in high heat, are increasingly important in lower temperatures. In addition, the fact that even as pressure continues to increase, the gas volume will neve...
Sun Jan 12, 2020 6:30 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5I.13 part c
Replies: 2
Views: 35

### Re: 5I.13 part c

From previously in the question you foudn that chlorine favors its reactants more than fluorine because the K of chlorine is smaller. Since Cl2 is on the reactants side it is more stable there than flourine is in F2
Sun Jan 12, 2020 6:25 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Application of La Chatelier's
Replies: 3
Views: 23

### Re: Application of La Chatelier's

Le Chatelier's principle is used solely to figure out the outcome when you change reaction conditions when it is in equilibrium as said above. The important thing to note is that Le Chatelier's just tells you what happens not why it happens.

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