Search found 59 matches

by Nahelly Alfaro-2C
Fri Mar 15, 2019 11:47 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Microscopic Reversibilty
Replies: 1
Views: 29

Microscopic Reversibilty

I'm still confused about what microscopic reversibility is and when this type reversibility is applied?
by Nahelly Alfaro-2C
Fri Mar 15, 2019 11:43 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: applying Le Chatelier's Principle
Replies: 4
Views: 162

applying Le Chatelier's Principle

On the first midterm, for the first question part how do you know/ prove that the shift in the reaction is forward?
by Nahelly Alfaro-2C
Sun Mar 10, 2019 12:18 am
Forum: General Science Questions
Topic: Discussion Section Test
Replies: 3
Views: 165

Re: Discussion Section Test

The reason why delta G>0 would be wrong is that during photosynthesis a plant uses light energy from the sun and carbon dioxide plus water to convert it into glucose and oxygen. This means that glucose is a product of the chemical reaction that is occurring, therefore, being exergonic.
by Nahelly Alfaro-2C
Sun Mar 10, 2019 12:05 am
Forum: General Rate Laws
Topic: reaction process
Replies: 1
Views: 30

reaction process

How can you tell difference between a reaction being slow or fast?
by Nahelly Alfaro-2C
Wed Mar 06, 2019 11:20 am
Forum: Van't Hoff Equation
Topic: Temp Units
Replies: 11
Views: 222

Re: Temp Units

I believe you would K units for temperature.
by Nahelly Alfaro-2C
Sun Mar 03, 2019 7:36 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: n and k
Replies: 3
Views: 58

Re: n and k

N is needed because it gives insight into the reaction mechanism of the reactant. K is needed because the rate constant that depends on the temperature and activation energy.
by Nahelly Alfaro-2C
Sun Mar 03, 2019 7:30 pm
Forum: Student Social/Study Group
Topic: Week 8
Replies: 2
Views: 170

Re: Week 8

Monday- Nernst equation ( using log, the presence of H+ or pH), Concentration cell using Nernst equation Wednesday- applications of electron transfer reactions( ion-selective electrodes), electrolysis, Kinetics, Kinetic analysis, reaction rate, average rate, instantaneous rate Friday- unique rate, i...
by Nahelly Alfaro-2C
Sun Mar 03, 2019 7:21 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Cell diagram
Replies: 4
Views: 88

Re: Cell diagram

Cell diagrams are used to write the redox reaction of the physical set up of the cell. It consists of a salt bridge represents by two lines (II) and one line (I) to represent the interface between phases in contact with each other. The anodes are on the left of the salt bridge while the cathode is o...
by Nahelly Alfaro-2C
Sun Feb 24, 2019 8:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: equilibruim based on enthalpy
Replies: 3
Views: 66

equilibruim based on enthalpy

How can you determine the shift in the equilibrium of a chemical reaction when only given the change of enthalpy of the reaction?
by Nahelly Alfaro-2C
Sun Feb 24, 2019 8:06 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free Energy is a state function?
Replies: 5
Views: 72

Re: Free Energy is a state function?

To add on, state functions are able to be added and subtracted which is how Gibbs energy is obtained between enthalpy, entropy and temperature values. State functions are also independent on the path taken to obtain that state.
by Nahelly Alfaro-2C
Sun Feb 24, 2019 7:54 pm
Forum: Balancing Redox Reactions
Topic: Oxidation and Reduction?
Replies: 6
Views: 70

Re: Oxidation and Reduction?

