Search found 44 matches

by christabellej 3F
Mon Nov 18, 2019 8:34 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining polarity 2E 25 pt d
Replies: 3
Views: 12

Re: Determining polarity 2E 25 pt d

Yes, AX2, AX3, AX4, AX5, and AX6 are non polar if there are no electron pairs and if X is all the same.
by christabellej 3F
Mon Nov 18, 2019 8:31 am
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pair shape
Replies: 3
Views: 13

Re: lone pair shape

You would also want to take from the equatorial position and not the axial position because a lone pair in the equatorial position results in the molecule having lower energy. Lower energy is what most molecules strive for too.
by christabellej 3F
Mon Nov 18, 2019 8:26 am
Forum: Hybridization
Topic: 2F.15
Replies: 2
Views: 10

Re: 2F.15

In an sp3 hybrid, there is around 25% s character since there is one part s and three parts p. For sp2, there is about 33% character. Since the bond angle for sp2, which has greater s character, is a bigger angle than sp3, you could expect the bond angle to increase as the s character of the hybrids...
by christabellej 3F
Mon Nov 18, 2019 8:24 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 1/r^6
Replies: 3
Views: 24

Re: 1/r^6

I believe that this equation shows the the strength of the interaction is dependent on the distance between molecules. For 1/r^6, it means that the strength of the interactions drops quite quickly as the distance between the molecules become greater. Not sure if we'll need to know this for the test
by christabellej 3F
Mon Nov 18, 2019 8:22 am
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
Replies: 2
Views: 14

Re: Polarizability

The size of the atom is usually related to polarizability, and greater polarizability usually makes interactions stronger since London dispersion forces would increase. As the size of the atom gets bigger, usually there are more electrons. Since there are more electrons, the nucleus doesn't have as ...
by christabellej 3F
Mon Nov 18, 2019 8:17 am
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi Bonds
Replies: 8
Views: 28

Re: Sigma and Pi Bonds

Sigma and pi bonds are also relevant as part of the valence bond theory, which takes into account the wave nature orbitals. It is also significant because it helps understand the concept of hybridization.
by christabellej 3F
Tue Nov 12, 2019 9:18 am
Forum: Dipole Moments
Topic: Textbook question 3F.1
Replies: 5
Views: 32

Re: Textbook question 3F.1

I think it helps to draw the lewis structures of these molecules to see if they are polar or non polar. Generally, if the net dipole moments cancel out and the molecule is non polar, it would have London dispersion forces (induced dipole-induced dipole). If it is polar, then I believe dipole dipole ...
by christabellej 3F
Tue Nov 12, 2019 9:13 am
Forum: Dipole Moments
Topic: 3F.11
Replies: 3
Views: 21

Re: 3F.11

Hydrogen bonds form when there is a lone pair on the N, O, and F atom. This can be seen in HNO2 too and makes the intermolecular forces between the molecules strong.
by christabellej 3F
Tue Nov 12, 2019 9:09 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Bond Angle
Replies: 1
Views: 9

Re: Determining Bond Angle

For some molecules, drawing the structure and arranging them according to the VSEPR model could help determine bond angle. For example, if a molecule is linear, then the bond angle will be 180 degrees. If a molecule is trigonal planar, the bond angle will be 120 degrees and if it is tetrahedral, the...
by christabellej 3F
Tue Nov 12, 2019 9:03 am
Forum: Dipole Moments
Topic: 3F.5
Replies: 6
Views: 44

Re: 3F.5

To find which has a higher melting point, you would want to find out what types of IMFs each molecule or compound has, and determine which compound has the stronger IMF. For example, in a) HCl is a covalently bonded molecule while NaCl is an ionic compound. NaCl will have a higher melting point beca...
by christabellej 3F
Tue Nov 12, 2019 8:58 am
Forum: Dipole Moments
Topic: 3F.3
Replies: 5
Views: 37

Re: 3F.3

In these types of questions, it could be helpful to first draw the Lewis structures. CCl4 and CH4 are symmetric and are non polar structures overall since the net moments cancel out; they will have London dispersion forces. CH3Cl, CH2Cl2, and CHCl3 will also have dipole dipole interactions, so those...
by christabellej 3F
Mon Nov 04, 2019 8:06 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: aufbau principle
Replies: 4
Views: 34

