CHEMISTRY COMMUNITY

Daniisaacson2F

I had the same question, I'm wondering how they were able to derive that from the arrhenius equation

Daniisaacson2F

Just use the integrated rate laws that he gives on the equation sheet!

Daniisaacson2F

For zero order, that just means that the concentration of that reactant does not affect the rate of the reaction. That can be seen in the problems where you compare the concentrations and rate constants of different reactions to find their orders; if it is zero order, then changing the concentration...

Daniisaacson2F

Yes, k prime if the reverse reaction's rate constant. You can use that and the forward reaction's k to figure out the equilibrium constant, K.

Daniisaacson2F

For problems 17 and 19, it is confusing to know which units to use, but you should probably keep it consistent with what they give you unless you need to convert (eg. seconds to hours).

Daniisaacson2F

Coefficients do not determine the order of the reaction, they just matter when it says the concentration of the products vs reactants and you have to multiply by a coefficient to keep the rate consistent.

Daniisaacson2F

I would just keep the units of the answer the same units that they give you, I know that sometimes they change the units interchangeably from minutes and seconds and as long as the answers are consistent with each other I believe its ok.

Daniisaacson2F

Like they said, a half life is the time it takes for half of the concentration of the specific reaction to deplete by 50%, and the rate is just how fast it depletes throughout the reaction.

Daniisaacson2F

It depends which order you are talking about. For a first order reaction, the linear graph is the graph of ln[A] vs time, and the curved graph is just concentration vs time.

Daniisaacson2F

You just add up each order of the reactants to find total order.

Daniisaacson2F

In the problems that they are giving in the homework, they are treating Q as if it was K, and using that value to determine whether the reactants or products are favored. In other words, they usually will not give you a K value to compare it to.

Daniisaacson2F

Yes, you use it under nonstandard conditions, such as a change in the molarities (not 1M like you said), a different temperature, pressure, etc.

Daniisaacson2F

Yes you can do it like that, but not all the time. In an electrolytic cell, the potential is supposed to be negative; so, if you did it like you said, then you would mix them up because you are solving for the standard potential to be negative. It is a more safe bet to look at the overall reaction a...

Daniisaacson2F

You can look at the overall reaction, and split it into 2 half reactions. For example, if one of the half reactions for the total equation is Cr3+ + 1e- -----> Cr2+, then here one electron is being transferred. However, if there are 2Cr3+ and Cr2+, then you know there are 2 electrons transferred bec...

Daniisaacson2F

They just took the Hydrogen off of the NO3-, then Nitrogen is reduced from 5+ charge to 2+ charge in NO.

Daniisaacson2F

What would be an example in this category that would be on the midterm?

Daniisaacson2F

Are the ions that flow from the cathode to the anode through the salt bridge cations or anions?

Daniisaacson2F

I would assume that the question he would ask would have to do with a temperature raise in the atmosphere (like how we use q=-q) but I doubt it will be covered on the exam.

Daniisaacson2F

Yes, you have to take into account the different ways that you can solve for deltaS. Since deltaG is the spontaneity of a reaction, it depends on S so it also depends on pressure and volume.

Daniisaacson2F

If deltaS is the disorder (for use of a better word) or a reaction, how is that different than delta G?

Daniisaacson2F

I see what you're saying, and I think that it would be easier to just imagine what would make G negative (stated above). But for some of them, the reverse reaction will be the opposite sign of deltaG, changing whether or not it is spontaneous.

Daniisaacson2F

Along with that, qp=delta H only if the pressure is constant. Therefore, having the work be 0 with a system with constant pressure would result in the only thing changing the internal energy of the system be the change in heat.

Daniisaacson2F

It also depends what kind of system you are trying to increase the q on; you cannot add or remove a substance from a closed system because matter cannot be transferred. However, for a closed system, you can do work on it or change the temperature.

Daniisaacson2F

Q is not a state function because throughout a reaction, the heat changes; therefore, you cannot solve for q with qfinal-qinitial. With work, it is the same thing. The amount of work done on a system is not solved for just by the final and initial work.

Daniisaacson2F

You always just use what they give you for enthalpies, but heat capacity is definitely more specific. So yes, it does depend on whether the pressure/volume is constant for heat capacity.

Daniisaacson2F

I'm pretty sure it depends on whether work is being done by the system or on the system. I'm assuming if it was being done ON the system, it would be positive and vice versa.

Daniisaacson2F

In the textbook, they are only taking into account which specific bonds were broken and produced from the reactants to products. When I do these problems, I tend to write out all of the bonds and multiply by the number of them (it's easier for me), but wither way is fine.

Daniisaacson2F

Bond enthalpy is the energy needed to break a bond. In today's lecture, Lavelle was essentially trying to show us which bonds are broken in the specific reaction, and how you use the enthalpies from both the reactants and products to find the total change in enthalpy. Since there were bonds broken a...

Daniisaacson2F

Sometimes you have to convert the units given to you in order to do the calculation correctly. For example, the specific heat capacity and the heat of fusion have different units, so in order to get both of them to kJ, you have to cancel out the units in each equation to be converted to kJ.

Daniisaacson2F

The meaning of an exothermic reaction means that it gives off energy once completed, not that the reactants need to be spontaneous in order to do so.

CHEMISTRY COMMUNITY

Search found 30 matches

Re: 15.63

Re: The integrated rate laws

Re: Applications

Re: k' in Pseudo-First-Order Rate Laws

Re: Proper units

Re: Coefficients

Re: Units in 15.17 vs. 15.19

Re: half life vs rate

Re: Graphs in Lecture

Re: Overall order

Re: Q & K?

Re: Nernst equation usage

Re: Defining Cathodes and Anodes through standard cell potential

Re: calculating n

Re: Gold ring example

fossil fuels on midterm [ENDORSED]

cat/anions

Re: Environmental impact?

Re: Pressure and Volume on Spontaneity

Gibbs Free Energy [ENDORSED]

Re: Spontaneity of a reaction

Re: Internal Energy and Enthalpy [ENDORSED]

Re: Open System

Re: q isn't a state function

Re: Pressure in enthalpy vs heat capacity

Re: Work function

Re: Calculating enthalpy using bond energies [ENDORSED]

Re: What is bond enthalpy and can someone explain to me what Lavelle was doing with the Lewis Structures in today's lect

Re: Heating Curve: How is the kJ calculated?

Re: Exothermic Rxn