For Q=K, the reaction is at equilibrium
For Q>K, the forward reaction is favored (towards the products)
For Q<K, the reverse reaction is favored (towards the reactants)
Search found 49 matches
- Wed Mar 18, 2020 1:20 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Qc vs Kc
- Replies: 15
- Views: 5451
- Wed Mar 18, 2020 1:17 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Approximating X
- Replies: 13
- Views: 856
Re: Approximating X
You can approximate the x value provided K<10^-4 (or smaller), and as already stated, you can cross check using the 5% ionization rule.
- Wed Mar 18, 2020 1:09 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Solving for the equilibrium constant
- Replies: 3
- Views: 405
Re: Solving for the equilibrium constant
^ Your work seems to be right.
- Wed Mar 18, 2020 1:04 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: k
- Replies: 4
- Views: 415
Re: k
Temperature affects the forward and reverse reaction rates, which subsequently affects the rate constant (for K=k/k’ and k = rate constant). So when temperature changes, the rate constant, (and K) also changes.
- Wed Mar 18, 2020 1:01 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reaction Direction
- Replies: 19
- Views: 1040
Re: Reaction Direction
You can determine them using Q and K, for Q>K, the reaction favors reactants and moves left, for Q<K, it favors products and proceeds to the right.
- Wed Mar 18, 2020 12:19 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kw and other constants
- Replies: 9
- Views: 732
Re: Kw and other constants
Kw is the equilibrium constant for water, and the w subsequently refers to water.
- Wed Mar 18, 2020 12:12 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: What to do if R>P for two equations
- Replies: 4
- Views: 478
Re: What to do if R>P for two equations
Find both the K and Q values, and see which one is larger. For Q>K, the reactants are favored and the reaction will shift to the left, for Q<K, products are favored, and the reaction will proceed to the right.
- Wed Mar 18, 2020 12:10 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ignoring solids & liquids for K
- Replies: 7
- Views: 547
Re: ignoring solids & liquids for K
Since the Ca(OH)2 gets dissolved in water, it is an aqueous solution, which makes it included within the equilibrium constant calculation.
- Tue Mar 17, 2020 11:55 pm
- Forum: Ideal Gases
- Topic: Kc
- Replies: 7
- Views: 626
Re: Kc
Provided they are in a gaseous or aqueous state, but not if they are liquids or solids.
- Tue Mar 17, 2020 11:53 pm
- Forum: Ideal Gases
- Topic: ideal gases
- Replies: 14
- Views: 990
Re: ideal gases
Ideal gases do not take up space/volume, and don't have any interaction (no intermolecular forces of attraction). They have to satisfy/follow the (ideal) gas laws essentially.
- Tue Mar 17, 2020 11:50 pm
- Forum: Ideal Gases
- Topic: R Constant
- Replies: 26
- Views: 1225
Re: R Constant
It will normally depend on the units given for the other quantities being used in the problem, and the variations of R and its value/units will usually be given on the formula sheet, so it is easier to assess the units on a case by case basis and see which one is the best fit.
- Tue Mar 17, 2020 11:48 pm
- Forum: Ideal Gases
- Topic: T variable in pv=nrt [ENDORSED]
- Replies: 38
- Views: 1744
Re: T variable in pv=nrt [ENDORSED]
I would keep it in Kelvin at all times, just to be safe.
- Tue Mar 17, 2020 11:36 pm
- Forum: Ideal Gases
- Topic: Partial Pressure
- Replies: 13
- Views: 756
Re: Partial Pressure
If you decrease the volume of a system, the same number of particles (or moles of a substance) will suddenly have more opportunities to collide (the frequency of their collisions will increase), which will increase the pressure of the system. The system will want to nullify this change and return to...
- Tue Mar 17, 2020 11:30 pm
- Forum: Ideal Gases
- Topic: When to use equation
- Replies: 9
- Views: 768
Re: When to use equation
Assuming you are talking about the ideal gas law, in which case yes, you can use the equation to find a value like moles when given temperature, pressure, and volume. In regards to the second part of your question, I don't think you would be able to use the given equation to find initial and final c...
- Sat Mar 07, 2020 12:24 am
- Forum: Balancing Redox Reactions
- Topic: Half rxns
- Replies: 27
- Views: 1489
Re: Half rxns
In both cases, you are balancing O and H, when balancing acidic reactions, add H+ protons (to balance H) and H2O (to balance O), and for basic reactions, add OH- ions and H2O.
