Search found 56 matches
- Mon Mar 11, 2019 4:05 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Large Ea
- Replies: 2
- Views: 269
Large Ea
Is there ever an activation energy that is so large that the reaction can't proceed? What causes this/can this occur suddenly because of something in the reaction?
- Mon Mar 11, 2019 4:03 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Factors
- Replies: 3
- Views: 1185
Factors
What factors alter how large or small the activation energy of a reaction is?
- Mon Mar 04, 2019 4:40 pm
- Forum: General Rate Laws
- Topic: Rate Law Formula
- Replies: 2
- Views: 335
Rate Law Formula
Do these general rate laws work for every order of reaction? Are there any exceptions?
- Mon Mar 04, 2019 4:37 pm
- Forum: General Rate Laws
- Topic: K
- Replies: 3
- Views: 441
K
What factors of a reaction affect its K value?
- Mon Mar 04, 2019 4:35 pm
- Forum: Zero Order Reactions
- Topic: Different Orders
- Replies: 5
- Views: 590
Different Orders
Do we only have to know how to do 0-2nd order reaction calculations? And are the calculations similar or are they derived differently?
- Mon Feb 25, 2019 4:07 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Standard Cell Potential [ENDORSED]
- Replies: 1
- Views: 242
Standard Cell Potential [ENDORSED]
Are there any special rules or types of chemicals that aren't included when calculating the standard cell potential?
- Mon Feb 25, 2019 4:04 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Max Potential [ENDORSED]
- Replies: 1
- Views: 281
Max Potential [ENDORSED]
Why is max potential when very little current flows instead of when max current flows through the cell?
- Mon Feb 25, 2019 4:03 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cells [ENDORSED]
- Replies: 1
- Views: 245
Galvanic Cells [ENDORSED]
Is there ever a galvanic cell reaction that creates electrical energy without making a physical difference on the anode/cathode?
- Tue Feb 19, 2019 8:07 pm
- Forum: Van't Hoff Equation
- Topic: Non-consistant enthalpy
- Replies: 3
- Views: 419
Non-consistant enthalpy
What do you do if delta H isn't consistent? Can you still use this formula?
- Tue Feb 19, 2019 8:02 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Factors
- Replies: 2
- Views: 284
Factors
What factors influence the value of delta G in a reaction? Is it mainly influenced by what's present in the reaction or what is produced/given off?
- Tue Feb 19, 2019 7:59 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Indications
- Replies: 3
- Views: 398
Indications
Are there any characteristics of a reaction that would hint at the value of delta G being positive/negative or larger/smaller?
- Mon Feb 04, 2019 1:26 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Examples of Open Closed Isolated
- Replies: 5
- Views: 2083
Re: Examples of Open Closed Isolated
An open system is any that has openings where matter and heat can be transferred into/out of, such as an open top cup. A closed system is one that doesn't have any physical openings, but can transfer heat through its walls, such as a closed box. And an isolated system is one that doesn't have any ph...
- Mon Feb 04, 2019 1:15 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed and Isolated
- Replies: 10
- Views: 753
Re: Closed and Isolated
If it's closed then matter can't be added or taken away from the system, such as a closed box, but heat can still transfer into and out of it. If the system is isolated, then it's like a highly insulated box where matter and heat both can't be transferred into or out of the system.
- Mon Feb 04, 2019 1:12 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Outside Factors
- Replies: 1
- Views: 216
Outside Factors
Is there ever a situation where the change in internal energy is affected by factors other than heat and work?
- Mon Jan 28, 2019 7:35 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Extensive Vs Intensive Properties
- Replies: 1
- Views: 245
Extensive Vs Intensive Properties
What's the difference between extensive and intensive properties (heat capacity vs specific heat capacity) and does it change how/when we use those things?
- Mon Jan 28, 2019 7:27 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity
- Replies: 5
- Views: 504
Heat Capacity
Since heat capacity and specific heat capacity are one calculation apart, when asked about heat capacity in a question should we assume they're asking about specific heat capacity? Will normal heat capacity ever be asked about?
- Mon Jan 28, 2019 7:16 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calorimetry
- Replies: 5
- Views: 571
Calorimetry
What's the difference between normal calorimetry and bomb calorimetry? Does normal just have constant pressure but anything else can change and bomb is the same idea but only volume can change?
