## Search found 40 matches

Tue Mar 12, 2019 6:10 pm
Forum: Calculating Work of Expansion
Topic: 4.17 7th Edition
Replies: 1
Views: 293

### Re: 4.17 7th Edition

because some of the reactant, including all of the limiting reactant will be used up and converted to products, I believe the overall moles decreases in the problem. I may be completely wrong though, i have the 6th edition and just did a similar problem so i hope its the same one
Tue Mar 12, 2019 6:05 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta H of reaction
Replies: 2
Views: 363

### Re: delta H of reaction

Its all about matching the coefficients of the reactants and how many moles of reactant are reactions say for the reaction 2A>3B and delta h is -20, if there were 4 moles of A reacting then we have to multiply delta h by two so that the coefficient matches the number of moles reacting
Tue Mar 12, 2019 6:02 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: catalyst and equilibrium constant
Replies: 2
Views: 100

### Re: catalyst and equilibrium constant

Its because the catalyst affects each rate constant proportionally, the forward and reverse rate will increase proportionally which will not change the equilibrium constant
Mon Mar 04, 2019 9:31 pm
Forum: First Order Reactions
Topic: order
Replies: 5
Views: 213

### order

how do we calculate or know what the reaction order is and what does the reaction order mean?
Mon Mar 04, 2019 9:06 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Galvanic Cells
Replies: 4
Views: 140

### Re: Galvanic Cells

I believe it is so that the reaction can occur spontaneously, where being reversible allows the cell to have little micro changes that give the cell the energy to do work
Mon Mar 04, 2019 9:03 pm
Forum: General Rate Laws
Topic: 6th edition 15.9
Replies: 4
Views: 204

### 6th edition 15.9

when trying to find the units for the rate constants, why is the units for k mol per liter per second when the units in the table for constants are liter per mol per second?
Tue Feb 26, 2019 10:35 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram and Ecell [ENDORSED]
Replies: 10
Views: 39820

### Re: Cell Diagram and Ecell[ENDORSED]

I believe the solid is always on the outside (or just inside the inert part) so the second form should always be right, and yes everything is reversed when the E is less than zero.
Tue Feb 26, 2019 10:33 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Replies: 2
Views: 107

### Re: Question about cell diagrams

I have been having the same confusion, Im just hoping that for a test, we would be given a simpler version and the half reaction equation that we would need would be apparent
Tue Feb 26, 2019 10:31 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Problem 14.15- Sixth Edition
Replies: 1
Views: 77

### Re: Problem 14.15- Sixth Edition

this is just because OH is not present alone in solution, it need another ion to "attach" to which comes in the form of K+ but it doesn't really affect anything as they are basically dissociate, just makes the problem look a lot more confusing
Tue Feb 26, 2019 10:30 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Order of Cell Diagram
Replies: 1
Views: 93

### Re: Order of Cell Diagram

you always want the part that is the physical cathode or anode to be on the outside, in that case, Cl2 is the part that is being reduced, so ibleieve it would go on the outside, making the bottom version correct
Mon Feb 18, 2019 1:27 pm
Forum: Van't Hoff Equation
Topic: Temperature Dependence of K
Replies: 5
Views: 269

### Re: Temperature Dependence of K

yeah you can also think about it in terms of the Le Chatlier's principle with how heat affects what sides of equations are favored, if one side of the equation is more favored at a different heat, then the there will be greater concentration of molecules on that side and the K value would shift. Hof...
Mon Feb 18, 2019 1:20 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy and Molar Ratios
Replies: 2
Views: 204

### Re: Gibbs Free Energy and Molar Ratios

Usually you will make the product coefficient equal to 1 and adjust the reactants accordingly because the questions are usually asking for the change in gibbs free energy for the creation of one mole of the product. However, it always depends on the information we are being asked for. If the questio...
Mon Feb 18, 2019 1:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Polyprotic Acids
Replies: 5
Views: 216

### Re: Polyprotic Acids

you have to write out each equation separate as though the two reactions are independent, making two different ice tables, however with the second ice table, you have to be sure to add the hydronium or h+ ions that were created in the first reaction so the initial concentration of hydronium in the s...
Mon Feb 18, 2019 1:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: K and Gibbs Free Energy
Replies: 2
Views: 135

