## Search found 51 matches

Sat Dec 07, 2019 11:47 pm
Forum: Air Pollution & Acid Rain
Topic: Final Exam
Replies: 5
Views: 401

### Final Exam

To what extent do we need to have an understanding of acid rain? Do we need to know the chemical formula
Sat Dec 07, 2019 4:02 pm
Forum: Identifying Acidic & Basic Salts
Topic: 6.21 part (c)
Replies: 1
Views: 69

### 6.21 part (c)

Can someone explain why the nitro groups on thymine are amphiprotic? And how would you write proton transfer equilibria equations with these groups?
Sat Dec 07, 2019 3:23 pm
Forum: Identifying Acidic & Basic Salts
Topic: 6D.11 (e) & (f)
Replies: 2
Views: 156

### 6D.11 (e) & (f)

I know that in AlCl3 and Cu(NO3)2, the Al3+ and Cu2+ are highly charged metal cations, and their pull allows water molecules to pick up another H+ and therefore make the solution more acidic. However, I'm really struggling on writing out equations to demonstrate this. For example, in the solution gu...
Sat Dec 07, 2019 2:07 pm
Forum: Bronsted Acids & Bases
Topic: Relative strength of acids
Replies: 1
Views: 85

### Relative strength of acids

When determining the relative strength between 2 acids, are you supposed to compare the bond length and anion stability of their conjugate bases? Or the compound as is?
Sat Dec 07, 2019 2:03 pm
Forum: Lewis Acids & Bases
Topic: Differentiating Lewis Acids/Bases
Replies: 1
Views: 91

### Differentiating Lewis Acids/Bases

I have read through the textbook and I'm still a little confused on how to determine whether a compound is a Lewis acid or Lewis base. I know a Lewis acid is an electron acceptor and a Lewis base is an electron donor, but I'm not quite sure how to look at a compound and determine this. Is it based o...
Sat Nov 30, 2019 9:57 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Monodentate and Bidentate Ligands
Replies: 2
Views: 99

### Monodentate and Bidentate Ligands

In homework problem 9C.5, (CO3)2- is revealed to be both monodentate and bidentate. Can someone explain how this is possible? Also, are there any other ligands that fall under this category we need to know?
Sat Nov 30, 2019 9:54 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Monodentate and Bidentate Ligands [ENDORSED]
Replies: 1
Views: 402

### Monodentate and Bidentate Ligands[ENDORSED]

In homework problem 9C.5, (CO3)2- is revealed to be both monodentate and bidentate. Can someone explain how this is possible? Also, are there any other ligands that fall under this category we need to know?
Sat Nov 30, 2019 9:50 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating Ligands
Replies: 2
Views: 76

### Chelating Ligands

The definition of a chelate as given in lecture is that it is a complex containing a ligand that forms a ring of atoms that includes the central metal atom. I don't understand how to apply this definition to the homework problems. If a ligand is polydentate, does that mean it is a chelating ligand? ...
Sat Nov 30, 2019 9:45 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 1
Views: 74

### Coordination Number

Question 9C.9 in the textbook homework is related to determining a metal ion's coordination number. For part (c), en is bidentate, causing the coordination number of the complex to be 6. For part (d), edta is hexadentate, causing the coordination number of the complex to be 6. How and why does a lig...
Sat Nov 30, 2019 9:42 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentates [ENDORSED]
Replies: 1
Views: 70

### Polydentates[ENDORSED]

When doing the homework and referencing the charts in the textbook, it is evident that water is monodentate even though the oxygen in it contains two lone pairs. Is determining if a ligand is mono, bi, or polydentate directly related to the number of lone pairs it contains? If it is related to lone ...
Sat Nov 23, 2019 2:54 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Bronsted acids
Replies: 5
Views: 204

### Bronsted acids

Can someone explain/summarize what we need to know about Bronsted acids? I was kinda confused when he went over them in lecture on Friday.
Sat Nov 23, 2019 2:51 pm
Forum: Biological Examples
Topic: Biological Examples
Replies: 10
Views: 156

### Re: Biological Examples

Because conceptual questions are included in Lavelle's midterms and final, it would definitely be helpful to know the biological examples/functions of the transition metals he went over in class. I don't think he'd test us on an obscure example he didn't go over in depth.
Sat Nov 23, 2019 2:49 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelates
Replies: 1
Views: 65

### Chelates

Can someone explain how the concept of chelates could show up as a problem on the test?
Sat Nov 23, 2019 2:46 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxalato
Replies: 3
Views: 87

