## Search found 65 matches

Fri Mar 15, 2019 1:00 am
Forum: General Rate Laws
Topic: Q 15.29 6th edition
Replies: 1
Views: 104

### Q 15.29 6th edition

For the first-order reaction A --> 3 B + C, when [A]0 = 0.015 mol/L, the concentration of B increases to 0.018 mol/L in 3.0 min. (a) What is the rate constant for the reaction expressed as the rate of loss of A? (b) How much more time would be needed for the concentration of B to increase to 0.030 m...
Mon Mar 11, 2019 11:57 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: 96

### Electrolysis

Did Lavelle go over the formula Q=It and the electrolysis process in detail? Some of the questions given as practice from the textbook talk about overpotential, did he teach it?
Sun Mar 10, 2019 3:38 pm
Forum: Balancing Redox Reactions
Topic: Question from textbook
Replies: 3
Views: 103

### Question from textbook

6th edition 14.5 (d)
How would you balance the following reaction in a basic medium -
P4 (s) ----> H2PO2 ^- (aq) + PH3 (g)
Thu Mar 07, 2019 11:35 am
Forum: General Rate Laws
Topic: Deriving rate laws
Replies: 2
Views: 138

### Deriving rate laws

Do we need to know how to derive the rate laws?
Mon Mar 04, 2019 9:43 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test #2
Replies: 2
Views: 162

### Test #2

If anyone has got their test back, could you please solve the question about deprotonation of H2O? Or if you remember how you did it, please answer.
Mon Mar 04, 2019 9:41 am
Forum: First Order Reactions
Topic: Homework #15.29
Replies: 1
Views: 112

### Re: Homework #15.29

(a) Since it is a first-order reaction, the rate constant k=[A]^1 and in terms of loss of A, you can just put a negative sign and say that it is decreasing.

Mon Mar 04, 2019 9:34 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: The Nernst equation
Replies: 2
Views: 152

### Re: The Nernst equation

Yep, the temperature is always in Kelvin.
Sat Feb 23, 2019 5:03 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Stability
Replies: 2
Views: 92

### Re: Stability

You can look at it this way - If a compound has more energy, its constituent atoms will have more energy. This energy will allow atoms to move around or break apart from each other thus making the compound unstable. Think of this situation as a kid who is hyped up on sugar, he or she will not sit qu...
Sat Feb 23, 2019 4:59 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: writing reaction for CO(g)
Replies: 1
Views: 85

### Re: writing reaction for CO(g)

I think this is because carbon is naturally found as graphite which is a solid.
Sat Feb 23, 2019 4:57 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: test 3
Replies: 10
Views: 369

### Re: test 3

Everything beginning from Gibbs free energy up to Friday's lecture which covered cell potential, electric work, and free energy.
Sat Feb 23, 2019 4:55 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Homework
Replies: 3
Views: 133

### Re: Homework

yes, there is homework due every week unless mentioned by your TA or Dr. Lavelle.
Tue Feb 12, 2019 2:44 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: 6th edition 8.25
Replies: 4
Views: 2807

### 6th edition 8.25

A constant-volume calorimeter was calibrated by carrying out a reaction known to release 3.50 kJ of heat in 0.200 L of solution in the calorimeter (q =-3.50 kJ), resulting in a temperature rise of 7.32 C. In a subsequent experiment, 100.0 mL of 0.200 m HBr(aq) and 100.0 mL of 0.200 m KOH(aq) were mi...
Tue Feb 12, 2019 1:29 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Irreversible vs Reversible
Replies: 3
Views: 135

### Irreversible vs Reversible

Which one occurs at constant pressure - reversible or irreversible expansion?
Tue Feb 12, 2019 1:27 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Calorimeter - Type of System
Replies: 5
Views: 502

### Re: Calorimeter - Type of System

A calorimeter is an isolated system so change in internal energy is always zero because neither there is a change in heat (q=0) nor there is any change in volume (w=0).
Thu Feb 07, 2019 10:04 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv,m and CP,m
Replies: 3
Views: 255

### Re: Cv,m and CP,m

C v,m signifies the specific heat capacity of a gas at constant volume per mole, and C p,m signifies the same for constant pressure per mole.
Thu Feb 07, 2019 10:01 am
Forum: Phase Changes & Related Calculations
Topic: Solids and Liquids
Replies: 5
Views: 174

### Re: Solids and Liquids

Because solids and liquids can be called 'incompressible'. It means that their volume varies very little or not at all with change in pressure.
Thu Feb 07, 2019 10:00 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Textbook Question
Replies: 1
Views: 122

### Textbook Question

Calculate the heat released by 5.025 g of Kr(g) at 0.400 atm as it cools from 97.6 C to 25.0 C at
(a) constant pressure and
(b) constant volume. Assume that krypton behaves as an ideal gas.

