Search found 55 matches

by SGonzales_3L
Fri Dec 06, 2019 5:56 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa and Ka
Replies: 9
Views: 150

Re: pKa and Ka

In response to the previous post, I believe a lower pKa and larger Ka are actually representative of a strong acid. A higher Ka value is indicative of a larger concentration of hydronium (H3O+) ions. Oops, yes that is my bad. I've edited my comments so they should be correct now. But yes, a stronge...
by SGonzales_3L
Fri Dec 06, 2019 11:23 am
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Determining relative strengths of bases (6C 17)
Replies: 1
Views: 71

Re: Determining relative strengths of bases (6C 17)

Yes, you're right. BrO - is the stronger base. Looking at charge is one way of figuring out which is a stronger acid/base. It might help to also look at bond lengths--for the halogen acids, the longer the bond length, the stronger the acid. Strong acids also have stable conjugate bases so it is a go...
by SGonzales_3L
Fri Dec 06, 2019 11:19 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa and Ka
Replies: 9
Views: 150

Re: pKa and Ka

One thing to know that Dr. Lavelle mentioned in class is that if a pKa value is given it is highly likely that that acid is a weak acid. Strong acids strongly favor the products and, thus, have an astronomically large pKa. Does that mean strong acids have a high conc of H+? Yes, strong acids dissoc...
by SGonzales_3L
Fri Dec 06, 2019 11:15 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HW 6D.11.
Replies: 1
Views: 27

Re: HW 6D.11.

First of all, look at the ions that form each of the compounds. For example, NH 4 Br is formed by NH 4 + and Br - . We know that the conjugate bases and acids of strong acids and bases do not affect the pH. HBr is a strong acid due to how easily it loses its H, so Br - does not affect the pH. NH 4 ...
by SGonzales_3L
Fri Dec 06, 2019 11:09 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa and Ka
Replies: 9
Views: 150

Re: pKa and Ka

One thing to know that Dr. Lavelle mentioned in class is that if a pKa value is given it is highly likely that that acid is a weak acid. Strong acids strongly favor the products and, thus, have an astronomically large Ka.
by SGonzales_3L
Thu Nov 28, 2019 8:36 pm
Forum: Bronsted Acids & Bases
Topic: 6A9
Replies: 2
Views: 44

Re: 6A9

You know that a Bronsted Acid is a proton donor and a Bronsted Base is a proton acceptor. Go through each of the chemical equations and see if you can identify if one of the compounds is donating a proton to another. For example in a), NH 4 + donates a proton to create H 3 O + . In this equation, H ...
by SGonzales_3L
Thu Nov 28, 2019 8:31 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Constant K(a)
Replies: 4
Views: 50

Re: Constant K(a)

I believe Dr. Lavelle said that we wouldn't be calculating K A in this class, but it is good to understand its significance. K A is used to calculate the strength of weak acids. There is no K A for strong acids since it would be an astronomically large number. In determining which acid is stronger w...
by SGonzales_3L
Thu Nov 28, 2019 8:28 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination number of [Co(Ox)3]3-
Replies: 2
Views: 24

Re: Coordination number of [Co(Ox)3]3-

Yes, ox is an abbreviation for the oxalate anion. The whole coordination compound looks like this: https://s3mn.mnimgs.com/img/shared/ck-files/ck_587c9fd80fefb.png

The Co ion can only bond to the oxygens on one end of the oxalate anions, so the coordination number is 6.
by SGonzales_3L
Thu Nov 28, 2019 8:19 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted Acid and base
Replies: 8
Views: 82

Re: Bronsted Acid and base

A Bronsted Base is a proton acceptor. In contrast, a Bronsted Acid is a proton donor.
by SGonzales_3L
Thu Nov 28, 2019 8:17 pm
Forum: Hybridization
Topic: 2F.7
Replies: 1
Views: 26

Re: 2F.7

I believe so. We only learned that the central atom has hybridized orbitals, so I'd assume that F has it's normal 2p valence orbitals.
by SGonzales_3L
Sat Nov 23, 2019 12:59 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating Ligands
Replies: 2
Views: 39

Re: Chelating Ligands

Another thing to note is that these molecules may have the ability to envelope transition metals in such a way due to the presence of sigma bonds which allow rotation of molecules. This allows molecules to bind to others in multiple places.
by SGonzales_3L
Tue Nov 19, 2019 10:38 pm
Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
Topic: repulsion
Replies: 2
Views: 94