Oxidation means the loss of electron. Reduction is the gain of an electron.
by Nahelly Alfaro-2C
Sun Feb 17, 2019 5:21 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Enthalpy
Replies: 4
Views: 151

Enthalpy

Why does the magnitude in the change in entropy depend on temperature when heat is transferred?
by Nahelly Alfaro-2C
Sun Feb 17, 2019 5:16 pm
Forum: Calculating Work of Expansion
Topic: work
Replies: 2
Views: 61

work

Just a verification for work equations:
We would use W=-Pdelta V when pressure is constant and W=-nRTln(V2/V1) when pressure is not constant?
by Nahelly Alfaro-2C
Sun Feb 17, 2019 4:51 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Temperature
Replies: 2
Views: 40

Temperature

Based on the temperature a reaction has, how can one know if reaction being favored is forward or reverse?
by Nahelly Alfaro-2C
Sun Feb 10, 2019 10:42 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
Replies: 3
Views: 138

Re: Degeneracy

Degeneracy (w) is the number of ways of achieving a given energy state. The relationship shared between entropy and degeneracy is the Boltzmann's equation- S= kB ln W. The way degeneracy would be calculated is W=2^N in which N represents the particles that can be found in one of two states. When con...
by Nahelly Alfaro-2C
Sun Feb 10, 2019 10:33 pm
Forum: Calculating Work of Expansion
Topic: Work Formula Involving Integral
Replies: 3
Views: 45

Re: Work Formula Involving Integral

In a way it could be considered to be a form of obtaining w=-P times delta V; however, this equation is used to during an irreversible pathway which is temperature (T) changes along a pathway decrease then increase work done against constant Pex. The integral form of obtaining work done in a system ...
by Nahelly Alfaro-2C
Sun Feb 10, 2019 10:13 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat as path function
Replies: 3
Views: 69

Re: Heat as path function

State property is not dependent on a path is taken to obtain that state. This means that the state property can either be added or subtracted. In this case, heat cannot be considered a state function because heat and work depend on a path to reach work and heat.
by Nahelly Alfaro-2C
Sun Feb 03, 2019 11:17 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Hess's Law depends on enthalpy as a state function
Replies: 3
Views: 65

Re: Hess's Law depends on enthalpy as a state function

Remember that state properties do not depend on a path taken to obtain that state and they can also be added or subtracted. Therefore changes in enthalpy (Hess's Law) are additive like a state function. In addition, enthalpy change at each step of a multi-step reaction can be additive to give the to...
by Nahelly Alfaro-2C
Sun Feb 03, 2019 11:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: intensive vs extensive properties
Replies: 2
Views: 59

intensive vs extensive properties

What are the differences between intensive and extensive properties?
by Nahelly Alfaro-2C
Sun Feb 03, 2019 11:02 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: RXN constant P
Replies: 2
Views: 53

RXN constant P

When is the rxn constant P significant and insignificant? Why is knowing its significance important?
by Nahelly Alfaro-2C
Sun Jan 27, 2019 9:20 pm
Forum: Phase Changes & Related Calculations
Topic: State Properites
Replies: 7
Views: 101

State Properites

Why are work and heat not considered a state property?
by Nahelly Alfaro-2C
Sun Jan 27, 2019 9:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard reaction enthalpy
Replies: 2
Views: 48

Standard reaction enthalpy

How can the standard reaction enthalpy be calculated if the bond enthalpies are not provided in the problem?
by Nahelly Alfaro-2C
Sun Jan 27, 2019 9:06 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: closed vs isolated
Replies: 14
Views: 190

Re: closed vs isolated

A closed system only allows for the exchange of energy in the system. On the other hand, an isolated system does not allow the exchange of energy or matter in the system.
by Nahelly Alfaro-2C
Sun Jan 20, 2019 10:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: The pH of Solutions of Weak Acids and Bases 12.73
Replies: 1
Views: 47

Re: The pH of Solutions of Weak Acids and Bases 12.73

The pH of the solution can be found by first finding the equilibrium the conjugate acid of the weak base and finding its Ka and Kb. From there an ICE table can be created in order to find the concentrations based on the concentrations that were provided by the problem. You could then find the Ka by ...
by Nahelly Alfaro-2C
Sun Jan 20, 2019 10:37 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: 6th Edition 12.39
Replies: 1
Views: 121

Re: 6th Edition 12.39

The same values of the molecules can be used because in order to find the Ka you would be able to use the equation Ka +Kb= 1x10^-14 since the Kb value has been provided. This would also be applied if the Ka were to be provided in order to find the Kb.
by Nahelly Alfaro-2C
Sun Jan 20, 2019 10:10 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5% rule
Replies: 11
Views: 150

