Search found 21 matches
- Sat Mar 18, 2017 10:05 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Higher Residual Entropy
- Replies: 1
- Views: 519
Re: Higher Residual Entropy
NO would have a higher residual entropy than BF3 because if you look at it, BF3 can have the fluorine atoms in 3 different places, but essentially they are the same molecule. However, flipping the N and O position across the double bond gives 2 different orientations which is why NO has higher resid...
- Sat Mar 11, 2017 11:34 am
- Forum: *Alkenes
- Topic: Naming alkenes [ENDORSED]
- Replies: 2
- Views: 731
Re: Naming alkenes [ENDORSED]
I believe the -a- is simply there to make the name easier to say versus having two consonants together.
Re: Naming
It is 4-ethyl,2,2-Dimethyl-hexane instead of 3-ethyl, 5,5-dimethyl-hexane because you always want the lowest possible number you can have. 2 is lower than 3 and 5 so this is why you would name it this way.
- Thu Feb 23, 2017 2:21 pm
- Forum: General Rate Laws
- Topic: catalyst
- Replies: 1
- Views: 514
Re: catalyst
Yes, a catalyst can be included in a rate law. That's because, most reactions occur in a series of step and the rate is based on the "rate determining step", which is the slowest step. A catalyst may be a reactant in the rate determining step, and a product in a subsequent step. Therefore,...
- Sun Feb 19, 2017 11:38 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Catalyst
- Replies: 6
- Views: 1236
Re: Catalyst
Catalysts work by providing an alternative reaction pathway for the breaking and remaking of bonds. The activation energy for this new pathway is often less than the activation energy of the normal pathway. When a catalyst is present, one of the reactants reacts with the catalyst to form an intermed...
- Thu Feb 09, 2017 5:49 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams
- Replies: 4
- Views: 844
Re: Cell Diagrams
Many electrode reactions involve only ionic species, which typically consist of aqueous and gas. If neither of the electroactive species is a metal, some other metal must serve as a conduit for the supply or removal of electrons from the system; platinum is commonly used.
- Fri Feb 03, 2017 3:24 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Higher Entropy
- Replies: 2
- Views: 821
Re: Higher Entropy
Hi!
It is also very important to remember the third law of thermodynamics which states that the entropies of all perfect crystals approach zero as the absolute temperature approaches zero (0 Kelvin). So, keeping this in mind, we also should look at the temperature these molecules are at.
It is also very important to remember the third law of thermodynamics which states that the entropies of all perfect crystals approach zero as the absolute temperature approaches zero (0 Kelvin). So, keeping this in mind, we also should look at the temperature these molecules are at.
- Thu Jan 26, 2017 2:20 pm
- Forum: Calculating Work of Expansion
- Topic: non isothermal processes
- Replies: 2
- Views: 567
Re: non isothermal processes
If the reaction is isothermal then delta U (change in internal energy) is zero and because delta U= q + w, --> q= w. A reversible process has the same external and internal pressure while in an irreversible process, the internal and external pressure are different.
- Thu Jan 19, 2017 2:12 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Cpm vs Cvm [ENDORSED]
- Replies: 1
- Views: 6087
Re: Cpm vs Cvm [ENDORSED]
Heat capacity increases with molecular complexity because as more atoms are in the molecule, there are more possible bond variations that can absorb the added energy.
- Thu Jan 12, 2017 2:20 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3916512
Re: Post All Chemistry Jokes Here
Getting in the spirit of chem...
- Fri Dec 02, 2016 10:22 am
- Forum: Student Social/Study Group
- Topic: Indicators
- Replies: 3
- Views: 844
Re: Indicators
It is probably a good idea to remember that indicators are weak acids that give a strong color change with pH. The popular indicator phenolphthalein in acid appears colorless, however in base appears pink. The H+ release results in a structural change so light is absorbed differently. The color chan...
- Tue Nov 29, 2016 12:04 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kp and Kc Same?
- Replies: 4
- Views: 1174
Re: Kp and Kc Same?
Hopefully this can help! Kp and Kc are not the same because Kc refers to concentration while Kp refers to partial pressure.
- Mon Nov 21, 2016 5:08 pm
- Forum: Conjugate Acids & Bases
- Topic: pH and pOH
- Replies: 4
- Views: 1339
Re: pH and pOH
pOH = -log[OH-]
the negative log of the hydroxide ion molarity
pKw = -log Kw
the negative log of the water ion product , Kw
pKa = -log Ka
the negative log of the acid dissociation constant, Ka
pKb = -log Kb
the negative log of the base dissociation constant, Kb
the negative log of the hydroxide ion molarity
pKw = -log Kw
the negative log of the water ion product , Kw
pKa = -log Ka
the negative log of the acid dissociation constant, Ka
pKb = -log Kb
the negative log of the base dissociation constant, Kb
- Wed Nov 16, 2016 11:03 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Question regarding heteronuclear molecular orbitals
- Replies: 2
- Views: 665
Re: Question regarding heteronuclear molecular orbitals
I would imagine we need to know how to draw heteronuclear molecular orbitals for the quiz, but we have to know how to draw it for the final anyways. Basically use the same outline for MO as homonuclear molecular orbitals with Z<8, except the more electronegative element has a lower energy level.
- Thu Nov 10, 2016 3:36 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3916512
Re: Post All Chemistry Jokes Here
Saw this one coming...
- Thu Nov 03, 2016 3:25 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Bonding vs. Anti-bonding
- Replies: 2
- Views: 2590
Re: Bonding vs. Anti-bonding
Bonding: constructive interference; in-phase; orbital overlap; molecular stability & lower energy. Sigma has head to head overlap while pi bonds along a parallel plane or axis
Anti-Bonding: destructive interference; out-of-phase; no orbital overlap; molecular instability & higher energy.
Anti-Bonding: destructive interference; out-of-phase; no orbital overlap; molecular instability & higher energy.
- Fri Oct 28, 2016 12:38 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3916512
Re: Post All Chemistry Jokes Here
cackled out loud when I saw this
- Mon Oct 17, 2016 9:54 am
- Forum: Ionic & Covalent Bonds
- Topic: Ionic Bonds of Octet Outliers
- Replies: 3
- Views: 854
Re: Ionic Bonds of Octet Outliers
Two exceptions to the octet rule are hydrogen and helium, which both have room for only two electrons in their valence shell. Because they both only have one shell, the first shell has only one s orbital and no p orbital, so it holds only two electrons (which is when helium and hydrogen are most sta...
- Thu Oct 13, 2016 10:42 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Building-Up Principle [ENDORSED]
- Replies: 3
- Views: 4366
Re: Building-Up Principle [ENDORSED]
It helps with practice, but basically you can tell which state it is in by the levels which are filled in an electron configuration. When in an excited state, the electrons "jump" to a higher level, which is not normally found in the ground state configuration of the atom. This jump causes...
- Sat Oct 08, 2016 12:04 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Energy Level Changes in Orbitals
- Replies: 2
- Views: 607
Re: Energy Level Changes in Orbitals
I think its more a conceptual aspect. So if an electron is excited to a higher energy level, it can still exist in the same orbital as it was before (1s/2s), but now it also has the possibility of occupying a different orbital (2s/3p).
- Sun Oct 02, 2016 10:37 am
- Forum: Significant Figures
- Topic: Sig Figs in a problem with addition & multiplication [ENDORSED]
- Replies: 5
- Views: 3154
Sig Figs in a problem with addition & multiplication [ENDORSED]
What would we do if we were given a problem that had addition or subtraction and multiplication or division in the same question? Are we supposed to do sig figs at each step as we work through the problem or do we just wait until the end?