## Search found 52 matches

Sat Mar 17, 2018 2:04 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: When is Delta G equal to maximum work?
Replies: 2
Views: 354

### Re: When is Delta G equal to maximum work?

Is there a way to approach this problem conceptually and going around using differential equations? Lavelle actually posted this years ago but hopefully it helps (: G is actually defined as the maximum non-expansion work under constant T and P. Non-expansion means not related to a volume change, for...
Sat Mar 17, 2018 1:59 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: pseudo equilibrium constants
Replies: 1
Views: 156

### Re: pseudo equilibrium constants

Delta G (dagger) is a way to distinguish the amount of free energy available to do work at the pseudo equilibrium of a TRANSITION STATE/INTERMEDIATE STEP

This value is different to the delta G (or free energy available) of the overall reaction.

I hope this helps (:
Sat Mar 17, 2018 1:49 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: When is Delta G equal to maximum work?
Replies: 2
Views: 354

### When is Delta G equal to maximum work?

We know that a negative delta G implies spontaneity but does the correlation where delta G equal max work only apply for standard conditions?
Fri Mar 16, 2018 6:01 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy
Replies: 5
Views: 419

### Activation Energy

When given a graph interpretation of a reaction, why does activation energy sometimes change in multi step chemical reaction?
Fri Mar 16, 2018 5:49 pm
Forum: General Rate Laws
Topic: Substitution Reactions
Replies: 2
Views: 192

### Re: Substitution Reactions

What is a leaving group?
For substitution reactions, I thought we only replaced the intermediates
Fri Mar 16, 2018 5:47 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15. 103
Replies: 1
Views: 156

### Re: 15. 103

A poikilotherm is an animal whose internal temperature varies considerably. -Wikipedia Since temperature is one of the parameters that affects rate constant/law(s) an animal with the ability to vary their internal temperature means they have the ability to change the rate of the reaction mechanisms ...
Fri Mar 16, 2018 5:44 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Question 9.20
Replies: 1
Views: 247

### Re: Question 9.20

What is the question? (:
Fri Mar 16, 2018 5:43 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.69
Replies: 1
Views: 151

### Re: 15.69

If "the new pathway has a different pre-exponential factor"

then yes

A is a different value.

The problem usually directs what pre-exponential factor to use when solving, say for, rate law/constant.
Fri Mar 16, 2018 5:41 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test #2 Question 5
Replies: 5
Views: 306

### Re: Test #2 Question 5

The reducing agent has the ability to oxidize.

Highest oxidizing power is determined by reducing agent.
Fri Mar 16, 2018 5:36 pm
Forum: *Aldehydes
Topic: Identifying Aldehyde
Replies: 1
Views: 446

### Identifying Aldehyde

when identifying aldehyde

do you include both carbons or just the carbon bonded to the OH?

Thanks
Wed Mar 14, 2018 9:44 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium Approach
Replies: 1
Views: 146

### Pre-Equilibrium Approach

When determining the Rate Law of a multiple step Reaction, what is the best way to determine which is the slow step? How do you find out if the step before it is in equilibrium, does the problem have to state it or does it have to do with A Big K value of [P]/[R] ?
Wed Mar 14, 2018 2:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Which to set as Anode and Cathode [ENDORSED]
Replies: 1
Views: 171

### Which to set as Anode and Cathode[ENDORSED]

Looking at an example problem: we are told we take out lab equipment to make galvanic cell which includes battery set up and 200ml of .008M CrCl3 200ml of .12M CuSO4 Copper wire Chrome platted wire How do we approach the problem to find which to use as the anode and which to use as the cathode. Do w...
Wed Mar 07, 2018 8:00 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Finding the intermediate(s)
Replies: 5
Views: 275

### Finding the intermediate(s)

How do we determine when a reactant is an intermediate?
Tue Mar 06, 2018 3:01 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Behavior
Replies: 3
Views: 437

### Re: Arrhenius Behavior

Useful equation to predict the value of a rate constant at one temperature from its value at another temperature!
Tue Mar 06, 2018 2:59 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Which compound to use
Replies: 3
Views: 199

### Re: Which compound to use

From the problems I have worked on in the book, we are typically instructed which compound to use as the intermediate. Sidenote: I don't think this will be included in test 3.
Tue Mar 06, 2018 2:57 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Determining Reaction Mechanism
Replies: 2
Views: 162