Re: aufbau principle

The Aufbau principle is the building up principle that combines both Pauli Exclusion principle and Hunds rule. Pauli Exclusion principle states that there can be a max of two electrons per orbital and that the two electrons must be spin paired. Hunds rule states that the electrons should be placed o...
by christabellej 3F
Mon Nov 04, 2019 8:01 am
Forum: Quantum Numbers and The H-Atom
Topic: n, l ,ml, ms
Replies: 6
Views: 38

Re: n, l ,ml, ms

The magnetic spin of an electron can only be +1/2 or -1/2. This is because of the Pauli exclusion principle where there can only be two electrons per orbital, and that the electrons must be spin paired. So, one electron must go in an upwards spin (+1/2) and the other in a downwards spin (-1/2). As f...
by christabellej 3F
Mon Nov 04, 2019 7:57 am
Forum: Lewis Structures
Topic: formal charge
Replies: 4
Views: 26

Re: formal charge

Formal charge can also help you predict which structure is the lowest energy structure (and thus which structure contributes more to the hybrid) as the closer the formal charges are to 0 on the atoms gives you the lowest energy structure.
by christabellej 3F
Mon Nov 04, 2019 7:54 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: En=-hR/n^2
Replies: 1
Views: 23

Re: En=-hR/n^2

You generally use this equation when dealing with atomic spectra problems, where calculating the energy difference (or wavelength and frequency) absorbed or emitted by an element that has gone from one energy level to another. For example, if you want to know the change in energy from the emitted ra...
by christabellej 3F
Mon Nov 04, 2019 7:49 am
Forum: Einstein Equation
Topic: Module Question
Replies: 1
Views: 36

Re: Module Question

This question is a photoelectric effect questions, and gives you the minimum frequency needed to eject an electron from the molybdenum metal surface. This means that any frequency lower than this will not eject any electrons and that with this particular frequency, there won't be any excess kinetic ...
by christabellej 3F
Mon Nov 04, 2019 7:46 am
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Numbers
Replies: 5
Views: 25

Re: Quantum Numbers

The quantum number ms is the magnetic spin of the electron. In the Pauli Exclusion principle, it states that there can only be a maximum of two electrons per orbital, and that the two electron spins must be paired. That basically means that one electron will spin in an upwards direction and one in a...
by christabellej 3F
Mon Oct 28, 2019 8:50 am
Forum: Photoelectric Effect
Topic: photoelectric effect book example
Replies: 2
Views: 17

Re: photoelectric effect book example

hi! the mass of the electron, as well as the masses of neutrons/protons are on the constants and equations sheet that is on Dr. Lavelle's website. It should also be provided on the test!
by christabellej 3F
Mon Oct 28, 2019 8:44 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: HW question 1D.11
Replies: 5
Views: 31

Re: HW question 1D.11

As someone mentioned above, l= 0 is the s orbital, l=1 is p, l=2 is d, and l=3 is f. Because of that, the number of orbitals in subshells for s will be 1, p is 3, d is 5, and f is 7.
by christabellej 3F
Mon Oct 28, 2019 8:40 am
Forum: Ionic & Covalent Bonds
Topic: 2A.11
Replies: 4
Views: 30

Re: 2A.11

In order to find what metal with a 3+ state would have the ground state configuration, I find it helpful to first write what configuration the metal would have if it were not an ion. For the first one, for example, if the 3+ state is [Ar] 3d6, then the configuration for the unionized version would b...
by christabellej 3F
Mon Oct 28, 2019 8:35 am
Forum: Lewis Structures
Topic: how to know which elements bonds to which?
Replies: 3
Views: 20

Re: how to know which elements bonds to which?

In general, the central atom would be the one with the lower ionization energy. In class, Dr. Lavelle also mentioned that because H can only form one bond, it will never be the central atom.
by christabellej 3F
Mon Oct 28, 2019 8:31 am
Forum: Resonance Structures
Topic: Lewis Structures for Resonance
Replies: 4
Views: 19

Re: Lewis Structures for Resonance

Generally, the octet rule will be followed for lewis structures that have resonance. However, as someone mentioned above, some atoms can form more than four bonds because they are big enough and have the ability to fill the d orbitals. This only starts after the 3 p level though, and so some atoms i...
by christabellej 3F
Mon Oct 28, 2019 8:29 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: HW question 1B.25
Replies: 3
Views: 45

Re: HW question 1B.25

Hi! So in this problem, you know that you should use the Heisenberg equation in order to find uncertainty of speed of the electron. Since Delta p * delta x = h/4pi, and delta p can be substituted by m * delta v (velocity), you can rearrange and solve for the minimum uncertainty in a particle's veloc...
by christabellej 3F
Mon Oct 21, 2019 11:31 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: What's the right equation?
Replies: 7
Views: 42

Re: What's the right equation?

