Search found 20 matches

by Christopher Lew 1L
Mon Mar 07, 2016 9:33 am
Forum: *Electrophiles
Topic: Why is F electrophile?
Replies: 5
Views: 965

Re: Why is F electrophile?

Electrophile is something that is electron deficient. For F it has 7 valence electron and an unfilled p orbital. It wants to find something that is electron rich or nucleophilic to satisfy an octet
by Christopher Lew 1L
Mon Mar 07, 2016 9:24 am
Forum: *Nucleophiles
Topic: Strength of Nucelophile
Replies: 3
Views: 454

Re: Strength of Nucelophile

As you go down a group, the strength of the ability of an atom to hold an electron decreases. Remember that when you go down a group you encounter larger orbitals that are farther and farther away. This means that the electrons are farther from the nucleus and thus have a weaker hold to the nucleus.
by Christopher Lew 1L
Mon Mar 07, 2016 9:18 am
Forum: *Electrophiles
Topic: Memory Tips
Replies: 8
Views: 1053

Re: Memory Tips

Nucleophiles -> Nucleus-> positive-> phile -> wants positive stuff -> electron rich
Electrophiles -> Electron -> negative ->phile -> wants negative stuff -> electron deficient
by Christopher Lew 1L
Sat Feb 20, 2016 4:45 pm
Forum: General Rate Laws
Topic: Catalyst vs intermediate
Replies: 2
Views: 439

Re: Catalyst vs intermediate

A catalyst lowers the activation energy of a reaction and pretty much never undergoes a chemical change as a result of the reaction. It provides a new pathway for the reaction which requires less energy. However, an intermediate is the substance that is formed briefly before reacting again to form a...
by Christopher Lew 1L
Sat Feb 20, 2016 4:26 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Unit of rate constant
Replies: 2
Views: 1482

Re: Unit of rate constant

Its best not to go about memorizing the units of for the rate constants since the units vary depending on the order of the reaction. If you are given the rate constant then great. However, when it is not given it is best that you go and calculate it. Solve for k and you will end up canceling and add...
by Christopher Lew 1L
Fri Feb 05, 2016 9:56 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox reactions
Replies: 3
Views: 500

Re: Balancing Redox reactions

You do not double the cell potential because cell potential is an intensive property. An intensive property is a fancy way of saying that it doesn't matter how much of a substance there is. So if you had x amount of a substance and y value for cell potential, then if you had 2x of a substance it wou...
by Christopher Lew 1L
Sun Jan 31, 2016 3:39 pm
Forum: Calculating Work of Expansion
Topic: w=-PdeltaV Equation
Replies: 2
Views: 5162

Re: w=-PdeltaV Equation

Lets look at it using the equation, If w is negative, then it is likely that the change in volume (DeltaV) is positive. Therefore, the final volume of the gas is larger than its initial value. The system has to use some of its energy to do work. If w is positive, then it is likely that the change in...
by Christopher Lew 1L
Fri Jan 22, 2016 9:02 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Positive and Negative Work Values
Replies: 1
Views: 743

Re: Positive and Negative Work Values

When the "system" does work, the value for work will be negative. When work is performed on the "system", the value for work is positive. If you want to create change, or work, you have to convert some of your energy. There is an overall net decrease in your total energy which is...
by Christopher Lew 1L
Sat Jan 16, 2016 12:12 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Kelvin and degrees celcius
Replies: 4
Views: 483

Re: Kelvin and degrees celcius

A different way to look at the conversion is to look at it mathematically. Look at the 263.15 that you have to add to Celsius to make Kelvin as a constant. The difference of 1 degree is of the same amount for both Celsius and Kelvin. Celsius is Kelvin without 263.15 added onto it.
by Christopher Lew 1L
Sat Jan 09, 2016 2:33 pm
Forum: Phase Changes & Related Calculations
Topic: Celsius to Kelvin conversion
Replies: 2
Views: 653

Re: Celsius to Kelvin conversion

For simplicity, Lavelle had in his course reader for 14A:

Kelvin = Celsius + 273.15

Since 273.15 is a constant no matter what unit you use the difference for your problem will be 80 units regardless of whether you used Celsius or Kelvin.
by Christopher Lew 1L
Mon Nov 30, 2015 9:13 pm
Forum: Conjugate Acids & Bases
Topic: Memorizing types of acids/bases
Replies: 3
Views: 758

