Search found 50 matches

by Danah Albaaj 1I
Sun Mar 18, 2018 9:38 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7606
Views: 1017637

Re: Post All Chemistry Jokes Here

This is what I picture the dilute saying whenever a precipitate forms in a concentration cell.
by Danah Albaaj 1I
Wed Mar 14, 2018 3:59 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Isothermal Changes
Replies: 2
Views: 163

Re: Isothermal Changes

With an isothermal process, the heat is equal to the opposite of the work value, remember the equation ∆U=q+w. The first law of thermodynamics, relating to the law of conservation of matter and energy explains why when a process is isothermal ∆U=0, q=-w. As long as you are capable of calculating the...
by Danah Albaaj 1I
Wed Mar 14, 2018 3:54 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: adiabatic process
Replies: 5
Views: 365

Re: adiabatic process

Well, because both open and closed systems are capable of exchanging energy with their surroundings this means either one could have an adiabatic process. Heat is a form of energy, as long as the system has the capability to exchange energy, it will also have the possibility of being an adiabatic pr...
by Danah Albaaj 1I
Sun Mar 11, 2018 10:02 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy and heat
Replies: 2
Views: 122

Re: Internal Energy and heat

If a system is isothermal we can be positive there is no change in the system's internal energy because of the equation U=3/2nRT. This does not mean that the system could have no change in heat, because if the system is adiabatic as well there would be no change in heat.
by Danah Albaaj 1I
Sat Mar 10, 2018 12:12 pm
Forum: Calculating Work of Expansion
Topic: 8.11-is part A isothermal too? [ENDORSED]
Replies: 1
Views: 145

Re: 8.11-is part A isothermal too? [ENDORSED]

The irreversible equation is not isothermal because the -nRT within the equation for reversible, isothermal expansion is in a way replacing the Pex from the irreversible equation. The isothermal is used to make -nRT a constant during the integration of the volume of the reversible expansion (pg 265 ...
by Danah Albaaj 1I
Sat Mar 10, 2018 11:49 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: HW 15.47
Replies: 2
Views: 98

Re: HW 15.47

You just have to look at the molecules within each step, and check to see if any are repeated within the product of one step and the reactant of another. This would make them an intermediate of the reaction. If you still struggle with determining the intermediates and the overall reaction, you could...
by Danah Albaaj 1I
Sun Mar 04, 2018 6:40 pm
Forum: General Rate Laws
Topic: 15.15
Replies: 2
Views: 129

Re: 15.15

The reaction would be first order because the reaction rate is increased in direct proportion to each reactant's concentration.
by Danah Albaaj 1I
Sun Mar 04, 2018 5:23 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.29
Replies: 1
Views: 82

Re: 15.29

No, because we are able to set up similar equations for zero and second order reactions using our integrated rate laws. 15.39 is a perfect example on how one such problem would look when being asked to do so.
by Danah Albaaj 1I
Sun Mar 04, 2018 5:19 pm
Forum: General Rate Laws
Topic: higher order rate laws
Replies: 1
Views: 83

Re: higher order rate laws

No, because as he has mentioned many times. We won't really be be involving ourselves with reactions that are more than second order due to their complexity.
by Danah Albaaj 1I
Thu Feb 22, 2018 2:34 pm
Forum: General Rate Laws
Topic: Rate Law
Replies: 2
Views: 127

Re: Rate Law

No, the answer would just be -1 because you still have to follow the formula and dividing the fractions will cancel out the value of a and leave you with -1.
by Danah Albaaj 1I
Sun Feb 18, 2018 5:51 pm
Forum: Balancing Redox Reactions
Topic: Addition of H3O+ or OH-
Replies: 4
Views: 205

Re: Addition of H3O+ or OH-

You add H+ to reactions in acidic solutions and OH- to reactions in basic solutions. For H+ you add the ion to the oxidizing agent, and for the OH- ion you add it to the reducing agent. From there you make sure they are on opposite sides of the half-reactions so that they will cancel out when adding...
by Danah Albaaj 1I
Sun Feb 18, 2018 5:40 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.9
Replies: 2
Views: 150

