Search found 23 matches

by Jessica Manzano 1B
Sat Mar 12, 2016 6:13 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium Help [ENDORSED]
Replies: 5
Views: 1438

Re: Pre-Equilibrium Help [ENDORSED]

My quiz has a slightly different version but it's the same idea: CHBr 3 (g) + Br 2 (g) -> CBr 4 (g) + HBr(g) Use the pre-equilibrium approach to justify if the following mechanism is consistent with the observed rate law: Rate= k[Br 2 ][CHBr 3 ] Step 1 (fast): Br 2 (g) -> 2Br(g) Step 2 (slow): CHBr ...
by Jessica Manzano 1B
Wed Mar 09, 2016 4:21 pm
Forum: *Complex Reaction Coordinate Diagrams
Topic: Quiz 3 Question 4C
Replies: 1
Views: 575

Re: Quiz 3 Question 4C

My quiz is a different version, but I'm referencing my quiz question that looks the most relevant to your question. The reaction coordinate diagram illustrates two peaks, indicating that the reaction has two steps. The forward reaction occurs faster because the first step in the forward reaction req...
by Jessica Manzano 1B
Mon Feb 29, 2016 1:27 pm
Forum: *Identifying Primary, Secondary, Tertiary, Quaternary Carbons, Hydrogens, Nitrogens
Topic: Secondary Carbons
Replies: 1
Views: 302

Re: Secondary Carbons

A secondary carbon is a carbon atom bonded to 2 other carbon atoms. The carbon atom bonded to CH 3 and CH 3 CHCH 3 is not a secondary carbon because if you look to the left and right of that carbon atom, it is attached to 2 other carbon atoms in the parent chain. That carbon atom is a quaternary car...
by Jessica Manzano 1B
Tue Feb 23, 2016 5:30 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Temperature and rxn rate
Replies: 1
Views: 281

Re: Temperature and rxn rate

Lowering the temperature slows down the reaction because when you lower temperature, you lower kinetic energy. Kinetic energy increases the chances that reactants will collide, and reactants must collide in order to react. Therefore, if you lower this kinetic energy, reactants will be less likely to...
by Jessica Manzano 1B
Wed Feb 17, 2016 8:44 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Example 15.7
Replies: 1
Views: 287

Re: Example 15.7

I believe you do always use the reactants to write a rate law because only the concentrations of the reactants affect the rate of reaction. The concentrations of the products result from the rate of reaction, but the rate does not depend on those concentrations. Typically, only fast steps would requ...
by Jessica Manzano 1B
Wed Feb 10, 2016 10:06 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: help with midterm 2012 q 7A
Replies: 1
Views: 256

Re: help with midterm 2012 q 7A

0.34 V is the standard reduction potential for the Cu/Cu2+ half reaction. I believe this value would likely be given to us in a table.
by Jessica Manzano 1B
Wed Feb 10, 2016 10:02 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Is E a state function?
Replies: 1
Views: 401

Re: Is E a state function?

E is not a state function because it depends on the path taken (i.e. what was reduced and what was oxidized). It is an intensive property because its value does not change depending on the amount of substance involved.
by Jessica Manzano 1B
Wed Feb 03, 2016 2:51 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams- Overview
Replies: 1
Views: 276

Re: Cell Diagrams- Overview

A galvanic cell consists of the following parts: -Anode -Voltmeter -Salt bridge -Cathode In the anode, there is a Zn electrode immersed in a ZnSO 4 solution. The Zn is oxidizing, or losing electrons. When Zn loses electrons, it releases Zn 2+ ions into the solution in the anode. The release of Zn 2+...
by Jessica Manzano 1B
Wed Jan 27, 2016 2:20 pm
Forum: Balancing Redox Reactions
Topic: Balancing Charges
Replies: 2
Views: 367

Re: Balancing Charges

In a redox reaction, electrons are transferred; the oxidized reactant loses electrons and the reduced reactant gains electrons. Although the electrons are transferred from one reactant to another in the reaction, the number of electrons is conserved. In the example we did in class, we separated a re...
by Jessica Manzano 1B
Thu Jan 21, 2016 5:31 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: what is Kb
Replies: 1
Views: 281

Re: what is Kb

kB in S=kblnW is Boltzmann's constant, 1.38 x 10-23 J/K.
by Jessica Manzano 1B
Thu Jan 14, 2016 4:25 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculating Bond Enthalpies
Replies: 1
Views: 267

Re: Calculating Bond Enthalpies

Ways to calculate \Delta H : Using Hess's Law: - Because enthalpy is a state function, you can add the enthalpy changes at each step of a reaction to find the total enthalpy change - To add the steps of a reaction together and find the total enthalpy of that reaction, you can manipulate the chemical...
by Jessica Manzano 1B
Tue Jan 05, 2016 9:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 2
Views: 502