- Sat Mar 07, 2020 12:20 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Kelvin or Celsius?
- Replies: 86
- Views: 5872
Re: Kelvin or Celsius?
The temperature should be in kelvin.
- Sat Mar 07, 2020 12:19 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Change in Internal Energy
- Replies: 3
- Views: 385
Re: Change in Internal Energy
At constant pressure, the value of q will equal H, and The equation U=H-PVdv should be used.
- Sat Mar 07, 2020 12:15 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5.61
- Replies: 3
- Views: 417
Re: 5.61
Water (and solids) are not included in the calculation of an equilibrium constant, and adding water should not shift the reaction in either direction since it is omitted from the equilibrium concentration and reaction direction calculations to begin with.
- Sat Mar 07, 2020 12:15 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5.61
- Replies: 3
- Views: 417
Re: 5.61
Water (and solids) are not included in the calculation of an equilibrium constant, and adding water should not shift the reaction in either direction since it is omitted from the equilibrium concentration and reaction direction calculations to begin with.
- Sat Mar 07, 2020 12:11 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reasonable values for K
- Replies: 7
- Views: 563
Re: Reasonable values for K
I think it should be 10^-3<k<10^3 where k values less than 10^-3 are considered small, and k values bigger than 10^3 are considered large.
- Fri Feb 28, 2020 4:02 pm
- Forum: Biological Examples (*DNA Structural Transitions, etc.)
- Topic: Examples Expected to Know
- Replies: 15
- Views: 1869
Re: Examples Expected to Know
I don't think there is a specific list you have to memorize, but knowing/understanding the examples Dr. Lavelle mentions in class should be useful.
- Fri Feb 28, 2020 3:59 pm
- Forum: Calculating Work of Expansion
- Topic: Irreversible and Reversible Expanision
- Replies: 9
- Views: 696
Re: Irreversible and Reversible Expanision
Generally the problem should specify which one it is. If not, for a reversible expansion, Psystem = external pressure, which will decrease as the expansion takes place. For an irreversible expansion, the external pressure will be constant.
- Fri Feb 28, 2020 3:20 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding Inert Gas
- Replies: 20
- Views: 1135
Re: Adding Inert Gas
Adding an inert gas will change the pressure of the system (increase it), but will not affect the K and Q values (does not change the equilibrium concentration), and will not have an effect on the overall reaction.
- Fri Feb 28, 2020 3:12 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Additional resources: Thermodynamics
- Replies: 5
- Views: 497
Re: Additional resources: Thermodynamics
Sapling learning and the textbook questions have both been really helpful! Khanacademy has also been useful for understanding certain concepts.
- Fri Feb 28, 2020 2:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5.55
- Replies: 3
- Views: 304
Re: 5.55
You would need to use an ICE table for part b, to find the eventual equilibrium concentrations of the substances involved.
- Fri Feb 21, 2020 12:49 am
- Forum: Ideal Gases
- Topic: ideal gas
- Replies: 5
- Views: 369
Re: ideal gas
They are (hypothetical) gases that do not have many interactions and take up very little space (and follow the gas laws perfectly). They are considered hypothetical since they do not occur naturally (very often).
- Fri Feb 21, 2020 12:44 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ph
- Replies: 8
- Views: 374
Re: Ph
The pH will always be calculated at equilibrium, subsequently the H+ value will also be at equilibrium.
- Fri Feb 21, 2020 12:37 am
- Forum: Ideal Gases
- Topic: pv=nrt
- Replies: 19
- Views: 1211
Re: pv=nrt
Yes, you can use this equation at STP.
- Fri Feb 21, 2020 12:32 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sign of delta G
- Replies: 9
- Views: 608
Re: Sign of delta G
Yes I think thats possible, provided you have been given enough information.
- Fri Feb 21, 2020 12:24 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: gas constant for gibbs free energy
- Replies: 5
- Views: 431
Re: gas constant for gibbs free energy
Yes, since that R-value is in J/Kmol (or kJ/Kmol), which can be cancelled out to give you an appropriate value (in units) for G (J/mol).
- Sat Feb 15, 2020 3:59 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Joules or KJ?
- Replies: 14
- Views: 2807
Re: Joules or KJ?
I don't think it matters provided your units stay consistent throughout the entire problem. If J/kJ are necessary the problem will probably specify which unit it wants/if it wants you to convert between units.
