Search found 77 matches
- Sun Mar 13, 2016 12:05 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy of surroundings for irreversible expansion
- Replies: 1
- Views: 403
Entropy of surroundings for irreversible expansion
Why is surrounding entropy = 0 for an irreversible expansion? The question was posed before, but with no confirmed answer. Thanks.
- Sat Mar 12, 2016 5:43 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Redundant Numbering
- Replies: 1
- Views: 313
Redundant Numbering
Hi,
Is it acceptable to use redundant numbering when naming?
For example, will propan-1-al be accepted for full credit?
Thanks.
Is it acceptable to use redundant numbering when naming?
For example, will propan-1-al be accepted for full credit?
Thanks.
- Fri Mar 11, 2016 8:05 pm
- Forum: *Cycloalkenes
- Topic: Winter 2012 Final Exam Q5
- Replies: 3
- Views: 637
Re: Winter 2012 Final Exam Q5
Chem_Mod wrote:Yeah, it has to do with the double bond.
Could you explain what the double bond means in terms of the cis/trans? Thanks.
- Fri Mar 11, 2016 3:19 pm
- Forum: *Cycloalkenes
- Topic: Winter 2012 Final Exam Q5
- Replies: 3
- Views: 637
Winter 2012 Final Exam Q5
Hi,
For this question, which asks for the IUPAC name for a cycloalkene with only one functional group that sticks out of the main chain, how do we decide if it is cis or trans? Does it have something to do with the double bond?
Thanks.
For this question, which asks for the IUPAC name for a cycloalkene with only one functional group that sticks out of the main chain, how do we decide if it is cis or trans? Does it have something to do with the double bond?
Thanks.
- Wed Mar 09, 2016 11:19 pm
- Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
- Topic: Signs for Dihedral Angles
- Replies: 1
- Views: 344
Signs for Dihedral Angles
Hi.
Do the + and - in dihedral angles refer to the back carbon rotating or the front one?
Also, do we have to include signs for the final? or can we simply state the angle?
Thanks.
Do the + and - in dihedral angles refer to the back carbon rotating or the front one?
Also, do we have to include signs for the final? or can we simply state the angle?
Thanks.
- Wed Mar 09, 2016 12:17 am
- Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
- Topic: Newman projections when 2 carbons are not specified.
- Replies: 1
- Views: 334
Newman projections when 2 carbons are not specified.
Hi,
How do we decide which carbons to draw a Newman projection for if they are not stated?
One example is Self-Test 3.3B in Intro to Organics.
Draw a Newman projection for the gauche conformation of 1-iodobutane.
Thanks.
How do we decide which carbons to draw a Newman projection for if they are not stated?
One example is Self-Test 3.3B in Intro to Organics.
Draw a Newman projection for the gauche conformation of 1-iodobutane.
Thanks.
- Mon Mar 07, 2016 11:33 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Uses of Various Functional Groups and Organic Comp
- Replies: 1
- Views: 313
Uses of Various Functional Groups and Organic Comp
Hi,
For the final do we have to memorize the various real-world connections for various functional groups and organic compounds?
For example, that Ethanal is present in plants and their products?
Thanks.
For the final do we have to memorize the various real-world connections for various functional groups and organic compounds?
For example, that Ethanal is present in plants and their products?
Thanks.
- Mon Mar 07, 2016 10:16 pm
- Forum: *Alkynes
- Topic: Priority of Double Bonds, Triple Bonds, and other F. Groups
- Replies: 1
- Views: 1570
Priority of Double Bonds, Triple Bonds, and other F. Groups
Hi, I was wondering the priority for double bonds, triple bonds, and other functional groups. I believe double and triple bonds take priority over all other functional groups. I also think that double bonds take priority over triple bonds. These conclusions are derived from various examples. Can som...
- Mon Mar 07, 2016 9:55 pm
- Forum: *Alcohols
- Topic: Naming priority between double bond and functional group
- Replies: 4
- Views: 9914
Re: Naming priority between double bond and functional group
There is an example in the book where a double bond takes precedence over a chloro (halide) substituent...
Maybe halides are are an exception? If so, I would expect ethers to be as well...
