Search found 51 matches

by Hazem Nasef 1I
Sat Mar 17, 2018 12:49 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 2014 Final 1C
Replies: 1
Views: 182

Re: 2014 Final 1C

That is the specific heat capacity of the Potion in terms of kilojoules. This is taken from part 1B, where it is mentioned in the question as 5.4 J/C.g. This is then converted to kilojoules.
by Hazem Nasef 1I
Sat Mar 17, 2018 12:28 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: phase diagram
Replies: 1
Views: 166

Re: phase diagram

I'll assume you are talking about heating curves since that is what is relevant to heat capacity. Since the x-axis is time, and the y-axis is temperature, a steep slope would mean it takes less time to reach a certain temperature than a slope that isn't steep. If something requires less time to reac...
by Hazem Nasef 1I
Sat Mar 17, 2018 12:23 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.3
Replies: 1
Views: 188

Re: 8.3

The change in internal energy for this problem is solely due to work from compression. There is no mention of using heat or increasing the temperature of the pump. Since the problem only speaks of compression work, it is assumed no heat was transferred.
by Hazem Nasef 1I
Fri Mar 09, 2018 9:07 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Frequency Factor
Replies: 1
Views: 227

Re: Frequency Factor

Two molecules have to collide in the correct orientation, meaning that specific places on one molecule must collide with another molecule in a certain location. The molecules can't just randomly collide in any location in order for the reaction to proceed. Think of it like plugging a plug into an ou...
by Hazem Nasef 1I
Fri Mar 09, 2018 10:29 am
Forum: First Order Reactions
Topic: 15.27
Replies: 2
Views: 147

Re: 15.27

Yes, you are correct. Starting with the original equation, if you move ln[A]0 to the other side, it becomes ln[A] - ln [A]0 and you are left with -kt on the other side. Dividing by the negative one will result in -ln[A] + ln[A]0, which can be rewritten as ln([A]0/[A]), which is equivalent to kt.
by Hazem Nasef 1I
Fri Mar 09, 2018 10:20 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Negative Order
Replies: 7
Views: 718

Re: Negative Order

A negative order means that as the concentration of that substance is increased, the rate of the reaction decreases. An example of this would be a product with a negative order. If the concentration of this product is increased, it participates in a reverse reaction, thereby slowing down the reactio...
by Hazem Nasef 1I
Sun Mar 04, 2018 4:23 pm
Forum: General Rate Laws
Topic: graphs
Replies: 2
Views: 110

Re: graphs

For a zero order reaction, a graph of [A] vs time will produce a straight line with a negative slope. For a first order reaction, a graph of ln([A]) vs time will produce a straight line with a negative slope. For a second order reaction, a graph of 1/[A] vs time will produce a straight line with a p...
by Hazem Nasef 1I
Sun Mar 04, 2018 4:20 pm
Forum: General Rate Laws
Topic: catalytic reaction
Replies: 5
Views: 151

Re: catalytic reaction

When hydrogen peroxide decomposes into water and oxygen gas, the process is quite slow. Adding the catalyst potassium permanganate will speed up the reaction, causing it to proceed almost instantly by using an alternate energy pathway that requires a lower activation energy.
by Hazem Nasef 1I
Sun Mar 04, 2018 3:53 pm
Forum: General Rate Laws
Topic: 2A --> B Rate Law
Replies: 1
Views: 188

Re: 2A --> B Rate Law

In the regular rate laws, it is assumed that the coefficients in front of the reactants and products are all 1. In this case, when the coefficient of the reactant is 2, then the differential rate law has a 1/2 in front of it. When this is integrated, there is now a 2 in front of the -k*t instead of ...
by Hazem Nasef 1I
Fri Feb 23, 2018 10:43 am
Forum: General Rate Laws
Topic: Negative sign in reactants
Replies: 6
Views: 868

Re: Negative sign in reactants

The reaction rate is represented as change in concentration over change in time. Since the concentration of reactants decreases as time goes on, the change in concentration is a negative value. To make the reaction rate a positive value, we always place a negative sign in front of the change in conc...
by Hazem Nasef 1I
Fri Feb 23, 2018 10:37 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert Electrode
Replies: 4
Views: 166

