## Search found 21 matches

Sat Mar 18, 2017 10:27 am
Forum: Calculating Work of Expansion
Topic: Potential/Residual Entropy
Replies: 1
Views: 262

### Re: Potential/Residual Entropy

The equation given doesn't account for the thermal entropy of molecules and we haven't done any problems that deal with calculating thermal entropy so I think we only need to know how to calculate potential entropy using S = kB * ln W
Sat Mar 18, 2017 10:21 am
Forum: Phase Changes & Related Calculations
Topic: General formula for phase changes for enthalpy.
Replies: 2
Views: 511

### Re: General formula for phase changes for enthalpy.

When you're asked to find the required heat for some substance to undergo a phase change and you're given a mass, you usually convert it to moles first because enthalpies are generally given in kJ/mol so you'd have to find the moles of the sample to make the units cancel. So convert grams->moles the...
Fri Mar 17, 2017 10:38 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Intensive vs. Extensive
Replies: 1
Views: 359

### Re: Intensive vs. Extensive

Extensive properties depend on the amount of a sample you have while intensive does not. For heat capacity, the larger the sample you have, the more heat is required to change the temperature of that sample. For specific heat capacity, it doesn't depend on how large or small your sample is; the amou...
Fri Mar 17, 2017 10:33 am
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: Electron Density and Conformations
Replies: 1
Views: 721

### Re: Electron Density and Conformations

Electron density plays a role in the stability of molecules. If there is high electron-electron repulsion between adjacent atoms, then there will be greater steric strain and the molecule will be less stable than its conformation that reduces this strain. Because some conformations are so unstable, ...
Fri Mar 17, 2017 10:28 am
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Stability of chair and boat isomers
Replies: 1
Views: 263

### Re: Stability of chair and boat isomers

Think of the molecule in 3D space. In the chair conformation, one CH2 is pointed down while the one opposite of it is pointed up. There is no angle, torsional, or steric strain because of the positions of the atoms and the minimizing of electron repulsion. In a chair conformation, however, there is ...
Sat Feb 11, 2017 6:22 pm
Forum: Balancing Redox Reactions
Topic: Ozone as an oxidizing agent [ENDORSED]
Replies: 1
Views: 287

### Re: Ozone as an oxidizing agent[ENDORSED]

Ozone would be the oxidizing agent because of the BrO3- that forms in the reaction. In BrO3-, each oxygen has a -2 oxidation state, which means that the oxygen went from 0 in ozone to -2 in BrO3-. The oxygen was reduced, making it the oxidizing agent.
Sun Feb 05, 2017 8:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: order of galvanic cell
Replies: 2
Views: 347

### Re: order of galvanic cell

The right-hand electrode in the diagram is treated as the location where reduction occurs while the left-hand electrode is treated as the site of oxidation. The sign of the cell potential will tell you if the reaction is spontaneous in that direction or if the reverse reaction is spontaneous. So you...
Sun Jan 29, 2017 10:35 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs irreversible equations
Replies: 3
Views: 511

### Re: Reversible vs irreversible equations

We need to know which equations to use on our own. For irreversible expansions, the pressure is constant so we use w=-P(delta V) and for reversible expansions we use w=-nRT(ln(V2/V1)). Those equations will be given to us on the formula sheet, however, we must select the appropriate one to solve the ...
Sun Jan 22, 2017 10:02 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Related to work on and by
Replies: 1
Views: 240

### Re: Related to work on and by

When the question says that work is done on the system, it means that some external force is applied to the system, such as an increase in pressure. Think of a bike pump--when you push the handle down, the pressure in the ball or tire or whatever you are pumping up (which would be the system) is exp...
Fri Jan 13, 2017 1:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Defining Enthalpy
Replies: 1
Views: 193

### Re: Defining Enthalpy

Enthalpy is the heat of the reaction and allows us to monitor the energy changes that occur when the pressure is constant. Since the definition of enthalpy states that pressure is constant, we will always make that assumption in our calculations. To find the enthalpy, you find the sum of the interna...
Thu Dec 01, 2016 7:02 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8037
Views: 1408967

### Re: Post All Chemistry Jokes Here

Thu Dec 01, 2016 4:49 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Chapter 12 question 27
Replies: 1
Views: 776

### Re: Chapter 12 question 27

For part (a), you would begin by using the 200.0 mL volume and the molarity of the HCl solution. HCl is a strong acid so we can assume 100% dissociation; therefore, the moles of HCl are equal to the moles of hydronium ions present. Since we know the volume and molarity (which is moles per liter), we...
Mon Nov 28, 2016 12:18 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8037
Views: 1408967

### Re: Post All Chemistry Jokes Here

Sodium doesn't take "Na" for an answer.
Sat Nov 19, 2016 2:21 pm
Forum: Lewis Acids & Bases
Topic: Textbook Problem
Replies: 1
Views: 370

### Re: Textbook Problem

The images show the molecules of the acids with the hydronium ions being the gray spheres and the conjugate bases being the colored spheres. Recall that a strong acid dissociates completely in water. When comparing the images, the strongest acid would show the gray and colored spheres completely sep...
Fri Nov 11, 2016 9:29 am
Forum: General Science Questions
Topic: MO Energy Diagrams [ENDORSED]
Replies: 1
Views: 890

### Re: MO Energy Diagrams[ENDORSED]

You just use the periodic table! The nuclear charge is the same as the atomic number, and, therefore, the total number of protons in that element's nucleus. For example, Oxygen has an atomic number of 8 so it has 8 protons in its nucleus, and its nuclear charge is 8. So if the element is lower than ...
Fri Nov 04, 2016 7:34 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Homo and Lomo
Replies: 1
Views: 483

### Re: Homo and Lomo

HOMO and LOMO refers to the electron configuration of excited atoms. The electron is excited by a photon and one of the valence electrons transitions from the highest occupied molecular orbital to the lowest unoccupied orbital. So if an electron is in the sigma star molecular orbital, and the lowest...
Fri Oct 28, 2016 3:17 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8037
Views: 1408967

### Re: Post All Chemistry Jokes Here

Florence Flask was getting ready for the opera. All of a sudden, she screamed: "Erlenmeyer, my joules! Somebody has stolen my joules!" The husband replied, "Calm down, honey. We'll find a solution."
Fri Oct 21, 2016 2:17 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8037
Views: 1408967

### Re: Post All Chemistry Jokes Here

Anions aren't negative, they're just misunderstood.
Fri Oct 14, 2016 3:33 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8037
Views: 1408967

### Re: Post All Chemistry Jokes Here

This is relevant to what we've talked about in class this week haha
Wed Oct 05, 2016 7:15 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shells, Subshells, and Orbitals
Replies: 1
Views: 397

### Shells, Subshells, and Orbitals

If anyone is as confused as I was about the differences between these three, I found this video extremely helpful!