## Search found 65 matches

Sun Mar 17, 2019 5:58 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Ecell
Replies: 5
Views: 358

### Re: Ecell

I belive it’s just one of them is more specific to 25 degrees Celsius (the second one)
Sun Mar 17, 2019 5:53 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: delta h and q
Replies: 3
Views: 547

### Re: delta h and q

Delta h is the heat transferred at constant pressure
Sun Mar 17, 2019 5:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatlier Principle
Replies: 10
Views: 1305

### Re: Le Chatlier Principle

I think because a catalyst speeds up the forward and back reaction to the same extent, adding a catalyst does not affect the relative rates of the two reactions
Sun Mar 17, 2019 8:44 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: DeltaU = 3/2 nRT
Replies: 3
Views: 341

### DeltaU = 3/2 nRT

under what conditions is delta U = 3/2 nRT ?
Fri Mar 15, 2019 11:28 am
Forum: Reaction Mechanisms, Reaction Profiles
Replies: 1
Views: 90

do we need to know the steady state approach for the final?
Thu Mar 14, 2019 1:00 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: comparing forward and reverse rates
Replies: 4
Views: 177

### Re: comparing forward and reverse rates

okay, I get now that the rate constants are different but the rates are the same...but doesn't the rate constant correspond to the rate of the reaction (larger rate constant --> faster rate of reaction)?
Thu Mar 14, 2019 12:02 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: comparing forward and reverse rates
Replies: 4
Views: 177

### comparing forward and reverse rates

I'm confused about how the forward and reverse rates of a reaction compare We know K = k1/k1prime aka K = forward rate constant/reverse rate constant So if K is large, the forward rate constant is larger which means the forward rate faster. BUT at equilibrium aren't the forward and reverse rates sup...
Thu Mar 14, 2019 11:47 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium approach
Replies: 3
Views: 140

### Re: Pre-Equilibrium approach

oh got it, thank you!
Thu Mar 14, 2019 11:38 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium approach
Replies: 3
Views: 140

### Pre-Equilibrium approach

is the pre-equilibrium approach only valid when there a fast step followed by a slow step (fast, slow)? Are there any other cases in which we would use the pre-equilibrium approach?
Wed Mar 13, 2019 7:06 pm
Forum: Second Order Reactions
Topic: Problem 15.35 (half life)
Replies: 1
Views: 99

### Problem 15.35 (half life)

given the half-life, how do we calculate the time needed for a certain amount of the reactant's concentration to decrease using the half-life equation for example : (problem 15.35) The half-life for the second-order reaction of a substance A is 50.5 s when [A] 0 = 0.84 mol/L. Calculate the time need...
Wed Mar 13, 2019 6:55 pm
Forum: Second Order Reactions
Topic: half-life
Replies: 4
Views: 148

### Re: half-life

Sarah Zhao 4C wrote:You can't multiply it by four but you can square it by four!
Break down the math:
1/2 x 4 = 2
vs
(1/2)^4 = 1/16

This doesn't give you the correct answer :( I think it's because, as someone said above, the half-life of a second-order reaction depends on how much reactant is left
Tue Mar 12, 2019 10:51 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 6th edition 15.19
Replies: 2
Views: 145

### Re: 6th edition 15.19

did you get the correct answer ( k = 2.85 x 10^12 L4mol-4s-1 ) when you did all your calculations in mmol and just converted to mol at the end?? because every time I do that I get the wrong answer (I keep getting k = 2.85 x 10^3
Tue Mar 12, 2019 10:29 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Answer to parts c and d of problem 15.19
Replies: 1
Views: 109

### Re: Answer to parts c and d of problem 15.19

the book's answer is in moles so you would have to divide your answer of k = 2.85 by 10^3 to get from mmol to mol. BUT that is still giving me the wrong answer because then I get k = 2.85 x 10^3 L4*mol-4*s-1, which still doesn't match the book's answer :(
Tue Mar 12, 2019 9:18 pm
Forum: General Rate Laws
Topic: rate of formation
Replies: 1
Views: 104

