CHEMISTRY COMMUNITY

asannajust_1J

the units for k are 1/M^(n-1)*s. n being the order of the reaction. Thus, if the reaction is first order the units are 1/s and second order 1/Ms and so on.
x-1 is just 1/x

asannajust_1J

the units for k are 1/M^(n-1)*s. n being the order of the reaction. Thus, if the reaction is first order the units are 1/s and second order 1/Ms and so on.

asannajust_1J

for the problem that asks to solve for the partial pressures of each gas PCl3 + Cl2 =PCl5 .. I found the value of K=10 but was not sure how he got the ratio of 2x/x^2 . Can someone please explain this?

asannajust_1J

For a cell to do work there must be a difference in cell potential. The maximum work a cell can do is equal to the difference in cell potentials.

asannajust_1J

Could you specify which question?

asannajust_1J

For student A, start by writing each rate law as if it were the rate-limiting step. If the second step is the slow step, an intermediate is found in your rate law. the k in the rate law from stoichiometric coefficients corresponds with the rate constant for step two. Then, since intermediates are no...

asannajust_1J

reaction mechanisms are different pathways in which a reaction can take place. Since reactions do not simply occur at once, they are broken down into steps for different reactions to take place.

asannajust_1J

the total order of the reaction is the sum of the exponential coefficients. This can be determined based on graphs, a given rate law, or an integrated rate law.

asannajust_1J

reaction rate increases as temperature increases, while reaction rate decreases as temperature decreases

asannajust_1J

unimolecular would correspond with 1 molecule that initiates the reaction
bimolecular would correspond with 2 molecules colliding to start a reaction
termolecular would correspond with 3 molecules colliding
and higher molecularity is very rare

asannajust_1J

the ratio of the rates is one and when you change the concentrations the only exponent that will also give 1 as a result would be zero.

asannajust_1J

No, Lavelle said in lecture to focus on pre-equilibrium

asannajust_1J

If not indicated, the fast step will be in equilibrium and the slow step will not.

asannajust_1J

The pre-equilibrium method assumes that the fast rate before the slow step creates a bottleneck as the product of the fast reaction will accumulate and we assume that this causes the first reaction to be in equilibrium. By using the equilibrium constant, you can use this to solve for any intermediat...

asannajust_1J

(a) Verify that there is no difference in the state function S for a process in which 1.00 mol of nitrogen molecules in a cylinder of volume 3.00 L at 302 K undergoes the following three steps: (i) cooling at constant volume until T 5 75.6 K; (ii) heating at constant pressure until T 5 302 K; (iii) ...

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The problem: A certain synthesis gas is 40.0% by volume carbon monoxide, 25.0% hydrogen gas, 10.0% noncombustible gases, and the rest methane. What volume of this gas must be burned to raise the temperature of 5.5 L of water by 5 8C? Assume the gas is at 1.0 atm and 298 K and that all three gases ar...

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In problem 4.17, I calculated parts a-d; however do not understand how to obtain delta H for this reaction: A technician carries out the reaction 2 SO2(g) 1 O2(g) S 2 SO3(g) at 25 8C and 1.00 atm in a cylinder fitted with a piston and maintained at constant pressure. Initially, 0.030 mol SO2 and 0.0...

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Assume H and S are independent of temperature, calculate G for each reaction at 80C. What temperature range will each reaction be spontaneous. For part a, B2O3 +6HF --> 2BF3 +3H2O when I started this problem I used the standard heat of formations for the products - reactants and the standard entropy...

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since Estandard=-rt/nf (lnK)
as you increase the value of K, increasing the amount of product, you increase the Estandard of the cell.
as you decrease the value of K, increase the amount of reactant, you decrease the Estandard of the cell.

asannajust_1J

Yes, you must balance each half reaction to determine n, the number of electrons transferred in the reaction.

asannajust_1J

the reduction of cr2o7 2- goes from oxidation number (6+-->3+) which is a transfer of 3 electrons, but since there are two, it would transfer 6 electrons. The coefficients of the reaction do not influence the cell potential so you would not divide the cell potential by this value. 1 electron is tran...

