## Search found 31 matches

Sun Dec 09, 2018 12:14 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: homework problem 6B.1
Replies: 2
Views: 130

### homework problem 6B.1

The molar concentration of HCl in hydrochloric acid is reduced to 12% of its initial value by dilution. What is the difference in pH values of the two solutions?
Sat Dec 08, 2018 11:15 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 7th edition 9C.5
Replies: 1
Views: 111

### Re: 7th edition 9C.5

Yes, HN(CH2CH2NH2) is tridentate. It's easier to see when looking at the structure drawn out, but there are 3 N atoms each with a set of lone pairs that are ready to form a coordinate covalent bond. The ligand bends in such a way to where the N atoms are able to bind to the same metal atom.
Sat Dec 08, 2018 12:26 pm
Forum: Naming
Topic: Cation Naming
Replies: 2
Views: 138

### Re: Cation Naming

Yup! An anionic complex with an overall negative charge.
Sat Dec 08, 2018 12:00 pm
Forum: Identifying Acidic & Basic Salts
Topic: Polydentate v. Chelate
Replies: 2
Views: 271

### Re: Polydentate v. Chelate

You have the right idea. Polydentate means one ligand can bind to the same metal atom at different binding sites. The chelate is the complex that is produced when a polydentate ligand binds to a metal atom and forms a ring. Chelation is just this process, and the polydentate ligand can be referred t...
Fri Dec 07, 2018 3:34 pm
Forum: Ionic & Covalent Bonds
Topic: bond length
Replies: 3
Views: 262

### bond length

Why is the PF bond in PF3 longer than the NF bond in NF3? This is from homework problem 2.25
Thu Dec 06, 2018 12:05 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Net Dipole
Replies: 3
Views: 358

### Net Dipole

How does ClF3 have a dipole moment? Does it have to do with the lone pairs on the Cl molecule?
Wed Dec 05, 2018 10:50 pm
Forum: Identifying Acidic & Basic Salts
Topic: aqueous solutions of salts
Replies: 2
Views: 305

### aqueous solutions of salts

How do we decide whether aqueous solutions of salts are acidic, neutral, or basic? Could someone please explain how Ba(NO2)2 would be basic?
Thu Nov 29, 2018 9:08 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligand charge
Replies: 4
Views: 226

### Re: Ligand charge

Thank you Sam that was super helpful!
Tue Nov 27, 2018 10:18 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligand charge
Replies: 4
Views: 226

### Ligand charge

Lavelle said in class that we can use the charge of the ligands to figure out the oxidation number of the central atom. He used the example Fe(CN)6^4- with an oxidation number or 2+. How do we know the charge of the CN molecules?
Mon Nov 26, 2018 11:28 pm
Forum: Hybridization
Topic: s-character
Replies: 6
Views: 978

### s-character

What is the "s-character" of a hybridized atom?
Fri Nov 16, 2018 1:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.25 (7th ed)
Replies: 2
Views: 106

### Re: 2E.25 (7th ed)

But which is the correct way to arrange the atoms?
Fri Nov 16, 2018 1:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion Strength
Replies: 2
Views: 109

### Re: Repulsion Strength

The bonding electron pair shared in a sigma bond with an adjacent atom lies further from the central atom than a nonbonding (lone) pair of that atom, which is held close to its positively charged nucleus. Thus, repulsion from a lone pair is greater than repulsion from a bonding pair.
Fri Nov 16, 2018 1:48 pm
Forum: Hybridization
Topic: General definition/context
Replies: 2
Views: 135

### Re: General definition/context

Hybridization occurs because electrons in an atom or molecule are randomly dispersed, and sometimes happen to be gathered in one area. This causes dipole dispersion, and another dipole molecule interacts with these electrons making Van Der Waals forces. The atomic orbitals overlap (hybridization) to...
Sun Nov 11, 2018 11:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 4
Views: 155

### Re: Bond Angles

We represent molecules using 2D Lewis structures, but they really exist in 3D space. This means that the atoms can get father away from each other, going behind or coming in front of the central atom, which explains the larger bond angle of 109.5
Sun Nov 11, 2018 7:25 pm
Forum: Ionic & Covalent Bonds
Topic: 7th edition 2D.3
Replies: 2
Views: 122

### Re: 7th edition 2D.3

Professor Lavelle said that for a bond to be considered ionic, the difference in electronegativites of the 2 atoms should be at least 2. This isn't the case for BeBr2, so it's not ionic.
Wed Nov 07, 2018 10:12 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent or ionic?
Replies: 4
Views: 957

### Covalent or ionic?

Why isn't BeBr2 an ionic compound?
Fri Nov 02, 2018 4:21 pm
Forum: Ionic & Covalent Bonds
Topic: Non-polar and Polar Covalent Bonds
Replies: 3
Views: 188

### Re: Non-polar and Polar Covalent Bonds

A bond will be polar covalent if the 2 atoms have different electronegativities. In the case of C and H, they have similar enough electronegativities (I think theres a .3 difference) to be non polar covalent. C and H are the 2 main elements you need to know have similar electronegativities.
Fri Nov 02, 2018 1:43 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Numbers related to Orbitals
Replies: 4
Views: 183

