CHEMISTRY COMMUNITY

JennyCKim1J

Why is there '-0.59' at the end? is this the ln A value? If so, where in the question is the A value given?

JennyCKim1J

For 15.49b, why is [HOBr] included in the rate law? Shouldn't it be expressed in a different way (like we did in class today) because it is an intermediate?

JennyCKim1J

For 4A, how do I know that I'm using irreversible eq. instead of reversible eq?

JennyCKim1J

What is the equation d[A]/[A] for? Is this just change in [A] over time? What is the difference between d[A]=-kdt and d[A]/[A]?

JennyCKim1J

For rate, is it okay to leave the answer as mmol or do I have to convert to mol? Does rate unit always have to be M*L-1*s-1?

JennyCKim1J

For 15.23c, why is 'ln' not included in the equation? Since the equation that we start with is ln([A]t-[A]0)=-kt, I thought the equation we end up with should be ln[A]t=whatever?

JennyCKim1J

Why is large k = fast reaction?

Also, just in general, why do we want to know half-life?

JennyCKim1J

Can someone explain what n and m is for the equation

overall reaction order = n + m?

Also, I thought I could determine reaction order by looking at k; is this just another method?

JennyCKim1J

I have a pick up line instead.
"You must be made of Florine, Iodine, and Neon, because you are FINe :))"

Actually don't use it I don't think it'll work

JennyCKim1J

For the diagram Cu(s)|Cu2+(aq)||Fe3+(aq),Fe2+(aq)|Pt(s), why is Fe3+ before Fe2+? Does the order matter?

JennyCKim1J

Is Nernst equation simply used to find cell potential under non-standard conditions (not 1M)? I'm confused b/c there are different Nernst equations and I think one of them's supposed to be use to calculate k for redox reactions at equilibrium.

JennyCKim1J

Au(s) + NO3-(aq) + 4H+(aq) -> Au3+(aq) + NO(g) + H2O(l)

^ I don't understand how to get NO3- and NO from HNO3.

JennyCKim1J

Can I calculate Hvap without using/given Hvap=Hvapor-Hliquid? Similarly, can I get Hsub or Hfus?

JennyCKim1J

I think it just means that SO2F2 can exist in six different arrangements knowing that S has to be the middle.

JennyCKim1J

I think C is for constant volume, which is 3/2R, and R is just gas constant? Cv, constant volume, cannot be used for the second equation b/c volume is changing (V1 -> V2).

JennyCKim1J

When is Gibbs free energy equal to zero?

For this question:

The entropy of vap of water is 109.0J/mol*K. What is the enthalpy of vap of water at its normal boiling point of 100 degree C?

Why do we set G equal to zero?

JennyCKim1J

So both enthalpy and entropy change during phase changes?

JennyCKim1J

For the equation deltaG=G+R*T*lnQ, what is Q?

JennyCKim1J

Is Kb simply equal to R, or is it only when we are calculating W for 1 mole? If it is only for 1 mole, what is Kb?

JennyCKim1J

Out of three methods for calculating free energy, which one is the most accurate/least accurate and why?

JennyCKim1J

Can someone explain why reversible system does more work than irreversible using the 2atm pushing against 1atm vs. 2atm pushing against 2atm diagram? I get the general concept but I don't understand the diagram.

JennyCKim1J

I don't really understand the equation for G. Is it G = free energy of the gas at 1 atm + free energy difference due to different pressure? Also, is the G just simple G or deltaG?

JennyCKim1J

When is potential energy highest? For example, for combustion, is it highest before or after combustion? Why? Does the book cover this?

JennyCKim1J

So I understand that the equation for finding change in enthalpy of reaction is sum of products' change in Hf - sum of reactants' change in Hf. However, when using bond enthalpies to find change in enthalpy, why are we simply adding enthalpies on the product side and subtracting that from reactant s...

JennyCKim1J

For the test, what are the standard states we have to remember? (For example, O2?)

JennyCKim1J

For 8.27, I thought the equation for an reversible isothermal expansion is: w = -nRT*ln(V2/V1). However, on the answer sheet, "ln" is not part of the equation. Which then is the correct equation? Also, is V2 = final volume and V1 = initial volume?

JennyCKim1J

For 8.21, why is heat lost by metal = - heat gained by water? Feels like it should be: since metal (Cu) is the system, so - heat lost by the system (metal) = heat gained by water. Why are the signs flipped?