### Determining Reaction Mechanism

Will the problem typically tell us which step in the mechanism is the slow step? Are there clues in wording to look for that hint which step in mechanism is the slow step?
Tue Mar 06, 2018 2:54 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.19a
Replies: 2
Views: 192

### Re: 15.19a

I believe they made a very generous estimation and rounded the increase in rate between experiments 2 and 3. The change in [B] increased from 1.25 to 3.02 which is approx an increase of a multiple of 2. The change in the concentration is approx. an increase of a multiple of 3. Here is where I was co...
Tue Mar 06, 2018 1:49 am
Forum: Experimental Details
Topic: Rate Unit Conversion
Replies: 4
Views: 653

### Rate Unit Conversion

Is it necessary to convert the units of a rate to metric units of time, seconds, when doing rate calculations in (mols/Ls)?
Tue Mar 06, 2018 1:45 am
Forum: General Rate Laws
Topic: How the concentration of a reactant affects the rate of the reaction
Replies: 3
Views: 164

### How the concentration of a reactant affects the rate of the reaction

What are some of the ways that the concentration of a reactant affects the rate of the reaction ?
Tue Mar 06, 2018 1:41 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate Laws of Elementary Reactions
Replies: 4
Views: 200

### Re: Rate Laws of Elementary Reactions

Bimolecular elementary reactions are second order reactions!
Tue Mar 06, 2018 1:36 am
Forum: First Order Reactions
Topic: Zero-order vs. First-order reaction graphs
Replies: 5
Views: 2322

### Re: Zero-order vs. First-order reaction graphs

Does this mean that both of the graphs ( Zero-order and First-order reactions) would be straight straight lines but that the only difference would be the labeling of the y-axis. [A] for Zero-Order and ln[A] on the y-axis of First Order reaction graph.

What exactly are the different axis implying?
Tue Mar 06, 2018 1:30 am
Forum: Experimental Details
Topic: Rate Constant
Replies: 4
Views: 572

### Re: Rate Constant

Any are okay to use, some may be easier to use than others especially if there are constants!
Tue Mar 06, 2018 1:26 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.51
Replies: 6
Views: 356

### Re: 15.51

The slow reaction determines the overall reaction rate.
Tue Mar 06, 2018 1:23 am
Forum: First Order Reactions
Topic: When to use rate equations
Replies: 3
Views: 224

### Re: When to use rate equations

I believe there will be cases when both will be needed to solve problems
The first step of a problem could ask for us to use regular rate laws and given concentrations and a rate and to calculate k.

This k would be used with integrated rate laws to find the change in concentrations over time.
Tue Mar 06, 2018 1:17 am
Forum: Zero Order Reactions
Topic: Deriving Zero Order Half Life Equation
Replies: 1
Views: 223

### Deriving Zero Order Half Life Equation

To gain a better understanding of the concept behind half life, I am trying to get a sense of how the equations were derived.

Can anyone point me in the right direction to find the derivation of the half-life for zero order reaction

Zero order reaction: half-life= [A]o/2k
Tue Mar 06, 2018 1:13 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Rate Constant Calculations [ENDORSED]
Replies: 3
Views: 348

### Rate Constant Calculations[ENDORSED]

Can Rate Constant of a reaction be determined by solely given order of the reaction and initial concentration of reactant(s)?
Tue Mar 06, 2018 1:10 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Method of initial rate vs more than one reactant
Replies: 2
Views: 216

### Re: Method of initial rate vs more than one reactant

if reaction rate ia to be found in a reaction with more than one reactant, than we must pay attention to what reactant the problem wants us to find the rate is respect of. If Initial rate of reactant given is not the reactant of interest than we must convert it in terms of the consumption of the oth...
Tue Mar 06, 2018 1:05 am
Forum: First Order Reactions
Topic: Key Words for First Order Reactions Half Life Problems
Replies: 2
Views: 193

### Key Words for First Order Reactions Half Life Problems

I am having a hard time identifying the order of a reaction given half life reaction time t1/2.

