CHEMISTRY COMMUNITY

Julia Cheng 2J

You would usually use delta S to find the change in entropy of a reaction (so some change to the system has to happen in order for there to be a delta S). We've only been using S to find the entropy of a molecule as a result of its structure (so there doesn't have to be any change in its state).

Julia Cheng 2J

Kind of... the calorimeter is a very specific type of surroundings though.

Julia Cheng 2J

Rachel N 1I wrote:Why is the contents of an ideal cooler at 3 deg Celsius considered isolated and not closed?

In an ideal cooler, no energy is exchanged with the surroundings (because ideally its contents will stay cold without absorbing warmth from the outside), so it's isolated.

Julia Cheng 2J

An intermediate is produced in an earlier step and then used in a later step. It isn't an intermediate if it is used in an early step and produced in a later step.

Julia Cheng 2J

Also, the greater the molecularity, the less likely the reaction is to happen since the probability of that many molecules colliding is less.

Julia Cheng 2J

In the slow step, we find the unique reaction rate according to the formation of products, which is equivalent to the overall rate law. So, we can set them equal.

Julia Cheng 2J

A pseudo first order reaction is actually a higher order reaction in which the concentrations of all the reactants except one is super high. This way, only the change in concentration of one reactant will be significant and you can solve for its concentration as if it was a real first order reaction.

Julia Cheng 2J

You can use the reaction to figure out order only if it is an elementary reaction.

Julia Cheng 2J

As long as the forward reaction is progressing faster than the reverse reaction, the rate of the change in concentration of reactants will be negative because they are being consumed.

Julia Cheng 2J

The more positive the reduction potential, the greater its ability to be reduced. Since the table is arranged in order of large to small reduction potential, it works out.

Julia Cheng 2J

For this problem, we know deltaG for Tl3+/Tl. However, for b we want to know the deltaG for Tl3+/Tl+ in order to find whether or not Tl is disproportionate. We use the reaction potential for Tl+/Tl to calculate deltaG for the half-reaction and then combine the deltaG's for Tl3+/Tl and Tl+/Tl in a He...

Julia Cheng 2J

They yield the same results though!

Julia Cheng 2J

To determine oxidation numbers, remember that the oxidation number of oxygen is always +2 unless you're looking at a peroxide (I think). Then you just determine the oxidation numbers of the rest of the atoms in the molecules based on the charge of the molecule. The oxidation numbers of all the atoms...

Julia Cheng 2J

I'm pretty sure the r stands for "reaction." So rather than this being a standard deltaG, this is the deltaG of the reaction and the number of moles of electrons in the reaction.

Julia Cheng 2J

It helps to write out all your units when you're doing a problem so you can see what cancels out for your final answer.

Julia Cheng 2J

Yes, a conducting metal/solid is necessary for electrons to be transferred between half-reactions.

Julia Cheng 2J

Yes; it uses spontaneous redox reactions to generate electrical energy.

Julia Cheng 2J

Just make sure that the number of electrons cancel out and the charges are balanced and you should be good to calculate the standard reaction potential by adding up E for each half reaction

Julia Cheng 2J

Keep in mind that the second law is referring to the total entropy, aka the entropy of the universe. So, the entropy of the system or of the surroundings can increase without violating the second law as long as the total entropy is not negative.

Julia Cheng 2J

For the equation deltaG=deltaH-TdeltaS, for a negative deltaH (exothermic), as long as the TdeltaS term is negative and larger in magnitude than deltaH, deltaG will be positive and the process will be endergonic.

Julia Cheng 2J

I believe that a trans isomer has a smaller W than its corresponding cis crystal. A trans isomer and its mirror across a certain axis are indistinguishable, but you can tell the difference between a cis crystal and its mirror, so the cis crystal has a greater W.

Julia Cheng 2J

S, G, and H change depending on the conditions. So, S, G, and H indicate spontaneity for whatever conditions they are given for in the problem.

Julia Cheng 2J

Isothermal just means that there's no change in temperature of the system, but there is still an exchange of heat between the system and the surroundings.

Julia Cheng 2J

Don't forget that when you are solving for enthalpy change for exothermic phase changes, you just use negative delta H for their endothermic counterparts.

Julia Cheng 2J

Also, q is zero in free expansion because no heat exchange occurs between the system and surroundings.

Julia Cheng 2J

If the system expands or is compressed, there can only be a change in the number of moles if the system is open.

Julia Cheng 2J

The system will always be wherever the reaction is occurring, and the surroundings are everything else.

Julia Cheng 2J

Reversible work is done very slowly and requires the maximum amount of energy.

Julia Cheng 2J

Yes, even for the same substance, its standard enthalpy of formation is different depending on what state it is in. On tests and in the textbook, the standard enthalpies of formation are given and specific to whatever physical state the molecule is in, so we have to pay attention to that.

Julia Cheng 2J

Since the internal energy of the gas is less, the molecules have less energy and experience fewer collisions with each other and the walls of the container. So, the temperature and pressure are less. I'm not sure, but with your answer, I believe that the flaw is that the pressure could be greater ev...

Julia Cheng 2J

The standard enthalpy of formation is 0 when the element is in its purest form. So even though water is in liquid form commonly, its standard enthalpy of formation is not 0 because it's not in its purest form.

CHEMISTRY COMMUNITY

Search found 31 matches

Re: S and delta S

Re: qreaction and qcalorimeter

Re: Open, closed, or isolated test 1 question

Re: Finding the intermediate(s)

Re: What is Molecularity?

Re: Pre-Equilibrium Approach Methodology

Re: Pseudo First Order Reaction

Re: Order of the Reaction [ENDORSED]

Re: Average rate [ENDORSED]

Re: Table 14.1

Re: 14.33b homework

Re: ln vs log [ENDORSED]

Re: Balancing

Re: "Molar" form/ Pure number

Re: 14.9

Re: Conducting Metal

Re: Galvanic Cell

Re: Standard Reduction Potential

Re: entropy to surroundings

Re: Endergonic vs Endothermic

Re: 9.75

Re: 9.73

Re: Heat and temp difference

Re: Names of phase changes

Re: Internal Energy in a Vacuum [ENDORSED]

Re: PV=nRT

Re: Assigning system/surroundings

Re: Reversible vs Irreversible

Re: Liquids and Solids

Re: Expansion and change in pressure

Re: Most Stable Forms