Search found 34 matches

by Alex Dib 4H
Sun Mar 19, 2017 12:31 pm
Forum: *Alkenes
Topic: Are Alkenes considered functional groups?
Replies: 1
Views: 568

Are Alkenes considered functional groups?

I came across a question, can't recall which, that asked us to identify all functional groups in a given molecule. The answer also included double bond alkenes in the list of functional groups. For our purposes, should we consider alkenes and alkynes as functional groups if asked to identify functio...
by Alex Dib 4H
Fri Mar 17, 2017 7:57 pm
Forum: *Alkanes
Topic: How to name the Alcohol
Replies: 4
Views: 730

Re: How to name the Alcohol

Hi, I think it is complete preference. I prefer to use propan-2-ol because it is more clear for me. Also, when there is a double bond involved as well as a functional group, prop-x-en-2-ol (where x is whichever carbon the double bond is on) is, for me, much easier to deconstruct than x,2-propenol (n...
by Alex Dib 4H
Sat Mar 11, 2017 1:26 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7582
Views: 1017439

Re: Post All Chemistry Jokes Here

Did you know that you can cool yourself to -273.15˚C and still be 0k?
by Alex Dib 4H
Sun Mar 05, 2017 2:46 pm
Forum: *Cycloalkenes
Topic: 2 Substituents on a Ring
Replies: 2
Views: 549

Re: 2 Substituents on a Ring

An example of this would be with, lets say, a cyclohexane with a methyl on the left lower carbon and an ethyl on the right upper carbon. You can either number this as 4-ethyl-1-methylcyclohexane, giving a 1 to the methyl and giving a 4 to the ethyl , or you can alternatively name it 1-ethyl-4-methyl...
by Alex Dib 4H
Sat Mar 04, 2017 11:07 pm
Forum: *Nucleophilic Substitution
Topic: Naming with Substituents [ENDORSED]
Replies: 1
Views: 550

Re: Naming with Substituents [ENDORSED]

If I understand your question correctly, I think the numbering starts on the substituent that will yield the smallest combination of all substituent's numbers when added. For example, if you have two different possibilities for numbering a molecule's substituents which are (1, 3, and 4) or (1,2, and...
by Alex Dib 4H
Fri Feb 24, 2017 7:01 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Electrophiles
Replies: 3
Views: 360

Re: Electrophiles

I think it is because they are attracted to electrons to complete their shells, due to 7 valence electrons. Someone please correct me if I'm wrong.
by Alex Dib 4H
Thu Feb 23, 2017 12:34 am
Forum: General Rate Laws
Topic: Quiz 2 Preparation
Replies: 2
Views: 287

Re: Quiz 2 Preparation

We know its a second order reaction because of the exponent given in the rate law; rate = k[A] 2 Using the integrated rate law for second order reactions, we can rearrange the equation and solve for time. Knowing that k is the same constant at both initial concentrations, we can ignore it. This give...
by Alex Dib 4H
Mon Feb 20, 2017 3:39 am
Forum: First Order Reactions
Topic: 15.21
Replies: 1
Views: 434

Re: 15.21

In this problem, we use first order integrated rate law ln[A] t =-kt+ln[A] 0 and plug in the rate constant and time, converted to minutes. We can't actually determine the concentrations directly, but we can solve for [A] t by rearranging and putting into exponent form. With algebra, you get [A] t =....
by Alex Dib 4H
Sun Feb 12, 2017 2:01 am
Forum: Calculating Work of Expansion
Topic: Problem 8.93
Replies: 1
Views: 312

Re: Problem 8.93

For this problem, we rearrange w=-P(delta)V with PV=nRT and get w =-(delta)nRT. Delta n is equal to the amount of stoichiometric moles of gas for products minus the moles of gas for the reactants, and only gas. I think the reason this is the case is because we're not given enough information to dete...
by Alex Dib 4H
Mon Feb 06, 2017 1:26 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Spontaneous Reduction
Replies: 1
Views: 257

Re: Spontaneous Reduction

It is summed up very well in the course reader on page 49, but essentially we know that deltaGo=-nFEo, and from the previous chapter, when deltaG is negative, the reaction is spontaneous, which means that Eo is always positive when deltaG is negative.
by Alex Dib 4H
Sun Jan 29, 2017 12:56 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW Ch.8 question 8.25
Replies: 4
Views: 462

Re: HW Ch.8 question 8.25

Hey, I don't have the problem in front of me, but from what I understand, you're correct. You can see this mathematically when you set q(system)+q(calorimeter)=0, which is rearranged as q(calorimeter)=-q(system). What we're given, we are only finding information of the calorimeter. We know that the ...
by Alex Dib 4H
Mon Jan 23, 2017 3:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 #101
Replies: 2
Views: 354

