Search found 37 matches

by Johnchou1A
Sun Mar 13, 2016 1:28 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Intermediates
Replies: 1
Views: 362

Re: Intermediates

I believe that since they are initially formed and then used in the overall reaction, they do not provide an accurate portrayal of the actual reaction itself. As in, the rate law (including intermediates) doesn't show the actual reactants used. That is why we must solve for the intermediate during t...
by Johnchou1A
Thu Mar 03, 2016 5:46 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Assigning priority and naming the compound error? pg17
Replies: 3
Views: 545

Re: Assigning priority and naming the compound error? pg17

I think it has to do with the highest priority group(highest atomic number) on each individual C atom of the double bond.
by Johnchou1A
Mon Feb 29, 2016 12:36 am
Forum: *Alkanes
Topic: Quiz 3 Preparation
Replies: 34
Views: 11558

Re: Quiz 3 Preparation

Shelby Yee 1J wrote:@Johnchou1A the Iodine gets ultimate priority since it has a higher atomic number, therefore, iodine should be 1 and bromine should be 3


Do we look at the atomic number only when we deal with halogens as substituents then?
by Johnchou1A
Sun Feb 28, 2016 11:26 pm
Forum: *Alkanes
Topic: Including Subsituents in Naming?
Replies: 2
Views: 367

Re: Including Subsituents in Naming?

Think of it as a parent nonane chain with 2 substituents: methyl and 2-methylpropyl. Methyl precedes methylpropyl in alphabetical order so methyl receives the lowest possible number When you mean alphabetical order, are you referring to the fact that the "m" in methyl precedes the "p...
by Johnchou1A
Sun Feb 28, 2016 10:33 pm
Forum: *Alkanes
Topic: Quiz 3 Preparation
Replies: 34
Views: 11558

Re: Quiz 3 Preparation

for question number 5 on the first quiz, why is Iodine chosen as the starting point rather than Bromine? does it matter? I had the exact same question. I always thought that since bromine comes first alphabetically, it must be assigned the lower number. Therefore you Bromine would be numbered 1? Is...
by Johnchou1A
Sun Feb 28, 2016 6:46 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Assigning priority and naming the compound error? pg17
Replies: 3
Views: 545

Assigning priority and naming the compound error? pg17

On page 17 in the Organic textbook, would the 3rd name down on the right side of the page be wrong? In other words, is (Z)-1,1-bromochloropropene the right name of that compound? because Br and Cl have highest priority but they are on opposite sides of the double bond. Wouldn't that make it a trans ...
by Johnchou1A
Sat Feb 27, 2016 5:07 pm
Forum: *Alkanes
Topic: Numbering the Carbon
Replies: 4
Views: 373

Re: Numbering the Carbon

What I do is, I right them out both ways and then I add the number of Carbons and chose the one with the least. For example, 1+3 is 4 while 5+3 is 8. So the first one was the correct one because 4 is smaller than 8. Hopefully that helps a little. I thought that we aren't supposed to use the "s...
by Johnchou1A
Thu Feb 18, 2016 7:25 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium Approach
Replies: 3
Views: 607

Re: Pre-Equilibrium Approach

I had the same question. This video helped to better clarify the confusion when plugging back in to try to verify the overall rate law. https://www.youtube.com/watch?v=7QT1ehpxKUU"onclick="window.open(this.href);return false; Both in his and Lavelle's example, I assume we view the k1k2/k1' and other...
by Johnchou1A
Tue Feb 09, 2016 10:44 pm
Forum: Phase Changes & Related Calculations
Topic: Winter 2013 Midterm Q2A.
Replies: 4
Views: 695

Re: Winter 2013 Midterm Q2A.

I had the same question as Anika. When you look at a hearing curve, like the one in our course reader, you first need to raise the temperature of the ICE in order to get it to it's melting point of 0 degrees Celsius, using q=nCdeltaT. C would then have to refer to the heat capacity of water as ice. ...
by Johnchou1A
Sun Feb 07, 2016 2:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Choosing cathodes and anodes when given standard E values
Replies: 1
Views: 3054

Choosing cathodes and anodes when given standard E values

When given two half reactions and their reduction values, is it safe to assume the half reaction with the more positive E value will be the cathode/reduced? Because when you compute the E value of the cell, the value will then be positive due to E(cell) = E(cathode) - E(anode)? Also, is this because...
by Johnchou1A
Thu Feb 04, 2016 12:02 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Discerning what is being reduced and oxidized? HW 14.15a
Replies: 2
Views: 394

Discerning what is being reduced and oxidized? HW 14.15a

AgBr(s) <-> Ag+ + Br- In this case, how can we tell which species is being reduced and which is being oxidized? Some equations make seeing which species is oxidized/reduced easier because you can clearly see which charges decrease/increase, but how would we write the oxidation and reduction half rea...
by Johnchou1A
Wed Feb 03, 2016 11:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: homework question 14.9
Replies: 3
Views: 474