### rate of formation

are rate of formation and the unique rate the same thing?
Thu Feb 28, 2019 11:35 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta G = 0 ??
Replies: 5
Views: 802

### delta G = 0 ??

when is deltaG equal to zero
and when is deltaG standard equal to zero
Wed Feb 27, 2019 12:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Order in Cell Diagrams
Replies: 1
Views: 71

### Order in Cell Diagrams

when writing cell diagrams in which both species at the anode or cathode are aqueous solutions, does the order in which we write the aqueous solutions matter? For example in the reduction reaction Ce4+ + e- --> Ce3+ does: [anode] || Ce4+, Ce3+ | Pt mean somethingdifferent than: [anode] || Ce3+, Ce3+...
Wed Feb 27, 2019 12:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Order in Cell Diagrams
Replies: 3
Views: 168

### Order in Cell Diagrams

when writing cell diagrams in which both species at the anode or cathode are aqueous solutions, does the order in which we write the aqueous solutions matter? For example in the reduction reaction Ce4+ + e- --> Ce3+ does: [anode] || Ce4+, Ce3+ | Pt mean somethingdifferent than: [anode] || Ce3+, Ce3+...
Tue Feb 26, 2019 3:30 pm
Forum: Administrative Questions and Class Announcements
Replies: 179
Views: 12897

on electrochem worksheet #8d, does it matter if on the cell diagram NO is listed first or NO3 is listed first? Or can the order of these two be reversed and the diagram still denotes the same reaction
Wed Feb 13, 2019 10:54 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: DeltaS total
Replies: 2
Views: 79

### DeltaS total

under what conditions is delta S total or delta S of the universe equal to 0?
Thu Feb 07, 2019 10:16 pm
Forum: Administrative Questions and Class Announcements
Replies: 179
Views: 12897

For question 6 on worksheet 4, how exactly are we supposed to determine which volume we use to find the pressure for the work component of the internal energy change? To my understanding, the pressure was calculated using PV = nRT, with V = 998L, n = 31.9 mol, R = 0.08206 L * atm / mol * K, T = 311...
Thu Feb 07, 2019 12:07 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 8
Views: 427

### Midterm

will all of outline 4 be on the midterm? (including Gibbs Free Energy and the little part of Chapter 11 that is listed on the 6th edition outline) Or are will it be only up to section 9.11 in the sixth edition?
Wed Feb 06, 2019 11:16 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Ideal Gas Heat Capacity
Replies: 1
Views: 98

### Ideal Gas Heat Capacity

when calculating the heat released by a gas at constant pressure or volume, can we always assume it is an ideal gas unless specifically stated otherwise? (so then we can use Cp = (5/2)R and Cv = (3/2)R)
Sun Jan 27, 2019 9:10 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Replies: 4
Views: 182

### Re: Adiabatic and diathermic walls

I don’t think this factors into our calculations, it seems more like a conceptual thing to understand about different systems
Sun Jan 27, 2019 9:07 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U vs Delta H
Replies: 6
Views: 375

### Re: Delta U vs Delta H

Delta H is the change in enthalpy and delta U is the change in internal energy. Enthalpy is different from internal energy in that it is the amount of heat released or absorbed at a constant pressure. So enthalpy is a way of measuring a systems internal energy at a constant pressure. Delta H = delta...
Sun Jan 27, 2019 9:00 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Open, closed, and isolated
Replies: 1
Views: 92

### Re: Open, closed, and isolated

An open system can exchange both matter and energy with the surroundings. Examples of open systems are automobile engines and the human body. A closed system has a fixed amount of matter, but it can exchange energy with the surroundings. An example of a closed system is a cold pack used for treating...
Fri Jan 18, 2019 5:39 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Approximations
Replies: 4
Views: 171

### Re: Approximations

In a weak acid or base whose K is smaller than 10^-3, the amount of substance that dissociates is so small compared to the initial molarity that there isn't really a substantial difference between the initial and the initial minus the amount dissociated for example, we are saying because the amount ...
Fri Jan 18, 2019 5:34 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: percentage protonation
Replies: 2
Views: 128

