Search found 149 matches
- Wed Mar 10, 2021 12:20 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Pre-equilibrium approach [ENDORSED]
- Replies: 3
- Views: 225
Re: Pre-equilibrium approach [ENDORSED]
The reason we have to do an extra process for if the second step is slow is because often times we have an intermediate, so we need to get rid of it. This makes sense because we never add intermediates to the reaction, they just form in the middle of the reaction. Therefore, they shouldn't be includ...
- Wed Mar 10, 2021 12:17 pm
- Forum: General Rate Laws
- Topic: Rate Law
- Replies: 6
- Views: 383
Re: Rate Law
He got it from the coefficient in front of NO2 (i.e. 2) and 1/a where a = 2 is how he got it.
- Wed Mar 10, 2021 12:16 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: What was your favorite chem topic?
- Replies: 137
- Views: 8518
Re: What was your favorite chem topic?
Kinetics was fun! It was most fun because you can see how topics can relate to your field of study.
- Wed Mar 10, 2021 12:15 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Homework #16
- Replies: 5
- Views: 275
Re: Homework #16
K = k/k' which means the rate of the forward reaction over the rate of the reverse reaction, due to how the concentrations cancel out!
- Wed Mar 10, 2021 12:14 pm
- Forum: General Rate Laws
- Topic: Final Exam
- Replies: 19
- Views: 759
Re: Final Exam
Focuses on everything from class, although I don't know if some things will be focused on more than others.
- Sun Mar 07, 2021 7:57 pm
- Forum: Student Social/Study Group
- Topic: Spring Break
- Replies: 53
- Views: 3152
Re: Spring Break
Definitely going to take some time to just relax and exercise. Haven't been able to do that as much lately.
- Sun Mar 07, 2021 7:56 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook 6N.1
- Replies: 3
- Views: 393
Re: Textbook 6N.1
I found E˚ based on the way the reaction was written (Ti is being reduced so it is the cathode as an example) and then used lnK = nFE˚/RT to solve.
- Sun Mar 07, 2021 7:51 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Inert Conductors
- Replies: 5
- Views: 326
Re: Inert Conductors
Pt is often used when there is no conductor solid. For example, if there was Fe+3 (aq) in solution, you'd still need to add Pt (s) because you need a solid conductor of metal to transfer electrons.
- Sun Mar 07, 2021 7:48 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Determining Anode vs Cathode
- Replies: 23
- Views: 872
Re: Determining Anode vs Cathode
I think if they write out the actual equation, you can see which one is being reduced and label it as the cathode. If asked which one would create a spontaneous reaction, you'd compare E˚ values and see which one is more positive and label it as the cathode.
- Sun Mar 07, 2021 7:47 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: K value
- Replies: 20
- Views: 788
Re: K value
K is just the rate, so it will always be positive. You can think of it as negative when something is decomposing, but the actual sign needs to be positive.
- Sun Feb 28, 2021 7:28 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling Week 7/8 Question 3
- Replies: 5
- Views: 264
Re: Sapling Week 7/8 Question 3
Strange. I am also getting the same answer as you. Make sure it is asking for the reaction in basic solutions? That is the only error I could think of. Maybe Sapling is just being glitchy.
- Sun Feb 28, 2021 7:23 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Reducing agent strength
- Replies: 2
- Views: 172
Re: Reducing agent strength
To add on the other answer, I believe that the more positive E˚reduction is, the more likely the substance will be to be reduced and the less positive it is, the easier it is to oxidize.
- Sun Feb 28, 2021 7:22 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Sapling #16 Wk7/8
- Replies: 8
- Views: 1654
Re: Sapling #16 Wk7/8
Remember that E doesn't get affected because if we increase the amount of "stuff" in a redox reaction, we will increase both the potential energy and the charge and therefore the ratio will remain the same.
- Sun Feb 28, 2021 7:20 pm
- Forum: Student Social/Study Group
- Topic: Sapling weeks 7-8
- Replies: 1
- Views: 109
Re: Sapling weeks 7-8
I remember when I did this problem, I forgot to add OH- to both sides, not just one. That may be what is happening here, but I was left with 2 H+ on the right side of the equation, so I added 2 OH- to the right and left sides of the equations. Hope that helps a bit!
- Sun Feb 28, 2021 7:18 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Reactions
- Replies: 22
- Views: 965
Re: Balancing Reactions
I think as long as your reactants and products are on the right side, it doesn't matter what order the individual reactants/products are in. I am referring to balancing equations, so I am not sure if you are referring to something else.