### Re: Quantum Numbers related to Orbitals

Basically, elements on the left half of the periodic table will have +1/2, and elements on the right half will have -1/2. This is because on the left half of the table, the orbitals each have one electron in them, and once you get to the other half, the electrons begin to double up. Each element has...
Thu Nov 01, 2018 3:46 pm
Forum: Octet Exceptions
Topic: Octet Exceptions
Replies: 3
Views: 234

### Re: Octet Exceptions

Why doesn't the 13th column of the periodic table need an octet?
Thu Nov 01, 2018 3:27 pm
Forum: Octet Exceptions
Topic: Boron Trifluoride class example
Replies: 3
Views: 141

### Boron Trifluoride class example

When talking about Lewis acids and bases, Lavelle drew the Lewis structure for BF3 with Boron only having 6 electrons. He explained this was because making one of the B-F bonds a double bond would give F a + charge. Why would that be a bad thing?
Thu Nov 01, 2018 3:19 pm
Forum: Lewis Structures
Topic: Lewis Structure NO3-
Replies: 3
Views: 137

### Lewis Structure NO3-

In lecture, Dr. Lavelle drew out the Lewis structures for NO3- when explaining resonance. Nitrogen has 2 single bonds to Oxygen and one double bond to Oxygen, but I thought Nitrogen could only make 3 bonds because it has 5 valence electrons. Can someone please explain how this works? Can we just add...
Tue Oct 30, 2018 11:49 pm
Forum: Ionic & Covalent Bonds
Topic: Chemical Bonds 3.13
Replies: 1
Views: 113

### Re: Chemical Bonds 3.13

The electron configuration for each of these atoms is listed on the periodic table. So for (a) Zn, the electron configuration is [Ar] 3d10 4s2. To form a +1 ion, an electron will be taken from the outermost shell, which we get from the electron configuration. For Zn, an electron would be removed fro...
Thu Oct 25, 2018 7:40 pm
Forum: Einstein Equation
Topic: 1B.9 (7th edition)
Replies: 8
Views: 406

### Re: 1B.9 (7th edition)

Energy and intensity aren't the same in practice. You first find the total energy (32W*1J/s*2s=64J), then find the energy per photon using E=hc/lambda. Calculate the number of photons by dividing the total energy by the energy/photon, then convert this number to moles by dividing by Avogadro's numbe...
Thu Oct 25, 2018 5:38 pm
Forum: Photoelectric Effect
Topic: unit conversion hw Q 1.3
Replies: 7
Views: 190

### unit conversion hw Q 1.3

The question reads, "In each second, a certain lamp produces 2.4x10^21 photons with a wavelength of 633 nm. How much power (in watts) is produced as radiation at this wavelength?" I know how to solve this problem and that you start using E=hc/lambda, but do I need to convert the wavelength...
Thu Oct 25, 2018 4:11 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Question about H electron configuration
Replies: 3
Views: 161

### Re: Question about H electron configuration

We write electron configurations for the ground state, so yes it would be 1s1 for H and 1s2 for He. An excited H electron will pass all energy levels up to the one matching the energy of the photon, and then fall right back down to release the energy as light.
Sun Oct 14, 2018 12:24 am
Forum: SI Units, Unit Conversions
Topic: What Unit of Mass to Use?
Replies: 5
Views: 587

### Re: What Unit of Mass to Use?

Yes, the SI unit for mass is kg. However, in many problems, we're dealing with amounts of samples that make most sense to express in g. In a realistic lab setting we would say 2.4 g instead of 2.4 x 10^-3 kg. So if a problem gives units in g, it's probably best to use g in your answer
Sun Oct 14, 2018 12:06 am
Forum: Trends in The Periodic Table
Topic: problem 1.13
Replies: 3
Views: 87

### problem 1.13

why is the ionization energy for O lower than that of N or F when ionization energy usually increases from left to right across the periodic table?
Sat Oct 13, 2018 11:54 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals problem 1E.11
Replies: 2
Views: 44

### Orbitals problem 1E.11

Can someone please explain how to write the ground state electron configuration of atoms: sodium, silicon, chlorine, and rubidium?
Sat Oct 06, 2018 2:55 am
Forum: Properties of Light
Topic: Classical vs Quantum
Replies: 2
Views: 131

### Re: Classical vs Quantum

classical mechanics explains behavior of large objects, while quantum mechanics describes very small objects, such as subatomic particles. In his example during class, he described water in both ways. In a classical sense, when we pour water from a can, it comes out as one continuous stream. However...
Sat Oct 06, 2018 2:45 am
Forum: Empirical & Molecular Formulas
Topic: Question L.39, Reaction Stoichiometry
Replies: 1
Views: 109

### Question L.39, Reaction Stoichiometry

Could I get a step by step solution to this problem? I'm not sure where to start. "A 1.50 g sample of metallic tin was placed in a 26.45 g crucible and heated until all the tin had reacted with the O in air to form an oxide. The crucible and product together were found to weigh 28.35 g. a. What...
Thu Oct 04, 2018 2:57 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Molar Masses
Replies: 9
Views: 252

### Molar Masses

Will we need to know the molar masses of elements for tests? I know the basics (O,C,H,N), but am wondering if I should try to memorize any others or if we'll be given a periodic table.