CHEMISTRY COMMUNITY

Hyein Cha 2I

Can someone please explain the difference between a reaction that is considered to be under kinetic control vs reaction considered to be under thermodynamic control? Like what control dominates at low temperature vs high temperatures? Which pathway has larger activation energy? etc..

Hyein Cha 2I

What is the unit of activation energy?

For 15.61, I used R = 8.314 J/(K*mol), and got my activation energy as Joules, but the solutions manual converted R into KJ, thus making unit of activation energy KJ.

Does it matter which one I use?

Hyein Cha 2I

Must we know about. the rate of formation of product equation for enzymes (section 15.16 of book) and the michaelis constant thing?

Hyein Cha 2I

Cali Rauk1D wrote:Do coefficients matter when calculating oxidation numbers?

Just to add, subscripts matter when calculating oxidation numbers, but not coefficients

Hyein Cha 2I

Josh Moy 1H wrote:will naming be on the final?

yes, he said just the very basics

Hyein Cha 2I

How in depth are we expected to know the derivation of and utilization of the constants Cp and Cv. Are we supposed to understand the relationship in how Cp - Cv = R ? Are we supposed to understand how these constants change with degree of freedoms? Please elaborate how greatly in depth we are suppo...

Hyein Cha 2I

It's simply that homogeneous catalysts are in the same phase as the reactants, and heterogeneous catalysts are in different state from the reactants

Hyein Cha 2I

well since q=m*c*delta T, if delta T=0, q must also equal 0.

Hyein Cha 2I

The half-life for the second-order reaction of a substance A is 50.5 s when [A]0 0.84 mol L 1. Calculate the time needed for the concentration of A to decrease to (a) one- sixteenth; (b) one-fourth; (c) one- fth of its original value. for part a, why can't we simply multiply the half life, so 50.5 s...

Hyein Cha 2I

Chris Pleman 3E wrote:Did Dr Lavelle mention the extent of the questions in the textbook that are necessary/will be covered by the Kinetics test? If so, which ones?

It's 1~39

Hyein Cha 2I

A lot of the hw questions give concentration in mmol/L instead of mol/L. Must we always convert fo mol/L or can we leave it as mmol/L ?

Hyein Cha 2I

Why does hamburger yield lower energy than steak?

Because it's in the ground state!

Hyein Cha 2I

Well no not necessarily.

If the only reactant was H2 and the reaction was second order, THEN rate would quadruple of H2 was doubled.

But for this particular question, rate would just double since order of H2 is 1. There are two reactants, H2 and I2, each with order of 1. Overall order is 2.

Hyein Cha 2I

Reaction would slow down as concentration of SO3 builds up because it is in the denominator. Plug some numbers in. Let's say the concentration of SO3 is 4, then the denominator is 2. If concentration increases to 9, then square root of 9 is 3. The point is, no matter what the exponent may be, if it'...

Hyein Cha 2I

So it says the test is on 15.1~6, but up to what problem number is the test on?

Hyein Cha 2I

Alyssa Parry Disc 1H wrote:You just look in the back of the book in Appendix 2B and then find the best half reaction with Mno4- and the best half reaction for Fe2+

? For number 15 tho

Hyein Cha 2I

I really just dont get how to write half reactions for this kind of reactions! :( can someone please please show me how to write half reactions for part a and b of this problem? Solutions manual do not make any sense to me..

Hyein Cha 2I

How is the reduction half reaction O3(aq) -> O2(g)?
There is no change in oxidation number, so how is it considered a reduction?

Hyein Cha 2I

Must the standard hydrogen electrode(she) always be on the left side of the cell diagram?

I was confused because hydrogen on can also be reduced to H2, right? So couldnt SHE also be on the right side of the cell diagram?

Hyein Cha 2I

What is special about Daniell Cell that sets it apart from other galvanic cells? Are there any notable difference?

Hyein Cha 2I

Two chemists go into a restaurant.
The first one says "I think I'll have an H2O."
The second one says "I think I'll have an H2O too" - and he died.

Hyein Cha 2I

So what exactly is the difference between galvanic cell and electrolytic cell?

Hyein Cha 2I

Is delta U = 0 for isothermal, reversible processes only or does it also apply to irreversible ones?

Hyein Cha 2I

When do we use delta H instead of q as in delta S = delta H/T? (when the problem doesn't tell you that it's constant pressure)

Do you always use delta H instead of q during phase changes?