### Re: percentage protonation

Weak acids and bases do not fully dissociate as strong acids and bases do. Percentage protonation/deprotonation tells us how much of the acid or base has dissociated. Percentage protonation tells you the percent of a base that has dissociated. In other words, its the percent of the base that has acc...
Fri Jan 18, 2019 5:19 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ignoring solids
Replies: 6
Views: 314

### Re: ignoring solids

The concentration of solids and liquids essentially remains constant throughout the reaction so we don't include them in K or Q expressions.
Sun Jan 13, 2019 10:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Catalysts [ENDORSED]
Replies: 3
Views: 130

### Re: Catalysts[ENDORSED]

Catalysts only speed up the time it takes for the reaction to reach equilibrium, but it does not change the equilibrium position and it does not change K.
Sun Jan 13, 2019 9:57 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Solids and Liquids with the Reaction Quotient
Replies: 3
Views: 184

### Re: Solids and Liquids with the Reaction Quotient

no, solids and liquids are not included in Q for the same reasons they aren't included in K (their concentration does not change or changes so little it is insignificant). Ultimately, Q and K are both calculated in the exact same way, only the numbers themselves are different because in the case of ...
Tue Jan 08, 2019 3:14 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Spontaneous reaction
Replies: 4
Views: 167

### Spontaneous reaction

what does it mean to say a reaction is spontaneous?
Fri Dec 07, 2018 8:49 pm
Forum: Administrative Questions and Class Announcements
Topic: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]
Replies: 118
Views: 11384

### Re: FINAL PRACTICE - Lyndon's Churro Review Session[ENDORSED]

Michelle Ramirez_4A wrote:Can someone explain why hemogrlobin is tetradentrate but cisplatin is monodentrate?

hemoglobin and cisplatin are not ligands, so they aren't any kind of "dentate." We only describe ligands as being bidentate, tridentate, etc.
Fri Dec 07, 2018 11:50 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone pairs & dipoles
Replies: 1
Views: 73

### Lone pairs & dipoles

do lone pairs directly cause a dipole moment? or do they only affect the shape of the molecule which can affect the dipole moment?
Fri Dec 07, 2018 11:46 am
Forum: Determining Molecular Shape (VSEPR)
Topic: ClO2- lewis structure
Replies: 4
Views: 310

### ClO2- lewis structure

does the lewis structure of ClO2- have doubles bonds or only single bonds? because to minimize formal charge, there should be one double bond between one Cl and the O, but I've heard Cl doesn't form double bonds??
Sun Dec 02, 2018 11:33 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted v. Lewis v. Arrhenius
Replies: 4
Views: 282

### Re: Bronsted v. Lewis v. Arrhenius

also, the Lewis definition encompasses more compounds/is more general than the Bronsted and Arrhenius definitions
Sun Dec 02, 2018 11:23 pm
Forum: Bronsted Acids & Bases
Topic: Transition Metals
Replies: 3
Views: 157

### Re: Transition Metals

the book also shows them written in reverse so I'm assuming that is the "correct" way to write them and that we'd have to write them like that on the test too
Sat Dec 01, 2018 10:13 pm
Forum: Biological Examples
Topic: Final Material
Replies: 2
Views: 173

### Re: Final Material

I'm not sure to what extent we need to know it, but the syllabus outline says we need to know the biological significance of coordination compounds and the final covers the whole syllabus
Wed Nov 28, 2018 11:48 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone pairs on octahedral electron density
Replies: 3
Views: 190

### Lone pairs on octahedral electron density

For all of the other VSEPR models, replacing an atom with a lone pair is done by taking away from the equatorial plane. But with the octahedral shape, an axial bond is replaced to form square pyramidal. Why is that so?
Sun Nov 25, 2018 9:56 pm
Forum: Lewis Structures
Topic: Exceptions to the Octet Rule
Replies: 5
Views: 234

### Re: Exceptions to the Octet Rule

H, He, Li, Be, and B can have less than an octet (an incomplete octet)
and any element in period 3 or below can have more than an octet (expanded octet) because they can use the empty d orbital, as mentioned above.
Sun Nov 25, 2018 9:53 pm
Forum: Hybridization
Topic: promoted hybridization
Replies: 4
Views: 186