- Sun Feb 28, 2021 7:14 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridges
- Replies: 41
- Views: 2921
Re: Salt Bridges
If there was no salt bridge, the charges from the reductions and oxidations build up (positive on the side of the anode and negative on the side of the cathode) and therefore the reduction potential is much smaller. The larger the difference in charges, the easier it is to transfer electrons. Theref...
- Sun Feb 21, 2021 11:20 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: State functions
- Replies: 18
- Views: 788
Re: State functions
If you can do X(final) - X(initial), it is usually a state function! That's how I usually think about it.
- Sun Feb 21, 2021 4:55 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: When does delta H = q?
- Replies: 15
- Views: 4826
Re: When does delta H = q?
When there are constant pressure conditions. ∆H = q under these conditions because if the pressure is constant, the volume is changing, and therefore the heat put into the system is used for expansion work. Therefore, the total q energy supplied will equal the ∆H of the system (assuming no other typ...
- Sun Feb 21, 2021 4:51 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: q and w for an Isolated System
- Replies: 19
- Views: 3273
Re: q and w for an Isolated System
∆U is always 0 for an isolated system, because if you think about it, an isolated system cannot exchange matter or energy with its surroundings. Therefore, its internal energy doesn't change. It's interesting to think, however, if this is only theoretical. Most "isolated" systems still los...
- Sun Feb 21, 2021 4:49 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff equation
- Replies: 13
- Views: 1443
Re: Van't Hoff equation
The Van't Hoff equation is used when you have two different temperature values, and you want to find the K at the new temperature. -RTlnK is used when you want to find the K value at a specific, constant temperature. If your temperature is not changing, then you can use it.
- Sun Feb 21, 2021 4:48 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Q and K
- Replies: 40
- Views: 2616
Re: Q and K
If Q < K, then you know the reaction will proceed in the forward direction (towards products) because if Q is less than K, the denominator of Q is larger. Since we know the denominator is the reactants, this means that there are more reactants than there should be at equilibrium. Using the same logi...
- Sun Feb 21, 2021 4:46 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Open vs closed
- Replies: 31
- Views: 2755
Re: Open vs closed
Open systems allow for both matter and energy to be exchanged with the surroundings. An example of this is a coffee. The cup allows for the exchange of heat with surroundings, and you can add in milk or sugar. A closed system allows only for energy to be exchanged. Think about that coffee cup and th...
- Sun Feb 14, 2021 4:17 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: 4H 5 part b
- Replies: 1
- Views: 76
Re: 4H 5 part b
You can see in this case that 1-pentene has a less rigid structure because it is not confined to a certain shape and is more flexible, and therefore has more possible positions and should have a higher entropy.
- Sun Feb 14, 2021 4:15 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Homework #19
- Replies: 4
- Views: 244
Re: Homework #19
You need to use the equation ∆G = ∆G˚ + RT*lnQ, You are given ∆G˚ and the values to find Q, so plug those in and you should get ∆G!
- Sun Feb 14, 2021 4:13 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Sapling 7
- Replies: 3
- Views: 220
Re: Sapling 7
Basically you need to convert from W to J and then your enthalpy is your J divided by your mol (take the grams and convert them to moles). Then you have ∆H(vap). In order to find ∆S(vap), you need to use the equation ∆S = ∆H/T and make sure that your T is in Kelvin and not ˚C
- Sun Feb 14, 2021 4:11 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Sapling #12
- Replies: 2
- Views: 252
Re: Sapling #12
First we need to think about this equation: ∆G˚ = ∆H˚ – T∆S˚ Spontaneous at all temperature: ∆H = – and ∆S = +. If you have a negative ∆H, and a positive ∆S, you will be subtracting a negative value from a negative value, leading to a negative value overall and therefore ∆G˚ is negative. This means ...
- Sun Feb 14, 2021 4:04 pm
- Forum: Calculating Work of Expansion
- Topic: Textbook Problem 4B.13
- Replies: 6
- Views: 436
Re: Textbook Problem 4B.13
So basically one of these processes is reversible and the other isn't. Therefore, you need different equations for work. For reversible, you would use w = -nRT*ln(Vf/Vi) and for irreversible expansion w = -Pex*∆V. You can use the initial conditions given to find n!
- Sun Feb 14, 2021 4:02 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: kJ/K*mol vs J/K*mol
- Replies: 7
- Views: 290
Re: kJ/K*mol vs J/K*mol
Yep you can change R into kJ instead of J! It works.