asannajust_1J

If the concentration of K+ is 20-30x greater inside the cell than outside. What is the potential difference between the inside and the outside of the cell (due only to imbalance in K+ ions)? the reduction of K+ to K is -2.93... I am not sure how to approach this problem. I considered using Q but the...

asannajust_1J

I don't remember going over the idea of cathodic protection and/or rust in lecture (i.e the activity series, and the factors involved in determining the best form of cathodic protection). There was 2 homework questions regarding this in section N. Are we responsible for knowing this for the test?

asannajust_1J

For 6L.9 ad 6L. 10, how do you know how the reaction will take place. In other words, how do you decipher which will be reduced and which will be oxidized when given potassium permanganate and FeCL2 react in an acidic solution. Would you use the standard cell potentials to determine the reaction tha...

asannajust_1J

The question asks you to calculate the K value at 25C and 150C. I correctly found the K value for the reaction at 25 C using equation G=-RTlnK, but am not sure how to apply the vant hoff equation at 150C.. the reaction is NH4CL -> NH3 + HCl

asannajust_1J

If Q= products/reactants, wouldn't the concentration of H+ be on te denominator resulting in -1 as the pH for this problem?

asannajust_1J

If K is large, can we assume there will be a positive cell potential for a reaction, and if K is less than one will this result in a negative cell potential? Not sure if this is the correct relationship between K and E.

asannajust_1J

How do we determine the relative reducing strength of a metal without any standard cell potentials?

asannajust_1J

Do we need to know the different C values at constant pressure for monoatomic, diatomic, and polyatomic gases?
ex) monoatomic Cv=3/2R Cp= 5/2R ; Diatomic Cv= 5/2R Cp= 7/2R; Polyatomic Cv = 7/2R Cp=9/2R

asannajust_1J

Yes, the area under the curve indicates the amount of work done on/by a system by comparing pressure time volume. In an irreversible expansion, once the final volume is achieved, the work done by the system prior to that is no longer relevant thus only using the amount of work done from the final vo...

asannajust_1J

In any situation indicating a closed/isolated system where there is no change in volume (unless it is under a piston)

asannajust_1J

Degeneracy is a way to quantify the possible number of positions a particular species can form. In relation to entropy, it can be seen as the number of Microstates/positions that are possible for a particular system.

asannajust_1J

If the system is closed a change in volume can still occur in the case of a gas doing work on a piston. In an isolated system, there would be no change in volume.

asannajust_1J

Extreme disorder?

asannajust_1J

number of sig figs in a pH or pOH only count after the decimal. For pH=3.489, there would be three sig figs since there are 3 decimal place. If the question is only 1 sig fig then the pH can be reported to 1 decimal place. Hope this makes sense!

asannajust_1J

Not sure how to answer this problem, A buffer solution containing equal amounts of acetic acid and sodium acetate is prepared. What molar concentration of the buffer must be prepared to prevent a change in the pH by more than 0.20 after the addition of 1.00 mL of 6.00 m HCl(aq) to 100.0 mL of the bu...

asannajust_1J

He said sometime during week 3, I assume there will be an email sent out to notify everyone.

asannajust_1J

6G has practice problems

asannajust_1J

it is important to memorize the list of strong acids and Bases, since everything not on this list would be considered a weak acid or weak base.

asannajust_1J

If a bond is being broken, energy is required thus the reaction would be endergonic

asannajust_1J

to determine the ratio of the concentrations, record the final and initial concentrations of each gas, then determine ratio between them.
Ai=28 Af=18 f-i= 10
Bi=0 Bf=5 f-i= 5
Ci=0 Cf=10 f-i=10
the ratio of A:B:C is 2:1:2

asannajust_1J

Difficulty understanding this problem... Would the K value be equal to the concentration of gas in products since the solid's are not included in the equation PV=nRT or the calculation of the equilibrium constant.

asannajust_1J

You must use an ICE chart and assume that the products start with zero initially...

asannajust_1J

The reaction favors equilibrium so affecting one side will affect the other side of the reaction, and rxn will proceed to oppose/resist change.

asannajust_1J

this is due to the fact that multiplying the reaction by a value (2) would be doubling all the stoichiometric coefficients, ultimately squaring the entire K value. Thus raising the K value to any value n.

