Search found 57 matches

by Sebastian Lee 1H
Fri Nov 15, 2019 3:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.5
Replies: 3
Views: 11

Re: 2E.5

Also to address your comment on H 2 O: H20 is based off the tetrahedral shape since it has 2 bonding pairs and 2 lone pairs (4 total regions of electron density). In a tetrahedral molecule, the angles are 109.5 degrees. When you replace two atoms for two lone pairs, this angle will be similar but ac...
by Sebastian Lee 1H
Fri Nov 15, 2019 3:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.5
Replies: 3
Views: 11

Re: 2E.5

Ok, so like you figure out, ClO 2 - has a lewis structure where a central chlorine is double bonded to oxygen atoms with a lone pair on the chlorine. Here we have 3 regions of electron density (2 bonding regions and one lone pair). A molecule with 3 regions of electron density will be based off the ...
by Sebastian Lee 1H
Fri Nov 15, 2019 3:05 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: polar/nonpolar
Replies: 2
Views: 9

Re: polar/nonpolar

Nonpolar molecules can have induced dipole-induced dipole (aka London dispersion) forces as well as dipole-induced dipole forces if in the presence of polar molecules. London forces arise when a temporary uneven distribution of electrons in any molecule give rise to a temporary partial charge which ...
by Sebastian Lee 1H
Fri Nov 15, 2019 2:53 pm
Forum: Bond Lengths & Energies
Topic: Bond lengths and lone pairs
Replies: 2
Views: 12

Re: Bond lengths and lone pairs

I think so. I believe that if an atom has more lone pairs it will have a longer and weaker bond with surrounding molecules that also have lone pairs. Since electrons repel each other, the lone pairs would want to be as far away as possible from other lone pairs on bonded atoms. In class, Dr. Lavelle...
by Sebastian Lee 1H
Fri Nov 15, 2019 2:48 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 Part c
Replies: 2
Views: 39

Re: 3F.5 Part c

Thank you! I talked to Dr. Lavelle and he mentioned that, like you said, the dipole moments mostly cancel out (not fully) which contributes to a relatively low polarity molecule. He also said that even though Flourine is highly electronegative, it is also pretty close to the Carbon since its atomic ...
by Sebastian Lee 1H
Fri Nov 15, 2019 2:45 pm
Forum: Administrative Questions and Class Announcements
Topic: Extra Credit?
Replies: 5
Views: 47

Re: Extra Credit?

Eileen Si 3H wrote:Test 2 should cover topics ranging from Lewis structures, intermolecular forces, and the VSEPR Model. Hopefully I'm not missing anything!


In lecture today, Dr. Lavelle also said that sigma and pi bonds will also be on the test. He will cover them first thing in Monday's lecture.
by Sebastian Lee 1H
Mon Nov 11, 2019 1:45 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 Part c
Replies: 2
Views: 39

3F.5 Part c

In Problem 3F.5 part c, it says that CHI 3 has stronger intermolecular forces than CHF 3 and will have a higher melting point. This difference is attributed to the difference in strength of induced dipole-induced dipole forces between the two molecules. I understand why CHI 3 has stronger London for...
by Sebastian Lee 1H
Tue Nov 05, 2019 10:38 pm
Forum: Photoelectric Effect
Topic: Light acts as a wave
Replies: 4
Views: 26

Re: Light acts as a wave

I'm pretty sure the photoelectric effect supports the particle/photon model of electromagnetic radiation because increasing the intensity of a low frequency light didn't eject electrons. It supports the theory of discrete, quantized packets of energy which each have energy dependent on frequency. In...
by Sebastian Lee 1H
Tue Nov 05, 2019 10:32 pm
Forum: Ionic & Covalent Bonds
Topic: Lattice Energy
Replies: 2
Views: 20

Re: Lattice Energy

by Sebastian Lee 1H
Tue Nov 05, 2019 10:30 pm
Forum: Lewis Structures
Topic: Exceptions to the Octet Rule Question
Replies: 5
Views: 28