### Re: K and Gibbs Free Energy

I believe so because they are directly correlated, and a positive delta G means that the products have a higher G which means they have more energy available to do work and the way reactions do work is through expansion (when that side of the equation has more moles of gas or is favored). I may have...
Tue Feb 12, 2019 10:00 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp vs Cv
Replies: 7
Views: 544

### Cp vs Cv

How do we know when to use Cv or Cp? I know one is constant volume and one is constant volume but for a problem where it looks like both are constant, how can we tell which one to use?
Mon Feb 11, 2019 2:33 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculating deltaH of a reaction at a different temperature
Replies: 2
Views: 166

### Re: Calculating deltaH of a reaction at a different temperature

You would have to be given the different cosntants (bond energies or standard reaction formation enthalpies) associated with that specific temperature difference. I don't think there is a way to calculate the different delta H just using the delta H at one temperature. And i don't think this will be...
Mon Feb 11, 2019 10:54 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Ideal Behavior
Replies: 3
Views: 185

### Re: Ideal Behavior

I believe this just means to assume all gases act as ideal gases, for example in equations where there are 5 moles of gas on the reactants side and 5 moles of gas on the product side, all of these gases should behave in the same way. This allows us to predict the way reactions will shift when change...
Mon Feb 11, 2019 10:51 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Internal Energy and Entropy Relationship
Replies: 1
Views: 106

### Re: Internal Energy and Entropy Relationship

They are not always directly related, for example, if you take the 2 connected spaces example we got in class. If all the gas is trapped in one side of the beaker then suddenly allowed to move to the other side as well, the entropy will increase because there are more possible positions, however the...
Mon Feb 04, 2019 8:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Total bond energy
Replies: 2
Views: 96

### Total bond energy

Does a higher total bond energy imply that the bond is more stable? For example in the 6th edition 8.77, why do the different resonances have different energies and what does that mean for stability?
Mon Feb 04, 2019 12:27 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question 8.3 (Sixth Edition)
Replies: 2
Views: 174

### Re: Question 8.3 (Sixth Edition)

One equation for work is w=-P(change in Volume)(the constant for Lxatm=J) the change in volume can be calculated using the area of the bike pump cylinder times how far it moved.
Mon Feb 04, 2019 12:25 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question 8.1 (Sixth Edition)
Replies: 1
Views: 111

### Re: Question 8.1 (Sixth Edition)

I believe b is a closed system because the actual coolant material cannot leave the system yet energy can and c is an isolated system because no energy or matter is able to leave a bomb calorimeter
Mon Feb 04, 2019 12:22 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 4
Views: 156

### Re: Bond Enthalpies

You only need to know the types of bonds present and how many of them are so if you can look at the name of the molecule and see how it is bonded in your head, you can use that to calculate the bond enthalpies
Thu Jan 31, 2019 6:31 pm
Forum: Calculating Work of Expansion
Topic: Atmospheres to Joules
Replies: 2
Views: 105

### Re: Atmospheres to Joules

I believe youre talking about the Work equation where you have w=PxV where w should be in Joules and pxv gives you atmospheres times liters, in that case you would use 1 L.atm = 101.325 J which is given on our equation sheet.
Mon Jan 28, 2019 8:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State
Replies: 2
Views: 112

### Re: Standard State

It will usually be stated in the problem, otherwise you can look at the units. The standard state of substance is its phase (solid, liquid, gas) at 25.0 °C and one atmosphere pressure
Mon Jan 28, 2019 6:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method 3
Replies: 2
Views: 112

### Re: Method 3

I believe enthalpy refers to the amount fo energy that goes into the bond formation of that compound, the higher the enthalpy, the more energy that goes into the bond. Higher energy bonds also tend to be more reactive and release more energy so i think a higher enthalpy means less stable.
Mon Jan 28, 2019 6:36 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: reversible expansion
Replies: 3
Views: 138

### reversible expansion

In the equation that gives the work for reversible expansion how do we find V1 and V2?
Mon Jan 28, 2019 6:14 pm
Forum: Phase Changes & Related Calculations
Topic: Work
Replies: 5
Views: 251