Hyein Cha 2I

So I thought I had to use delta S = C * ln(T2/T1) when there is change in temperature.

But in the solutions manual for 9.13, it used delta S = nR*ln(T2/T1).

Can someone explain?

Hyein Cha 2I

the question says "During the test of an internal combustion engine, 3.00L of nitrogen gas at 18.5 degrees C was compressed suddenly (and irreversibly) to .500L by driving in a piston. In the process the temperature of the gas increased to 28.1 degrees C. Assume ideal behavior. What is the chan...

Hyein Cha 2I

Dr. Lavelle never mentioned the Clausius Inequality in class, so is it relevant for the midterm? If so, can someone explain how it relates to ΔS = q rev /T? ^ I agree that this probably won't be on the midterm since it was not covered in class/discussion. But, a process does maximum work if it take...

Hyein Cha 2I

Is the link for practice midterm posted yet? Thank you!

Hyein Cha 2I

When solving a problem, when do we assume that delta U = 0, thus q=-w?

i.e. Is it only for reversible/isothermal path?

Hyein Cha 2I

I still don't get why delta G have is zero to find the minimum temperature. Could someone please explain?

Hyein Cha 2I

"Look mom! a Carbon tetrafluoride!"

Report card:

Math: C

History: F

English: F

Chemistry: F

PE: F

Hyein Cha 2I

I would tell another chemistry joke, but all of the good ones Argon...

Hyein Cha 2I

At constant pressure, q = enthalpy. Thus, enthalpy only includes the "heat" part.

Hyein Cha 2I

How much heat is required to convert a 42.30 g block of ice at -5.042 degrees C into water vapor at 150.35 degrees C?"

Why can't you use enthalpy of sublimation instead of adding enthalpy of fusion and of vaporization and heat change in liquid state?

Hyein Cha 2I

We will usually take chemical reactions as occurring in isothermal environments. This is the basis for standard molar enthalpies of formation and standard reaction enthalpies we have discussed and can be found tabulated in the back of the book. All these values are predicated on the fact that tempe...

Hyein Cha 2I

Oxygen diflouride is a colorless, very poisonous gas that reacts rapidly with water vapor to produce O2, HF and heat: OF2 +H20 yields O2 +2HF and delta H is =- 318 kJ. I just don't get why T remains constant when calculating for -PdeltaV = -deltanRT. Also, why is T 298K and not other temperature? Th...

Hyein Cha 2I

How would you solve this question? In the solutions, it says to use 5/2R.. what’s the value of R in this case?

Hyein Cha 2I

Will stuffs like Cv,m= (3/2)R for monatomic ideal gas be on the test 1?? If so, will we need to memorize all the formulas or will it be given?

Hyein Cha 2I

In section 8.9 of textbook, it states that Cp,m is larger than Cv,m since not all the heat supplied is used to raise the temperature at constant pressure. I didnt really understand why not all heat is used to raise temperature at comstant pressure. Can someone please explain?

Hyein Cha 2I

how is the unit of pressure kg/(m*s^2)?

Hyein Cha 2I

it's just to keep track of sig figs. You do not need to write it in scientific notation :)

Hyein Cha 2I

Do ta's write their own discussion tests? or do all discussion sessions have the same test?

Hyein Cha 2I

In 8.55, thr answer sheet shows that delta H of 2Al + 3/2 O2 yeidls Al2O3 is -1676kJ. However, K dont understand how delta H of above equation is the same as delta H of 2Al + O2 yields Al2O3. Can someone explain?

Hyein Cha 2I

jillian1k wrote:1 L•atm is equal to 101.325 Joules.

There's an example on page 274-275 using this conversion.

Ohhh thank you!

Hyein Cha 2I

How do you convert 1.48 L•atm to Joules?

Hyein Cha 2I

Thank you ziyang!

Hyein Cha 2I

Nitrous acid has a pKa of 3.16, so the pKb of its conjugate base must be 14-3.16 = 10.84 Acetic acid has a pKa of 4.75, so the pKb of its conjugate base must be 14-4.75 = 9.25 Since 10.84 > 9.25, and a large pKb corresponds to a weaker base, the conjugate base of nitrous acid is weaker. This can al...