Re: Inert Electrode

You add an inert platinum electrode whenever there is no solid substance in a half-cell. For example, for the standard hydrogen electrode, aqueous hydrogen ions are reduced to hydrogen gas, so since there is no solid substance to serve as the electrode, which is why an inert platinum electrode is ne...
by Hazem Nasef 1I
Fri Feb 23, 2018 10:33 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: ln vs log [ENDORSED]
Replies: 5
Views: 197

Re: ln vs log [ENDORSED]

There is no difference in using log versus using ln. The main reason log is preferred is because it is used in measuring pH, so it is easier to keep the logarithm the same base across chemistry, rather than switching from ln to log.
by Hazem Nasef 1I
Sun Feb 18, 2018 12:16 pm
Forum: Balancing Redox Reactions
Topic: Basic v Acidic
Replies: 2
Views: 107

Re: Basic v Acidic

To balance in basic solution, first balance the half reactions as if they were in acidic solution and add them together. Then, add OH- ions to both sides in the same number which H+ions are present on one side. (i.e. if you have 6H+ ions, then add 6OH- ions to both sides) The side that has 6H+ and 6...
by Hazem Nasef 1I
Sun Feb 18, 2018 11:58 am
Forum: Balancing Redox Reactions
Topic: Standard Reduction Potentials Concept
Replies: 4
Views: 282

Re: Standard Reduction Potentials Concept

I understand that all values are for standard reduction potentials, but when using the Ecell=Ecathode-Eanode we plug in both values for the reduction potential of the equations from the anode and cathode even when we know the reaction at the anode is actually the reverse reaction since it is actual...
by Hazem Nasef 1I
Sun Feb 18, 2018 11:29 am
Forum: Balancing Redox Reactions
Topic: Balancing Half Reactions
Replies: 2
Views: 111

Re: Balancing Half Reactions

When balancing half-reactions, first balance all the elements except for hydrogen and oxygen. Then, balance any oxygens by adding the appropriate number of water molecules to the side opposite of the oxygens. Then, you balance the hydrogens from the water molecules by adding H+ ions to the side oppo...
by Hazem Nasef 1I
Fri Feb 09, 2018 11:38 pm
Forum: Administrative Questions and Class Announcements
Topic: Bruin Cast
Replies: 5
Views: 268

Re: Bruin Cast

Also, if you can find someone from previous years to buy the course reader from, it has all of the lecture slides in it.
by Hazem Nasef 1I
Fri Feb 09, 2018 11:26 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: disorder & entropy
Replies: 2
Views: 107

Re: disorder & entropy

An increase in disorder would correspond to an increase in entropy, since entropy is the number of different states a system can be in. For example, when a substance goes from a liquid to a gas, there is an increase in entropy of the system, since the collection of gas molecules can occupy a greater...
by Hazem Nasef 1I
Fri Feb 09, 2018 11:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibb's Free Energy
Replies: 2
Views: 101

Re: Gibb's Free Energy

When Gibb's Free energy is negative, this means that the process is spontaneous, in other words, one that will occur without any energy input from the surroundings. There are many examples of spontaneous processes in everyday life. Two of these would be iron rusting or the decay of radioisotopes.
by Hazem Nasef 1I
Sat Feb 03, 2018 10:57 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: entropy and heat capacity
Replies: 2
Views: 97

Re: entropy and heat capacity

Heat capacity is a measured value of the amount of heat required to raise an object's temperature by 1 degree Celsius, it is not a calculated value. (there is no formula) Entropy refers to the likelihood a system will be in a particular state. I don't believe there is any connection between the two ...
by Hazem Nasef 1I
Sat Feb 03, 2018 10:40 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm
Replies: 6
Views: 265

Re: Midterm

will anything about knowing how the equations were made up as shown in todays lecture need to be rememberes I think it is fair game for the midterm since it was covered during lecture. Normally, we aren't asked questions about derivations of formulas, but I would still be familiar with it to be safe.
by Hazem Nasef 1I
Sat Feb 03, 2018 10:34 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Degeneracy vs Disorder
Replies: 4
Views: 162