5% rule

How does the 5% rule work? How do we know it should be used when calculating an equilibrium?
by Nahelly Alfaro-2C
Sun Jan 13, 2019 7:28 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction Quotient Meaning
Replies: 2
Views: 49

Re: Reaction Quotient Meaning

The reaction Q comes into play when the direction in which the reaction will proceed (left or right) and is used when comparing it to the equilibrium constant, K. If Q<k, the reactant proceeds forward to the product side. If Q>k, then it is a reverse reaction and favors the reactant side of the equa...
by Nahelly Alfaro-2C
Sun Jan 13, 2019 7:20 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th edition 5I.3
Replies: 2
Views: 34

Re: 7th edition 5I.3

I believe that the reactants for this problem would be H2 and I2 and the product would be HI. In addition, you can assume H2 is a reactant that is what the problem is asking to find the concentration for and the concentration for I2 has been provided.
by Nahelly Alfaro-2C
Sun Jan 13, 2019 7:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Tables
Replies: 3
Views: 41

ICE Tables

When adding the x variable to the changing concentration is the reactant side always going to add a negative x (-x) and the products side added a positive x (+x)? Are there special cases when this is not the case?
by Nahelly Alfaro-2C
Mon Jun 04, 2018 9:29 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charge
Replies: 5
Views: 216

Re: Formal charge

Bonds are always counted as one electron, never as two electrons. If a single bond is present there is one election. In the presence of a double bond, there are two electrons If a triple bond is present there are three electrons.
by Nahelly Alfaro-2C
Mon Jun 04, 2018 9:24 pm
Forum: Ideal Gases
Topic: Memorization
Replies: 12
Views: 325

Re: Memorization

I believe you do not have to because it is provided in the constant and equation page during a test but it wouldn't hurt to know it.
by Nahelly Alfaro-2C
Fri Jun 01, 2018 12:13 am
Forum: Determining Molecular Shape (VSEPR)
Topic: regions of e- density
Replies: 4
Views: 121

Re: regions of e- density

I believe the different regions of electron density do correspond to different molecular shapes because it was said in class that different hybridizations describe shapes. I this would connect to your question because the regions of electron density= number of hybrid orbitals. Hope it helped.
by Nahelly Alfaro-2C
Fri Jun 01, 2018 12:03 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar and non polar
Replies: 3
Views: 71

Polar and non polar

I understand that a polar molecule must have polar bonds with dipoles that do not cancel. I also understand that a nonpolar molecule must have zero an electric dipole moment which is possible if it contains non-polar bonds. My question is how can you identify the difference and determine whether a m...
by Nahelly Alfaro-2C
Thu May 31, 2018 11:46 pm
Forum: Hybridization
Topic: hybridization
Replies: 2
Views: 114

hybridization

Can someone explain how hybridization works? How can a hybridized molecule be determined and the orbitals assigned to it as well? For example, NH3( ammonia).
by Nahelly Alfaro-2C
Wed May 23, 2018 1:15 am
Forum: Lewis Structures
Topic: H Formal Charge
Replies: 4
Views: 138

Re: H Formal Charge

Hydrogen does not have a formal charge because it is a stable atom. It only has one electron in its shell. When taking the formal charge it would be:
V-(L+1/2B)
1-(0+1/2*2)=1-1=0
The zero indicates a neutral charge.
by Nahelly Alfaro-2C
Mon May 21, 2018 11:20 pm
Forum: Lewis Structures
Topic: 3.41 part c
Replies: 4
Views: 128

Re: 3.41 part c

You would start the structure with NH2 followed by H2C and COOH. The central atoms in the Lewis structure would be Nitrogen, Carbon, and Oxygen.
by Nahelly Alfaro-2C
Mon May 21, 2018 11:12 pm
Forum: Bond Lengths & Energies
Topic: Bond Order
Replies: 4
Views: 226