Fri Feb 01, 2019 3:37 pm
Forum: Calculating Work of Expansion
Topic: formula for work with integral
Replies: 3
Views: 125

### Re: formula for work with integral

I am assuming that we will have to use that in solving questions because he posted a document with rules of differentiation on his website.
Fri Feb 01, 2019 3:34 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Determining Internal Energy
Replies: 3
Views: 147

### Re: Determining Internal Energy

The negative sign indicates that work is being done by the system, i.e. it is releasing energy.
Fri Feb 01, 2019 3:32 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Enthalpy
Replies: 3
Views: 167

### Enthalpy

Is enthalpy calculated only for reactions at constant pressure?
Fri Feb 01, 2019 2:00 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated Systems
Replies: 6
Views: 229

### Re: Isolated Systems

I don't think that any system except the universe is 100% isolated. But examples of an isolated system can be water in an insulated bottle.
Fri Jan 25, 2019 5:19 pm
Forum: Phase Changes & Related Calculations
Topic: Modules
Replies: 17
Views: 438

### Modules

Are the modules on Dr. Lavelle's website compulsory?
Fri Jan 25, 2019 5:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Accurate and estimation of bond enthalpy
Replies: 3
Views: 137

### Re: Accurate and estimation of bond enthalpy

a diatomic molecule is a molecule like N2, O2, HCl, which has only 2 elements.
Fri Jan 25, 2019 3:16 pm
Forum: Phase Changes & Related Calculations
Topic: Lecture 1/23
Replies: 3
Views: 151

### Re: Lecture 1/23

hello, he started thermochemistry and introduced enthalpy. he said that enthalpy is a state property meaning that it does not depend on the path taken but only on the initial condition. he also talked about enthalpies of fusion (solid -> liquid), sublimation (solid -> gas), and vaporization (liquid ...
Tue Jan 22, 2019 12:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 6th edition question from book
Replies: 1
Views: 112

### 6th edition question from book

Consider the equilibrium 3 NH3(g) + 5 O2(g) (equilibrium sign) 4 NO(g) + 6 H2O(g). (a) What happens to the partial pressure of NH3 when the partial pressure of NO is increased? (b) Does the partial pressure of O2 decrease when the partial pressure of NH3 is decreased? Can someone please help me with...
Thu Jan 17, 2019 5:43 pm
Forum: Ideal Gases
Topic: Partial Pressure for Gases [ENDORSED]
Replies: 2
Views: 177

### Re: Partial Pressure for Gases[ENDORSED]

Not always. Sometimes decreasing the volume causes the pressure to increase since both of them are inversely proportional to each other.
Thu Jan 17, 2019 4:08 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: relationship between Ka, Kb, and its ability to donate
Replies: 3
Views: 118

### Re: relationship between Ka, Kb, and its ability to donate

So if you are given a pKa value of a conjugate acid which is large, does that mean the base is strong?
Thu Jan 17, 2019 4:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Question
Replies: 2
Views: 74

### Textbook Question

(a) A sample of 2.0 mmol Cl2(g) was sealed into a 2.0-L reaction vessel and heated to 1000. K to study its dissociation into Cl atoms. Use the information in Table 11.2 to calculate the equilibrium composition of the mixture. (b) If 2.0 mmol F2 was placed into the reaction vessel instead of the chlo...
Fri Jan 11, 2019 8:00 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium constants for ionic compounds
Replies: 1
Views: 32

### Re: Equilibrium constants for ionic compounds

I am not completely sure, but if the ions are in their aqueous states as products you just include them as you would include any compound or molecule in the equation for K.
Fri Jan 11, 2019 7:58 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Thermodynamics
Replies: 1
Views: 37

### Re: Thermodynamics

It equals to -RT ln K. So If Gr is negative, then ln K must be positive and therefore K > 1; products are favored at equilibrium.
If Gr is positive, then ln K must be negative and therefore K < 1; reactants are favored at equilibrium.
Fri Jan 11, 2019 7:53 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: vant Hoff factor and equation
Replies: 3
Views: 46