Re: 14.9

When solving for ∆G˚ you should be getting your answers in J/mol because the Coulombs in Faraday's constant and voltage will cancel out. Voltage is J/Coulomb while Faraday's constant is in Coulomb/mol, multiplying them together will leave you with the J/mol.
by Danah Albaaj 1I
Sat Feb 17, 2018 8:35 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.17
Replies: 1
Views: 91

Re: 14.17

I was also quite confused by this question. In the solutions manual, they used the values of permanganate and the iron for finding half-reactions in appendix 2B but I wasn't sure on why.
by Danah Albaaj 1I
Fri Feb 16, 2018 1:53 pm
Forum: Balancing Redox Reactions
Topic: 14.5 (a)
Replies: 1
Views: 97

Re: 14.5 (a)

It's really confusing to be asked which is the oxidizing agent and which is the reducing agent. It's the opposite of the reaction the molecule would be in, so O3 is in the reduction reaction which means it is the oxidizing agent.
by Danah Albaaj 1I
Sat Feb 10, 2018 3:21 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: *Confusion Regarding Cv and Cp* [ENDORSED]
Replies: 1
Views: 100

*Confusion Regarding Cv and Cp* [ENDORSED]

After doing multiple problems with entropy calculations with other classmates, UAs and TAs, as well as checking in the textbook and on here I am still confused on when to use Cv or Cp for ∆S= -nClnT2/T1. The problems all involved a diatomic gas at a changing volume and temperature, which meant I was...
by Danah Albaaj 1I
Fri Feb 09, 2018 5:32 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Homework problem 9.47
Replies: 2
Views: 131

Re: Homework problem 9.47

In Chapter 8, we are given the equation ∆U=3/2nR∆T to relate the change in internal energy to the change in temperature. If a system is isothermal, this means that ∆U=0 for this system. Using the first law of thermodynamics, we can determine the q=-w, rather than 0 .
by Danah Albaaj 1I
Fri Feb 09, 2018 1:46 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.99
Replies: 2
Views: 161

Re: 11.99

The bond dissociation energies are from a table in Chapter 3. The F-F bond is lower in energy than the other bonds because of its short bond length which in turn causes the electron pairs between the two F atoms to have stronger electron repulsion. This repulsion causes the dissociation energy of th...
by Danah Albaaj 1I
Sun Feb 04, 2018 2:56 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Using Q
Replies: 2
Views: 118

Re: Using Q

Using Q is for when the reaction is not at equilibrium. So then you would use both the result from when the reaction at equilibrium found from ∆G˚= -RTlnK and the value of RTlnQ. Professor Lavelle went over the equation at the end of lecture on Friday before the Van't Hoff equation if you would like...
by Danah Albaaj 1I
Sat Feb 03, 2018 4:48 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Test Number 1
Replies: 9
Views: 339

Re: Test Number 1

The volume of the balloon decreased, which means there was expansion work done. The definition of expansion work is from the change in the volume of the system, which is how we get the equation w = -P∆V
by Danah Albaaj 1I
Sat Feb 03, 2018 2:02 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Why does an exothermic process lead to an increase in entropy?
Replies: 3
Views: 120

Re: Why does an exothermic process lead to an increase in entropy?

Exothermic processes lead to an increase in entropy because the heat is being released into the surroundings which causes the overall entropy to increase. In this situation, the change in entropy of the surroundings will be greater than that of the system (exothermic process), which is why it is imp...
by Danah Albaaj 1I
Sat Jan 27, 2018 5:51 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: temperature dependence of entropy
Replies: 2
Views: 120

Re: temperature dependence of entropy

The first equation is at a constant temperature, while the second equation is with changing temperatures. Because of this difference, you should not expect to see the same trend in the entropy. In the second equation, the value from dividing the final temperature by the initial temperature will alwa...
by Danah Albaaj 1I
Sat Jan 27, 2018 3:27 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Utotal of Ideal Gas
Replies: 3
Views: 151

