## Search found 34 matches

Wed Mar 14, 2018 11:48 am
Forum: Second Order Reactions
Topic: Test 3 #8
Replies: 2
Views: 325

### Re: Test 3 #8

use the half life to solve for k and then use the integrated rate law.
Wed Mar 14, 2018 11:47 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Calculating Gibbs Free Energy
Replies: 4
Views: 377

### Re: Calculating Gibbs Free Energy

Usually i look at what information is given and then am able to determine which equation works.
Wed Mar 14, 2018 11:44 am
Forum: General Rate Laws
Topic: Test #3 Q3
Replies: 3
Views: 623

### Re: Test #3 Q3

The key is you need to remember to balance the equation. Then you can use the integrated rate law to solve for time.
Tue Mar 06, 2018 10:11 pm
Forum: General Rate Laws
Topic: 15.17
Replies: 4
Views: 309

### Re: 15.17

As the others said, C is zero order because looking at experiments 1 and 4, even though the concentration of C changes, the initial rate remains the same. This means C has no impact and therefore its exponent is 0.
Tue Mar 06, 2018 10:08 pm
Forum: General Rate Laws
Topic: Units for Time
Replies: 2
Views: 142

### Re: Units for Time

For when the units aren't given, the SI unit of time is seconds.
Tue Mar 06, 2018 10:06 pm
Forum: General Rate Laws
Topic: 15.5
Replies: 3
Views: 251

### Re: 15.5

Im pretty sure the unique rate refers to only 1 mole of reactant in the reaction. Since there are three moles of oxygen we multiple the unique rate by 3.
Tue Mar 06, 2018 9:59 pm
Forum: General Rate Laws
Topic: Proper units
Replies: 7
Views: 454

### Re: Proper units

It shouldn't really matter but sometimes like in problem 15.3 you need the answer to be in moles so you can run further calculations with your answer.[/quote]
Tue Mar 06, 2018 9:59 pm
Forum: General Rate Laws
Topic: Proper units
Replies: 7
Views: 454

### Re: Proper units

i shouldn't really matter but sometimes like in problem 15.3 you need the answer to be in moles so you can run further calculations with your answer.
Tue Mar 06, 2018 9:58 pm
Forum: General Rate Laws
Topic: 15.3
Replies: 3
Views: 235

### Re: 15.3

As someone already said, the units are already Moles of N02 L^-1S^-1 so you don't need to divide by moles of N02
Tue Mar 06, 2018 9:53 pm
Forum: General Rate Laws
Topic: Writing rate laws
Replies: 4
Views: 261

### Re: Writing rate laws

When the reactant is first order, you do not need to include the exponent, when the reactant is 0 order, you do not need to write the reactant at all.
Thu Mar 01, 2018 8:34 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Dissolving metal in a solution
Replies: 3
Views: 235

### Re: Dissolving metal in a solution

Figure out if the E nott value is positive
Thu Mar 01, 2018 8:33 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: standard conditions [ENDORSED]
Replies: 4
Views: 281

### Re: standard conditions[ENDORSED]

As others have said, standard conditions refers to the temp and pressure etc, that are accepted so that accepted values for E nott and many other values from tables are valid.
Thu Mar 01, 2018 8:30 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell potential
Replies: 5
Views: 289

### Re: Cell potential

Yeah i think when they are both negative you gotta just choose the one that is less negative for the cathode
Thu Feb 22, 2018 9:41 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Concentration Cells
Replies: 2
Views: 162

### Re: Concentration Cells

I believe the difference in concentration creates a potential difference because on one end reduction occurs, and on the other oxidation is occurring which allows for the travel of electrons and in turn allows for current to flow.
Thu Feb 22, 2018 9:35 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E rxn vs E standard at equilibrium [ENDORSED]
Replies: 2
Views: 289

### Re: E rxn vs E standard at equilibrium[ENDORSED]

I don't think Erxn is zero at equilibrium. Erxn=Estandard at equilibrium. It only equals 0 for hydrogen
Thu Feb 22, 2018 9:34 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: K and Q at equilibrium
Replies: 5
Views: 377

### Re: K and Q at equilibrium

Erxn is Estandard at equilibrium. Q=1 at equilibrium. This checks out mathematically using the equation Estandard=Erxn+rt/nf lnq. if q=1, then lnq=0 and Erxn=Estandard
Wed Feb 14, 2018 10:38 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: State Properties
Replies: 5
Views: 487