### Re: Oxalato

I believe it has a -2 charge
Sat Nov 23, 2019 2:43 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Transition Metals
Replies: 2
Views: 58

### Transition Metals

Can someone explain what it means for a transition metal complex to be organometallic?
Sun Nov 17, 2019 3:39 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 3F.19
Replies: 2
Views: 46

### 3F.19

In question 3F.19 in the textbook, part b asks you to explain why the vapor pressure of diethyl ether (C2H5OC2H5) is greater than that of water. What is the correlation between vapor pressure and boiling point? Also, in part c, it asks you to explain why the boiling point of pentane, CH3(CH2)3CH3, i...
Sun Nov 17, 2019 3:34 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 3F.5
Replies: 1
Views: 34

### 3F.5

On part (c) of 3F.5 in the textbook, it asks if CHI3 of CHF3 has a higher boiling point. I assumed it was CHF3, as there is a larger difference in electronegativity between C and F than C and I, therefore the bonds would be stronger and harder to boil in CHF3. However, the answer key says that CHI3 ...
Sun Nov 17, 2019 3:31 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 3F.3
Replies: 1
Views: 24

### 3F.3

On part (c) of question 3F.3 in the textbook, it asks if there are dipole-dipole interactions in the molecule CH2Cl2. Drawing out the Lewis structure, it appears as though the dipoles cancel each other out, yet the answer key says the molecule contains dipole-dipole interactions. I think it might ha...
Sun Nov 17, 2019 3:26 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Boiling Points
Replies: 7
Views: 124

### Re: Boiling Points

If a question asks which molecule has the highest boiling point, find out what type of bonding is within each molecule. The strongest are ionic bonds (ion-ion), then ion-dipoles, then hydrogen bonds, then dipole-dipoles, then LDF. The stronger the bond, the higher the boiling point.
Sun Nov 17, 2019 3:24 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Quick Run-Through
Replies: 2
Views: 37

### Re: Quick Run-Through

An example of an ion-ion interaction is NaCl, as this is ionic bonding (their charges cancel). An example of an ion-dipole interaction is when Na bonds to a water molecule, as Na is the ion and there are dipole interactions between the O and H in the water molecule. An example of a dipole-dipole int...
Sun Nov 10, 2019 12:13 am
Forum: Bond Lengths & Energies
Topic: test 2
Replies: 16
Views: 257

### test 2

test 2 isn't cumulative right? Is it only based on material covered after the midterm?
Sun Nov 10, 2019 12:09 am
Forum: Bond Lengths & Energies
Topic: Week 7 Homework
Replies: 15
Views: 317

### Re: Week 7 Homework

I'd recommend doing problems from the 3F section on the chemical bonds outline as those were not covered on the midterm :)
Sun Nov 10, 2019 12:01 am
Forum: Octet Exceptions
Topic: Reasoning for Octet Exception
Replies: 19
Views: 512

### Re: Reasoning for Octet Exception

As all these elements are located in period 3, they can have expanded octets through using their energetically accessible, low-lying d sub-shell for bonding. This is why period 2 elements cannot have an expanded octet, as they don't have access to the d sub-shell.
Sat Nov 09, 2019 11:56 pm
Forum: Lewis Structures
Topic: Lewis acids and bases?
Replies: 7
Views: 102

### Re: Lewis acids and bases?

Yes! Lewis acids accept electrons whereas lewis bases donate electrons. We will definitely elaborate more on them in the future weeks remaining in the quarter
Sat Nov 09, 2019 11:54 pm
Forum: Sigma & Pi Bonds
Topic: hybridization
Replies: 2
Views: 99

### Re: hybridization

Hybridization is a concept where atomic orbitals can fuse to form new, hybridized orbitals. Basically, it's an expansion of the valence bond theory, which assumes all bonds are localized bonds formed between two atoms due to each one donating an electron. In terms of determining hybridization, here'...
Fri Nov 01, 2019 8:50 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic/Covalent
Replies: 6
Views: 76

### Ionic/Covalent

How is it possible for ionic compounds to have covalent properties? I know it's possible, but I don't know how to explain the concept in a way that makes sense.
Fri Nov 01, 2019 8:48 pm
Forum: Lewis Structures
Topic: central atom
Replies: 16
Views: 1579

### Re: central atom

In addition to referring to the electronegativity, I would look at the compound to see which atom is more likely to form bonds. For example, carbon forms four, nitrogen three, oxygen two, etc.
Fri Nov 01, 2019 8:42 pm
Forum: Lewis Structures
Topic: Determining lowest energy lewis structure
Replies: 2
Views: 33