- Sun Feb 07, 2021 4:08 pm
- Forum: Ideal Gases
- Topic: R ideal gas constant
- Replies: 31
- Views: 1955
Re: R ideal gas constant
Depending on the units given, you'll use different R values OR you could convert other things in your equation to get them to the same units as your desired R. Just be careful when using 0.0821 L*atm/mol*K because you need to use 101.325 J = 1 L*atm to get J, while 8.314 J/mol*K will give you J righ...
- Sun Feb 07, 2021 4:06 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Quick 4A.5 Question
- Replies: 1
- Views: 96
Re: Quick 4A.5 Question
I don't think an irreversible expansion can ever do more work, because a reversible expansion by definition is the infinitesimal decrease of external pressure, so the gas does MAX amount of work. There can never be a case where irreversible does more work.
- Sun Feb 07, 2021 4:05 pm
- Forum: Phase Changes & Related Calculations
- Topic: Vapor vs gas
- Replies: 121
- Views: 8894
Re: Vapor vs gas
Vapor and gas are the same thing.
- Sun Feb 07, 2021 4:02 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Temperatue in delta S = qREV/T
- Replies: 3
- Views: 123
Re: Temperatue in delta S = qREV/T
Yes the temperature must be held constant and therefore be isothermal.
- Sun Feb 07, 2021 4:01 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling #19 - Week 3/4
- Replies: 3
- Views: 184
Re: Sapling #19 - Week 3/4
I think we kind of do, because it says 0.5 L, and the L of reactants add up to create 0.5 L. Since it's a calorimeter, we know that q(cal) = -q(rxn) so therefore we don't really need any of the other things. We just need to make sure that there are 0.5 L because that is what the calorimeter is calib...
- Sun Feb 07, 2021 3:59 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: sapling week 3/4 question 18
- Replies: 1
- Views: 41
Re: sapling week 3/4 question 18
Your temperature is wrong. The change is 20.1 K, therefore that is the ∆T. You do not need to subtract anything for the T. Hope that helps!
- Sun Jan 31, 2021 8:03 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm 1
- Replies: 9
- Views: 427
Re: Midterm 1
Usually about a week!
- Sun Jan 31, 2021 5:29 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Strong Acids/Bases
- Replies: 19
- Views: 1281
Re: Strong Acids/Bases
Strong acids are: HCl, HI, HBr, H2SO4, HNO3, HClO4, and HClO3. Everything else in this class is a weak acid. Strong bases include the first and second groups of metal oxides, such as NaOH, and Ca(OH)2. Everything else is a weak base. These should be memorized, especially in the context of acid base ...
- Sun Jan 31, 2021 5:26 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: polyprotic acids
- Replies: 10
- Views: 589
Re: polyprotic acids
I believe you can ignore the Ka2 if it is << Ka1, and this is true for most acids EXCEPT H2SO4, so just use Ka1 and Ka2 for that acid. This is because H2SO4 is strong, so it's first Ka essentially goes to completion, while the other acids are weak, so H+ does not equal HA. And the Ka2 is smaller bec...
- Sun Jan 31, 2021 5:23 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: steam causing burns
- Replies: 40
- Views: 1212
Re: steam causing burns
The way that I understood it is that at the time the water reaches 100 ˚C, the energy supplied doesn't go into raising the temperature of the gas, but rather the bonds between water molecules so that they may be converted to gas molecules. Then, when all the liquid water molecules have been converte...
- Sun Jan 31, 2021 4:31 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Enthalpy vs. Entropy
- Replies: 18
- Views: 575
Re: Enthalpy vs. Entropy
Enthalpy is the heat or energy contained, such as in bonds (where if ∆H is negative, the reaction is exothermic and so the bonds have lower enthalpy than the reactants meaning they are more stable). Entropy is the measure of disorder. According to the laws of thermodynamics and Muse, the entropy of ...
- Sun Jan 31, 2021 4:28 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated System
- Replies: 16
- Views: 656
Re: Isolated System
Vacuums can be isolated systems, but not all isolated systems are vacuums.
- Sun Jan 31, 2021 4:26 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2974333
Re: Post All Chemistry Jokes Here
When Q = K
- Sun Jan 24, 2021 9:05 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Spectator Ions
- Replies: 6
- Views: 708
Re: Spectator Ions
I think that spectator ions are just there in solution, but they are present on both sides of the equation. So if you had Na2SO4, you would break it up into 2 Na+ and SO4-2 and those are ions, which if they appear on both sides of the equation they can cancel out. It's often called a net ionic equat...
