CHEMISTRY COMMUNITY

Dakota_Campbell_1C

Where does the 0.693 come from in the half life equation for first order reactions. Will that value ever change? I just want to know where it comes from and why we use it.

Dakota_Campbell_1C

In self test 15.4B, it tells you that the order is not an integer. If this is the case how do you determine this and what rate order expression do you use?

Dakota_Campbell_1C

Do Catalysts change the reaction mechanism? Since something new is being added into the chemical equation does that mean there will be entirely new intermediates?

Dakota_Campbell_1C

Why is the rate determining step always the slowest reaction

Dakota_Campbell_1C

I don't understand how the slope of the tangent line is significant to finding a true rate if the rate is exponentially reaching a plateau.

Dakota_Campbell_1C

In lecture Lavelle had a graph that had ln[A] on the Y axis and time on the X axis. I was confused to see that the plot for the graph was linear. Why is it linear if the graph of ln is exponential?

Dakota_Campbell_1C

When calculating the delta H why do we do the delta H products minus reactants oppose to just using the sum of the enthalpies like the questions previously. Like in questions 4J.5 we just use the products delta H when finding Gibbs.

Dakota_Campbell_1C

In the shorthand notation for the redox reactions, the textbook says that the double verticle line represents the salt bridge. What is a salt bridge and what is its importance to a Galvanic cell

Dakota_Campbell_1C

I understand that there was an error in the textbook, however, the answer in the solutions manual doesn't make sense, why for one of the answers does it include the electrons and in the other answer, the coefficients are missing?

Dakota_Campbell_1C

Is the amount of chemical change proportional to the amount of current passed?

Dakota_Campbell_1C

The problem asks for both the reduction and oxidation half reaction. For the oxidation reaction I got 6e+14H+Cr2O7^2- -----> 2Cr^3+ +7H2O.
But for some reason, I am confused about how to write the reduction half-reaction because of the H+ and the C2H5OH

Dakota_Campbell_1C

Will we be expected to know all of the oxidation numbers for all the elements or will we be given a table? If we are expected to know is there some kind of shorthand or way of figuring them out?

Dakota_Campbell_1C

What is the difference between an intensive property and extensive property and why are specific heat capacity and specific heat capacity them respectively?

Dakota_Campbell_1C

In problem 4B in Lydon's midterm review packet when we added up both sides of the reaction we subtracted the reactant side from the product side when we generally do the opposite. Why was this problem an exception?

Dakota_Campbell_1C

Why do we calculate separate reaction entropies and why is that final accurate? For example in question 5 of Lydon's review packet we did 3 separate change in entropy equations then added them to get the final answer. I guess what I'm not understanding is how is the sum of those entropies an accurat...

Dakota_Campbell_1C

When solving for degeneracy when is W equal to 0. There was a problem on the Midterm that I had seemed to misinterpret.

Dakota_Campbell_1C

When calculating the overall enthalpy, particularly with the bond enthalpy problems will the bond energies always be given to us and if not how do we calculate them?

Dakota_Campbell_1C

For part A, when solving for change in enthalpy why do we place a negative in front of energy transferred as heat (q)?

Dakota_Campbell_1C

What is the point of an Isolated system? If no matter or heat can leave or enter the system and the heat and mass stay constant what would be the interest in using an Isolated system?

Dakota_Campbell_1C

Lavelle did a chemical potential energy problem, where he took the delta H of all the bonds on both sides of the reaction. He mentioned how there was a short cut to the method where you didn't have to calculate the energy of each bond what was that short cut?

Dakota_Campbell_1C

What's the difference between enthalpy and entropy? Entropy is the measure of gain or loss of heat. Entropy is the measure of chaos, but what does that mean and does it have units?

Dakota_Campbell_1C

What does exergonic mean in terms of Gibbs free energy. How does it determine spontaneity?

Dakota_Campbell_1C

When doing ice box problems what are you supposed to do with the coefficient in front of a molecule? do you add it to the change or do you multiply? Also when you are adding Mols to the equation do you change it for the base equation?

Dakota_Campbell_1C

What is the 5% rule and how does it relate to the ICE box?

Dakota_Campbell_1C

Pressure and Volume have a inverse relationship. Thus if you pump an inert gas into a system at equilibrium you are increasing the pressure you are lessening volume which leads to the reaction favoring the side of the reaction with a lower concentration.

