Search found 29 matches

by Oscar Valdovinos 1I
Sat Mar 17, 2018 1:42 pm
Forum: *Alkanes
Topic: Final
Replies: 13
Views: 1180

Re: Final

I think the questions are going to ask us to identify functional groups within huge carbon chains.
by Oscar Valdovinos 1I
Sat Mar 17, 2018 1:39 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneity question
Replies: 7
Views: 358

Re: Spontaneity question

Assuming delta H is postive,
The temperature is high enough it could overcome a positive delta H and make delta G negative (thus a spontaneous reaction). But if temperature is low it doesn't matter if you have a positive delta S, the reaction is not spontaneous.
by Oscar Valdovinos 1I
Sat Mar 17, 2018 1:32 pm
Forum: *Enzyme Kinetics
Topic: Catalysts in a reaction
Replies: 7
Views: 576

Re: Catalysts in a reaction

If the substance shows up in the products and isnt cancelled out later by a reactant, then it can not be an intermediate.
by Oscar Valdovinos 1I
Sat Mar 17, 2018 1:26 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Step Determining Overall Rate
Replies: 3
Views: 147

Re: Slow Step Determining Overall Rate

the slow step itself makes up the rate law because it is rate determining step. In other words you could only go as fast as your slowest step. If the first step is your slow step then that is the rate law. But if the slow step is your second or third step in the reaction you have to include the rate...
by Oscar Valdovinos 1I
Wed Mar 14, 2018 10:46 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Question 15.47
Replies: 4
Views: 158

Re: Question 15.47

Another perspective to take on intermediates, is that are not present in the reactants of the first step and the products of the last step. Therefore Intermediates are produced by an elementary reaction but consumed in another one.
by Oscar Valdovinos 1I
Wed Mar 14, 2018 10:21 pm
Forum: First Order Reactions
Topic: Psuedo-Order Rate Laws
Replies: 1
Views: 182

Re: Psuedo-Order Rate Laws

It was covered in class, so there its likely.
by Oscar Valdovinos 1I
Wed Mar 14, 2018 10:19 pm
Forum: General Rate Laws
Topic: Rate Law
Replies: 6
Views: 478

Re: Rate Law

When writing out the rate law equation, the exponents are the orders of the reaction. Therefore, the coefficient doesn't have an effect on the value of the of the exponents.
by Oscar Valdovinos 1I
Sat Mar 10, 2018 5:51 pm
Forum: Balancing Redox Reactions
Topic: 14.5 Part a
Replies: 4
Views: 202

14.5 Part a

If we are combining redox reductions and it has to be in basic solution, does the final answer have to include (OH-)?
I am asking this because the solutions manual for 14.5 part a does not have (OH-) in its final answer
by Oscar Valdovinos 1I
Sat Mar 10, 2018 5:08 pm
Forum: First Order Reactions
Topic: Log vs ln
Replies: 9
Views: 472

Re: Log vs ln

There is no need to convert ln into log, and this could cause an answer to be wrong if you ever need to get rid of ln. Since e^ln cancels out smoothly the finding the reaction constant or time is made easier. In short, stick with ln
by Oscar Valdovinos 1I
Sat Mar 10, 2018 4:54 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: The universe as a thermodynamic system [ENDORSED]
Replies: 3
Views: 267

Re: The universe as a thermodynamic system [ENDORSED]

Since the universe contains everything by definition, and thus there can be no exchange of energy or matter with anything, thus the Universe is an isolated system.
by Oscar Valdovinos 1I
Sat Mar 10, 2018 4:49 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: The First Law
Replies: 6
Views: 396

Re: The First Law

I think the conservation of energy is another name to the first law so they are the same.
by Oscar Valdovinos 1I
Sat Mar 03, 2018 7:11 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7582
Views: 1015220

Re: Post All Chemistry Jokes Here

I make bad chemistry puns, but only periodically.
by Oscar Valdovinos 1I
Sat Mar 03, 2018 7:10 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7582
Views: 1015220

Re: Post All Chemistry Jokes Here

Q: What was the charge when NaCl was arrested?

A:Salt.
by Oscar Valdovinos 1I
Sat Mar 03, 2018 7:08 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7582
Views: 1015220

Re: Post All Chemistry Jokes Here

The only chemistry jokes that haven't been poster yet are the BORON ones,
*Ba Dum tsss*
by Oscar Valdovinos 1I
Sat Feb 10, 2018 11:54 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13
Replies: 1
Views: 113

Re: 9.13

We use 5/2*R because the question says that the volume is changed from 3L to .5L so the reaction does not take place under constant volume. It does however take place under constant pressure.

