Search found 24 matches

by stelang
Thu Mar 10, 2016 10:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units
Replies: 2
Views: 332

Re: Units

Sometimes if you look at past practice exams both answers can be acceptable. If the answer in J looks super long you can always convert to kj to provide a more concise answer
by stelang
Fri Mar 04, 2016 11:22 pm
Forum: *Nucleophiles
Topic: Ambident Nucleophiles
Replies: 2
Views: 603

Re: Ambident Nucleophiles

Another property that most ambient nucleophiles have is that more than one atoms has a lone pair. This is what allows the molecule to have multiple Lewis structures in which different atoms carry the negative charge.
by stelang
Fri Feb 26, 2016 11:07 pm
Forum: *Nucleophiles
Topic: Br2 as an electrophile
Replies: 2
Views: 1889

Re: Br2 as an electrophile

You could also think of it has as the elections in the Br-Br bond are moving in a continuous pattern. At some point in time one Br molecule might have more electrons than the other Br. It just doesn't apply to this Br2 molecule. Even for a O2 molecule the electrons are moving in a continuous pattern...
by stelang
Fri Feb 19, 2016 11:16 pm
Forum: General Rate Laws
Topic: Differential Rate Law
Replies: 1
Views: 329

Re: Differential Rate Law

Well one way in which the differential rate law could be used is if for instant you want to calculate the rate constant and you are only given info about the concentration, order of the reaction and initial rate. You could then use initial rate=k[A]^x to solve for k.
by stelang
Fri Feb 12, 2016 1:06 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat capacity
Replies: 1
Views: 367

Re: Heat capacity

Ethane ends up having the greater heat capacity because it has more degrees of freedom. We can figure out the degrees of freedom via the equipartition theorem. I have posted a link explaining this concept. http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/eqpar.html"onclick="window.open(this.href);...
by stelang
Mon Feb 01, 2016 6:28 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: Residual Entropy
Replies: 1
Views: 431

Residual Entropy

Why is the residual entropy for one molecule of O2=0. Why is W=1 in this case. Can't each oxygen atom occupy two different states?
by stelang
Fri Jan 29, 2016 11:59 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Residual Molar Entropy
Replies: 3
Views: 534

Re: Residual Molar Entropy

One example of this type of problem was on one practice quiz asking for the residual molar entropy of one mole of c6h5br. We are able to use the klnW equation here after calculating the value of w. There are six possible states for carbon so W would simply be 6^avogadros number.
by stelang
Sat Jan 23, 2016 12:16 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: When to use C(delta)T vs. mC(delta)T
Replies: 1
Views: 910

Re: When to use C(delta)T vs. mC(delta)T

Usually the C Deta T is used, at least in the hw, in problems involving bomb calorimeters. Meanwhile the equation with the mass in front is utilized in almost every other scenario. You would use the equation with moles in a similar fashion. It all depends on what data is provided to you. In problem ...
by stelang
Fri Jan 15, 2016 9:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: kJ vs kJ/mol
Replies: 2
Views: 822

Re: kJ vs kJ/mol

Dr. Lavelle told us in class that he does not care if we represent our answers as either kj or kj/mol. However, in technicality enthalpy is always written in terms of kj/mol. The textbook sometimes writes delta H in just Kj when describing a reaction that takes place but truly what it means is kj pe...
by stelang
Fri Jan 08, 2016 10:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpy of Formation
Replies: 3
Views: 692

Re: Standard Enthalpy of Formation

You can also look at problem 8.59 for further clarification on this concept because n2 has the same property as O2 in this regard. In problem 8.59 you will notice that while doing this problem that no value for the enthalpy is given because the true value is 0.
by stelang
Sat Dec 05, 2015 10:27 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Shape
Replies: 2
Views: 419

Re: Shape

Some basic ones can be memorized such as EDTA which forms 6 bonds, oxalato which is bidentate, dien which is tridentate or en which is bidentate. I find it easier to memorize these main ones and understand the rest through drawings.
by stelang
Thu Nov 26, 2015 5:07 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Trend to Remembering Strong Acids
Replies: 2
Views: 610

Re: Trend to Remembering Strong Acids

There is no real trend but there are only 6 primary strong acids that you really need to remember: HCL, HBr, HI, HCLO4, H2SO4, and HNO3. One trend you could think of is remember that four of the strong acids listed previously contain a halogen and three simply contain a hydrogen and a halogen. Other...
by stelang
Thu Nov 19, 2015 5:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressures and Equilibrium
Replies: 2
Views: 464

Re: Partial Pressures and Equilibrium

You actually can not just plug directly into the equation. You actually do have to set up an ice box later on in the problem. However first calculate the value of Kp for the given initial values as you will obtain your equilibrium constant. Next use the ice box method with the initial values being 4...
by stelang
Thu Nov 19, 2015 5:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Significant Figures with Chemical Equilibria?
Replies: 1
Views: 325

Re: Significant Figures with Chemical Equilibria?