Dakota_Campbell_1C

Why does the KA and KB value have to add up to 10x^14?

Dakota_Campbell_1C

When is it appropriate to use the quadratic equation when solving for the ICE box. In lecture lavelle was completing a problem and let us know that the quadratic equation wasnt needed why is this and when is it needed.

Dakota_Campbell_1C

In lecture we did the calculations for Kw, I am unsure what the significance of this constant is. I thought that water was not an important part of equilibrium, why do we calculate a constant for it and what is it used for?

Dakota_Campbell_1C

In regards to calculating K, the values that are inputted into the equation are concentrations or partial pressures whereas when Calculating Q the values inputted are initial values not equilibrium values.

Dakota_Campbell_1C

If K is the equilibrium constant, or the rate at which both the forward and reverse reaction are happening simultaneously. What is the Q value and what is its significance in determining whether the products or the reactants are going to be favoured?

Dakota_Campbell_1C

Why is Oxalate bidentate? It seems that all four of the oxygens are able to donate an electron pair I am confused by why it is considered bidentate.

Dakota_Campbell_1C

What is a polydentate would it be just an anion that has more than 4 bonding sites? Can someone give an explanation and example?

Dakota_Campbell_1C

On problem 9C3 part d), My final answer was [Fe(C2O4)2(H2O)2]Na while the book answer was Na[Fe(OH2)2(C2O4)2] will it matter on the exam if the aqua is written as H2O or OH2? Is one answer more right than the other? If so can someone please explain!

Dakota_Campbell_1C

Is it safe to assume that any covalently bonded molecule with a lone pair on the central atom will be polar? How can polarity be determined with larger molecules in class Lavelle usually draws arrows to demonstrate what direction the positive and negative poles are at how is this determined.

Dakota_Campbell_1C

Why do the lone pairs on the central atom have more repulsion than all of the valence electrons on the other atoms of the molecule? Why do the lone pairs on the central atom dictate shape.

Dakota_Campbell_1C

usually you can figure out the amount of pi and sigma bonds assuming every first bond is a sigma bond and every bond after that is a pi bond. So in a triple bond the first of three would be a sigma and the other two would have to be pi

Dakota_Campbell_1C

what is the significance of molecules that have just one electron on the central atom not a lone pair. How does that affect the shape?

Dakota_Campbell_1C

Do we need to know how to write the ground state configuration for the hybridized molecules? If what is the logic behind writing them. Like the ground state sp^4d. Im just lost

Dakota_Campbell_1C

The question doesn't specify how many lone pairs there can be on the central atom, it only says "one or more lone pairs". After doing some research online, apparently a AX2E3 molecule will give a bond angle of 180 degrees.

Dakota_Campbell_1C

The reading says that you can identify the pi bonds by the number of nodal planes, how are you supposed to know how many nodal planes there are in a molecule is there a better way to figure it out?

Dakota_Campbell_1C

Is it fair to say that if there is a lone pair on the central atom that the molecule is going to be polar? Most of the examples I'm seeing demonstrate this point? Will there be more electron density there, therefore, repelling the other atoms creating a dipole.

Dakota_Campbell_1C

For the E in the vesper formula does that take in account only the lone pairs of electrons on the central atom or in the whole structure.

Dakota_Campbell_1C

When estimating bond length from Lewis structure would a very electronegative and low electronegative atom have a shorter bond than two very electronegative atoms? Is there a trend in missing.

Dakota_Campbell_1C

For Cr and Cu what is the exception and what does it mean? from what I understand you take from the S orbital and give to the D?

Dakota_Campbell_1C

I don't understand what it means by dominant. How are you supposed to tell what structure is dominant over the other one?

Dakota_Campbell_1C

What is the explanation behind the Pauli exclusion principle?

Dakota_Campbell_1C

Why is it that we can only know the measurement of either the position or momentum at a given time? I don't understand the idea behind this equation.

Dakota_Campbell_1C

In the lecture, we went over that l=n-1 but it also says that it can be anything lower than n. Why is this, and when do we stick to n-1?

Dakota_Campbell_1C

Thank You!

Dakota_Campbell_1C

In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series (for example, Balmer series, Lyman series, Paschen series), as shown in Figs. 1.10 and 2.1. What is common to the lines within a series that makes grouping them together logical? Having troub...

Dakota_Campbell_1C

Once you've found the energy you can use the formula λ=(hc)/E to find wavelength.

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