Re: Utotal of Ideal Gas

It has to do with the kinetic energy of the ideal gas. I recommend reading section 8.7 where it goes into great detail on how the numbers come into play through the use of Boltzmann's constant and the Ideal Gas Law alongside the equipartition theorem. Professor Lavelle also briefly went over it whil...
by Danah Albaaj 1I
Sat Jan 27, 2018 3:19 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Units for Entropy
Replies: 4
Views: 143

Re: Units for Entropy

I believe it depends on whether the question is asking you for the entropy per mole of the substance or not.
by Danah Albaaj 1I
Mon Jan 22, 2018 8:25 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Recognizing standard states
Replies: 2
Views: 139

Re: Recognizing standard states

I'm sure the standard states of molecules not seen as often as those similar to H2 and O2 will be given to us. Otherwise, it wouldn't hurt to be able to recognize the common elements' standard states.
by Danah Albaaj 1I
Sat Jan 20, 2018 2:29 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.57
Replies: 3
Views: 170

Re: 8.57

The values of each standard enthalpy of combustion they provided can just be plugged in to find the reaction enthalpy. So your equation to find the enthalpy will look like this deltaH = [1 mol(-1560 kJ/mol)] - [1 mol(-1300 kJ/mol) + 2 mol(-286 kJ/mol)] The final answer will then be -312 kJ. If you'r...
by Danah Albaaj 1I
Fri Jan 19, 2018 12:22 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW 8.105
Replies: 1
Views: 96

HW 8.105

Can someone help me with the final steps of this problem? I found the heat for water using q=mCdeltaT, but I'm not sure what I'm supposed to do with the given information regarding the photon's wavelength. I know I have to use Avogadro's constant, but each combination I try is not the answer of 2.49...
by Danah Albaaj 1I
Thu Jan 18, 2018 10:48 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar Kinetic Energy
Replies: 2
Views: 150

Re: Molar Kinetic Energy

Also a follow-up, can someone explain why the answer to part c is 12.5 kJ/mol instead of 12.5 J/mol?
Thank you!
by Danah Albaaj 1I
Thu Jan 18, 2018 10:20 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar Kinetic Energy
Replies: 2
Views: 150

Molar Kinetic Energy

In homework question 8.103 they ask for the molar kinetic energy in joules/mole of Krypton gas at two temperatures with a deltaT of 1 degree celsius and using the answers I'm supposed to find the specific heat capacity. My TA covered this concept a little bit in discussion today, but I was wondering...
by Danah Albaaj 1I
Sun Jan 14, 2018 2:47 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Systems
Replies: 3
Views: 203

Re: Systems

A closed system has a fixed amount of matter within it, but it can exchange energy with its surroundings. The coolant in a refrigerator coil is an example of a closed system because the type of matter doesn't change (coolant) and there is an energy exchange (temperature of refrigerator). Isolated sy...
by Danah Albaaj 1I
Sun Jan 14, 2018 2:39 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs. Isolated
Replies: 4
Views: 197

Re: Closed vs. Isolated

A closed system has a fixed amount of matter within it, but it can exchange energy with its surroundings. Isolated systems can exchange neither energy or matter with its surroundings, essentially having no contact with its surroundings.
by Danah Albaaj 1I
Sun Jan 14, 2018 2:36 pm
Forum: Calculating Work of Expansion
Topic: Homework Problem 8.3 Using Proper Units
Replies: 1
Views: 130

Re: Homework Problem 8.3 Using Proper Units

The problem provides you with the volume in centimeters cubed and the pressure in atm. In this case it is best if you convert the volume to liters in order to perform the conversions for joules. If the pressure had already been in pascals, then having the volume be in liters would have been unnecess...
by Danah Albaaj 1I
Sat Dec 09, 2017 8:34 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Question 12.45
Replies: 3
Views: 334

