Search found 148 matches

by sarahsalama2E
Wed Nov 13, 2019 9:59 pm
Forum: Administrative Questions and Class Announcements
Topic: Test #2
Replies: 22
Views: 259

Re: Test #2

Correct, it will be on IMF'S, VESPR, and the rest of bonding that was not covered on the midterm.
by sarahsalama2E
Mon Nov 11, 2019 2:45 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: intermolecular forces/polarity
Replies: 2
Views: 27

Re: intermolecular forces/polarity

Higher attraction (aka dipole moment) means that it takes more energy to disassociate the bond, which results in a higher melting or boiling point. Like what was mentioned before, you must draw the lewis structure to see if the bonds cancel out, because the particular bonds could be polar but the mo...
by sarahsalama2E
Mon Nov 11, 2019 2:43 pm
Forum: Electronegativity
Topic: Noble Gases
Replies: 19
Views: 162

Re: Noble Gases

Noble gases are not included in the e-negativity trend, because they are already full (p6 electrons) they do not want to add any more, because that would make them unstable. The goal is always to be as stable as possible.
by sarahsalama2E
Mon Nov 11, 2019 2:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole moment
Replies: 4
Views: 32

Re: Dipole moment

So when an atom is not bonded to itself, does that always result in a dipole moment?
by sarahsalama2E
Mon Nov 11, 2019 2:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: H2O and Ionic Compounds
Replies: 3
Views: 20

Re: H2O and Ionic Compounds

The strongly different polar charges are able to interact with BOTH positive and negative charged ions, therefore disassociating them.
by sarahsalama2E
Mon Nov 11, 2019 2:41 pm
Forum: Octet Exceptions
Topic: More then 8 electrons
Replies: 5
Views: 48

Re: More then 8 electrons

Yes, this is allowed because it has an expanded octet due to the d orbital which can hold up to 10 electrons.
by sarahsalama2E
Mon Nov 11, 2019 2:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polar bonds and molecular shape
Replies: 2
Views: 19

polar bonds and molecular shape

I know we haven't covered this yet, but just wondering how exactly polar bonds affect the shape of a molecule?
by sarahsalama2E
Wed Nov 06, 2019 4:47 pm
Forum: Quantum Numbers and The H-Atom
Topic: Equations we need for midterm
Replies: 7
Views: 111

Re: Equations we need for midterm

Yes it is
by sarahsalama2E
Sun Nov 03, 2019 10:39 pm
Forum: Trends in The Periodic Table
Topic: Electron affinity vs electronegativity
Replies: 7
Views: 42

Re: Electron affinity vs electronegativity

Do we need to know the actual or formal definitions of terms like this for the exam?
by sarahsalama2E
Sun Nov 03, 2019 10:38 pm
Forum: Formal Charge and Oxidation Numbers
Topic: How to know where a double bond should go?
Replies: 10
Views: 74

Re: How to know where a double bond should go?

You have to check that the double bond wouldn’t violate a particular atoms octet rule, also you should draw the double bond so that it stabilizes the molecule the most and reduces the formal charge as much as possible.
by sarahsalama2E
Sun Nov 03, 2019 10:36 pm
Forum: Resonance Structures
Topic: Drawing the resonance hybrid
Replies: 2
Views: 37

Drawing the resonance hybrid

Will we need to draw the actual resonance hybrid on the exam, or can we just draw the arrows between the resonance structures signifying that the structures are contributing to the final resonance structure...
by sarahsalama2E
Sun Nov 03, 2019 10:34 pm
Forum: Resonance Structures
Topic: Including resonance structures
Replies: 2
Views: 23

Including resonance structures

So do we need to draw the resonance structures for each time there are resonance structures, or only when it
Is asked for in the specific question?
by sarahsalama2E
Sun Nov 03, 2019 10:33 pm
Forum: Bond Lengths & Energies
Topic: Why Are Double Bonds Shorter
Replies: 16
Views: 195