Sometimes in the textbook significant figures are rounded on a step by step basis. However on all tests and quizzes only round at the very end.
by stelang
Thu Nov 12, 2015 11:20 pm
Forum: Naming
Topic: HW 17.31 part d
Replies: 2
Views: 429

Re: HW 17.31 part d

While they are the same thing in technology it sometimes is preferred to write it as oh2 as it simply specifies the oxygen and not the hydrogen is bound to the central transition metal. This is a all a matter of specificity in making clear what is the bonding atom.
by stelang
Fri Nov 06, 2015 9:11 am
Forum: Lewis Structures
Topic: Lewis Structure of HClO3
Replies: 3
Views: 22287

Re: Lewis Structure of HClO3

The H atom would actually be bonded to one of the oxygen atoms that is connected to the chlorine atoms. One of the patterns for acidic molecules is that if there is an hydrogen it usually will want to form an O-H bond with one of the oxygens. For example, for the molecule HCLO4 the hydrogen is attac...
by stelang
Fri Nov 06, 2015 9:07 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond lengths
Replies: 3
Views: 633

Re: Bond lengths

We can determine bond lengths in a couple of ways. One way is looking at the Lewis structures of molecules. Another way is calculating the bond order. The point of utilizing these methods is to calculate exactly what type of bond is occurring between the atoms. We want to know if it is a single bond...
by stelang
Thu Oct 29, 2015 11:17 pm
Forum: Octet Exceptions
Topic: Double bonds on group 17 atoms
Replies: 2
Views: 1377

Re: Double bonds on group 17 atoms

For example, look at the Lewis structure of ClO3-. Cl forms two different double bonds with oxygen. However many times in fact group 17 elements in Lewis structures don't have double bonds. This is just due to the fact that having an octet allows the halogen to have a formal charge of 0. However thi...
by stelang
Thu Oct 29, 2015 11:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electron distortions
Replies: 2
Views: 413

Re: Electron distortions

Distortion are simply a product of atoms being highly polarizable or an atom having high polarizing power. Large anions have electrons which have the property of being highly distort able. Meanwhile small cations have the ability to distort electrons of other atoms. This property plays a key role in...
by stelang
Thu Oct 22, 2015 12:05 am
Forum: Resonance Structures
Topic: Lewis Structures w/ Nitrogen
Replies: 2
Views: 422

Re: Lewis Structures w/ Nitrogen

Remember that even though nitrogen can form a triple bond with itself it cannot have more than an octet. Thus, be careful when using multiple bonds for nitrogen and make sure you follow the octet rule.
by stelang
Fri Oct 16, 2015 12:09 am
Forum: Trends in The Periodic Table
Topic: Exceptions to trends in electron affinity
Replies: 1
Views: 1767

Re: Exceptions to trends in electron affinity

Like all other trends on the periodic table electronic affinity also has its exceptions. We simply have to know general trends and the fact that affinity grows higher the more right you move. However we do not need to know these specific nuances. In the hw for chapter 2 one of the problems goes over...
by stelang
Thu Oct 08, 2015 5:06 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Chapter 1 HW #57
Replies: 3
Views: 585

Re: Chapter 1 HW #57

Because the problem involves the Balmer series we know that the ground state will always be equal to 2. For the Lyman series the ground state always has the value of 1. If the first value of n is equal to 2 then each of the 4 provided wavelengths represent n=3 n=4 n=5 and n=6. The one after that is ...
by stelang
Fri Oct 02, 2015 3:27 pm
Forum: Properties of Electrons
Topic: Ground State
Replies: 2
Views: 573

Re: Ground State

They are sometimes given, but other times the problem might just mention the presence of ultraviolet or visible light. A hydrogen atom producing ultraviolet light is part of the Lyman series and thus the ground state is always 1, so n1=1. Meanwhile a hydrogen atom emitting or absorbing visible light...
by stelang
Fri Oct 02, 2015 3:22 pm
Forum: Properties of Light
Topic: HW #1.37
Replies: 2
Views: 1023

Re: HW #1.37

Like the mass of an electron they are both set values. The mass of a proton is around 1.6726*10^-27 kg and th mass of a neutron is around 1.6750*10^-27 kg.

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