CHEMISTRY COMMUNITY

ClaireHW

For the pre-equilibrium approach, there are 2 ways to do it. I'm going to do it Lavelle's way. For: A + B -> C (fast) C -> D (slow) Write out the rate law for the slow step: Rate = k[C] Since C is an intermediate and it cancels out, you don't want it in your final rate. You can replace it using the ...

ClaireHW

Is there a way to tell if a step is slow or fast in a proposed mechanism? What sort of data would need to be given? And will this sort of question be asked?

Claire Woolson Dis 1K

ClaireHW

The following rate laws were each derived from an elementary reaction. In each case, write the chemical equation for the reaction, determine its molecularity, and draw a proposed structure for the activated complex. a. Rate = k[CH3CHO] (products are CH3 and CHO) b. Rate = k[I] 2 [Ar] (products are I...

ClaireHW

In terms of a redox reactions, what do K and Q equal?
Do they equal [red]/[ox] or [ox]/[red]?

Thanks!

Claire Woolson Dis 1K

ClaireHW

How does one go about setting up the equations used for this question step by step?

Thanks!

(Claire Woolson Dis 1K)

ClaireHW

For 1st order reactions the equation is typically ln[A]_f = -kt + ln[A]₀
I found a variation used in the textbooks: ln([A]₀/[A]_f) = kt
Can these equations be used interchangeably and produce the same answer?

Thanks!

(Claire Woolson Dis 1K)

ClaireHW

When dealing with rate laws, is it always necessary to convert all units into moles, liters, or seconds?
If not, when can we use difference units?

Thanks!

(Claire Woolson Dis 1K)

ClaireHW

Is the order of the reactions just the sum of the exponents of the reactants? If not, how is it calculated?

Thanks!

(Claire Woolson Dis 1K)

ClaireHW

For this problem, why aren't the products considered in the rate law?

(Claire Woolson Dis 1K)

ClaireHW

The unique rate for the reaction aA + bB -> cC + dD is -(1/a)(delta [A]/delta t) = -(1/b)(delta [B]/delta t) = (1/c)(delta [C]/delta t) = (1/d)(delta [D]/delta t) Dr. Lavelle explained it in the first kinetics lecture, but didn't explicitly call it the unique rate law. Hope that helps! (Claire Wools...

ClaireHW

In a neuron, the concentrations of K+ ions inside the cell is about 20 - 30 times as great as that outside. What potential difference between the inside and the outside of the cell would you expect to measure if the difference is due only to the imbalance of potassium ions? I'm confused about why E=...

ClaireHW

What is the difference between an electrode and an electrolyte?

Thanks!

(Claire Woolson Dis 1K)

ClaireHW

How do we know to use H2O in part b?

(Claire Woolson Dis 1K)

ClaireHW

Determine the unknown quantity in each of the following cells: a) Pt(s) I Hg2 (1.0 bar) I H+ (pH=?) II Cl- (aq, 1.0 M) I Hg2Cl2(s) I Hg(l), E=0.33V b) C(gr) I Cl2(g, 1 bar) I Cl- (aq, ?) II MnO4- (aq, 0.010 M), H+ (pH=4.0), Mn2+ (aq, 0.10 M) I Pt(s), E=-0.30 I'm specifically confused about part b an...

ClaireHW

How exactly is Q or K written in terms a cell diagram?

(Claire Woolson Dis 1K)

ClaireHW

What are the rules for constructing a cell diagram? Order, inert metals, commas v. lines v. double lines, etc.

Thanks!

(Claire Woolson Dis 1K)

ClaireHW

Using values in Appendix 2A, calculate the standard Gibbs free energy for the vaporization of water at 25, 100, and 150 degrees C.
b) what should the value at 100 degrees C be?
c) Why is there a discrepancy?

(Claire Woolson Dis 1K)

ClaireHW

How does delta S tot determine spontaneity?
I am confused to the difference between delta S and delta S tot.

(Claire Woolson Dis 1K)

ClaireHW

Can someone also explain under what conditions is delta U equal to zero?