Re: Why Are Double Bonds Shorter

Should we also know the relative strengths of polar covalent vs non polar covalent forces
by sarahsalama2E
Wed Oct 30, 2019 11:41 pm
Forum: Properties of Electrons
Topic: Knowing masses
Replies: 2
Views: 54

Re: Knowing masses

no, i asked today in a review session and the UA's said that they would be given on the formula sheet.
by sarahsalama2E
Wed Oct 30, 2019 11:39 pm
Forum: Resonance Structures
Topic: Delocalized Electrons
Replies: 4
Views: 27

Re: Delocalized Electrons

I think that electrons are not really stationary like we draw them in lewis structures, but rather they move around (meaning that they are delocalized). You can see this in resonance structures and resonance hybrid.
by sarahsalama2E
Wed Oct 30, 2019 11:38 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Will we have to do calculations with the wave functions?
Replies: 1
Views: 23

Re: Will we have to do calculations with the wave functions?

I believe no (if you are referring to psi), however make sure to know de broglie's, heisenberg. Also make sure to use SI units for those !
by sarahsalama2E
Wed Oct 30, 2019 11:35 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 4
Views: 25

Re: Drawing Lewis Structures

Place the least electronegative element in the middle of the lewis structure. Also the single available element is in the middle of the structure.
by sarahsalama2E
Wed Oct 30, 2019 11:33 pm
Forum: Resonance Structures
Topic: Why do all of the bonds have the same length regardless of double/single bonds in a resonance structure?
Replies: 4
Views: 37

Re: Why do all of the bonds have the same length regardless of double/single bonds in a resonance structure?

This is because the actual structure is a resonance hybrid where the bonds are all roughly the same length. Also in a real structure, electrons move around as well.
by sarahsalama2E
Wed Oct 30, 2019 11:31 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Why does 3d come before 4s?
Replies: 2
Views: 21

Re: Why does 3d come before 4s?

That is correct, it is also important to note that when 4s begins to fill with electrons, 4s has higher energy than 3d. So, we right 3d before 4s. Also this is for ease of removing an electron when we are forming anions.
by sarahsalama2E
Tue Oct 22, 2019 6:30 pm
Forum: DeBroglie Equation
Topic: DeBroglie Equation
Replies: 11
Views: 67

Re: DeBroglie Equation

Just wondering that when we use DeBroglie Equation and Heisenberg Uncertainty Equation, we are using Kg and m as these are the SI units?
by sarahsalama2E
Tue Oct 22, 2019 6:29 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Excited state vs ground state
Replies: 4
Views: 30

Re: Excited state vs ground state

Like what was mentioned above by others, pay attention to the written electron configuration to notice an electron "jumping" levels. Additionally, when looking at drawn orbital diagrams, making sure that each orbital is filled before moving on to the next ensures that it is in the ground s...
by sarahsalama2E
Tue Oct 22, 2019 6:27 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Balmer and Lyman series
Replies: 5
Views: 29

Re: Balmer and Lyman series

The Balmer series releases electrons to the n=2 level and happens in visible light while the Lyman series releases electrons to the n=1 level and happens in UV light.
by sarahsalama2E
Tue Oct 22, 2019 6:25 pm
Forum: Properties of Light
Topic: Combining Different Equations
Replies: 8
Views: 61

Re: Combining Different Equations

Personally, I just write down all the equations i know or see fit and use which ones make sense given the variables that I have in the problem at hand. Make sure that you are using reasonable equations at each step of the problem.
by sarahsalama2E
Tue Oct 22, 2019 6:23 pm
Forum: Trends in The Periodic Table
Topic: Effective Nuclear Charge
Replies: 7
Views: 37

Re: Effective Nuclear Charge

atomic radius increases down a group and decreases down a period. Because the # of shells stays the same across a period, the effective nuclear charge is increasing because the atomic # (therefore charge of nucleus) is increasing. Because this is happening, the atomic radius decreases due to attract...
by sarahsalama2E
Tue Oct 22, 2019 6:20 pm
Forum: Properties of Electrons
Topic: x,y,z for Electrons
Replies: 10
Views: 80

