Search found 42 matches
- Fri Mar 16, 2018 12:27 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation energy and temp
- Replies: 3
- Views: 583
Activation energy and temp
Does activation energy change with temperature?
- Mon Mar 12, 2018 8:39 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Adiabatic System
- Replies: 3
- Views: 579
Re: Adiabatic System
also, there is no transfer of matter between the system and the surroundings
- Mon Mar 12, 2018 8:24 pm
- Forum: *Enzyme Kinetics
- Topic: Catalyst
- Replies: 6
- Views: 902
Re: Catalyst
Catalysts are not consumed so in the steps of the reaction, the species that is used as a reactant in one step, and comes out as a product in a future step is the catalyst
- Mon Mar 12, 2018 8:14 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: reaction profile
- Replies: 3
- Views: 440
Re: reaction profile
maybe it could be possible if the potential gibbs free energy of the reactants is equal to the potential gibbs free energy of the products. but it is probably super rare
- Wed Mar 07, 2018 10:57 pm
- Forum: General Rate Laws
- Topic: Timing of rate laws
- Replies: 2
- Views: 339
Re: Timing of rate laws
it at the beginning so we use the initial rate because any rate after could be affected by products going back to reactants
- Wed Mar 07, 2018 10:50 pm
- Forum: Second Order Reactions
- Topic: Second Order
- Replies: 3
- Views: 573
Re: Second Order
false because the rate is dependent on the concentration of the reaction
r=k[A]^2
so if you change [A] then the rate also changes
r=k[A]^2
so if you change [A] then the rate also changes
- Wed Mar 07, 2018 10:47 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Rate Law being affected by product [ENDORSED]
- Replies: 2
- Views: 450
Re: Rate Law being affected by product [ENDORSED]
experimentally we usually only consider the forward reaction. the example in the book with the reaction with ozone and O2, they consider the reverse reaction because in the atmosphere there is no way to isolate the products so the products are able to turn back into reactants and affect the rate law
- Fri Mar 02, 2018 10:44 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: How to tell difference btwn thermo and kinetics [ENDORSED]
- Replies: 7
- Views: 1001
Re: How to tell difference btwn thermo and kinetics [ENDORSED]
all reactions have to overcome a specific activation energy this is what determines the rate of the reaction (kinetics)
whether or not the products are in a higher or lower energy state than the reactants determines if the reaction is favorable (thermodynamics)
whether or not the products are in a higher or lower energy state than the reactants determines if the reaction is favorable (thermodynamics)
- Fri Mar 02, 2018 10:38 pm
- Forum: Second Order Reactions
- Topic: Example?
- Replies: 4
- Views: 581
Re: Example?
another example is the decomposition of nitrogen dioxide
2NO2(g)-->2NO(g)+O2(g)
r= k[NO2]^2
2NO2(g)-->2NO(g)+O2(g)
r= k[NO2]^2
- Fri Mar 02, 2018 10:30 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Number of steps to reach the overall reaction
- Replies: 3
- Views: 559
Re: Number of steps to reach the overall reaction
yes since each step is a reaction and all the steps together form the overall reaction, the number of steps is equal to the number of intermediate reactions
- Tue Feb 20, 2018 7:29 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2
- Replies: 1
- Views: 293
Test 2
Will we be given the table with the reduction half reaction potentials?
- Sat Feb 17, 2018 11:42 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: notation for galvanic cell
- Replies: 2
- Views: 361
Re: notation for galvanic cell
a vertical line represents an interface between phases in contact with each other
while a comma represents two different things not separated by anything
while a comma represents two different things not separated by anything
- Sat Feb 17, 2018 11:39 pm
- Forum: Balancing Redox Reactions
- Topic: Sign of E when anode rxn reverses
- Replies: 2
- Views: 344
Re: Sign of E when anode rxn reverses
if you use the equation Ecell= Ecathode - E anode then you dont have to switch the sign from the table
if you use the equation E cell= Ecathod + E anode then you do have to switch the sign from the table
if you use the equation E cell= Ecathod + E anode then you do have to switch the sign from the table
- Sat Feb 17, 2018 11:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.13 b
- Replies: 1
- Views: 218
Re: 14.13 b
you use an inert conductor as the electrode when dealing with half reactions that have no conducting solids.
because I2(s) is not a conductor, you use platinum as the electrode
because I2(s) is not a conductor, you use platinum as the electrode
- Sun Feb 11, 2018 10:56 pm
- Forum: Van't Hoff Equation
- Topic: Different versions of van't Hoff
- Replies: 2
- Views: 528
Re: Different versions of van't Hoff
The advantage to using Lavelle’s is that you can calculate k at different temperatures if delta h is known
- Sun Feb 11, 2018 9:44 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: 9.47
- Replies: 1
- Views: 329
9.47
why is change in entropy surroundings equal to 0 for irreversible free expansion but not for reversible?
