## Search found 45 matches

Fri Dec 12, 2014 2:34 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: 11.65 (% deprotonation)
Replies: 4
Views: 2390

### Re: 11.65 (% deprotonation)

The solutions are right. Since 2.4% is deprotonated, then 1-.024 is not deprotonated, and stays as benzoic acid. I dont know where you got .110 - .024, because thats not how percentages work. Also .110 - .024 is not .110, since .024 is not 0.
Wed Dec 10, 2014 5:57 pm
Forum: Calculating the pH of Salt Solutions
Topic: pH of AlCl3
Replies: 2
Views: 2270

### Re: pH of AlCl3

Because AlCl dissociates into Al3+ and Cl-. Al with a +3 charge is hydrated, because H2O is polar, creating Al(H2O)6.
Wed Dec 10, 2014 5:55 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: How do you know which compounds dissociate completely?
Replies: 1
Views: 3788

### Re: How do you know which compounds dissociate completely?

Hi Leiana!
Salts with NO3- or Cl- are generally soluble, except AgCl PbCl2 and Hg2Cl2. If you want to be sure just memorize these solubility rules.
http://www.csudh.edu/oliver/chemdata/solrules.htm
Wed Dec 10, 2014 5:33 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Q8 2009 Final Exam
Replies: 1
Views: 346

### Re: Q8 2009 Final Exam

The first reaction, with HCl and NaHCO3 is only for determining the amount of HCOOH created and NaHCO3 used. In the second reaction, you can use either HCOOH as the reactant HCOOH > H+ + HCOO-, or as the product HCOO + H2O > HCOOH + OH-. The first equation is just more convenient, because you are gi...
Wed Dec 10, 2014 5:20 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: J.13(b) Fundamentals - Na3AsO4 weak base
Replies: 2
Views: 1315

### Re: J.13(b) Fundamentals - Na3AsO4 weak base

Calculate Molar Mass by adding the atomic masses together (Na+Na+Na+As+O+O+O) = MM. 35.0g/MM = mol of Na3AsO4. THen Na3AsO4 x 3 = mol Na+.
Wed Dec 10, 2014 5:16 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: 11.65 (% deprotonation)
Replies: 4
Views: 2390

### Re: 11.65 (% deprotonation)

Percent Deprotonation is the percentage of the initial acid that creates H3O+ and it's conjugate base. This would be .110 x 2.4% =x molarity of Benzoic acid converted to H+ and Benzoate. To find pH take -log(x), and to find Ka use x^2/(.110 -x).
Wed Dec 03, 2014 11:35 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 #10
Replies: 8
Views: 1064

### Re: Quiz 3 #10

You get similar answers for atm and bar, since the constants are similar (8.31x10^-2 vs 8.21x10^-2), and if you round to 2 sig figs in your answer, you get the same answer for one, and .01 off for the other. But for Torr, the answer is way off.
Tue Dec 02, 2014 5:53 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Why can CO3(2-) be a mono/bidentate ligand
Replies: 3
Views: 6147

### Re: Why can CO3(2-) be a mono/bidentate ligand

Normally Carbonate is monodentate, because it only has 120 degrees between its Oxygens, so two oxygens cannot bind to the same metal. However, in some cases carbonate bonds to two different metals, making it bidentate.
Tue Dec 02, 2014 5:38 pm
Forum: Lewis Acids & Bases
Topic: HW Question 11.17
Replies: 3
Views: 611

### Re: HW Question 11.17

SO2 actually has 3 resonance structures, even though it makes no sense according to formal charge. It's just something you have to know, since SO2 is considered polar, even though according to formal charge it's not. See page 69 of the course reader.
Tue Dec 02, 2014 5:36 pm
Forum: Naming
Topic: Neutral Ligands Order
Replies: 1
Views: 266

### Re: Neutral Ligands Order

Name it in alphabetical order.
Tue Dec 02, 2014 5:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 #10
Replies: 8
Views: 1064

### Re: Quiz 3 #10

Yes it does matter, but you do not know which unit to use because it is not given in the question. I'm pretty sure Lavelle forgot to put it in. I'm just writing down three different answers.
Tue Dec 02, 2014 5:22 pm
Forum: Molarity, Solutions, Dilutions
Topic: Why doesn't a solute add to the volume of a solution? [ENDORSED]
Replies: 6
Views: 3200

### Re: Why doesn't a solute add to the volume of a solution?[ENDORSED]

Yes, in the real world we would also calculate the volume added by the solute. However, the volume is so little that it is negligible in our calculations.
Tue Dec 02, 2014 5:17 pm
Forum: Naming
Topic: Naming Bis Tris Tetrakis
Replies: 4
Views: 809

