Search found 50 matches
- Sat Mar 14, 2020 8:40 pm
- Forum: Balancing Redox Reactions
- Topic: oh
- Replies: 11
- Views: 775
Re: oh
no you always use h20 to balance out the o's, then you use oh's later on, in basic solutions to balance the charge (not in acidic solutions though).
- Sat Mar 14, 2020 8:38 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Delta S
- Replies: 8
- Views: 682
Re: Delta S
Delta S total is equal to delta s or the surroundings plus delta s of the system. When the reaction is reversible then delta s total is equal to zero because the work done on the surroundings and on the system is equal
- Sat Mar 14, 2020 8:36 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Reaction order
- Replies: 4
- Views: 348
Re: Reaction order
It can be used on any reaction order because it has to do with changes in the rate constant rather than changes regarding the reaction order.
- Sat Mar 14, 2020 8:33 pm
- Forum: General Rate Laws
- Topic: How to use general rate laws to find rates of specific equations?
- Replies: 4
- Views: 520
Re: How to use general rate laws to find rates of specific equations?
Rate laws can be used in this question because for bimolecular reactions like the one in part a, the rate is simply equal to k[NO}^2, because there are two molecules of NO reacting and colliding with each other. This makes the coefficient for NO 2, and thus that becomes the exponent in the rate law ...
- Sat Mar 14, 2020 8:29 pm
- Forum: Zero Order Reactions
- Topic: Units
- Replies: 9
- Views: 755
Re: Units
I think the units for a zero order reaction are molarity per second (or M/second). In a zero order reaction, the reactant is just pretty much colliding with the walls of the space it is within, not with any other reactant.
- Thu Mar 05, 2020 7:41 am
- Forum: Van't Hoff Equation
- Topic: Van't Hoff equation
- Replies: 11
- Views: 1231
Re: Van't Hoff equation
Although this isn't on the equation sheet itself, you should know how to derive it. It basically draws a relationship between temperatures and K values that are changing/ different.
- Thu Mar 05, 2020 7:39 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Platinum in cell diagrams
- Replies: 5
- Views: 309
Re: Platinum in cell diagrams
Pt is a solid used to conduct the actual processes happening, so it should be added to the side of a cell in which there is only aq solutions, or aq and gas.
- Thu Mar 05, 2020 7:38 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: writing cell diagramsl
- Replies: 4
- Views: 282
Re: writing cell diagramsl
Leave H2O out of all cell diagrams, it should not be there
- Thu Mar 05, 2020 7:38 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst
- Replies: 10
- Views: 714
Re: Nernst
You usually use ln, just because it is more direct and it is also given to us on our equation sheets. If you want to use log however, just multiply by the conversion factor, it shouldn't really matter in the end
- Thu Mar 05, 2020 7:36 am
- Forum: Balancing Redox Reactions
- Topic: Simplifying
- Replies: 7
- Views: 577
Re: Simplifying
you can definitely simplify at the end, it won't change the potentials at all. Still, usually after balancing half reactions the final one will already be in its most simplified form
- Sat Feb 29, 2020 9:20 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt bridges
- Replies: 11
- Views: 734
Re: Salt bridges
In a battery, if ions were to flow freely to their corresponding sides, there would eventually be a buildup of charge. The cathode side would get extremely negative because of the electrons flowing to it, and the anode side would get very positive. The salt bridge neutralizes this and prevents it fr...
- Sat Feb 29, 2020 9:18 pm
- Forum: Balancing Redox Reactions
- Topic: Cell Diagrams
- Replies: 14
- Views: 932
Re: Cell Diagrams
A general rule of thumb my TA said was that the anode is usually on the left and the cathode is on the right.
- Sat Feb 29, 2020 9:14 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: E potentials
- Replies: 5
- Views: 424
Re: E potentials
I think that the only way we have been learning and the only way they do it in the textbook is in terms of reduction potentials, so that's probably what we should pay attention to
- Sat Feb 29, 2020 9:12 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell diagram order
- Replies: 4
- Views: 347
Re: Cell diagram order
I don't think the order matters at all. Sometimes, it is written in the order of reactants then products, but this isn't a rule and you shouldn't assume it will be that way in a question.