Re: Degeneracy vs Disorder

Degeneracy refers to the number of ways of achieving a given energy state. Disorder refers to the organization of atoms and molecules. They are similar in the fact that when either degeneracy (Boltzmann equation) or disorder increases, entropy also increases. Although they are similar properties, th...
by Hazem Nasef 1I
Fri Jan 26, 2018 8:57 pm
Forum: Calculating Work of Expansion
Topic: Internal Energy Change in Adiabatic Reversible Expansion vs Adiabatic Irreversible Expansion
Replies: 2
Views: 121

Re: Internal Energy Change in Adiabatic Reversible Expansion vs Adiabatic Irreversible Expansion

You are correct in that reversible expansions do more work than irreversible expansions. Although internal energy is a state property, both work and heat depend on the path taken, so they are not state properties. Work for a reversible expansion is nRT*ln(V2/V1) and is -P*deltaV for an irreversible ...
by Hazem Nasef 1I
Fri Jan 26, 2018 8:42 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: Calculating degeneracy(W)
Replies: 3
Views: 165

Re: Calculating degeneracy(W)

I believe normally that the number of states possible in a system would be given to you, or you would be able to deduce it from information given (i.e. the number of arrangements of molecules that result in the same energy) and you would have to calculate degeneracy. The degeneracy is given by the n...
by Hazem Nasef 1I
Fri Jan 26, 2018 8:37 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Relation of degeneracy and entropy
Replies: 2
Views: 116

Re: Relation of degeneracy and entropy

Increasing degeneracy results in an increase in entropy of the system. This is shown by the Boltzmann equation: S=kB*ln(W), where w is the degeneracy and S is entropy. Therefore, an increase in w increases the value of S, which is entropy. This also makes sense because degeneracy is the number of wa...
by Hazem Nasef 1I
Sun Jan 21, 2018 12:20 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.85 part b
Replies: 1
Views: 98

Re: 8.85 part b

You can use the conversion of about 22.7 L being equivalent to one mole of gas ONLY because this question is occurring under standard temperature (0 C) and pressure (1 atm). You get the same answer if you use it for this question. However, if the reaction is not occurring under these conditions, the...
by Hazem Nasef 1I
Sun Jan 21, 2018 12:14 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.65
Replies: 2
Views: 99

Re: 8.65

If you notice, in the original equation, it was just N2 reacting with 2.5 moles of O2 ( or 5 moles of O). In this second reaction, instead of N2, it is two moles of NO, which contains two moles of O, and then 1.5 moles of O2 (or 3 moles of O). So both equations essentially have 5 moles of O, but the...
by Hazem Nasef 1I
Sun Jan 21, 2018 12:01 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.37
Replies: 1
Views: 88

Re: 8.37

That is how they calculated the enthalpy of vaporization because these values are always reported per 1 mole. If you divide the the heat by the number of moles, you'll get the enthalpy per mole, which is the standard way of reporting it.
by Hazem Nasef 1I
Sun Jan 14, 2018 7:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpy Definition
Replies: 7
Views: 155

Re: Standard Reaction Enthalpy Definition

McKenna disc 1C wrote:So it can be at any temperature, so long as the substances are existing in their standard state? Thanks!

Yes, that is correct. However, most of the time, the reported data is for 25 degrees celsius.
by Hazem Nasef 1I
Sun Jan 14, 2018 7:20 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: Born Habers Cycle [ENDORSED]
Replies: 4
Views: 203

Re: Born Habers Cycle [ENDORSED]

The Born Haber cycle is a way of breaking up the lattice enthalpy into smaller processes, whose values are known. The lattice enthalpy is equivalent to the sum of the enthalpy of atomization of the cation, enthalpy of atomization of the anion, the ionization energy of the cation, the electron affini...
by Hazem Nasef 1I
Sun Jan 14, 2018 6:55 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpies of Physical Change
Replies: 2
Views: 87

Re: Standard Enthalpies of Physical Change

No, my TA told us that any values like these necessary for a problem will be given to you.
by Hazem Nasef 1I
Wed Dec 06, 2017 11:48 pm
Forum: Bronsted Acids & Bases
Topic: Oxoacids
Replies: 4
Views: 217

Re: Oxoacids

It's not necessarily having more oxygens, but rather having more atoms that stabilize the anion by withdrawing delocalizing the negative charge. For example, as Dr. Lavelle discussed in class, trichloroacetic acid (an acetic acid molecule in which the three hydrogen atoms are replaced with chlorine ...
by Hazem Nasef 1I
Wed Dec 06, 2017 11:34 pm
Forum: Lewis Acids & Bases
Topic: BF3 [ENDORSED]
Replies: 2
Views: 186

