CHEMISTRY COMMUNITY

Angel Gomez 1K

You can also think of the reducing agent as the one that is being oxidized.

Angel Gomez 1K

When writing more than one R, do we have to denote them differently? For example, would we use R, R', R''...

Angel Gomez 1K

Yes, these will be the axes b/c it will result in a straight line with a negative slope. The slope of the line is equal to the activation energy/R. You can think of it as being in the slope-intercept form y=mx+b

Angel Gomez 1K

For our test, I think we'll have to reverse the half reaction of the anode (where oxidation occurs) to get a cell potential that will result in a positive value.

Angel Gomez 1K

Can someone explain why the deltaH was multiplied by 2 mols?

Angel Gomez 1K

An elementary step's rate law must agree with the observed rate law of the overall reaction. The step whose rate law agrees is going to be the slowest step.

Angel Gomez 1K

Would you mind posting the question? It'd be easier on us so that we don't have to refer to it

Angel Gomez 1K

given the balanced equation: NaN3 --> 3N2+2Na

Can someone explain how N is oxidized? The solution explains it in the screenshot I attached, but uses a notation I'm not familiar with. Explanation?

Angel Gomez 1K

Yes, that is correct. You can assume pressure is 1 atm and then plug in values for delta V to check. If you compress something, Vf-Vi will be negative, so the two negative signs will combine to make a positive value. Delta V is positive for expansion, so the value will end up being negative.

Angel Gomez 1K

When Lavelle started lecturing on reaction mechanisms, he gave the equation A+B+C–>P He said that if the initial concentrations of both B and C were a lot greater than the initial concentration of A, then the rate=k' [A]^{n} since B and C remain essentially constant. I'm confused as to why we are us...

Angel Gomez 1K

If we calculate a standard potential and the value comes out to be negative, does that mean that it's not a galvanic cell? If not, then what type of cell is it?

Angel Gomez 1K

I believe that the simplified equation of E=Enot-RT/nF*lnQ, which is E=Enot-0.00591/n * log Q, is given to us specifically so that we don't have to plug in values for T, since it's simplified for use under STP.

Angel Gomez 1K

Wouldn't it depend on what your initial concentrations are? I would think that if you start with more products, they would decrease over time, and your rate for the reverse rxn would be (-) negative. Is this correct?

Angel Gomez 1K

If you notice, the inert electrodes are usually denoted as solids by (s), as most metals are solid at STP, and they have conductive properties, which is why they're useful as inert electrodes. There are exceptions, though. For ex, mercury is a liquid at STP, so it'd be written as Hg(l) in the cell d...

Angel Gomez 1K

You say that k varies depending on activation energy and temperature, but how exactly would we go about calculating the value of k?

Angel Gomez 1K

To explain why we compare initial rates, we can refer to the following equation that Lavelle used in class: NH_{4}^{+}(aq)+NO_{2}^{-}(aq)\rightarrow N_{2}(g)+H_{2}O(l)) Since N2 is a gas, it leaves the solution. As a result the reverse reaction is less likely to o...

Angel Gomez 1K

Sorry. The fourth letter should have been
d) $\Delta S_{total}$

Angel Gomez 1K

How would you go about answering the following question? Under what conditions, if any, does the sign of each of the following quantities provide a criterion for assessing the spontaneity of a reaction? (a) \Delta G^{\circ}< 0 ; (b) \Delta H^{\circ} ; (c) \Delta S^{\circ} ; (d) \Delta S^{\circ}

Angel Gomez 1K

The book defines bulk matter as "matter composed of large numbers of atoms." It probably means everyday objects like a piece of wood.

Angel Gomez 1K

Would you mind explaining why enthalpy can be measured as an amount altogether but entropy can only be measured by the changes in it?

Angel Gomez 1K

Because the entropy lost by the reaction goes to the surroundings, and the surroundings are gaining the entropy, this means that the entropy gained by the surroundings is equal to that lost by the reaction. If the entropy for the reaction decreased by 1 J/K (-1 J/K), for example, then the entropy of...

Angel Gomez 1K

I also don't understand this question. Are we supposed to convert the grams of water to moles and use the molar heat capacity instead? I see that it says constant pressure, and that almost lead me to believe that I needed to use 5/2R for heat capacity. However, given that it's a liquid, doesn't that...

Angel Gomez 1K

By definition, an ideal gas is a gas made of point particles (zero dimensional/no volume particles). Therefore, treating any real gas as an ideal gas is always an approximation. While the approximation is closer for monatomic gases (He, Ne, etc.), we can apply it to any real gas. The heat capacity t...

Angel Gomez 1K

I'm not sure Lavelle has covered this in lecture, but I would say that polarity has nothing to do bond enthalpies.

