Search found 30 matches

by Hanlin Zhu 4G
Sat Dec 08, 2018 9:30 pm
Forum: Amphoteric Compounds
Topic: Amphiprotic vs. Amphoteric
Replies: 7
Views: 322

Re: Amphiprotic vs. Amphoteric

Not all Amphoteric substances are amphiprotic. For example, Al2O3 is amphoteric but not amphiprotic.
by Hanlin Zhu 4G
Thu Dec 06, 2018 8:10 pm
Forum: Naming
Topic: Chemical Formulas
Replies: 2
Views: 62

Re: Chemical Formulas

I think transition metals are almost always inside the brackets of a coordination compound.
by Hanlin Zhu 4G
Thu Dec 06, 2018 8:06 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination number
Replies: 1
Views: 69

Coordination number

Does anyone know how to find the coordination number for complexes with polydentate ligands? For example, I know EDTA4- is a hexadentate and having octahedral structures when it binds to a metal cation, but I don't know if a complex such as [Fe(EDTA)]2- should be consider as having coordination numb...
by Hanlin Zhu 4G
Thu Dec 06, 2018 7:52 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: H30+ and H+
Replies: 4
Views: 95

Re: H30+ and H+

When HCl is deprotonated, we often write it as H+ and Cl- for simplicity. However, H+ does not exist in form of a single proton, it will bind with water and form H3O*. So it is a actually transfer of proton.
by Hanlin Zhu 4G
Thu Dec 06, 2018 11:55 am
Forum: Bronsted Acids & Bases
Topic: Distinguishing bronsted acids vs bases
Replies: 3
Views: 110

Re: Distinguishing bronsted acids vs bases

In the example you give, HNO2 + HPO4 ^2- <=> NO2^- + H2PO4^-, HNO2 is the acid, because it loses (donates) a proton to HPO4^2-. HPO4 ^2- is the base, because it accepts the H+ from HNO2. You can distinguish bronsted acids and bases by finding their roles in proton transfer.
by Hanlin Zhu 4G
Sun Dec 02, 2018 10:12 pm
Forum: Dipole Moments
Topic: Strength of intramolecular forces due to polarity
Replies: 5
Views: 150

Re: Strength of intramolecular forces due to polarity

Between two polar molecules, such as HF and HF, there are dipole-diploe interactions going on. It is a slightly greater intermolecular attractive force than the dispersion force between two non-polar molecules.
by Hanlin Zhu 4G
Sun Dec 02, 2018 10:04 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: calcium
Replies: 2
Views: 54

Re: calcium

Maybe calcium oxide is called a "quicklime" just because it is very reactive.
by Hanlin Zhu 4G
Sun Dec 02, 2018 10:00 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted Acid vs Lewis Acid
Replies: 2
Views: 91

Re: Bronsted Acid vs Lewis Acid

A Bronsted acid is a proton (H+ ion) donor, and a Bronsted base is a proton acceptor. A Lewis acid is an electron acceptor, and a base is an electron donor. You can apply the two definitions to a single molecule. For example, ammonia is a proton acceptor, and it is also a electron donor.
by Hanlin Zhu 4G
Sun Nov 25, 2018 9:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 3
Replies: 38
Views: 755

Re: Test 3

I think the comparative strength of ion-ion, ion-dipole, dipole-dipole, dipole-induced dipole, and dispersion interactions may also on the test. Also I remember there are specific factors affecting induced dipole-induced dipole forces.
by Hanlin Zhu 4G
Sun Nov 25, 2018 9:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 3
Replies: 38
Views: 755

Re: Test 3

I think different intermolecular interactions is also included in the test.
by Hanlin Zhu 4G
Sun Nov 25, 2018 9:14 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: sigma and pi bonds
Replies: 4
Views: 102

Re: sigma and pi bonds

A sigma bond is in direction along the bond axis, like a stick connecting two balls, so atoms can rotate freely. The pi bonds is formed above and below the sigma bond, so it is only stable in one orientation and cannot rotate.
by Hanlin Zhu 4G
Sun Nov 18, 2018 12:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Shape
Replies: 10
Views: 250

Re: Determining Shape

It is hard to know the number of bonding pairs and lone pairs just by looking at the chemical formula. I think to be safe we have to draw the lewis structure.
by Hanlin Zhu 4G
Sun Nov 18, 2018 12:06 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle for VSEPR Name AX2E3 [ENDORSED]
Replies: 1
Views: 80

Re: Bond Angle for VSEPR Name AX2E3 [ENDORSED]

I think AX2E3 is linear because the repulsion force of equatorial orbitals pushes the bonding pairs to the vertical axis. If the bond angle is less than 180 degree, the bonding pairs actually gets closer to the lone pairs, which would not happen.
by Hanlin Zhu 4G
Sun Nov 18, 2018 11:57 am
Forum: Determining Molecular Shape (VSEPR)
Topic: No central atom
Replies: 7
Views: 157

Re: No central atom

I think we can think of the two nitrogen atom separately. Each of the nitrogen atom has a formula AX3N1 and a trigonal pyramidal shape.
by Hanlin Zhu 4G
Fri Nov 09, 2018 10:28 am
Forum: SI Units, Unit Conversions
Topic: Angstrom
Replies: 5
Views: 397

