Search found 35 matches

by Joanna Su 2L
Tue Mar 08, 2016 6:35 pm
Forum: *Alkenes
Topic: Alkenes as functional groups
Replies: 1
Views: 425

Alkenes as functional groups

Should we consider alkenes and alkynes as functional groups? On one of the previous finals an alkene was listed as a functional group but I remember Dr. Lavelle mentioning that they're not true functional groups.
by Joanna Su 2L
Mon Mar 07, 2016 5:00 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Cyclobutane
Replies: 1
Views: 373

Re: Cyclobutane

Cyclobutane only has hydrogens attached to the carbons which are not large enough to create steric strain. It does have torsional strain when the ring is planar because the bonds are eclipsed.
by Joanna Su 2L
Mon Mar 07, 2016 4:56 pm
Forum: *Amines
Topic: Amines
Replies: 1
Views: 659

Re: Amines

N indicates that the substituents are attached to nitrogen instead of a carbon. Since all of the substituents are attached to nitrogen, they are labeled N instead of a number.
by Joanna Su 2L
Mon Mar 07, 2016 1:48 am
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: Eclipsed form and strain
Replies: 1
Views: 434

Re: Eclipsed form and strain

The eclipsed form will always have torsional strain and therefore be less favorable than the staggered conformation.
by Joanna Su 2L
Mon Feb 29, 2016 5:41 pm
Forum: *Electrophilic Addition
Topic: Free Energy Reaction Profile
Replies: 1
Views: 378

Free Energy Reaction Profile

When noting the change in Gibbs free energy for the second transition state, should we label it as the difference between the transition state and the reactant or the transition state and the intermediates? The textbook uses both in chapter 4 (figures 4.3 and 4.4 on p157).
by Joanna Su 2L
Mon Feb 29, 2016 5:23 pm
Forum: *Nucleophilic Substitution
Topic: SN2 Reactions
Replies: 4
Views: 1353

Re: SN2 Reactions

SN2 reactions are always one step reactions. There are no intermediates. As the hydroxide attacks bromomethane, the Br-C bonds starts to break. This would give a transition state with Br-C partially broken and C-OH partially formed.
by Joanna Su 2L
Tue Feb 23, 2016 1:16 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Unbranched vs. Branched Structural Formulas
Replies: 1
Views: 2345

Re: Unbranched vs. Branched Structural Formulas

Unbranched structures consist of a single carbon chain. Branched structures have a substituent such as a methyl group that is attached to a carbon on the chain.
by Joanna Su 2L
Tue Feb 16, 2016 4:43 pm
Forum: First Order Reactions
Topic: Winter 2015 Quiz Prep #11
Replies: 1
Views: 413

Re: Winter 2015 Quiz Prep #11

You would have to use the Arrhenius equation ln(k2/k1)=Ea/R(1/T1-1/T2). Solve for Ea/R first then use it to find k for 770K.
by Joanna Su 2L
Mon Feb 15, 2016 1:33 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: reactant intermediate
Replies: 1
Views: 480

Re: reactant intermediate

Intermediates are produced in one elementary step then used up in a later one. They do not show up on the overall reaction.
by Joanna Su 2L
Wed Feb 10, 2016 12:42 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm Question 2013 Q6A
Replies: 2
Views: 484

Re: Midterm Question 2013 Q6A

ΔS total is not the same as ΔS system found in the Gibbs free energy equation. ΔS total = ΔS sys + ΔS surroundings . ΔG=ΔH-TΔS If you divide both sides by T, you'll end up with: ΔG/T=ΔH sys /T - ΔS sys Since q sys =-q surr and under constant pressure ΔH sys =-ΔH surr , ΔS surr = -ΔH syst /T Take the...
by Joanna Su 2L
Wed Feb 10, 2016 12:31 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Winter 2014 Midterm #8
Replies: 1
Views: 425

Re: Winter 2014 Midterm #8

In this particular question, we want to solve for Ka which is the acid dissociation constant. This means that we would want HF--> H + + F - which is the reaction for the dissociation of hydrofluoric acid. Typically, in a galvanic cell, we would want a spontaneous reaction which has a positive E°cell...
by Joanna Su 2L
Sun Feb 07, 2016 1:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15C Why is KOH included in the galvanic cell?
Replies: 1
Views: 427

14.15C Why is KOH included in the galvanic cell?