Re: BF3 [ENDORSED]

A lewis acid is a species which accepts electron pairs. BF3 is electron deficient, because it only has 6 valence electrons. It has room to form a coordinate covalent bond, by accepting an electron pair from a lewis base, such as ammonia, which has a lone pair of electrons.
by Hazem Nasef 1I
Thu Nov 30, 2017 10:29 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi bonds
Replies: 5
Views: 304

Re: Sigma and Pi bonds

Yes, you are correct. Whenever a compound has resonance, this means that a double or triple bond can be found in multiple locations in the compound. That second or third bond is always a pi bond, and when there is resonance, that means that the electrons involved in the pi bond are delocalized.
by Hazem Nasef 1I
Thu Nov 30, 2017 10:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.7 Part C
Replies: 2
Views: 164

Re: 11.7 Part C

Although if you count the number of atoms and molecules, it seems to have increased, no extra molecules have been inserted into the flask. All that happened was that 3 of the molecules have dissociated into atoms, so the actual amount of substance has not changed. Therefore, the pressure remains con...
by Hazem Nasef 1I
Tue Nov 21, 2017 2:59 pm
Forum: Naming
Topic: Ligand Names
Replies: 6
Views: 232

Re: Ligand Names

It seems that for the anionic ligands in the table, they can be named without memorization as the same rule applies: change the -ide to -ido, the -ate to -ato, and the -ite to -ito. As far as the neutral ligands, we should definitely know the prefix for water and ammonia as those were on the homewor...
by Hazem Nasef 1I
Tue Nov 21, 2017 2:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: CH2CL2 4.25
Replies: 2
Views: 99

Re: CH2CL2 4.25

When you draw the 2-D lewis structure, the chlorines can be placed opposite each other, and it appears that the dipoles cancel. However, CH2Cl2 is a 3-D molecule arranged in a tetrahedral shape. No matter how you arrange the chlorine atoms and hydrogen atoms, the dipoles will never be completely opp...
by Hazem Nasef 1I
Fri Nov 17, 2017 10:31 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Number of Ligands
Replies: 1
Views: 106

Re: Number of Ligands

The simplest coordination compounds are linear with a coordination number of 2. Coordination numbers as high as 12 are found with elements of the f-block, but are rare in the d-block.
by Hazem Nasef 1I
Fri Nov 17, 2017 10:11 pm
Forum: Hybridization
Topic: dsp3
Replies: 1
Views: 121

Re: dsp3

The d subshell consists of five orbitals. Three of them have 4 lobes of electron density located in the XY, YZ, and ZX planes. One of them has lobes of electron density along the X and Y axis. The last one has lobes of electron density along the Z axis and and a donut shape of electron density in th...
by Hazem Nasef 1I
Sat Nov 11, 2017 12:17 am
Forum: Dipole Moments
Topic: Drawing dipole moments [ENDORSED]
Replies: 3
Views: 259

Re: Drawing dipole moments [ENDORSED]

There's two conventions for drawing the dipoles. The classic convention is to draw the arrow pointing towards the negative partial charge. The modern convention is to draw the arrow pointing towards the positive partial charge. Both are valid, but since Dr. Lavelle showed us the classic convention, ...
by Hazem Nasef 1I
Sat Nov 11, 2017 12:09 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape Memorization [ENDORSED]
Replies: 7
Views: 365

Re: Shape Memorization [ENDORSED]

I would say a good way to memorize them is to organize the shapes by electron domain geometry. Then, you should know that there are shapes whose molecular geometry matches its electron domain geometry, and shapes with one or more lone pairs replacing an atom. For example, for tetrahedral electron do...
by Hazem Nasef 1I
Sat Nov 04, 2017 2:36 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic or Covalent?
Replies: 4
Views: 197

Re: Ionic or Covalent?