Re: Exceptions to the Octet Rule Question

YES. Basically, any element in the 3rd row/period of the periodic table and beyond can have an expanded octet because they have access to the d orbital. For example, Xe (a noble gas) can make bonds and break the octet rule because it has free electron real estate in the 5d orbital.
by Sebastian Lee 1H
Tue Nov 05, 2019 10:27 pm
Forum: Quantum Numbers and The H-Atom
Topic: Clarification about Unique Quantum Numbers
Replies: 1
Views: 12

Re: Clarification about Unique Quantum Numbers

I believe so. Each orbital, of course, will have 2 electrons with different spin too (different quantum numbers).
by Sebastian Lee 1H
Tue Nov 05, 2019 10:25 pm
Forum: Octet Exceptions
Topic: Easy way to remember octet exceptions
Replies: 4
Views: 30

Re: Easy way to remember octet exceptions

Basically, if the element is in the 3rd row of the periodic table or beyond, it can have an expanded octet. For incomplete octets, it's H, He, Li, Be, B and the rest of the group 13 elements (like Al).
by Sebastian Lee 1H
Tue Nov 05, 2019 10:22 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Numbers Question
Replies: 2
Views: 11

Re: Quantum Numbers Question

If n=2: l can be l=0, 1 because l=0,...,n-1 If l=0: m l = 0 because m l = -l,...,l If l=1: m l = -1, 0, 1 So we can see how many m l numbers there are which correspond to each orbital. There is one 2s orbital (n=2, l=0) and there are three 2p orbitals (n=2, l=1) each one having a m l of -1, 0, or 1....
by Sebastian Lee 1H
Tue Nov 05, 2019 10:15 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Numbers Question
Replies: 2
Views: 18

Re: Quantum Numbers Question

Okay so if n=4: l=0, 1, 2, 3 For l=0: m l = 0 For l=1: m l = -1, 0, 1 For l=2: m l = -2, -1, 0, 1, 2 For l=3: m l = -3, -2, -1, 0, 1, 2, 3 For each orbital there can be two electrons (one with spin up (m s = +1/2) and one with spin down (m s = -1/2)). If we add up all the orbitals, there are 16. Sin...
by Sebastian Lee 1H
Tue Nov 05, 2019 10:09 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: polarizability/polarizing power and periodicity
Replies: 2
Views: 11

Re: polarizability/polarizing power and periodicity

I believe all these concepts are related. An anion will be more polarizable if it has a larger ionic radius and thus has a lower ionization energy/lower electron affinity. The effective nuclear charge is lower so the electrons are held less tightly and the electron cloud is more easily distorted to ...
by Sebastian Lee 1H
Tue Nov 05, 2019 10:02 pm
Forum: Electronegativity
Topic: Electronegativity Chart
Replies: 5
Views: 38

Re: Electronegativity Chart

I think you should definitely know the general trend that electronegativity increases as you go to the right across a period and up a group. This way you can roughly determine what kind of dipole moment may appear in a molecule. The only time I think we would need to have an electronegativity chart ...
by Sebastian Lee 1H
Tue Nov 05, 2019 9:57 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Determining which bonds are more polar
Replies: 4
Views: 25

Re: Determining which bonds are more polar

Mg-O is more polar than B-O because the electronegativity difference between Mg and O is higher than between B and O. I think you're mistaken in saying that Mg is a smaller radius than B, because I'm pretty sure that atomic radius increases as you go down and to the left of the periodic table. Mg ha...
by Sebastian Lee 1H
Sat Nov 02, 2019 11:24 pm
Forum: Octet Exceptions
Topic: Boron and Aluminum
Replies: 1
Views: 17

Re: Boron and Aluminum

From my understanding, since both Boron and Aluminum are in the 13th group on the periodic table, they only have 3 valence electrons. Since they have a relatively low electron affinity, they won't feasibly gain a complete octet through covalent bonding. However, they can be stable with 5 valence ele...
by Sebastian Lee 1H
Sat Nov 02, 2019 11:14 pm
Forum: Dipole Moments
Topic: Midterm
Replies: 8
Views: 59