Maybe halides are are an exception? If so, I would expect ethers to be as well...
- Mon Mar 07, 2016 9:09 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Steric Factor
- Replies: 1
- Views: 652
Re: Steric Factor
Hi, The unfavorable steric factor in terms of transition states refers to how the specific orientation requirement of a TS causes its change in entropy to be negative, and thus Free Energy change to be positive. In terms of steric strain, this refers to the conformational strain produced when the el...
- Mon Mar 07, 2016 9:01 am
- Forum: *Complex Reaction Coordinate Diagrams
- Topic: Reaction Profiles
- Replies: 1
- Views: 758
Re: Reaction Profiles
Hi,
The products are thermodynamically stable if they have lower Free Energy than the reactants (1&2).
A reaction is kinetically stable if it has a high activation energy, because few reactants will become products at normal temperatures (2&4).
The products are thermodynamically stable if they have lower Free Energy than the reactants (1&2).
A reaction is kinetically stable if it has a high activation energy, because few reactants will become products at normal temperatures (2&4).
- Thu Mar 03, 2016 9:25 pm
- Forum: *Alkanes
- Topic: Substituents in Condensed Structural Formula
- Replies: 1
- Views: 298
Substituents in Condensed Structural Formula
Hi.
Are Substituents still placed in parentheses for Condensed Structural Formulas?
Thanks.
Are Substituents still placed in parentheses for Condensed Structural Formulas?
Thanks.
- Tue Mar 01, 2016 8:12 pm
- Forum: *Alkanes
- Topic: Alphabetizing Alkyls and Halogens
- Replies: 1
- Views: 302
Alphabetizing Alkyls and Halogens
Hi, I was wondering if you alphabetize when both alkyls and halogens are included in a structure.
That is, if both chlorine and a methyl group were attached to an alkane, would the structure be for example, 2- chloro-3-methylnonane?
That is, if both chlorine and a methyl group were attached to an alkane, would the structure be for example, 2- chloro-3-methylnonane?
- Tue Mar 01, 2016 8:10 pm
- Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
- Topic: Cis/Trans
- Replies: 3
- Views: 598
Re: Cis/Trans
Nope. Because for triple bonds, there is only one structure possible. A linear one.
- Mon Feb 29, 2016 8:50 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Activation Energy
- Replies: 1
- Views: 329
Re: Activation Energy
The distance between the reactant potential energy and the potential energy of the transition state is the activation energy needed to cause that reaction to occur.
- Mon Feb 29, 2016 8:48 pm
- Forum: *Alcohols
- Topic: Naming priority between double bond and functional group
- Replies: 4
- Views: 9914
Re: Naming priority between double bond and functional group
I think we prioritize other functional groups over double bonds. Would be great if someone could confirm.
- Mon Feb 29, 2016 8:45 pm
- Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
- Topic: Cis/Trans
- Replies: 3
- Views: 598
Re: Cis/Trans
First of all, cis and trans isomers occur only when there are double bonds in the molecule. To determine cis or trans, look individually at each carbon and what is connected to it. Decide which of the two species connected to each carbon is greater in atomic number, and if they are the same, keep mo...
- Sun Feb 28, 2016 2:03 pm
- Forum: *Alkanes
- Topic: Capitalization in (Organic) Naming
- Replies: 1
- Views: 377
Capitalization in (Organic) Naming
In general, does capitalization matter for organic naming?
If so, when do we capitalize?
I've seen things capitalized and not capitalized, so just want to check.
Thanks.
If so, when do we capitalize?
I've seen things capitalized and not capitalized, so just want to check.
Thanks.
- Sat Feb 27, 2016 10:16 pm
- Forum: *Alkenes
- Topic: Condensed Structural Formulas for Alkenes and Alkynes
- Replies: 1
- Views: 1416
Condensed Structural Formulas for Alkenes and Alkynes
Hi, I was wondering for condensed structural formulas of Alkenes and Alkynes, do the double and triple bonds have to be shown? For example, would the condensed structural formula of butene be CH2=CHCH2CH3 or CH2CHCH2CH3? Also, just to confirm, the condensed structural formula and structural formula ...
- Wed Feb 24, 2016 10:19 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Why will this TS not have negative enthalpy?