Re: Bond Order

In class, it was mentioned the strength of a bond is measured by its dissociation energy which is the energy required to break the bonds. It ranges between a single, double or triple bond. The single bond is the longest and weakest while the triple bond is the shortest and strongest. For example, N2...
by Nahelly Alfaro-2C
Thu May 17, 2018 11:26 pm
Forum: Lewis Structures
Topic: Identifying radicals [ENDORSED]
Replies: 4
Views: 146

Identifying radicals [ENDORSED]

I know that radical is an atom, molecule, or ion that has unpaired electron but I still have difficulty identifying the radical. Can someone explain how to identify a radical? For example, problem 3.55 part (B)-CH3
by Nahelly Alfaro-2C
Thu May 17, 2018 11:13 pm
Forum: Ionic & Covalent Bonds
Topic: Help on 3.21
Replies: 2
Views: 60

Re: Help on 3.21

For part C the ground state configuration for Te2- is [Xe] with no unpair electron. For part D the ground state configuration for Ag+ is [Kr]4d10 with no unpaired electrons are well.
by Nahelly Alfaro-2C
Thu May 17, 2018 11:07 pm
Forum: Electronegativity
Topic: Connection
Replies: 3
Views: 192

Re: Connection

Electronegativity and polarity are connected through the bonds made between atoms. The greater difference in electronegativity between the atoms the more polar the bond is going to be.
by Nahelly Alfaro-2C
Thu May 17, 2018 10:57 pm
Forum: Lewis Structures
Topic: Test #3
Replies: 11
Views: 341

Re: Test #3

I think it will cover everything we have learned after to test #2 up to what we are currently learning. So I would assume it is all of chapter 3.
by Nahelly Alfaro-2C
Mon May 07, 2018 11:18 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Module Question #17
Replies: 4
Views: 177

Re: Module Question #17

You are starting the problem correctly by multiplying the speed of light to the mass of an electron to 1/100; however, your uncertainty in momentum is not 3x10^6. The uncertainty in momentum is actually 2.731 x 10^-24 which is the mistake is made. From there like you mentioned, you would divide the ...
by Nahelly Alfaro-2C
Mon May 07, 2018 10:44 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: homework week 6
Replies: 3
Views: 159

Re: homework week 6

I would assume from chapter 3 because that is what we learned started last Wednesday and what we learned today is from that chapter but I think we could also include chapter 2 because it helps review for the midterm.
by Nahelly Alfaro-2C
Mon May 07, 2018 12:06 am
Forum: Quantum Numbers and The H-Atom
Topic: Homework problem 2.93
Replies: 2
Views: 169

Re: Homework problem 2.93

You are correct in the concept that cations are smaller than there parent element and anions are bigger than their parent element. You may have read the solution incorrectly as the correct answer mentioned in the textbook is A= Cl, B= Na, C= Cl- and D=Na+.
by Nahelly Alfaro-2C
Thu May 03, 2018 11:13 pm
Forum: Ionic & Covalent Bonds
Topic: Help on 2.43
Replies: 3
Views: 118

Re: Help on 2.43

The ground-state configuration of the elements is the last noble gas of the row above it with the electron configuration. So the elements configuration for a,b, and d would be
silver- [Kr]4d^10 5s
beryllium-[He]2s^2
gallium-[Ar]3d^10 4s^2 4p
by Nahelly Alfaro-2C
Tue May 01, 2018 5:15 pm
Forum: Balancing Chemical Reactions
Topic: Why didn't we take into account charges
Replies: 4
Views: 191

Re: Why didn't we take into account charges

We don't take into consideration the electron charge of the elements because when they put with another element they balance each other. For example, water uses hydrogen and oxygen. hydrogen has a +1 charge while oxygen has a -2 charge with is why it water requires two hydrogens to satisfy oxygens o...
by Nahelly Alfaro-2C
Sun Apr 29, 2018 5:21 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s orbital lower in energy than 3d
Replies: 3
Views: 293

Re: 4s orbital lower in energy than 3d

The 3d state is higher in energy than the 4s state for potassium and calcium because Z(atomic number) is equal to 20. In addition, the d-electron are higher in energy than the p-electron on the same shell which results in higher energy than s-electron of the same shell too.
by Nahelly Alfaro-2C
Sun Apr 29, 2018 5:05 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW 2.31 [ENDORSED]
Replies: 5
Views: 192

