CHEMISTRY COMMUNITY

Shannon Asay 1C

What are the differences between the rate constants, k, k', and K?

Shannon Asay 1C

What is the process of obtaining a pseudo rate law, and how does it apply to determining the rate constant?

Shannon Asay 1C

A catalyst would appear at the beginning of the reaction and would not be used up, and an intermediate would be generated in a reaction, but then be used up in the next part of the reaction, so it would not appear in the final equation.

Shannon Asay 1C

How does the collision model and activated complex model relate to the rate law?

Shannon Asay 1C

I believe you could use the equation ln(k2/k1)=-Ea/R*(1/T2-1/T1). Just plug in all your variables and solve for Ea.

Shannon Asay 1C

How would we determine what the rate-determining step is, or would that be given to us in a question?

Shannon Asay 1C

I believe it's because it's H2O, and you don't need to include it if the solution is aqueous.

Shannon Asay 1C

I think they're both the same. I believe one equation is lnk2/k1=-delta(h)/R(1/t2-1/t1) and the other is lnk2/k1=delta(h)/R(1/t1-1/t2). When you do the math, I believe they work out to be the same things.

Shannon Asay 1C

The n in the Nernst equation refers to the number of electrons transferred and you can find it by writing out the redox reaction.

Shannon Asay 1C

Ecell is the potential difference between the cathode and anode and Ecell° is the potential difference under standard conditions. Typically, you'll solve for Ecell when you are given the concentrations of reactants and products, like in this equation E = E° - RT ln Q. Ecell° is usually given to you,...

Shannon Asay 1C

How would we use the unique rate law in a calculation?

Shannon Asay 1C

What does a third order reaction mean, and why is it hard to achieve?

Shannon Asay 1C

What are the steps to balance a redox reaction in acidic or basic solution?

Shannon Asay 1C

What's the difference between an electrolytic cell and a galvanic cell?

Shannon Asay 1C

A reducing agent oxidizes something and an oxidizing agent reduces something else.

Shannon Asay 1C

In the cell diagram we did in class, why was Pt(s) only in contact with the aqueous iron solution and not the copper?

Shannon Asay 1C

I believe the graph you are talking about shows the temperature dependence of K, and the slope of the line is -delta H/R.

Shannon Asay 1C

How does the salt bridge keep the charge from building up?

Shannon Asay 1C

n refers to the number of electrons that are transferred in the balanced chemical equation.

Shannon Asay 1C

How is the max potential calculated and why does it occur when very little current flows?

Shannon Asay 1C

When calculating enthalpies of melting ice, why do we have to divide the process into multiple steps?

Shannon Asay 1C

The equation of Q is Q=[NH3][H2S]. The molarity of NH3 is 1.47mol/2L and the molarity of H2S is 2.85mol/2L. Multiply those together and you'll get Q which is 1.05.

Shannon Asay 1C

The first law is basically just conservation of energy. It's shown by the equation delta u=q + w. It's saying that the internal energy of an isolated system is constant.

Shannon Asay 1C

The 2nd law says that systems spontaneously go towards states of maximum entropy, which is shown by the equation, delta s=q/T. This is also demonstrated by Gibbs free energy equation because systems that are exothermic and have high entropy are spontaneous. For the third law, it's saying that as the...

Shannon Asay 1C

I believe so, because all the equations we learned for reversible reactions relied on there being no change in temperature with the surroundings.

Shannon Asay 1C

Are micro states always dependent on the number of bonds? Would we have to calculate the entropy of more complex molecules?

Shannon Asay 1C

What did Dr. Lavelle mean when he said that if a system can be prepared in only 1 way, then S=kBlnW=0? And how did this relate to the third law of thermodynamics?

Shannon Asay 1C

I believe if volume is the only variable that changes, then yes, the volume would need to increase for the entropy to increase (for the reaction to be spontaneous).

Shannon Asay 1C

Entropy is an extensive property because it depends on the amount of substance available. However, it is also a state property because it doesn't matter the pathway it takes to get there, but the final minus initial states.

Shannon Asay 1C

Yes, when delta G is negative, the reaction is spontaneous. Dr. Lavelle proved this today when he showed how the entropy of the universe would increase.

Shannon Asay 1C

For calculating the heat given off by a neutralization reaction, would you always use the specific heat capacity of water to calculate it?

Shannon Asay 1C

What does delta u stand for and how do you calculate for it?

Shannon Asay 1C

What does it mean that when the volume of the reactants equals the volume of products, delta h is equal to delta u?

Shannon Asay 1C

In calculating the enthalpy of a system, why is it that the delta T for an exothermic reaction is positive?

Shannon Asay 1C

How does the experiment work to calculate enthalpy using the bomb calorimeter?

Shannon Asay 1C

Why is using bond enthalpies the least accurate method for calculating delta H?

Shannon Asay 1C

Lavelle brought up that there were 4 methods for calculating delta H, what was the 4th method he mentioned in lecture today?

Shannon Asay 1C

Could someone reiterate why steam causes more severe burns? How does the energy relate to this?