Re: repulsion

Lone pair-lone pair repulsion is higher than lone pair-bonded pair repulsion, which is then higher than bonded pair-bonded pair repulsion. Thus, lone pair-lone pair repulsion around the central atom can reduce the bond angle between atoms attached to the central atom by a large amount. Lone pair-bon...
by SGonzales_3L
Tue Nov 19, 2019 10:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Difference between Electorn arrangement and VSEPR
Replies: 5
Views: 55

Re: Difference between Electorn arrangement and VSEPR

The electron arrangement uses the names of VSEPR shapes, but simply denotes where regions of high electron density are found around the central atom. It includes lone pairs into the consideration of the electron arrangement. In contrast, the VSEPR model itself only considers where the atoms are arra...
by SGonzales_3L
Tue Nov 19, 2019 10:30 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: cations
Replies: 2
Views: 41

Re: cations

The smaller the cation and the higher the charge, the higher its polarizing power. This just means that it can easily distort the electron cloud of a neighboring anion more easily than larger/lower charged cations.
by SGonzales_3L
Mon Nov 18, 2019 2:40 pm
Forum: Hybridization
Topic: hybridization 1st number
Replies: 3
Views: 25

Re: hybridization 1st number

I think one way of determining what number goes in front of the hybridization orbital is just by considering which shell the hybridization occurs in. If it occurs in the 3s/3p shells then you'd use 3spn, and if it occurs in the 4s/4p shells then you'd use 4spn, etc.
by SGonzales_3L
Wed Nov 13, 2019 2:17 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Answers
Replies: 10
Views: 149

Re: Midterm Answers

Yes, it's located on his website. If you go to Class Websites > CHEM 14A > Exam Information > Midterm Solutions. It should be located on the right column.
by SGonzales_3L
Wed Nov 13, 2019 2:15 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: Induced dipole-induced dipole
Replies: 1
Views: 25

Re: Induced dipole-induced dipole

This is simply because more electrons may occupy certain regions of a molecule at one time. Their distribution isn't very symmetrical, so if there are more electrons found in one region of the molecule at one time, the molecule has a slight negative charge in that region which would then repel and i...
by SGonzales_3L
Wed Nov 13, 2019 2:13 pm
Forum: Photoelectric Effect
Topic: Electrons ejection
Replies: 2
Views: 196

Re: Electrons ejection

You would use the equation for the conservation of energy in the photoelectric effect. You know that: E photon = Threshold Energy + Kinetic Energy The threshold energy was supposed to be calculated in the Q2A. The Kinetic Energy was given. E photon = hv where h=Planck's constant and v= frequency. Us...
by SGonzales_3L
Wed Nov 13, 2019 2:08 pm
Forum: *Particle in a Box
Topic: Photons and electrons
Replies: 1
Views: 106

Re: Photons and electrons

For these questions you could use conversion ratios. For the first question, you'd determine how much energy one photon carries. Then you'd divide the 100kJ of energy to determine how many photons carry the given amount of energy. For the second question, you'd convert the number of photos using rat...
by SGonzales_3L
Wed Nov 13, 2019 2:03 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear VSEPR model
Replies: 21
Views: 331

Re: Linear VSEPR model

If the central atom has either zero or three non bonding electron domains in addition to the two bonding it is linear but any other number would be some other shape. Yes, we haven't learned it yet, but lone pairs also influence the shape of molecules due to electron-electron repulsions. In the book...
by SGonzales_3L
Wed Nov 13, 2019 2:01 pm
Forum: *Particle in a Box
Topic: Hydrogen Atom
Replies: 7
Views: 271

Re: Hydrogen Atom

I believe that the energy is positive since when a Hydrogen atom absorbs a photon, its electron achieves a higher energy state.
by SGonzales_3L
Wed Nov 13, 2019 1:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Class grading
Replies: 12
Views: 251

Re: Class grading

I'm not really sure what you mean by grading scale, but based on his syllabus, the class is point based. We get a maximum of 5 points a week for chemistry community posts and homework submission. A maximum of 50 points for each test, 120 for the midterm, and 180 for the final. The maximum amount of ...
by SGonzales_3L
Fri Nov 08, 2019 8:20 pm
Forum: Dipole Moments
Topic: Relationship with Boiling Point and Shape
Replies: 2
Views: 25

