CHEMISTRY COMMUNITY

Tyler_Ash_3C

You know the entropy of the system because the reactants have 3 moles of gas while the products have 2 moles of gas. Since the moles of gas decreases from reactants to products, you know that the entropy of the system must be decreasing, so the change in entropy of the system must be negative and th...

Tyler_Ash_3C

Yes, the structure with the lowest potential energy is the most stable because stable molecules experience more attractive forces and less repulsive forces. Attractive forces lower the potential energy of a molecule while repulsive forces increase the potential energy of a molecule, so the structure...

Tyler_Ash_3C

For #4 Why isn't it 1-butyl-3,4 dimethylcyclohexane? For cycloalkanes with more than two substituents, you must compare each individual number for each substituent: 1-butyl-3,4-dimethylcyclohexane (incorrect) 4-butyl-1,2-dimethylcyclohexane (correct) Since your proposed answer has 1,3,4 while the c...

Tyler_Ash_3C

The intermediates are represented by the minimum of the curve between two peaks. The two peaks represent transition states, but not intermediates. In general, the number of intermediates formed is one less than the number of peaks or "humps" because when the graph returns to a minimum at t...

Tyler_Ash_3C

Yes the rate determining step and rate limiting step mean the same thing. It is always the slow step because it "determines" or "limits" the speed of the reaction.

Tyler_Ash_3C

You don't write the salt bridge in the diagram. You include Pt(s) when the anode or cathode or both do not have a solid in their half reaction. This is because a solid electrode must be present for the system to function. Pt(s) is used because it is an inert conductor that allows electron flow witho...

Tyler_Ash_3C

Q is the reaction quotient. Mathematically, it is represented by the fraction: [products]/[reactants]. At equilibrium Q is equal to K, the equilibrium constant of the reaction. Partial pressures for gases can be used in the formula instead of concentrations if this is given in the problem. Recall fr...

Tyler_Ash_3C

The midterm is mainly thermochemistry and electrochemistry I believe. Nothing after electrochemistry should be on it. The practice exams in the back of the course reader really helped me study for 14A with Lavelle, and I have been doing the same thing to prepare for this midterm. It also is helpful ...

Tyler_Ash_3C

A photon checks into a hotel and is asked if he needs any help with his luggage. He replies, "no, I'm travelling light."

Tyler_Ash_3C

The two methods are interchangeable under standard conditions using the values given in Appendix 2A. Neither method is really preferable, but rather it depends on what information you are given in the problem or how the problem is asked. In instances under non-standard conditions, I think the second...

Tyler_Ash_3C

It takes more heat to raise 1.00 g of ice by 1.00 degree Celsius than it does to raise the temperature of 1.00 g liquid water by 1.00 degree Celsius. It also takes more heat to raise the temperature of liquid water than to raise the temperature of water vapor. The equation q=cm(change in temperature...

Tyler_Ash_3C

Since the molar heat capacity is concerned with a temperature change, it can be expressed in terms of degrees Celsius or degrees Kelvin. Zero degrees Celsius is equal to 273.15 Kelvin, and this difference can be used to calculate degrees Celsius from Kelvin by subtracting this number, and to calcula...

Tyler_Ash_3C

On problem 8.19 of the homework exercises, there are two terms for the total heat supplied, one to eat the copper kettle and one to heat the water. In both cases the temperature change used is 100-22 degrees Celsius. For these types of problems, is the temperature change of the container always the ...

Tyler_Ash_3C

Since volume is not clearly defined in this problem, I think that it is acceptable to assume that at whatever volume the reaction is taking place, the pressure of NO2=1.00 bar while the concentration of the products is the same as their partial pressures. There should exist some volume where this ho...

Tyler_Ash_3C

What is Cesium and Iodine's favorite TV show?
CSI

Tyler_Ash_3C

If the concentration of H3O+ is 10^-7, then pH= -log(10^-7). Using the log rule dealing with exponents, pH= 7 log(10), and pH=7, which proves that the solution would be neutral. Autoprotolysis refers to the transfer of a proton between two identical molecules. In this case two molecules of H2O yield...

Tyler_Ash_3C

Got mole problems? Call Avogrado at 602-1023.

Tyler_Ash_3C

That is correct. Both Lewis and Bronsted explanations can describe the same acid or base. Notice that for acids, the net change in charge is -1, while for bases, the net change in charge is +1. When an acid donates a proton its charge becomes more negative, and when it accepts an electron its charge...

Tyler_Ash_3C

You write (π2p)^4 because in molecular orbital diagrams you can't determine which p orbitals are x, y, and z due to the different ways molecular orbitals interact during bonding. The expanded version is used for valence electron configurations of a single atom. When writing the valence electron conf...

Tyler_Ash_3C

LiH is more ionic than HCl because it has a greater difference in electronegativity between the two atoms. Even though hydrogen is at the left of the periodic table, it is actually more electronegative than one might expect. If you look in the chart in the course reader, you can see that hydrogen ha...

Tyler_Ash_3C

What did the chemist say when he wrote down nitrogen dioxide incorrectly? ONO!!!

Tyler_Ash_3C

A diagonal relationship is when diagonal elements in the Periodic Table show similar chemical properties. For example, elements that have similar atomic radius and ionization energies will likely exhibit similar chemical properties. The diagonal strip of metalloids demonstrates this characteristic s...

Tyler_Ash_3C

S, P, D, and F are subshells of an electron shell (n). Each subshell is further divided into orbitals. Each orbital can contain up to two electrons. S subshells (1s, 2s, 3s...) have one orbital. P subshells (2p, 3p, 4p...) have three orbitals. D subshells have 5 orbitals, and F subshells have 7 orbi...

Tyler_Ash_3C

For the purposes of this class, it is best to use the previous noble gas in brackets for shorthand electron configurations. Using other elements is not as practical because you would most likely confuse yourself by using an element in the middle of the period because it would become more difficult t...

Tyler_Ash_3C

For the purposes of molar mass calculations such as those in section E, charges are pretty much irrelevant to what we are doing. The charge on Cu^2+ in E23a is there to show that CuBr2 is an ionic compound in which electrons are shared between the atoms that compose it. Since the single copper atom ...

CHEMISTRY COMMUNITY

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Re: entropy question

Re: Newman Projection

Re: Quiz 3 Winter 2017

Re: Intermediates in Reaction Profiles

Re: rate determining and rate limiting step [ENDORSED]

Re: Drawing a Cell Diagram

Re: What is Q again?

Re: W '17 midterm

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Re: Finding Gibbs Free Energy - 9.55 and 9.57

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Problem 8.19

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Re: Charges [ENDORSED]