Are there key words or phrases that indicate a reaction is first order when determining half life reaction time?
Mon Mar 05, 2018 10:44 am
Forum: Second Order Reactions
Topic: Half-life of second order reactions
Replies: 2
Views: 468

### Re: Half-life of second order reactions

The half life of any reaction is the amount of time it takes to consume half of the initial material. For a second-order reaction, the half-life is inversely related to the initial concentration of the reactant (A). For a second-order reaction each half-life is twice as long as the life span of the ...
Sun Jan 21, 2018 9:52 pm
Forum: Phase Changes & Related Calculations
Topic: Calculating the Initial Temperature Of An Object
Replies: 3
Views: 411

### Re: Calculating the Initial Temperature Of An Object

The answer I'm getting is approx:

40.2 C for initial Temp. of Cu

This makes sense b/c in order for the water to increase temp, it had to transfer from a hotter object (2nd Law of Thermo)
Sat Jan 20, 2018 12:24 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: W=-(Pex)(deltaV)
Replies: 5
Views: 526

### Re: W=-(Pex)(deltaV)

Yes, when a system does work, work leaves the system -- resulting in a net loss of work from the "perspective of the system."
Sat Jan 20, 2018 11:41 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: the sign of q and w [ENDORSED]
Replies: 6
Views: 338

### Re: the sign of q and w[ENDORSED]

To answer the latest question: "If w decreases, will the internal energy increases or decreases" It depends if w is positive or negative - if the work done on the system decreases (+w) The change in internal energy of the system (deltaU) decreases Or - if the work done by the system decrea...
Sun Dec 10, 2017 10:22 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Weak Acid pH
Replies: 1
Views: 307

### Re: Weak Acid pH

The amount of an acid does not effect strength/ pH,

the concentration of H3O+

that an acid produces
when deprotanized

is directly related to the strength
Sun Dec 10, 2017 10:16 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.89
Replies: 1
Views: 319

### Re: 11.89

If you notice the units on the y-axis of graph are in

kPa

We calculate equilibrium constants in

atm (atmospheres)

I am assuming a unit conversion was made when dividing by 100 since

1 atm = 101.3 kPa ~ 100 kPa

:)
Sun Dec 10, 2017 9:14 am
Forum: Conjugate Acids & Bases
Topic: 12.131
Replies: 1
Views: 331

### Re: 12.131

(A) The H+ in lactic acid can interact w HbO2- to produce HHb and release oxygen, which means concentartion of HbO2- will be lower in the tissue

(B) Since more Hb- will return to the lung, more oxygen will be bound to Hb-, to produce HbO2- which will increase the concentartion of HbO2-
Sun Dec 10, 2017 9:06 am
Forum: Octet Exceptions
Topic: Exceptions [ENDORSED]
Replies: 7
Views: 644

### Re: Exceptions[ENDORSED]

Atoms that include the 3d orbital can have expanded octets.

The Xe in XeF4 breaks the octet rule and can have expanded octet since Xe includes 3d orbital

Hope this helps!
Sun Dec 10, 2017 9:02 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: carboxylic strength
Replies: 2
Views: 316

### Re: carboxylic strength

Find the concentration of [H3O+] to determine strength or ph of any acid:

pH = - log ([H3O+])

We will be provided w an equilibrium constant Ka to determine whether given amounts of acid are in equilibrium.
Sun Dec 10, 2017 8:57 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 11.115 (f) equilibrium shift
Replies: 1
Views: 252

### Re: 11.115 (f) equilibrium shift

Water has no effect on the reaction of aqueous solutions since they are in fact surrounded by water.

Adding water allows us to visually see the protonation or deprotonation of an acid or a base:

Base + H2O <---> OH- + conjugate acid
Acid + H2O <---> H3O+ + conjugate base
Sun Dec 10, 2017 8:40 am
Forum: Formal Charge and Oxidation Numbers
Topic: Oxidation Number
Replies: 1
Views: 239

### Re: Oxidation Number

In order to find oxidation number you must pay attention to the following: - Overall charge of the ion - The number of ligands and each ligand's charge - Number of metal atoms The oxidation number of the Iron (Fe) in the picture below is 3+. I determined the oxidation number by paying attention to t...
Sun Dec 10, 2017 8:28 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Replies: 3
Views: 271

### Re: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions

In a Homogeneous Reaction is one that includes only one phase - i.e. if all the products and reactants are in the gas phase, then the reaction is homogeneous
Sun Dec 10, 2017 2:36 am
Forum: Empirical & Molecular Formulas
Topic: empirical vs theoretical vs derived relationship/formula
Replies: 1
Views: 387