Re: Relationship with Boiling Point and Shape

Essentially, the more spread out the shape of a molecule (e.g. rod shaped), the more surface area there is for intermolecular forces to interact. The more intermolecular forces there are, the less likely the molecules are to spread out into the gas phase, thus leading to a higher boiling point.
by SGonzales_3L
Fri Nov 08, 2019 8:17 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 2
Views: 33

Re: Bond Length

This is simply because heavier atoms have more electrons and their electron clouds get larger. Thus, the distance between atoms in bonds is a bit further in order to accommodate for the amount of space taken up by all the extra electron shells.
by SGonzales_3L
Wed Nov 06, 2019 11:37 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing Power (Trends)
Replies: 3
Views: 76

Re: Polarizing Power (Trends)

As anions get larger and larger, their polarizability increases. This is due to the decreasing effective nuclear charge on their valence electrons. As charge increases on cations and as they get smaller, their polarizing power increases since they can get close to the nucleus of anions and exert a h...
by SGonzales_3L
Wed Nov 06, 2019 11:34 am
Forum: Lewis Structures
Topic: Expanded Octets
Replies: 6
Views: 61

Re: Expanded Octets

One rule of thumb is to calculate the number of valence electrons in a molecule. Fulfill the octet rule for every atom in the Lewis structure. If you still have some electrons left over, it is highly likely that there is an atom with an expanded octet. Usually elements in the p-block, in period 3 or...
by SGonzales_3L
Wed Nov 06, 2019 11:32 am
Forum: Dipole Moments
Topic: Clarification on Dipole Moment
Replies: 3
Views: 39

Re: Clarification on Dipole Moment

A dipole moment measures the partial charges on atoms in a molecule. It shows which has a more negative charge due to a higher affinity for electrons and which has a more positive charge. This shows how polar a molecule will be and also shows how covalent bonds may have ionic character. You can calc...
by SGonzales_3L
Fri Nov 01, 2019 9:53 am
Forum: Octet Exceptions
Topic: Expanded Valence Shells
Replies: 3
Views: 59

Re: Expanded Valence Shells

I think it helps to fill all the other typical atoms first (e.g. H, O, F, Cl, etc.) since these are most likely to abide by the octet rule. Then, draw bonds to the central atom. One good tip is to count how many electrons/electron pairs are in the molecule/formal unit. If all the typical atoms alrea...
by SGonzales_3L
Fri Nov 01, 2019 9:45 am
Forum: Lewis Structures
Topic: Best way to go about drawing Lewis structures
Replies: 7
Views: 86

Re: Best way to go about drawing Lewis structures

I think this is the best way to go about it. I also do the same thing and change my Lewis structures as necessary. One thing I've found to be helpful is to divide the total electron count by 2 to find the number of electron pairs. This just allows me to count how many bonded atoms/lone pairs there w...
by SGonzales_3L
Thu Oct 31, 2019 10:54 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 5
Views: 71

Re: Resonance

If a molecule's resonance structures can be drawn where the central atom has an expanded octet, this would be an exception to the octet rule. Another exception would be with Group 13 elements whose resonance structures might not even complete their octet and instead form compounds with 6 electrons.
by SGonzales_3L
Thu Oct 31, 2019 10:47 pm
Forum: Electronegativity
Topic: 2D.3
Replies: 2
Views: 53

Re: 2D.3

I'm thinking that out of the three compounds listed there, Ba and Br have the highest difference in electronegativity values, followed by Ca and Br, and finally by Be and Br. That would make BaBr 2 have bonds that are primarily ionic. This is correct. If you look at a table of electronegativity val...
by SGonzales_3L
Thu Oct 31, 2019 10:43 pm
Forum: Lewis Structures
Topic: Exceptions to the Octet
Replies: 5
Views: 54

Re: Exceptions to the Octet

When P bonds with other atoms, it can expand its valence shells to accommodate more than 8 valence electrons. It actually has a valence shell of 5 electrons with the electron configuration [Ne]3s 2 3p 3 . Since n=3, the atom now has d-orbitals which can accommodate more electrons, and so P and subse...
by SGonzales_3L
Sat Oct 26, 2019 11:35 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Question 1E.25
Replies: 1
Views: 31

Re: Question 1E.25

For B, ns 2 np 3 is simply a generalization of their electron configurations. The d-orbitals are not included because as the d-orbitals get filled, their overall energy decreases and becomes lower than the s orbitals. Thus, when we write electron configurations, we write nd # before the s orbitals. ...
by SGonzales_3L
Sat Oct 26, 2019 11:28 am
Forum: Lewis Structures
Topic: Shapes of molecules
Replies: 2
Views: 25