### Re: promoted hybridization

When an electron is promoted it is relocated to a higher energy orbital. Although it takes energy to promote electron, it eventually results in bonding and a more stable molecule. (this is why promotion will only take place if the overall change is towards lower energy). Promotion happens in carbon ...
Sun Nov 25, 2018 9:44 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar vs Nonpolar
Replies: 5
Views: 168

### Re: Polar vs Nonpolar

you have to determine the shape of the molecule and look at whether or not the molecule has one side of the molecule that has a negative/positive dipole. A polar bond between two atoms creates a dipole moment in which one atom has a slightly more positive/negative charge. Depending on how these pola...
Sun Nov 18, 2018 2:44 pm
Forum: Hybridization
Topic: sp3 hybridization
Replies: 6
Views: 212

### Re: sp3 hybridization

What is the hybridization of the central atom in a molecule with trigonal pyramidal shape?
Sun Nov 18, 2018 2:34 pm
Forum: Hybridization
Topic: sp3 hybridization
Replies: 6
Views: 212

### sp3 hybridization

does the central atom of a molecule with a tetrahedral shape always have sp3 hybridization?
Sun Nov 18, 2018 2:01 pm
Forum: Sigma & Pi Bonds
Topic: Differences in energy
Replies: 5
Views: 256

### Re: Differences in energy

the shorter the bond, the stronger it is. And triple bonds are shorter than double bonds which are shorter than single bonds. (triple < double < single) And anything more than a single bond has at least one pi bond. (for example, a triple bond is 1 sigma and 2 pi bonds) So I guess you could say the ...
Sun Nov 11, 2018 6:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs
Replies: 7
Views: 301

### Re: Lone Pairs

only the lone pairs around the central atom affect the shape of the molecule (For example the lone pairs of chlorine on CCL4 would not affect the molecules shape)
Sun Nov 11, 2018 6:16 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Atom Distance, repulsion?
Replies: 6
Views: 410

### Re: Atom Distance, repulsion?

electron repulsion affects the overall shape of the molecule because it determines how far the bonds around the central atom are from each other. Lone pairs of electrons have stronger repulsion strength than bonding pairs .
Sun Nov 11, 2018 6:08 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Boiling point
Replies: 12
Views: 668

### Re: Boiling point

I think organic compounds are generally rod-shaped. Also, the way the formula is written generally gives you an idea of whether it is rod/sphere shaped. For example, in Lavelle's lecture, he mentioned the examples C4H10 and CH3CH2CH2CH3. These both have the same number of each atom but the latter is...
Sun Nov 11, 2018 6:01 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Graphical Representation of Orbitals
Replies: 2
Views: 334

### Re: Graphical Representation of Orbitals

the graphical representations are the probability distributions
Sun Nov 11, 2018 5:58 pm
Forum: Bond Lengths & Energies
Topic: Interaction Potential Energies
Replies: 1
Views: 54

### Re: Interaction Potential Energies

I believe it's representative of how strongly attracted two atoms are. it's affected by "r" (the distance between the atoms) because as the distance between them increases, they are less attracted to each other. And as the distance decreases, aka they are closer, they are more strongly att...
Sun Nov 04, 2018 8:46 pm
Forum: Octet Exceptions
Replies: 16
Views: 917

you put one dot on the element that has the radical
Sun Nov 04, 2018 8:27 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charges in charged molecules
Replies: 5
Views: 130

### Re: Formal charges in charged molecules

the negative formal charge usually is on the element that is most electronegative
Sun Nov 04, 2018 8:26 pm
Forum: Electronegativity
Topic: Electronegativity Relations
Replies: 2
Views: 56

### Re: Electronegativity Relations

electronegativity is value that is calculated using the measured values of electron affinity and ionization energy. and electron affinity is the energy released when an electron is added to an atom and ionization energy is the energy required to remove an electron from an atom in its gaseous state T...
Sun Nov 04, 2018 8:25 pm
Forum: Electronegativity
Topic: Electronegativity Relations
Replies: 2
Views: 56