Yes, you can look at the distance between the two elements on the periodic table. For example, sodium and chlorine are on opposite sides of the periodic table, so you can know that the electronegativity difference will be quite large and an ionic bond will form. As opposed to nitrogen and oxygen, wh...
by Hazem Nasef 1I
Sat Nov 04, 2017 2:20 pm
Forum: Lewis Structures
Topic: Expanded Octet
Replies: 3
Views: 146

Re: Expanded Octet

Formal charge is basically the charge that an atom would have if the bond it formed is perfectly covalent. Basically, that means it's the charge that the atom would have it "owned" its lone pair electrons and "owned" half the number of shared electrons. When formal charge is 0, t...
by Hazem Nasef 1I
Fri Oct 27, 2017 10:06 pm
Forum: Administrative Questions and Class Announcements
Topic: Weekly online discussion points
Replies: 3
Views: 235

Re: Weekly online discussion points

My homework points are inputted on MyUCLA. I think it just depends on your TA, and if they want to put them in weekly or at the end.
by Hazem Nasef 1I
Wed Oct 25, 2017 9:31 pm
Forum: General Science Questions
Topic: Problems
Replies: 1
Views: 412

Re: Problems

You should complete problems related to the topics covered in lecture this week. We've been finishing up chapter 2, so you should probably do problems from the end of the assigned problems of chapter 2 that we covered this week. The chapter 2 problems are: 1, 13, 17, 19, 21, 23, 25, 27, 29, 31, 33, ...
by Hazem Nasef 1I
Thu Oct 19, 2017 3:01 pm
Forum: Properties of Electrons
Topic: h variable
Replies: 2
Views: 227

Re: h variable

The lower case "h" represents Planck's constant in equations like De Broglie's equation and the Bohr frequency condition. Frequency is represented by a lower case Nu, which looks like a lower case "v". Frequency doesn't tend to be represented by h.
by Hazem Nasef 1I
Thu Oct 19, 2017 2:58 pm
Forum: Properties of Light
Topic: the quantum world [ENDORSED]
Replies: 3
Views: 241

Re: the quantum world [ENDORSED]

Essentially, electromagnetic radiation can act as both a wave or a particle, depending on the situation. This was shown for example in the photoelectric effect, when the incident UV radiation on the metal acted as photons of light, rather than waves, with each individual photon requiring enough ener...
by Hazem Nasef 1I
Thu Oct 19, 2017 2:47 pm
Forum: Administrative Questions and Class Announcements
Topic: Course Reader
Replies: 3
Views: 274

Re: Course Reader

They stopped selling them in order to cut down on costs for students.
by Hazem Nasef 1I
Sat Oct 14, 2017 12:41 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Doubt [ENDORSED]
Replies: 4
Views: 210

Re: Photoelectric Effect Doubt [ENDORSED]

The intensity of the light is essentially the amplitude. Increasing the intensity increases the number of photons hitting the metal. Originally, it was expected that if a certain intensity of UV light didn't remove electrons from the metal, then increasing the intensity of the light (or number of ph...
by Hazem Nasef 1I
Sat Oct 14, 2017 12:34 pm
Forum: Properties of Light
Topic: Balmer Vs. Lyman
Replies: 12
Views: 755

Re: Balmer Vs. Lyman

What relationship do these series have with the elements? Do all elements have these series? Are the different series only referring to the electrons? The Balmer and Lyman series are specific only to the hydrogen atom, not other elements. They represent the transitions of hydrogen's electron betwee...
by Hazem Nasef 1I
Tue Oct 10, 2017 4:13 pm
Forum: Limiting Reactant Calculations
Topic: Finding Excess Reactant [ENDORSED]
Replies: 2
Views: 204

Re: Finding Excess Reactant [ENDORSED]

If you were asking about how to find how much reactant is actually remaining, you would use the limiting reactant to find the moles of excess reactant actually used. Then, you would subtract how much was used from the amount of the excess reactant to find how much excess reactant is left over.
by Hazem Nasef 1I
Tue Oct 10, 2017 3:54 pm
Forum: Administrative Questions and Class Announcements
Topic: Where to find Bruincast?
Replies: 3
Views: 336

Re: Where to find Bruincast?

Whenever I click on the Chemistry 14A site at CCLE it goes directly to Professor Lavelle's website, and I cant find the link for media resources on his website anywhere. Where should I go? I joined the class late, so I missed three lectures. I also could not find the link for media resources since ...

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