Re: Midterm

YES. You will have to know about dipole moments caused by electronegativity in covalent bonds. What you won't need to know is the specific intermolecular forces like dipole-dipole or dipole-induced dipoole BUT you should understand why many molecules will have partial charges and a dipole moment.
by Sebastian Lee 1H
Sat Nov 02, 2019 11:11 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Midterm Q
Replies: 2
Views: 22

Re: Atomic Spectra Midterm Q

I don't think you'll need to memorize each specific color. Just know that visible light is from about 400-700nm and that ~400 is violet while ~700 is red light.
by Sebastian Lee 1H
Thu Oct 31, 2019 3:00 pm
Forum: Lewis Structures
Topic: HW Problem 2C.5
Replies: 1
Views: 28

Re: HW Problem 2C.5

A radical is a molecule in which one of the atoms has a single lone electron. If you draw the Lewis Dot Structure for a radical, you would be left with one dot or electron by itself, unpaired with any other electrons. So if you have drawn the correct structure with bonds and lone pairs but you have ...
by Sebastian Lee 1H
Thu Oct 31, 2019 11:11 am
Forum: Resonance Structures
Topic: C4H4
Replies: 2
Views: 17

Re: C4H4

If you arrange the carbon atoms in a line, I don't think they will have enough bonds to make an octet. With C 4 H 4 , each C atom is single bonded to one H, single bonded to another C, and double bonded to a different C. This gives each Carbon 4 bonds if put in a square configuration, satisfying the...
by Sebastian Lee 1H
Thu Oct 31, 2019 11:06 am
Forum: Electronegativity
Topic: Electronegativity vs Electron Affinity of Nitrogen
Replies: 3
Views: 12

Electronegativity vs Electron Affinity of Nitrogen

I noticed that Nitrogen has a quite high electronegativity value of 3.04 but has a very low electron affinity of almost 0. I understand that Nitrogen has such a low electron affinity because adding an electron to its stable half-full 2p subshell is actually energetically unfavorable. But why does Ni...
by Sebastian Lee 1H
Mon Oct 28, 2019 10:10 am
Forum: Octet Exceptions
Topic: Sharing more than 8 e-
Replies: 1
Views: 17

Re: Sharing more than 8 e-

Certain elements can have expanded valence shells, more than 8 electrons in their valence shell. I believe this can only happen with nonmetals in the 3rd row of the periodic table and down. This is because they can put electrons into the d subshell, even though the ground state atom doesn't have ele...
by Sebastian Lee 1H
Mon Oct 28, 2019 10:03 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 11
Views: 79

Re: Midterm

Check out this: https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

Yes, the midterm will be on Wednesday from 6-8pm. It will cover Fundamentals, Quantum World, and Chemical Bonds. The format will be 8 questions in 2 hours, free response like last test.
by Sebastian Lee 1H
Mon Oct 28, 2019 10:01 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 2
Views: 16

Re: Midterm

https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

8 questions in 2 hours. Probably multi-step free response.
by Sebastian Lee 1H
Mon Oct 28, 2019 10:00 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 5
Views: 55

Re: Midterm

https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

According to the info, it should cover Fundamentals, Quantum World, and Chemical Bonds.
by Sebastian Lee 1H
Mon Oct 28, 2019 9:57 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 2
Views: 35

Re: Midterm

https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

8 questions, likely free response like the first test
by Sebastian Lee 1H
Mon Oct 28, 2019 9:55 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm Time
Replies: 1
Views: 13

Re: Midterm Time

https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

Wednesday from 6-8 pm so not during class.
by Sebastian Lee 1H
Sat Oct 26, 2019 11:44 pm
Forum: Lewis Structures
Topic: Drawing a Lewis Structure
Replies: 2
Views: 19

Re: Drawing a Lewis Structure

Fluorine only needs to make one bond in order to reach a stable octet of valence electrons. So each fluorine will make a single bond with the bromine atom to become stable. This does indeed result in Br having 10 electrons in its valence shell (6 from the bonds and 4 from the 2 lone pairs). (Bromine...
by Sebastian Lee 1H
Thu Oct 24, 2019 3:42 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2A.5: What happens with s and d orbitals?
Replies: 2
Views: 17

Re: 2A.5: What happens with s and d orbitals?