Cp=5/2*R

Cv=3/2*R
by Oscar Valdovinos 1I
Sat Feb 10, 2018 11:49 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Concept of Second Law of Thermodynamics
Replies: 6
Views: 377

Re: Concept of Second Law of Thermodynamics

The 2nd law of thermodynamics relates entropy change to heat and temperature. For example if you connected two rooms that are at different temperatures, the temperature of the two rooms will reach an equilibrium
by Oscar Valdovinos 1I
Sat Feb 10, 2018 11:40 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7582
Views: 1015220

Re: Post All Chemistry Jokes Here

Aha
by Oscar Valdovinos 1I
Sat Feb 10, 2018 11:25 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Degeneracy (W)
Replies: 4
Views: 166

Re: Degeneracy (W)

To findthe degeneracy, you need to the formula W= number of states^(number of molecules)
by Oscar Valdovinos 1I
Sat Feb 10, 2018 11:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.99: Enthalpy Values
Replies: 2
Views: 151

Re: 8.99: Enthalpy Values

I think the solution manual has a mistake in when calculating the enthalpy of formation, because i notice that the enthalpy for HCL was used twice in their equation.
by Oscar Valdovinos 1I
Sat Feb 10, 2018 10:57 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Third law
Replies: 3
Views: 141

Re: Third law

Adding to the post above, another way to think about is that heat is created by the movement of particles. Thus as the temperature reaches closer to 0 kelvin, this absolutely no movement, thus we have exactly no entropy.
by Oscar Valdovinos 1I
Sat Jan 27, 2018 11:56 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question regarding 8.39 homework question
Replies: 5
Views: 217

Re: Question regarding 8.39 homework question

In short, this problem requires two steps, the first step is calculating how much heat is needed to melt the ice at 0c, basically asking you to calculate the phase change with 80grams of ice (DeltaH=n(6.01kj*mol). The second part is calculating a change in temperature with the 80g of liquid water wh...
by Oscar Valdovinos 1I
Sat Jan 27, 2018 11:45 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Examples of work being done
Replies: 7
Views: 305

Re: Examples of work being done

Another aspect of work to note is that work is not a state meaning that its value depends on the path taken. A quick example of this would be pushing a ball 100ft on a flat surface would require less work on the system than pushing that same ball uphill for a 100ft.
by Oscar Valdovinos 1I
Sat Jan 27, 2018 11:29 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: CV or CP
Replies: 5
Views: 201

Re: CV or CP

You use Cv when the reaction is going under a constant Volume (isometric) and Cp when the pressure is not changing in the reaction (isobaric).
by Oscar Valdovinos 1I
Sun Jan 21, 2018 11:13 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.49
Replies: 5
Views: 203

Re: 8.49

I think you assume ideal gases, which is why we use Pv=nRT. Also in ideal gases tempature is always 25 degrees celsius or 298 kelvin
by Oscar Valdovinos 1I
Sun Jan 21, 2018 11:09 pm
Forum: Phase Changes & Related Calculations
Topic: heat vs ΔH vs work
Replies: 2
Views: 117

Re: heat vs ΔH vs work

Adding on the previous reply, work can only occur in a change in volume in the system, that is why in a bomb calorimeter work is always zero. A few examples that would cause a work change is a piston changing the volume of the system or pushing a box around a room. Another aspect of work is that it ...
by Oscar Valdovinos 1I
Sun Jan 21, 2018 10:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.67 gas to liquid
Replies: 2
Views: 105

Re: 8.67 gas to liquid

Changing a gas to liquid is an exothermic reaction and therefore the enthalpy is negative. In other words, the system which is the gas itself is losing energy to the surrounding this cooling can be seen in the physical change to a liquid.
by Oscar Valdovinos 1I
Sat Jan 13, 2018 8:37 pm
Forum: Phase Changes & Related Calculations
Topic: Constant temp
Replies: 3
Views: 157

Re: Constant temp

The heat is simply being use to get the substance through its phase change. After the phase change is completed then any addition of heat will result in higher temperature, until of course another phase change is begun and completed.
by Oscar Valdovinos 1I
Sat Jan 13, 2018 8:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Infinite Forms of Hess's Law
Replies: 5
Views: 136

Re: Infinite Forms of Hess's Law

Technically we could use Hess law to connect hundreds of equations, but I don't think we are going to see that in our problems because it would pointless since 2-4 equations shows that we know the concepts associated with Hess's law.
by Oscar Valdovinos 1I
Sat Jan 13, 2018 8:12 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeters
Replies: 3
Views: 110

Re: Calorimeters

We use bomb a calorimeter to measure the change in Enthalpy at a constant volume (gas or solution). A coffee cup Calorimeter is used to measure the change in heat at a constant pressure (solution only).

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