Search found 17 matches

by rachaeld_1D
Fri Jan 23, 2015 9:36 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy of ice to water
Replies: 1
Views: 1283

Gibbs Free Energy of ice to water

Why is the Gibbs free energy for the reaction of ice to water at 1 atm at 0 degrees C 0?

Delta H is positive (endothermic reaction because heat has to be added)
Delta S is positive (more chaos)

G=H-TS, so if T=0, wouldn't G=H?
by rachaeld_1D
Fri Jan 23, 2015 9:20 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculating standard reaction enthalpy
Replies: 2
Views: 468

Calculating standard reaction enthalpy

Say we are given the equation 3Al(s)+3NH4ClO4(s)--> Al2O3(s)+AlCl3(s)+NO(g)+6H2O(g) and asked to calculate the standard delta H for the reaction. After looking up the enthalpies and summing the enthalpies for each product (multiplyie by the number of moles) and subtracting the sum of the reactants (...
by rachaeld_1D
Wed Jan 14, 2015 4:50 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Does a monatomic atom have rotational motion?
Replies: 3
Views: 1111

Does a monatomic atom have rotational motion?

For a monatomic atom, would the total motional contribution to the internal energy be the sum of the rotational and translational energy? Or would it just be the translational energy because a single molecule doesn't store much energy as it spins by itself?
by rachaeld_1D
Mon Dec 08, 2014 11:27 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: strength of an acid
Replies: 1
Views: 386

strength of an acid

In the book, it says, "the greater the electronegativity of A, the stronger the acid HA." Why is this the case? I thought that the higher the electronegativity of A, the stronger the bond between H--A; therefore, the weaker the acid. In the course reader it says that HCl is more acidic tha...
by rachaeld_1D
Mon Dec 01, 2014 3:52 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate Question
Replies: 5
Views: 699

Re: Polydentate Question

For that question, why is water always monodentate? Its lewis structure has two lone pairs, so shouldn't it be bidentate?
by rachaeld_1D
Wed Nov 26, 2014 10:28 am
Forum: Naming
Topic: Are we expected to name cis and trans molecules?
Replies: 3
Views: 569

Re: Are we expected to name cis and trans molecules?

As you mentioned, you said to put cis or trans before the compound name, so you write cis-(molecules name)? Do you know if we would be expected to draw these structures?
by rachaeld_1D
Fri Nov 21, 2014 4:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Conceptional Question abut Equilibrium Constant
Replies: 2
Views: 386

Re: Conceptional Question abut Equilibrium Constant

In the course reader (page 114), it says to omit section 10.3, which covers Gibbs Energy and the relationship to K. But, it you want to know, look at page 393 in the text book.
by rachaeld_1D
Tue Nov 11, 2014 7:00 pm
Forum: Trends in The Periodic Table
Topic: Which compound is more ionic?
Replies: 7
Views: 15097

Re: Which compound is more ionic?

How would we know that LiH is more ionic than HCl if we didn't have the electronegativity of these elements memorized? H and Cl is farther away on the period table than H and Li.
by rachaeld_1D
Sun Nov 09, 2014 1:55 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Hund's Rule for Z<8 molecular orbital energy diagram
Replies: 1
Views: 478

Hund's Rule for Z<8 molecular orbital energy diagram

Say we are doing the molecular orbital diagram for CO (Dr. Lavelle did this in his review session). There are 14 electrons that need to go into the diagram. 2 go into sigma 1s 2 go into sigma* 1s 2 go into sigma 2s 2 go into sigma* 2s (8 electrons used so far) 1 goes into pi 2x 1 goes into pi 2y The...
by rachaeld_1D
Tue Nov 04, 2014 9:43 am
Forum: Dipole Moments
Topic: Dipole trend
Replies: 1
Views: 345

Re: Dipole trend

In lecture, Dr. Lavelle said that dipole depends on the magnitude of charge, which depends on electronegativity. Electronegativity decreases as you go down the periodic table.
by rachaeld_1D
Tue Nov 04, 2014 9:39 am
Forum: Ionic & Covalent Bonds
Topic: Ionic radius
Replies: 2
Views: 386

Re: Ionic radius

I don't think we need to know exact values for the ionic radius, but we have to know the general trends.
by rachaeld_1D
Mon Nov 03, 2014 10:16 pm
Forum: Lewis Structures
Topic: Question 2.95 in the textbook
Replies: 1
Views: 357

Question 2.95 in the textbook

Question 95 is asking us to draw a N5+ cation and its resonance structures. Looking in the answer key, how is it possible for N to have a triple bond with another N atom and a single bond with a different N atom. Since N has 5 valence electrons, doesn't it only form three bonds? How is it forming 4 ...
by rachaeld_1D
Thu Oct 30, 2014 11:57 am
Forum: Ionic & Covalent Bonds
Topic: Dissociation Energies
Replies: 1
Views: 344

Dissociation Energies

Do we need to know the dissociation energies between atoms? Or just know the general trends for these values?
by rachaeld_1D
Thu Oct 23, 2014 4:51 pm
Forum: Lewis Structures
Topic: Bond Lengths
Replies: 1
Views: 283

Bond Lengths

In the lewis structure of NO3, why did Dr. Lavelle say that the bond lengths are the same? Aren't double bonds shorter than single bonds? And, in Benzene, shouldn't the double bonds be shorter than the single bonds?
by rachaeld_1D
Sat Oct 18, 2014 11:18 am
Forum: Photoelectric Effect
Topic: Fall 2013 Practice Test Number 10
Replies: 1
Views: 4702

Fall 2013 Practice Test Number 10

If molybdenum is irradiated with light of wavelength of 194 nm, what is the maximum possible kinetic energy of the emitted electrons? We know from the previous problem that Molybdenum metal absorbs radiation with minimum frequency of 1.09x10^15 s^-1. And that the minimum energy (E=hv) is 7.22 x 10^-...
by rachaeld_1D
Fri Oct 10, 2014 9:52 am
Forum: Limiting Reactant Calculations
Topic: Neutralizing Acid Spill
Replies: 1
Views: 867

Neutralizing Acid Spill

On question 8 of the review self test, the question is: How many moles of CO2 (g) is produced when 500g a of CaCO3 (s) is used to neutralize an acid spill? The equation for the reaction at 1 atm and 25 degrees C is: CaCO3 (s) + H2SO4 (aq)--> CaSO4 (s) + CO2 (g) + H2O (l) Because the reaction is at S...
by rachaeld_1D
Thu Oct 09, 2014 3:48 pm
Forum: *Black Body Radiation
Topic: What is "black body radiation?"
Replies: 8
Views: 1139

Re: What is "black body radiation?"

Do we just have to know this about black body radiation for chem 14A?
Chem_Mod wrote:Answer: "Black body radiation" refers to the radiation that originates from the thermal energy of the body that is heated.

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