### Re: empirical vs theoretical vs derived relationship/formula

The way I like to remeber it is that, Empirical formulas Are based on real experimental results For example the equation that gives us the change in energy levels of electrons in hydrogen atoms: -hR/(n^2) Was derived by observing and finding a relationship between the changes in energy of these elec...
Sun Dec 10, 2017 2:28 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: dotted line that is not resonance
Replies: 1
Views: 211

### Re: dotted line that is not resonance

When in comes to coordination compounds: the dotted lines represent denticity, sites where the ligand can bind to the transitional metal If a ligand shows two dotted lines extending from it, this indicates that the ligand is a bidentate Usually these dotted lines extend from N and O because of their...
Sun Dec 10, 2017 2:15 am
Forum: Lewis Acids & Bases
Topic: the importance of protonation
Replies: 2
Views: 245

### Re: the importance of protonation

Protonation tells how much of a given base has had protons added to reach equilibrium. The x value we determine at the end of ICE tables is the amount of product or reactant that has had protons added [Base]+H2O <--> [BaseH^+]+[OH^-] I can def see this show up on the test. This has to do w Acids and...
Sun Dec 10, 2017 2:04 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Video Module: Calculate Reaction Quotient
Replies: 1
Views: 306

### Re: Video Module: Calculate Reaction Quotient

The reaction quotient Qc is the ratio between the [P] and [R] at their current/provided values. Here you are given number of moles. In order to determine concentration from number of moles: Divide number of moles / by volume (L) Use these molarities as your concentartion amounts to determine Qc by p...
Sun Dec 10, 2017 1:43 am
Forum: Dipole Moments
Topic: SiO2
Replies: 2
Views: 274

### Re: SiO2

SiO2 is Polar because the dipole moments do not cancel each other. If the dipole momements cancel it is non-polar.
Sun Dec 10, 2017 1:31 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Delocalized Electrons
Replies: 3
Views: 453

### Re: Delocalized Electrons

I believe resonance indicates delocalization.

If a structure like

a benzene ring (C6H6)

shows resonance in the double bonds,

meaning the double bonds can be drawn in an alternating pattern without effecting overall charge

then the structure also shows delocalized bonding !
Sun Dec 10, 2017 1:23 am
Forum: Ideal Gases
Topic: Value of R
Replies: 3
Views: 1690

### Re: Value of R

Value of R is the Gas Constant
Sat Dec 09, 2017 11:27 pm
Forum: Lewis Structures
Topic: Same Formal Charge and Different Stability? [ENDORSED]
Replies: 2
Views: 252

### Same Formal Charge and Different Stability?[ENDORSED]

If the formal charge is the same in two Lewis Structures how do you determine which is more stable? I have attached an image of two Lewis Structures for NCO^- The solution I am provided states that the structure with the triple bond is the most stable. Although they cancel, this structure shows form...
Sat Dec 09, 2017 7:00 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Bigger or Smaller Acidity Constant in Cations?
Replies: 1
Views: 290

### Bigger or Smaller Acidity Constant in Cations?

Hi

Would you expect Ka (Acidity Constant) of

[Fe(H20)6]^2+

to be bigger or smaller than

[Fe(H20)6]^3+

?

I understand that the iron cation w 3+ has a higher positive charge. What does that tell us about Ka?

Ty!
Sat Dec 09, 2017 5:17 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Relationship between pH, protanation and molarity
Replies: 5
Views: 463

### Relationship between pH, protanation and molarity

Hi

How can pH or pOH be found
given % protonation/deprotanation and molarity?

Ty!
Sat Dec 09, 2017 4:15 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic vs. Endothermic
Replies: 1
Views: 281

### Exothermic vs. Endothermic

Hi,

If an increases in temperature increases the value of equilibrium constant K, does that mean the reaction is exothermic/endothermic?

My understanding is that it takes in more heat. Then not sure how to determine reaction type (endo/exothermic).

Ty!
Sat Dec 09, 2017 4:02 pm
Forum: Naming
Topic: Ligand Prefixes: Di- vs. Bis-
Replies: 1
Views: 272

### Ligand Prefixes: Di- vs. Bis-

How do we know when to use "di-" , "tri-" etc. as the prefix of a ligand compared to "bis-" , "tris-", etc. ?

ty!

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