CHEMISTRY COMMUNITY

Mary Becerra 2D

When a rate law = k*([A]^3/[B]^-1), what does the negative power mean? I was thinking it was an inhibitor of some kind since it reduces the order of the reaction?

Mary Becerra 2D

In a calorimeter, since w = -PdeltaV and deltaV=0 and w=0 does that mean that P=0. Or does that imply that the change in P would be 0?

Mary Becerra 2D

In step 1 we find that the work done by the system is -158J. How can we make the conclusion that in step 2, our U = +158J? I thought that since there is no heat exchange, w=U.

Mary Becerra 2D

What exactly is a nucleophile? Also, can there be more than one nucleophile with molecule interactions?

Mary Becerra 2D

So I noticed a trend with the units of k, we keep dividing each one by M (molarity) i.e. zero order is k M/s, first order is k 1/s, second order is k 1/M.s. Does this trend continue for 3rd, 4th, and 5th orders?

Mary Becerra 2D

The concept part of it would be that there is an inverse relationship between the activation energy and the rate of a reaction: the lower the activation energy, the higher the rate of the reaction. A catalyst offers an alternative pathway with a lower activation energy, therefore, the reaction goes ...

Mary Becerra 2D

I noticed that in lecture we were given an experimentally determined rate law equal to k[NO2]^2 and made the connection that since the other reactant, CO, when not present in this given rate law it was of zero order. Can we always make this connection? Also, how would this look in a reaction with mo...

Mary Becerra 2D

Will the number of steps used in order to find the overall reaction equal the number of reactants? Are there any exceptions?

Mary Becerra 2D

What exactly is a pseudo 1st order rate law and how is it different from a normal 1st order rate law? It was mentioned in lecture on Friday and I don't fully understand the concept.

Mary Becerra 2D

With that example he gave in lecture, he drew a diagram showing that while graphite is at lower and a more stable energy, the activation energy required to turn diamond into graphite is too large for it to spontaneously happen (at least at standard conditions).

Mary Becerra 2D

If we have a hypothetical A ---> B E= 123, does that mean that B ---> A E= -123?

Mary Becerra 2D

I understand that aA's rate would be (-1/a)*(dA/dt). Does this mean 1/a*A's rate is (-a)*(dA/dt)? Thank you!

Mary Becerra 2D

Will "n" value in the Nernst Equation always just be the number of electrons used to balance the half reactions?

Mary Becerra 2D

How do we know when to balance the equation using basic or acidic methods? Is it possible to use both when balancing the same equation?

Mary Becerra 2D

I think there is a typo/error in #8.55. The solutions manual says to that the second reaction given (2Al + O2 ----> Al2O3) doesn't change its enthalpy value even though the book differs from the manual. Basically, the book says the second reaction is 2Al + O2 ----> Al2O3 while the solutions manual s...

Mary Becerra 2D

Why is it that when involved in an isothermal reversible expansion, the change in S of surroundings is equal to the opposite sign of the change in S of the system but when involved in an isothermal nonreversible free expansion, the change in S of surroundings is equal to zero?

Mary Becerra 2D

Side note: an easy way to remember that oxidation is the loss of e- and reduction is gain of e-, use OIL RIG. OIL = Oxidation Is Loss, RIG = Reduction Is Gain

Mary Becerra 2D

During the lecture on Monday, there was a graphic of two beakers with an electron flow filled with similar solution. What is this solution? I was assuming it is water but can it be any liquid?

Mary Becerra 2D

The perfect crystal is related to the third law of thermodynamics which is about systems in equilibrium at absolute zero (0 Kelvin). It states that the entropy of a perfect crystal at absolute zero is exactly equal to zero.

Mary Becerra 2D

Is there a periodic trend when it comes to heat capacities? If so, what is it and is this useful in making calculations?

Mary Becerra 2D

Do dense elements have a higher heat capacity than less dense elements? Also, does the heat capacity have more to do with density, atom structure, or bond energies?

Mary Becerra 2D

I know that when you increase the volume of a gas, you increase the entropy since the gas now has more positions available to it, however, is this the same with liquid? Or do you have to take gravity into account since that would limit its positions? For example, would entropy increase for a liquid ...

Mary Becerra 2D

The textbook (example 9.16) presents an example of an endothermic reaction becoming exothermic due to an increase in temperature. Is this the case for all endothermic processes? Or are there some cases where an increase in temperature will never make an endothermic process exothermic?

Mary Becerra 2D

In Friday's lecture, Lavelle had on is powerpoint, "In any spontaneous process there is an increase in entropy." Does this mean that in any non-spontaneous process there is a decrease in entropy?

