Search found 35 matches

by Jeffrey Xiao 4A
Sun Dec 09, 2018 3:34 pm
Forum: Properties of Light
Topic: Snail velocity final problem
Replies: 3
Views: 2117

Re: Snail velocity final problem

Set KEsnail=Ephoton
so .5mv^2=pc then solve for v
by Jeffrey Xiao 4A
Fri Dec 07, 2018 8:11 pm
Forum: General Science Questions
Topic: PH3 or NH3
Replies: 2
Views: 416

Re: PH3 or NH3

NH3 because it can form hydrogen bonding while PH3 can't so NH3 will have the strongest intermolecular forces which means its boiling point will be highest
by Jeffrey Xiao 4A
Fri Dec 07, 2018 8:09 pm
Forum: General Science Questions
Topic: what determines boiling point
Replies: 2
Views: 258

Re: what determines boiling point

Hydrogen bonding because hydrogen bonding is the strongest intermolecular force which means the boiling point will be highest in a molecule with hydrogen bonding (For example: H20 has a boiling point of 100 degrees due to its hydrogen bonding capabilities)
by Jeffrey Xiao 4A
Sat Dec 01, 2018 7:10 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordinate Covalent Bonds
Replies: 1
Views: 33

Re: Coordinate Covalent Bonds

When an atom provides two electrons in a bond instead of only providing one as in normal covalent bonds, for example, NH3 is a compound with 3 bonded atoms and a set of lone pairs around the central atom, and when it becomes NH4, the set of lone pairs in NH3 are both used for the bond between the N ...
by Jeffrey Xiao 4A
Sat Dec 01, 2018 7:07 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: oxidation numbers for ligands
Replies: 2
Views: 70

Re: oxidation numbers for ligands

Well, oxidation number can be calculated from the charges of the ligands and the overall charge of the coordinate compound, Example: [Fe(NCS)(OH2)5]2+ ,OH2 is neutral so it is not included in the calculations, there is one NCS which is an anionic ligand with -1 charge so this means the iron metal mu...
by Jeffrey Xiao 4A
Wed Nov 28, 2018 11:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Angular Shape
Replies: 3
Views: 95

Re: Angular Shape

Slightly less because lone pairs result in a greater repulsion than regular bonds since lone pairs.
by Jeffrey Xiao 4A
Wed Nov 28, 2018 10:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: SnCl2
Replies: 2
Views: 283

Re: SnCl2

Sn wants to be in the most stable state which is when formal charge is equal to 0. With 18 total valence electrons in the structure, and with 16 valence electrons being taken up by the two Chlorines with 3 lone pairs around each and 1 single bond linking each Cl to Sn thanks to the fact that Chlorin...
by Jeffrey Xiao 4A
Wed Nov 28, 2018 10:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: How to identify polarity
Replies: 2
Views: 73

Re: How to identify polarity

Usually lone pairs make the molecule polar but there are exceptions with the linear AX2E3 and square planar AX4E2 where the molecules are nonpolar because dipole moments cancel regardless of the lone pairs, Otherwise, all the shapes with no lone pairs are nonpolar (tetrahedral, trigonal planar, octa...
by Jeffrey Xiao 4A
Wed Nov 21, 2018 9:33 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Homework
Replies: 2
Views: 121

Re: Homework

For part b) BH3 when you draw the lewis structure the B is the central atom bonded to 3 hydrogen atoms which means there are 3 regions of electron density which correlates to sp2 since there will be one hybridized orbital (1 s +2 p=3 total hybridized orbitals) for each bond.
by Jeffrey Xiao 4A
Wed Nov 21, 2018 9:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: CH 4 4.19 HW 6TH EDITION
Replies: 2
Views: 76

Re: CH 4 4.19 HW 6TH EDITION

For these you just draw the lewis structures and from the lewis structures you determine the shapes based on lone pairs and bonds around the central atom and from the shape you can estimate the bond angle For example, for part a) S2O3 2- has a central S atom bonded to the 4 other atoms with no lone ...
by Jeffrey Xiao 4A
Wed Nov 21, 2018 9:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: HW 6TH EDITION 4.45
Replies: 1
Views: 34

Re: HW 6TH EDITION 4.45

Well, first you would draw the Lewis structure of CH2O then count number of electron densities around central atom which should be 3 (two C-H single bonds and one double bond between C and O). As a result, hybrid orbitals would be sp2 since there are three electron densities, and then you would figu...
by Jeffrey Xiao 4A
Fri Nov 16, 2018 12:00 am
Forum: Electronegativity
Topic: noble gases
Replies: 2
Views: 86

