## Search found 25 matches

Sat Mar 12, 2016 4:07 pm
Forum: Second Order Reactions
Topic: Decay for Non- First Order Reactions
Replies: 1
Views: 312

### Re: Decay for Non- First Order Reactions

You can do this for a first order reaction because the half life doesn't depend on the initial concentration of A. However, the half-lives for zero and second order do depend on the initial concentration of A, so you would need to use the equations to solve.
Wed Mar 02, 2016 11:49 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: Activation Energy and Temperature
Replies: 1
Views: 370

### Re: Activation Energy and Temperature

On page 154 of the organic textbook, it states that reactions with activation energies below 80kJ/mol can occur at room temperature, but those with larger activation energies require energy input to occur.
Sat Feb 27, 2016 10:26 pm
Forum: *Alkanes
Topic: General rule for direction
Replies: 3
Views: 362

### Re: General rule for direction

You need to go in the direction that will give the lowest number to the substituents. Then you put the substituents in alphabetical order.
Wed Feb 17, 2016 10:50 pm
Forum: General Rate Laws
Topic: 15.27
Replies: 1
Views: 383

### Re: 15.27

Since it's a first order reaction, the initial concentration doesn't affect the half life, so you can use this method. 1/8 is 3 half lives, so to find the time it takes to reach 1/8th of the initial concentration, you would multiply 3 by 355s. You can also use the half life equation to find k, and t...
Mon Feb 08, 2016 9:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Winter 2011 Midterm, Question 2A
Replies: 1
Views: 265

### Re: Winter 2011 Midterm, Question 2A

In the first equation, the HCl is (aq) and in the 3rd it is HCl (g), so they wouldn't cancel. That's why you need to use the 2 other equations too.
Sat Feb 06, 2016 11:59 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: HW 14.35 Nernst Equation Significant Figures
Replies: 1
Views: 418

### HW 14.35 Nernst Equation Significant Figures

When using the Nernst equation, how do we determine the number of significant figures?
Why does the final answer in hw 14.35 have only 1 significant figure?
Fri Feb 05, 2016 10:35 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs irreversible work
Replies: 2
Views: 552

### Re: Reversible vs irreversible work

In a reversible reaction, energy is not lost as heat. In an irreversible reaction, some energy is lost as heat.
Mon Jan 25, 2016 10:16 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Calculating the number of microstates
Replies: 2
Views: 2412

### Re: Calculating the number of microstates

In bromobenzene, there is a H attached to 5 of the carbons and Br attached to one of the carbons. So there would be 6 possible orientations, so the number of micro states would be 6.
Sat Jan 23, 2016 6:30 pm
Forum: Phase Changes & Related Calculations
Topic: Calculating w, q, and delta U
Replies: 1
Views: 1255

### Re: Calculating w, q, and delta U

Since it is isothermal, the temperature is constant and deltaU is equal to zero.
since it is a reversible reaction, use w= -nRT ln(V2/V1)
You will find that w= -5.48 kJ
deltaU = q + w
0 = q + w
q = -w
q = +5.48 kJ
Fri Jan 22, 2016 10:40 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat Curve
Replies: 1
Views: 268

### Re: Heat Curve

1) First you have to raise the temperature of the block of ice to 0 degrees C. use the formula deltaH= mC deltaT 2) Melt the ice at O degreesC (the temperature is constant at this point) multiply the number of moles by the enthalpy of fusion of water 3) Raise the temperature of the liquid from 0 deg...
Fri Jan 22, 2016 10:18 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy and Compression
Replies: 1
Views: 281

### Re: Entropy and Compression

When you compress something, the volume decreases. When volume decreases, entropy becomes negative because a smaller volume is less likely to be disordered than a large volume.
Tue Jan 12, 2016 4:43 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Work in Reversible Process vs Work in Irreversible Process
Replies: 3
Views: 699

### Re: Work in Reversible Process vs Work in Irreversible Proce

In a reversible process, you don't lose energy as heat, while in an irreversible process, some energy is lost as heat.
Sat Jan 09, 2016 9:30 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: First Law of Thermodynamics
Replies: 1
Views: 370

### Re: First Law of Thermodynamics

The first law of thermodynamics states that "The internal energy of an isolated system is constant" meaning that there is conservation of energy. They both state the same concept of energy being conserved.
Fri Dec 04, 2015 12:44 am
Forum: *Titrations & Titration Calculations
Topic: HW 13.23 volume at halfway point
Replies: 1
Views: 509

### Re: HW 13.23 volume at halfway point

The volume at the halfway point is always half the volume of the stoichiometric point. Since it is 10ml at the stoichiometric point, the volume at the halfway point would be 5ml.
Tue Dec 01, 2015 3:13 pm
Forum: Amphoteric Compounds
Topic: Oxides: Basic, acidic, or amphoteric
Replies: 1
Views: 452

