## Search found 50 matches

Sun Mar 15, 2020 4:42 pm
Forum: Experimental Details
Topic: Psuedo First Order
Replies: 4
Views: 652

### Re: Psuedo First Order

Is the rate always going to depend on the reactant with smallest concentration? A pseudo rate is considered when there are too many changing concentrations. For instance, it is difficult to calculate the rate when you have k[A][B], and both A and B are changing. As such, you make one significantly l...
Sun Mar 15, 2020 4:37 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow and Fast Step
Replies: 7
Views: 99

### Re: Slow and Fast Step

Yes, since the slow step determines the rate of the overall reaction, it means that the order of the slow step is the same as the order of the reaction.
Sun Mar 15, 2020 4:31 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Slowest step
Replies: 9
Views: 128

### Re: Slowest step

Because the slowest step needs to be done for the reaction to be able to be completed.
Sun Mar 15, 2020 4:17 pm
Forum: Zero Order Reactions
Topic: Orders
Replies: 8
Views: 96

### Re: Orders

As far as I know, we never include products in the rate law, correct? A first-order reaction means that there is one reactant or molecule present in the rate law. A second-order rate law either has two of the same reactant (rate law would be squared) or two different ones (they would be multiplied b...
Sun Mar 15, 2020 4:16 pm
Forum: Zero Order Reactions
Topic: Orders
Replies: 8
Views: 96

### Re: Orders

How would we know the order of the reaction if we are given an integrated rate law?

asannajust_1J wrote:the total order of the reaction is the sum of the exponential coefficients. This can be determined based on graphs, a given rate law, or an integrated rate law.
Sun Mar 08, 2020 9:43 pm
Forum: Zero Order Reactions
Topic: Concentration of Reactants in a Zero-Order Reaction
Replies: 2
Views: 30

### Concentration of Reactants in a Zero-Order Reaction

Why does increasing the concentration of reactants in a zero-order reaction not affect the reaction rate?
Sun Mar 08, 2020 9:10 pm
Forum: General Rate Laws
Topic: Product in Rate Law
Replies: 2
Views: 53

### Re: Product in Rate Law

I think you only use the concentration of the reactants when calculating the rate (this is for differential rate laws).
Sun Mar 08, 2020 8:48 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Intermediate Species
Replies: 9
Views: 83

### Intermediate Species

Could anyone please explain what exactly is an intermediate species?
Sun Mar 08, 2020 8:41 pm
Forum: Van't Hoff Equation
Topic: what does it do?
Replies: 13
Views: 253

### Re: what does it do?

Thank you! I see how it is related and it's definitely useful. Could you elaborate a little more on how it's an indirect way to measure enthalpy, please? When using the Van't Hoff equation, we assume that the difference in enthalpy is considered to be the same, and we assume that the difference in e...
Sun Mar 08, 2020 8:36 pm
Forum: General Rate Laws
Topic: Pseudo-Rate Law
Replies: 2
Views: 25

### Re: Pseudo-Rate Law

If the concentration of one reactant is small and the concentration of the other reactant(s) is large, the reaction rate will depend on the reactant with small concentration, so the reaction is easier to study.
Sun Mar 01, 2020 10:43 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Replies: 8
Views: 67

When do you add platinum to the cell diagram of a redox reaction, and on which side does it go?
Sun Mar 01, 2020 10:37 pm
Forum: Balancing Redox Reactions
Topic: Acidic vs. Basic Solutions
Replies: 8
Views: 120

### Acidic vs. Basic Solutions

What is the difference between a redox reaction in acidic solution and one in a basic solution?
Sun Mar 01, 2020 10:32 pm
Forum: Balancing Redox Reactions
Topic: Anode and Cathode
Replies: 9
Views: 94

### Re: Anode and Cathode

The anode loses electrons (undergoes oxidation) and the cathode gains electrons (undergoes reduction).
Sun Mar 01, 2020 10:28 pm
Forum: Balancing Redox Reactions
Topic: Oxidizing/reducing agent
Replies: 18
Views: 223

### Re: Oxidizing/reducing agent

Why is the oxidizing agent being reduced and not oxidized?

Charysa Santos 4G wrote:An oxidizing agent refers to the item being reduced, which allows for the other species to be oxidized. A reducing agent is exactly the opposite: it is being oxidized in order for another species to be reduced.
Sun Mar 01, 2020 10:25 pm
Forum: Balancing Redox Reactions
Topic: Test 2
Replies: 19
Views: 200

### Re: Test 2

It will be until the end of electrochemistry; thus, kinetics should not be included.

WYacob_2C wrote:
CynthiaLy4F wrote:I believe it will only cover topics from the midterm up until the end of kinetics.

Would it be up until the end of kinetics or the end of electrochemistry?
Sun Feb 23, 2020 6:25 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: how to get n in equation
Replies: 8
Views: 82

### Re: how to get n in equation

Is it in number of moles?