Shannon Asay 1C

How does the pressure of the surrounding environment affect the enthalpy of the system?

Shannon Asay 1C

I believe so. I think it's just anything he's covered in lecture over the week, so thermodynamics should be fine!

Shannon Asay 1C

I'm pretty sure for that question you're still solving for Qc for aqueous phase materials, and partial pressure for the gaseous phase molecules. I think solving for concentration or pressure depends on what the question is asking for.

Shannon Asay 1C

It would increase the formation of X because the reaction is endothermic and an increase in the temperature would increase the k value. This means an increase in the number of products.

Shannon Asay 1C

Weaker acids don't dissociate completely, like strong acids do, so there is a lower concentration of H+. Because of this, weak acids have a higher pH, because they aren't as acidic as strong acids in the same concentration.

Shannon Asay 1C

So In 5J.11 b, the equation is X2->2X, where x is a halogen. In this equation, it is essentially breaking a bond, which means it requires energy and is endothermic. In an endothermic reaction, when you raise the temperature, the value of k increases. If k increases, that means the equilibria is favo...

Shannon Asay 1C

I'm not entirely sure why either but I'm guessing it's because the number of moles of gas on either side of the equation doesn't change so one side isn't strongly favored.

Shannon Asay 1C

Will topics using or related to Gibbs free energy equation be on the first test?

Shannon Asay 1C

How would you know whether to solve for Kp or Kc?

Shannon Asay 1C

When solving an ICE table and solving for x, when do you know you can simplify a quadratic or cubed equation, and why can you do that?

Shannon Asay 1C

What is Le Chatelier's Principle and what effects cause changes to the equilibria. For example, how can you produce more product?

Shannon Asay 1C

Why are solvents not included in the equilibrium expression equation?

Shannon Asay 1C

It strongly favors the formation of products if K>10^3 and it strongly favors the formation of reactants when K<10^-3.

Shannon Asay 1C

9C.9) With the help of Table 9C.1, determine the coordination number of the metal ion in each of the following complexes: (a) [NiCl4]2–; (b) [Ag(NH3)2]+; (c) [PtCl2(en)2]2+; (d) [Cr(edta)]-. Could someone help me understand why c and d are both 6? This is what the answer key says: c) 6 (en is bident...

Shannon Asay 1C

State whether the following oxides are acidic, basic, or amphoteric: (a) BaO; (b) SO3; (c) As2O3; (d) Bi2O3.

How do we tell when it's amphoteric or not?

Shannon Asay 1C

6C.17) Which is the stronger base, the hypobromite ion, BrO-, or morphine, C17H19O3N? Justify your answer.

Why is hypobromite the stronger base?

Shannon Asay 1C

What is the percentage deprotonation for a molecule and how do you calculate it?

Shannon Asay 1C

Bronsted and Lewis acids and bases are essentially referring to the same things, they're just different ways of describing an acid or a base. A Bronsted acid is a proton donor and a Lewis acid is an electron pair acceptor. A Bronsted base is a proton acceptor and a Lewis base is an electron pair don...

Shannon Asay 1C

In the example from lecture Wednesday, Dr. Lavelle said that trichloroacetic acid, CCl3COOH, was stronger than acetic acid, CH3COOH. Could someone re-explain why that is?

Shannon Asay 1C

What properties make an acid strong versus weak?

Shannon Asay 1C

6b.1) The molar concentration of HCl in hydrochloric acid is reduced to 12% of its initial value by dilution. What is the difference in the pH values of the two solutions?

How would you go about starting this problem?

Shannon Asay 1C

Can someone explain the hybridization of carbon in CH2O and the hybridization of nitrogen in NH3?

Shannon Asay 1C

The conjugate acid, in the products, is the compound that receives the proton and the conjugate base is the one that had given up the proton in the reactants. For example, with the equation, H2SO4 + H20 -> H30+ + HSO4-, the acid would be the H2SO4, the base would be H20, the conjugate acid would be ...

Shannon Asay 1C

Could I get some help with this question?

9C.7) Which of the following isomers of diaminobenzene can form chelating complexes? Explain your reasoning.

Shannon Asay 1C

How does myoglobin work to transport O2 in muscle tissue?

Shannon Asay 1C

What is a chelate and how does it work?

Shannon Asay 1C

How does cisplatin work to stop cell division?

Shannon Asay 1C

Why is a sigma bond more stable than a pi bond?

Shannon Asay 1C

Trigonal planar has 3 bonded pairs attached to the central atom and tetrahedral has 4 bonded pairs attached to the central atom.

Shannon Asay 1C

C18H38 has a higher molar mass than C5H12. The polarizability is higher for atoms with larger molecular weights. This has nothing to do with the mass, however, it's because the number of electrons increases as the mass does which allows for more polarizability of the electrons.

Shannon Asay 1C

It's because the lone pair of electrons over the central atom pushes the other electrons away from it, making the bond angles slightly smaller.

