Search found 24 matches

by Alex Chen 1B
Tue Mar 14, 2017 7:33 pm
Forum: *Alcohols
Topic: Homework question
Replies: 1
Views: 595

Re: Homework question

In 18, the 2 refers to the carbon that the alcohol is attached to, which is the second carbon in the three-carbon chain. In 19, the alcohol is named in the same way with the 2-hexanol, which tells you that the alcohol is attached to the second carbon in the six-carbon chain. The fact that that's a s...
by Alex Chen 1B
Thu Mar 09, 2017 3:09 am
Forum: *Free Energy of Activation vs Activation Energy
Topic: Catalysts vs. Enzymes
Replies: 1
Views: 943

Re: Catalysts vs. Enzymes

Enzymes are just biological catalysts that catalyze biochemical reactions. So all enzymes are catalysts, but not all catalysts are enzymes.
by Alex Chen 1B
Sat Mar 04, 2017 9:31 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Chapter 15 Question 65
Replies: 1
Views: 307

Re: Chapter 15 Question 65

The rate of a reaction with a lower activation energy barrier isn't as affected by increasing temperature because once the reaction reaches a temperature that allows it to get over its energy barrier, the rate basically stays the same. The rate of a reaction with a higher activation energy barrier, ...
by Alex Chen 1B
Mon Feb 20, 2017 7:38 pm
Forum: Zero Order Reactions
Topic: 15(25) part c (where does negative sign go?)
Replies: 1
Views: 288

Re: 15(25) part c (where does negative sign go?)

The equation the solution manual uses is just a slightly different form of the ln [A]t = -kt + ln [A]not equation. When you solve for -kt, you get ln ([A]t/[A]not) and then the solution manual just divided the everything by -1 to get kt = -ln ([A]t/[A]not) = ln ([A]not/[A]t), which is just a princip...
by Alex Chen 1B
Mon Feb 13, 2017 2:19 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Gibbs free energy
Replies: 2
Views: 394

Re: Gibbs free energy

Gibbs free energy is the amount of energy available to do work, so the delta G of a redox reaction is the maximum amount of work that can be done by the reaction.
by Alex Chen 1B
Thu Feb 09, 2017 6:56 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: CH 14.57 [ENDORSED]
Replies: 1
Views: 510

CH 14.57 [ENDORSED]

Chapter 14.57 in the textbook asks: Aqueous solutions of (a) Mn2; (b) Al3; (c) Ni2; (d) Au3 with concentrations of 1.0 mol/L are electrolyzed at pH 7. For each solution, determine whether the metal ion or water will be reduced at the cathode. I thought electrolysis meant that your redox reaction is ...
by Alex Chen 1B
Thu Feb 02, 2017 9:55 pm
Forum: Administrative Questions and Class Announcements
Topic: Equipartition Theorem
Replies: 1
Views: 355

Re: Equipartition Theorem

No I don't think we have to. I don't remember that being in the course reader.
by Alex Chen 1B
Mon Jan 23, 2017 3:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 #101
Replies: 2
Views: 547

Re: Chapter 8 #101

The problem tells you that there are initially 0.0300 moles of SO2 and 0.0300 moles of O2 present in the cylinder. They give you the equation for the reaction, so all you have to do is figure out which reactant will completely react given the initial quantities. So in this case, if all of the O2 wer...
by Alex Chen 1B
Fri Jan 20, 2017 3:13 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Ch 8.85
Replies: 1
Views: 567

Re: Ch 8.85

For a), I just did stoichiometry to find the heat absorbed. For b), you have to use PV = nRT to find the moles of N2 that were oxidized, and then you can use stoichiometry to find the heat that this reaction absorbed because you know that 180.6 kJ of heat are released for every 1 mole of N2 that was...
by Alex Chen 1B
Sun Jan 15, 2017 8:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy and Energy
Replies: 1
Views: 252

Re: Enthalpy and Energy

Enthalpy is the measure of how much heat is released or absorbed at a constant pressure and heat is defined as the transfer of energy due to temperature difference. So I think enthalpy can be thought of as a measure of the transfer of energy in a chemical reaction.
by Alex Chen 1B
Fri Dec 02, 2016 10:51 am
Forum: Significant Figures
Topic: Sig Figs for pH
Replies: 3
Views: 1212

Re: Sig Figs for pH

No, I don't think so. I remember learning in AP Chem that the number of sig figs you have becomes the number of decimal places in the pH value (ex. 3 sig figs = 3.000). But the textbook solutions are given in a way that the number of sig figs you have are the sig figs in the answer (ex. 3 sig figs =...
by Alex Chen 1B
Wed Nov 23, 2016 3:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.37 Homework Help
Replies: 1
Views: 335

Re: 11.37 Homework Help

Since 2 NH3 -> N2 + 3H2 is the reverse reaction of N2 + 3H2 -> 2 NH3, you just have to take the inverse of the K of N2 + 3H2 -> 2 NH3 to get the K of 2 NH3 -> N2 + 3H2. This works because the equilibrium expression for N2 + 3H2 -> 2 NH3 is [NH3]^2/[N2][H2]^3 and the equilibrium expression for 2 NH3 ...
by Alex Chen 1B
Tue Nov 15, 2016 9:56 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Using MO Model
Replies: 1
Views: 266