Re: Shapes of molecules

I'm not sure what you mean by carbon having 2 valence electrons paired as all of its 4 valence electrons are bonded with hydrogen atoms. In general, though, the presence of lone pairs in a Lewis atomic structure can cause electron-electron repulsions which increase the angle between atoms, thus affe...
by SGonzales_3L
Sat Oct 26, 2019 11:24 am
Forum: Trends in The Periodic Table
Topic: atomic radius
Replies: 3
Views: 31

Re: atomic radius

We probably don't need to calculate it for this class, but it has been experimentally determined by measuring the distance between atom nuclei that bond together to form molecules and dividing the distance by 2 to get an individual atom's radius.
by SGonzales_3L
Sat Oct 26, 2019 11:18 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E.5
Replies: 1
Views: 27

Re: 1E.5

This statement is false because l=1 denotes electrons in the s shell whereas l=2 denotes p electrons. S shell electrons are found closer to the nucleus than p electrons and are able to shield outer e- from the electrostatic attraction of the positive nucleus. Thus, the outer electrons feel a reduced...
by SGonzales_3L
Sat Oct 26, 2019 11:12 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E.9
Replies: 1
Views: 26

Re: 1E.9

ml can only have a value of l, l-1, 0, ... , -l. Because l=0, ml can only equal 0.
by SGonzales_3L
Sat Oct 19, 2019 8:25 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: More Orbital Understanding
Replies: 3
Views: 63

Re: More Orbital Understanding

The probability depends on the shape of the shell itself. Some orbitals have nodal planes or areas where the probability density is equal to 0. This means that there is no possibility of finding an electron in these areas. An s-orbital, however, has a symmetrical electron probability density that is...
by SGonzales_3L
Sat Oct 19, 2019 8:23 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: P Orbital specifics
Replies: 4
Views: 44

Re: P Orbital specifics

Dr. Lavelle mentioned in class that the order in which the p-orbitals are filled is arbitrary. There is no regularly adopted convention as to which orbital is filled first, but it simply accepted to say that they fill px, py, and pz respectively.
by SGonzales_3L
Sat Oct 19, 2019 8:10 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron Configuration Model Confusion
Replies: 3
Views: 40

Re: Electron Configuration Model Confusion

I believe that diagram is simply a visual representation of electron configuration and of which orbitals are filled up given the number of electrons in an atom. Yes, he was filling up the orbitals as he went across the periodic table utilizing Hund's rule and the Aufbau principle.
by SGonzales_3L
Tue Oct 15, 2019 2:34 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Time of Use
Replies: 5
Views: 47

Re: Time of Use

The question, like many of the book problems, may also ask for an uncertainty in velocity since velocity is used to calculate momentum.
by SGonzales_3L
Mon Oct 14, 2019 10:26 pm
Forum: DeBroglie Equation
Topic: DeBroglie
Replies: 3
Views: 41

Re: DeBroglie

Although he derived his equation using light, De Broglie's equation is only valid for particles with mass, so do not use his equation to calculate wavelength for light. His conclusions help us understand that all particles with momentum have wavelike properties that can be calculated using this equa...
by SGonzales_3L
Mon Oct 14, 2019 10:21 pm
Forum: DeBroglie Equation
Topic: How to find work function
Replies: 2
Views: 45

Re: How to find work function

Given the velocity of the photon, we can use De Broglie's Equation: . We know the values for Planck's constant (6.626 x 10-34 Js) and for the mass of an electron (9.109 x 10-31 kg). Since we are given the velocity, we can just solve for wavelength.
by SGonzales_3L
Thu Oct 10, 2019 9:32 am
Forum: Photoelectric Effect
Topic: HW 1B15
Replies: 1
Views: 44

HW 1B15

The question asked is: "The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x 10 3 km/s. (a) What is the wavelength of the ejected electron?" What equation would we use to determine the wavelength? I could not use c= \lambda v and was unsure where to go f...
by SGonzales_3L
Thu Oct 10, 2019 9:27 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Question 1.A.15
Replies: 2
Views: 62

Re: Question 1.A.15

No, we cannot always assume that the initial state is n=1. The reason why they use n 1 =1 is because the spectral line is observed at 102.6 nm. This wavelength falls within the UV region, suggesting that the spectral line is a part of the Lyman series which, by definition, transitions where the n 1 ...
by SGonzales_3L
Wed Oct 09, 2019 11:09 pm
Forum: Empirical & Molecular Formulas
Topic: Homework problem E21
Replies: 2
Views: 65