- Mon Jan 21, 2019 7:15 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Salt Solution
- Replies: 5
- Views: 686
Salt Solution
When you're calculating the pH of a salt solution do you always ignore the ions that don't take part in the reaction and dissolve away?
- Mon Jan 21, 2019 7:13 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Ionized vs Deprotonated
- Replies: 2
- Views: 515
Ionized vs Deprotonated
What's the difference between % ionized vs % deprotonated? Are there different names that mean the same calculation?
- Mon Jan 21, 2019 7:11 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Percent Protonation
- Replies: 6
- Views: 547
Percent Protonation
For percent protonation is it the final concentration of the weak base over its initial concentration x100 or the concentration of the conjugate acid over the initial concentration of the weak base x100?
- Mon Jan 14, 2019 8:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Weak Acid/Base Calculations
- Replies: 2
- Views: 329
Weak Acid/Base Calculations
How do we find the pH/pOH and concentrations of H30+ and OH- of a reaction with a weak acid/base that doesn't completely dissociate?
- Mon Jan 14, 2019 8:18 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: change in pressure
- Replies: 4
- Views: 444
Re: change in pressure
Because of the same idea, if there are more moles on the right and pressure is added then the reaction will try to balance itself out by favoring the reverse reaction and going back to reactants.
- Mon Jan 14, 2019 1:12 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: ICE Table [ENDORSED]
- Replies: 3
- Views: 490
Re: ICE Table [ENDORSED]
The subscripts don't matter in the ice table, only the coefficients before the molecules of product or reactant affect the change in molarity in the ice table calculations and the powers the molarities are to in the final equilibrium constant calculation.
- Wed Jan 09, 2019 10:18 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K
- Replies: 4
- Views: 323
Re: K
If you're dealing with solutions that have a given concentration, then you use Kc, but if you're dealing with gases and partial pressures, you use Kp.
- Wed Jan 09, 2019 10:16 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium Constant
- Replies: 2
- Views: 140
Equilibrium Constant
How do you calculate the equilibrium constant if you're given a mix of concentrations and pressures? Or will that never happen?
- Wed Jan 09, 2019 10:14 am
- Forum: Ideal Gases
- Topic: Ideal vs Real Gas
- Replies: 6
- Views: 550
Ideal vs Real Gas
What's the physical and chemical difference between ideal and real gases?
- Fri Dec 07, 2018 1:22 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: pKa and Ka
- Replies: 3
- Views: 360
Re: pKa and Ka
Ka tells you how well an acid dissolves in solution, but when simplified into pKa, the smaller the value is the stronger the acid, as strong acids dissociate more in solution.
- Fri Dec 07, 2018 1:18 pm
- Forum: Lewis Acids & Bases
- Topic: Determining Factors
- Replies: 2
- Views: 310
Determining Factors
What aspects of an acid/base's lewis structure tells you if it's an acid or base?
- Fri Dec 07, 2018 1:16 pm
- Forum: Conjugate Acids & Bases
- Topic: Water as an Acid/Base
- Replies: 20
- Views: 1598
Water as an Acid/Base
Is water's identity as an acid or base solely determined by being the opposite of what it's reacting with?
- Fri Nov 30, 2018 2:23 pm
- Forum: Hybridization
- Topic: Determining Factors
- Replies: 3
- Views: 429
Determining Factors
Is hybridization always based off of the number of bonds or lone pair electrons around the central atom or are there other factors that could affect it?
- Fri Nov 30, 2018 2:19 pm
- Forum: Bronsted Acids & Bases
- Topic: Bronsted vs Lewis
- Replies: 3
- Views: 340
Bronsted vs Lewis
What are the main differences between Bronsted and Lewis acids and bases?
- Fri Nov 30, 2018 2:16 pm
- Forum: Lewis Acids & Bases
- Topic: Strength
- Replies: 3
- Views: 361
Strength
What factors determine how strong or weak an acid/base is?
- Sun Nov 25, 2018 11:42 am
- Forum: Hybridization
- Topic: Test 3
- Replies: 13
- Views: 933
Re: Test 3
I think we don't have to know how to draw the 3-D hydbridization diagrams, but that we have to know how to make the electron configuration and understand how it works.