asannajust_1J

Unless a change had been acted upon a system or reaction, there will be no change in equilibrium. Adding or removing P/R, affecting the concentration for both (aq) and (g) products/reactants.

asannajust_1J

Use KP for gases with partial pressure values and use KC for concentration gases, and aqueous conditions.

asannajust_1J

octahedral complexes are the most common, so generally they will have 6 water molecules attached.

asannajust_1J

you should know the strong acids and bases, so you will know that everything else would be weak.

asannajust_1J

How do you determine the coordination number and shape of a coordination compound?
Why is K[Cu(en)2(CN)2]-1 coordination number 6 octahedral while [Co(OH)2C2O4]-1 is 4 square planar/tetrahedral?
Is the -1 charge playing a role in determining the + of ligands or is it the ion outside the complex?

asannajust_1J

CCl4 is a much larger molecule, and has more electrons, so it will form more LDF's, which require more energy to break apart.

asannajust_1J

Acid rain results from the reaction of H2O+CO2→ H2CO3 Increase in concentration of CO2 in the atmosphere will result in an increase of H2CO3, which is acidic forming acid rain. SO2, NO, and NO2 are also components of acid rain that form HNO3 and HSO4- (strong acids) A way to reduce this would be ins...

asannajust_1J

How does that tell you the coordination number?

asannajust_1J

a weak base will not dissociate completely, so it won't yield as many OH- ions in the solution, and since a strong base does dissociate completely the OH- concentration is much higher in a solution with a strong base than one with a weak base.

asannajust_1J

Not all ring structures chelate though, make sure that the electron pairs are close together, otherwise they will only remain polydentate and will not chelate.

asannajust_1J

How do you approach this problem? not sure of my answers... determine the coordination number of the metal ion in each of the following complexes: (a) [NiCl4]2–; (b) [Ag(NH3)2]1 ; (c) [PtCl2(en)2]21 ; (d) [Cr(edta)]2

asannajust_1J

the question is mostly focused on the fact that this reaction is in equilibrium and has a K constant

asannajust_1J

More s character means that it has less electron-electron repulsion since there are less electrons in the p orbital, therefore the less repulsions would result in greater bond angle.

asannajust_1J

I think to know the biological context of vitamin b12 through the chelation of cobalt.

asannajust_1J

The second bond would form as a result of an unhybridized orbital.

asannajust_1J

I got my test back during discussion today, so I would say your next discussion section.

asannajust_1J

Would water attract Be2+ or Al3+ more strongly through the ion-dipole IMF?

asannajust_1J

How do you determine whether SiF4 or Si2F2 has stronger IMF's?
I know the linear structure creates stronger IMF's than trigonal planar. But would the larger number of e- in SiF4 allow for more IMF's?

asannajust_1J

This is the potential energy for the intermolecular interactions rather the ones within a molecule.

asannajust_1J

I drew all three isomers. and since Cl is the most electronegative, it has the negative dipole in the 1,4 structure it is nonpolar since the dipoles are directly across from each other (so they cancel), but in isomer 1,3 and 1,2 the dipoles do not cancel thus they are polar.

asannajust_1J

How do you determine the shape of this molecule? (CH3)2Be. Not sure how to translate the ionic lewis structure into the shape since the central atom had two "branches".

asannajust_1J

All molecules, whether they are polar or nonpolar, have London Dispersion forces. It is the only type of intermolecular force that exists between noble gases and nonpolar molecules.

asannajust_1J

The polarity of so2 is due to the lone pairs on the S, which creat a bent shape. This will make more sense once we learn shape.

asannajust_1J

Polarizing power depends on size and charge. The smaller and higher the charge, the greater the ability to attract the electron cloud of the partial negative atom. Smaller atoms allow for less distance between atoms, so electrons can be easily distorted in a molecule, and a higher charge will allow ...

asannajust_1J

These instantaneous "bounces" in temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles. Electron clouds of two relatively non-polar molecules have moments of attraction.

asannajust_1J

Explain how covalent bond dissociation energy is related to covalent bond multiplicity, atomic radius, and the presence of unpaired electrons. Am mostly confused on the reference to the presence of unpaired electrons.

asannajust_1J

What are the factors affecting covalent bond length and the effect of each?

asannajust_1J

What is the difference between electronegativity and polarizability?

