Search found 49 matches
- Thu Mar 12, 2020 6:50 pm
- Forum: Ideal Gases
- Topic: Kc vs Kp
- Replies: 109
- Views: 5569
Re: Kc vs Kp
Kp is used with gases and Kc is used when you are dealing with concentrations.
- Thu Mar 12, 2020 6:49 pm
- Forum: Ideal Gases
- Topic: R Constant
- Replies: 26
- Views: 1265
Re: R Constant
It depends on the units given in the problem. All of the R constants mean the same thing; the numbers just change due to unit conversions.
- Thu Mar 12, 2020 6:48 pm
- Forum: Ideal Gases
- Topic: reversing reactions
- Replies: 83
- Views: 6191
Re: reversing reactions
K is inversed so it becomes 1/K.
- Thu Mar 12, 2020 6:47 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Units
- Replies: 8
- Views: 2900
Re: Units
yes. the units for rate is always concentration (M) over time (s)
- Thu Mar 12, 2020 6:46 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: What was your favorite chem topic?
- Replies: 137
- Views: 13378
Re: What was your favorite chem topic?
Chemical Equilibrium!
- Sun Mar 08, 2020 5:05 pm
- Forum: First Order Reactions
- Topic: rate constants
- Replies: 30
- Views: 1563
Re: rate constants
Rate constants are always positive because concentrations cannot be negative.
- Sun Mar 08, 2020 5:04 pm
- Forum: Zero Order Reactions
- Topic: third order
- Replies: 11
- Views: 1232
Re: third order
No, we are not covering third order reactions.
- Sun Mar 08, 2020 5:04 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: units of k
- Replies: 9
- Views: 729
Re: units of k
for zero-order reactions, K has units of M/s
for first-order reactions, K has units of 1/s
for second-order reactions, K has units of 1/M.s
for first-order reactions, K has units of 1/s
for second-order reactions, K has units of 1/M.s
- Sun Mar 08, 2020 5:02 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: units of T
- Replies: 11
- Views: 1103
Re: units of T
It is usually best to use the standard units if nothing is specified.
- Sun Mar 08, 2020 5:01 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: determine n
- Replies: 16
- Views: 1445
Re: determine n
n represents the order of the reactants.
- Sun Mar 08, 2020 5:00 pm
- Forum: General Rate Laws
- Topic: the variable A
- Replies: 4
- Views: 348
Re: the variable A
A is the frequency factor or pre-exponential factor. It includes the number of collisions with the correct orientation.
- Sun Mar 08, 2020 4:59 pm
- Forum: General Rate Laws
- Topic: integrated rate laws
- Replies: 7
- Views: 476
Re: integrated rate laws
The rate law is a differential equation that only considers the initial rate, while the integrated rate laws can be used to discover how quickly a reaction has progressed over a certain amount of time.
- Sun Mar 08, 2020 4:56 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: instantaneous rate
- Replies: 16
- Views: 989
Re: instantaneous rate
The instantaneous rate is more precise because it isn't an average.
- Sun Mar 08, 2020 4:55 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: derivations
- Replies: 9
- Views: 623
Re: derivations
In lecture, Dr. Lavelle went over the derivations for the first, second, and zeroeth order rate laws and their half-life reactions. He did not go over the derivation for the Arrhenius equation though.
- Sun Mar 08, 2020 4:46 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: kinetically stable?
- Replies: 10
- Views: 780
Re: kinetically stable?
It is thermodynamically spontaneous because delta G is negative, but it won't proceed normally because it has such a high activation energy.
- Sun Mar 08, 2020 4:44 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: units
- Replies: 11
- Views: 787
Re: units
It is usually mol per L per unit of time, which is usually in seconds.
- Sun Mar 01, 2020 6:50 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidizing/reducing agent
- Replies: 18
- Views: 1161
Re: Oxidizing/reducing agent
I think of it in terms of opposites, so whatever is being oxidized acts as the reducing agent and whatever is being reduced acts as the oxidizing agent.
- Sun Mar 01, 2020 5:07 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Metal dissolution
- Replies: 10
- Views: 1050
Re: Metal dissolution
The metal that becomes an ion is the one that dissolves in the solution. Also, most reactions would identify it as dissolved by using (aq).
- Sun Mar 01, 2020 5:05 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Activation Energy
- Replies: 16
- Views: 1523
Re: Activation Energy
Activation energy is the minimum amount of energy required to begin the reaction. In an energy diagram, it is the highest peak on the energy graph.