(Claire Woolson Dis 1K)

ClaireHW

Assume that the standard change in enthalpy and entropy are independent of temperature and calculate the change in the standard Gibbs Free Energy for each of the following at 80 C. Over what temperature range will each reaction be spontaneous under standard conditions? a) B2O3 + 6HF -> 2BF3 + 3H2O b...

ClaireHW

Initially a sample of ideal gas at 323K occupies 1.67L at 4.95 atm. The gas is allowed to expand to 7.33L by two pathways a) isothermal, reversible expansion; b) isothermal irreversible free expansion. Calculate delta S total, delta S, and delta S surroundings for each pathway. I'm confused on not o...

ClaireHW

I'm super confused about how the answer is figured out in this question. Container A is filled with 1.0 mol of the atoms of an ideal monatomic gas. Container B has 1.0 mol of atoms bound together as diatomic molecules that are not vibrationally active. Container C has 1.0 mol of atoms bound together...

ClaireHW

Why it is more favorable for Gibbs Free Energy to be negative?
Thanks!
(Claire Woolson Dis 1K)

ClaireHW

Can someone also do the same for Gibbs Free Energy?

Thanks!

(Claire Woolson Dis 1K)

ClaireHW

What is entropy? Physically what does an entropy change look like?

(Claire Woolson Dis 1K)

ClaireHW

Just for clarification, can someone explain the key differences between irreversible and reversible reactions?

(Claire Woolson Dis 1K)

ClaireHW

I noticed that in certain problems the tempurature wasn't given, but was required to solve the problem. The Solutions Manual used the temperature 298K. If the temperature isn't given but is necessary to solve, do we just assume its at 298K?

(Claire Woolson Dis 1k)

ClaireHW

Use bond enthalpies in Table 8.6 and 8.7 to estimate the reaction enthalpy for

CH4 + CCl4 -> CHCl3 + CH3Cl

I was confused by the method shown in the Solutions Manuel. Could someone explain step by step how this is done?

Thanks!

(Claire Woolson Dis 1K)

ClaireHW

In the solution manual, the values of Cp,m and Cv,m are somehow found. Could someone explain how these equations were derived?

Thanks!

(Claire Woolson Dis 1K)

ClaireHW

I'd also like to ask if someone could tell us how many steps will have to be calculated and how they come together to get the final temperature.

(Claire Woolson Dis 1K)

ClaireHW

Can someone explain why the given answers are correct? In an diabetic process, no energy is transferred as hear. Indicate whether each of the following statements about an diabetic process in a closed system is always true, always false, or true in certain conditions (specify condition): a) delta U ...

ClaireHW

Also what is the difference between Standard reaction enthalpy and standard enthalpy of formation?

(Claire Woolson Dis 1K)

ClaireHW

HI!
I'm super confused about what a standard reaction enthalpy is. Could someone expand on what Dr. Lavelle defined it as and give another example?
Thanks!

(Claire Woolson Dis. 1K)

ClaireHW

Hi!
I always forget the difference between endothermic and exothermic reactions. Does anyway have an easy way to remember them?
Thanks!

(Claire Woolson Dis. 1K)

ClaireHW

State whether reactants or products will be favored by an increase in the total pressure (resulting from compression). If there is no change, explain why that is so.

Cl2(g) <-> 2Cl(g)

Thanks!

(Claire Woolson Dis. 3J)

ClaireHW

Hi, could someone explain the difference between endothermic and exothermic reactions and give an example of each?

Thanks!

(Claire Woolson Dis. 3J)

ClaireHW

Are there other special names for compounds (such as aqua for H2O or ammine for NH3) that we should know?

Thanks!

(Claire Woolson Dis 3J)

ClaireHW

Thanks guys! Impressive and super helpful responses.

(Claire Woolson Dis 3J)

ClaireHW

For the reaction N2(g) + 3H2(g) <-> 2NH3(g) at 400K, K= 41. Find the value of K for each of the following reactions at the same temperature.
a) SO2(g) + 1/2O2(g) <-> SO3(g)
b) SO3 <-> SO2(g) +1/2O2(g)
c) 3SO2(g) + 3/2O2 <-> 3SO3(g)

Thanks!

