## Search found 52 matches

Sat Mar 14, 2020 11:58 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 5
Views: 42

### Catalysts

How can you determine the catalyst by looking at the reaction? For example in 7E.5, how do you know the catalyst in this reaction?
Sat Mar 14, 2020 11:57 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation energy
Replies: 3
Views: 44

### Re: Activation energy

I don't think you can tell by just the activation energy. In a endergonic reaction, the products are higher than the reactants. If it is a slow endergonic reaction the activation energy is going to be much larger. In a faster endergonic reaction, the activation energy will be much lower. The same th...
Fri Mar 13, 2020 7:34 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Homework 7E1
Replies: 4
Views: 46

### Re: Homework 7E1

A catalyst doesn't affect deltaH! Remember to not mix thermodynamics with kinetics. All catalysts do is lower the activation energy of the reaction which therefore increases the rate of the reaction, but not the enthalpy of the reaction!
Fri Mar 13, 2020 7:32 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7th Edition Problem 7D.5
Replies: 3
Views: 117

### Re: 7th Edition Problem 7D.5

I don't understand why they subtracted 0.59, but I solved the problem without 0.59 being subtracted and got 2.7x10^10 which is what the solution manual got as well.
Fri Mar 13, 2020 6:15 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Dr. Lavelle's week 10 review - last question
Replies: 3
Views: 89

### Dr. Lavelle's week 10 review - last question

I am confused on what we are suppose to solve for this question. How do you determine if the student's mechanism is valid? I looked at Dr. Lavelle's work but I was still confused on this concept.
Fri Mar 13, 2020 6:10 am
Forum: First Order Reactions
Topic: HW 7B.3 Part C
Replies: 1
Views: 37

### Re: HW 7B.3 Part C

Since you have the initial concentration of A, [A]o, and you are given the number of moles for each reactant and product, you can solve to find [A]t which you can then plug into the equation ln[A]t=-kt+ln[A]o to solve for k. To find [A]t you would subtract the mole ratio of A to B times the concentr...
Mon Mar 09, 2020 9:03 pm
Forum: Second Order Reactions
Topic: 7B.13
Replies: 5
Views: 138

### Re: 7B.13

Wait, how do you solve for k if you don't have [A]t?
Sun Mar 08, 2020 5:40 pm
Forum: General Rate Laws
Topic: rate consumption
Replies: 1
Views: 39

### rate consumption

How do you solve for the rate of consumption?
Sun Mar 08, 2020 5:28 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation
Replies: 4
Views: 72

### Arrhenius Equation

What is the importance of the Arrhenius equation? What are you trying to find using this equation?
Sun Mar 08, 2020 5:19 pm
Forum: First Order Reactions
Topic: Determining order
Replies: 3
Views: 53

### Re: Determining order

I am not sure whether you use integrated or differential rate laws, but to determine order you can either look at the units given for k(r) or the exponent's in the equation. Usually, the units for
zero order: mol/(L x s)
1st order: 1/s
2nd order: L/(mol x s)
Sun Mar 08, 2020 5:16 pm
Forum: First Order Reactions
Topic: 1st order equation
Replies: 2
Views: 23

### 1st order equation

Hi! I am a little confused, when we are solving for first order problems, will we actually ever use the equation ln[A]=-kt+ln[A] or do you just use rate=k[A]?
Thu Mar 05, 2020 6:32 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Temperature
Replies: 2
Views: 55

### Temperature

How does change in temperature affect K or Q?
Tue Mar 03, 2020 4:57 pm
Forum: Balancing Redox Reactions
Replies: 4
Views: 54

Hi! For some problems such as 6K.5, when I am adding the electrons to balance the charge, I am sometimes getting the wrong number of electrons. I know how to find the initial and final oxidation numbers, but why isn't the charge you add to the reactants or products always equal to the change in oxid...
Tue Mar 03, 2020 10:20 am
Forum: Balancing Redox Reactions
Topic: MnO4-
Replies: 5
Views: 77

### MnO4-

Why is the charge of MnO4- +7?
Mon Mar 02, 2020 9:43 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: factors that affect k
Replies: 8
Views: 215

### Re: factors that affect k

K can be affected by cell potential. Cell potential depends on factors such as concentration, gas pressure, and temperature so all of these factors also affect K.
Mon Mar 02, 2020 9:09 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: observing initial rates
Replies: 3
Views: 56

### Re: observing initial rates

t=0 usually is the start for most reactions so when you are wanting to observe initial rates you want to observe rates that are closest to zero. It can be initial rates right after time t=0 so it is easiest to measure.
Mon Mar 02, 2020 5:43 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Week 8 - Wednesday Lecture
Replies: 2
Views: 47

### Week 8 - Wednesday Lecture

Hello! I was absent on Wednesday of week 8, I have the notes but I don't really understand what the notes mean. Can someone briefly explain the concept of Kinetics and the most important takeaway from that lecture? Thanks!
Sun Feb 23, 2020 6:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.1 A
Replies: 2
Views: 54