Re: HW 2.31 [ENDORSED]

the subshells 2d and 4g do not exist because there is not an element to be assigned to in that subshell. The d-block of subshells is for transition metals and begin at 3d. The 4g could simply not be possible because the subshells on the periodic table go up to the f-block. The 4d and 6f subshells ca...
by Nahelly Alfaro-2C
Tue Apr 24, 2018 3:59 pm
Forum: Einstein Equation
Topic: converting from keV to joules
Replies: 7
Views: 272

Re: converting from keV to joules

I think we don't because it was one of the conversions located in the front of test one.
by Nahelly Alfaro-2C
Tue Apr 24, 2018 3:34 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework Question 1.11
Replies: 1
Views: 63

Re: Homework Question 1.11

The textbook mentions that the series consists of the lines of the spectrum that show its lowest energy level. For the Balmer series its lowest energy level is n=2 as the Lyman series the lowest energy level would be n=1. For the Paschen series the lowest energy level would be n=3 and for the Bracke...
by Nahelly Alfaro-2C
Sun Apr 22, 2018 10:19 pm
Forum: Balancing Chemical Reactions
Topic: Q4
Replies: 3
Views: 181

Re: Q4

when you are writing a combustion equation you will always add O2 to the reactant part of the equation because the product will be CO2 and H2O.
So in writing the combustion equation of fluorene, it would be: C13H10+O2----> CO2+H2O. You then have to balance the equation to make it side equal.
by Nahelly Alfaro-2C
Fri Apr 20, 2018 12:46 am
Forum: General Science Questions
Topic: Test #2 [ENDORSED]
Replies: 6
Views: 414

Re: Test #2 [ENDORSED]

The problems are from chapter one: 3,5,7,9,11,13,15,21,23,25,27,33,37,39,41.
by Nahelly Alfaro-2C
Sat Apr 14, 2018 9:30 pm
Forum: Properties of Light
Topic: wavelength description [ENDORSED]
Replies: 11
Views: 321

Re: wavelength description [ENDORSED]

From what I understood during the lecture the amplitude of a wavelength represents its height.
by Nahelly Alfaro-2C
Thu Apr 12, 2018 1:42 am
Forum: Limiting Reactant Calculations
Topic: M1 hw
Replies: 3
Views: 169

Re: M1 hw

The molar mass 31.038 of 2NH3 would not be used because the 2 in 2NH3 serves as stoichiometric coefficient being used to balanced the equation as a whole. The molar mass 17.031 would be the one being used because it is the molar mass if ammonia (NH3) and would be used to find the moles of NH3 to the...
by Nahelly Alfaro-2C
Mon Apr 09, 2018 12:38 pm
Forum: Significant Figures
Topic: Sig fig simple question [ENDORSED]
Replies: 5
Views: 222

Re: Sig fig simple question [ENDORSED]

yes this is correct
by Nahelly Alfaro-2C
Sat Apr 07, 2018 9:38 pm
Forum: Empirical & Molecular Formulas
Topic: Finding the molecular formula [ENDORSED]
Replies: 5
Views: 187

Finding the molecular formula [ENDORSED]

After finding the empirical formula of a molecule, would you use the molar mass of the empirical formula to find the molecular formula of a molecule?
by Nahelly Alfaro-2C
Sat Apr 07, 2018 8:22 pm
Forum: SI Units, Unit Conversions
Topic: writing out conversions in one long line vs. steps
Replies: 16
Views: 562

Re: writing out conversions in one long line vs. steps

I find more convenient to write the conversion in one long line because it is easier for me to see the conversion between the units. It's also easier for me to see the units that needed to be canceled.
by Nahelly Alfaro-2C
Sat Apr 07, 2018 8:02 pm
Forum: SI Units, Unit Conversions
Topic: Units + their meanings
Replies: 3
Views: 139

Re: Units + their meanings

The unit for moles is "mol". In addition, the unit g/mol signifies mass per mole of a particle which is what defines molar mass.

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