Search found 19 matches
- Tue Mar 14, 2017 8:42 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: #8.101.c
- Replies: 2
- Views: 526
#8.101.c
The reaction 2 SO2(g) + O2(g) --> 2 SO3(g) occurs at 25 degrees Celsius and 1 atm in a constant pressure cylinder. Initially, 0.030 mol SO2 and 0.030 mol O2 are present in the cylinder. Part C asks "Assuming that the reaction goes to completion and that the temperature and pressure of the react...
- Thu Mar 09, 2017 2:30 pm
- Forum: *Cycloalkanes
- Topic: Multiple possible names
- Replies: 2
- Views: 396
Re: Multiple possible names
I think it depends on the number of substituents. When there are just two substituents, it would make sense to assign the smaller number to the substituent that would be named first alphabetically, and then the second substituent would get the next number. However, when you have three or more substi...
- Sun Mar 05, 2017 10:09 pm
- Forum: *Electrophilic Addition
- Topic: Help on HW 4.30 and the Arrhenius Equation
- Replies: 1
- Views: 648
Help on HW 4.30 and the Arrhenius Equation
The question asks: "The activation energy in organic reaction is known to be 125 kJ/mol. Will this reaction occur at room temperature?" How do I calculate this? I assumed we would use the Arrhenius equation and solve for k, and if k is less than 1, then the reaction wouldn't occur under ro...
- Thu Feb 23, 2017 11:50 pm
- Forum: General Rate Laws
- Topic: When B and C is significantly larger than A
- Replies: 3
- Views: 483
Re: When B and C is significantly larger than A
I believe it is just "significantly large" enough so that the concentrations of B and C remain constant when A is being used up. This way, as stated in the Course Reader, the reaction rate depends on just concentration of A.
- Tue Feb 14, 2017 7:09 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: midterm 2015 #4&5 B
- Replies: 3
- Views: 593
Re: midterm 2015 #4&5 B
I understand it is Cv because it is under constant volume due to the fact that the expansion occurs isothermally. However, in Ron's case, the temperature of the balloon actually changes. I'm confused because wouldn't this mean the expansion doesn't occur isothermally?
- Thu Feb 09, 2017 2:02 pm
- Forum: Balancing Redox Reactions
- Topic: Reduction and Oxidation [ENDORSED]
- Replies: 6
- Views: 680
Re: Reduction and Oxidation [ENDORSED]
Cu is being oxidized because it is losing two electrons, while Fe^3 is being reduced because it is gaining an electron.
- Fri Feb 03, 2017 4:26 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 8791
- Views: 1492703
Re: Post All Chemistry Jokes Here
Why are Helium, Curium, and Barium considered medical elements?
Because if you can't HEALium or CUREium, you got to BURYem.
Because if you can't HEALium or CUREium, you got to BURYem.
- Wed Jan 25, 2017 3:37 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Delta S and what it favors?
- Replies: 2
- Views: 1343
Delta S and what it favors?
Why does positive Delta S favor forward processes and why does negative Delta S not? Does "forward" refer to a reaction where a substance goes from a lower energy state to a higher one? Clarification please, thanks.
- Fri Jan 20, 2017 3:40 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: What is Kb in Entropy? Entropy Clarification? [ENDORSED]
- Replies: 2
- Views: 788
What is Kb in Entropy? Entropy Clarification? [ENDORSED]
In Chem14A, Ka and Kb dealt with acid and base equilibrium; however, I don't understand how this relates to entropy and how we're supposed to derive this value for calculations? Also, I don't fully understand the concept of entropy. I understand that it is randomness within a system, but in lecture ...
- Wed Jan 11, 2017 11:03 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Help on HW 8.57
- Replies: 4
- Views: 911
Help on HW 8.57
In this question, we must find the reaction enthalpy by subtracting the standard enthalpy of formation of all products with the reactants'. However, every time I do this, I get 312 kJ per mole, while the solutions manual says the correct answer is -312 kJ per mole. My math was -1560 - (-1300 + 2 * -...