### Re: Determining lowest energy lewis structure

Personally, I like to draw out the Lewis structure with single bonds first, fulfilling the octet rule for the atoms if possible. Then I calculate formal charge: a quick way to do this is by drawing a circle around the atom (basically splitting the bonds in half) and counting how many electrons it ha...
Fri Nov 01, 2019 8:25 pm
Forum: Trends in The Periodic Table
Topic: Octet Rules
Replies: 4
Views: 54

### Octet Rules

What is the difference between an element that does not have to satisfy the octet rule, and an element that can have an extended octet? I think, I might be wrong, that all elements group 3 and below can have an extended octet?
Fri Nov 01, 2019 8:23 pm
Forum: Trends in The Periodic Table
Topic: electron affinity and electronegativity
Replies: 2
Views: 50

### Re: electron affinity and electronegativity

Electronegativity describes the tendency of an atom to attract a shared pair of electrons. Electron affinity, simply put, is how badly an element "wants" an electron to make it more stable. They can both be followed by the same trend: they increase going up groups and right across periods.
Sun Oct 27, 2019 8:52 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity on the Test
Replies: 3
Views: 36

### Re: Electron Affinity on the Test

I don't believe we have to do calculations however I'm not 100% sure. What he will most likely do is present us with several elements and ask which one has the highest or lowest electron affinity. So basically...interpreting/applying your knowledge of periodic trends.
Sun Oct 27, 2019 8:48 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configurations (3d-orbital and 4s-orbital)
Replies: 2
Views: 60

### Re: Electron Configurations (3d-orbital and 4s-orbital)

A half-full or completely full d sub-shell is more stable than a full 4s orbital. "Removing" the electron from the s sub-shell and placing it in the d sub-shell is actually when an electron becomes excited with more energy so it can move up a level.
Sun Oct 27, 2019 8:45 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Chromium and Copper
Replies: 5
Views: 67

### Re: Chromium and Copper

They are exceptions because a completely full or a half full d sub-level is more stable than a partially full d sub-level. To make the d sub-level more stable, an electron from the 4s orbital is excited/rises to the 3s orbital. Instead of 3d^4 or 3d^9, we excite an orbital to make 3d^5 of 3d^10.
Sun Oct 27, 2019 8:36 pm
Forum: Trends in The Periodic Table
Topic: F orbital
Replies: 3
Views: 53

### F orbital

How familiar with the f-orbital do we need to be for the midterm? Will we be doing electron configurations for elements that include the f orbital?
Sun Oct 27, 2019 8:34 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy
Replies: 4
Views: 72

### Re: Ionization Energy and Lewis Structures

Use periodic trends! The atom with the lowest ionization energy takes the least amount of energy to remove a valence electron from its outer shell. Ionization energy increases from left to right across a period and decreases going down a group. This is because a larger atomic radius means the valenc...
Sun Oct 27, 2019 8:25 pm
Forum: Trends in The Periodic Table
Topic: 1F.19
Replies: 1
Views: 37

### Re: 1F.19

Elements of the s-block have much lower ionization energies than p-block metals. Therefore, it doesn't take much energy for them to give away electrons, so s-block metals usually form cations. This tendency to form cations makes the s-block metals more reactive. Hope that helped :)
Sun Oct 20, 2019 5:07 pm
Forum: Properties of Electrons
Topic: Quantum numbers
Replies: 4
Views: 82

### Re: Quantum numbers

This is due to the Pauli-exclusion principle. Also, it's important to note that an orbital can only contain a maximum of 2 electrons, so the two electrons must have opposing spins.
Sun Oct 20, 2019 4:55 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework Problem 1A #3
Replies: 3
Views: 81

### Re: Homework Problem 1A #3

As frequency decreases, wavelength increases. As wavelength increases, the slope of each wave decreases as the waves appear less steep. Slope = extent of change, therefore the extent of change decreases. Also, it always helps me to draw it out :)
Sun Oct 20, 2019 4:32 pm
Forum: Properties of Light
Topic: N levels
Replies: 8
Views: 115

### Re: N levels

The n levels are principal energy levels that are very important to know in order to do Rydberg equation problems. The change in energy is the energy of the final level minus the energy of the initial, solved by substituting in the Rydberg equation. You use the quantum number of the energy level in ...
Sun Oct 20, 2019 4:24 pm
Forum: Properties of Light
Topic: Modules
Replies: 5
Views: 108