Re: homework question 14.9

"n" refers to the number of moles of electrons in each half-reaction that you have written. Assuming that the number of electrons are balanced, which they should be, both half reactions will have the same number of electrons, which you then use as your "n"
by Johnchou1A
Sat Jan 30, 2016 2:55 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8195
Views: 1429298

Re: Chemistry Jokes

What is the charge of cations?

pawsitive
by Johnchou1A
Fri Jan 22, 2016 3:12 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Expansion work
Replies: 4
Views: 570

Re: Expansion work

When it states "no expansion work," deltaV is 0. When deltaV is 0, it means that there is no work done, and that the only change in internal energy will be due to heat. Thus, deltaU = q
by Johnchou1A
Tue Jan 19, 2016 4:17 pm
Forum: Phase Changes & Related Calculations
Topic: Premed info session
Replies: 1
Views: 376

Premed info session

will the information session for today (Tuesday 1/19) be broadcasted?
by Johnchou1A
Sat Jan 16, 2016 8:41 pm
Forum: Phase Changes & Related Calculations
Topic: HW 8.41
Replies: 1
Views: 357

HW 8.41

When calculating the heat to raise the ice cube to the final temperature, the solutions manual uses the specific heat capacity of water as a liquid (not as a solid). Is this because it is assumed that at this point in the reaction, the ice has already been melted (through heat of fusion) and we are ...
by Johnchou1A
Sat Jan 16, 2016 8:11 pm
Forum: Phase Changes & Related Calculations
Topic: enthalpy units
Replies: 1
Views: 545

enthalpy units

Is it safe to assume that H can be measured in joules AND joules/mole? It seems the units can interchange during different calculations, such as in the answers of 8.37 and 8.39 on the homework
by Johnchou1A
Sat Jan 16, 2016 1:46 pm
Forum: Phase Changes & Related Calculations
Topic: Path Functions
Replies: 1
Views: 338

Re: Path Functions

Work and heat are examples of path functions because in order to measure them, one must measure the actual "paths" taken. They depend on the actual sequence of steps by which the system took to go from initial state to final state. I like this website's explanation: "There is no such ...
by Johnchou1A
Thu Jan 07, 2016 10:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Using Bond Enthalpies in Calculations
Replies: 3
Views: 507

Re: Using Bond Enthalpies in Calculations

When doing these calculations, I find it easier to first draw the Lewis structures of each compound involved in the reaction. Then, imagine breaking the bonds of the reactants and then reimagine the final Lewis structure of the product, keeping in mind which bonds are being formed. For the second ex...
by Johnchou1A
Sat Dec 05, 2015 8:25 pm
Forum: Ionic & Covalent Bonds
Topic: covalent character
Replies: 5
Views: 4336

Re: covalent character

This problem is in the 2013 Final (question 3C) and it says the answer AgF, but why is AgF less covalent than BeCl2? I had the same question. Since Be and Cl are the farthest from each other on the periodic table, wouldn't they technically be the most ionic compound and therefore the least covalent?
by Johnchou1A
Mon Nov 30, 2015 11:26 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Calculating K when H2O is not in the equation.
Replies: 1
Views: 401

Calculating K when H2O is not in the equation.

For question 12.117, you are asked to calculate the K value of the eqn,

HNO2(aq) + NH3(aq) <-> NO2-(aq) + NH4+(aq).

I know you have to do something with each reactants original Ka & Kb expressions, but I do not see the connection to obtain the overall K value. Can anybody clarify?
by Johnchou1A
Fri Nov 27, 2015 3:25 pm
Forum: Lewis Acids & Bases
Topic: Strong Acid
Replies: 3
Views: 578

Re: Strong Acid

For the most part, strong acids usually involve a hydrogen bonded to one of the halogens, such as HCl, HBr, and HI. In this case, the strongest acid would be HI, because due to its longer and therefore weaker bond, it is more easily disassociating, and thus can donate more protons in the form of H+ ...
by Johnchou1A
Tue Nov 17, 2015 4:41 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure
Replies: 2
Views: 709

Re: Pressure

Also keep in mind that when looking at these chemical equations, you must only focus on MOLES OF GAS. Foe example, if your equation was: H2O(g) + C(s) <-> H2(g) + CO(g) you would disregard the C on the reactant side. There would then be 1 mol of gas on the left (H2O), and 2 mol of gas on the right (...
by Johnchou1A
Fri Nov 13, 2015 3:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Icebox: when to add to either the reactants or products
Replies: 1
Views: 414