For the reaction Cd(s)+2Ni(OH) 3 (s)-->Cd(OH) 2 (s)+2Ni(OH) 2 (s), the half reactions are: Cd(OH) 2 + 2e - -->Cd + 2OH - Ni(OH) 3 + e - --> Ni(OH) 2 +OH - The solutions manual says that the cell diagram is Cd(s)|Cd(OH) 2 (s)|KOH(aq)||Ni(OH) 2 (s)|Ni(s) Why is KOH included in the cell diagram?
by Joanna Su 2L
Mon Feb 01, 2016 6:04 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Textbook Problem 11.19a
Replies: 1
Views: 296

Re: Textbook Problem 11.19a

Gibbs free energy for H2 and O2 are both 0kJ/mol.
by Joanna Su 2L
Mon Feb 01, 2016 12:47 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy Ideal Gas
Replies: 1
Views: 320

Re: Entropy Ideal Gas

Entropy increases as the complexity of a molecule increases. More atoms means that there are more vibrations and rotational positions possible. Therefore, a diatomic molecule would have a higher entropy than a monatomic one.
by Joanna Su 2L
Tue Jan 26, 2016 3:56 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Units
Replies: 2
Views: 500

Re: Entropy Units

Since moles to gram and Celsius to Kelvin do not have a one to one ratio, 15J/molK is not the same as 15J/gC. You could probably solve for entropy in terms of J/gC but depending on what the molecule is J/molK would be different.
by Joanna Su 2L
Tue Jan 19, 2016 5:12 pm
Forum: Phase Changes & Related Calculations
Topic: Quiz 1 Prep Winter 2014 #4
Replies: 2
Views: 519

Re: Quiz 1 Prep Winter 2014 #4

Looking at the final reaction, you know that D has to be on the reactants side. The only equation that has D is the second equation. Since D is on the products side, you would need to flip the reaction. However, that leaves you with 3A when you add up the reaction. To get 2A, you can halve the first...
by Joanna Su 2L
Tue Jan 19, 2016 4:48 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Perfect System
Replies: 3
Views: 618

Re: Perfect System

qsystem is negative if heat was released. In this case, qsurroundings would be positive because it absorbs the heat that was lost from the system. If the system absorbed heat from the surroundings, qsystem would be positive and qsurroundings would be negative.
by Joanna Su 2L
Tue Jan 19, 2016 4:43 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: HW 8.45: forming carbon disulfide
Replies: 1
Views: 310

Re: HW 8.45: forming carbon disulfide

In the overall reaction, 4 moles of carbon are used and 4 moles of carbon disulfide are produced. So ΔH is really 358.8kJ for every 4 moles of C, 358.8kJ for every mole of S 8 , and 358.8kJ for every 4 moles of CS 2 . For part b, you would have to find ΔH per mole of C and then multiply it by the mo...
by Joanna Su 2L
Tue Jan 19, 2016 4:34 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Quick Question About Isothermal Reactions
Replies: 1
Views: 309

Re: Quick Question About Isothermal Reactions

A reversible reaction is one that can be reversed by an infinitely small change. For example when the external pressure is decreased infinitesimally, the piston moves out. On the other hand, an irreversible reaction is one where there is a measurable change and infinitesimally small changes in exter...
by Joanna Su 2L
Mon Jan 18, 2016 5:34 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: When is change in internal energy 0?
Replies: 1
Views: 344

Re: When is change in internal energy 0?

Change in internal energy is 0 when there is no heat transfer and there is no work done on or by the system.
by Joanna Su 2L
Mon Jan 18, 2016 5:31 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Question 8.49
Replies: 1
Views: 313

Re: Question 8.49

Unless it is specifically mentioned, we can assume the temperature is 25 degrees Celsius or 298K.
by Joanna Su 2L
Mon Jan 11, 2016 4:11 pm
Forum: Phase Changes & Related Calculations
Topic: Hess's Law
Replies: 3
Views: 573

Re: Hess's Law

All state functions are additive. Because enthalpy is a state function, it is also additive.
by Joanna Su 2L
Fri Jan 08, 2016 5:43 pm
Forum: Phase Changes & Related Calculations
Topic: Celsius to Kelvin conversion
Replies: 2
Views: 723

Re: Celsius to Kelvin conversion

Change in degrees Celsius is always the same as change in Kelvin. To convert temperature from Celsius to Kelvin, you add 273.15. For example, 0°C = 273.15K.
20°C = 293.15K
100°C = 373.15K
Thus, the change in temperature from 20°C to 100°C or from 293.15K to 373.15K is 80K
by Joanna Su 2L
Fri Jan 08, 2016 5:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpies of Formation H.W. 8.65
Replies: 1
Views: 503

Re: Standard Enthalpies of Formation H.W. 8.65

ΔH° (enthalpy of the reaction) is different from ΔH° f (enthalpy of formation). When you add the two reactions, what you end up with is the enthalpy of the reaction 2NO(g) +3/2O 2 (g)-->N 2 O 5 (g), not the enthalpy of formation of N 2 O 5 (g). In order to find the enthalpy of formation of N 2 O 5 (...
by Joanna Su 2L
Mon Nov 30, 2015 4:31 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HIO vs HIO3 Acid Strength
Replies: 1
Views: 7802