- Replies: 1
- Views: 407
Why will this TS not have negative enthalpy?
Hi I was wondering why transition states always have positive enthalpy changes despite TS that involve solely bond formation. One example would be the second step of electrophilic addition of HBr to Propene in which the second step involves a Br anion attaching to a carbocation. Since the formation ...
- Wed Feb 24, 2016 10:16 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Why Transition States always have Positive Enthalpy
- Replies: 2
- Views: 502
Re: Why Transition States always have Positive Enthalpy
Yes. That's right. But what about the example I gave?
- Wed Feb 24, 2016 7:45 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Why Transition States always have Positive Enthalpy
- Replies: 2
- Views: 502
Why Transition States always have Positive Enthalpy
Hi I was wondering why transition states always have positive enthalpy changes despite TS that involve solely bond formation. One example would be the second step of electrophilic addition of HBr to Propene in which the second step involves a Br anion attaching to a carbocation. Since the formation ...
- Tue Feb 23, 2016 9:13 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Electrolysis
- Replies: 1
- Views: 315
Re: Electrolysis
An external energy source supplies electric current to an electrolytic cell. By introducing an external current, it can drive a non spontaneous reaction. In an electrolytic cell, both electrodes are submerged in the SAME solution. When the positive ions in the solution collide with the negative elec...
- Tue Feb 23, 2016 6:04 pm
- Forum: *Alkanes
- Topic: Naming Compounds Clarification
- Replies: 1
- Views: 349
Re: Naming Compounds Clarification
I agree with your first question that the ordering seems strange. To answer your second question, the substituent listed first is always given the lower number if equivalent numbering is possible. However, if lower numbers in general can be obtained by giving the first substituent a higher number th...
- Thu Feb 18, 2016 10:28 pm
- Forum: General Rate Laws
- Topic: Unique Rate Law
- Replies: 1
- Views: 397
Re: Unique Rate Law
Good question.
I think since we are told to find the initial rate of decomposition and we know that E is consumed at 5 times the unique average rate (which applies without alteration only to species with coefficient 1), we should multiply by 5.
Would double check though.
I think since we are told to find the initial rate of decomposition and we know that E is consumed at 5 times the unique average rate (which applies without alteration only to species with coefficient 1), we should multiply by 5.
Would double check though.
- Thu Feb 18, 2016 10:18 pm
- Forum: General Rate Laws
- Topic: General Rate Laws
- Replies: 1
- Views: 292
Re: General Rate Laws
I'm not 100% sure what you are asking, but the differential rate law (Rate=k[A]^n) is useful for comparison between data in experiments to determine what the orders are for each reactant.
- Tue Feb 16, 2016 7:14 pm
- Forum: General Rate Laws
- Topic: How Balancing Affects Rate Law
- Replies: 1
- Views: 420
How Balancing Affects Rate Law
Hi, I was wondering if equations should be balanced before rate laws are derived. That is, for Question 3 of Quiz Prep 2, the question states that rate=k[N2O]... However, when the reaction in question is balanced, N2O has a 2 coefficient. Does this not change the rate equation to become rate=k[N2O]^...
- Tue Feb 16, 2016 7:09 pm
- Forum: General Rate Laws
- Topic: Units question
- Replies: 2
- Views: 425
Re: Units question
If the question does not specify differently, I would use the time units that are used in the givens.
- Mon Feb 15, 2016 1:36 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Pseudo Rate Laws
- Replies: 1
- Views: 402
Re: Pseudo Rate Laws
The concentration of the reactant being tested has to be small enough relative to the concentration of the other reactants that the concentration of the other reactants will remain essentially constant as the reactant being tested is being consumed.
- Mon Feb 15, 2016 1:32 pm
- Forum: First Order Reactions
- Topic: Initial Rate
- Replies: 1
- Views: 327
Re: Initial Rate
You can assume first order with respect to the species in question when the reaction rate doubles due to a doubling of the concentration of that species.
- Tue Feb 09, 2016 11:41 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneity
- Replies: 2
- Views: 450
Re: Spontaneity
deltaS represents the entropy change of the exact reaction you are looking at. deltaSo represents the entropy change of the reaction at standard conditions. While deltaS0 might be positive and thus spontaneous at normal conditions, deltaS might not be positive at certain conditions (or visa versa). ...
