## Search found 50 matches

Sat Mar 14, 2020 8:40 pm
Forum: Balancing Redox Reactions
Topic: oh
Replies: 11
Views: 250

### 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: 156

### 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: 93

### 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: 117

### 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: 135

### 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: 10
Views: 266

### 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: 58

### 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: 45

### 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: 181

### 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: 141

### 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: 128

### 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: 162

### 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: 72

### 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: 75

### 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: 343

### 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: 422

### 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: 236

### 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: 335

### 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: 34

### 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: 198

### 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: 34
Views: 690

### 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: 286

### 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: 176

### 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: 149

### 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: 276

### 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: 70

### 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: 70

### 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: 47

### 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: 56

### 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: 7
Views: 55

### 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: 113

### 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: 97

### 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: 223

### 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: 2
Views: 99

### 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: 167

### 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: 29

### 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: 136

### 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: 91

### 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: 38

### 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: 41

### 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: 140

### 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: 67

### 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: 37

### 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: 64

### 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: 69

### 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: 76

### 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: 89

### 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: 74

### 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: 764

### 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: 79

### Re: Test 1 14B Topics

Definitely outline 1 and maybe a little of outline 2