Angel Gomez 1K

To add to the above response, you can also consider heat capacity vs. specific heat capacity. The heat capacity of a bomb calorimeter, for example, does not depend on the amount of substance because it is a defined object. It has a specified mass for which to measure it's heat capacity, and we canno...

Angel Gomez 1K

When you are measuring the change in heat, or \Delta H , of an ideal gas at constant volume, the specific heat will be equal to 3/2 times the ideal gas constant. Here is the equation: C_{V}=3/2*R Therefore, when measuring \Delta H , you replace C_{V} with 3/2*R in your \Delta H=mC_{V}\Delta T equati...

Angel Gomez 1K

Typically, you will determine if you need to use J or kJ based on the question. The question may give you a value in kJ, but it can still ask for your answer to use J instead, and vice versa, so all you'd need to do is make the conversion.

Angel Gomez 1K

The standard heat of combustion will always be negative since the reaction will be giving off heat as it breaks the chemical bonds. The heat of formation should always be positive since it will be taking in heat in order to produce the chemical bonds. They can be related to one another by using the ...

Angel Gomez 1K

Isn't the equation for finding change in heat as follows: $\Delta H=q=mC\Delta T$
I know that the m accounts for mass instead of moles(which is usually represented as n), so would we simply switch out the m for n if we are presented with molar heat capacity?

Angel Gomez 1K

If you were given the concentrations to both products and reactants, you would first need to find Q, which is given by [P]/[R]. Given a value for Kc, you would need to compare Q to Kc and see if it is greater than or less than. If Q is greater, then that means that the reaction would shift toward th...

Angel Gomez 1K

Oxidation numbers are the total sum of ionic charges for a compound. For example, if we were looking at water, H20, we can see that it has two elements that compose it: 1) hydrogen, which is usually found as H+, so it has a positive charge of one and 2)oxygen, which is usually found as O 2- . If you...

Angel Gomez 1K

Amphoteric refers to the ability of X, a compound, to act as both a base and an acid. For example, in the chemical equation H_{2}O(l)+H_{2}O(l)\rightarrow H_{3}O^{+}(aq)+OH^{-}(aq) , water acts as both an acid (whose conjugate base is hydroxide, OH-) and as a base (wh...

Angel Gomez 1K

Lewis structures are used to model the chemical bonds between two or more elements regardless of what block they are in. Lewis models use the valance electrons(v.e-) of elements to visualize the bonds because the v.e- are in the outermost shell, and it wouldn't make sense for elements to bond with e...

Angel Gomez 1K

Transition metals are those elements in the d-Block that consists entirely of metals. Those metals always form cations (ions with a positive charge) and the charges in the metals will vary. The reason they all form cations is because transition metals have relatively low ionization energies, so an e...

Angel Gomez 1K

Can someone explain the difference between the Lyman and Blamer series to me? I couldn't really determine the difference when looking at the graphs Lavelle showed us during lecture. Fundamental difference would be great, and further detail would be much appreciated!

Angel Gomez 1K

Different elements have different characteristics, so the energy at the ground state of an electron (e-) for Hydrogen (H) is going to be different than the energy for the ground state of an e- of Helium (He), for example. The energy for a hydrogen e- at the ground state is 2.178 x 10^-20 Joules (J),...

CHEMISTRY COMMUNITY

Search found 36 matches

Re: Friday Section Test 2

Re: The symbol R

Re: Arrhenius Graph

Re: Using Appendix 2A

Standard enthalpy change

Re: Elementary Reaction

Re: Test 2 #5a

Notation question

Re: Sign for compression vs expansion

Please explain k'

Re: Galvanic Cells

Re: Standard State with Nernst Equation

Re: signs

Re: Cell Diagrams [ENDORSED]

Re: Rate Constant K [ENDORSED]

Re: Initial rates

Re: Criterion for Assessing Spontaneity of a Reaction

Criterion for Assessing Spontaneity of a Reaction

Re: Bulk Matter

Re: Enthalpy vs. Entropy

Re: entropy to surroundings

Re: 9.43

Re: Question about equation?

Re: bond enthalpy [ENDORSED]

Re: Extensive/Intensive Property [ENDORSED]

Re: Cv vs. R

Re: J vs. kJ [ENDORSED]

Re: standard heat of combustion vs. standard heat of formation

Re: ∆H equation

Re: X in ICE table

Re: Oxidation Numbers

Re: Amphoteric vs amphiprotic

Re: S and P blocks and Lewis structures [ENDORSED]

Re: Transition Metals

Lyman Series v Balmer series

Re: why is Bohr Frequency equation negative