Re: Using MO Model

The Z>8 and Z<8 only applies for homonuclear molecules, which are molecules that have atoms of the same element, and it's the atomic number of that element. For molecules with different atoms (heteronuclear), you always use the MO diagram for Z<8.
by Alex Chen 1B
Sat Nov 12, 2016 3:13 pm
Forum: Naming
Topic: Negative charge. Add Ate to the end
Replies: 3
Views: 529

Re: Negative charge. Add Ate to the end

Since you have 3 K+ cations, you have to balance the 3+ charge to get a neutral net charge. So the anion, which is the coordination compound in this case, has to have a charge of 3-.
by Alex Chen 1B
Sat Nov 12, 2016 12:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Aqueous Ions
Replies: 1
Views: 301

Re: Aqueous Ions

We only include the concentration of aqueous solutions and gases in the equilibrium expression because their concentrations can change. The molar concentration of pure substances that are in liquid and solid form don't change, so we leave them out.
by Alex Chen 1B
Fri Nov 11, 2016 3:06 pm
Forum: Naming
Topic: Order of ligands in the reverse naming
Replies: 1
Views: 236

Re: Order of ligands in the reverse naming

When you're writing the formula for the coordination compound, the ligands are written in alphabetical order according to their symbols. So for example, pentaaquachloridoiron(II) ion is written as [FeCl(OH2)5]+. Cl comes before OH2 alphabetically, so you written them in that order despite the fact t...
by Alex Chen 1B
Tue Nov 08, 2016 10:02 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Ch 4 Question 67 [ENDORSED]
Replies: 1
Views: 326

Re: Ch 4 Question 67 [ENDORSED]

Since the electron being removed from C2- is in a higher energy molecular orbital, it takes less energy to remove it. It's the same concept as the periodic trend for ionization energy. The valence electrons of elements lower in the periodic table are in higher energy orbitals than the electrons of e...
by Alex Chen 1B
Wed Nov 02, 2016 11:23 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Midterm 2015 #4
Replies: 1
Views: 370

Re: Midterm 2015 #4

The VSEPR formula for XeF2 is AX2E3. Since there are five regions of electron density around Xe, the geometry of the molecule is trigonal bipyramidal. The three lone pairs have to be the three regions of electron density that are in one plane, because this minimizes the lone pair-lone pair repulsion...
by Alex Chen 1B
Tue Oct 25, 2016 10:04 pm
Forum: Lewis Structures
Topic: N2O Lewis Structure; how can N form a double bond?
Replies: 1
Views: 4544

Re: N2O Lewis Structure; how can N form a double bond?

The N in Structure 2 can form a double bond and have two lone pairs because one of the bonds in the double bond is a coordinate covalent bond, which means that one of the atoms in the bonded pair supplies both electrons for the bond. So in this case, one electron in the double bond came from left-mo...
by Alex Chen 1B
Sat Oct 22, 2016 2:12 am
Forum: Coordinate Covalent Bonds
Topic: Electron Distortion and Chemical Bonds
Replies: 1
Views: 5280

Re: Electron Distortion and Chemical Bonds

Electron distortion is when the electrons of the anion are attracted to the cation, which causes the shape of the electron density to change slightly. When we talk about ionic bonds, we usually think it means a bond where the more electronegative atom has completely removed an electron from the less...
by Alex Chen 1B
Wed Oct 12, 2016 2:36 pm
Forum: Properties of Electrons
Topic: Removing 2nd Electron
Replies: 2
Views: 1040

Re: Removing 2nd Electron

It becomes harder to remove an electron when an atom has a net positive charge because the attraction that the nuclear charge exerts per electron gets larger. For example, if you have a neutral nitrogen atom, it has 7 electrons. The nuclear charge exerted by the 7 protons in the nucleus is distribut...
by Alex Chen 1B
Thu Oct 06, 2016 2:06 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework problem 1.69 [ENDORSED]
Replies: 1
Views: 321

Re: Homework problem 1.69 [ENDORSED]

They give you the work function of lithium in the problem, which is 2.93 eV. You can find the conversion from eV to J online and it's 1 J = 6.2415*10^18 eV. Since the work function is equal to the threshold energy necessary to eject an electron from the metal surface, you can use it to figure out th...
by Alex Chen 1B
Wed Oct 05, 2016 12:42 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg vs. En equation for H atom
Replies: 1
Views: 735

Re: Rydberg vs. En equation for H atom

Yes, the R's in the Rydberg formula and the En formula are different variables. If you use the En formula, subtract E(initial) from E(final) and set it equal to h*c/(wavelength), you can derive the Rydberg formula. The R in the Rydberg formula is equal to the quotient of the R from the En formula an...
by Alex Chen 1B
Tue Sep 27, 2016 10:30 am
Forum: Significant Figures
Topic: Sig Figs Throughout Problems
Replies: 12
Views: 4025

Re: Sig Figs Throughout Problems

You shouldn't round during the problem, but you should definitely keep track of the sig figs on each calculation that you make as you progress through the problem. And once you reach your final answer, figure out how many sig figs there are based on the sig figs of your previous calculations. One me...

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