### Re: Electronegativity Relations

electronegativity is value that is calculated using the measured values of electron affinity and ionization energy. and electron affinity is the energy released when an electron is added to an atom and ionization energy is the energy required to remove an electron from an atom in its gaseous state T...
Sun Oct 28, 2018 9:42 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum numbers for the "exception" cases
Replies: 15
Views: 1010

### Re: Quantum numbers for the "exception" cases

ohhh got it. thanks!
Wed Oct 24, 2018 4:44 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum numbers for the "exception" cases
Replies: 15
Views: 1010

### Re: Quantum numbers for the "exception" cases

Right thanks, but I meant in terms of writing the quantum numbers... wouldn't these two atoms have the same quantum numbers (n = 4, l = 0)

or do we write copper as : n= 3, l = 2, ml = +2
Wed Oct 24, 2018 2:12 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum numbers for the "exception" cases
Replies: 15
Views: 1010

### Quantum numbers for the "exception" cases

I'm confused about how we would write the quantum numbers for something like Copper (Cu) whose electron configuration is [Ar] 3d^10 4s^1
How would we differentiate this quantum number from that of Potassium (K) whose electron configuration is [Ar] 4s^1
Sun Oct 21, 2018 9:48 pm
Forum: Quantum Numbers and The H-Atom
Topic: Difference between ground and excited state of electrons
Replies: 4
Views: 222

### Re: Difference between ground and excited state of electrons

an excited electron will be in a higher energy level than it "should"/would normally be in
Sun Oct 21, 2018 9:46 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: S,P,D,F
Replies: 6
Views: 2417

### Re: S,P,D,F

not every orbital has a p(), the magnetic quantum number tells you the orientation in a subshell (s,p,d,f). for p it is Px Py Pz. for d it is Dyz, Dxz, Dxy,
Dx^2-y^2, Dz^2
Sun Oct 21, 2018 9:32 pm
Forum: Photoelectric Effect
Topic: Visible Light Spectrum
Replies: 6
Views: 240

### Re: Visible Light Spectrum

yeah pretty much. Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers
Fri Oct 12, 2018 9:24 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Extensive vs. Intensive
Replies: 2
Views: 217

### Extensive vs. Intensive

Can someone give me some examples of extensive and intensive properties that aren't in the notes?
Fri Oct 12, 2018 9:13 am
Forum: Properties of Light
Replies: 4
Views: 215

### Re: Explaining answer for 1.3

when the frequency of the wave decreases, the wavelength is longer so waves broaden (spread out) and the extent of the change (aka the slope of the wave) decreases
Fri Oct 12, 2018 9:08 am
Forum: Properties of Light
Topic: Hz to S-1
Replies: 4
Views: 159

### Re: Hz to S-1

One Hz is equivalent to one cycle per second
Fri Oct 05, 2018 1:40 am
Forum: Limiting Reactant Calculations
Topic: Mass of products/Reactants [ENDORSED]
Replies: 3
Views: 116

### Re: Mass of products/Reactants[ENDORSED]

The law of conservation of mass states that matter is neither created or destroyed (with the sole exception of nuclear reactions). So as long as we are dealing with chemical reactions, the mass on the reactants side before the reaction must be the same as the mass on the products side after the reac...
Fri Oct 05, 2018 1:32 am
Forum: Limiting Reactant Calculations
Topic: multiple limiting reactants
Replies: 9
Views: 388

### Re: multiple limiting reactants

I remember coming across this in the online module and the answer given as correct was: no, it is highly unlikely that 2 reactants are both present in limiting molar amounts.
Fri Oct 05, 2018 1:25 am
Forum: Limiting Reactant Calculations
Topic: Limiting Reactant
Replies: 8
Views: 728

### Re: Limiting Reactant

Instead of calculating each possible theoretical yield, you can also just calculate the moles of each given substance and compare it to the number of moles in the balanced equation. The substance with the smallest ratio of [moles you have/coefficient in the balanced chemical equation] is the limitin...