Shannon Asay 1C

Dr. Lavelle was saying that London forces were the same as induced dipole-induced dipole reactions, not dipole-induced dipole reactions. So the book is correct in saying that London forces are between nonpolar molecules and dipole-induced dipoles are between polar molecules and nonpolar molecules.

Shannon Asay 1C

I'm assuming that we will have to know the angles for the test.

Shannon Asay 1C

What is an electric dipole moment?

Shannon Asay 1C

Why are hydrogen bonds stronger than normal dipole-dipole interactions?

Shannon Asay 1C

Electronegativity increases up a group and across a period, going towards Fluorine, which is the most electronegative element. Electronegativity refers to an atom's ability to attract electrons, and since Fluorine only needs one more electron to complete its valence shell and have a full stable octe...

Shannon Asay 1C

Yes, that's correct. For example, two molecules, like pentane and 2,2-Dimethylpropane, both have the molecular formula C5H12. They have the same number of electrons, so their shape influences the strength of attraction. Certain shapes allow the molecules to get closer so they can have stronger induc...

Shannon Asay 1C

Why do smaller cations have higher polarizing powers?

Shannon Asay 1C

What are some general rules for drawing Lewis structures?

Shannon Asay 1C

Could someone go over what coordinate covalent bonds are and why they occur?

Shannon Asay 1C

Radicals are compounds with unpaired electrons. They're highly reactive because of this. In bodies, radicals can damage DNA because they react with it.

Shannon Asay 1C

a) Mn 4+ would have 3 valence electrons, as it normally would have 7, including those in the d-orbital, but since you remove 4 electrons to have the net positive 4 charge, it would have 3. You can see this by counting across the period on the periodic table. b) Rh 3+ would have 6 valence electrons b...

Shannon Asay 1C

Electron affinity is the energy released when an electron is added to a gas-phase atom. The general trend is that it increases as you go across a period and up a group.

Shannon Asay 1C

What is the meaning of electron delocalization in resonance structures?

Shannon Asay 1C

I believe it would have 7 valence electrons because you include the electrons from the d and s orbital.

Shannon Asay 1C

How is phosphorus in phosphorus pentachloride able to have more than an octet in its bonding structure?

Shannon Asay 1C

Could someone explain the periodic trend for electron affinity?

Shannon Asay 1C

In lecture today, Dr. Lavelle mentioned something about electron affinity and formal charge, did anyone catch what the last thing he said about that was?

Shannon Asay 1C

I think either one would be marked as correct on a midterm, it's just the noble gas abbreviation makes it easier especially when you get further down on the periodic table when there are more shells.

Shannon Asay 1C

What are the differences between the angular momentum quantum number and the magnetic quantum number and how do you calculate them?

Shannon Asay 1C

What are nodal planes exactly and why do the s- orbitals not have them?

Shannon Asay 1C

Could someone help me understand the Stern and Gerlach Experiment a bit better and what they discovered about electrons from it?

Shannon Asay 1C

So the two equations are E=hv and c=(wavelength)(v). If we solve for frequency in the speed of light equation, we get v=c/wavelength. You can plug that in for the frequency of the energy equation to get E=(h*c)/(wavelength)

Shannon Asay 1C

Yeah you're correct, the wavelength and frequency are inversely proportional so as one goes up the other goes down. That's seen with this equation: c=(wavelength)(frequency). Energy and frequency are directly proportional, as seen by this equation: E=hv. When one goes up, the other does as well.

Shannon Asay 1C

For #30, I used the equation E(photon)-E(energy to remove an electron)=Ek(electron). For the kinetic energy of the electron (Ek), I plugged in the number I calculated from #28 which was 1.99x10^-19 and for E(energy to remove an electron), I plugged in the value I calculated for #29 which was 2.501x1...

Shannon Asay 1C

I had some trouble understanding in today's lecture how electron's exhibit wave-like properties and I was wondering if someone could help explain that a bit better?

Shannon Asay 1C

The electrons have negative energies according to Rydberg's equation because we take our reference point off an electron that has been completely removed and is no longer interacting with the nucleus as E=0. The minus sign is because the electron's energy has decreased and the energy is released as ...

Shannon Asay 1C

For #29, I took the work function for sodium given in the problem, 150.6 kJ/mol and multiplied that by 1000 to get the joules/mole. Then, I divided that by Avogadro's constant to get the energy per electron which should be 2.501x10^-19 J.

Shannon Asay 1C

A keV is a kiloelectron volt, there is a conversion to get it in joules in the back of the textbook. To start the problem, I converted keV to Joules, then used the E=hv equation to solve for frequency, and then you can just divide the speed of light by the frequency to get the wavelength.

Shannon Asay 1C

From my other chem classes, constants did not come into play in the final answer, you'd typically go with the same amount of sig figs as the original question states. So to answer your question, your answer would not be limited to 4 sig figs.

Shannon Asay 1C

I followed the same process as you, solving for the moles given the molarity and volume, and then using the molar mass to convert to grams. I got the same answers as you for both a and b.

Shannon Asay 1C

I personally use 1.01 for hydrogen and 16 for oxygen, but I think it's fine to use whatever number is on the periodic table.

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