### 6L.1 A

Why do you use 2 for n in the equation DeltaG=-nFE in 6L.1 a?
Sun Feb 23, 2020 4:50 pm
Forum: Balancing Redox Reactions
Topic: 6K.1
Replies: 6
Views: 89

### 6K.1

Hi! I'm really confused with 6K.1. I'm having a hard time identifying the elements undergoing oxidation and reduction, and writing and balancing the reactions. Can anyone help explain?
Mon Feb 17, 2020 9:47 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5G.17
Replies: 2
Views: 67

### 5G.17

Can someone explain what the reaction, I (reactant) and I2 (product), will look like graphically?
Sun Feb 16, 2020 3:58 pm
Forum: Balancing Redox Reactions
Topic: Electrochemisty
Replies: 10
Views: 122

### Electrochemisty

Hi! I was absent Friday. Can someone explain what electrochemistry means and the importance of electrochemistry? Thanks!
Sun Feb 16, 2020 3:51 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Pressure
Replies: 3
Views: 39

### Re: Pressure

Yes, if you increase the partial pressure of a product gas, ΔG becomes more positive. If you increase the partial pressure of a reactant gas, ΔG becomes more negative because of the equation ΔG=ΔGo+RTlnQ where Q equals partial pressure of products over the partial pressure of reactants.
Sun Feb 16, 2020 3:48 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free energy
Replies: 2
Views: 32

### Re: Free energy

If the reaction is at equilibrium, Q=K and ΔG=-RTlnK. If you increase the partial pressure of a product gas, ΔG becomes more positive. If you increase the partial pressure of a reactant gas, ΔG becomes more negative. Therefore, ΔG depends on pressure and K.
Mon Feb 10, 2020 8:03 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: 4G.5
Replies: 4
Views: 44

### Re: 4G.5

According to the textbook, the cis compound has 12 different orientations while the trans compound only has three different orientations, decreasing the entropy due to the fact that there is less uncertainty in its orientations. In regards to entropy, residual entropy is the measure of how many dif...
Sun Feb 09, 2020 9:02 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv vs. Cp
Replies: 2
Views: 43

### Re: Cv vs. Cp

Like what Maia said above, in the review session today they said that they have almost never used Cp and only Cv. But when you are calculating, you can also check to see if the compound is a monatomic or diatomic compound. If it's monatomic then use 3/2, but if it's diatomic use 5/2.
Sun Feb 09, 2020 8:49 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Cs for monoatomic and diatomic
Replies: 4
Views: 45

### Re: Cs for monoatomic and diatomic

Monatomic compounds are composed of single atoms, and diatomic compounds are composed of molecules containing two atoms. what-are-the-seven-diatomic-elements-606623-v3-5b562dab46e0fb0037fee8c7.png Difference-Between-Monatomic-and-Diatomic-Comparison-Summary.png I don't know why the C s values are 3...
Sun Feb 09, 2020 8:45 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: expansion work
Replies: 4
Views: 59

### Re: expansion work

nshahwan 1L wrote:Would we ever have to calculate/know the amount of that force? Thanks!!

I don't think we have to worry about solving for force as we haven't been given any equations that include force
Sun Feb 09, 2020 8:41 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: internal energy and work
Replies: 4
Views: 47

### Re: internal energy and work

Internal energy equals the sum of heat and work. If internal energy is equal to zero than heat is equal to the opposite of what work is equal to.
Mon Feb 03, 2020 7:29 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4A.7
Replies: 2
Views: 41

### 4A.7

(a) Calculate the heat that must be supplied to a copper kettle of mass 400.0 g containing 300.0 g of water to raise its temperature from 20.0°C to the boiling point of water, 100.0°C. (b) What percentage of the heat is used to raise the temperature of the water? Can someone explain the concept of t...
Sun Feb 02, 2020 6:39 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Constant Volume and Pressure
Replies: 7
Views: 47

### Constant Volume and Pressure

What does it mean to have a constant volume or constant pressure?
Sun Feb 02, 2020 6:31 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Positive or negative work?
Replies: 8
Views: 84

### Re: Positive or negative work?

If energy is going into the system that means something else is doing work on the system and the work on the system is positive. If energy is going out of the system, that means that the system is doing work on the surrounding environment and energy is being lost from the system and is negative.
Sun Feb 02, 2020 6:26 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: higher entropies
Replies: 6
Views: 392

### Re: higher entropies

To go off of the idea that higher entropy means higher disorder, that means that gas has high entropy because it has many microstate while solids have the lowest entropy because it has the fewest microstates.
Sun Feb 02, 2020 6:21 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: extensive property
Replies: 12
Views: 153

### extensive property

Can someone explain the concept of extensive property? What are some examples of extensive property?
Sun Feb 02, 2020 6:13 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: residual entropy
Replies: 4
Views: 36

### Re: residual entropy

The residual entropy of a system is the difference between the calculated and experimental entropy at a given temperature
Sun Feb 02, 2020 4:27 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 4 Friday Lecture
Replies: 4
Views: 51

### Re: Week 4 Friday Lecture

Patricia Cardenas wrote:
Delaney Smith 1C wrote:Hi guys! I wasn't able to make this past Friday's lecture (week 4). Could anyone share their notes with me? Thank you so much!

