## Search found 35 matches

Wed Jun 13, 2018 10:41 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ka on final, 12.25 [ENDORSED]
Replies: 3
Views: 443

### Ka on final, 12.25[ENDORSED]

Are we expected to calculate pH, Ka, Kb on the final? For example, problems 12.19, 12.25, 12.27 in the book deal with calculating pH.
Thu Jun 07, 2018 9:17 pm
Forum: Bronsted Acids & Bases
Topic: J.5
Replies: 2
Views: 266

### J.5

For question J.5, it asks to write the overall, complete ionic, and net ionic equation. For part c) OH-(aq) + H+(aq) --> 2H2O(l), I don't understand why there is a 2H20 instead of just H2O in the net ionic equation OH- + H+ --> 2H2O. Could someone explain this?
Thu Jun 07, 2018 9:12 pm
Forum: Lewis Acids & Bases
Topic: Ionic Equations and net ionic equation
Replies: 3
Views: 217

### Re: Ionic Equations and net ionic equation

In the net ionic equation, the ions common to both sides cancel out, so for example if there is an Li+ on both the reactants and products side, you could cancel these and the net ionic equation would not have Li+ included.
Thu Jun 07, 2018 6:40 pm
Forum: Bronsted Acids & Bases
Topic: H3O vs H2O
Replies: 5
Views: 652

### Re: H3O vs H2O

In the last example with HBr and KOH, what is the acid and what is the base?
Thu Jun 07, 2018 4:14 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 17.35
Replies: 1
Views: 115

### 17.35

I'm confused on the definition of a chelate and a chelating complex, for example in 17.35 it asks which of the isomers of diaminobenzene can form chelating complexes. Is the answer only b since the NH2's are close enough together, and how do you know if they're close enough? I also know that a chela...
Sat Jun 02, 2018 10:28 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Naming shape
Replies: 7
Views: 429

### Naming shape

In our discussion, we were trying to clarify what the wording of the problem will be when it's asking for the shape, looking at lone pairs or not. To clarify, if a problem asks to state the molecular shape, is this the shape only looking at the atoms, and the geometry of the molecule is the VSEPR na...
Sat Jun 02, 2018 12:17 am
Forum: Hybridization
Topic: Textbook 4.37
Replies: 3
Views: 204

### Re: Textbook 4.37

For PCl3 when drawing out the Lewis structures, you can see that P has 4 regions of electron density surrounding it, so this is why it is sp3. I think that drawing out the structures for these problems also helps.
Fri Jun 01, 2018 1:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.25 a
Replies: 2
Views: 200

### Re: 4.25 a

Since the shape is a tetrahedral (3D shaped), the charges do not cancel out. It's polar since Cl has a stronger pull on electrons than the H atoms.
Fri Jun 01, 2018 12:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.3 Structure and Shape [ENDORSED]
Replies: 4
Views: 225

### Re: 4.3 Structure and Shape[ENDORSED]

I think that it's hard to find the molecular shape without drawing out the Lewis diagram, for example some molecules may have bond angles and lone pairs, and you wouldn't know the shape without drawing these out.
Fri Jun 01, 2018 12:46 pm
Forum: Dipole Moments
Topic: London vs. Dipole
Replies: 3
Views: 659

### Re: London vs. Dipole

In one of the homework problems from chapter 6, it asks what possible intermolecular forces occur in the molecules given, and for each of the molecules, London forces can always occur. London/Vander waals forces are small/weak temporary interactions and can occur quite frequently, whereas dipoles oc...
Wed May 30, 2018 7:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: HW 4.9
Replies: 10
Views: 1084

### Re: HW 4.9

Are we expected to memorize these bonding angles? How do you know that the bonding angle is slightly less than 90 degrees?
Wed May 30, 2018 5:22 pm
Forum: Dipole Moments
Topic: 6.1 and 6.19 question
Replies: 3
Views: 274

### 6.1 and 6.19 question

For question 6.1 in the textbook, it asks to identify what kinds of intermolecular forces arise between the molecules given. For SO2 the solutions say it could be a dipole-dipole interaction, but I don't understand why this could occur. Also in question 6.19, I'm confused on how London forces/Hydrog...
Thu May 24, 2018 7:16 pm
Forum: Lewis Structures
Topic: Finding the central element on the Lewis structure
Replies: 4
Views: 648