- Tue Feb 09, 2016 8:53 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: change in entropy for adiabatic systems
- Replies: 4
- Views: 920
Re: change in entropy for adiabatic systems
For reversible adiabatic process, delta S should be 0. I can see that is true through deltaS=q/T, since deltaS will be 0 when q is 0. However, if V2/V1 can be substituted for T2/T1 in the equation deltaS=nCln(T2/T1), then how does this equation show deltaS as 0 when q=0 (adiabatic)? Is this equatio...
- Mon Feb 08, 2016 6:41 pm
- Forum: Calculating Work of Expansion
- Topic: Ideal Gases Formula Pt. 2
- Replies: 2
- Views: 386
Re: Ideal Gases Formula Pt. 2
One instance would be when you find the change in entropy of a monatomic ideal gas due to change in temperature.
- Mon Feb 08, 2016 6:39 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: change in entropy for adiabatic systems
- Replies: 4
- Views: 920
Re: change in entropy for adiabatic systems
Factors other than heat flow (q) can affect entropy. For example, if volume was increased for a gas, there would be more entropy since the gas molecules have more possible micro states in which to exist.
- Tue Feb 02, 2016 2:00 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Notation
- Replies: 1
- Views: 298
Re: Cell Notation
I'm not 100% sure, but from what I have seen, the cell notation usually follows the order that the ions are consumed and produced.
If the reaction was Fe(III) + e- --> Fe(II), for example, I think it would be Fe3+, Fe2+ since Fe3+ becomes Fe2+.
Would be great if someone could verify.
If the reaction was Fe(III) + e- --> Fe(II), for example, I think it would be Fe3+, Fe2+ since Fe3+ becomes Fe2+.
Would be great if someone could verify.
- Mon Feb 01, 2016 6:25 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Emax/wmax
- Replies: 1
- Views: 480
Re: Emax/wmax
E=Electromotive force=Cell potential. Cell potential is the amount of electrical potential energy created by differences in the charge of two half cells. It is greatest when the current is near 0 and the electrons experience the strongest pull from one half cell to the other. Wmax is the maximum amo...
- Tue Jan 26, 2016 5:26 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Which has more entropy?
- Replies: 4
- Views: 2510
Which has more entropy?
Hi.
For the same mass, would fewer, larger molecules have more entropy or more, smaller molecules. Why?
For the same mass, would fewer, larger molecules have more entropy or more, smaller molecules. Why?
- Tue Jan 26, 2016 12:46 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Molar Heat Capacity
- Replies: 1
- Views: 357
Re: Molar Heat Capacity
Diatomic or polyatomic gases have higher molar heat capacities than monoatomic gases because they have more fundamental particles that are able to absorb energy and use it to perform translational/ vibrational/ rotational motion.
- Tue Jan 26, 2016 12:35 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: When to use R or C?
- Replies: 1
- Views: 464
Re: When to use R or C?
It's a typo. You're right. Use C for entropy calculation.
See link: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Solution_Manual_Errors_6Ed.pdf
See link: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Solution_Manual_Errors_6Ed.pdf
- Sun Jan 24, 2016 2:35 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Work/ reversible expansion
- Replies: 1
- Views: 324
Re: Work/ reversible expansion
Isothermal means that the temperature does not change during this expansion. Reversible means that the expansion can be reversed with the slightest push from external forces. Essentially, the system goes to equilibrium with the surroundings at each infinitely small step of the expansion. The pressur...
- Sun Jan 24, 2016 12:17 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Coefficients for Calculating Standard Enthalpy
- Replies: 1
- Views: 363
Coefficients for Calculating Standard Enthalpy
Hi.
What coefficients are used when calculating standard enthalpy for a reaction?
Some sources say to make the lowest coefficient 1 in the equation, and others say to make the molecule in question have a coefficient of 1 (with other molecules having fractional coefficients)...
What coefficients are used when calculating standard enthalpy for a reaction?
Some sources say to make the lowest coefficient 1 in the equation, and others say to make the molecule in question have a coefficient of 1 (with other molecules having fractional coefficients)...