### Re: State Properties

heat capacity is q=c(delta t)
specific heat capacity is q=mc(delta t)
basically specific heat capacity is specific to your sample because it incorporates mass.
Wed Feb 14, 2018 10:36 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ∆U for isothermal reversible
Replies: 3
Views: 264

### Re: ∆U for isothermal reversible

I think the question will specify if the gas is ideal. If it doesn't specify whether the gas is ideal or not, it will give explicit condition of the gas.
Wed Feb 14, 2018 10:35 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Work
Replies: 5
Views: 361

### Re: Work

That is correct because the work done is a vacuum is 0 because there is no pressure or opposing force.
Tue Feb 06, 2018 5:18 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.13
Replies: 1
Views: 131

### Re: 9.13

im not positive but maybe because it says to assume ideal gas behavior? could just be a poorly written question as well.
Tue Feb 06, 2018 5:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.99 Concept
Replies: 1
Views: 146

### Re: 8.99 Concept

i think they are using the q=mc(dt) equation to solve for dt. this works because we are given the m, the c, and the q leaving the dt. I think your way probably works too, but is a lot more work.
Tue Feb 06, 2018 5:10 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Standard Gibbs Free Energy of Formation (Units)
Replies: 2
Views: 232

### Re: Standard Gibbs Free Energy of Formation (Units)

As Suchita said, it depends on how the question is worded, and how you complete the calculations, however kj/mole should be good.
Wed Jan 31, 2018 8:43 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: sign of entropy
Replies: 11
Views: 674

### Re: sign of entropy

Direction of heat flow determines the sign as well as whether or not the reaction is spontaneous.
Wed Jan 31, 2018 8:40 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 9.33 (a)
Replies: 3
Views: 463

### Re: 9.33 (a)

As jannie had said, gasses do have more entropy and therefore the reactants in this case have more entropy than the products because there are more moles of gas on the reactants side.
Wed Jan 31, 2018 8:36 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: heat capacities
Replies: 5
Views: 384

### Re: heat capacities

As the others said you would set the ice side equal to the water side and use the respective heat capacities in each side.
Wed Jan 24, 2018 12:23 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Energy of systems
Replies: 4
Views: 276

### Re: Energy of systems

Delta u= q+w
where u is energy and q is heat and w is work. Thus the ways to change energy is by adding or subtracting heat or work.
Wed Jan 24, 2018 12:21 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Released
Replies: 3
Views: 141

### Re: Heat Released

Yeah like nicole said, it depends on how you word the answer. If you add the word released then your number is positive, but if you are referring to the change in energy for the reaction then it should be negative
Wed Jan 24, 2018 12:18 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Exothermic
Replies: 7
Views: 367

### Re: Exothermic

As others have said, the reaction releases energy causing the surrounding area absorb the energy and feel warmer .
Fri Jan 19, 2018 8:32 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar heat capacity
Replies: 3
Views: 188

### Re: Molar heat capacity

Not sure if this is right or not but the way I was thinking about it was the lower he pressure, the easier it is to add heat and therefore the lower the heat capacity... similarly the greater the volume, the more energy it can absorb and therefore the specific heat capacity is lower... again I’m not...
Fri Jan 19, 2018 8:25 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U？
Replies: 7
Views: 2171

### Re: Delta U？

I believe the delta symbol always means change in the given variable which in this case is U(final)-U(initial)=(delta) U. U is the energy of the system.
Fri Jan 19, 2018 8:23 am
Forum: Calculating Work of Expansion
Topic: Work
Replies: 2
Views: 167

### Re: Work

I’m pretty sure if the piston allows the volume to increase then pressure will remain constant.
Sat Jan 13, 2018 8:57 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 13
Views: 829

### Re: Phase Changes

Exothermic phase changes are ones that release heat such as a gas turning into a liquid or solid, or a liquid turning into a solid. As the temperature lowers, energy is released and the phase changes.
Sat Jan 13, 2018 12:49 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8042
Views: 1412374

### Re: Post All Chemistry Jokes Here

If you aren't apart of the solution, you're apart of the precipitate
Wed Jan 10, 2018 11:38 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Paths and Changes of State
Replies: 3
Views: 326

### Re: Paths and Changes of State

I don’t think we need to know what you drew however we need to know how to draw and interpret a phase change graph plotting energy and heat and you definetley should be able to determine whether this change is endothermic or exothermic.