Re: noble gases

Since higher electronegativity means that the element will have a stronger ability to attract electrons, noble gases have low electronegativity because they have a complete octet meaning they do not want to attract electrons
by Jeffrey Xiao 4A
Thu Nov 15, 2018 10:59 pm
Forum: Ionic & Covalent Bonds
Topic: H bonds and melting points
Replies: 4
Views: 134

Re: H bonds and melting points

Because hydrogen bonding is the strongest form of an intermolecular force which means it will be harder to break that bond by melting or boiling a molecule so the points will be higher
by Jeffrey Xiao 4A
Thu Nov 15, 2018 10:57 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shapes
Replies: 3
Views: 96

Re: Molecular Shapes

Tetrahedral structure is where the central atom has just 4 bonded atoms while seesaw shape is where the central atom has 4 bonded atoms and one lone pair.
by Jeffrey Xiao 4A
Thu Nov 08, 2018 7:08 pm
Forum: Octet Exceptions
Topic: Octet vs formal charge
Replies: 16
Views: 643

Re: Octet vs formal charge

Formal charge of zero because there are octet exceptions such as PCl5 or BH3 which means they won't have a complete octet but their formal charge will be zero instead so formal charge closest to zero should be the most important factor as complete octets are not always necessary.
by Jeffrey Xiao 4A
Thu Nov 08, 2018 7:05 pm
Forum: Lewis Structures
Topic: Electron configuration
Replies: 2
Views: 81

Re: Electron configuration

Since it has 2 electrons in its 5s shell, those 2 valence electrons are most likely to be removed to make sure cadmium has a complete octet which is why cadmium's most likely charge is +2.
by Jeffrey Xiao 4A
Thu Nov 08, 2018 7:04 pm
Forum: Resonance Structures
Topic: Dominant resonance structure
Replies: 4
Views: 85

Re: Dominant resonance structure

The dominant resonance structure is the one with formal charge closest to zero for the most stable structure.
by Jeffrey Xiao 4A
Thu Nov 01, 2018 8:06 pm
Forum: Resonance Structures
Topic: Most Stable Configuration
Replies: 11
Views: 268

Re: Most Stable Configuration

It is most stable if the formal charge of all the elements in the neutral compound are closest to 0, V-(L+S/2).
by Jeffrey Xiao 4A
Thu Nov 01, 2018 7:59 pm
Forum: Ionic & Covalent Bonds
Topic: 2A.15 (7th Ed)
Replies: 1
Views: 59

Re: 2A.15 (7th Ed)

Well, looking at a periodic table shows tellurium is two groups away from the noble gas of Xenon so theoretically, the most likely charge for Te should be Te2- since it will want to gain 2 electrons to complete its octet to be like Xenon.
by Jeffrey Xiao 4A
Wed Oct 31, 2018 2:24 am
Forum: Lewis Structures
Topic: Lewis Structures
Replies: 2
Views: 59

Re: Lewis Structures

Lines are for bonded electrons (electrons being shared between atoms) while dots are for lone pair electrons in which the valence electrons are not being shared with another atom.
by Jeffrey Xiao 4A
Sun Oct 28, 2018 2:27 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework problem 2A.23 (7th edition) [ENDORSED]
Replies: 1
Views: 77

Re: Homework problem 2A.23 (7th edition) [ENDORSED]

Expected charge refers to what the element's charge should theoretically be based on completing the octet of valence electrons. For a), since magnesium has 2 electrons in the s subshell, magnesium is two electron removals away from a complete octet so Mg2+ is the expected charge for magnesium and al...
by Jeffrey Xiao 4A
Thu Oct 25, 2018 8:59 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ionization Energy
Replies: 3
Views: 92

Re: Ionization Energy

Yeah, they have low ionization energy since they only need to remove one or two electrons to complete an octet which means they will be very reactive as they want a complete octet like the noble gases do.
by Jeffrey Xiao 4A
Thu Oct 25, 2018 8:56 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Meaning of Z
Replies: 5
Views: 136

Re: Meaning of Z

Z refers to the atomic number since there must be the same amount of electrons as the number of protons in a neutral element.
by Jeffrey Xiao 4A
Wed Oct 24, 2018 11:51 pm
Forum: Photoelectric Effect
Topic: Example 1.5 Part C in 6th Edition
Replies: 1
Views: 100