- Fri Jan 22, 2016 10:33 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calculating final temperature of a substance
- Replies: 1
- Views: 300
Re: Calculating final temperature of a substance
Use the temperature provided for each substance as its initial temperature.
Then use Tf in your equation to represent final temperature. Tf will be the same for both substances after the temperatures comes to equilibrium.
Finally, you can combine the two Tf's into one variable and solve.
Then use Tf in your equation to represent final temperature. Tf will be the same for both substances after the temperatures comes to equilibrium.
Finally, you can combine the two Tf's into one variable and solve.
- Tue Jan 19, 2016 4:56 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Standard entropy of vaporization of water (HW 9.19)
- Replies: 2
- Views: 514
Re: Standard entropy of vaporization of water (HW 9.19)
For the phase change piece, you use the entropy of vaporization of water at 100C, which is 109.0J/Kmol.
For the other pieces, yes, use dS=Cln(T2/T1).
Then, add al the pieces together to get total S change.
For the other pieces, yes, use dS=Cln(T2/T1).
Then, add al the pieces together to get total S change.
- Mon Jan 18, 2016 9:18 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Entropy
- Replies: 1
- Views: 318
Re: Entropy
Entropy is an extensive property because it depends on the volume of the substance in question.
When there is more volume, there is greater degeneracy since there are more microstates for the same energy state to be achieved.
Greater degeneracy equates to greater Entropy by the equation: S=kBlnW
When there is more volume, there is greater degeneracy since there are more microstates for the same energy state to be achieved.
Greater degeneracy equates to greater Entropy by the equation: S=kBlnW
- Mon Jan 11, 2016 11:18 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Purpose of Pressurized Oxygen Gas in Bomb Calorimeter
- Replies: 1
- Views: 499
Purpose of Pressurized Oxygen Gas in Bomb Calorimeter
Hi.
What is the purpose of the pressurized oxygen gas in bomb calorimeters?
I presume it has something to do with isolating the sample from the environment?
Thanks.
What is the purpose of the pressurized oxygen gas in bomb calorimeters?
I presume it has something to do with isolating the sample from the environment?
Thanks.
- Mon Jan 11, 2016 11:11 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Reg Calorimeter v. Bomb Calorimeter
- Replies: 3
- Views: 4181
Re: Reg Calorimeter v. Bomb Calorimeter
A bomb calorimeter provides an isolated system at constant pressure and volume.
A regular calorimeter, such a coffee cup calorimeter, allows pressure to equalize with the environment.
Essentially, a bomb calorimeter is airtight/sealed, while a regular calorimeter is open.
A regular calorimeter, such a coffee cup calorimeter, allows pressure to equalize with the environment.
Essentially, a bomb calorimeter is airtight/sealed, while a regular calorimeter is open.
- Fri Jan 08, 2016 2:24 pm
- Forum: Phase Changes & Related Calculations
- Topic: Definition of a State Function
- Replies: 2
- Views: 378
Re: Definition of a State Function
- A state function refers to an intrinsic property of a substance/object. - Enthalpy is equal to the total heat content of a system. - The total heat content of a system is an intrinsic property. It exists even when the object/substance is not undergoing any action. - Heat on the other hand, refers ...
- Fri Jan 08, 2016 2:19 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat capacity of an ideal gas
- Replies: 1
- Views: 346
Re: Heat capacity of an ideal gas
- Heat capacity is the amount of heat needed to raise the temperature of a substance/object in question by one degree. - For any gas, an increase in temperature causes it to expand. - For a gas at constant pressure, this expansion causes it to push against the atmospheric pressure of the surrounding...
- Sun Dec 06, 2015 1:32 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Acid Strength
- Replies: 1
- Views: 699
Re: Acid Strength
See which conjugate bases for the acids will be most stable and most able to withdraw negative charge/electrons after deprotonation.
Generally, conjugate bases with resonance and electronegative atoms will be correspondent to stronger acids
Generally, conjugate bases with resonance and electronegative atoms will be correspondent to stronger acids
- Sun Dec 06, 2015 1:29 pm
- Forum: Conjugate Acids & Bases
- Topic: Conjugate Base Stability
- Replies: 2
- Views: 2712
Re: Conjugate Base Stability
It means that after the acid is deprotonated, the high amounts of negative charge are withdrawn by other atoms on the conjugate base, and the resonance helps to distribute the negative charge for more stability.