- Sun Feb 11, 2018 9:43 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: change in entropy total
- Replies: 2
- Views: 456
change in entropy total
why is the total change of entropy not always 0?
- Sat Feb 03, 2018 3:44 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Difference between deltaS(tot), deltaS and deltaS(surr)
- Replies: 5
- Views: 1688
Re: Difference between deltaS(tot), deltaS and deltaS(surr)
one relation is that delta s of the system plus delta s of the surroundings is equal to delta s total
- Sat Feb 03, 2018 3:43 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Formula Manipulations
- Replies: 1
- Views: 320
Re: Formula Manipulations
q is equal to deltaU at constant volume becuase delta u = q plus w, so at constant volume there is no expansionary work (w=0)
- Sat Feb 03, 2018 3:39 pm
- Forum: Van't Hoff Equation
- Topic: How to calculate K [ENDORSED]
- Replies: 3
- Views: 867
Re: How to calculate K [ENDORSED]
to isolate k you would do e^lnk
and for the other side of the equation e^....
and for the other side of the equation e^....
- Sun Jan 21, 2018 9:47 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Bomb calorimeter
- Replies: 7
- Views: 783
Bomb calorimeter
Why is a bomb calorimeter an isolated system?
- Sun Jan 21, 2018 6:40 pm
- Forum: Phase Changes & Related Calculations
- Topic: Delta H Fusion / Delta H Vaporization
- Replies: 2
- Views: 2560
Re: Delta H Fusion / Delta H Vaporization
the q = n C deltaT is for molar heat capacity
- Sun Jan 21, 2018 6:29 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calorimetry Questions
- Replies: 2
- Views: 321
Re: Calorimetry Questions
the heat absorbed by the calorimeter is equal to the heat released by the reaction
- Sun Jan 21, 2018 6:21 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heating Curve Calculation Confusion
- Replies: 3
- Views: 346
Re: Heating Curve Calculation Confusion
it depends on the starting temperature of the ice and the final temperature of the water vapor if the starting temp of ice is less than 0 and the final temp of water vapor is over 100 degrees celcius then you would use MCdeltaT three times once to go from <0 to 0, phase change, then to go from 0 to ...
- Fri Jan 12, 2018 2:18 pm
- Forum: Phase Changes & Related Calculations
- Topic: qv vs qp
- Replies: 4
- Views: 2208
qv vs qp
What is the difference between qv and qp?
- Fri Jan 12, 2018 2:15 pm
- Forum: Phase Changes & Related Calculations
- Topic: Standard Reaction Enthalpy
- Replies: 8
- Views: 791
Re: Standard Reaction Enthalpy
One difference is that standard reaction enthalpy is in KJ, while standard enthalpy of formation is in KJ/mol
- Fri Jan 12, 2018 2:13 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heating Curve
- Replies: 6
- Views: 534
Re: Heating Curve
On the heating curve, the sloped lines represent heat capacity
- Wed Nov 29, 2017 6:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.53 sig figs
- Replies: 1
- Views: 312
11.53 sig figs
a reaction mixture that consists of .400 mol H2 and 1.60 mol I2 was introduced into a 3.00 Liter flask and heated. at equilibrium, 60.0% of the hydrogen gas had reacted. what is the equilibrium constant K for the reaction.
why is the answer in 2 sig figs?
why is the answer in 2 sig figs?