I can share my notes with you too, what's your email?

dmsmith14@g.ucla.edu

Thank you!
Sun Feb 02, 2020 4:25 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 4 Friday Lecture
Replies: 4
Views: 51

### Re: Week 4 Friday Lecture

Deena Doan 2F wrote:Yeah, I can! What's your email?

dmsmith14@g.ucla.edu

Thank you so much!
Sun Feb 02, 2020 1:17 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 4 Friday Lecture
Replies: 4
Views: 51

### Week 4 Friday Lecture

Hi guys! I wasn't able to make this past Friday's lecture (week 4). Could anyone share their notes with me? Thank you so much!
Sun Jan 26, 2020 3:18 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: standard state
Replies: 2
Views: 26

### standard state

For method 3, how do you make sure everything is in standard state? Do you just divide by the number of moles for each substance so you have one mole?
Sun Jan 26, 2020 3:14 pm
Forum: Phase Changes & Related Calculations
Topic: DeltaHsub
Replies: 2
Views: 23

### DeltaHsub

Can someone explain why DeltaHsub = DeltaHfus + DeltaHvap?
Sun Jan 26, 2020 3:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: different methods
Replies: 3
Views: 38

### Re: different methods

It will most likely depend on the information given. You use: Hess's law (method 1) : If you have two equations that can be added together to get the wanted composite equation, you can add the deltaHRXN of each equation to get the net deltahHRXN Method 2: if you are given the bond enthalpies and can...
Sun Jan 26, 2020 2:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method 3 - Enthalpy
Replies: 2
Views: 19

### Re: Method 3 - Enthalpy

The third method is referred to as the standard enthalpy of formation. The standard enthalpy of formation is the change in enthalpy of the products and reactants with each substance being in standard state (one mole).
Sun Jan 26, 2020 2:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Lewis Structures
Replies: 4
Views: 52

### Lewis Structures

Can anyone briefly explain how to go about drawing lewis structures? I know it's useful to draw out for method 2, but I forgot. Thanks!
Sun Jan 19, 2020 4:53 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pH vs. pOH
Replies: 13
Views: 149

### pH vs. pOH

What do you do again when you are calculating pOH? Also, how do you know if you are calculating for a base or for an acid?
Sun Jan 19, 2020 4:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6A.23
Replies: 1
Views: 19

### 6A.23

In 6A.23, how do you know how to write the reaction? I'm confused on how to know if OH- or H3O is in the reaction and if so which side it is on?
Sun Jan 19, 2020 4:30 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Conjugate Seesaw
Replies: 5
Views: 42

### Re: Conjugate Seesaw

Acids produce conjugate bases when they dissociate in aqueous solutions. On the other hand, bases produce conjugate acids when they dissociate in aqueous solutions. The conjugate seesaw basically just means that stronger acids produce weaker bases and stronger bases will produce weaker acids.
Sun Jan 19, 2020 4:24 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Strong Acids/Bases vs. Weak Acids/Bases
Replies: 9
Views: 63

### Strong Acids/Bases vs. Weak Acids/Bases

How do you know in a problem whether the acid/base is strong or weak? Do you memorize them or is there an easier way to tell?
Sun Jan 19, 2020 4:18 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 4
Views: 34

### Re: Le Chatelier's Principle

For partial pressure, the composition will tend to change in a way that minimizes the resulting increase in pressure. The basic point is that the reaction will shift to whichever side that has less moles.
Sun Jan 12, 2020 5:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solvents
Replies: 1
Views: 16

### Solvents

Why are changes in solvent concentrations insignificant in a reaction?
Sun Jan 12, 2020 4:40 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction shifts right or left?
Replies: 14
Views: 224

### Re: Reaction shifts right or left?

Yes, if the reaction is shifted to the left that means that the are more moles on the left side of the reaction which are the reactants. While if the reaction is shifted to the right that means there are more moles on the right side of the reaction which are the products.
Sun Jan 12, 2020 4:33 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Situations in which Q=K
Replies: 7
Views: 71

### Re: Situations in which Q=K

The reaction is still present and occurring even when the products are equal to the reactants. This just means that P/R ratio is the same so there won't be more products or reactants as the reaction is at equilibrium.
Sun Jan 12, 2020 4:19 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Equilibrium vs. Non-Equilibrium
Replies: 4
Views: 33

### Equilibrium vs. Non-Equilibrium

How do you know if a reaction is at equilibrium or not at equilibrium? Will the question state specifically to solve for K or Q or do you have to know just by looking at the reaction whether you're solving a reaction at equilibrium or not at equilibrium?
Sun Jan 12, 2020 4:15 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE vs Normal Concentrations
Replies: 5
Views: 37

### Re: ICE vs Normal Concentrations

ICE is good to use when you are solving for the composition of reactants or products in a reaction. Otherwise you would be solving for K if the reaction is at equilibrium or Q if the reaction is not at equilibrium.