Great question! So the ground state of normal Tl is [Xe] 4f 14 5d 10 6s 2 6p 1 . To form a cation, the outermost valence electrons of the atom will be removed. The outermost electrons are going to be the ones in the 6s and 6p subshells. So if we have Tl 3+ , we remove the 3 electrons from the 6s and...
by Sebastian Lee 1H
Wed Oct 23, 2019 8:48 pm
Forum: Trends in The Periodic Table
Topic: Effective Nuclear Charge
Replies: 5
Views: 37

Re: Effective Nuclear Charge

I believe effective nuclear charge actually describes how much attraction an electron feels from the positive nucleus. Basically, a valence electron in a multi-electron atom will have a lower effective nuclear charge (Z eff e) than an electron closer to the atom. This is because of the shielding eff...
by Sebastian Lee 1H
Wed Oct 23, 2019 8:40 pm
Forum: Lewis Structures
Topic: Valence e in d block
Replies: 5
Views: 21

Re: Valence e in d block

Yes I believe most d-block elements will only have the s-shell valence electrons of the energy level above the d. This is helpful to know when considering making cations from these metals. The electrons will be removed from the outermost shell which consists only of its highest energy s-shell electr...
by Sebastian Lee 1H
Wed Oct 23, 2019 8:31 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: General Terminology for Electron Configuration
Replies: 2
Views: 14

Re: General Terminology for Electron Configuration

The shell is described by the primary quantum number n. A shell refers to the general energy level and distance from the nucleus. The n=1 shell is the lowest energy level. The subshell is described by the angular orbital momentum quantum number l. A subshell refers to the general shape. If l=0, it's...
by Sebastian Lee 1H
Wed Oct 23, 2019 8:19 pm
Forum: Ionic & Covalent Bonds
Topic: Focus 2.B problem B9
Replies: 2
Views: 24

Re: Focus 2.B problem B9

Also, we know it'll have to be an ionic compound because it's between a metal that has a very low ionization energy and a nonmetal with a high ionization energy/high electron affinity.
by Sebastian Lee 1H
Wed Oct 23, 2019 8:17 pm
Forum: Ionic & Covalent Bonds
Topic: Focus 2.B problem B9
Replies: 2
Views: 24

Re: Focus 2.B problem B9

Because phosphorous is a non-metal in the p-block, we know it will form an anion in an ionic bond. P has 5 valence electrons (2s 2 2p 3 ). In order to reach the desired 8 valence electrons to become stable (octet rule), it must gain 3 electrons and become P 3- . Potassium is an alkali metal so it wi...
by Sebastian Lee 1H
Sat Oct 19, 2019 9:51 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration
Replies: 1
Views: 15

Re: Electron Configuration

Basically, when writing electron configurations you must write in order of lowest energy to highest energy. In K and Ca, the 4s subshell is of a slightly lower energy than the 3d subshell so electrons occupy that space first. However, when Z>20 (you enter the d-block), the 3d subshell actually shift...
by Sebastian Lee 1H
Sat Oct 19, 2019 9:47 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Which Element to Use in Electron Configurations
Replies: 5
Views: 25

Re: Which Element to Use in Electron Configurations

Typically you would use the last element with a full shell (typically a noble gas) to shorthand. The problem with using the last element is that it would be confusing when identifying the extra electron in your element. For example, if I was doing the configuration for Ca, it would be weird to say [...
by Sebastian Lee 1H
Sat Oct 19, 2019 9:41 pm
Forum: Properties of Light
Topic: 1A. 15
Replies: 3
Views: 25

Re: 1A. 15

Okay so we know that the energy of the light emitted is caused by the transition of the electron from one energy level to another. We can represent this as \Delta E = E_{final} - E_{initial} . We also know that, for hydrogen, the energy of a specific energy level is given by the equation E = -\frac{...
by Sebastian Lee 1H
Sat Oct 19, 2019 9:20 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Spin
Replies: 4
Views: 32