Re: Icebox: when to add to either the reactants or products

After writing out the equilibrium equation, "x" is subtracted from the side containing the reactants and added to the side containing the products, depending on whatever the equation is. In addition, coefficients on the "x"s must match their corresponding stoichiometric coefficie...
by Johnchou1A
Thu Nov 12, 2015 4:35 pm
Forum: Naming
Topic: oxalato
Replies: 1
Views: 395

Re: oxalato

I believe abbreviating it is just fine. My TA said it should be good either way you do it.
by Johnchou1A
Sun Nov 08, 2015 8:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium
Replies: 2
Views: 286

Re: Chemical Equilibrium

Going off of what Ashlee said, Q is the value of the ratio of concentrations of the products to reactants when the chemical equation is NOT at equilibrium. K is the value of the ratio of concentrations of the products to reactants when the chemical equation IS at equilibrium. Thus, when you calculat...
by Johnchou1A
Sun Nov 01, 2015 11:17 pm
Forum: Sigma & Pi Bonds
Topic: Identifying the composition of bonds/hybridizations notation
Replies: 2
Views: 550

Identifying the composition of bonds/hybridizations notation

In the practice midterms, there are questions that ask for the composition of bonds/lone pairs in the form of
σ(H1s,C2sp^2), for example.

How do we know what to write when a question asks for these on a Lewis structure?
by Johnchou1A
Mon Oct 26, 2015 9:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Oxygen
Replies: 1
Views: 344

Re: Oxygen

More often than not, oxygen will form a double bond because in doing so, its formal charge becomes 0 (most stable).
by Johnchou1A
Mon Oct 26, 2015 9:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Phosphate polarity
Replies: 1
Views: 765

Re: Phosphate polarity

Because phosphate is an ion and has an overall charge, polarity does not play a role.
by Johnchou1A
Mon Oct 26, 2015 9:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Octet Rule Exception
Replies: 3
Views: 693

Re: Octet Rule Exception

Usually I think of drawing Lewis structures as trial and error. In your case, after the 4 bonds have been formed, the extra two valence electrons have no other place to be located, so place them as a lone pair around the central atom. Because Br can form an expanded octet (it is below period 2), thi...
by Johnchou1A
Thu Oct 15, 2015 1:05 pm
Forum: Empirical & Molecular Formulas
Topic: Self test Quiz 1
Replies: 1
Views: 419

Re: Self test Quiz 1

Coefficients simply tell the number of moles of a particular compound. In this case, C6H10O is a different compound from C12H20O. By adding a coefficient of 2 to C6H10O (2C6H10O), your final answer is not C12H20O, but rather, 2 moles of C6H10O. Hope that made sense.
by Johnchou1A
Thu Oct 15, 2015 1:01 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg v. Schrodinger
Replies: 1
Views: 366

Re: Heisenberg v. Schrodinger

I believe Dr. Lavelle told us that we will not be using the Schrodinger wave equation in the class. As seen in the homework problems in Chapter 2, none of them specifically ask to calculate the wave function. All of the problems deal with uncertainty through the use of the Heisenberg equation.
by Johnchou1A
Mon Oct 12, 2015 9:42 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Do you have to multiply by 2 for when given a +/-?
Replies: 2
Views: 419

Re: Do you have to multiply by 2 for when given a +/-?

I wouldn't think about it as simply multiplying by "2," but you are looking for the "change in" (Δ) a value. In your case, Δv = 10 m/s because the change in velocity is +/- 5 m/s, so your change in velocity would have to be from -5 to 5. That is why Δv would be 10 m/s. Hope that ...
by Johnchou1A
Wed Oct 07, 2015 1:20 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Uncertainty Problem in A-V Module
Replies: 2
Views: 1590

Re: Heisenberg Uncertainty Problem in A-V Module

The uncertainty principle states that ΔxΔp≥h/4Π. In this case, the uncertainty of the position(Δx) is given by (percent accuracy) x (the diameter of the atom), so Δx = (.01)(.05 * 10^-9 m). Once that is found, you have the mass of the electron and the uncertainty in its position; now, just plug and ...
by Johnchou1A
Tue Sep 29, 2015 12:09 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Formula Unit
Replies: 4
Views: 3367

Formula Unit

When calculating the number of formula units in a compound, would the question simply be referring to the number of molecules? For example, would the number of formula units in 1 mol of H2O just be

(1 mol H2O) x (6.02x10^23)?
by Johnchou1A
Sun Sep 27, 2015 4:51 pm
Forum: Empirical & Molecular Formulas
Topic: Writing formulas
Replies: 2
Views: 556

Re: Writing formulas

I believe that the suffix depends on the last letters of the compound. Polyatomic ions follow the general rule of "ate = ic ; ite = ous." In your case, "nitric" falls under the "ate" category, so the corresponding polyatomic ion would be nitrate (NO3-). And because you ...

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