Bryce Barbee wrote:N is found by finding how many electrons are being transferred in the process.
Sun Feb 23, 2020 6:01 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: neg vs pos
Replies: 9
Views: 58

### Re: neg vs pos

For the first part of your answer, this means that the reaction will not occur spontaneously in the forward reaction, right? A negative cell voltage -- reaction will occur spontaneously but in the opposite direction as compared to the forward. A positive cell voltage--reaction will occur spontaneous...
Sun Feb 23, 2020 5:59 pm
Forum: Balancing Redox Reactions
Topic: Flow of electrons
Replies: 11
Views: 91

### Flow of electrons

Is the flow of electrons always going to be form anode to cathode or are there circumstances where it's the other way around?
Sun Feb 23, 2020 5:56 pm
Forum: Van't Hoff Equation
Topic: what does it do?
Replies: 13
Views: 253

### Re: what does it do?

Could you elaborate a little more on how it's an indirect way to measure enthalpy, please? When using the Van't Hoff equation, we assume that the difference in enthalpy is considered to be the same, and we assume that the difference in entropy between reactants and products is also the same at these...
Sun Feb 23, 2020 5:45 pm
Forum: Van't Hoff Equation
Topic: Notes from 02/14/2020
Replies: 1
Views: 37

### Notes from 02/14/2020

Could anyone please send me a copy of their notes from 02/14/2020, I would really appreciate it. My email is noebamen02@g.ucla.edu. Thanks in advance!
Sun Feb 16, 2020 8:26 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous
Replies: 13
Views: 125

### Re: Spontaneous

When delta G is negative, it's spontaneous. When delta G is positive.
Sun Feb 16, 2020 8:17 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: memorize
Replies: 14
Views: 215

### Re: memorize

I think such numbers like that one will always be given to us.
Sun Feb 16, 2020 8:10 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Why are exothermic reactions generally spontaneous?
Replies: 16
Views: 227

### Re: Why are exothermic reactions generally spontaneous?

Yes, a spontaneous reaction has a negative delta G.

LBacker_2E wrote:Is this related to the relationship between ∆G and the direction of a spontaneous reaction? Does a spontaneous reaction have a -∆G and proceed in the forward direction?
Sun Feb 16, 2020 8:07 pm
Forum: Van't Hoff Equation
Topic: delta s
Replies: 9
Views: 87

### Re: delta s

It won't change unless standard conditions are changed
Sun Feb 16, 2020 7:57 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 4f.1
Replies: 2
Views: 36

### Re: 4f.1

Under which conditions would you use delta S = nRln(V2/V1) and delta S = qrev/T?
Sun Feb 09, 2020 3:19 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous Reaction
Replies: 8
Views: 56

### Re: Spontaneous Reaction

Can someone please explain how a negative delta G makes a reaction favorable?

005324438 wrote:Yes exactly, when ΔG is negative the reaction is favorable, and when it is positive it is unfavorable.
Sun Feb 09, 2020 2:51 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: solids and liquids in the rxn quotient
Replies: 8
Views: 110

### Re: solids and liquids in the rxn quotient

Yes, you exclude solids and liquids. You only take into account gases and aqueous solutions when calculating Q and/or K.
Sun Feb 09, 2020 2:28 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: internal energy
Replies: 3
Views: 37

### Re: internal energy

This is because there's no expansion since pressure and volume are constant, right?

Elena Bell 1C wrote:If a system is a constant pressure and volume then w would equal zero. Since, deltaU=q+w and q=deltaH I think it would just be deltaU=deltaH if both pressure and volume is constant.
Sun Feb 09, 2020 2:22 pm
Forum: Calculating Work of Expansion
Topic: Irreversible Expansion Explained
Replies: 7
Views: 96

### Re: Irreversible Expansion Explained

I was about to ask the same question since homework problems specify whether it's reversible or irreversible, so I didn't know if we have to know based on the given information. This is kind of irrelevant to the question but will the question always say if it is reversible or irreversible? Or is the...
Sun Feb 02, 2020 6:53 pm
Forum: Calculating Work of Expansion
Topic: work integral
Replies: 6
Views: 59

### Re: work integral

Are there any homework problems where we have to use the integral instead of the simplified formula? We use -p(delta)v when the pressure is constant, because it allows us to factor out the variable P from the integral to end up with just integrating the constant "1", which simplifies the i...
Sun Feb 02, 2020 6:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: accuracy of bond enthalpies
Replies: 8
Views: 85

### Re: accuracy of bond enthalpies

Because it uses the average of many molecules.
Sun Feb 02, 2020 3:50 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter + Heat Transfer
Replies: 4
Views: 22

### Re: Calorimeter + Heat Transfer

It might also be helpful to think that the heat of a system plus the heat of its surroundings has to be equal to 0. So, if you have an exothermic reaction that released -X amount of heat, the surroundings gained +X amount of heat in order for the addition of both to be 0.
Sun Feb 02, 2020 3:39 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible/Irreversible Reactions
Replies: 6
Views: 59

### Re: Reversible/Irreversible Reactions

Does anyone know if we need to know the integral equation for reversible reaction or just the simplified version? Honestly that is the biggest difference, and because of the difference there are two different equations that can be used. For irreversible reactions, use the equation w=-P(change in V) ...
Sun Feb 02, 2020 3:32 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Elements
Replies: 8
Views: 42