- Thu Dec 01, 2016 11:53 pm
- Forum: *Titrations & Titration Calculations
- Topic: Finding Stoichiometric Point for Weak Acids/Bases? [ENDORSED]
- Replies: 1
- Views: 480
Finding Stoichiometric Point for Weak Acids/Bases? [ENDORSED]
Alright, so for a weak acid, the pH starts low so the stoichiometric point must be above pH 7, and for a weak base, the pH starts high so the stoichiometric point must be below pH 7. However, how would we calculate the EXACT stoichiometric point? For strong acids/bases it's easier because we can jus...
- Tue Nov 22, 2016 9:01 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Difference between aq and l?
- Replies: 1
- Views: 8183
Difference between aq and l?
When calculating equilibrium constants, we are supposed to disregard what is in the solid or liquid state. However, why don't we disregard the aqueous solution? I thought that an aqueous solution and a liquid were the same thing. Could someone clarify? Thanks.
- Tue Nov 15, 2016 6:19 pm
- Forum: Naming
- Topic: Is (OH)2 aqua? [ENDORSED]
- Replies: 1
- Views: 293
Is (OH)2 aqua? [ENDORSED]
In problem 17.29 in the textbook, the compound [Co(CN)5(OH)2]2- is named aquapentacyanocobaltate(III). However, the Course Reader says H2O is named aqua, and (OH)2 isn't the equivalent of H2O. Could someone clarify this for me? Thanks!
(I thought it would be named pentacyanodihydroxocobaltate(III)).
(I thought it would be named pentacyanodihydroxocobaltate(III)).
- Sat Nov 12, 2016 5:35 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: How to determine Nuclear Charge? [ENDORSED]
- Replies: 1
- Views: 419
How to determine Nuclear Charge? [ENDORSED]
For MO energy diagrams, knowing the atoms' nuclear charge is important. However, I don't really know how to find it. Is nuclear charge the same as the number of valence electrons an atom has? If not, what is it? Thank you! Clarification much needed!
- Tue Nov 01, 2016 2:33 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Size of Cations/Anions compared to Parent Atoms
- Replies: 1
- Views: 6307
Size of Cations/Anions compared to Parent Atoms
The Course Reader states, "But cations are smaller than their parent atoms and anions are larger." However, shouldn't cations be larger than their parent atoms because losing an electron would mean decreasing nuclear charge and thus electrons would be further from the nucleus? Also, should...
- Wed Oct 26, 2016 2:25 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bond Angles?
- Replies: 2
- Views: 847
Bond Angles?
How exactly do you calculate the angles of each bond? Also, how do these angles affect the molecule? Are we supposed to memorize the angles that correspond to a certain shape, or is there some way to calculate it? Thank you!
- Wed Oct 12, 2016 2:30 pm
- Forum: Properties of Electrons
- Topic: Removing 2nd Electron
- Replies: 2
- Views: 1434
Removing 2nd Electron
Why does it become harder to remove an electron when an atom has a net positive charge? I understand the ionization energy becomes higher after the first electron is removed, but why?
- Thu Oct 06, 2016 1:34 pm
- Forum: Properties of Electrons
- Topic: Wavelike Properties? [ENDORSED]
- Replies: 2
- Views: 640
Wavelike Properties? [ENDORSED]
I need some clarification. Throughout the Course Reader, electrons are described as having "wavelike properties." Why so? There is also an example described where "If you are driving a 1.5E3 kg car at 27.0 m.s-1, what is the De Brogile wavelength of your car? Does your car have any me...
- Fri Sep 30, 2016 3:04 pm
- Forum: Properties of Electrons
- Topic: Energy Level Model [ENDORSED]
- Replies: 2
- Views: 638
Energy Level Model [ENDORSED]
I am having trouble understanding the model depicted in the course reader. I understand that it has to do with electrons, but what exactly is happening? Why are the arrows pointing downwards and why are they of different lengths and at different levels? What is "hR"? Help would be apprecia...