- Sat Feb 15, 2020 3:56 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Enthalpy
- Replies: 26
- Views: 1232
Re: Enthalpy
The value of state functions are independent of pathways taken to reach their initial/final values. Since pathway becomes inconsequential, the quantity is only dependent on initial and final values.
- Fri Feb 14, 2020 10:09 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Meaning of q=-w
- Replies: 14
- Views: 2367
Re: Meaning of q=-w
q=-w when the internal energy of a system is 0, (normally q=U-w). This happens when an isothermal reversible expansion is taking place since work is being done by the system (and heat is leaving the system).
- Thu Feb 13, 2020 1:40 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: adiabatic
- Replies: 19
- Views: 1076
Re: adiabatic
An adiabatic process has no heat transfer (q=0)
- Thu Feb 13, 2020 1:27 am
- Forum: Calculating Work of Expansion
- Topic: Positive or negative work
- Replies: 15
- Views: 2178
Re: Positive or negative work
It depends but generally it would be positive when work is being done on the system and negative when the system is performing work on the surroundings
- Wed Feb 05, 2020 8:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium concentration vs equilibrium molar conc.
- Replies: 3
- Views: 237
Re: Equilibrium concentration vs equilibrium molar conc.
There is no difference, they are the same thing.
- Wed Feb 05, 2020 8:14 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: state functions
- Replies: 10
- Views: 380
Re: state functions
State functions deal with the initial and final values of a system, but are not interested in the path taken by systems to reach those values.
- Wed Feb 05, 2020 8:09 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Cp and Cv
- Replies: 10
- Views: 483
Re: Cp and Cv
I don't think we will need to memorize them, most values we need should be given to us on the formula sheet.
- Wed Feb 05, 2020 8:04 pm
- Forum: Calculating Work of Expansion
- Topic: units
- Replies: 9
- Views: 244
Re: units
w represents work and is expressed in joules.
- Wed Feb 05, 2020 7:59 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: closed vs isolated
- Replies: 14
- Views: 478
Re: closed vs isolated
A closed system can exchange energy with its surroundings, an isolated system cannot exchange energy or matter with its surroundings.
- Thu Jan 30, 2020 12:32 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: memorize
- Replies: 6
- Views: 270
Re: memorize
I think they would most likely be given on the formula sheet, I would memorize the value for water just in case.
- Thu Jan 30, 2020 12:29 am
- Forum: Phase Changes & Related Calculations
- Topic: 4B.1
- Replies: 6
- Views: 242
Re: 4B.1
It would be positive since work is being performed on the system.
- Wed Jan 29, 2020 1:02 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Units
- Replies: 5
- Views: 208
Re: Units
I would just stay consistent with whatever units the problem gives you.
- Wed Jan 29, 2020 1:01 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Bomb calorimeter
- Replies: 2
- Views: 110
Bomb calorimeter
Can someone explain why its called a bomb calorimeter again?
- Fri Jan 24, 2020 12:11 am
- Forum: Ideal Gases
- Topic: PV=nRT
- Replies: 13
- Views: 703
Re: PV=nRT
It can be used to convert between partial pressure and concentration, since n/v (mol/L) is equal to concentration, for pv=nRT, n/v=P/RT.
- Fri Jan 24, 2020 12:00 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature
- Replies: 6
- Views: 223
Re: Temperature
Increasing temperature decreases k for an exothermic reaction (which releases energy), and increasing temperature increases k for an endothermic reaction (which requires energy).
- Thu Jan 23, 2020 8:02 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Calculating K
- Replies: 15
- Views: 774
Re: Calculating K
You cannot calculate K for an unbalanced equation, but unless you know the reaction is at equilibrium, you would be calculating Q for a balanced reaction as well. For both the Q and K cases, your reaction still needs to be balanced.
- Thu Jan 23, 2020 7:57 pm
- Forum: Ideal Gases
- Topic: Kc vs Kp
- Replies: 109
- Views: 5038
Re: Kc vs Kp
Kc is used when you're dealing with molar concentrations, or when all the substances in your reaction are aqueous. Kp is used for partial pressures, or when the substances in your reaction are all gases.
- Thu Jan 23, 2020 7:53 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Property
- Replies: 6
- Views: 390
Re: State Property
State properties are values that are dependent on a final condition rather than the path taken to reach that condition. So their value would be the same no matter what method you use to get to your final value (similar to the mountain climbing analogy used in class, where the route taken doesn't mat...