### Re: Naming Bis Tris Tetrakis

You change the prefix even if they do not match, so you would use tris(ethylenediamine).
Tue Dec 02, 2014 5:16 pm
Forum: Naming
Topic: Elements before the brackets
Replies: 4
Views: 612

### Re: Elements before the brackets

Yes, if they come before the brackets, that means they are the cation balancing out the coordinate complex (anion).
Tue Dec 02, 2014 5:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 #10
Replies: 8
Views: 1064

### Re: Quiz 3 #10

I think you guys are talking about two different questions. The question asked was from this year's practice quiz. You do not need Kc, you only need Kp. First you use P = nRT/V to find Ph2o. Then, draw an ice table to find an equation for Kp, which is given (3.72). Use the quadratic formula to solve...
Tue Dec 02, 2014 5:07 pm
Forum: Naming
Topic: Oxidation number in coordination compounds
Replies: 2
Views: 620

### Re: Oxidation number in coordination compounds

If the coordinate complex is the cation, oxidation number = sum of negative charges of all ligands and anions
If the coordinate complex is the anion, oxidation number = total negative charge of ligands - positive charge of cations
Basically just balance the charges to = 0.
Mon Dec 01, 2014 12:44 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectroscopy patterns of Hydrogen
Replies: 1
Views: 326

### Re: Atomic Spectroscopy patterns of Hydrogen

Yes, multiple Hydrogen atoms must be present, or numerous trials on one Hydrogen atom need to be done. Yes, only one line would appear if we only excited one electron one time. Yes, multiple lines are in the atomic spectra because the electron is beginning and ending at different energy levels for e...
Mon Dec 01, 2014 12:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Significant Figures
Replies: 4
Views: 530

### Re: Significant Figures

You only have to have the correct number of sigfigs for the last answer that you box. For the steps you take to get to the answer, you do not need to have correct sigfigs. However, be careful that you don't truncate numbers in each step, or else the answer you get will not be accurate, even if you h...
Mon Dec 01, 2014 12:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant: Concentration vs. Partial Pressure
Replies: 2
Views: 577

### Re: Equilibrium Constant: Concentration vs. Partial Pressure

Use Partial Pressure for gasses, and concentration for solutions. If there is enough information for both cases, either way you'll get the same K, because Partial Pressure = [conc]RT, and if you calculate PPressure(Products)/PPressure(Reactants) then it would be [conc]RT/[conc]RT, and the RT cancels...
Tue Nov 04, 2014 4:32 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Character and Covalent Character
Replies: 4
Views: 1239

### Re: Ionic Character and Covalent Character

Ionic character giving/taking electrons, covalent character is sharing electrons. A bond has covalent bond has ionic character when the bond is very polar, or when the difference in electronegativity is high (greater than .5). Covalent character is the opposite, when difference in electronegativity ...
Tue Nov 04, 2014 3:41 pm
Forum: Ionic & Covalent Bonds
Topic: 2.75
Replies: 1
Views: 380

### Re: 2.75

An Ionic bond is defined as a difference in electronegativity greater than 2.0. So whichever acid has a greater difference in electronegativity. In this case HCl, since Cl is higher than I on the periodic table.
Tue Nov 04, 2014 3:32 pm
Forum: Lewis Structures
Topic: Question 2.95 in the textbook
Replies: 1
Views: 370

### Re: Question 2.95 in the textbook

In most cases, Nitrogen forms 3 bonds, while keeping a sp3 hybridized lone pair to itself. However, in this case, Nitrogen shares both electrons to form a bond. When drawing Lewis structures, follow the rules (C makes 4 bonds, N makes 3 bonds) as a general guideline, but not always. Since this quest...
Tue Nov 04, 2014 3:07 pm
Forum: Lewis Structures
Topic: Bond Angles
Replies: 1
Views: 378

### Re: Bond Angles

Yes, the lone pair distorts the bond angle for see-saw because lone-pair bonding-pair repulsion is stronger, so it will be 90 degrees for the angles between the top and center bonds, but it will be less than 120 degrees between the two center bonds. For square planar, the lone pairs do not distort t...
Mon Nov 03, 2014 2:03 pm
Forum: Lewis Structures
Topic: Structure of SF4 in homework problem 3.19D
Replies: 1
Views: 477

### Re: Structure of SF4 in homework problem 3.19D

It is polar because of the lone pair on the S. SF4 is AX4E, which means it has a see-saw shape, which is a polar shape.
Mon Nov 03, 2014 1:59 pm
Forum: Lewis Structures
Topic: Mistake in solutions for Textbook 2.61(d)
Replies: 1
Views: 354