asannajust_1J

Should we be familiar with complex line structures for the midterm.. never went over it.

asannajust_1J

• Describe the nature of light as electromagnetic radiation (wave model) and as a stream of photons (photon model).

asannajust_1J

Question: Arrange the cations Rb+, Be2+, Sr2+ in order of increasing polarizing power. I know this is based on, which is more electronegative, but don't know how to approach Rb+ and Sr2+ since they are isoelectronic.

asannajust_1J

This is due to resonance. Resonance makes it so that the electrons are delocalized and the actual structure is a combination of all of the different resonant structures, which creates a "blend" or average of the bond lengths.

asannajust_1J

dots normally represent lone pairs and the lines represent bonds, it is definitely important to represent bonds using the lines rather than dots to avoid confusion.

asannajust_1J

Diagonal relationship: Some elements of certain groups in the second period resemble with the certain elements of the next higher group in the third period. This is called diagonal relationship. Thus lithium resembles magnesium (Mg), beryllium (Be) resembles aluminum (Al) and boron (B) resembles sil...

asannajust_1J

Basically the electrons that are closer to the nucleus (in smaller sublevels s<p<d<f) are better at shielding. For example, electrons in the s orbital are better at shielding than the p orbital since they are closer to the nucleus and experience a greater nuclear charge in addition to the fact that ...

asannajust_1J

the Lanthanide series atomic number 57-70 comes before Bi3+

asannajust_1J

Normally you wouldn't have to worry about this in the context of this class, but Bi3+ has 3 less electrons so the configuration from the closest noble gas, Xenon, would be [Xe]4f^14 5d^10 6s^2

asannajust_1J

The nodes represent where the electrons cannot be found. It is less likely for an electron in the p orbital to be found close to the nucleus; however, it just depends on the electron-electron interactions as well as the effective nuclear charge experienced by that electron.

asannajust_1J

IE for Oxygen is lower than N and F because having a half full or completely full orbital is more stable and favorable. Thus, since oxygen has 4 valence electrons, it is 1 electron too many to have a half full orbital (3 e-out of 6). Therefore, the Ionization Energy (energy to remove an electron) is...

asannajust_1J

My reasoning for this problem was: a) is false since Zeff is dependent on the # e- because the amount of shileding that can occur is affected by the number of electrons. More electrons, more shielding, lower Zeff. b) is true because the p and d orbitals are more effective at shielding since they are...

asannajust_1J

Additional practice problems in the book work well for me.

asannajust_1J

for part A, just use the equation (velocity)=(frequency)(wavelength) for part B, the question asks about the relationship between energy and frequency so you would use E=hf for part C, then using the energy you just determined, use the equation E= (hc) /(wavelength) so solve for the wavelength. for ...

asannajust_1J

What exactly are you referring to? It could also mean H-atom

asannajust_1J

Its important to remember during this question where the electron is both in the orbital and the periodic table is extremely helpful in working that out.

asannajust_1J

28. Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Answer the following three questions. A. What is the kinetic energy of the ejected electron? 1.99*10^-19J 29. B. How much energy is required to remove a...

asannajust_1J

It's also significant when considering the fact that the second derivative of the trig function will return to the original function (possible change of sign, but that is not important)

asannajust_1J

If the electromagnetic radiation is light, then it can be thought of as an EM wave. So since E=hv, the energy per photon would be proportional to the frequency not necessarily the speed. Correct?

asannajust_1J

since 1/2mv^2= hf - threshold?

asannajust_1J

But if kinetic energy is = energy of a photon - threshold energy, then wouldn't the velocity of the photon be proportional to the frequency.

asannajust_1J

Why does the speed of radiation decrease when the frequency decreases?

asannajust_1J

The leading zeroes do not influence sig figs unless you are adding, then the decimal place is important.

asannajust_1J

What Pages are the homework problems on for this chapter? having hard time figuring out which section they apply to...

asannajust_1J

In the reactants, there is an O2.

asannajust_1J

You should have a pretty good idea of the visual light spectrum, but besides that I think that should be it.

asannajust_1J

Threshold energy depends on the problem. Remember, for an electron to be emitted, a specific wavelength and energy must be reached. This is unique to every situation.

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