- Sun Dec 06, 2015 1:27 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Bond Order and Bond Length
- Replies: 6
- Views: 1295
Re: Bond Order and Bond Length
Greater bond order = stronger bond = shorter bond
- Sun Dec 06, 2015 1:26 pm
- Forum: *Titrations & Titration Calculations
- Topic: solving quadratics
- Replies: 1
- Views: 364
Re: solving quadratics
If the x is less than 5% of the quantity it is subtracted by, it may be omitted because it is relatively so much smaller.
- Sun Dec 06, 2015 11:02 am
- Forum: *Titrations & Titration Calculations
- Topic: Find the final pH of the final solution in a titration
- Replies: 1
- Views: 581
Re: Find the final pH of the final solution in a titration
pH of a titration of strong base with a strong acid is 7.
The ions attached to the H+ and OH- do not affect pH and combine to produce a neutral salt.
As for finding volume, calculate how many moles of base need to be neutralized.
Then, calculate the volume of acid that will contain that many moles.
The ions attached to the H+ and OH- do not affect pH and combine to produce a neutral salt.
As for finding volume, calculate how many moles of base need to be neutralized.
Then, calculate the volume of acid that will contain that many moles.
- Thu Dec 03, 2015 1:56 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Using Moles in Ice Table
- Replies: 1
- Views: 5065
Using Moles in Ice Table
Hi,
When can one use moles in the ice table?
I assume only when the volume is 1L since Kc is a set value and applies when concentrations are used?
If volume is 1L, moles would essentially be the same as concentrations?
When can one use moles in the ice table?
I assume only when the volume is 1L since Kc is a set value and applies when concentrations are used?
If volume is 1L, moles would essentially be the same as concentrations?
- Mon Nov 30, 2015 1:22 pm
- Forum: *Biological Importance of Buffer Solutions
- Topic: Buffer solutions and salt
- Replies: 2
- Views: 1015
Re: Buffer solutions and salt
A salt is used to supply the conjugate acid/base of the weak acid/base that is being used as a buffer.
If no salt is added, the buffer might not be at the optimum level since the amount of acid/base and conjugate are not going to be necessarily equal.
If no salt is added, the buffer might not be at the optimum level since the amount of acid/base and conjugate are not going to be necessarily equal.
- Mon Nov 30, 2015 1:19 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Soluble salts
- Replies: 1
- Views: 411
Re: Soluble salts
By definition, a salt is an ionic compound. Thus, its component atoms/molecules are necessarily charged (either positive of negative). When these charged components interact with a polar medium such as water, the ionic components are pulled away from each other. A salt dissolves when the positive en...
- Mon Nov 30, 2015 11:23 am
- Forum: Conjugate Acids & Bases
- Topic: Acidic or Basic Buffer?
- Replies: 1
- Views: 482
Acidic or Basic Buffer?
Hi, Since weak acids and weak bases both function as buffers and can act as a sink or source of protons, does that mean that to buffer a solution, it does't matter whether a weak acid or weak base is used as long as the PKa is close to the desired pH? That is, a weak acid can buffer an acidic soluti...
- Fri Nov 27, 2015 6:45 pm
- Forum: Conjugate Acids & Bases
- Topic: NH4+ and NH3
- Replies: 3
- Views: 11100
NH4+ and NH3
Hi.
Normally the conjugate acid of a weak base is a strong acid, however, the conjugate acid of the weak base NH3 is a weak acid, NH4+.
Why is this the case?
Normally the conjugate acid of a weak base is a strong acid, however, the conjugate acid of the weak base NH3 is a weak acid, NH4+.
Why is this the case?
- Thu Nov 26, 2015 12:41 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Dissociation of a Compound
- Replies: 1
- Views: 400
Re: Dissociation of a Compound
If the species is a strong acid or base, it will dissociate essentially completely in water. If it is a weak acid/base, it will only dissociate partially in water, and some will remain in weak acid/base form. To determine if an acid/base is strong, examine the Ka or Kb value. If Ka or Kb is large, t...