Hyein Cha 2I

You can think of it in terms of Le Chatelier's Principle. When nitrous acid is dissolved, it produces a weaker conjugate base than that of acetic acid. This means that the conjugate base of acetic acid is better at eating all the hydronium ions (in the solutions manual, it says H+, not sure if they...

Hyein Cha 2I

Autoprotolysis is simply when a proton (H+ ion) is transferred between two identical molecules. One of them will be bronsted acid (giving H+) and one of them will be bronsted base (gaining H+). So for water, an H+ ion is being transferred from one water molecule, thus forming a hydronium ion (H3O+) ...

Hyein Cha 2I

Kyra LeRoy 1F wrote:100 kPa=1 bar, so to go from 1kPa you multiply each by 1/100 bar.

ohh so we always need to have pressure in terms of 'bar?'

Hyein Cha 2I

Question is: Acetic acid is used as a solvent for some reactions b/w acids and bases. a) nitrous acid and carbnonic acids are both weak acids in water. Will either of them act as a strong acid in acetic acid? explain your answer b) will ammonia act as a strong or weak base in acetic acid? Explain yo...

Hyein Cha 2I

Can someone please explain both parts of the question 11.89? I first dont get how you would write balanced equation when you don’t know the composition of A B and C, and also why is partial pressures all over 100 in the answer sheet for part b? For example, why is partial pressure for C not 10 and 1...

Hyein Cha 2I

Why are thevalues of K and Kc different for some of the reactions in table 11.2? Shouldnt they all be the same?

Hyein Cha 2I

You can use the concentrations if you want to, but parts a and c have all reactants and products in the gas phase, so its easier to use pressure and not convert to concentration. For part b, since the components that are counted in Q are aqueous, it makes more sense and is faster to use concentrati...

Hyein Cha 2I

The question asks to write the reaction quotient for three chemical equations. I was wondering why, in the solutions manual, Q is found by using pressure for part a and c whereas concentration is used to find Q in part b. Does it matter at all? Can I just use concentration to find Q for all three eq...

Hyein Cha 2I

Could some one please explain why the ratio [O2]/[O3] would be different? The solutions manual says that "by solving for Kc in each case" I will be able to figure out why the ratio of concentration is different, but I do not understand the solution manual's explanation.

Hyein Cha 2I

Up to what section of ch 11 are we being tested on?

Hyein Cha 2I

Can someone please explain part B about why C6H4 might be highly reactive?

Hyein Cha 2I

Mirrat wrote:yes, the ligands bond to the central metal atom.

But how do you know which one is bonding to the central atom?

Hyein Cha 2I

When you draw the lewis structure for CO32-, there is one C-O double bond, and two single C-O bonds. The single bonds leave the oxygen atom with a -1 formal charge and these atoms have the potential to bind a metal atom in two different places, hence making CO32- a bidentate ligand. Ohhh so we use ...

Hyein Cha 2I

What is the difference between tm complex and a coordination compound?

Hyein Cha 2I

Brigitte Phung 1F wrote:In discussion, my TA stated that for the purposes of the test, two of the more important Latin root elements to remember are Copper and Iron. In a coordination compound with a negative charge, Copper is written as Cuprate and Iron is written as Ferrate.

thank you!!

Hyein Cha 2I

Thio is used when an oxygen atom in the compound has been replaced by a sulfur atom. N or S is underlined depending on when it is the atom that 'links' to the compound, for eg O in H2O could be underlined to show that it is the one linking. wait, by linking do you mean forming a bond? So underline ...

Hyein Cha 2I

The ligands only have to be in alphabetical order when writing out the name, when writing the formula for the compound the order doesn't matter. You should always write OH2 in coordination compounds instead of H2O. Oh, i was confused because 17.31 part C's answer has (H2O) instead of (OH2) can you ...

Hyein Cha 2I

Could someone please explain how to determine if a ligand is polydentate or not?

Also, how do you determine if a ligand, for example, CO3 2- (part b of 17.33) has atoms will lone pair of electrons which makes it polydentate? Is drawing the lewis structure the only way to determine it?

Hyein Cha 2I

I got teo questions:

Where did the prefix thio- come from in ligands such as NCS- (thiocyanato)?

Also, for NCS-, i saw in table 17.4 that either N or S is underlined. When is N underlined and when is S underlined?