Mary Becerra 2D

What makes a reaction reversible versus irreversible? Also, what relevance would this have when considering how to solve a problem with the condition of reversible/irreversible?

Mary Becerra 2D

Is there a difference between heat and thermal energy or can they be used interchangeably?

Mary Becerra 2D

Is there such a thing as a "perfect" isolated system? What I mean by that is a system where over an infinite amount of time, there is no exchange of heat or matter?

Mary Becerra 2D

Are there infinite forms of Hess's Law? All the problems I have encountered usually have between 2-4 chemical reactions to use, but is it possible to have more than that in one problem? Or are we limited to the number of reactions?

Mary Becerra 2D

Why can we equate delta H (heat transfer at constant pressure) and delta U (heat transfer at constant volume)?

Mary Becerra 2D

What is the difference between heat and enthalpy? From my understanding, enthalpy is the measurement of the change of heat after a reaction. Is this correct, wrong, or correct but too simplistic?

Mary Becerra 2D

Do we need to know the full name of en (ethylenediamine) or can we just put "en" when naming a compound? I've been told that we do but some people and we don't by others so I'm confused.

Mary Becerra 2D

One pattern I noticed was that the number of Nitrogens in a compound gave away whether it was mono, bi, etc. So 1 Nitrogen is mono, 2 Nitrogens is bi, etc. There may be acceptions but this is what I have noticed.

Mary Becerra 2D

How do you find pH when you are given/find a value of pOH? Is this when you use the formula pH = 14 - pOH?

Mary Becerra 2D

What does isoelectronic mean? It was #5D on the midterm. The question asked to choose the two ions that were not isoelectronic with fluoride ion (F-). I answered correctly with the ions O- and N2- but I do not fully understand the concept.

Mary Becerra 2D

Ni3+ is the Lewis Acid because it is the metal in this compound and metals are always the electron acceptors when they have ligands surrounding them.

Mary Becerra 2D

How can you tell when an atom is donating a proton versus an electron? Does it work as in when a proton is donating electrons it is always donating protons? Therefore a Lewis base is always a Bronsted acid?

Mary Becerra 2D

How can you tell when an atom is donating a proton versus an electron? Does it work as in when a proton is donating electrons it is always donating protons? Therefore a Lewis base is always a Bronsted acid?

Mary Becerra 2D

According to Le Chatelier's principle, the effect of temperature on equilibria involves a change in the equilibrium constant as well.

Mary Becerra 2D

The general rule is that the farther away the elements are, the more polar, and the closer they are, the more nonpolar.

Mary Becerra 2D

I understand that if the oxidation number of a compound is 2+ (for example) we will use the Roman Numerals (II) when we write out the name. If the oxidation number was negative, is there a way to indicate that when naming a compound? Would there be negative Roman numerals?

Mary Becerra 2D

Can there be two or more radicals in the same molecule? All previous examples we have used in class or discussion have only described one.

Mary Becerra 2D

Do you only use this equation when finding wavelengths of objects with mass? Also, is it still valid when the said object is not in motion?

Mary Becerra 2D

In a molecule, nonpolar atoms tend to have a low difference in electronegativity while polar atoms tend to have a high difference in electronegativity. Also, electrons in a nonpolar molecule are shared equally while electrons in a polar molecule are shared unequally, creating a dipolar moment.

Mary Becerra 2D

How do you know when the shape is bent when writing out a formation?

Mary Becerra 2D

How can many bonds at once be formed? does it only go up to triple bond?

Mary Becerra 2D

When constructing Lewis structures, how do you know which element to put in the middle?

Mary Becerra 2D

Also I just realized that I may have posted this in the wrong section, but I would still appreciate an answer. Thank you!

Mary Becerra 2D

During lecture, Lavelle mentioned that a double bond is shorter than a single bond. Can someone explain why this is?

Mary Becerra 2D

In order to find the speed, you must use the values given to you and plug it into the Heisenberg equation. The only value you should be missing is speed since for the momentum part of the equation is equal to (mass)(velocity). The rest of the equation is either constants or given to you in the equat...

Mary Becerra 2D

Oh, ok. That makes sense, thank you!

Mary Becerra 2D

In the periodic table, why doesn't the d block align its numbers with the s and p blocks? For example, the "4s" row directly leads into the "3d" row.

Mary Becerra 2D

But wouldn't you have to find the mass percentage composition in order to go through the next steps of dividing what you find by the smallest number and then finding out whether it is the empirical or molecular function?

Mary Becerra 2D

Personally, I would try to let the calculator do all the work and then round at the very end, so you get the most accurate answer possible.

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