Re: Question 12.45

For this question, you use the given pKb to calculate the pKa by subtracting the pKb from 14. From there you are able to calculate the molecule's Ka using the equation: Ka=10^-pKa The resulting value should then help you determine the strength of each acid and rank them accordingly. The whole proces...
by Danah Albaaj 1I
Sat Dec 09, 2017 8:25 pm
Forum: Trends in The Periodic Table
Topic: Exceptions to the trends of Periodic Tables
Replies: 1
Views: 144

Re: Exceptions to the trends of Periodic Tables

I feel as if it would be wise to know which elements are exceptions the trends in the periodic table, especially if they are within the first 5 rows and could apply to any of the main topics like oxygen does. I would recommend checking Dr. Lavelle's lecture outlines and see if in any of them mention...
by Danah Albaaj 1I
Sun Dec 03, 2017 10:20 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Ph, Poh, and kw
Replies: 2
Views: 217

Re: Ph, Poh, and kw

We use Kw because it is has a calculated experimental constant for autoprotolysis at 25* C, which allows us to determine how the formation of hydronium and hydroxide within an equilibrium can be used to determine the pH and pOH based on their concentrations. We use Kw to find the pH and pOH because ...
by Danah Albaaj 1I
Sun Dec 03, 2017 10:12 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Homework Help :12.43 pg 513
Replies: 1
Views: 122

Re: Homework Help :12.43 pg 513

You would want to consider how trichlorophenol has atoms with a higher electronegativity on it, which correlates with its strength as an acid. This is because the bonds of atoms with higher electronegativity typically are weaker therefore increasing the transfer of H+
by Danah Albaaj 1I
Sun Nov 26, 2017 10:24 pm
Forum: Hybridization
Topic: 4.41
Replies: 4
Views: 401

Re: 4.41

The two carbons are bonded together. Then you place the 2 hydrogens on of one of the carbons. This is a bent shape. For the other carbon you have a hydrogen by itself and the oxygen bonded to both the nitrogen and carbon. The C-C-N bond will be one diagonal line, and make the shape of that part of t...
by Danah Albaaj 1I
Fri Nov 24, 2017 1:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 11.41
Replies: 1
Views: 249

Homework 11.41

I'm not entirely sure how to approach this problem. It states a 25.0-g sample of ammonium carbamate, NH4(NH2CO2), was placed in an evacuated 0.250-L flask and kept at 25 C. At equilibrium, 17.4 mg of CO2 was present. What is the value of Kc for the decomposition of ammonium carbamate into ammonia an...
by Danah Albaaj 1I
Sat Nov 18, 2017 5:22 pm
Forum: Hybridization
Topic: Energy of Hybrid Orbitals
Replies: 4
Views: 320

Re: Energy of Hybrid Orbitals

I wouldn't say that the energy of a hybridized orbital is the average of its contributing orbitals. Instead, I like to think about how much each orbital contributed to the hybridized orbital's energy. For example, a sp^3 orbital has 25% s-character and 75% p-character. It would make sense that the h...
by Danah Albaaj 1I
Sat Nov 18, 2017 2:49 pm
Forum: Hybridization
Topic: 4.91 Benzyne
Replies: 2
Views: 191

4.91 Benzyne

This problem asks me to draw a Lewis structure of benzyne (C6H4) including the hybridization of each carbon atom, then use my knowledge of bonding to explain why benzyne might be a reactive molecule. I know that the triple bond within the molecule would play a significant role, I'm just not exactly ...
by Danah Albaaj 1I
Sun Nov 12, 2017 5:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Tetrahedral vs Trigonal Pyramid
Replies: 2
Views: 224

Re: Tetrahedral vs Trigonal Pyramid

Another way to think of it is trigonal pyramidal is a tetrahedral shape that has lost a bond and replaced it with a lone pair. You can see it when you look at the VSEPR notation for both shapes, tetrahedral is AX4 while trigonal pyramidal is AX3E.
by Danah Albaaj 1I
Sun Nov 12, 2017 5:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Thiosulfate ion shape
Replies: 2
Views: 272