Re: HIO vs HIO3 Acid Strength

Because oxygen is a highly electronegative atom, it pulls electron density towards itself and away from iodine. The more oxygen atoms there are, the more spread out the negative charge is on the conjugate base. And the more spread out the charge is, the more stable the base is. This makes the acid a...
by Joanna Su 2L
Wed Nov 25, 2015 3:15 pm
Forum: Bronsted Acids & Bases
Topic: Strong/weak acids and bases
Replies: 1
Views: 538

Re: Strong/weak acids and bases

If there is a double-headed arrow, the acid or base is most likely a weak one. If the arrow only points in one direction, it is most likely a strong acid or strong base because it will dissociate completely. Strong acids include HCl, HBr, HI, H2SO4, HNO3, HClO4, and HClO3. Strong bases include NaOH,...
by Joanna Su 2L
Mon Nov 16, 2015 7:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solving for Equilibrium Constant Kp (HW11.89b)
Replies: 2
Views: 373

Re: Solving for Equilibrium Constant Kp (HW11.89b)

Do the units for pressure always have to be converted to bar? Or are there some cases where equilibrium constants can be calculated from values of different units such as Pascal or atmosphere?
by Joanna Su 2L
Mon Nov 16, 2015 4:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solving for Equilibrium Constant Kp (HW11.89b)
Replies: 2
Views: 373

Solving for Equilibrium Constant Kp (HW11.89b)

HW 11.89B The chemical equation is 2A(g) --> B(g) + 2C(g). At equilibrium, A is 18kPa, B is 5 kPa, C is 10 kPa. In the solutions manual, when solving for the equilibrium constant, the values for pressure are all divided by 100. Kp=(5/100)(10/100)^2/(18/100)^2. Why is this so?
by Joanna Su 2L
Tue Nov 10, 2015 12:12 am
Forum: Naming
Topic: Coordination Compound Nomenclature Order
Replies: 1
Views: 355

Coordination Compound Nomenclature Order

When writing out the formula for coordination compounds, does the order of the ligands matter? For example, can pentaamminesulfatocobalt(III) chloride be written as [Co(NH3)5(SO4)]Cl and [Co(SO4)(NH3)5]Cl? Or does the formula have to be written in the same order as it is named?
by Joanna Su 2L
Tue Nov 03, 2015 9:28 pm
Forum: Resonance Structures
Topic: Octet with Formal Charge vs Expanded Octet Stability
Replies: 1
Views: 603

Octet with Formal Charge vs Expanded Octet Stability

Are Lewis structures with an expanded octet more stable (lower in energy) than structures with an octet and formal charges? The course reader states that structures with an expanded octet are lower in energy. However, some of the problems in past midterms state that structures with octets are more s...
by Joanna Su 2L
Wed Oct 28, 2015 7:45 pm
Forum: Lewis Structures
Topic: calculated number of valence e- does not match
Replies: 2
Views: 454

Re: calculated number of valence e- does not match

There are two lone pairs that are not shown on each oxygen atom. (8 electrons are not shown.) If you take into account those valence electrons, there will be a total of 40.
by Joanna Su 2L
Wed Oct 21, 2015 4:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity and electronegativity
Replies: 2
Views: 388

Re: Polarity and electronegativity

Electronegativity measures the power of an atom to pull electrons towards itself. The values for electronegativity are predetermined so you would have to look it up. But in general, electronegativity increases as you go from the bottom to the top of a group and from left to right across a period. As...
by Joanna Su 2L
Thu Oct 15, 2015 3:15 pm
Forum: SI Units, Unit Conversions
Topic: Convert eV to J [ENDORSED]
Replies: 2
Views: 739

Re: Convert eV to J [ENDORSED]

1 eV = 1.602 x 10^-19 J
The conversion is on the back of the periodic table that was provided with the course reader.
by Joanna Su 2L
Wed Oct 07, 2015 11:28 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Quantum Number
Replies: 2
Views: 811

Re: Magnetic Quantum Number

There is no specific orbital (or orientation) that is indicated by the magnetic quantum number. However, you can assign an orbital to the numbers. For example, if you have a p subshell, the possible magnetic quantum numbers include +1, 0, and -1. You could then say px is +1, py is 0, and pz is -1. O...
by Joanna Su 2L
Fri Oct 02, 2015 7:44 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Momentum of a Photon
Replies: 1
Views: 380

Re: Momentum of a Photon

The momentum can be calculated through the formula, E = p x v, where p is momentum, v is velocity and E is energy. In the case of photons, v equals to the speed of light (c = 3 x 10^8 m/s). You can then rearrange the equation to solve for p (p = E/v).

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