- Sat Feb 29, 2020 9:10 pm
- Forum: Balancing Redox Reactions
- Topic: When to add H+ or H20
- Replies: 19
- Views: 2366
Re: When to add H+ or H20
If you are talking about acidic solutions (which I assume you are since you asked about H+ ions), you can just add H20 first to balance out the number of oxygens in the reaction, and then add however many H+ ions you need to balance out the hydrogens as well.
- Thu Feb 20, 2020 11:25 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneous
- Replies: 23
- Views: 1130
Re: Spontaneous
When the change in Gibbs Free Energy value is negative, then we can know that the reaction is spontaneous and proceeding towards the products. If it is a positive change, then the reaction is not favorable or spontaneous and proceeds towards reactants.
- Thu Feb 20, 2020 11:23 am
- Forum: Lewis Acids & Bases
- Topic: Midterm Question 3B
- Replies: 3
- Views: 482
Re: Midterm Question 3B
So for this question, you have to look at what system will have the smallest volume and the greatest amount of substance that is concentrated in it. My TA explained it in the way that a smaller volume will allow for a greater concentration of substrate to interact, and a higher concentration will al...
- Thu Feb 20, 2020 11:21 am
- Forum: Balancing Redox Reactions
- Topic: Reduction vs. oxidation
- Replies: 29
- Views: 1109
Re: Reduction vs. oxidation
an oxidized species will have lost electrons (in other words, its oxidation number will increase), and a reduced one will have gained electrons (so the oxidation number decreases and becomes more negative from the negative charge of the electrons)
- Thu Feb 20, 2020 11:19 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Potential Difference
- Replies: 3
- Views: 227
Re: Cell Potential Difference
yes the values will be given or you can look them up I believe
- Thu Feb 20, 2020 11:17 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Midterm question 8 [ENDORSED]
- Replies: 5
- Views: 505
Re: Midterm question 8 [ENDORSED]
In an irreversible reaction, the total change in entropy will be equal to the change in entropy of the system. In a reversible expansion, the total will be equal to zero, which can also be interpretted as the entropy change of the system is equal to the entropy change of the system but in negative f...
- Sun Feb 16, 2020 5:56 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: spontaneity
- Replies: 39
- Views: 1817
Re: spontaneity
If delta g, gibbs free energy, is a negative value, then the reaction in question can be determined to be spontaneous
- Sun Feb 16, 2020 5:56 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible vs Irreversible
- Replies: 13
- Views: 832
Re: Reversible vs Irreversible
Irreversible usually means there is a sudden change that happens very quickly, and the surroundings/ system entropies are not equal. Reversible means that there are a series of little partial changes during which the entropy change of the system is equal to the negative entropy change of the surroun...
- Sun Feb 16, 2020 5:54 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Equilibrium
- Replies: 15
- Views: 778
Re: Equilibrium
At equilibrium, we know that both the forward and reverse reactions are occurring at roughly the same rate, and with roughly the same favorability. This means that neither one is specifically favored or spontaneous, so delta g is 0
- Sun Feb 16, 2020 5:52 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: Boltzmann Equation
- Replies: 10
- Views: 561
Re: Boltzmann Equation
This equation is a way of calculating the entropy of a system of molecules entirely based on their position and the number of ways they can be arranged
- Sun Feb 16, 2020 5:51 pm
- Forum: Calculating Work of Expansion
- Topic: work = 0
- Replies: 14
- Views: 1282
Re: work = 0
when looking at work in an irreversible expansion, it is equal to external pressure times change in volume. In a vacuum, there is no external pressure so there is no work done
- Sun Feb 09, 2020 11:50 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Delta in enthalpy and not entropy
- Replies: 6
- Views: 160
Re: Delta in enthalpy and not entropy
The delta sign just smbolizes that there is a change in that specific value. Both entropy and enthalpy are state functions, and both of them can have calculated changes in their values.