Re: Magnetic Spin

I think you should understand electron spin as it pertains to electron configurations of certain elements. For instance, the Pauli Exclusion Principle states that if 2 electrons are in the same orbital, they should have opposite spins (spin up and spin down). Hund's rule says that electrons in the s...
by Sebastian Lee 1H
Sat Oct 19, 2019 9:15 pm
Forum: Quantum Numbers and The H-Atom
Topic: Values of l
Replies: 2
Views: 34

Re: Values of l

I believe you are referring to the possible values of the magnetic quantum number, m l . m l can take on the values from -l to l as you were saying. Each of these corresponds to the specific orientation of the orbital on the axes. For example, if l=2, m l can be -2, -1, 0, 1, or 2. Each of these 5 n...
by Sebastian Lee 1H
Sat Oct 19, 2019 9:11 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shell, Subshell, Orbital Terminology
Replies: 8
Views: 68

Re: Shell, Subshell, Orbital Terminology

Yes, I believe that is correct! I also used to think that the subshells were "orbitals".
by Sebastian Lee 1H
Sat Oct 19, 2019 9:07 pm
Forum: Quantum Numbers and The H-Atom
Topic: Ml values
Replies: 2
Views: 22

Re: Ml values

M l is the magnetic quantum number for an electron orbital/state. It can take the values of numbers from -l to +l so if l=2 (d-subshell), m l can be -2, -1, 0, 1, or 2. These values relate to the orientation of the orbital around the nucleus, meaning what axes/planes it lies on. For example, for the...
by Sebastian Lee 1H
Tue Oct 15, 2019 11:47 am
Forum: *Shrodinger Equation
Topic: Schrodinger's Equation
Replies: 8
Views: 50

Re: Schrodinger's Equation

Is the Schrodinger equation typically used to find the wavefunction itself or the total energy (kinetic + potential) of the wavefunction? Do observations reveal the total energy and allow the wavefunction to be derived from it?
by Sebastian Lee 1H
Tue Oct 15, 2019 11:34 am
Forum: DeBroglie Equation
Topic: HW Question 1.B.15
Replies: 3
Views: 16

Re: HW Question 1.B.15

The mass of the electron is a constant that should be given on the constants and equations sheet. The mass of an electron is 9.109 x 10-31 kg. Using the deBroglie equation you can find the wavelength with Planck's constant, velocity, and mass.
by Sebastian Lee 1H
Sat Oct 12, 2019 10:31 am
Forum: Properties of Electrons
Topic: De Broglie Problems
Replies: 4
Views: 25

Re: De Broglie Problems

I believe Dr. Lavelle said during lecture that any object with less than 10^-15 m wavelength would be undetectable--it wouldn't show wave-like properties, just particle properties. For example, an electron with a very small mass should have a detectable wavelength, even if it's velocity is high. How...
by Sebastian Lee 1H
Wed Oct 09, 2019 10:03 pm
Forum: Properties of Light
Topic: Problem 1A.15 and the Rydberg formula
Replies: 3
Views: 37

Problem 1A.15 w/o Rydberg formula

Ok, after lecture today I understand that to find the energy levels we can use \lambda =\frac{c}{\nu } , \Delta E = h\nu , \Delta E = E(final)-E(initial) , and En=-\frac{hR}{n^2} to solve the problem. Using the wavelength to get frequency and then frequency to get change in energy, w...
by Sebastian Lee 1H
Tue Oct 08, 2019 11:03 pm
Forum: Properties of Light
Topic: Light intensity
Replies: 10
Views: 63

Re: Light intensity

The energy per photon is equal to Planck's constant times frequency of each photon. The threshold energy (or work function) is how much energy is required per photon to eject an electron from the metal. If the energy per photon equals the threshold energy, then an electron will be ejected from the m...
by Sebastian Lee 1H
Tue Oct 08, 2019 10:58 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: The relationship of precision between position and momentum
Replies: 3
Views: 32

Re: The relationship of precision between position and momentum

The Heisenberg uncertainty principle shows the complementarity of location and momentum. If one property is known to a precise extent, the other can't be known as well simultaneously. We know from the de Broglie equation that \lambda = \frac{h}{p} . If we know the precise momentum, we assume wave-li...
by Sebastian Lee 1H
Tue Oct 08, 2019 10:39 pm
Forum: SI Units, Unit Conversions
Topic: Will we have to know how to convert from Fahrenheit, Celsius, and Kelvin?
Replies: 4
Views: 52

Re: Will we have to know how to convert from Fahrenheit, Celsius, and Kelvin?