Re: Thiosulfate ion shape

I agree with what was stated above, and in regards to where you should put a lone pair on the central atom. You want to put it the farthest you possibly can from any bonds or other lone pairs while keeping some symmetry with the rest of the bonds and their angles.
by Danah Albaaj 1I
Sun Nov 05, 2017 5:15 pm
Forum: Lewis Structures
Topic: HW: 3.33 part B
Replies: 1
Views: 84

Re: HW: 3.33 part B

The formal charge of a double bonded oxygen atom is 0, while the formal charge of a double bonded chlorine atom is +1. The formal charge of 0 is more stable and has a lower energy, which is what we want.
by Danah Albaaj 1I
Sun Nov 05, 2017 5:11 pm
Forum: Lewis Structures
Topic: HW Question 3.41
Replies: 2
Views: 127

Re: HW Question 3.41

Hi! So for the Lewis structure, you have to connect the central carbon to its own two hydrogen as well as the NH2 and COOH. So basically just put one carbon in the center, then attach a nitrogen on one side, and another carbon on the other. From there bond the remaining parts of each compound to eac...
by Danah Albaaj 1I
Sun Oct 29, 2017 2:55 pm
Forum: Electronegativity
Topic: Exceptions [ENDORSED]
Replies: 2
Views: 168

Re: Exceptions [ENDORSED]

The textbook tells us that one of the elements is oxygen, and I believe it goes more in depth about how we can find these exceptions.
by Danah Albaaj 1I
Sun Oct 29, 2017 2:52 pm
Forum: Resonance Structures
Topic: Efficiency [ENDORSED]
Replies: 2
Views: 203

Re: Efficiency [ENDORSED]

I believe the most efficient way would be to calculate the formal charge of the atom. As it says in our notes, the most stable bond is when the formal charge is equal to 0. Finding the bonds necessary for the formal charge to equal 0 should only take a few steps, especially if we are able to anticip...
by Danah Albaaj 1I
Sun Oct 29, 2017 2:48 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.81
Replies: 1
Views: 126

Re: 2.81

Oxygen has a lower ionization energy than nitrogen and fluorine because of the repulsion between its electrons. Nitrogen only has 3 electrons in the 2p-orbital which means each electron is unpaired. Fluorine has 5 electrons in the 2p-orbital meaning only one electron is unpaired, which makes it more...
by Danah Albaaj 1I
Wed Oct 18, 2017 4:51 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Identifying radiation based on a wavelength
Replies: 3
Views: 183

Re: Identifying radiation based on a wavelength

On the test I took yesterday, the values were given to me. However, I agree with what others have been saying and recommend knowing their differences because wavelength relates to the key concepts of this chapter.
by Danah Albaaj 1I
Wed Oct 18, 2017 4:48 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework
Replies: 3
Views: 176

Re: Homework

The homework due any week, is 4 questions relating to what has been discussed in lecture. This week you only have to turn in 4 more problems from Chapter 1, unless you decided to read ahead and do some of the Chapter 2 problems.
by Danah Albaaj 1I
Sun Oct 15, 2017 4:02 pm
Forum: DeBroglie Equation
Topic: 1.37 [ENDORSED]
Replies: 5
Views: 335

Re: 1.37 [ENDORSED]

You can also find the masses of both particles on the class website! It's in a worksheet named constants and equations, just in case you wanna have a separate page to look at so you're not constantly flipping the pages of your book :)
by Danah Albaaj 1I
Thu Oct 12, 2017 8:52 pm
Forum: Einstein Equation
Topic: HW Question 1.25
Replies: 2
Views: 644

HW Question 1.25

Question #25 states: Sodium vapor lamps, used for public lighting, emit yellow light of wavelength 589 nm. How much energy is emitted by (a) an excited sodium atom when it generates a photon; (b) 5.00 mg of sodium atoms emitting light at this wavelength; (c) 1.00 mol of sodium atoms emitting light a...

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