- Sun Feb 09, 2020 11:49 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Heat capacity
- Replies: 6
- Views: 247
Re: Heat capacity
Yes, because both types of molecules have different amount of orientations and states
- Sun Feb 09, 2020 11:49 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: U=3/2 nRT
- Replies: 4
- Views: 181
Re: U=3/2 nRT
I dont think we covered this in class so I am unsure if it is necessary for the exam, especially since we focused more on changes in internal energy, rather than fixed amounts...
- Sun Feb 09, 2020 11:47 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Constant T,P,V
- Replies: 4
- Views: 163
Re: Constant T,P,V
the question will often let you know whether the pressure, volume, or temperature is going to be held constant. Sometimes, too, the question will say that the reaction is isobaric or isochoric, which tells you which value is being held constant in the system.
- Sun Feb 09, 2020 11:44 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: degeneracy
- Replies: 17
- Views: 576
Re: degeneracy
degeneracy can be thought of as having more than one state for a molecule or system. it has to do with entropy and disorder.
- Wed Jan 29, 2020 12:37 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature
- Replies: 6
- Views: 363
Re: Temperature
In an exothermic reaction, heat is exuded once the reaction runs. It is emitted from the reaction proceeding, so you can almost consider it a product of the reaction itself. Thus, if we want to maintain equilibrium in a system, adding more of this product (adding heat/ increasing the temperature) wi...
- Wed Jan 29, 2020 12:35 pm
- Forum: Ideal Gases
- Topic: non ideal gases
- Replies: 8
- Views: 430
Re: non ideal gases
Pretty much all gases are not ideal. an "ideal gas" is just a concept to help us be able to solve problems and equations assuming that the gas does not take up any volume or have any intermolecular forces (which non-ideal gases obviously do).
- Wed Jan 29, 2020 12:33 pm
- Forum: Ideal Gases
- Topic: Inert Gas
- Replies: 12
- Views: 660
Re: Inert Gas
inert and noble gases are the same thing. They are in the very last column of the periodic table and are not reactive and very stable.
- Wed Jan 29, 2020 12:32 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: acidic and basic salts
- Replies: 3
- Views: 231
Re: acidic and basic salts
Salts usually only affect pH if they are weak rather than strong. Strong acids and bases can disassociate totally, and they wont affect the pH, while a weak one will only disassociate partially, meaning that the concentration of H30+ or OH- molecules will increase or decrease depending on the compou...
- Wed Jan 29, 2020 12:29 pm
- Forum: Ideal Gases
- Topic: Temperature
- Replies: 17
- Views: 723
Re: Temperature
most equations in chemistry tend to use Kelvin instead of Celcius or Farenheit. This is important for these calculations because without conversion, the answers to some questions may come out incorrectly. Usually, if the question does not want you to use Kelvin, it will let you know.
- Fri Jan 24, 2020 6:34 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Calculating Delta H
- Replies: 3
- Views: 59
Re: Calculating Delta H
Today we only covered three methods, but I imagine we will get to the fourth in the next lecture.
- Fri Jan 24, 2020 6:33 pm
- Forum: Phase Changes & Related Calculations
- Topic: Steam vs. Boiling Water
- Replies: 10
- Views: 445
Re: Steam vs. Boiling Water
Steam at 100 degrees celcius is clearly extremely hot, and when it touches skin, there is a huge difference in temperatures. The steam then undergoes a phase change extremely rapidly, going from a gas form to a liquid water form. This releases a lot of energy and thus ends up creating a much more in...
- Fri Jan 24, 2020 6:31 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q<K
- Replies: 11
- Views: 223
Re: Q<K
The forward reaction is favored because of the fact that changing the amount of reactants by increasing it will allow for more reactions to take place, ultimately increasing the amount of products and favoring this forward reaction.