### Re: Modules

I'm not certain but you could always ask Dr. Lavelle after his lecture. A similar way to study is by using Khan Academy. There are videos on almost every topic we've covered and quizzes that correspond to them, just like Lavelle's modules.
Sun Oct 20, 2019 4:16 pm
Forum: Properties of Light
Topic: Balmer and Lyman series.
Replies: 2
Views: 82

### Re: Balmer and Lyman series.

The Lyman series requires the high energy of UV light. The Balmer series releases light in the visible region. Questions will assume you know this information when asking you to find the n levels (initial and final) of an electron. An example would be question 1A.15: In the ultraviolet spectrum of a...
Mon Oct 14, 2019 3:21 am
Forum: Properties of Electrons
Topic: Electron standing wave
Replies: 2
Views: 36

### Re: Electron standing wave

Standing waves appear to be vibrating vertically without traveling horizontally. Here is a great khanacademy page that explains them/provides pictures!
Mon Oct 14, 2019 3:14 am
Forum: Balancing Chemical Reactions
Topic: Determining the state of matter
Replies: 4
Views: 175

### Re: Determining the state of matter

I think it just comes with familiarizing yourself with the compounds, but for some of them you can assume like H20 being liquid or if the problem tells you H20 vapor, then a gas. Diatomic elements like nitrogen, oxygen, hydrogen, etc. will be gases at room temperature. Usually compounds with oxide (...
Mon Oct 14, 2019 3:05 am
Forum: Properties of Light
Topic: MidTerms and Finals
Replies: 11
Views: 146

### Re: MidTerms and Finals

The midterm is 2 hours long and the final is 3. Since discussions are only 50 minutes, I think they are altered to fit the allotted time to take the test during those weeks.
Mon Oct 14, 2019 3:01 am
Forum: Properties of Light
Topic: Variables and what they mean
Replies: 9
Views: 143

### Re: Variables and what they mean

The lamda is a letter of the Greek alphabet that is used to represent wavelength (it looks like a squiggly v), whereas the lowercase v stands for frequency.
Mon Oct 14, 2019 2:56 am
Forum: Properties of Light
Topic: Memorizing Values for Tests
Replies: 3
Views: 35

### Re: Memorizing Values for Tests

I'm not quite sure if we need to know those values by heart in Chem14A (I don't think we do) but they are very useful to know for the future! Plank's constant is 6.626 x 10^-34 J.s^-1 where J = m^2s^-2kg. Rydberg's constant is 1.097 x 10^7 m^-1. The speed of light (c) is equal to 299,792,458 m.s^-1.
Sun Oct 06, 2019 5:48 pm
Forum: Empirical & Molecular Formulas
Topic: Polyatomic ions
Replies: 2
Views: 78

### Re: Polyatomic ions

I don't think we have to know polytatomic ions on the test as I believe the formulas will be given in the problems. However, they are very important to know for the future of this class. Here's a video on how to remember the most common ones :)
Sun Oct 06, 2019 5:42 pm
Forum: Significant Figures
Topic: Sig Figs given in problem vs solution
Replies: 3
Views: 68

### Re: Sig Figs given in problem vs solution

Ideally, yes, your answer should have the same number of sig figs as the values given in the problem. However, I asked my TA if on test one they were looking for the correct amount of sig figs in our answers and he said not to worry too much about it. As long as you know the concept and your answer ...
Sun Oct 06, 2019 5:36 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Finding number of atoms, formula units and moles
Replies: 4
Views: 22793

### Re: Finding number of atoms, formula units and moles

Regarding part b, we multiply by Avogadro's number to convert the moles we have into formula units. Since formula units are representative of molecules, we use Avogadro's number in the conversion. 1 mole = 6.022 x 10^23 molecules, atoms, formula units
Sun Oct 06, 2019 5:25 pm
Forum: Balancing Chemical Reactions
Topic: Alternative to Guess and Check?
Replies: 5
Views: 82

### Re: Alternative to Guess and Check?

I'd recommend balancing the simplest formula/element last. Most of the time this is hydrogen or oxygen. Also, writing how many moles of each element you have on both the reactant and product side can keep you organized when balancing the equation. There isn't a definitive way to balance equations, b...
Sun Oct 06, 2019 5:16 pm
Forum: SI Units, Unit Conversions
Topic: Formula Units
Replies: 3
Views: 64

### Re: Formula Units

Formula units are essentially empirical formulas for ionic compounds. It's the lowest whole number ratio of ions in an ionic compound. Most of the time formula units represent molecules, therefore they can be calculated by using Avogadro's number in a stoichiometric conversion. Hope this helps :)