### vant Hoff factor and equation

While reading the textbook I came across the vant Hoff equation and it seems really confusing. How important is it for this course?
Fri Jan 11, 2019 7:51 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q 11.47
Replies: 3
Views: 163

### Q 11.47

For the reaction PCl5(g) (equilibrium arrow) PCl3(g) + Cl2(g), Kc = 1.1 X 10^-2 at 400. K. (a) Given that 1.0 g of PCl5 is placed in a 250.-mL reaction vessel, determine the molar concentrations in the mixture at equilibrium. (b) What percentage of the PCl5 has decomposed at equilibrium at 400. K? C...
Sat Dec 08, 2018 2:40 pm
Forum: Empirical & Molecular Formulas
Topic: Mols to atoms
Replies: 1
Views: 350

### Mols to atoms

If I have 6 mols of Cl in a molecule, how many atoms does that convert to? Do we multiply 6 by Avogadro's number?
Fri Dec 07, 2018 12:48 am
Forum: Naming
Topic: Chloro v/s chlorido
Replies: 6
Views: 241

### Chloro v/s chlorido

When do we use chloro and chlorido? What is the difference between the two
Fri Dec 07, 2018 12:46 am
Forum: Naming
Topic: Naming of compounds with multiple ligands
Replies: 1
Views: 119

### Re: Naming of compounds with multiple ligands

Naming is always done in an alphabetical order irrespective of the formula. It doesn't matter how we write the formula.
Fri Dec 07, 2018 12:42 am
Forum: Dipole Moments
Topic: Interaction Potential Energy
Replies: 4
Views: 430

### Re: Interaction Potential Energy

Are we supposed to do any calculations related to the formula Ep is directly proportional to polarizability1 times polarizability2 divided by r^6?
Wed Dec 05, 2018 2:30 pm
Forum: Conjugate Acids & Bases
Topic: Conjugate acid base example from class
Replies: 2
Views: 125

### Conjugate acid base example from class

CH3CO2^- + H2O ---> OH^- + CH3CO2H

Which one is the conjugate acid-base pair?
Mon Nov 26, 2018 10:28 pm
Forum: Hybridization
Topic: Question from textbook
Replies: 4
Views: 186

### Question from textbook

Why is BrF3 sp3d hybridized?
Mon Nov 26, 2018 12:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Curve
Replies: 5
Views: 357

### Re: Curve

So does it use a straight grading scale? Like top 3% get a + and bottom 3% get a - grade in whichever zone they fall into?
Mon Nov 26, 2018 12:27 pm
Forum: Administrative Questions and Class Announcements
Replies: 135
Views: 31319

Is there any worksheet for test 3?
Mon Nov 26, 2018 12:26 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability
Replies: 4
Views: 225

### Polarizability

What is the trend of polarizing power for cations and anions?
Sat Nov 17, 2018 9:30 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Shielding effect
Replies: 6
Views: 373

### Re: Shielding effect

Shielding effect is when electrons in the shells closer to the nucleus block the effect of the protons in the nucleus on other electrons in the outer shells.
Sat Nov 17, 2018 8:08 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: electron distortion
Replies: 4
Views: 225

### Re: electron distortion

Because of repulsion between the electrons in the given atoms.
Sat Nov 17, 2018 8:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular shape
Replies: 2
Views: 125

### Re: Molecular shape

Because the shape of a molecule is the arrangement of atoms in a manner that each experiences the least amount of repulsion. Hence, if repulsion is less, the strength is more.
Sat Nov 17, 2018 8:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw shape
Replies: 2
Views: 103

### Re: Seesaw shape

Yes, molecules with see-saw shape usually have lone pairs.
Sat Nov 10, 2018 6:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 13
Views: 776

### Re: Bond Angles

Are we supposed to remember bond angles?
Sat Nov 10, 2018 4:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: (CH3)2Be shape
Replies: 2
Views: 164

### Re: (CH3)2Be shape

So in such cases do we consider C as the central atom or Be? Do have to take into account and write both the shapes?
Sat Nov 10, 2018 4:18 pm
Forum: Hybridization
Topic: sp^3d or dsp^3
Replies: 6
Views: 399

### Re: sp^3d or dsp^3

Does dsp^3 mean that the s and p orbitals used are from a shell higher than the d? For example, when 3d, 4s, and 4p are involved in hybridization we say dsp^3?
Mon Nov 05, 2018 2:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Wavelengths
Replies: 3
Views: 132

