CHEMISTRY COMMUNITY

Luke Bricca 1H

Awesome, thank you. I just looked back at my notes and it was in there, so I guess I must've missed it.

Luke Bricca 1H

In this question it asks us to draw a proposed structure for the activated complex of a chemical reaction. What is this and was it covered in class?

Luke Bricca 1H

In the solutions manual, the answer has a -0.59 added to the right side of the Arrhenius equation, and I was wondering where that came from?

Luke Bricca 1H

Usually the question tells you if a reaction is first, second, or zero order, but if you need to calculate it you can by comparing the rates of separate equations and how reactant concentrations change with them. You use the differential rate law when determining a rate of an equation (either a gene...

Luke Bricca 1H

The coefficient being 2 doesn't necessarily mean that A is second order. Order is determined by how the rate reacts to changes in reactant concentration, and the coefficient isn't used in determining that. A coefficient could be helpful if [B] or [C] was given and you needed to convert a final conce...

Luke Bricca 1H

Temperature is used to find k on the tables listed, but since in the problem you're already given k, the temperature given is not used in the problem.

Luke Bricca 1H

A secondary inert conductor that shows up in the HW for ch 14 fairly often is graphite, or C(s), which would also be good to familiarize yourself with.

Luke Bricca 1H

My TA also said these types of problems most likely won't be on any test since they're not in the homework and not in the class notes.

Luke Bricca 1H

You can assume that the initial concentration equals 1 and the final concentration you're looking for equals 0.15 when solving the half-life equation for time.

Luke Bricca 1H

Both can be used; if you look on the equations sheet it gives both equations as well as the conversion between ln and log.

Luke Bricca 1H

Furthermore, you could also solve the Nernst equation for K which would show its sign. This would be more work and is inefficient but guarantees a correct answer.

Luke Bricca 1H

When is it appropriate to use Pt(s) or another metal like C(s) to border a cell diagram?

Luke Bricca 1H

Specifically, the concept of "reaction coupling" is found often in nature where processes such as the oxidation of ATP drive other processes that require reduction within the body. In these cases, the oxidation reaction provides the energy required for the reduction reaction.

Luke Bricca 1H

Usually Gibbs Free Energy is given in kJ/mol, but you can multiply out the moles and just have kJ. By multiplying the Gibbs Free Energy by the number of moles, you're cancelling them in the denominator.

Luke Bricca 1H

In a redox reaction, a transfer of electrons is shown, which often requires H+ ions to show. In redox reactions containing acids and bases, H2O is a likely product.

Luke Bricca 1H

In an isothermal process, the internal temperature remains constant and the internal energy of an ideal gas is independent of its volume and pressure. Therefore, the internal energy of an ideal gas is wholly reliant on its temperature which is unchanging, so the delta U is unchanging as well, equall...

Luke Bricca 1H

Entropy is a state function and therefore changes in entropy can be calculated separately and then added together. For your question, a question would state that there was a change in temperature as well as a change in volume and ask for the final entropy of the system. To calculate this, you can us...

Luke Bricca 1H

Standard state refers to the standard temperature and pressure of a substance, and altering either affects both entropy and enthalpy if you look at the equations used to calculate both.

Luke Bricca 1H

To add to this, residual entropy is the difference in entropy between a non-equilibrium state system and a system near absolute zero (where the entropy should theoretically be zero.)

Luke Bricca 1H

Furthermore, absolute entropy is measured on an absolute scale and relates to the third law of thermodynamics.

Luke Bricca 1H

Additionally, in connection with Gibbs free energy, if the sign of the delta G is negative, the reaction is spontaneous and favorable.

Luke Bricca 1H

It's probably best to understand the reasons behind the derivations we learned in class as the logic used when deriving each equation could be helpful on a conceptual question on a future test or midterm, but I agree with the post above in that I think it's super unlikely we'll need to derive any eq...

Luke Bricca 1H

To add onto this using gasses as an example, P external must be used because work is achieved through expansion or compression against a constant external pressure or force, not against the internal pressure of the system.

Luke Bricca 1H

An adiabatic system is also an insulated system where there is no heat flow, so q=0.

Luke Bricca 1H

Bond enthalpies are the specific quantities of energy needed to break or form a bond between two atoms (ex: C--C or C--H). Bond enthalpies can be summed (since enthalpy is a state property) to find the total enthalpy of a reaction. Enthalpies of formation are the standard reaction enthalpies require...

Luke Bricca 1H

Both of your answers are right, and I'm sure on the test it'll specify which units we're supposed to use. Usually enthalpy is given in kJ/mol, but not always.

Luke Bricca 1H

In addition, if the problem instead wanted the final phase to be steam, another phase change would be required, adding a third step to your calculations. For any phase change problem, the work can be chunked into sections: energy required to raise temp to 0 deg C, energy for fusion phase change, ene...

Luke Bricca 1H

For question 8.45 part b, why is the enthalpy value found divided by the 4 moles of CS2? I know that the standard enthalpy of formation is per one mole formed of the product, but in the reaction there are 4 moles of carbon used to form 4 moles of CS2, so shouldn't the ratio be 1:1 and therefore the ...

Luke Bricca 1H

Follow up question: what is the triple point on a phase change diagram? In its definition it says that it's when all three phases of a substance "coexist in thermodynamic equilibrium," but what does that mean?

Luke Bricca 1H

It takes far more energy to excite liquid water molecules and break the bonds between them to cause vaporization than to break the crystalline-structured bonds between water molecules found in ice so the heating curve is much longer for vaporization.

CHEMISTRY COMMUNITY

Search found 30 matches

Re: 15.85

15.85

15.63

Re: Differential vs Integrated

Re: 15.23C

Re: Temperature Signifcance

Re: Inert Conductors [ENDORSED]

Re: Non-integer orders [ENDORSED]

Re: 15.27

Re: Picking between the different applications of the Nernst Equation

Re: 14.31

When to include Pt in cell diagram

Re: Nature

Re: Units for Gibbs Free Energy

Re: Balancing Redox Reactions

Re: isothermal expansion

Re: Isothermal and Isovolumetric Calculations [ENDORSED]

Re: Standard State

Re: Residual Entropy

Re: Absolute and statistical entropy

Re: sign of entropy

Re: Reversible isothermal expansion

Re: Pressure Internal vs. External

Re: Adiabatic system

Re: Enthalpy

Re: 8.37

Re: 8.39

HW 8.45 (b)

Re: Sublimation

Re: Heat Curve of Water