### Re: Elements

Does this means that if I have H2 and want to form H2O, then there would be an enthalpy of formation? Diatomic molecules such as H2, O2, N2, F2, I2, CL2, and Br2 all have an enthalpy of formation of 0 because it is their naturally occuring state. There is no enthalpy of formation for the way somethi...
Sun Jan 26, 2020 9:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 4
Views: 33

### Re: Hess's Law

I think it's just the first one, which is also the best method to use.
Sun Jan 26, 2020 9:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Exothermic and Endothermic
Replies: 11
Views: 420

### Re: Exothermic and Endothermic

An exothermic reaction has a negative H value because it releases energy when bonds are being formed. An endothermic reaction has a positive H value because it needs energy in order to break bonds.
Sun Jan 26, 2020 8:59 pm
Forum: Phase Changes & Related Calculations
Topic: Physical or Phase Changes
Replies: 7
Views: 64

### Re: Physical or Phase Changes

They should be given to us since we didn't go over how to calculate it.
Sat Jan 25, 2020 10:27 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat Capacity
Replies: 5
Views: 47

### Re: Heat Capacity

Does this mean that Specific heat capacity will always be less than molar heat capacity since it's 1 gram vs. 1 mole? Molar heat capacity is the amount of heat needed to raise the temperature of one mole of a pure substance by one degree Kelvin. Specific heat capacity is the amount of heat necessary...
Wed Jan 22, 2020 6:20 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic vs. Endothermic reactions
Replies: 12
Views: 428

### Exothermic vs. Endothermic reactions

Does anyone know if we will be asked on the test whether a reaction is exothermic or endothermic? If so, will the delta H value be given to us?
Sun Jan 19, 2020 9:41 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Identifying endothermic vs exothermic
Replies: 7
Views: 66

### Re: Identifying endothermic vs exothermic

If delta H is negative, it means that the reaction is exothermic (it releases energy). If delta H is positive, the reaction is endothermic (it requires energy).
Sun Jan 19, 2020 9:33 pm
Forum: Ideal Gases
Topic: R constant in Ideal Gas Law
Replies: 4
Views: 38

### Re: R constant in Ideal Gas Law

I think the question would state which units you need to use. If not, pay attention to the units of pressure. For example, if you are given the pressure in order to find the volume, you should use the R constant that has the same units as pressure in order for them to cancel out each other.
Sun Jan 19, 2020 9:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Relationship between pressure and volume
Replies: 10
Views: 86

### Re: Relationship between pressure and volume

Yes, they are. When you decrease a volume molecules have less space to move around, so they collide more--increasing the pressure. When you increase the volume molecules have more space and therefore, collide less--decreasing the pressure.
Sun Jan 19, 2020 8:58 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: X was ignored
Replies: 27
Views: 208

### Re: X was ignored

The x value is so small that when you subtract it from .10 it doesn't make a big chante to it, so you can ignore it. When you ignore it, it becomes easier to solve for x because you would now have Ka = x^2/.10
Mon Jan 13, 2020 10:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentrations and the K value.
Replies: 7
Views: 71

### Re: Concentrations and the K value.

This definitely makes sense!!! Thanks. The way I explain it to myself is that these stoichiometric coefficients are just telling us more than one of these species was formed. For example, in the balanced chemical equation to form water, 2H2 + O2 <-> 2H2O, the equation is telling us that two H2O spec...
Mon Jan 13, 2020 10:53 pm
Forum: Ideal Gases
Topic: ICE tables
Replies: 9
Views: 97

### ICE tables

How do you know whether to use the concentration or pressure of a gas when doing ICE tables? Also, if I use the pressure of a gas, what units do I use?
Sun Jan 12, 2020 1:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.61b
Replies: 3
Views: 23

### Re: 5.61b

You only take into account the gases, that's why when compressing the system there's no effect on the equilibrium since there is the same amount of moles of gas on both sides of the reaction.
Sun Jan 12, 2020 12:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentrations and the K value.
Replies: 7
Views: 71

### Concentrations and the K value.

Does anyone know the reason as to why the coefficients in a reaction become the exponents of the concentration values?
Sun Jan 12, 2020 12:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: predicting effects
Replies: 9
Views: 149

### Re: predicting effects

The way I think about it is that if you remove SO3, NO will increase because it has to make up for the SO3 that's being removed in order for the reaction to be at equilibrium.
Sun Jan 12, 2020 12:45 am
Forum: Ideal Gases
Topic: PV = nRT
Replies: 16
Views: 164

### Re: PV = nRT

Remember that this equation can be rewritten as P=nRT/V, and n/V is the same as concentration. So, P=concentration times RT.

P: Pressure
V: Volume in liters
n: number of moles
R: Ideal gas constant
T: Temperature in Kelvin
Sun Jan 12, 2020 12:34 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Different K's
Replies: 5
Views: 84

### Re: Different K's

Kc is the equilibrium constant when using concentrations and Kp is for when using pressures.