- Sun Mar 01, 2020 5:03 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: intermediate
- Replies: 26
- Views: 2109
Re: intermediate
An intermediate is formed and used up during the reaction, so it will not be included in the rate law because it isn't part of the overall reaction.
- Sun Mar 01, 2020 5:02 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: how can you tell
- Replies: 11
- Views: 806
Re: how can you tell
Reactions with short reaction times are usually controlled by kinetics, while reactions with longer reaction times are usually controlled by thermodynamics.
- Sun Mar 01, 2020 4:59 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Units for delta G
- Replies: 31
- Views: 2109
Re: Units for delta G
The unit would be kJ.
- Sun Mar 01, 2020 4:59 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Where to find Ecell values
- Replies: 15
- Views: 916
Re: Where to find Ecell values
It can be found in Appendix 2B at the back of the book!
- Sun Mar 01, 2020 4:58 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: delta G = -nFE
- Replies: 6
- Views: 600
Re: delta G = -nFE
The negative is to make sure that when E is positive, delta G will be negative, meaning that the reaction would be spontaneous.
- Sun Mar 01, 2020 4:56 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: finding n
- Replies: 6
- Views: 457
Re: finding n
Adriana_4F wrote:What happens if the number of electrons transferred is different? Do you have to balance the equation to make it the same?
Yes, you would have to balance the half-reactions so that the number of electrons transferred is the same.
- Sun Mar 01, 2020 4:55 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Flipping the sign
- Replies: 10
- Views: 675
Re: Flipping the sign
E is usually given for reduction reactions. When you need to find E for an oxidation reaction, you flip the sign for the equivalent reduction half-reaction.
- Sun Mar 01, 2020 4:54 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: cell diagram order
- Replies: 3
- Views: 246
Re: cell diagram order
The order of the cell diagram depends on state, not the order of the reaction, so it should be s|g|aq||aq|g|s.
- Sun Mar 01, 2020 4:53 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cells
- Replies: 6
- Views: 448
Re: Galvanic Cells
Galvanic cells are spontaneous, so E has to be positive.
- Sun Mar 01, 2020 4:51 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: C(gr) state
- Replies: 4
- Views: 295
Re: C(gr) state
C(gr) refers to carbon in the form of graphite.
- Sun Mar 01, 2020 4:50 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 10
- Views: 527
Re: Salt Bridge
The purpose of the salt bridge is to maintain electrical neutrality between the cathode and anode to keep the cell from reaching equilibrium too quickly.
- Sun Mar 01, 2020 4:50 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: salt bridge
- Replies: 11
- Views: 705
Re: salt bridge
The purpose of the salt bridge is to maintain electrical neutrality between the cathode and anode to keep the cell from reaching equilibrium too quickly.
- Sun Mar 01, 2020 4:48 pm
- Forum: Balancing Redox Reactions
- Topic: Reducing/Oxidizing Agents
- Replies: 13
- Views: 647
Re: Reducing/Oxidizing Agents
I think of it in terms of opposites, so whatever is being oxidized acts as the reducing agent and whatever is being reduced acts as the oxidizing agent.
- Sun Mar 01, 2020 4:47 pm
- Forum: Balancing Redox Reactions
- Topic: When to add H+ or H20
- Replies: 19
- Views: 2533
Re: When to add H+ or H20
In an acidic solution, you can use both H+ and H2O to balance the equation. In an acidic solution, You can add H2O to balance the oxygen first, and then H+ to balance the hydrogens. In a basic solution, you can add OH- to balance the oxygens and then add H2O to balance the hydrogens.
- Sun Mar 01, 2020 4:44 pm
- Forum: Balancing Redox Reactions
- Topic: H+ or H2O
- Replies: 9
- Views: 665
Re: H+ or H2O
You can use both H+ and H2O to balance redox reactions when they occur in acidic solutions.
- Sun Mar 01, 2020 4:43 pm
- Forum: Balancing Redox Reactions
- Topic: Cell Diagrams
- Replies: 14
- Views: 1006
Re: Cell Diagrams
In a cell diagram, the anode would be on the left and the cathode would be on the right, separated by || (the salt bridge).