Thanks

Hyein Cha 2I

As seen in the picture, it says that if the complex has ocerall negative charge, the suffix -ate is added to the stem of the metal’s name. Also, if symbol of metal has latin origins, then the latin stem is used. How can we know if an element has latin roots or not? Must we memorize all latin root el...

Hyein Cha 2I

The question asks to write the formula for the following coordination compound D. Sodium bisoxalato(diaqua)ferrate(III) I was wondering why the answer is Na[Fe(OH2)2(C2O4)2] instead of (C2O4)2 being inront of (OH)2? I thought ligands were supposed to be in alphabetical order. Shouldnt oxalate come b...

Hyein Cha 2I

Sigma bonds refer to single bonds. Pi bonds are double, but it can be triple bonds too. A double bond contains one sigma bond and one pi bond. A triple bond contains one sigma bomd and two pi bonds.

Hyein Cha 2I

The element with higher electronegativity (higher pull for electrons) will have negative sign, and the element with lower electronegativity (less pull for electrons) will have positive sign. It makes sense, because if you want 'negative' more strongly, you will have partially negative sign. For exam...

Hyein Cha 2I

Ok.. so.. I have no clue how to draw lewis structures for these complex molecules, like glycine. Can someone explain the steps I should follow when drawing lewis structures for very very complicated molecules?

Hyein Cha 2I

Hi, I found on google that the least electronegative atom should be the central atom, but we learned in class that it should be the atom with least Ionization energy. Which is the correct one? Also, in one of the book examples in chapter 3, it asked to draw the lewis structure for KSCN ion, so SCN- ...

Hyein Cha 2I

Emma Miltenberger 1K wrote:If you are referring to part C, it asks for the valence-shell configuration of the group 5 transition metals. I was confused on this as well. I think the solution manual made an error and is referring to the group 7 transition metals (Mg, Tc, Re, etc.).

yaa if that's the case, it all makes sense..

Hyein Cha 2I

How does the ability to "penetrate" the nucleus account for higher Zeff? Ability to penetrate means that the electron can be closer to the nucleus, thus the net positive charge experienced by the electron will be stronger than the net positive charge experienced by the electron that's far...

Hyein Cha 2I

thank you all so much! It makes sense now

Hyein Cha 2I

The question asks for the notation for the valence-shell configuration (including the outermost d electrons) of the Group 15 elements. Since 3 of d shell is filled and both 2 electrons of s shell are filled, the valence shell notation should be (n-1)d^3 ns^2. However, the solutions manual says it's ...

Hyein Cha 2I

I am confused on how to find delta V for heisenberg uncertainty equation. For example, for question 1.45, it says a bowling ball of mass 8 kg is rolled down a bowling alley lane at 5+/- 5 m/s (5 plus minus 5 meter/sec). What is the minimum uncertainty in its position? In the solutions manuel, it say...

Hyein Cha 2I

Is the hw for discussions this week on ch 3 again? or ch 4?

Hyein Cha 2I

The question is: ‘In the heavier transition metal elements, especially lanthanoids and actinoids, there are numerous exceptions to the regular order of orbital occupation predicted by the building-up principle. Sugfest why more exceptions would be noted for these elements’ I have seen the the soluti...

Hyein Cha 2I

Element chlorine can have oxidizing state from -1 to +7. The atom can gain one more or lose several elections to reach relatively stable state. Oxidizing state represents the number of electron(s) atom gains/loses to form ion. (Positive means losing while negative means gaining) I get -1, cause tha...

Hyein Cha 2I

But where do we get or how do we figure out what oxidation numbers chlorine can have. Or is it something we have to memorized because if I would know how to get that then I would be able to write the electron configuration. No, you would not have to memorize it, you can figure it out by looking at ...

Hyein Cha 2I

Yes, it is always the valence electron (the outermost electron) that will be removed. So yes, in the example you stated, electron from 2p5 will be removed

Hyein Cha 2I

Gabriela Carrillo 1B wrote:In relation to covalent and ionic bonds are Lewis diagrams only applicable to covalent bonds???

No, Lewis diagrams are applicable to ionic bonds also

Hyein Cha 2I

Shawn Patel 3C wrote:Hey,
I'm pretty sure Dr. Lavelle stated in class that the concept is good to know and understand, but you wouldn't get points marked off if you chose to not label px or py.

so for Nitrogen, for example, can I write 1s^2 2s^2 2P^3 ? Instead of 1s^2 2s^2 2Px^1 2Py^1 2Pz^1 ?