JennyCKim1J

When is the change in internal energy (U) equal to heat (q) and when is it equal to heat+work (q+w)? What is the difference between U=q and U=q+w?

JennyCKim1J

In the equation w = -nRT * ln(Vfinal/Vinitial), what does R represent?

JennyCKim1J

Maybe start from the back? Questions are divided into big sections so I'm starting with the ones covered in class!

JennyCKim1J

On page 283, for equation 14, what exactly is Hm (vapor) and Hm (liquid)? Is it related to moles like molar heat capacity (Cm)?

JennyCKim1J

My understanding is that there is no dipole moment for PO4 3- because of resonance and hybrid bond lengths are equal. Does this mean that there is no dipole moment for O3 as well?

If attached molecules are all same and there is resonance, can I say that there is always no dipole moment?

JennyCKim1J

Does x=0 mean that the amounts of both reactants and products stay the same?

JennyCKim1J

Is the conjugate base for strong acid weak base or strong base? Does it differ between Lewis acid/base & Bronsted acid/base?

JennyCKim1J

19. Calculate the reaction quotient, QC, from the following equilibrium data collected in a 3.00 L sealed reaction vessel for the reaction: AsH3 (g) ⇌ As (s) + H2 (g) AsH3 = 5.55 x 10-4 mol, As = 3.31 x 10-3 mol, H2 = 1.23 x 10-3 mol. First I divided given mols with 3.00L to find mol*L-1 and did wha...

JennyCKim1J

What is the difference between polydentate and chelate? By looking at [Co(en)3]3+, can I determine what ligands are attached to Co?

JennyCKim1J

What is IF7's geometrical shape and why?

JennyCKim1J

How can I figure out the oxidation state by looking at LS? Are there any other ways to figure out oxidation states?

JennyCKim1J

For cis-dichloreothene, I understand that there is a dipole arrow (force? what's the exact term for this) between C-Cl, but should we be thinking about C-H as well or is it just ignored completely?

JennyCKim1J

Can someone list the exceptions to octet rule? I know that
1. Any element from 3rd row or below can have more than 8 e-,
2. Be & B usually don't get all 8 e-, but I don't know if there are any other group of elements like them/the reason why.

JennyCKim1J

I think the center atom's supposed to be the one with lowest ionization E.

JennyCKim1J

On 2-43, shouldn't ground state e- config of tungsten be [Xe]4f^14 5d^5 6s^2 because tungsten originally has ... 5d^4 and it takes e- to make 5d^5? (Answer on the solution is [Xe]4f^14 5d^4 6s^2.)

JennyCKim1J

Should Ti's electron configuration be [Ar]3d^2 4s^2 or [Ar]4s^2 3d^2? Why?

JennyCKim1J

How about chapter 3?

JennyCKim1J

For chlorine monoxide, why is its chemical formula ClO instead of Cl2O (considering ionic charge)?

Also, when I drew its LS, Cl&O had single bond, and Cl had five e- (six including e- from the bond). Does this mean I have to write 1- next to Cl?

JennyCKim1J

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. (From previous Q, Ek = 1.99*10^-19J) #29. How much energy is required to remove an electron from one sodium atom? I know this question is just asking for wo...

JennyCKim1J

To interpret the results of photoelectric experiments the model of light needs to change from a ___ model to ___ model. What are the two missing words?

I thought the blanks should be waves & photon, but it's wrong. Anyone understand this question? What is the answer and why?

JennyCKim1J

For the equation Ek = (1/2)m*v^2, does ^2 apply to the whole equation ((1/2)m*v)^2 or just v (v^2)?

JennyCKim1J

Under Atomic Spectra, I wrote down "E = hv, ΔE = hv". What is the difference between the two equations? Is E equal to ΔE? When are these equations used?

JennyCKim1J

The acid H2A (where A stands for an unknown group of atoms) has molar mass 168 g mol 1. H2A reacts with the base XOH (molar mass 125 g mol -1) to produce H2O and the salt X2A. In one experiment, 1.20 g of H2A reacts with 1.00 g of XOH to form 0.985 g of X2A. What is the percentage yield of the react...

JennyCKim1J

The camel stores the fat tristearin, C57H110O6, in its hump. As well as being a source of energy, the fat is also a source of water because, when it is used, the reaction 2 C57H110O6(s) + 163 O2(g) -> 114 CO2(g) + 110H2O(l) takes place. What mass of oxygen is needed to oxidize this amount of trister...

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