CHEMISTRY COMMUNITY

MCracchiolo 1C

Can this be explained conceptually?

MCracchiolo 1C

Why is the standard Gibbs Free Energy of the vaporization of water at 100C 0?

MCracchiolo 1C

In question 15.63, why do we need to subtract 0.59 and where does this value come from?

MCracchiolo 1C

Would someone be able to explain why 15.67 uses the ratio of activation energies? i.e. How would I have known to substitute Ea(cat) without looking at the solution manual?

MCracchiolo 1C

In lecture on Friday (I believe), Lavelle discussed how the reaction between NO2 and CO in a series of steps in order to determine the rate law. The rate law was determined by the slow step of NO2 and NO2 reacting giving the rate law of k[NO2]^2.... if the slow step had been the reaction between NO3...

MCracchiolo 1C

The overall reaction order would be a fraction if changing the concentration of one reactant did not change the rate by a factor of 2 or 4. Similarly, the reaction order can be negative if increasing the concentration of a reactant decreases the rate instead of increasing it.

MCracchiolo 1C

For part c) you should see that 8.7=(1.25)(1.25)^2(1.25)^2 *k with each concentration being in mol/L if you use experiment 1... thus, k must have the units L^4*mol^-4*s^-1 in order to cancel with (mol/L)*(mol/L)^2*(mol/L)^2

MCracchiolo 1C

For question 14.17, "Write balanced half-reactions for the redox reaction of an acidified solution of potassium permanganate and iron (II) chloride" ... How do you know which half reactions you are supposed to be using?

MCracchiolo 1C

In question 14.15 part C, why is KOH added to the cell diagram?

MCracchiolo 1C

Even if the overall charge is neutral?

MCracchiolo 1C

In question 14.15, in the final cell diagram answer, why aren't Ag(s) and AgBr(s) separated by a comma even though they are in the same state?

MCracchiolo 1C

Do elements have oxidation numbers when it's just, for example, O2 or O3?

MCracchiolo 1C

In example 8.6 in chapter 8, to calculate the internal energy at constant pressure, why do you have to calculate it in two steps - heating to the final temperature at constant volume, followed by isothermal expansion?

MCracchiolo 1C

Why is the Gibbs Free Energy at 100 (degrees C) for the vaporization of water, zero?

MCracchiolo 1C

What is residual entropy and what is a trans-isomer?

MCracchiolo 1C

When calculating problems that involve DeltaS and DeltaH, if you multiply the standard enthalpies of formation or standard molar entropies by the number of moles in the balanced chemical equation, why are your answers still in kJ/mol and J/(K*mol)?

MCracchiolo 1C

How do the strengths of intermolecular forces affect Gibbs Free Energy?

MCracchiolo 1C

Section 9.8 states that a net increase in the amount of gas usually results in a positive entropy change. Is there ever a situation where that is not the case?

MCracchiolo 1C

Would someone be able to explain figure 9.9 in section 9.6 that describes a particle in a box?

MCracchiolo 1C

It goes along with the same concept of q(system)=-q(surroundings) where the heat released by one system must be absorbed by something else and vice versa

MCracchiolo 1C

Reversible: (One that can be reversed by an infinitesimally small change in variable; i.e. the example where the internal and external pressure of a gas inside a container are equal and a slight change in either would force the piston in one direction or another) Irreversible: (Work done against a c...

MCracchiolo 1C

The concept of P is the inverse of V comes from Boyle's Law, "For a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional."

Meaning, P(1)V(1)=P(2)V(2)

MCracchiolo 1C

Chapter 9 states, "This independence means that, if we want to calculate the entropy difference between a pair of states joined by an irreversible path, we can look for a reversible path between the same two states and then use Eq. 1 for that path." What is meant by a reversible path compa...

MCracchiolo 1C

On the Formula Sheet, C(p) and C(v) are listed as (5/2)R and (3/2)R respectively, but in the book, those equations are only for atoms. If we are given an ideal gas such as O2(g)...Do we have to know that linear molecules are C(p)=(7/2)R and C(v)=(5/2)? Or for the tests, is it okay if we use the form...

MCracchiolo 1C

What is the difference between S(s), rhombic and S(s), monoclinic?

MCracchiolo 1C

In the solution manual for 8.99, the calculated reaction enthalpy is found by the equation Delta H (RXN) = -153.89 +2(-167.16)-2(-167.16)-0 = -153.89 kJ/mol ...but the balanced chemical equation is 2HCl(aq)+Zn(s) --> H2(g)+ZnCl2(aq) Shouldn't the standard enthalpy of formation for H2 gas be 0? And w...