### Re: Mistake in solutions for Textbook 2.61(d)

You are right. There are 4 bonds and one lone pair. 4 bonds = 4x2 = 8 electrons. 8 electrons + additional lone pair (2 electrons) = 10 electrons.
Mon Nov 03, 2014 1:55 pm
Forum: Lewis Structures
Topic: Textbook Question 3.19 a
Replies: 1
Views: 267

### Re: Textbook Question 3.19 a

You can in the lewis structure, but to determine if a molecule is polar or nonpolar you have to consider the shape. Putting the Cl opposite each other in the lewis structure would be correct, but in 3 dimensions they are not opposite each other, since there is a tetrahedral shape. Therefore the mole...
Mon Nov 03, 2014 1:38 pm
Forum: Lewis Structures
Topic: 2 #101 Ground State v Excited State
Replies: 2
Views: 451

### Re: 2 #101 Ground State v Excited State

If the electron configuration follows the Aufbau principle of building up, then it is ground state. If it doesnt follow this principle then it is excited. For example, if the electron configuration for Lithium was 1s2, 2s1, then it would be in ground state. If it were 1s2, 2p1, then it is excited. I...
Mon Nov 03, 2014 12:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Atom arrangement of CH2Cl2
Replies: 1
Views: 1970

### Re: Atom arrangement of CH2Cl2

Hi Grace!
You would be right if CH2Cl2 had a square planar geometry, but its steric number is 4, not 6. Therefore you know it has a tetrahedral geometry, and if you pick any two places for Cl and H to be randomly, you would see it has a net dipole moment towards the side with the two H.
Sat Oct 25, 2014 4:21 pm
Forum: Lewis Structures
Topic: Exceptions to Octet Rule
Replies: 1
Views: 343

### Re: Exceptions to Octet Rule

Theoretically, they could accomodate more than 8 electrons. However, this does not happen since Al and Si do not have enough protons to attract so many electrons. Think of it in terms of formal charge: since Al only has 3 valence electrons, (L + S/2) cannot be too high. This is why Boron usually has...
Sat Oct 25, 2014 4:14 pm
Forum: Quantum Numbers and The H-Atom
Topic: Rydberg's General Equation
Replies: 1
Views: 350

### Re: Rydberg's General Equation

The negative sign refers to the bonding energy between the nucleus and the electron, showing that it takes outside energy input to move the electron to a higher energy level. If you set up the problem correctly, you do not have to ignore the negative sign. Usually the case is Einitial - Efinal = Eli...
Sat Oct 25, 2014 3:59 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration of Nb
Replies: 1
Views: 999

### Re: Electron Configuration of Nb

This is one of the many exceptions on the periodic table, because the energy gap between the 4d and 5s orbitals is small enough for the electron to be pulled from the 5s orbital due to electron repulsion, sort of like Hund's rule except applied across orbitals.
Tue Oct 21, 2014 2:07 pm
Forum: Molarity, Solutions, Dilutions
Topic: Fall 2012 Quiz 1 Preparation, #10
Replies: 4
Views: 754

### Re: Fall 2012 Quiz 1 Preparation, #10

The one with the limiting reactant.
Mon Oct 20, 2014 5:20 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr Frequency and Light Emission Frequency
Replies: 3
Views: 746

### Re: Bohr Frequency and Light Emission Frequency

Nevermind what I first posted, I was thinking of the photoelectric effect. You are correct, that light is absorbed only if it matches the energy gap for the electron to jump. However, the energy of the light emitted is still not always equal to the energy of the light absorbed. This is because the e...
Mon Oct 20, 2014 2:14 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Quiz 1 Preparation #3, Question 10
Replies: 4
Views: 634

### Re: Quiz 1 Preparation #3, Question 10

1. Calculate E for n=4 using E = -hR/n^2
2. Calculate E for v = 1.14 x 10^14 Hz using E = hv
3. Since E4 is the final state, you need to add E-light to get the E of the initial state.
4. Calculate n using E-final = -hR/n^2
Mon Oct 20, 2014 2:10 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr Frequency and Light Emission Frequency
Replies: 3
Views: 746

### Re: Bohr Frequency and Light Emission Frequency

"In regards to the hydrogen atom, the incoming light that is being absorbed by the electron has a certain frequency whose energy matches the energy difference between the two energy levels." No, the incoming light does not have a certain frequency, but has a threshold frequency. The freque...
Mon Oct 20, 2014 1:57 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Quiz 1 Preparation (2012) #8
Replies: 2
Views: 431