(Claire Woolson Dis 3J)

ClaireHW

Borazine, B3N3H3, a compound that has been called "inorganic benzene" because of its similar hexagonal structure (but with alternating B and N atoms in place of C atoms), is the basis of a large class of boron-nitrogen compounds. Write its Lewis structure and predict the composition of the...

ClaireHW

Hi, can someone explain how to do this problem? Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center. a) HN(CH2CH2NH2)2 b) Co3 2- c) H2O d) oxalate Thanks! (Claire Wo...

ClaireHW

So when a there are a sigma and a pi bond, does this mean there are two sigma bonds over lapping?

(Claire Woolson Dis 3J)

ClaireHW

Hi could someone go over 4.19 b?
The question is:
Predict the bond angles at the central atom of (CH3)2Be

Thanks

(Claire Woolson Dis. 3J)

ClaireHW

I'm confused about the distinction between a double sigma and a pi bond. Are they the same thing or is there a slight variation?

Thanks!

(Claire Woolson Dis. 3J)

ClaireHW

The answer given was 6.
I'm wondering how we get to 6 from that amount of moles.

ClaireHW

Given the balanced equations: 2C4H10 + 13O2 -> 8CO2 + 10H2O
What is the net number of moles of gas produced if 4 moles of C4H10 are used?

(Claire Woolson Dis 3J)

ClaireHW

Are there any rules for determining when a molecule will have a radical? If so what are they? Also, on the midterm, will we be required to determine if a molecule has a radical?

Thanks.

(Claire Woolson DIs. 3J)

ClaireHW

Compounds having bonds with a high covalent character tend to be less soluble in water than similar compounds that have low covalent character. Use electronegativities to predict which of the following compounds is more soluble in water; a) AlCl3 or KCl b) MgO or BaO Could you just briefly explain t...

ClaireHW

Select from each of the following pairs of Lewis structures the one that is likely to make the dominant contribution to a resonance hybrid. Explain your selection. Unfortunately, I can't include the structures, but I'm confused about the answers given in the book. Can you explain the resonance hybri...

ClaireHW

How many electrons can have to following electrons in an atom:
a) n=2, l=1
b) n=4, l=2, m=-2
c) n=2
d) n=3, l=2, m=+1

I'm confused about the logic behind solving these problems.

(Claire Woolson Dis. 3J)

ClaireHW

I'm confused about m and its relationship to electron configurations in general.
Does m influence electron configurations when we write them out? For instance how does m affect Carbon or [He]2s22p2? Where does m become relevant doing orbital problems?

(Claire Woolson Dis. 3J)

ClaireHW

What's the difference between the work function and the ionization energy?

(Claire Woolson Dis 3J)

ClaireHW

I'm confused about the relationship between electron configuration, the wave function, orbitals, and the actual pattern of electron movement. Can anyone explain these concepts?

(Claire Woolson Dis 3J)

ClaireHW

Does anyone know what homework is due this week, if any?

(Claire Woolson Dis. 3J)

ClaireHW

In 1.0 s, a 60 W bulb emits 11J of energy in the form of infrared radiation (heat) of wavelength 1850 nm. a) What is the energy per photon of light emitted? b) How many photons are emitted in one second?

I am particularly confused by part b.

(Claire Woolson Dis. 3J)

ClaireHW

When using the equations v=-R(1/n2 - 1/n2) or E= -hR/n2, the final answer for energy is negative if the electron is descending in energy levels. If negative energy is energy lost, where does it go?

(Claire Woolson, Dis 3J)

ClaireHW

Question: In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series (for example, Balmer series, Lyman series, Paschen series), as shown in Figs. 1.10 and 2.1. What is common to the lines within a series that makes grouping them together logical? I ...

ClaireHW

Does the CuSO4 bond with the H2O to form the new compound or do they become more connected due to being in an aqueous solution?
(Claire Woolson 3J)

ClaireHW

Does anyone know what makes certain substances see through or transparent? What about certain molecular structures makes substances that way?
Thanks
(Claire Woolson 3J)

ClaireHW

Why is the molar mass of CuSO4 5H20 used in part b?

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