- Fri Jan 24, 2020 6:30 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpy Accuracy
- Replies: 6
- Views: 101
Re: Bond Enthalpy Accuracy
The enthalpy of bonds is calculated by taking the averages of many different molecules, so you cant get a perfectly accurate and specific value for this. For diatomic molecules, however, it is accurate.
- Fri Jan 24, 2020 6:29 pm
- Forum: Phase Changes & Related Calculations
- Topic: Delta G vs. Delta H
- Replies: 3
- Views: 104
Re: Delta G vs. Delta H
Delta G refers to Gibbs free energy, the amount of energy available to do work in a system. Delta H, however, refers to enthalpy, or internal energy plus pressure and volume.
- Sun Jan 19, 2020 7:14 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Molar concentration of acids & bases
- Replies: 8
- Views: 359
Re: Molar concentration of acids & bases
If you are asked for the molar concentration, answer in mols/L, rather than pH or pOH. If you are asked for either of those, though, then you would need to take the negative log of the molar concentration and answer in that way.
- Sun Jan 19, 2020 7:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ice boc
- Replies: 7
- Views: 208
Re: ice boc
the ice box should pretty much always be used because it can help get rid of mistakes and organize our thoughts. x is only negligible when the k value is ver, very small. it has to be less than 1x10^-3 in order to just ignore x, otherwise you can't simply get rid of it.
- Sun Jan 19, 2020 7:06 pm
- Forum: Ideal Gases
- Topic: inert gas
- Replies: 5
- Views: 236
Re: inert gas
An inert gas is one that will not react or really have any effect on an ongoing reaction. For Le Chatlier's principle, adding an inert gas won't change the reaction. These are really stable, non-reactive gases: the noble gases in other words.
- Sun Jan 19, 2020 7:04 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Strong Acids/Bases vs. Weak Acids/Bases
- Replies: 9
- Views: 218
Re: Strong Acids/Bases vs. Weak Acids/Bases
From Chemistry 14A, we were advised to simply memorize the list of strong acids and bases. There is a comprehensive list in the textbook. Contextually speaking, though, strong acids and bases are basically the ones that dissociate completely in reactions, while weak ones are the ones that only parti...
- Mon Jan 13, 2020 6:01 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Thermodynamic Stability
- Replies: 6
- Views: 314
Re: Thermodynamic Stability
Cl2 is more thermodynamically stable than F2 because of its smaller K vale, or equilibrium constant. This also means that it is going to dissociate less totally than F2 into singular atoms, which in turn makes it more stable (since it wants to stay in its original state of a diatomic molecule).
- Sat Jan 11, 2020 5:13 pm
- Forum: Ideal Gases
- Topic: Solids and liquids [ENDORSED]
- Replies: 6
- Views: 263
Re: Solids and liquids [ENDORSED]
The activity of pure substances is equal to 1, which means that in a reaction their concentration will not ever change. Because of this, liquids are not included in the calculations.
- Sat Jan 11, 2020 5:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE box
- Replies: 9
- Views: 280
Re: ICE box
There can never be negative concentration values, so the only answers you would want to use for your answers are the ones that come out positive after solving the quadratic formula.
- Sat Jan 11, 2020 5:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Partial Pressure
- Replies: 7
- Views: 305
Re: Partial Pressure
Yes, partial pressure is only used for gases. Basically, a sum of all the partial pressures of different gases or compounds is equal to the total pressure of the system.
- Fri Jan 10, 2020 3:55 pm
- Forum: Ideal Gases
- Topic: R in PV=nRT
- Replies: 34
- Views: 5842
Re: R in PV=nRT
R is the Universal Gas Constant. It is described in the textbook as well. The values can be in different units of pressure. It is 8.314 J/molK, 0.082L-atm/ molK, or 62.36L-torr/molK.
- Fri Jan 10, 2020 3:50 pm
- Forum: Student Social/Study Group
- Topic: Test 1 14B Topics
- Replies: 4
- Views: 222
Re: Test 1 14B Topics
Definitely outline 1 and maybe a little of outline 2