- Sun Jan 24, 2021 9:03 pm
- Forum: Phase Changes & Related Calculations
- Topic: Work on vs by
- Replies: 4
- Views: 169
Re: Work on vs by
Work done on a system is positive, and when it does work it is negative because it is losing energy. Are we supposed to know q and w for the first midterm exam?
- Sun Jan 24, 2021 6:36 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert Gases and Le Chatelier's Principle
- Replies: 6
- Views: 480
Re: Inert Gases and Le Chatelier's Principle
Nope! The addition of an inert gas might slow down the reaction of equilibrium (i.e equilibrium will take longer to achieve because of competing collision) but it will not change equilibrium because the concentrations of the gases that are reacting do not change. Inert gases hardly ever react, so th...
- Sun Jan 24, 2021 4:43 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium Constant Sig Figs
- Replies: 3
- Views: 89
Re: Equilibrium Constant Sig Figs
I believe so for both, but on our midterms and final, Lavelle doesn't ask you to round everything to the exact sig figs (for example, there won't be answer choices like A). 2.00 or B) 1.99. It'll be obvious if your answer is there or not, but overall I believe they do impact sig figs.
- Sun Jan 24, 2021 4:40 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Increase in Pressure
- Replies: 31
- Views: 698
Re: Increase in Pressure
Gases because they are the only ones that have partial pressures. Aqueous, liquids, and solids do not have partial pressures so increasing the system's pressure won't do anything to them or their concentrations.
- Mon Jan 18, 2021 5:25 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: finding conc. from Kc
- Replies: 3
- Views: 95
Re: finding conc. from Kc
Happened to me as well. Make sure at the beginning of any problem to check if the equation is balanced or not. Even if there are already numbers in front of the molecules, this may be a trick so always double check!
- Mon Jan 18, 2021 5:20 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Textbook Question Kw
- Replies: 5
- Views: 183
Re: Textbook Question Kw
We know that in water, the concentration of H3O+ is 1.0 x 10^-7 M and the concentration of OH- is also 1.0 x 10^-7. These two concentrations multiplied together give Kw. In water, if an H3O+ molecule is formed, then an OH- one must be formed as well. Therefore, their concentrations must be equal.
- Sun Jan 17, 2021 10:06 pm
- Forum: Ideal Gases
- Topic: Kp?
- Replies: 30
- Views: 916
Re: Kp?
Yep, only for gases because remember that solids and liquids cannot have partial pressures. Therefore, partial pressures only apply to gases.
- Sun Jan 17, 2021 10:32 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Autoprotolysis Reaction and Kw
- Replies: 3
- Views: 74
Re: Autoprotolysis Reaction and Kw
K can be changed with temperature! It doesn't change with pressure or a change in concentration but temperature is a different story. Heat is like a reactant in an endothermic process, so adding heat would shift the process to the right (the forward reaction) and favor products, leading to a larger ...
- Sun Jan 17, 2021 10:28 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Weak versus Strong Acid and Base
- Replies: 10
- Views: 506
Re: Weak versus Strong Acid and Base
Yep! Just memorize them! Although anything organic will be a weak acid, and for bases the only strong ones are with cations from groups 1 and 2. Everything else is weak. I think there are some strong acids that we do not memorize in this class that exist in nature, but we don't really focus on them ...
- Sun Jan 17, 2021 10:25 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling #10, WK 1
- Replies: 8
- Views: 334
Re: Sapling #10, WK 1
I believe you now have the equilibrium concentrations, but then need to add 1 to NO2, so now your equilibrium concentrations become your initial, and that NO2 + 1 mole is also your initial. Then set up an ICE box and solve. However, also remember that you are adding more product, so the reaction wil...
- Sun Jan 17, 2021 10:17 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium constant
- Replies: 4
- Views: 87
Re: Equilibrium constant
well if the concentration of a reactant or product increases or decreases, the system will shift to create equilibrium again. Remember that k is just a constant of product ratio over reactant ratio, so there may be more or less reactants or products, but their overall ratio will remain the same. The...
- Sun Jan 17, 2021 10:12 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Acid and Bases Lecture #6
- Replies: 4
- Views: 229
Re: Acid and Bases Lecture #6
As others have said, the concentration of x is both the concentration of CH3COO- and H3O+ due to their coefficients. If it was 3 CH3COO-, it would be initial - 3x.