### Wavelengths

What is the shortest wavelength we can observe for objects using the De Broglie equation?
Sun Nov 04, 2018 8:48 pm
Forum: Administrative Questions and Class Announcements
Topic: Question from textbook
Replies: 2
Views: 142

### Question from textbook

Hi, can someone please help me with this question - A student prepared a solution of sodium carbonate by adding 2.111 g of the solid to a 250.0-mL volumetric flask and adding water to the mark. Some of this solution was transferred to a buret. What volume of solution should the student transfer into...
Tue Oct 30, 2018 3:08 pm
Forum: Lewis Structures
Topic: determining shapes of molecules
Replies: 2
Views: 135

### Re: determining shapes of molecules

Do we learn about Molecular Orbital Theory in 14A?
Tue Oct 30, 2018 3:06 pm
Forum: Lewis Structures
Topic: Lewis Structure for Compounds
Replies: 6
Views: 245

### Re: Lewis Structure for Compounds

How do we know which Lewis structure is correct and whether we have to add a double bond or not?
Tue Oct 30, 2018 2:57 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Perchlorate (ClO4)-
Replies: 7
Views: 8062

### Re: Perchlorate (ClO4)-

In ClO4- would all four oxygen atoms have a formal charge of -1?
Sun Oct 28, 2018 2:18 pm
Forum: Lewis Structures
Topic: Lewis Dot Order
Replies: 10
Views: 238

### Re: Lewis Dot Order

Do we have to make dots according to how they fill the px, py, pz orbitals? For example, if px and py each have 1 electron then do they have to be singly represented around the atom?
Sun Oct 28, 2018 2:15 pm
Forum: Administrative Questions and Class Announcements
Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Replies: 121
Views: 6913

### Re: MIDTERM PRACTICE - Garlic Bread Review Session[ENDORSED]

Thank you so much! Are you going to post more midterm practice worksheets? Where can we get more practice problems from? LYNDON: I will not be posting more practice worksheets. I do hand out paper copies of practice at my normal session workshops. However, you can only get previous ones from student...
Sun Oct 28, 2018 2:10 pm
Forum: Coordinate Covalent Bonds
Topic: Covalent Character
Replies: 4
Views: 703

### Re: Covalent Character

How can we know whether a bond has a covalent and ionic character?
Fri Oct 19, 2018 10:01 pm
Forum: *Particle in a Box
Topic: Midterm
Replies: 17
Views: 1718

### Midterm

What is the syllabus for the midterm that is on 5th November 2018?
Fri Oct 19, 2018 9:50 pm
Forum: *Shrodinger Equation
Topic: Test 2
Replies: 5
Views: 384

### Re: Test 2

Dr. Lavelle said that everything in outline 2 leading upto today will be on the test.
Fri Oct 19, 2018 9:47 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electrostatic potential energy
Replies: 1
Views: 67

### Electrostatic potential energy

What is the significance of the equation E is directly proportional to q1q2/r ?
Fri Oct 12, 2018 4:55 pm
Forum: Properties of Light
Topic: Photon energy
Replies: 2
Views: 83

### Re: Photon energy

Because the energy of an electromagnetic radiation can never be negative. The energy emitted by an object (here, radiation) is always positive.
Fri Oct 12, 2018 4:53 pm
Forum: Trends in The Periodic Table
Topic: electron affinity [ENDORSED]
Replies: 15
Views: 785

### Re: electron affinity[ENDORSED]

If electron affinity is negative then does that mean that the atom accepts electron easily and vice-versa meaning if electron affinity is positive the atom has difficulty accepting an electron?
Fri Oct 12, 2018 4:38 pm
Forum: *Shrodinger Equation
Topic: Wavefunction
Replies: 3
Views: 214

### Re: Wavefunction

How important is it to know the Schrodinger Equation because it can be very confusing?
Wed Oct 03, 2018 1:28 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Formula Units [ENDORSED]
Replies: 3
Views: 1211

### Re: Formula Units[ENDORSED]

So when we say 2NaCl we are referring to 2 formula units of NaCl? Calculating formula units is a little confusing too. Could someone please explain it?
Wed Oct 03, 2018 1:25 pm
Forum: Significant Figures
Topic: Rules For Significant Figures
Replies: 6
Views: 404

### Re: Rules For Significant Figures

So how many sigfigs are there in 705.0090 ??
Wed Oct 03, 2018 1:21 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 217
Views: 115285

### Re: Advice from a Medical Student[ENDORSED]

Thank you so much Ashley! I will definitely be taking your advice.