## Search found 21 matches

Mon Mar 13, 2017 10:55 am
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Priority groups
Replies: 1
Views: 294

### Re: Priority groups

Actually Cl has higher priority than CH3. Priority is determined by atomic number. The atom with a higher atomic number has higher priority. If the first atom in a substituent chain is the same for both substituents, then compare the second atom in the chain. For example, CH2CH3 is higher priority t...
Wed Mar 08, 2017 9:36 am
Forum: *Complex Reaction Coordinate Diagrams
Topic: Activation energy line on reaction diagram
Replies: 3
Views: 928

### Re: Activation energy line on reaction diagram

We know that it won't occur at room temperature because only reactions with an activation energy less than or equal to 80 kJ/mol can occur at room temperature. This is in section 4.3 of the organic textbook.
Tue Feb 28, 2017 10:59 am
Forum: *Free Energy of Activation vs Activation Energy
Topic: 4.30
Replies: 1
Views: 283

### Re: 4.30

It says on page 154 that a reaction will only occur at room temperature if the activation energy is about 80 kJ/mol or less.
Tue Feb 21, 2017 1:28 pm
Forum: General Science Questions
Topic: Bruin cast- chem kinetics
Replies: 1
Views: 379

### Re: Bruin cast- chem kinetics

The first kinetics lecture was on February 6th.
Mon Feb 13, 2017 11:58 pm
Forum: Balancing Redox Reactions
Topic: 2015 Midterm Question #7
Replies: 2
Views: 428

### Re: 2015 Midterm Question #7

No because it could just be a question where E of the anode and cathode are given and you simply add/subtract them depending on the form in which they're given.
Mon Feb 06, 2017 5:21 pm
Forum: Balancing Redox Reactions
Topic: Help on Homework Problem
Replies: 1
Views: 349

### Re: Help on Homework Problem

In order to figure out which couple is the anode and which is the cathode, you need to look up the E of each couple's reduction half reaction in Appendix 2B. Whichever one is larger is the anode, since this cell is supposed to generate energy. The species with a more negative/less positive charge in...
Tue Jan 31, 2017 3:34 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Homework Problem 9.21
Replies: 1
Views: 397

### Re: Homework Problem 9.21

So the first thing to know is that W (number of microstates) is equal to the number of possible arrangements for each molecule to the power of the number of molecules. You also need the equation that gives entropy when you know W, which is S = k*ln(W) where k is Boltzmann's constant. In (a) there is...
Mon Jan 30, 2017 6:47 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: equation from heat to a gas
Replies: 1
Views: 362

### Re: equation from heat to a gas

You use $q = nC\Delta T$ and use C at constant pressure (Cp).
Mon Jan 23, 2017 6:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Phase subscript question
Replies: 2
Views: 481

### Re: Phase subscript question

"Gr" is short for graphite, which is the most stable form of Carbon, and therefore the standard state.
Wed Jan 18, 2017 11:03 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: HW 8.53
Replies: 3
Views: 473

### Re: HW 8.53

Since this is a bomb calorimeter, heat can't go in and out of the system (it's isolated). Therefore heat(q) of the entire system is 0. Therefore any heat lost by an exothermic reaction will warm up the calorimeter, or any heat absorbed by an endothermic reaction will come from the calorimeter and co...
Wed Jan 11, 2017 10:48 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Ch 8 Q 25
Replies: 1
Views: 460

### Re: Ch 8 Q 25

The first part of the question is providing information so that you can find the specific heat of the calorimeter. You use the equation q = C * ΔT. Rearrange this so C = q / ΔT. We know the q of the reaction is q = -3.50 [kJ/mol], so if that heat is lost by the reaction it must be gained by the calo...
Mon Nov 28, 2016 8:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Negligible x given a small K value
Replies: 1
Views: 255

### Re: Negligible x given a small K value

On page 156 of the course reader it says that if X is less than 5% of the initial then approximation is okay.
Mon Nov 21, 2016 6:31 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Why when given Ka = weak acid
Replies: 7
Views: 1398

### Re: Why when given Ka = weak acid

One acid can be stronger than another acid and still not be a strong acid (one that dissociates completely in water). There are varying levels of acidity among weak acids.
Mon Nov 14, 2016 2:32 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate [ENDORSED]
Replies: 2
Views: 535

### Re: Polydentate[ENDORSED]

Ligands can be either ions or molecules. Ions only bond once to the central atom/ion in a d-metal complex, but some molecules are longer so that more than one atom in the molecule binds to the central atom. In this case, a ligand is polydentate. Unlike what the other person said, polydentate describ...
Tue Nov 08, 2016 12:47 am
Forum: Hybridization
Topic: Problem 4.91
Replies: 1
Views: 550

### Re: Problem 4.91

The wording in the solutions manual is a little confusing, but the gist is that the triple-bonded carbons both have only 2 regions of electron density. Therefore they are sp hybridized. Sp hybridized atoms generally form linear arrangements with bond angles of 180 degrees. However, the shape of benz...
Mon Oct 31, 2016 6:24 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Homework Question on Pollarding Power of Cations
Replies: 1
Views: 337

### Re: Homework Question on Pollarding Power of Cations

Rb+ < Sr2+ < Be2+ The smaller and more highly charged a cation is, the greater its polarizing power. Since Rb+ is less highly charged than the other two, it has the least polarizing power. Because Sr2+ is larger than Be2+ (it's lower down on the periodic table), it does not have as much polarizing p...
Mon Oct 24, 2016 6:31 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Characters
Replies: 5
Views: 1003

### Re: Ionic Characters

Subtract without multiplying. The bond type is not influenced by the number of bonds.
Wed Oct 19, 2016 3:49 pm
Forum: Quantum Numbers and The H-Atom
Topic: Homework Question. 2.51 [ENDORSED]
Replies: 4
Views: 2996

### Re: Homework Question. 2.51[ENDORSED]

In order to find the number of unpaired electrons in an atom, you first find what its highest energy orbital is, then find how many electrons are in that orbital. Then you can determine how many are paired. Part a: Bi is element 83. Its highest energy orbital is the p-orbital (you can find this by l...
Mon Oct 10, 2016 10:09 pm
Forum: Properties of Electrons
Topic: Energy Levels of Electrons
Replies: 1
Views: 453

### Re: Energy Levels of Electrons

3d is higher energy than 4s when Z is less than or equal to 20, but is lower once Z is greater than 20. This shift seems sudden but is actually the result of a continuous change in the relative energies of 4s and 3d. You can see a graph of that change here: http://www.scielo.br/img/revistas/qn/v36n6...
Mon Oct 03, 2016 9:19 pm
Forum: Properties of Light
Topic: Light as a Particle vs Light as a Wave
Replies: 2
Views: 421

### Re: Light as a Particle vs Light as a Wave

A wave is not a stream of photons. It is a separate thing. Light acts as a wave on the macro (classical mechanics) scale, for example in the dual-slit experiment. It acts as a particle on the micro (quantum mechanics) scale like in the photoelectric experiment. A good way to comprehend this is to th...
Sun Sep 25, 2016 4:11 pm
Forum: SI Units, Unit Conversions
Topic: Including Units in a Problem
Replies: 3
Views: 523

### Re: Including Units in a Problem

You will have to include units if you're doing dimensional analysis, which is a great way to make sure that you are using the right values in your calculations and to finish with the correct type of units. Here's a link to the Khan Academy explanation of dimensional analysis: https://www.khanacademy...