- Fri Jan 08, 2021 8:29 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Stability
- Replies: 8
- Views: 262
Re: Stability
I agree with the above poster. After doing some problems, I realized that even if the Kc constant is really small, Q can still be smaller, so overall the products are not as stable as the reactants but there still needs to be equilibrium, so products are formed even if they are not favored. When equ...
- Fri Jan 08, 2021 8:22 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Change in Amount of Product
- Replies: 4
- Views: 95
Re: Change in Amount of Product
That's a way of doing it I think! I personally stumbled upon this question as well, and what I did was I took the equilibrium concentrations of all products and reactants and made that the initial concentrations, and then just changed the initial concentration of what you are asking, in this case, I...
- Fri Jan 08, 2021 8:19 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert Gas
- Replies: 5
- Views: 92
Re: Inert Gas
Inert gases are the nobles gases, named inert because they do not react easily. It's not a gas that isn't in the reaction, because if you add another gas, it may somehow react with the other gases in the equation and form different products. However, inert gases are very unlikely to react with the o...
- Fri Jan 08, 2021 8:18 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Gibbs Free Energy
- Replies: 2
- Views: 94
Re: Gibbs Free Energy
Yes it will be covered later on in thermodynamics. For right now, I believe it is used to figure out if a reaction is exothermic (and Gibbs free energy is negative) or endothermic (where Gibbs free energy is positive).
- Fri Jan 08, 2021 8:16 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling HW Week 1 #5
- Replies: 2
- Views: 106
Re: Sapling HW Week 1 #5
Yep! you need to manipulate the equations. Then you need to cancel out like terms until you get the original equation. Whenever you manipulate something, you must change the K value. When multiplying, say by 2, you need to raise K to the power of the number you multiplied, so K^2. If you flipped the...
- Thu Jan 07, 2021 11:23 am
- Forum: Ideal Gases
- Topic: PV=nRT
- Replies: 74
- Views: 4204
Re: PV=nRT
P is pressure, and the SI unit is Pascals but often we use bar or atm (be careful to look out for this because it will change which gas constant R you use) V is volume in liters or m^3 n is the moles R is the gas constant (varies with pressure and volume) T is the temperature (in Kelvin) conversion ...
- Tue Jan 05, 2021 11:43 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: change in pressure
- Replies: 8
- Views: 393
Re: change in pressure
If the moles were equal, the equilibrium wouldn't shift anywhere. Also, if the problems says that the pressure is increased by adding an inert gas, the equilibrium wouldn't shift either, regardless of whether there are less moles on one side of the equation. I believe that the pressure must change d...
- Mon Jan 04, 2021 12:18 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: If K is large...
- Replies: 11
- Views: 1030
Re: If K is large...
Their concentrations could be equal, but that is not the rule for equilibrium. The concentration of reactants could be 0.1 M and the concentration for products could be 0.6 M. The key is that the forward reaction and reverse reactions are occurring at the same rate. I'm not sure about a direct examp...
- Wed Dec 16, 2020 9:55 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2974333
Re: Post All Chemistry Jokes Here
I'm not sure if this one has been done before :D Cop: Do you have any idea how fast you were going? Heisenberg: No, but I know exactly where I am. Cop: You were doing 55 in a 30. Heisenberg: Great, now I'm lost. Cop: What's in the trunk? Schrodinger: My cat. The cop opens the trunk. Cop: Your cat is...
- Tue Dec 15, 2020 9:50 am
- Forum: Identifying Acidic & Basic Salts
- Topic: What is a Salt?
- Replies: 9
- Views: 605
Re: What is a Salt?
It's a cation and an anion that are attracted to one another through ionic bonds! Such as NaCl, KCl, etc
- Tue Dec 15, 2020 9:45 am
- Forum: Naming
- Topic: ONO vs. NO2
- Replies: 9
- Views: 3148
Re: ONO vs. NO2
It is different in the name. ONO is nitrito while NO2 is nitro.
- Tue Dec 15, 2020 9:41 am
- Forum: Conjugate Acids & Bases
- Topic: What is the difference between a lewis acid and bases and Bronsted acids and bases?
- Replies: 7
- Views: 471
Re: What is the difference between a lewis acid and bases and Bronsted acids and bases?