Re: Memorizing types of acids/bases

For the most part I believe everyone probably saying the right things. To be safe know the ones in the course reader or at least be familiar with them. Other than that it might be beneficial to be comfortable with the general trends of the acids and bases. As for the molecular formulas we will proba...
by Christopher Lew 1L
Sat Nov 21, 2015 6:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Converting from Moles to Pressure
Replies: 3
Views: 521

Re: Converting from Moles to Pressure

Yes you would have to convert the concentrations to pressure by using the formula PV=nRT, or for our purposes: P=\frac{nRT}{V} You would also have to use the right gas constant known as R. For our class we use R = 8.206 \ast 10^{-2} L.atm. K^{-1} Knowing this information we then apply the ideal gas ...
by Christopher Lew 1L
Sat Nov 14, 2015 8:06 pm
Forum: Ideal Gases
Topic: Homogeneous vs heterogeneous
Replies: 3
Views: 698

Re: Homogeneous vs heterogeneous

The easiest way that I recognize whether a reaction is homogeneous or heterogeneous is by recognizing whether both the reactants and products are in the same state. If a single reactant or product is different the reaction is described as being a heterogeneous reaction. Homogeneous reaction - a reac...
by Christopher Lew 1L
Sat Nov 07, 2015 10:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AX2E3 Shape
Replies: 7
Views: 1825

Re: AX2E3 Shape

The VESPR shape for AX2E3 is linear. Molecular shape and structure is named based on the positions of the atoms. For AX2E3, think of it as first having a structure of AX5, or trigonal bipyramidal, as there are 5 regions of electron density. Then remove 3 areas where there are atoms as they are occup...
by Christopher Lew 1L
Sat Oct 31, 2015 8:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Octet Rule
Replies: 1
Views: 491

Re: Octet Rule

Boron is an exception to the octet rule. Looking at the periodic table we see that boron has 3 valence electrons. This means that boron is likely to pair these 3 electrons and form 3 covalent bonds by sharing them. Thus boron is "trivalent". Some common compounds for boron include BF3 and ...
by Christopher Lew 1L
Sat Oct 24, 2015 9:14 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Memorization
Replies: 4
Views: 1849

Re: Memorization

My TA said that it would be a good idea to be able to recognize as many polyatomic ions as you can, but for this class the questions will give you the molecular formula. Its only once we really start to get into the next classes of chemistry that we will probably need to be able to recognize them. H...
by Christopher Lew 1L
Sat Oct 17, 2015 10:12 pm
Forum: SI Units, Unit Conversions
Topic: How do you go from meter to nanometer? [ENDORSED]
Replies: 7
Views: 1677

Re: How do you go from meter to nanometer? [ENDORSED]

As everyone else has stated, 1 nanometer is equal to 1 x 10^-9m. The course reader gives a useful equation for conversions: Information Required = Information Given x \frac{Units Required}{Units Given} For example 256cm^2 to square meters Area (M^2) = 256 cm^2 x ( \frac{1m}{100cm} )^2 = 2.56 x 10^-2...
by Christopher Lew 1L
Wed Oct 07, 2015 8:03 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Exceptions when writing e- configurations
Replies: 3
Views: 577

Re: Exceptions when writing e- configurations

On the off chance that copper does gain an electron, the electron will fill the 4s orbital. I believe Tanera is correct as it does make sense that the 3d orbital is filled up at that point and that the orbital continue to fill the lowest available energy states. In addition, she does pose a very goo...
by Christopher Lew 1L
Sat Oct 03, 2015 7:27 pm
Forum: Balancing Chemical Reactions
Topic: States of Matter In Chemical Equations
Replies: 2
Views: 531

Re: States of Matter In Chemical Equations

Annie is correct. For most chemical reactions, correct me if i'm wrong, but we assume that they are taking place under room temperature unless stated otherwise. The question will have to specifically tell you that the reaction is being performed under a specific condition. So, we just assume that th...
by Christopher Lew 1L
Thu Oct 01, 2015 8:55 pm
Forum: Molarity, Solutions, Dilutions
Topic: Why doesn't a solute add to the volume of a solution? [ENDORSED]
Replies: 6
Views: 2869

Re: Why doesn't a solute add to the volume of a solution? [ENDORSED]

That is right, the change in volume when the solute is added is so small that there is basically no significant change to the overall volume.

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