Hyein Cha 2I

wait are you asking how to convert cm in meter? Could you clarify your question? cause 100cm = 1m, thus 1cm = 0.01m

Hyein Cha 2I

Ψ^2 is just the probability that you will find an electron in that location of an atom. Ψ^2 corresponds to the density of electrons because the higher the density of electrons, the higher the probability that you will find an electron in that particular location of the atom.

Hyein Cha 2I

N1 is always the "final energy" lvl, so after the electron emits energy.

For example, if in the question, electron goes from n=4 to n=2, then N1=2 and N2=4.

Hyein Cha 2I

Charlotte Shieh 1F wrote:If an atomic spectra lies within the visible light spectrum (Balmer series), would we be expected to know what color light it is?

Just know that red is 700nm and violet is 400nm

Hyein Cha 2I

How does one determine whether emission is in part of the balmer series or lyman series? I know that the visible region is associated with the balmer series and the ultraviolet region associates the lyman series, but how do we determine the energy value? It's part of balmer series when energy that ...

Hyein Cha 2I

Thomson thought that atoms are uniform spheres of positively charged matter in which electrons are embedded, whereas Rutherford stated that atoms are made of electrons that orbit a positively charged nucleus made up of protons and neutrons. To further clarify, Thomson had the "plum pudding&quo...

Hyein Cha 2I

I would use 3.00 x 10^8 for the homework problems, since Dr.Lavelle used it in his lecture~ but like the above reply said, i'm sure it will be more clear on the tests

Hyein Cha 2I

So the question is "In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series(for ex, Balmer, Lyman, Paschen series), as shown in figs 1.1 ans 2.1. What is common to the lines within a series that makes grouping them togehter logical?" I w...

Hyein Cha 2I

Another way of looking at it is when frequency decreases, wavelength increases and when you draw that out, the slope of the waves look flatter. Since slope is basically the same as "extent of change" (slope is the change in y over the change in x), a flatter or I guess you could say small...

Hyein Cha 2I

I read that section of the textbook (about the series), but I do not even get what those series are supposed to represent.. or what purpose they serve.. can someone explain please?

Also, there is the expression for balmer series and rydberg, but what is the expression for the Lyman series?

Thanks!

Hyein Cha 2I

I did it a little differently from the book but got similar answers (around .05 off - not sure if that's a huge problem), so hope this helps c: You have to find the limiting reactant of P4O6 first. I converted 5.77g P4 to moles: The molar mass of P4 is 123.88g 5.77g/123.88g = 0.0466 mol P4. The rat...

Hyein Cha 2I

When you use 5.77g P4 again in the second question, it's just to convert it to P4O6 because you want to find how much P4O6 came out of the first equation to use in the second equation. You would use the mole ratio so that 1 mole P4 equals 1 mole of P4O6, and then solve for how much oxygen you need,...

Hyein Cha 2I

There are two equations to the problem. For the first equation, if you use all the P4 and calculate the amount of O2 needed, you get 4.47g O2. Since you originally had 5.77g O2, you still have 1.30g O2 left. For the second equation, you use 5.77g P4 again but in the context of the second equation t...

Hyein Cha 2I

A reaction vessel contains 5.77 g of white phosphorous and 5.77 g of oxygen. The first reaction to take place is the formation of phosphorus (III) oxide, P4O6: P4 + 3O2 --> P4O6(s). If enough oxygen is present, the oxygen can react futher with this oxide to produce phosphorus (V) oxide, P4O10: P4O6 ...

Hyein Cha 2I

Hi, the (IV) in the name tin(IV) Oxide is the oxidation number of the tin metal. Also, the roman numeral is used to distinguish between SnO and SnO2, because both of them are tin oxide, but they have different oxidation numbers. So SnO would be Tin (II) Oxide, and SnO2 would be Tin(IV) Oxide. Hope t...

Hyein Cha 2I

1. Use the molecule formula C10H7OH to calculate mass percentage composition of C, H, O 2. Get the simplest ratio of mass of C, H, O in C10H7OH (C:H:O=15:1:2) 3. Get the percentage of O in C10H7OH in the sample using the ratio above (H : O = 5.20% : ? = 1:2 --> ? = 10.40%) 4. Add up the percentage ...

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