I doubt you would need to memorize the fahrenheit-celsius formulas as fahrenheit is rarely used in chemistry. However, I would suggest that you remember that Kelvin is Celsius + 273.15 (though I believe this is provided on the constants and equations sheet). This will probably be more relevant when ...
by Sebastian Lee 1H
Fri Oct 04, 2019 3:58 pm
Forum: Properties of Light
Topic: Problem 1A.15 and the Rydberg formula
Replies: 3
Views: 37

Problem 1A.15 and the Rydberg formula

1A.15: In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.66 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line. So I found the frequency of the emission to be 2.92 * 10 15 Hz usi...
by Sebastian Lee 1H
Thu Oct 03, 2019 8:40 pm
Forum: Molarity, Solutions, Dilutions
Topic: Homework Problem G17 Part B
Replies: 2
Views: 22

Re: Homework Problem G17 Part B

Yeah, the only difference is that in part a, you have anhydrous copper(ii) sulfate whereas in part b, you have copper(ii) sulfate pentahydrate. The 5H2O on the end means that there are water molecules in the crystalline structure of CuSO4 but are not totally bonded to the molecule. The only differen...
by Sebastian Lee 1H
Thu Oct 03, 2019 8:34 pm
Forum: Significant Figures
Topic: All students read this sig fig post [ENDORSED]
Replies: 115
Views: 10313

Re: All students read this sig fig post [ENDORSED]

melinak1 wrote:is there a consistent rule of how many sig figs there should be? or does it depends on what the problem is asking for?

The number of sig figs you need in your answer depends on how many sig figs are give in the numbers of the problem.
by Sebastian Lee 1H
Thu Oct 03, 2019 5:48 pm
Forum: Molarity, Solutions, Dilutions
Topic: Clarification for G17b ?
Replies: 4
Views: 25

Re: Clarification for G17b ?

To answer Ashley's question: The dot in CuSo4 • 5H2O signifies that the water (known as the water of hydration/crystallization) is bound to the copper(ii) sulfate in its crystalline framework. The water molecules can be evaporated away, leaving just the anhydrous salt. Note that the water can only b...
by Sebastian Lee 1H
Thu Oct 03, 2019 4:49 pm
Forum: Limiting Reactant Calculations
Topic: Homework Week 1
Replies: 18
Views: 133

Re: Homework Week 1

To satisfy the requirements, you only need to answer ANY 5 questions from the problem list and turn them in during tomorrow's lecture. HOWEVER, if you have the time and/or want extra practice, I would strongly suggest that you do more than the required 5 problems. Professor Lavelle states that he in...
by Sebastian Lee 1H
Wed Oct 02, 2019 11:54 pm
Forum: SI Units, Unit Conversions
Topic: Fundamentals Practice Problem E3
Replies: 3
Views: 61

Re: Fundamentals Practice Problem E3

You're absolutely correct! The gallium atoms have a third of the molar mass of the astatine atoms so you would need 3 times as many gallium atoms to balance out the astatine atoms. Conversely, the amount of astatine would be 1/3 the amount of gallium, so 9 atoms of gallium requires 3 atoms of astati...
by Sebastian Lee 1H
Wed Oct 02, 2019 9:30 am
Forum: Balancing Chemical Reactions
Topic: Balancing chemical reactions with polyatomic ions [ENDORSED]
Replies: 4
Views: 61

Re: Balancing chemical reactions with polyatomic ions [ENDORSED]

Hi Melivn, You can just write out each atom in the reaction. In some cases the polyatomic ion will appear in both the reactant and product; in this case, you can treat it as a whole unit. For example, 2AgN03 + CaCl2 -> 2AgCl + Ca(N03)2. Here the nitrate ion can be seen as a whole unit (2*1 units of ...

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