Re: Example 1.5 Part C in 6th Edition

Since wavelength and frequency are inversely related, the longest wavelength possible corresponds to the lowest frequency possible to eject an electron, and since the equation for photoelectric effect is Ek=hv - work function, the lowest frequency that ejects an electron is when hv-work function=0 s...
by Jeffrey Xiao 4A
Wed Oct 17, 2018 3:21 pm
Forum: Einstein Equation
Topic: 7th Edition 1B.5
Replies: 1
Views: 53

Re: 7th Edition 1B.5

1 keV=1.602 x 10^(-16) J
so 140.511 keV x 1.6022 x 10^(-16) J/keV= 2.25127 x 10^(-14) J
by Jeffrey Xiao 4A
Wed Oct 17, 2018 12:00 am
Forum: Properties of Light
Topic: calculating wavelength
Replies: 10
Views: 416

Re: calculating wavelength

De Broglie equation is h/mv where v (velocity) is not c so the de Broglie equation can be used when the speed of the particle is not at the speed of light whereas c=hv is mainly used for light calculations.
by Jeffrey Xiao 4A
Tue Oct 16, 2018 11:49 pm
Forum: Properties of Electrons
Topic: electrons
Replies: 3
Views: 103

Re: electrons

Electrons have wavelike properties because of the diffraction that occurs when electrons go through slits and the waves experience constructive (Peaks line up) and destructive interference (Peaks and troughs line up).
by Jeffrey Xiao 4A
Sun Oct 14, 2018 1:12 am
Forum: *Black Body Radiation
Topic: Stefan-Boltzmann and Wien's law
Replies: 2
Views: 372

Re: Stefan-Boltzmann and Wien's law

Boltzmann's law is when total intensity is proportional to T^4 while Wien's law is when T is inversely proportional to wavelength of maximum intensity so you use Wein's law for cases involving wavelength whereas Boltzmann's law is used when only total intensity is involved and not wavelength.
by Jeffrey Xiao 4A
Thu Oct 11, 2018 7:32 pm
Forum: Properties of Light
Topic: Homework for Week 2 [ENDORSED]
Replies: 3
Views: 91

Re: Homework for Week 2 [ENDORSED]

Lavelle said in lecture that the homework selection is flexible so yes you can turn in questions from the fundamentals for week 2 as someone asked your same question in my lecture.
by Jeffrey Xiao 4A
Thu Oct 11, 2018 7:30 pm
Forum: Molarity, Solutions, Dilutions
Topic: G.21
Replies: 2
Views: 280

Re: G.21

For part a) convert .500g of KCl to moles, convert .500g of K2S to moles then multiply the result by 2 since there are two potassium ions in that compound, and convert .500g of k3Po4 to moles then multiply the result by 3 because there are 3 potassium ions in that solution Finally, after all the con...
by Jeffrey Xiao 4A
Thu Oct 11, 2018 7:04 pm
Forum: Empirical & Molecular Formulas
Topic: Rounding for limiting reactants
Replies: 5
Views: 160

Re: Rounding for limiting reactants

Well it is much closer to 7.33 than 7 so I would round to 7.33 and then multiply it by 3 to get a whole number.
by Jeffrey Xiao 4A
Tue Oct 02, 2018 4:11 pm
Forum: Empirical & Molecular Formulas
Topic: Metal Hydroxides and sulfides
Replies: 2
Views: 105

Re: Metal Hydroxides and sulfides

For that problem, just find the molar mass of (OH)2 which is ~34.014 g/mol, then subtract that number from 74.10 g/mol (the total molar mass of the metal hydroxide) to find the molar mass of the metal. Then using a periodic table, find which element has the molar mass found previously which should b...
by Jeffrey Xiao 4A
Tue Oct 02, 2018 3:34 pm
Forum: Balancing Chemical Reactions
Topic: Net number of molecules
Replies: 3
Views: 93

Re: Net number of molecules

Stoichiometric coefficients represent number of moles so in a balanced chemical equation, to find net moles, subtract total number of moles of molecules from reactant side from the total number of moles of molecules from product side For example: From the Balancing Chemical Equations assessment modu...
by Jeffrey Xiao 4A
Tue Oct 02, 2018 2:37 pm
Forum: Empirical & Molecular Formulas
Topic: Rounding
Replies: 6
Views: 193

Re: Rounding

.38 is extremely close to .4 so I thought of 2.38 as 2.4 then to turn 2.4 into a whole number you multiply it by 5 so 2.4(5) is 12
Ratio is then 5:12:5 since 5(1:2.38:1)~ 5:12:5.

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