- Sun Mar 01, 2020 4:42 pm
- Forum: Balancing Redox Reactions
- Topic: Acidic and Basic solutions
- Replies: 11
- Views: 762
Re: Acidic and Basic solutions
In an acidic solution, you can balance it using H2O and H+, while in a basic solution, you can balance it using H2O and OH-.
- Thu Feb 20, 2020 5:46 pm
- Forum: Balancing Redox Reactions
- Topic: oxidizing and reducing agents
- Replies: 3
- Views: 259
oxidizing and reducing agents
For this reaction, would Cl2 be both the oxidizing and reducing agent?
Reaction of chlorine in water:
Cl 2 (g) --> HClO(aq) + Cl-
Reaction of chlorine in water:
Cl 2 (g) --> HClO(aq) + Cl-
- Thu Feb 20, 2020 4:44 pm
- Forum: Balancing Redox Reactions
- Topic: Homework problem 6K.1
- Replies: 5
- Views: 375
Re: Homework problem 6K.1
Start by identifying the oxidized and reduced species. The oxidation number for Cr changes from +6 to +3, indicating reduction (gain of 3 electrons). The oxidation number for C changes from -2 to -1, indicating oxidation (loss of 1 electron). You now have the skeleton for your half-reactions: (Cr2O...
- Thu Feb 20, 2020 4:42 pm
- Forum: Balancing Redox Reactions
- Topic: Test 2 [ENDORSED]
- Replies: 12
- Views: 748
Re: Test 2 [ENDORSED]
Test 2 has been postponed to week 9 starting on Tuesday during discussion sections.
- Thu Feb 20, 2020 12:29 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation numbers
- Replies: 5
- Views: 339
oxidation numbers
Do you have to figure out the oxidation numbers of all of the parts of the reaction in order to figure out which parts are oxidized and which are reduced?
- Thu Feb 20, 2020 12:28 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation numbers
- Replies: 3
- Views: 255
oxidation numbers
In an equation, if the oxidation number of one of the elements decreases, is that a way to see if it is reduced? Same question for if the oxidation number increases, would it be oxidized?
- Thu Feb 20, 2020 12:27 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation numbers
- Replies: 8
- Views: 593
oxidation numbers
Is the oxidation number just the charge? If not, how do you find the oxidation number?
- Thu Feb 20, 2020 12:13 pm
- Forum: Balancing Redox Reactions
- Topic: Homework problem 6K.1
- Replies: 5
- Views: 375
Homework problem 6K.1
The following reaction is used in the acidic solution in the Breathalyzer test to determine the level of alcohol in the blood: H+(aq) + (Cr2O7)-2(aq) + C2H5OH(aq) ---> (Cr)3+(aq) + C2H4O(aq) + H2O(l) I need help figuring out how to get a balanced redox equation by writing the balanced oxidation and ...
- Mon Feb 10, 2020 11:39 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: delta U = q + w
- Replies: 6
- Views: 419
delta U = q + w
In this equation: delta U = q + w, how would you know whether or not work would be positive or negative?
- Mon Feb 10, 2020 11:38 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: delta U = q + w
- Replies: 3
- Views: 196
delta U = q + w
In this equation: delta U = q + w, how would you know whether or not q would be positive or negative?
- Thu Jan 23, 2020 12:33 pm
- Forum: Ideal Gases
- Topic: solids and K
- Replies: 8
- Views: 375
solids and K
I am confused about why we don't include the solids when calculating K because they are included within the reaction.
- Thu Jan 23, 2020 12:31 pm
- Forum: Ideal Gases
- Topic: ICE table approximation
- Replies: 10
- Views: 419
ICE table approximation
How do you know whether you can use the approximation shortcut rather than the quadratic equation for problems involving ICE tables?
- Thu Jan 09, 2020 12:19 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K vs. Q
- Replies: 10
- Views: 555
Re: K vs. Q
K is the equilibrium constant, while Q is the reaction quotient and can, therefore, be used at any time during the reaction. This means that Q can be calculated even when the reaction is not at equilibrium, leading to K and Q possibly being different numbers. by comparing the different values of K a...
- Thu Jan 09, 2020 12:06 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5G.1C
- Replies: 3
- Views: 157
5G.1C
c) If one starts with a higher pressure of reactant, the equilibrium constant will be larger.
I don't really understand why this is false, because I thought that pressure affects the equilibrium constant for gases. Can someone please explain why this is false?
I don't really understand why this is false, because I thought that pressure affects the equilibrium constant for gases. Can someone please explain why this is false?