Re: Chapter 8 #101

Hi Step one, we gotta find the initial volume using PV=nRT, where n=.0300+.0300=.0600. This gives an initial volume of 1.47 L Step two, we need to determine the limiting reactant which can be done by inspection. We're given an equal amount of moles of both SO2 and O2, but we need twice the amount of...
by Alex Dib 4H
Sun Jan 22, 2017 10:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Change and Internal Energy Change for a Chemical Reaction
Replies: 1
Views: 258

Re: Enthalpy Change and Internal Energy Change for a Chemical Reaction

Hi, when calculating delta n (change in moles) we are only concerned with gas phase molecules in the chem equation because those are the only ones that will affect work done. In this problem, were given 6mol H20 and 6 mol CO2 in gas phase on products, totaling 12 moles, and 6 mol O2 on gas phase on ...
by Alex Dib 4H
Tue Jan 17, 2017 12:01 am
Forum: Calculating Work of Expansion
Topic: Hmwk Problem 8.67 [ENDORSED]
Replies: 2
Views: 346

Re: Hmwk Problem 8.67 [ENDORSED]

The way the reaction is balanced gives one mole of H20(l), which is helpful because when we find the enthalpy change for the reaction, we are also finding the enthalpy of formation of H20(l). There are a few ways to do this, but for this question we are asked to use bond enthalpies to calculate the ...
by Alex Dib 4H
Sun Dec 04, 2016 2:27 am
Forum: Calculating the pH of Salt Solutions
Topic: Salts
Replies: 1
Views: 380

Re: Salts

Hey, Im pretty sure that you'd only be using group 1 and 2 metals because they do not affect the pH of solution. I don't think it particularly matters which one, as long as as the formal charge of the conjugate base and metal salt match.
by Alex Dib 4H
Thu Nov 24, 2016 2:24 am
Forum: Polyprotic Acids & Bases
Topic: Polyprotic Acids and strength
Replies: 2
Views: 603

Re: Polyprotic Acids and strength

I think they're for the most part weak. But H2SO4 is a strong acid and gives off more than one proton so I don't think we should assume ALL are weak, but probably most.
by Alex Dib 4H
Tue Nov 15, 2016 11:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: concentration problem
Replies: 1
Views: 211

Re: concentration problem

Hey, I'm pretty sure you're correct about finding the concentration for that problem, just divide all of the given moles by their volume. And since our reactant is a solid, we just ignore it, like you said. To find moles when given grams, you would divide the given grams by the molar mass of the com...
by Alex Dib 4H
Mon Nov 07, 2016 10:45 pm
Forum: Naming
Topic: Name this compound
Replies: 1
Views: 559

Re: Name this compound

[CoBr(NH 3 ) 5 ]SO 4 Hey, so I see 5 neutral ammonias (NH 3 ), one bromine anion (Br - ), and cobalt (Co) as the transition metal all in the coordination sphere (inside brackets). Outside I see a sulfate (SO 4 2- ). Because that sulfate has a 2- charge, the coordination compound has to have a 2+ cha...
by Alex Dib 4H
Tue Nov 01, 2016 1:04 am
Forum: Octet Exceptions
Topic: Lewis Acids and Bases
Replies: 3
Views: 563

Re: Lewis Acids and Bases

Hi, I think this only applies to elements in group 13 because they have 3 valence electrons and don't complete a full octet, but will have 6 instead. An anion or terminal atom of a molecule can donate an electron pair to form a bond with that group 13 element, giving it an octet. The group 13 elemen...
by Alex Dib 4H
Sat Oct 29, 2016 12:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electron arrangement for ClO2-
Replies: 1
Views: 611

Re: Electron arrangement for ClO2-

I think you're correct on everything except that the electron configuration including the lone pairs is tetrahedral, not trigonal pyramidal, because their are four regions of electron density. Since two regions are lone pairs, we see the shape as bent instead of tetrahedral (just two of the branches...
by Alex Dib 4H
Thu Oct 27, 2016 3:02 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7582
Views: 1017439

Re: Post All Chemistry Jokes Here

I had my ion a great joke, but fluorine stole it :(
by Alex Dib 4H
Fri Oct 21, 2016 11:19 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Relative size of cations and anions
Replies: 2
Views: 528

Re: Relative size of cations and anions

I think its because when cations lose all of the electrons of their outer shell, that loss of the shell makes the cation much smaller. And when anions gain electrons to complete their outer shell, the extra electrons repel each other more, making the overall radius larger.
by Alex Dib 4H
Sun Oct 16, 2016 3:22 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Energy in the Atomic Spectroscopy
Replies: 2
Views: 375

Re: Energy in the Atomic Spectroscopy

Not positive of the true definition, but i think of it as equalling the energy at the n'th shell for hydrogen atoms. So the energy at the first shell (ground state) of a hydrogen atom would be -hR/1^2, and the energy at the second shell would be -hR/2^2. We are mostly interested in the difference in...
by Alex Dib 4H
Tue Oct 11, 2016 6:56 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Quantum number
Replies: 2
Views: 338

Re: Magnetic Quantum number

-1 refers to px (Boron or Oxygen)
0 refers to py, (Carbon or Flourine)
1 refers to pz, (Nitrogen or Neon)

The numbers are ambiguous, could have also said 1 refers to px, 0 refers to py, and 1 refers to pz. Just have to show consistency (I think).
by Alex Dib 4H
Tue Oct 11, 2016 6:47 pm
Forum: DeBroglie Equation
Topic: Quiz Prep 2015 #8 [ENDORSED]
Replies: 1
Views: 294

Re: Quiz Prep 2015 #8 [ENDORSED]

De Broglie's equation is used for finding the wavelength associated with objects with mass. A photon is massless and has its own equation for finding energy/wavelength/frequency.