### Re: Oxides: Basic, acidic, or amphoteric

Metals form basic oxides (CaO)
Nonmetals form acidic oxides (SO3)
Metalloids form amphoteric oxides (As2O3) These are located on the diagonal line between metals and nonmetals.
Page 469 in the book gives more examples.
Sat Nov 28, 2015 2:10 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: length of nod correspondence
Replies: 1
Views: 376

### Re: length of nod correspondence

Yes, the weaker (longer) the bond, the stronger the acid because it is easier to remove the H+ For example, HBr is more acidic than HCl because it has a longer bond. Bond length increases as you go down because of a larger atomic radii. But bond length isn't the only factor that affects acidity. For...
Mon Nov 23, 2015 7:08 pm
Forum: Bronsted Acids & Bases
Topic: Molecular Form?
Replies: 1
Views: 345

### Re: Molecular Form?

If a substance is a weak acid or base, then it doesn't completely dissociate and that's why you would leave it in its molecular form. For part a) HF is a weak acid so it would stay as HF(aq) in the ionic equation (writing it as HF is the molecular form) NaOH is a strong base and therefore dissociate...
Sat Nov 21, 2015 6:55 pm
Forum: Lewis Acids & Bases
Topic: Lewis Acids and Bases
Replies: 1
Views: 395

### Re: Lewis Acids and Bases

There are certain strong acids and bases that you should memorize and there's a list in the course reader on page 151. Acids such as HCL, HBr, HI are strong. Alkali metal hydroxides (LiOH, NaOH, KOH) and heavier alkaline earth metal hydroxides are strong bases. Organic compounds are usually weak.
Tue Nov 10, 2015 3:17 pm
Forum: Naming
Topic: [Co(CN)5(OH2)2]2-
Replies: 1
Views: 792

### Re: [Co(CN)5(OH2)2]2-

When naming, you name them alphabetically based on the ligand name (ignore the prefixes). So alphabetically, aqua comes before cyanido. In [Co(SO4)(NH3)5]+ the charge for Co is 3+ because the overall charge needs to be +1 (NH3)5 has a charge of 0. (SO4) has a charge of 2- So Co has to be 3+ in order...
Wed Nov 04, 2015 10:44 am
Forum: Octet Exceptions
Topic: Boron Octet Exception HW 4.81
Replies: 2
Views: 622

### Boron Octet Exception HW 4.81

When does Boron have less than an octet? In problem 4.81, it asks to draw the lewis structure of borazine (B3N3H6). The solution shows alternating double bonds between boron and nitrogen and a charge of +1 on N and -1 on B. If the structure is drawn with all single bonds and a lone pair on the Nitro...
Sat Oct 31, 2015 2:33 pm
Forum: Sigma & Pi Bonds
Topic: Paramagnetic
Replies: 1
Views: 382

### Re: Paramagnetic

B2- has 7 valence electrons. It has 2 electrons in the sigma 2s bonding orbital, 2 electrons in the sigma 2s antibonding orbital, 2 electrons in the pi 2px bonding orbital and 1 electron in the pi 2py bonding orbital (this is the unpaired electron).
Sat Oct 24, 2015 10:01 pm
Forum: Ionic & Covalent Bonds
Topic: Ground-State Electron Configurations of Ions 3.11
Replies: 2
Views: 1537

### Re: Ground-State Electron Configurations of Ions 3.11

a) The configuration for Co is [Ar] 3d^7 4s^2 To become C0^3+, it loses the two electrons in 4s, and then 1 electron from the d orbital and the final configuration will be [Ar]3d^6 b)The configuration for Fe is [Ar] 3d^6 4s^2 To become Fe^3+, Fe will lose the two electrons in 4s, and then lose one e...
Sun Oct 18, 2015 12:25 pm
Forum: Octet Exceptions
Replies: 1
Views: 343

How do we determine which species are radicals?
Fri Oct 09, 2015 3:53 pm
Forum: Trends in The Periodic Table
Topic: Ionization energy for oxygen hw 2.81
Replies: 3
Views: 575

### Ionization energy for oxygen hw 2.81

Why does oxygen have a lower ionization energy than nitrogen?
Sun Oct 04, 2015 4:05 pm
Forum: Limiting Reactant Calculations
Topic: 2 Questions from M. Limiting Reactants
Replies: 5
Views: 2799

### Re: 2 Questions from M. Limiting Reactants

When finding empirical and molecular formulas, when is it necessary to find the mass percent composition of each element and assume a 100g sample?