Lewis acids and bases have to do with electrons, while the Bronsted definition includes H+ and OH- ions. Lewis acids accept electrons, Lewis bases donate electrons, Bronsted acids donate H+ and form H3O+ in solution and Bronsted bases accept H+ ions and form OH- ions solution.
- Tue Dec 15, 2020 9:37 am
- Forum: Lewis Acids & Bases
- Topic: KA and pKA
- Replies: 19
- Views: 894
Re: KA and pKA
The larger the Ka value, the stronger the acid because this means that the products outweigh the reactants, and the lower the pKa.
- Tue Dec 15, 2020 9:36 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Balmer and Lyman Series
- Replies: 6
- Views: 412
Re: Balmer and Lyman Series
Well, the actual wavelength number will depend on the n value, so yes, the n value determines which series you use.
- Tue Dec 15, 2020 9:34 am
- Forum: Naming
- Topic: Ligand use -ate
- Replies: 18
- Views: 967
Re: Ligand use -ate
You ate when the ligand has a negative charge on the outside of the brackets.
- Tue Dec 15, 2020 9:08 am
- Forum: Air Pollution & Acid Rain
- Topic: Why does acid rain exist
- Replies: 16
- Views: 1041
Re: Why does acid rain exist
H2O in the air reacts with SO2, CO2, and NO2 to form acids that then dissociate and lower the pH of the water. It is because of pollutants, and some things that can be done is to lower CO2 emissions and use clean coal instead of dirty coal.
- Tue Dec 15, 2020 12:32 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Acid/base rules [ENDORSED]
- Replies: 3
- Views: 318
Re: Acid/base rules [ENDORSED]
Just to also add on, I believe that small, positively charged elements, such as Al+3, create a more acidic solution and are known as Lewis acids because they pull electron density towards them, and make the OH bond easier to break.
- Sun Dec 06, 2020 10:25 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: G19
- Replies: 3
- Views: 222
Re: G19
Your original concentration was 0.366 mol/L, meaning that if you took out 25 mL you would have 0.00915 moles. Then, 0.00915 moles/.125 L, because the total volume is 125 mL, not 125 + 25 mL, since the volume flask cannot exceed 125 mL, giving you a 0.0732 M. Hope this helps!
- Sun Dec 06, 2020 10:47 am
- Forum: General Science Questions
- Topic: State of a molecule
- Replies: 6
- Views: 538
Re: State of a molecule
Nope! I think it would be impossible to know. When given H2O, it could be in the gas, liquid, or solid phase but unless we're given the state or temperature, we won't know just from the Lewis structure (because remember the different states are based on intermolecular forces, so the overall shape of...
- Sun Dec 06, 2020 10:46 am
- Forum: Lewis Acids & Bases
- Topic: Lewis Acid
- Replies: 4
- Views: 334
Re: Lewis Acid
Hi! Yep, Lewis acids accept electrons! Acids will have a different pH depending on what they are dissolved in. Remember that it is not HCl that is acidic, but it acts as an acid, meaning that in water there will actually be very little amounts of HCl and more H+ and Cl- ions. In another substance, t...
- Sun Dec 06, 2020 10:40 am
- Forum: Naming
- Topic: Correct name for Na[Co(NH3)3Cl3]?
- Replies: 8
- Views: 8990
Re: Correct name for Na[Co(NH3)3Cl3]?
I think you also have to include sodium at the beginning. It would be sodium triamminetrichlorocobaltate (II) (Co has a +2 charge because you get a -1 overall charge outside the brackets due to only a +1 charge from Na to balance it out, and the 3 Cl- atoms give a -3 charge, meaning that to get an o...
- Sun Dec 06, 2020 10:37 am
- Forum: Naming
- Topic: Use of Toolbox 9C.1 on Final
- Replies: 3
- Views: 236
Re: Use of Toolbox 9C.1 on Final
I am pretty sure we'll need to memorize that list. As for the toolbox, we won't be given that; we need to memorize the formula to how to write the names of chemical compounds.
- Sun Dec 06, 2020 10:35 am
- Forum: Naming
- Topic: Naming H2O
- Replies: 11
- Views: 586
Re: Naming H2O
I think (OH2) is more common, but since the final is multiple choice, you don't have to worry about it because you'll see how it'll be written.
- Sun Dec 06, 2020 10:34 am
- Forum: Naming
- Topic: Amphoteric Compund
- Replies: 5
- Views: 157
Re: Amphoteric Compund
It's a compound that can act as an acidic or a basic compound, depending on what it interacts with. For example, water is amphoteric because it can behave as an acid or a base. Hope this helps!