Simply stated, if its a photon, use E=hv. If it has mass, use De Broglie's
by Alex Dib 4H
Tue Oct 11, 2016 4:52 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Question 2.29 from the textbook [ENDORSED]
Replies: 2
Views: 411

Re: Question 2.29 from the textbook [ENDORSED]

Yup, b) and d) are only 2 possibilities because the only quantum number missing is the +1/2 or -1/2 which would specifically say which element it is. a) is 6 because they tell us its in the second period and in the p-block, but don't specify which elements by telling us the other 2 quantum numbers, ...
by Alex Dib 4H
Tue Oct 11, 2016 4:38 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Pre Assessment Questions
Replies: 2
Views: 442

Re: Pre Assessment Questions

I'm also getting "none of the above" for this one and have been second guessing myself about it for a while too, lol. But instead of .1 nm x .01, I did .05 nm x .01 because they are saying 1% of the radius (I think we always double it when uncertainty is given in +/-. Here they are giving ...
by Alex Dib 4H
Fri Oct 07, 2016 11:30 pm
Forum: Properties of Light
Topic: Question 1.25 on the HW
Replies: 2
Views: 1245

Re: Question 1.25 on the HW

For part A, you just need the wavelength. Convert that to energy with E=hc/lambda. This tells us that 3.37x10^-19 J was emitted from one atom of Na. Part B is asking for 5.00 mg of Na now. We know how much per atom of Na, so using dimensional analysis, we can convert the energy for one atom Na to th...
by Alex Dib 4H
Fri Oct 07, 2016 12:18 am
Forum: Photoelectric Effect
Topic: Wavelength vs. Photons [ENDORSED]
Replies: 5
Views: 615

Re: Wavelength vs. Photons [ENDORSED]

How does the photoelectric effect exactly prove that light doesn't act as waves but as particles? I think its because when they were attempting to eject electrons with light, they knew that the light needed to carry with it enough energy to eject the electron. So when they weren't getting the elect...
by Alex Dib 4H
Wed Oct 05, 2016 2:07 am
Forum: Photoelectric Effect
Topic: Wavelength Intensity [ENDORSED]
Replies: 1
Views: 358

Re: Wavelength Intensity [ENDORSED]

I think it's because, at threshold energy, one photon ejects one electron (there's never 2+ photons needed to eject one electron or one photon ejecting 2+ electrons), and intensity of light is proportional to the number of photons in that light. So increasing the intensity of light hitting a metal s...
by Alex Dib 4H
Sun Oct 02, 2016 3:34 am
Forum: Properties of Light
Topic: Why is UV radiation more harmful than infrared?
Replies: 2
Views: 4986

Re: Why is UV radiation more harmful than infrared?

Hey Eva, It has to do with wavelength, as well as energy. As we know, the shorter the wavelength, the higher the energy, but what I THINK is going on with our bodies is that the smaller the wave, the easier that wave can penetrate and affect the cells and DNA that make up our bodies. When you look a...
by Alex Dib 4H
Sun Oct 02, 2016 3:17 am
Forum: Molarity, Solutions, Dilutions
Topic: Help on G.19.
Replies: 2
Views: 485

Re: Help on G.19.

Hi Karla, The way I chose to do this problem is in two steps. First, find the amount of moles in the given solution by using the given molarity. Then, once you have the moles, put whatever the final volume they are asking for with the moles determined before to get our concentration (moles/volume). ...
by Alex Dib 4H
Tue Sep 27, 2016 9:42 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reactant Audio-Visual Topic Question
Replies: 2
Views: 349

Re: Limiting Reactant Audio-Visual Topic Question

Hey Charles, I believe that you're correct. Due to the law of conservation of mass, the mass of product will always be equal to the mass of reactants, never more or less. This is what balancing equations is based off of. If we have excess reactant in a limiting reactant problem, the left over reacta...
by Alex Dib 4H
Tue Sep 27, 2016 9:22 pm
Forum: Molarity, Solutions, Dilutions
Topic: G #17 b
Replies: 4
Views: 957

Re: G #17 b

Hey Yuchien, I solved this problem using dimensional analysis. First, I found the amount of moles of CuSO4 in 250 mL of a 0.20 solution, which is 0.05 moles of CuSO4. Then, we have to convert that into moles CuSO4.5H20 with a conversion factor of 1 mole CuSO4 for every 1 mol of CuSO4.5H20, which als...

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