Re: Homework problem E21

I think the clearest way to find the number of molecules of N 2 would be to start at the beginning. Do the same thing you did to find the atoms of N, but change the molar mass to correspond to that of N 2 . Thus, you should get 4.37g N 2 (1 mol/28.0314 g) = 0.156 mol N 2 where 28.0314 g is the molar...
by SGonzales_3L
Wed Oct 09, 2019 11:04 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Energy Level Transitions
Replies: 2
Views: 57

Re: Energy Level Transitions

Yes, I think that's possible. We can assume that as electrons transition from higher energy levels to n= 4, 5, ..., etc. the spectral lines present will denote a longer wavelength, and thus a smaller frequency. I'm not sure whether n=4 will be in the microwave and if n=5 will be in the radio region ...
by SGonzales_3L
Wed Oct 09, 2019 10:58 pm
Forum: Properties of Light
Topic: Atomic Spectra
Replies: 7
Views: 86

Re: Atomic Spectra

If I remember correctly, the infrared region of the electromagnetic spectrum is not included in the Balmer series.
by SGonzales_3L
Wed Oct 09, 2019 10:52 pm
Forum: Properties of Light
Topic: HW Question #1A.15
Replies: 6
Views: 63

Re: HW Question #1A.15

Haley Dveirin 4B wrote:Are there any other series like this other than the Lymen series that we need to memorize?


It might be helpful to remember the Balmer series which is a series of spectral lines found in the visible light region of the electromagnetic spectrum.
by SGonzales_3L
Thu Oct 03, 2019 11:46 pm
Forum: SI Units, Unit Conversions
Topic: scientific notation
Replies: 7
Views: 78

Re: scientific notation

Obviously, if the question explicitly asks you to utilize scientific notation you'd use it then. Otherwise, simply use it in your answer when it is convenient for you and when it helps distinguish significant figures. For example, if you have the number 6,300,000 with 3 significant figures, you'd wa...
by SGonzales_3L
Thu Oct 03, 2019 11:43 pm
Forum: SI Units, Unit Conversions
Topic: Formula Units
Replies: 3
Views: 73

Re: Formula Units

According to the book (See Fundamentals C3 on page F26), a formula unit is any combination of ions that have the same number of atoms as given in a specific formula. Essentially, we can think of it as an empirical formula for an ionic compound.
by SGonzales_3L
Thu Oct 03, 2019 11:38 pm
Forum: SI Units, Unit Conversions
Topic: Homework Problem E. 29
Replies: 3
Views: 62

Re: Homework Problem E. 29

For part (b), you are asked to find the number of Cl - ions present in however many moles you calculated in part (a). Given the molecular formula: CuCl 2 * 4H 2 O, you know that in one molecule, there are 2 chlorine ions. This means that the mole ratio is 2 mol Cl - : 1 mol CuCl 2 * 4H 2 O. You can ...
by SGonzales_3L
Thu Oct 03, 2019 11:32 pm
Forum: Significant Figures
Topic: How would sig figs be used in a problem?
Replies: 7
Views: 68

Re: How would sig figs be used in a problem?

In most problems I've encountered, they do not explicitly ask for you to use significant figures. Even so, it is common practice to use the significant figure rules in essentially every calculation you do in chemistry. One rule of thumb, though, is to wait to round the significant figures until the ...
by SGonzales_3L
Wed Oct 02, 2019 1:42 pm
Forum: Limiting Reactant Calculations
Topic: HW M19
Replies: 2
Views: 38

HW M19

I was a bit confused on how to begin calculating the empirical and molecular formulas for problem #M19, about the combustion of caffeine. We are given the information that there is 0.376 g of caffeine initially and, when burned, the products are 0.682g CO 2 , 0.174 g H 2 O, and 0.110 g N 2 . We also...
by SGonzales_3L
Wed Oct 02, 2019 1:29 pm
Forum: Limiting Reactant Calculations
Topic: Homework M11
Replies: 4
Views: 58

Re: Homework M11

Yes, you'd have to find the limiting reactant of the first equation to then find the limiting reactant of P 4 O 10 . As stated in the previous reply, since 5.77g of P 4 and 5.77 g of O 2 are the original reactant values, you'd convert those to moles and determine the theoretical yield of P 4 O 6 . T...

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