Both are the same equation. This is because the h is actually h bar and stands for h/2pi. 1/2 (h bar) would then be the same as the first equation as it is h/4pi.
by christabellej 3F
Mon Oct 21, 2019 11:24 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Spin
Replies: 5
Views: 42

Re: Electron Spin

The last quantum number, the electron spin, only has two types of spin . It's notated by +1/2 and -1/2. There should only be two types as the Pauli Exclusion Principle states that there should only be 2 electrons per orbital, and that if there are 2 electrons, the spins should be paired up (one up a...
by christabellej 3F
Mon Oct 21, 2019 11:20 am
Forum: DeBroglie Equation
Topic: 1B. 19
Replies: 4
Views: 32

Re: 1B. 19

Yes, you could use the De Broglie equation, where the wavelength is equal to Planck's constant divided by momentum (which is mass times velocity).Since h is a constant and m is nearly the same, the only thing that could be variable is the velocity. However, in this problem, it states that the proton...
by christabellej 3F
Mon Oct 21, 2019 11:16 am
Forum: Properties of Light
Topic: calculating frequency of light
Replies: 4
Views: 30

Re: calculating frequency of light

Yes, since it says lowest frequency possible, we can assume that the KE is 0. We could then use the equation where the energy of the incident light is equal to the work function plus the KE (which is 0). You could then work backwards to find the energy of the light since you know what the work funct...
by christabellej 3F
Mon Oct 21, 2019 11:13 am
Forum: Photoelectric Effect
Topic: KE energy & intensity
Replies: 5
Views: 24

Re: KE energy & intensity

The kinetic energy is related to the frequency of the incoming light because the frequency of the incoming light, by the equation E = hv, can be used to find the incident light's energy. This energy, by the conservation of energy, is equal to the work function (the energy needed to eject an electron...
by christabellej 3F
Mon Oct 21, 2019 11:10 am
Forum: *Shrodinger Equation
Topic: Calculating the probability of finding an electron at a certain location
Replies: 5
Views: 53

Re: Calculating the probability of finding an electron at a certain location

Hi, 1D4 talks about the probability of finding electrons depending on the shapes of the orbitals. In this class, we would be discussing the orbitals s, p, and d. As far as the probability of finding an electron goes, s orbitals are said to be spherically symmetrical, meaning that the probability is ...
by christabellej 3F
Mon Oct 14, 2019 9:11 pm
Forum: Einstein Equation
Topic: Homework Problem B.5
Replies: 2
Views: 23

Re: Homework Problem B.5

KeV is a unit of energy. It is equivalent to 1000 eV because of the prefix kilo. From there, you can convert this unit to another energy unit - Joules by using the constants and equations sheet. 1 eV is equivalent to 1.6022*10^-19 J, so you can then use stoichiometry to convert KeV to Joules. After ...
by christabellej 3F
Mon Oct 14, 2019 9:06 pm
Forum: *Shrodinger Equation
Topic: probability vs probability density
Replies: 3
Views: 33

Re: probability vs probability density

The probability density, symbolized by psi squared, is the probability that something will be found in a space divided by region volume. For example, if psi squared is 0, then there is a probability of 0 that the electron will be found in that space in that region's volume. Probability has no unit b...
by christabellej 3F
Mon Oct 14, 2019 8:57 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg indeterminacy equation
Replies: 2
Views: 21

Re: Heisenberg indeterminacy equation

These two expressions are actually the same. This is because the h/2 is not h, but h bar. H bar is equal to h/2pi. Thus, this would make it the same as h/4pi because 1/2hbar = 1/2(h/2pi) = h/4pi. Hope this helps a bit
by christabellej 3F
Mon Oct 14, 2019 8:54 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Radii
Replies: 2
Views: 9

Re: Radii

In addition, the radius of a cation is usually smaller than its regular atom. The radius of an anion is larger than what the neutral atom would normally be because of the increased electron repulsion effects (since anions have more electrons). For atomic radius, the atomic radius increases as you go...
by christabellej 3F
Mon Oct 14, 2019 8:50 pm
Forum: Ionic & Covalent Bonds
Topic: Bonds
Replies: 4
Views: 52

Re: Bonds

Hi, usually a metal and a nonmetal together will form an ionic bond. In an ionic bond, an electron is basically donated.Metals are usually atoms, or elements found in group 1 or 2 of the periodic table. Covalent bonds generally consist of two nonmetals together.In a covalent bond, the electron is us...
by christabellej 3F
Mon Oct 07, 2019 9:44 pm
Forum: Limiting Reactant Calculations
Topic: Percent yield
Replies: 3
Views: 30