MCracchiolo 1C

For question 8.13, "In a combustion cylinder, the total energy change produced from the burning of a fuel is -2573 kJ. The cooling system that surrounds the cylinder absorbs 947 kJ as heat. How much work can be done by the fuel in the cylinder?" The answer, 1626 kJ...Is that the amount of ...

MCracchiolo 1C

In question 8.27, I got to the point of 2.23 L*atm for work, but in the solution manual, where does the 101.325 J*L-1*atm-1 come from?

MCracchiolo 1C

How do I know when my units should be in kJ or in kJ*mol^-1?

MCracchiolo 1C

In question 67, part b, the bond enthalpies are listed for O2 and H2, but how do I account for the contribution of carbon as graphite when calculating?

MCracchiolo 1C

When trying to calculate the standard enthalpy of formation for a compound, I understand you use the reactants in their most stable forms, but how do I know whether the product formed is in the right state?

MCracchiolo 1C

How does energy density affect the efficiency of a fuel and for example, how far a car can drive?

MCracchiolo 1C

What is the difference between the standard enthalpy of formation and the standard reaction enthalpy?

MCracchiolo 1C

What is the difference between non expansion work and expansion work, and what does it mean when the book says "at constant volume and no non expansion work" where the change in internal energy is equal to q?

MCracchiolo 1C

Oh! So 4 regions of electron density or sp^3 for example would still be tetrahedral?

MCracchiolo 1C

If we are given a coordination compound with a coordination number less than 6, do we assume we can add complexes to the central metal until we reach a coordination number of 6?

MCracchiolo 1C

What is the key to knowing if an oxide is acidic or basic?

MCracchiolo 1C

How do I write a net ionic equation?

MCracchiolo 1C

In my textbook on pg. 118, (in Chapter 4), figure 4.7 gives examples of polar vs. non polar molecules based on their VSEPR shapes... BrF3 is listed under AX3 as non polar, but seeing that BrF3 has a total of 28 valence electrons to use for the Lewis Structure, the central Br atom should have two lon...

MCracchiolo 1C

What does K(p) have to be in terms of? bar?

MCracchiolo 1C

Even though K and Q do not have units, do the values you use to calculate K and Q need to be in specific units, say, (mol*L^-1)?

MCracchiolo 1C

When using ICE tables to calculate concentrations, do we have to factor in the number of moles of each species. If so, when do those coefficients factor into the calculations?

MCracchiolo 1C

After deducing that CH4O is sp^3 tetrahedral, how do I know whether or not the compound is polar?

MCracchiolo 1C

When looking at the sigma and pi bonds of CH2=CHCHO, how do you know which orbitals are hybridized and which aren't such as in the case of the C-H bond where the sigma bond is (C2sp^2, H1s)?

MCracchiolo 1C

How do I measure the bond angles of hybridized orbitals?

MCracchiolo 1C

On Question 17.37, parts (c) and (d) contain the symbols (edta) and (en) within the chemical formula. What do these mean and how do I know that edta is hexadentate and en is bidentate?

MCracchiolo 1C

When writing the equilibrium expressions for fully dissociated ionic compounds, the book says to use the net ionic equation...Would someone be able to write the steps to finding the net ionic equation as a refresher from high school chem?

MCracchiolo 1C

In Section 11.2 of the book, when calculating the equilibrium constant, K, the authors use the terminology "activities" to describe the general expression for the equilibrium constant. Can we ignore this fact because we are assuming our gases are ideal gases and not real gases? Are "a...

MCracchiolo 1C

What information can you deduce from knowing the coordination number? Why is it important?

MCracchiolo 1C

What is the difference between talking about localized bonds with regard to Valence-Bond Theory and delocalized bonds in Molecular Orbital Theory?

MCracchiolo 1C

What is the general definition and significance of the coordination sphere with transition metals?

MCracchiolo 1C

When using VSEPR and Lewis structures to describe radicals, is a lone electron treated as its own region of electron density? How does a lone electron affect the shape?

MCracchiolo 1C

Do structures such as that for ONF have resonance even though the atoms bonded to the central atom (N) are not the same?

MCracchiolo 1C

For group 13, would someone be able to explain the reasoning behind the elements forming 3+ ions in the context of their electron configurations? Thank you!

MCracchiolo 1C

Looking for an explanation for the steps in problem M19 as you go from the grams of product to the formula of the reactant. Thank you!

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