### Work

How can you tell if the work is positive or negative with respect to a given system?
Mon Jan 21, 2019 1:03 pm
Forum: Calculating the pH of Salt Solutions
Topic: 6th edition 12.69
Replies: 1
Views: 311

### Re: 6th edition 12.69

I asked some of the UAs this same question yesterday and they weren't very sure why either so we shouldn't be expected to know why that happens. If we were asked that type of problem, an equation for the reaction would also be given to us
Mon Jan 21, 2019 12:59 pm
Forum: Bronsted Acids & Bases
Topic: Sig Figs
Replies: 4
Views: 308

### Re: Sig Figs

I also had a different professor so I'm not 100% sure but I have heard you cannot miss more than 2 points per test due to sig figs but they are graded so it is good to know.
Mon Jan 21, 2019 12:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Polyprotic Equations
Replies: 1
Views: 36

### Polyprotic Equations

When making the second ice chart for a polyphonic equation (treating each reaction independently), do we add the hydronium or hydroxide ions created in the first reaction to the initial concentration of hydronium or hydroxide ions in the second chart? or just leave them as zero, assuming the reactio...
Mon Jan 21, 2019 12:48 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in temperature's effect on K
Replies: 4
Views: 174

### Re: Change in temperature's effect on K

I always get confused about this too. Usually, I think of an endothermic reaction that is taking in energy where two atoms or molecules are being joined. These molecules need energy in order to be joined so the more heat you apply, the more products will be made. And then I just think that an exothe...
Mon Jan 14, 2019 9:23 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: change in pressure
Replies: 4
Views: 181

### Re: change in pressure

I find it easier to picture the products as reactants and just flip the equation around so that it reads the opposite way. It is easier for me to see which way the reaction would shift when i do this
Mon Jan 14, 2019 9:21 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Autoprotolysis
Replies: 3
Views: 132

### Re: Autoprotolysis

Autoprotolysis can occur between any two identical molecules as long as they have acidic hydrogen and lone pairs to give off (as per wikipedia)
Mon Jan 14, 2019 6:50 pm
Forum: Ideal Gases
Topic: Homework for week 2 [ENDORSED]
Replies: 10
Views: 2399

### Homework for week 2[ENDORSED]

What problems are we supposed to use for the homework for week two? should it be from the chemical equilibria outline or the acids and basis outline?
Mon Jan 14, 2019 6:48 pm
Forum: Ideal Gases
Topic: Using Kc or Kp
Replies: 13
Views: 438

### Re: Using Kc or Kp

All of these are just units for partial pressures, in order to convert between them, you would just have to look up how each one relates to another for example 760 torr is equal to 1 atm so to go from atm to torr you just multiply by 760.
Thu Jan 10, 2019 6:13 pm
Forum: Administrative Questions and Class Announcements
Topic: Audio-Visual Focus-Topics
Replies: 2
Views: 109

### Audio-Visual Focus-Topics

I was wondering if there was any way to see the correct answers for the pre and post assessments on the audit visual focus topics?
Tue Jan 08, 2019 9:45 pm
Forum: Student Social/Study Group
Topic: New to Lavelle
Replies: 32
Views: 3960

### New to Lavelle

I am new to Lavelle and finding it a bit confusing to navigate through his website and resources (im still not even really sure how to navigate chemistry community because there are so many posts and so many from the past, it seems as there are so many great resources but almost too many. I was wond...
Tue Jan 08, 2019 9:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: hw questions - points
Replies: 9
Views: 334

### Re: hw questions - points

how do you post an original post? all I seem to be able to do is post replies, I used the FAQ but I still can can only find how to reply
Tue Jan 08, 2019 8:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: hw questions - points
Replies: 9
Views: 334

### Re: hw questions - points

Yes, I believe any sort of post on here counts towards your 3 points a week for chemistry community, including questions about homework problems
Mon Jan 07, 2019 11:17 pm
Forum: Ideal Gases
Topic: R in PV=nRT
Replies: 34
Views: 744

### Re: R in PV=nRT

It is the called the gas constant and the SI unit for it is J K^-1 mol^-1