### Re: Finding the central element on the Lewis structure

Electronegativity generally increases from left to right, not right to left. Flourine is the most electronegative, and FONCl (most to least electronegative) is just a good way to remember electronegativity. So if the molecule is NOF, N would be the center because it is the LEAST electronegative. htt...
Tue May 22, 2018 12:53 pm
Forum: Lewis Structures
Replies: 3
Views: 251

I think that the more electronegative atom tends to pull the electrons closer to it, so the atom with the radical would be the one that is less electronegative.
Mon May 21, 2018 8:39 pm
Forum: Ionic & Covalent Bonds
Topic: Polarization
Replies: 7
Views: 593

### Re: Polarization

3.81 Arrange the cations Rb+, Be2+, and Sr2+ in order of increasing polarizing power. Give an explanation of your arrangement. 3.83 Arrange the anions Cl-, Br-, N3-, and O2- in order of increasing polarizability and give reasons for your decisions. So for this problem, can you say that polarizing po...
Sat May 19, 2018 5:25 pm
Forum: Formal Charge and Oxidation Numbers
Topic: HW 3.57 [ENDORSED]
Replies: 2
Views: 333

### Re: HW 3.57[ENDORSED]

Is it the most or least electronegative atom that has the negative charge? I had written down the least electronegative atom in my discussion, but now I'm confused since this problem has O with a -1 formal charge and the previous problem on that worksheet [S3N3]- said that S having the -1 charge is ...
Sat May 19, 2018 4:48 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charge in (S2CO)2-
Replies: 3
Views: 2220

### Formal charge in (S2CO)2-

One of the questions in my discussion last week said to draw resonance structures where appropriate and to label formal charges, and to rank resonance structures in order of importance to overall structure. For [S2CO]2-, the answer says that the best way to draw the structure is to put a formal char...
Sun May 13, 2018 9:04 pm
Forum: Ionic & Covalent Bonds
Topic: 3.25 part c
Replies: 3
Views: 222

### 3.25 part c

Could someone explain how to go through this problem:
On the basis of the expected charges on the monatomic ions, give the chemical formula of each of the following compounds: c) aluminum hydride
I don't explain why the answer is AlH3, because I thought that Al would have a 2+ charge.
Thu May 10, 2018 11:54 pm
Forum: Quantum Numbers and The H-Atom
Topic: Midterm Question
Replies: 13
Views: 750

### Re: Midterm Question

Subshell notation is l, and orbital notation is ml. The amount of orbitals is the values of ml, so for example when l=2, this would be a d orbital, with ml=-2,-1,0,1,2. This has 5 orbitals.
Wed May 09, 2018 8:40 pm
Forum: Trends in The Periodic Table
Topic: Zeff HW 2.37
Replies: 2
Views: 223

### Re: Zeff HW 2.37

I had the same confusion, since Zeff increases across a period, but I think that for this question, it's looking at just one atom, where the s orbital is closer to the nucleus and the p orbital is farther away from the nucleus.
Thu May 03, 2018 9:01 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2.43 part e
Replies: 1
Views: 63

### 2.43 part e

For question 2.43 part e, it asks for the ground state electron configuration of tungsten. the answer is [Xe]4f^145 d^4 6s^2, and I was wondering if you always put this f orbital in when it's an element after the lanthanoids on the d block. Also, I'm wondering why d^4 was not converted to d^5, since...
Thu May 03, 2018 6:01 pm
Forum: Quantum Numbers and The H-Atom
Topic: 2.29
Replies: 9
Views: 679

### Re: 2.29

I am also confused on part d, I know that it's in the 3d shell, and I'm not sure what you're supposed to do when given m1=+1.
Mon Apr 30, 2018 11:22 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: PROBLEM 2.1
Replies: 4
Views: 246

### Re: PROBLEM 2.1

For the radius of the atom, my first thought was that the radius would decrease, since we learned in class that when moving across a period, the radius generally decreases. I know that the radius does decrease though since n is moving from 1 to 2, so should we not think of placement on the periodic ...
Sat Apr 28, 2018 10:29 pm
Forum: Photoelectric Effect
Topic: What is work function? [ENDORSED]
Replies: 15
Views: 3506

### Re: What is work function?[ENDORSED]

Is there an actual equation for the work function, or will it always be given to you?
Sat Apr 28, 2018 10:26 pm
Forum: Properties of Light
Topic: photoelectric effect
Replies: 4
Views: 254