- Sun Nov 25, 2018 11:39 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bonds
- Replies: 2
- Views: 189
Bonds
Do single, double and triple bonds always have to be made from the exact number of sigma and pi bonds each time, or can they be made with other ratios of the two?
- Sun Nov 25, 2018 11:35 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polarity
- Replies: 6
- Views: 582
Polarity
Is a VSEPR model shape always polar if the central atom in the lewis structure has lone pairs? Or can lone pairs be symmetrical and cancel out charges to make the molecule non-polar?
- Wed Nov 14, 2018 5:13 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Shape
- Replies: 4
- Views: 433
Molecular Shape
What are all the factors that affect molecular shape determined from the lewis structure?
- Wed Nov 14, 2018 5:09 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Strengths
- Replies: 5
- Views: 447
Bond Strengths
Why are ionic bonds stronger than hydrogen bonds?
- Wed Nov 14, 2018 4:15 pm
- Forum: Octet Exceptions
- Topic: Resonance Structures
- Replies: 7
- Views: 850
Re: Resonance Structures
When you make a lewis structure that has resonance you need to draw all the resonance structures with double-sided arrows between them, as the correct lewis structure for the molecule is actually a hybrid of them all and not any single one.
- Wed Nov 07, 2018 1:22 pm
- Forum: Octet Exceptions
- Topic: Central atoms with more than 8 electrons
- Replies: 3
- Views: 1775
Re: Central atoms with more than 8 electrons
Any element in the third period or below can have an expanded octet with more than 8 valence electrons. They do have a d-orbital and are large enough to stably hold more electrons in their shells. But, if you have more that 8 electrons in your lewis structure for a certain molecule, try to make sure...
- Wed Nov 07, 2018 1:19 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Ideal lewis structure with Formal Charge
- Replies: 4
- Views: 2369
Re: Ideal lewis structure with Formal Charge
To find the most ideal lewis structure you want to create one where the base element, or element in the center of the structure, has a formal charge of 0. If the overall molecule is an ion with a charge, then try to have the outer elements which are connected to the main base be the ones that carry ...
- Wed Nov 07, 2018 1:16 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge
- Replies: 11
- Views: 1347
Re: Formal Charge
Formal charges don't always have to be zero, as if a molecule is an ion with a certain positive or negative charge, then at least one element in the structure must have a charge that makes all of the formal charges of the elements in the structure add up to zero. But, to find the most stable form of...
- Tue Oct 30, 2018 3:45 pm
- Forum: Octet Exceptions
- Topic: central atoms with more than 4 bonds
- Replies: 3
- Views: 507
Re: central atoms with more than 4 bonds
Lavelle said that elements in the third period and below are able to hold more than 8 valence electrons and stay stable. Since sulfur (S) is in the third period it can follow this rule, which is why it can hold 12 electrons.
- Tue Oct 30, 2018 3:41 pm
- Forum: Octet Exceptions
- Topic: octet rule exceptions?
- Replies: 5
- Views: 797
Re: octet rule exceptions?
Lavelle said that elements in the third period or below are able to hold more than 8 valence electrons, typically sulfur, silicon, phosphorus and chlorine are the main ones known to have this ability.
- Tue Oct 30, 2018 3:32 pm
- Forum: Resonance Structures
- Topic: Resonance hybrid
- Replies: 2
- Views: 251
Re: Resonance hybrid
If a molecule has resonance you must draw each possible lewis structure, bracket each structure, and draw double-sided arrows between them. In real life no single resonance lewis structure is "right," but the molecule is a hybrid of all the possibilities.
- Fri Oct 26, 2018 1:40 pm
- Forum: Lewis Structures
- Topic: Octet Rule
- Replies: 5
- Views: 861
Re: Octet Rule
Most elements need to have a complete octet of valence electrons in order to survive and be stable. Only certain elements such as sulfur, phosphorus, chlorine and silicon can hold more than 8 valence electrons and form a stable expanded octet and elements such as hydrogen can only handle 2 valence e...