- Sun Nov 29, 2020 10:21 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polar/Nonpolar Bonds/Molecules
- Replies: 2
- Views: 106
Re: Polar/Nonpolar Bonds/Molecules
Polar bonds are bonds in which the electrons are not shared evenly. Such as in C-H, C will pull the electron from H more strongly than H pulls the electron from C, so C will have a partial negative charge and H will have a partial positive charge. A nonpolar molecule can have polar bonds, because if...
- Sun Nov 29, 2020 11:38 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Seesaw and T-shapes
- Replies: 4
- Views: 762
Re: Seesaw and T-shapes
So for seesaw, you have 5 regions of electron density with 1 lone pair, and you have 5 regions of electron density with 2 lone pairs for T-shape. The angles between the equatorial bonded atoms facing you and facing away from you is less than 120 degrees, and the angle between one of the axial atoms ...
- Sun Nov 29, 2020 11:35 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Methane vs ammonia
- Replies: 5
- Views: 1205
Re: Methane vs ammonia
Because there are lone pairs, they repel the bonded atoms/electrons more strongly. In NH3, that lone pair will repel the H atoms more strongly and push them together, creating smaller bond angles between them. In CH4, the repulsion levels are the same between all bonded electrons, so the shape is te...
- Fri Nov 27, 2020 1:55 pm
- Forum: Hybridization
- Topic: 2sp^2 vs 3sp^2
- Replies: 6
- Views: 422
Re: 2sp^2 vs 3sp^2
Yea you got it! n is the energy level, and it can be 1, 2, 3, etc. Such as when we write 2p^2 for C, we write 3p^2 for Si. It shows the relative energy levels of the valence electrons, and it would be the same for the hybridized orbitals.
- Fri Nov 27, 2020 1:52 pm
- Forum: Significant Figures
- Topic: 40. versus 40
- Replies: 23
- Views: 1513
Re: 40. versus 40
Yes! When decimals are included, it means that you count everything before and after them. 40.0 would have 3 sig figs, and 40. would have two. 4.0 would also have 2.
- Fri Nov 27, 2020 1:50 pm
- Forum: Empirical & Molecular Formulas
- Topic: Periodic Table and Calculations
- Replies: 21
- Views: 1489
Re: Periodic Table and Calculations
I have the TI-89 and I really like it! But I also have the TI-84, and it's not my favorite but it gets the job done just as well! I just use a periodic table in a chemistry book. I'm not sure why the numbers you're using would be that off. Hope this helps!
- Sun Nov 22, 2020 8:26 pm
- Forum: Ionic & Covalent Bonds
- Topic: Rules of ionization energy
- Replies: 18
- Views: 1589
Re: Rules of ionization energy
The ionization energy increases going to the right because the atoms become more electronegative and want to hold onto their electrons more tightly. It decreases going down a group because the electrons in the outer shell are not held onto as tightly and can be removed more easily.
- Sat Nov 21, 2020 1:00 pm
- Forum: Dipole Moments
- Topic: Polarity
- Replies: 30
- Views: 1264
Re: Polarity
There can be polar bonds, but if they all cancel each other out, overall the molecule will be nonpolar. It's like if you are pulling a wagon one way and your friend is pulling it the other way. You're pulling different ways but you cancel each other out and the wagon doesn't move.
- Sat Nov 21, 2020 12:57 pm
- Forum: General Science Questions
- Topic: bond lengths
- Replies: 10
- Views: 912
Re: bond lengths
I don't think so, because that might just be a coincidence, but an interesting observation! I don't think that things fit that nicely in reality however.
- Sat Nov 21, 2020 12:50 pm
- Forum: Bond Lengths & Energies
- Topic: kJ/mol for bond energy in Lecture #18
- Replies: 3
- Views: 197
Re: kJ/mol for bond energy in Lecture #18
I believe it is the mole of H bonds being bonded. He said that if there were 20 kJ/mol of energy per something, and there 10 H bonds for that molecule, there would be 200 kJ/mol overall, so that implies that it's per mole of bonds. I could be completely wrong so please someone feel free to correct me!
- Sat Nov 21, 2020 12:46 pm
- Forum: Coordinate Covalent Bonds
- Topic: General Question on Coordinate Covalent Bonds
- Replies: 8
- Views: 588
Re: General Question on Coordinate Covalent Bonds
If both of the electrons that fulfilled the octet from the base come from the same element, it will be a coordinate covalent bond. Like in NH3 and BF3. Both electrons to fulfill the octet for B come from N, so it will be a coordinate covalent bond.