- Tue Nov 28, 2017 1:32 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: t-shaped
- Replies: 4
- Views: 581
Re: t-shaped
one bond angle is also slightly less than 120 degrees
- Tue Nov 28, 2017 1:31 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Internuclear Axis
- Replies: 1
- Views: 291
Re: Internuclear Axis
yes it is the area where electrons are being shared. it is just the imaginary straight line that connects the nuclei of atoms bonded to each other in a molecule
- Thu Nov 09, 2017 11:39 am
- Forum: Bond Lengths & Energies
- Topic: dissociatioin energies
- Replies: 3
- Views: 432
Re: dissociatioin energies
oh i think i meant to say NH
so why is dissociation energy of CH higher than that of NH
so why is dissociation energy of CH higher than that of NH
- Thu Nov 09, 2017 1:41 am
- Forum: Bond Lengths & Energies
- Topic: dissociatioin energies
- Replies: 3
- Views: 432
dissociatioin energies
why does CH have a higher dissociation energy than CN
- Wed Nov 01, 2017 11:35 pm
- Forum: Electronegativity
- Topic: oxygen and nitrogen
- Replies: 3
- Views: 1150
oxygen and nitrogen
why is oxygen and nitrogen switched for ionization energy and not for electronegativity if electonegativity is based on ionization energy??
- Wed Nov 01, 2017 11:28 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Wave Function
- Replies: 2
- Views: 357
Re: Wave Function
you would use the wave function to describe an electron with wavelike properties and indeterminacy in momentum and position in an atom. it is also the radial wavefuntion times the angular wave function. this shows how orbitals change with angles and radii
- Wed Nov 01, 2017 11:23 pm
- Forum: Trends in The Periodic Table
- Topic: 2.71
- Replies: 1
- Views: 339
Re: 2.71
oxidation state is referring to the charge. a plus 4 charge is at a higher oxidation state than a plus 3 charge
- Sun Oct 29, 2017 6:09 pm
- Forum: Electronegativity
- Topic: Exceptions [ENDORSED]
- Replies: 2
- Views: 361
Re: Exceptions [ENDORSED]
oxygen and nitrogen are exceptions to the trend for ionization energy, not for electronegativity. we expect oxygen to have higher IE than nitrogen but nitrogen has higher IE. this is because of the p orbital. oxygen has 4 electrons in the p subshell, while nitrogen has 3. because nitrogen has 3 elec...
- Sun Oct 29, 2017 5:57 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge of Carbon in CH3
- Replies: 2
- Views: 16098
Re: Formal Charge of Carbon in CH3
the formal charge of carbon in ch3 is 0.
valence electron=4
lone electrons=1
bonded electrons/2=3
4-(1+3)=0
FC=0
valence electron=4
lone electrons=1
bonded electrons/2=3
4-(1+3)=0
FC=0
- Sun Oct 29, 2017 5:50 pm
- Forum: Ionic & Covalent Bonds
- Topic: Noble Gases
- Replies: 6
- Views: 875
Re: Noble Gases
because noble gases have very high ionization energy and very low electron affinity, they do not form chemical compounds easily. however when they are ionized or under pressure, they are able to make chemical compounds. so, yes they can make chemical compounds even tho they have a full outer shell
- Fri Oct 13, 2017 6:59 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Post Assessment Module 30C
- Replies: 4
- Views: 695
Re: Photoelectric Post Assessment Module 30C
you can use the equation
frequency= (.5 x mass of electron x velocity of electron squared +work function) /plancks constant
i got that from
Energy of photon - work function = kinetic energy of electron
energy of photon = h x frequency
and
KE = .5mv^2
frequency= (.5 x mass of electron x velocity of electron squared +work function) /plancks constant
i got that from
Energy of photon - work function = kinetic energy of electron
energy of photon = h x frequency
and
KE = .5mv^2
- Fri Oct 13, 2017 5:00 pm
- Forum: Photoelectric Effect
- Topic: Post Assessment #28 [ENDORSED]
- Replies: 4
- Views: 616
Re: Post Assessment #28 [ENDORSED]
yes, the energy required to remove an electron is equal to the work function or threshold energy
- Fri Oct 06, 2017 10:22 am
- Forum: Molarity, Solutions, Dilutions
- Topic: G13 [ENDORSED]
- Replies: 2
- Views: 479
Re: G13 [ENDORSED]
to find the concentration after the dilution you use (M initial)(volume initial) = (molarity final)(volume final)
(.2 x 1)/(4) = final molarity
that equals .05M
you use 4 because its final volume in the equation
(.2 x 1)/(4) = final molarity
that equals .05M
you use 4 because its final volume in the equation
- Thu Oct 05, 2017 8:26 pm
- Forum: Balancing Chemical Reactions
- Topic: incomplete combustion
- Replies: 3
- Views: 2780
incomplete combustion
this isn't one of the homework problems, but question H.18 asks what the chemical equation is for the incomplete combustion of heptane gas. i was just wondering how to do it??