- Mon Nov 23, 2015 6:55 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Selecting the Appropriate Buffer
- Replies: 1
- Views: 427
Selecting the Appropriate Buffer
Hi, Since buffers can be weak acids or bases and either will neutralize both strong acids and bases, how does one select the best buffering solution? I assume that adding a salt containing the conjugate of a weak acid or base would be the easiest way to adjust buffering capacity in which case weak a...
- Mon Nov 23, 2015 12:37 pm
- Forum: Lewis Acids & Bases
- Topic: Determining Strength of an Acid/Base
- Replies: 2
- Views: 802
Re: Determining Strength of an Acid/Base
To determine the strength of an Acid/Base, you can calculate and interpret the Ka and Kb values. Remember that Ka = [H+][A-] / [HA] and Kb = [BH+][OH-] / [B]. Ka and Kb are the acid and base dissociation constants respectively. A higher Ka or Kb would mean a stronger acid or base respectively. In ge...
- Mon Nov 16, 2015 2:05 pm
- Forum: Naming
- Topic: Ligand order in TM compound formulas & Bracket Use
- Replies: 1
- Views: 363
Ligand order in TM compound formulas & Bracket Use
Hi, When we write the formula for a TM, does it matter the order which the ligands are placed in? I know for naming that the ligands come in alphabetical order before the TM. For example, for tetraamminedichloronickelate(II), would the formula be: [NiCl2(NH3)4] or [Ni(NH3)4Cl2] Also, do we put brack...
- Mon Nov 16, 2015 1:53 pm
- Forum: Naming
- Topic: naming a given complex
- Replies: 1
- Views: 283
Re: naming a given complex
It's alphabetical, so cyano before ethylenediamine.
- Mon Nov 16, 2015 1:48 pm
- Forum: Naming
- Topic: WorkBook Preparation for Quiz 3
- Replies: 1
- Views: 257
Re: WorkBook Preparation for Quiz 3
Let's clarify first that both the CN- (cyano) and Cl- (chloro) are (anionic) ligands.
From there, we just put them in alphabetical order so chloro is before cyano.
From there, we just put them in alphabetical order so chloro is before cyano.
- Mon Nov 16, 2015 1:36 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Changes in both reactants and products
- Replies: 1
- Views: 372
Re: Changes in both reactants and products
If concentration of both reactants and products change, you would use the new concentrations as the initials in your ice table and calculate a Q value. Then you would compare the derived Q with the known K value during equilibrium. If Q is smaller than K, the reaction will proceed towards the produc...
- Mon Nov 09, 2015 1:07 pm
- Forum: Ideal Gases
- Topic: Effect of inert gasses on equilibrium
- Replies: 1
- Views: 404
Effect of inert gasses on equilibrium
Hi, I know that adding any quantity of inert gas to an equilibrium reaction has no effect on the equilibrium constant and reactant/product concentrations remain the same. However, I don't see why adding an inert gas does not shift the equilibrium towards the side with fewer moles of gas since the in...
- Mon Nov 02, 2015 8:33 pm
- Forum: Sigma & Pi Bonds
- Topic: Electron Configuration Involving Sigma and Pi bonds
- Replies: 5
- Views: 37201
Re: Electron Configuration Involving Sigma and Pi bonds
Yes, Lisa. The subscript numbers represent which energy level the (valence) electron(s) are in.
So if an electron was on Pi2px, for example, it would be in the 2nd energy level.
So if an electron was on Pi2px, for example, it would be in the 2nd energy level.
- Mon Nov 02, 2015 1:13 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Responding to Molecular Orbital Questions on the Midterm
- Replies: 1
- Views: 307
Responding to Molecular Orbital Questions on the Midterm
Hi, If asked to identify the molecular orbital that an unpaired electron occupies in a molecule, are we expected to provide all three of these or only 1 or 2 of them? (If all 3, an example answer would be Pi*2Py) 1. The energy level of the orbital 2. Whether it is bonding or antibonding 3. Shape of ...