Re: Angstrom

It is convenient to use when measuring bond lengths, but it is not a IS unit.
by Hanlin Zhu 4G
Fri Nov 09, 2018 10:25 am
Forum: Bond Lengths & Energies
Topic: Dipole interaction
Replies: 3
Views: 94

Re: Dipole interaction

Dipole-dipole interactions take place between two polar molecules, such as HF and HF. Because F is more electronegative, there is a slight negative charge on the F end and a slight positive charge on the H end. The attraction between the positive end of one molecule and the negative end of another m...
by Hanlin Zhu 4G
Fri Nov 09, 2018 9:55 am
Forum: Dipole Moments
Topic: Dipole induced dipole
Replies: 3
Views: 83

Re: Dipole induced dipole

HCl is a polar molecule. When the Cl end comes close to a non-polar molecule N2, HCl repels the electron density of one end of N2, making that end slightly positive. This is an example of a dipole-induced dipole interaction.
by Hanlin Zhu 4G
Fri Nov 09, 2018 9:48 am
Forum: Dipole Moments
Topic: HCl
Replies: 6
Views: 113

Re: HCl

HCl has a permanent dipole moment because of its polarity. Cl is more electronegative, so Cl side always has a slight negative charge.
by Hanlin Zhu 4G
Sat Nov 03, 2018 12:12 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Node
Replies: 2
Views: 119

Re: Node

A wave function node occurs at points where the wave function psi is zero and changes signs. When psi=0, psi^2=0. Because psi^2 represents the probability density of electron, an electron has zero probability of being located at a node.
by Hanlin Zhu 4G
Sat Nov 03, 2018 12:07 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shells, Subshells, Orbitals
Replies: 4
Views: 331

Re: Shells, Subshells, Orbitals

Shells indicates the energy of the electrons and are specified by the principal quantum number n. There are k different subshells contained in a given shell with n value= k. For example, there are only one subshell in the n=1 level. There are two subshells in the n=2 level. Subshells are related to ...
by Hanlin Zhu 4G
Sat Oct 27, 2018 3:13 pm
Forum: Trends in The Periodic Table
Topic: Atomic Radius
Replies: 8
Views: 158

Re: Atomic Radius

I think knowing the general trends and being able to compare between two atoms given a periodic table is needed. We don't need to memorize the specific values.
by Hanlin Zhu 4G
Sat Oct 27, 2018 3:07 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Ml Meaning
Replies: 3
Views: 94

Re: Ml Meaning

ml is the magnetic quantum number, it specifies the individual orbitals within a subshell and indicates orientations. There are always 2l+1 different values of ml for a given value of l.
by Hanlin Zhu 4G
Sat Oct 27, 2018 2:59 pm
Forum: Quantum Numbers and The H-Atom
Topic: Orbitals
Replies: 4
Views: 121

Re: Orbitals

the outermost shell refers to the principal quantum number n and the energy level. For example, the number of electrons present in the outermost shell of a carbon atom is 4. (2s2, 2p2)
by Hanlin Zhu 4G
Mon Oct 22, 2018 10:56 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Significance of XYZ to PDF orbitals
Replies: 6
Views: 160

Re: Significance of XYZ to PDF orbitals

I agree with you. I think they are used mainly to denote the orientations of the lobes.
by Hanlin Zhu 4G
Mon Oct 22, 2018 10:51 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Formula confusion
Replies: 5
Views: 72

Re: Formula confusion

They are different but related. In the Heisenberg equation, the constant you mentioned that has the value 1.05457 x 10^-34 is actually not h. It is "h bar", which means h/2pi.
by Hanlin Zhu 4G
Mon Oct 22, 2018 10:47 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E.13 7th Edition
Replies: 3
Views: 62

Re: 1E.13 7th Edition

I think it is because a subshell is more stable if it gets half full or full. So when the d subshell is just one away from filled up it gets an electron from the s shell. It is similar to copper.
by Hanlin Zhu 4G
Wed Oct 17, 2018 8:37 am
Forum: Photoelectric Effect
Topic: Module Question 29 (Part B)
Replies: 4
Views: 118

Re: Module Question 29 (Part B)

I think the reason we have to divide it by the Avogadro constant is that the energy is given in kJ/mol. You need to solve for the energy of an atom.
by Hanlin Zhu 4G
Wed Oct 17, 2018 8:22 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Wavelengths
Replies: 5
Views: 131

Re: Wavelengths

I think wavelength should be a positive value. It is a measure of length rather than displacement.
by Hanlin Zhu 4G
Wed Oct 17, 2018 8:18 am
Forum: Photoelectric Effect
Topic: Post Module Assessment #25
Replies: 2
Views: 79

Re: Post Module Assessment #25

I think it might be D, because E=hv=hc/λ is connecting v, the frequency, with the energy of the photon.
by Hanlin Zhu 4G
Sat Oct 06, 2018 9:23 pm
Forum: Molarity, Solutions, Dilutions
Topic: dilutions? [ENDORSED]
Replies: 5
Views: 135

Re: dilutions? [ENDORSED]

The exact steps may vary depends on the types of values are given. The key concept is that when diluting a solution, the moles of solute remain the same. The moles of solute = M initial × V initial = M final × V final. So it might be helpful to first think about which of those quantities were given,...

Go to advanced search