### Re: Quiz 1 Preparation (2012) #8

n1 implies that it is the energy shell that the electron starts off in. n1 means "n first". n2 means "n second", so the question does specify an order.
Mon Oct 20, 2014 1:49 pm
Forum: Empirical & Molecular Formulas
Topic: Chemical Reactions
Replies: 1
Views: 307

### Re: Chemical Reactions

Here are the steps to take:
1. Balance the reaction
2. Calculate the mol of reactant by dividing the mass of a reactant by its molar mass.
3. Using Mole ratios from the equation, find the mol of product formed
4. Multiply mol of product by the Molar Mass of product to get mass of a product formed.
Mon Oct 20, 2014 1:47 pm
Forum: Empirical & Molecular Formulas
Topic: Combustion and Solving for Empirical and Molecular Formula
Replies: 1
Views: 289

### Re: Combustion and Solving for Empirical and Molecular Formu

Actually you are right, all combustion does require oxygen. This also applies to the problem, and you can find the amount of oxygen used in the combustion by subtracting the mass of the sample from the total mass of the products. .3664g + .1500g = .5164g of product was formed, but there was only .25...
Mon Oct 20, 2014 1:34 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Valence shell
Replies: 1
Views: 484

### Re: Valence shell

The valence shell is 5s25p1. That is why the most common ion of Indium is In3+, since the three electrons in the n=5 shell are taken, giving it a 3+ charge.
Mon Oct 20, 2014 1:30 pm
Forum: Photoelectric Effect
Topic: Fall 2012 Quiz 1 Preparation, #10
Replies: 1
Views: 317

### Re: Fall 2012 Quiz 1 Preparation, #10

You start by balancing the equation, adding a coefficient (2) in front of AgNO3 and AgCl. Next, calculate the mols of reactants you are given, by multiplying the Molarity by the amount in liters you are given. .55 x .06 = .033 mol CaCl2, and .22 x .125 = .0275 mol AgNO3. From this you can see that A...
Mon Oct 20, 2014 1:30 pm
Forum: Molarity, Solutions, Dilutions
Topic: Fall 2012 Quiz 1 Preparation, #10
Replies: 4
Views: 754

### Re: Fall 2012 Quiz 1 Preparation, #10

You start by balancing the equation, adding a coefficient (2) in front of AgNO3 and AgCl. Next, calculate the mols of reactants you are given, by multiplying the Molarity by the amount in liters you are given. .55 x .06 = .033 mol CaCl2, and .22 x .125 = .0275 mol AgNO3. From this you can see that A...
Mon Oct 13, 2014 10:24 am
Forum: Molarity, Solutions, Dilutions
Topic: G 11 and 13b
Replies: 1
Views: 356

### Re: G 11 and 13b

For 13b. you want 60mL of .5M solution. .5x.06=.03mol NaOH. To get that from 2.5M solution you need .03/2.5=12mL of NaOH. Then add 60-12 = 48mL of water. Another way to think of it is you want 1/5th the concentration, so only add 1/5 of the solution and 4/5 water. 1/5 x 60 = 12mL. For 11 use the fir...
Sun Oct 12, 2014 3:56 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Hydrogen Atom- Atomic Spectra Workbook question
Replies: 1
Views: 334

### Re: Hydrogen Atom- Atomic Spectra Workbook question

You are right: n1 is the first energy level, and n2 is the third energy level. To put this into the equation, you would solve for energy twice--once using n1 (1), and once using n2 (3). E1 = -hR/(n1)^2 = -hR/(1)^2. Then solve for energy for n2: E2 = -hR/(n2)^2 = -hR/(3)^2. once you have E1 and E2, f...
Sun Oct 12, 2014 3:46 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Derive Heisenberg Equation
Replies: 3
Views: 512

### Re: Derive Heisenberg Equation

It is not possible to derive Heisenberg's equation from the equations we have learned, as it was derived through matrices. The equation comes from QP-PQ=ih/2pi. I don't know what this means, but for this class we only need to know how to use Heisenberg's equation.
Sat Oct 11, 2014 7:50 pm
Forum: DeBroglie Equation
Topic: de Broglie wavelength vs. Planck length
Replies: 3
Views: 788

### Re: de Broglie wavelength vs. Planck length

I did some research on it, and it appears Planck length (1.616199(97)×10^−35 m) is several magnitudes smaller than the lengths we can currently measure with our technology, so no, there is no research on its implications for matter waves. But theoretically speaking, as Planck length is the shortest ...