- Fri Oct 30, 2015 10:20 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Fractional Bond Orders Greater than 1
- Replies: 1
- Views: 454
Fractional Bond Orders Greater than 1
Hi,
I was wondering if a molecule with a fractional bond order of 2.5 is more stable than a molecule with a integer bond number of 2. (It should be since 2.5 is greater than 2?)
Thanks.
I was wondering if a molecule with a fractional bond order of 2.5 is more stable than a molecule with a integer bond number of 2. (It should be since 2.5 is greater than 2?)
Thanks.
- Mon Oct 26, 2015 2:11 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Energy Levels for Antibonding Molecular Orbitals
- Replies: 1
- Views: 244
Energy Levels for Antibonding Molecular Orbitals
Hi,
For antibonding molecular orbitals, I was wondering why the sigma*s orbitals have a higher energy than the pi*p orbitals. In bonding orbitals, the opposite is true because s orbital electrons penetrate less than p orbital electrons.
Thanks.
For antibonding molecular orbitals, I was wondering why the sigma*s orbitals have a higher energy than the pi*p orbitals. In bonding orbitals, the opposite is true because s orbital electrons penetrate less than p orbital electrons.
Thanks.
- Mon Oct 19, 2015 5:16 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: The Square Planar Shape
- Replies: 1
- Views: 393
The Square Planar Shape
Hi all,
I was wondering why a molecule with Square Planar Configuration (AX4E2) would prefer staying in a 2D plane rather than using 3D space to minimize electron repulsion. Perhaps the 2D shape just happens to be the one that minimizes repulsions?
Thanks.
I was wondering why a molecule with Square Planar Configuration (AX4E2) would prefer staying in a 2D plane rather than using 3D space to minimize electron repulsion. Perhaps the 2D shape just happens to be the one that minimizes repulsions?
Thanks.
- Mon Oct 12, 2015 1:02 pm
- Forum: Octet Exceptions
- Topic: Affect of Radicals on DNA
- Replies: 1
- Views: 416
Affect of Radicals on DNA
In what way do radicals react/interact with DNA to damage it?
- Mon Oct 12, 2015 12:58 pm
- Forum: Lewis Structures
- Topic: Electron Orbitals in Lewis Structures
- Replies: 1
- Views: 259
Electron Orbitals in Lewis Structures
How does one correlate the electrons of a Lewis structure to which orbitals they are in? For example, for oxygen, is one electron pair assumed to belong to the s orbital while the other pair and unpaired electrons are assumed to belong to the p orbitals?
- Wed Oct 07, 2015 7:57 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Energy Levels of d and s
- Replies: 3
- Views: 583
Re: Energy Levels of d and s
First recall that subshells with higher “l” (the quantum number “l”) values have greater energy than subshells with lower “l” values. For example, the f orbital (l=3) has more energy than the d orbital (l=2). Electrons of higher orbitals are “less penetrating” (less likely to be found near the nucle...
- Fri Oct 02, 2015 11:20 am
- Forum: Properties of Light
- Topic: Momentum of Photons
- Replies: 1
- Views: 375
Momentum of Photons
How does a photon have momentum p (as in E=pc) if it has no rest mass?
Wouldn't momentum, p=mv=0?
Does that mean that photons have mass but the mass is so tiny it can be considered 0?
Wouldn't momentum, p=mv=0?
Does that mean that photons have mass but the mass is so tiny it can be considered 0?
- Wed Sep 30, 2015 12:51 am
- Forum: SI Units, Unit Conversions
- Topic: Units for Plank's Constant [ENDORSED]
- Replies: 3
- Views: 747
Units for Plank's Constant [ENDORSED]
Plank's constant sometimes uses the units "J-s" and other times "m^2 kg / s."
How does one become the other and which should we use for class?
Thanks!
How does one become the other and which should we use for class?
Thanks!
- Wed Sep 30, 2015 12:28 am
- Forum: Balancing Redox Reactions
- Topic: Identifying a Redox Reaction
- Replies: 1
- Views: 3303
Identifying a Redox Reaction
How does one quickly identify a reaction as redox?
Are there any giveaways to look for in the reaction?
Thanks in advance.
Are there any giveaways to look for in the reaction?
Thanks in advance.