- Fri Oct 26, 2018 1:20 pm
- Forum: Lewis Structures
- Topic: Drawing Lewis Structures
- Replies: 3
- Views: 513
Re: Drawing Lewis Structures
Atoms can be bonded together in the lewis structure in any pattern, but each main element, other than H, needs to have a full set of 8 electrons by the end. By using single, double and triple bonds, you can use the amount of valence electrons available and start to form the structure, experimenting ...
- Fri Oct 26, 2018 1:16 pm
- Forum: Lewis Structures
- Topic: Lewis Dot Order
- Replies: 10
- Views: 1266
Re: Lewis Dot Order
There is no particular order that you have to put the elements of the structure in, as long as each main element has a full set of 8 electrons, other than elements like H which only need 2 electrons.
- Mon Oct 15, 2018 4:32 pm
- Forum: SI Units, Unit Conversions
- Topic: Unit Conversions
- Replies: 3
- Views: 512
Re: Unit Conversions
Just remember that the SI base units are kilograms(kg) for mass, meters(m) for length and seconds(s) for time. Then make sure you know the prefixes, such as mega, kilo, deci, centi, milli, etc, and the powers of ten from the original SI unit they represent.
- Mon Oct 15, 2018 4:26 pm
- Forum: Significant Figures
- Topic: Module: Molarity #15
- Replies: 6
- Views: 1276
Re: Module: Molarity #15
Since 0.25 isn't followed by any other decimal values after the 5, normally this answer would and should be rounded to 0.2 since both of the values getting you to this answer had only one significant figure.
- Mon Oct 15, 2018 4:19 pm
- Forum: Properties of Electrons
- Topic: Photon Momentum
- Replies: 1
- Views: 346
Photon Momentum
In today's lecture we talked about De Broglie's Wave Equation, I don't understand how a photon can have momentum when it doesn't have a mass?
- Wed Oct 10, 2018 11:54 am
- Forum: Balancing Chemical Reactions
- Topic: Where to start [ENDORSED]
- Replies: 10
- Views: 1424
Re: Where to start [ENDORSED]
I always start by balancing the more unique elements that only occur once on each side of the reaction equation. I then balance the more common elements that show up multiple times throughout the equation, such as H, O and C. After that I can finish balancing the equation with any elements that are ...
- Wed Oct 10, 2018 11:49 am
- Forum: Limiting Reactant Calculations
- Topic: How to find the limiting reactant easily and quickly
- Replies: 5
- Views: 13921
Re: How to find the limiting reactant easily and quickly
When I find the limiting reactant I always use the molar masses of the reactants to find how many moles of each the reaction has. After I do that I look at the molar ratios between the reactants to see how much of each is needed to react with the other. In the example 2A + 1B --> 3C, for every 2 mol...
- Wed Oct 10, 2018 11:43 am
- Forum: Limiting Reactant Calculations
- Topic: Percent Yield [ENDORSED]
- Replies: 13
- Views: 2918
Re: Percent Yield [ENDORSED]
Actual yield is the amount of product formed when performing the reaction in real life, theoretical yield is the maximum predicted amount of that same product formed if the reaction completely uses up its limiting reactant and doesn't lose any product due to error. The actual yield will almost alway...
- Thu Oct 04, 2018 1:02 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: molarity conversion
- Replies: 7
- Views: 462
Re: molarity conversion
When using the formula m1v1=m2v2 always make sure the volume values you put in are in liters, and then if the question asks for the answer to be in mL or another form, convert from liters at the end.
- Thu Oct 04, 2018 1:00 pm
- Forum: Significant Figures
- Topic: Sig Figs... when to round?
- Replies: 7
- Views: 898
Re: Sig Figs... when to round?
Never round off by sig figs in the middle of the problem, but keep in mind the sig figs of each new value you are continually using in a problem. At the end of the problem look at the supposed sig figs the values you used had and then round off to that number of sig figs.
- Thu Oct 04, 2018 12:54 pm
- Forum: Balancing Chemical Reactions
- Topic: Order of balancing an equation
- Replies: 8
- Views: 682
Re: Order of balancing an equation
As others have said, I usually start by balancing the unique elements that only occur once that are not found in multiple reactants or products, then continue by balancing the more common elements that are spread throughout the equation, and finish by balancing elements that are standing alone, such...