Re: Hess's Law

When using Hess's Law, you're basically manipulating two or more given chemical equations and their delta H values so that when they are added together, they give you the chemical equation and delta H of the reaction you are finding delta H for. The given equations are steps into which the equation ...
by Jessica Manzano 1B
Tue Dec 01, 2015 2:30 pm
Forum: Polyprotic Acids & Bases
Topic: HW 12.77 (Calculating pH of alanine)
Replies: 3
Views: 580

Re: HW 12.77 (Calculating pH of alanine)

This equation was discussed by my TA in discussion section and this is how I understood it: On the titration curve of a polyprotic acid (an acid that can donate more than one H+ proton and has different K a values for each proton lost), there are midpoints on the curve where pH=pK a . These midpoint...
by Jessica Manzano 1B
Wed Nov 25, 2015 1:47 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Adding [A-] Effect on pH
Replies: 1
Views: 371

Re: Adding [A-] Effect on pH

I think the answer should be "c. remain constant because the resulting solution is a buffer." I do not think the pH of the solution of oxalic acid will increase or decrease due to the added oxalate. This is how I understand it: the pH remains constant because when you add sodium oxalate (t...
by Jessica Manzano 1B
Wed Nov 25, 2015 1:24 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Box
Replies: 1
Views: 304

Re: ICE Box

You may neglect the x value in ICE box calculations when the given K value is very small (an example problem in our course reader uses the value K c = 2.0 x 10 -37 ). From a very small K value, one can infer that the change in molar concentration, x, in the reaction is also very small--- so small th...
by Jessica Manzano 1B
Thu Nov 19, 2015 1:20 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: CO3 2- (carbonato)
Replies: 2
Views: 1634

Re: CO3 2- (carbonato)

You can determine why carbonato can be either monodentate or bidentate by looking at its Lewis structure. In its Lewis structure, the C atom in the middle forms one double bond with an O atom and forms two single bonds with the remaining two O atoms. The two single C-O bonds include O atoms that hav...
by Jessica Manzano 1B
Thu Nov 12, 2015 12:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: reactants of equilibrium constants
Replies: 1
Views: 262

Re: reactants of equilibrium constants

In equilibrium constants, pure substances like solids and liquids are not included because their concentrations do not change in a reaction. To understand this, think about Dr. Lavelle's analogy of taking three dollars away from one million dollars; relative to the concentration of solvent that soli...
by Jessica Manzano 1B
Thu Nov 05, 2015 2:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Bond Angle for Various Molecular Shapes
Replies: 2
Views: 1534

Re: Determining Bond Angle for Various Molecular Shapes

A molecular shape will have an angle of less than its expected angle (for example, 109.5 o for a tetrahedral or 120 o for trigonal planar) if it has lone pairs causing repulsion on the other electron pairs in the molecule. Lone pair-lone pair repulsion is the strongest form of electron repulsion, fo...
by Jessica Manzano 1B
Thu Oct 29, 2015 11:54 pm
Forum: Bond Lengths & Energies
Topic: Valence Bond Theory
Replies: 1
Views: 324

Re: Valence Bond Theory

B can function as an exception to the octet rule. When you look at the chemical formula of BH 3 and plan its Lewis structure, the number of valence electrons in the molecule add up to 6 (3 valence electrons for B and 1 valence electron for each H). B is an exception to the octet rule because with a ...
by Jessica Manzano 1B
Thu Oct 22, 2015 6:27 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Question Regarding Ionic Character
Replies: 1
Views: 518

Re: Question Regarding Ionic Character

Electronegativity is the measure of an atom's ability to attract electrons. CaO has greater ionic character than MgO because the electronegativity difference between Ca and O (1.0 and 3.5) is greater than the electronegativity difference between Mg and O (1.2 and 3.5). This electronegativity differe...
by Jessica Manzano 1B
Wed Oct 14, 2015 10:30 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for Copper
Replies: 2
Views: 10378

Re: Electron Configuration for Copper

The ground state electron configuration of Cu is [Ar] 3d 10 4s 1 . Although 4s is filled before 3d, 3d becomes lower in energy than 4s once it is filled with electrons, which is why 4s 1 is listed after 3d 10 . One may expect the electron configuration of Cu to be [Ar] 3d 9 4s 2 , but this is not tr...
by Jessica Manzano 1B
Thu Oct 08, 2015 9:42 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Nodal Planes
Replies: 1
Views: 254

Re: Nodal Planes

Nodal planes are regions in which there is zero probability of finding an electron in an atom. S-orbitals do not have nodal planes, but p, d, and f orbitals have nodal planes because they have angular momentum that affects interaction between electrons and the nucleus. This angular momentum gives th...
by Jessica Manzano 1B
Thu Oct 01, 2015 9:16 pm
Forum: Properties of Light
Topic: Clarification on Wave-Particle Duality of ER
Replies: 2
Views: 419

Clarification on Wave-Particle Duality of ER

This post refers to Figure 1.19 in the textbook, the figure of incident light coming through slits and creating a diffraction pattern that is also depicted in the course reader. The explanation of Figure 1.19 in the textbook says that at the points where the waves experience constructive interferenc...

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