### Re: photoelectric effect

The experiment revealed that electrons not only have wave like properties but also particle like properties, since increasing the brightness/amplitude of the light did not affect the energy.
Thu Apr 26, 2018 11:32 pm
Forum: DeBroglie Equation
Topic: DeBroglie
Replies: 7
Views: 412

### Re: DeBroglie

In class the example was to find the wavelength of a 0.1 kg baseball traveling at a velocity of 35 m/s. You would use the DeBroglie Equation, wavelength=h/m*v to solve this.
Sat Apr 21, 2018 9:51 pm
Forum: Einstein Equation
Topic: Planck's Constant Value [ENDORSED]
Replies: 7
Views: 2999

### Re: Planck's Constant Value[ENDORSED]

I think for intermediate calculations it's always safer to put more decimals for a greater accuracy.
Sat Apr 21, 2018 9:48 pm
Forum: Photoelectric Effect
Topic: Significance of intensity [ENDORSED]
Replies: 7
Views: 399

### Re: Significance of intensity[ENDORSED]

I also believe that the intensity is another word to describe brightness, so the higher the brightness, the greater the intensity.
Thu Apr 19, 2018 10:45 pm
Forum: Properties of Light
Topic: 1.3 Atomic Spectra- Rydberg's equation
Replies: 3
Views: 226

### Re: 1.3 Atomic Spectra- Rydberg's equation

In class we found the change in energy, and used this to find the frequency and could subsequently find the wavelength. In the solutions manual they sue Rydberg's equation v= R(1/(n1)^2 - 1/(n2)^2), so I was also wondering if we should use this equation for problems since it's shorter or stick to th...
Fri Apr 13, 2018 11:26 am
Forum: Limiting Reactant Calculations
Topic: Question 8 on UA's Practice Test
Replies: 3
Views: 170

### Re: Question 8 on UA's Practice Test

Another way to do this problem using dimensional analysis is to start with both grams given and convert to g of ALCL3, so this way you can determine the limiting reactant and g of ALCL3 all in one step.
Fri Apr 13, 2018 10:49 am
Forum: Limiting Reactant Calculations
Topic: Different ways of determining limiting reactants
Replies: 2
Views: 185

### Different ways of determining limiting reactants

From lecture and discussion, it seems that there are multiple ways of determining the limiting reactant. Is there one way that is best? For example, converting both reactants into moles of a product of an equation and seeing which one is less? Or comparing the results in grams? Or choosing one react...
Fri Apr 13, 2018 10:40 am
Forum: Limiting Reactant Calculations
Topic: actual vs. theoretical yield [ENDORSED]
Replies: 6
Views: 789

### Re: actual vs. theoretical yield[ENDORSED]

Usually in a problem with calculating the percentage yield, you will be given the actual yield, which is less than the theoretical yield that you will be calculating. So an easy way to check your work in a problem like this is to make sure that the theoretical yield you calculate is more than the ac...
Thu Apr 05, 2018 9:48 pm
Forum: Balancing Chemical Reactions
Topic: H.5.b [ENDORSED]
Replies: 7
Views: 524

### Re: H.5.b[ENDORSED]

Yes, Mg(N3)2 would become MgN6. This just means that there are 6 N, so you would also need 6 N on the other side of the equation. When there's a number outside the parentheses you multiply that number by the subscript in the parentheses (so if you had (H6)2 in subscripts it would be the same as H12)...
Thu Apr 05, 2018 9:41 pm
Forum: SI Units, Unit Conversions
Topic: E.15 confusion
Replies: 2
Views: 190

### Re: E.15 confusion

When they subtracted the grams and got 40, they saw that 40 g/mol is the molar mass of Calcium. Because of this , the metal M is Calcium (since it wasn't given to you previously). The question asks what is the molar mass of the sulfide of this metal, so since you know that the metal is calcium, you ...
Thu Apr 05, 2018 9:12 pm
Forum: Molarity, Solutions, Dilutions
Topic: G.5 part a [ENDORSED]
Replies: 3
Views: 239

### Re: G.5 part a[ENDORSED]

They use this number since part a is 2.15 mmol, which stands for millimole. This means that there are 1000 millimoles in 1 mole, so that's why they used 2.15 x 10^-3.