- Sat Nov 21, 2020 12:44 pm
- Forum: Coordinate Covalent Bonds
- Topic: What is a coordinate Covalent Bond
- Replies: 11
- Views: 740
Re: What is a coordinate Covalent Bond
A coordinate covalent bond is one formed between a Lewis acid and a Lewis base, but also the electrons that are from the base come from one atom, not any more.
- Sat Nov 21, 2020 12:42 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Configuration vs. Valence Electron Configuration
- Replies: 2
- Views: 2643
Re: Electron Configuration vs. Valence Electron Configuration
Hi! The valence electron shell are the electrons in the outermost shells. So in sulfur, for example, the core electrons are the electrons leading up to the nearest noble gas, in this case Neon, and the rest of the electrons are the valence. I also wanted to say that for transitional metals, you need...
- Sat Nov 14, 2020 11:01 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Valence electron numbers
- Replies: 6
- Views: 288
Re: Valence electron numbers
I think that the p orbital that you are talking about has to do more with quantum numbers rather than valence electrons? Correct me if I am mistaken. Yeah, I agree. I think this has to do more with the shape and the wave function, but I'm not positive Regarding the p orbitals, I mean they fill up w...
- Fri Nov 13, 2020 8:51 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Valence electron numbers
- Replies: 6
- Views: 288
Valence electron numbers
I think that valence electrons are every electron after the noble gas, but do we include d electrons? In the textbook problems, it sometimes does and sometimes doesn't include the d electrons as the valence. For example, how many valence would Sb +3 have? It's electron configuration is 4d105s2, so w...
- Fri Nov 13, 2020 1:15 pm
- Forum: Electronegativity
- Topic: Textbook 2D #5
- Replies: 4
- Views: 219
Re: Textbook 2D #5
HCl would have greater ionic character, since Cl is more electronegative. Because it is more electronegative, it pulls electrons in more closely to it, and the electrons are shared less equally (i.e. less covalently). Therefore, it would have an ionic character higher than that of HI. You can also t...
- Wed Nov 11, 2020 6:26 pm
- Forum: Dipole Moments
- Topic: Sapling #17
- Replies: 8
- Views: 4012
Re: Sapling #17
Typically, London forces are nonpolar because they don't have permanent dipoles, and nonpolar molecule interactions can only do so through dispersion forces. Look at whichever molecules are nonpolar and those should be the correct answers!
- Wed Nov 11, 2020 1:56 pm
- Forum: Dipole Moments
- Topic: Hydrogen Bonds
- Replies: 6
- Views: 294
Re: Hydrogen Bonds
You can argue that all bonds are just electrostatic forces of attraction. In bonding, there is no solid thing linking the two atoms. They're the same bonds, just intramolecular are stronger than intermolecular.
- Wed Nov 11, 2020 1:55 pm
- Forum: Bond Lengths & Energies
- Topic: Quadruple Bond
- Replies: 2
- Views: 106
Re: Quadruple Bond
Yes they exist when 8 electrons are involved in bonding, but are mostly found in the d block elements. I believe there are also quintuple bonds.
- Wed Nov 11, 2020 1:53 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic v. Covalent Bonding
- Replies: 16
- Views: 765
Re: Ionic v. Covalent Bonding
When atoms are far away from each other on the periodic table, they will most likely form an ionic bond, such as Ca and Cl. When they are closer, they will most likely form covalent. I do want to mention that no there is no true ionic or covalent bond. Each of these characters will have a little bit...
- Wed Nov 11, 2020 1:51 pm
- Forum: Lewis Structures
- Topic: Double Bonds
- Replies: 11
- Views: 270
Re: Double Bonds
Look to see which one would have the lowest formal charge, but also it would make sense for the higher ionization element/more electronegative element to get the partial negative charge if you couldn't form a double bond. Also you need to make sure that Cl wouldn't have a + charge, because Cl is ver...
- Wed Nov 11, 2020 1:49 pm
- Forum: Dipole Moments
- Topic: Negative Energy
- Replies: 4
- Views: 361
Re: Negative Energy
Yes! Energy is released when bonds are formed, and energy is required to break them. This is why ATP is important; it is not the breaking of bonds of ATP that releases the most energy, but the energy formed when ATP breaks and then recombined with other molecules to form bonds.