Re: Percent yield

The theoretical yield actually doesn't have to depend on information on percent or actual yield. Theoretical yield just means the maximum yield that a product can be based on a chemical equation. So, the theoretical yield is can purely be based on calculations, stoichiometry, and molar ratios from t...
by christabellej 3F
Mon Oct 07, 2019 9:39 pm
Forum: Balancing Chemical Reactions
Topic: Fundamentals H.11
Replies: 3
Views: 39

Re: Fundamentals H.11

You would want to treat each step as separate reactions. This is because the products in these two reactions will likely be different, and you would want to make sure that your equation is balanced in that it has the same mass and atoms on both sides.
by christabellej 3F
Mon Oct 07, 2019 9:36 pm
Forum: Limiting Reactant Calculations
Topic: Determining the equation of written formulas
Replies: 2
Views: 24

Re: Determining the equation of written formulas

With B2O3 specifically, you could use the rules listed above can be used to. Oxygen, because it is in group 16, has a -2 charge. Boron has a +3 charge. Because this is a neutrally charged molecule, you know that somehow, the -2 and +3 charge have to cancel out. This is why there are 2 boron atoms an...
by christabellej 3F
Mon Oct 07, 2019 3:21 pm
Forum: Balancing Chemical Reactions
Topic: Homework Question H21
Replies: 5
Views: 63

Re: Homework Question H21

I balanced the carbon on the CO2 product because I first started out by balancing the N. Since there are 2 N on the products side and 1 N on reactants, a stoichiometric coefficient of 2 needs to be on C10H15N. Since the N was already balanced, you would want to try to balance the C by changing coeff...
by christabellej 3F
Mon Oct 07, 2019 3:13 pm
Forum: Molarity, Solutions, Dilutions
Topic: E.13
Replies: 2
Views: 53

Re: E.13

For this problem, you know that there are two isotopes of Boron and you know the molar masses of both types (and the weighted average molar mass). You also know that when the two isotopes' percent abundances are added together, they should equal 100% or 1. I like to use x and y, expressed in decimal...
by christabellej 3F
Mon Sep 30, 2019 2:22 pm
Forum: Empirical & Molecular Formulas
Topic: Problem 11b
Replies: 1
Views: 61

Problem 11b

This problem asks for the formula and there is 31.91% K, 28.93% Cl and the rest O2 (39.16%). When I converted these mass percentages to moles, I got roughly 1.22 mol O2, 0.82 mol Cl, and 0.82 mol K. After dividing all these moles by the lowest mol (0.82) I got that there is a ratio of 1.5 mol O2: 1 ...
by christabellej 3F
Mon Sep 30, 2019 2:08 pm
Forum: Limiting Reactant Calculations
Topic: Lecture Question
Replies: 2
Views: 41

Re: Lecture Question

The actual yield can't be a theoretical yield because it is highly unlikely for a reaction produced in the lab to equal 100% of maximum yield. This is due to some side reactions that may take place as well as other sorts of impurities. Some of the products may stick to sides of the container too. Th...
by christabellej 3F
Mon Sep 30, 2019 11:14 am
Forum: Balancing Chemical Reactions
Topic: Equations
Replies: 5
Views: 105

Re: Equations

It is also key to remember the law of conservation of mass when balancing equations. This law states mass cannot change in a closed system, and so to check whether an equation is balanced, there should be the same mass in products as there were in reactants. Hope that helped a bit :)
by christabellej 3F
Sun Sep 29, 2019 9:20 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Question E.9 - Writing Molecular Formula + Mole Calculations
Replies: 6
Views: 75

Re: Question E.9 - Writing Molecular Formula + Mole Calculations

The example NH4NO3 is made up of two polyatomic ions. One is NH4+ and the other is NO3-. Because the charges balance out, you'll see that there is only one NH4+ and one NO3- ion. I think there is a list somewhere of good polyatomic ions to memorize by name, but NH4+ is ammonium ion and NO3- is a nit...
by christabellej 3F
Sun Sep 29, 2019 9:10 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: MOLARITY
Replies: 17
Views: 650

Re: MOLARITY

Hi! just to add on to the post above, molarity is notated with symbol M while molality is notated with symbol m. Molarity, the moles of solute per liter solution, and molality, the moles solute per kilogram solvent, is similar to each other in room temperature aqueous solutions. The molality measure...

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