Re: x,y,z for Electrons

x,y,z is essentially the planes that the different p-orbitals could be oriented on. There are three orientations or planes--> px,py,pz.This is also just being more specific regarding the electron placement in the p-orbital. Because we know hund's rule, each px,py,pz must be filled with one e- before...
by sarahsalama2E
Tue Oct 22, 2019 6:18 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energies Trend
Replies: 5
Views: 31

Re: Ionization Energies Trend

ionization energy is the energy required to remove an electron from an atom in the gas phase. The further away an electron is from the nucleus the easier it is to remove. Ionization energy increases across a period because the nuclear charge is greater and the electrons are still being added to the ...
by sarahsalama2E
Mon Oct 21, 2019 2:11 pm
Forum: Properties of Electrons
Topic: Problem 1E.5
Replies: 3
Views: 39

Re: Problem 1E.5

(a) false--> the effective nuclear charge is the nuclear charge - shielding e- (b) true--> because electrons in the s-orbital are closer to the nucleus and can penetrate to the nucleus of the atom, compared to electrons that are farther away (c) false, l=1 is closer (d) true= because s orbital is sh...
by sarahsalama2E
Mon Oct 21, 2019 1:55 pm
Forum: Trends in The Periodic Table
Topic: Atomic Radius
Replies: 7
Views: 78

Re: Atomic Radius

Atomic radius is 1/2 the distance between the centers of neighboring atoms, and increases as you go down a group and decreases across a period. It is important to know that that ionic radii also shows the same trends.
by sarahsalama2E
Wed Oct 16, 2019 4:59 pm
Forum: Properties of Light
Topic: Constant for Speed of Light
Replies: 14
Views: 88

Re: Constant for Speed of Light

Personally, I have always used 3.0 x 10^8 m/s for the constant c and my answers have been correct, but I would just check the formula sheet that's given on the test next time just to be safe.
by sarahsalama2E
Wed Oct 16, 2019 4:56 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron spin
Replies: 8
Views: 80

Re: Electron spin

Just like what was mentioned above, use +1/2 and -1/2 spin to distinguish up vs down spin. Remember, no two electrons in the SAME element can have the same set of quantum numbers.
by sarahsalama2E
Wed Oct 16, 2019 4:53 pm
Forum: *Shrodinger Equation
Topic: Equations for Quantum Topics
Replies: 3
Views: 25

Re: Equations for Quantum Topics

Remember that the magnetic quantum number (ml) is a set of possible values as it could be anywhere from -l to +l.
by sarahsalama2E
Wed Oct 16, 2019 4:51 pm
Forum: Properties of Electrons
Topic: Relationship between Speed and Frequency
Replies: 3
Views: 31

Re: Relationship between Speed on Frequency

Remember that the equation is c=wavelength x (v) ---> meaning that v stands for frequency NOT velocity. Speed and frequency are not related in a directly proportional manner. Increasing the frequency simply means increasing the cycles per second that are happening of the given wave, and decreasing t...
by sarahsalama2E
Wed Oct 16, 2019 4:47 pm
Forum: Quantum Numbers and The H-Atom
Topic: X Y and Z
Replies: 7
Views: 76

Re: X Y and Z

Depending on the particular orientation, then it will be in the x, y or z plane. This is contingent upon the ml number we find when solving for the quantum numbers.
by sarahsalama2E
Sun Oct 13, 2019 3:03 pm
Forum: Significant Figures
Topic: When to apply Sig Figs
Replies: 6
Views: 63

Re: When to apply Sig Figs

i like to apply the sig figs AT THE VERY END of my calculation. i write all the decimals points given to me by my calculator at each step of the problem or question. This ensures that I get the most accurate answer i possibly can.
by sarahsalama2E
Sun Oct 13, 2019 3:01 pm
Forum: Balancing Chemical Reactions
Topic: Any Easy Way
Replies: 10
Views: 121

Re: Any Easy Way

i typically like to start with the element that occurs the most on one side of the equation and then move on to O and H (those are usually the most difficult so I like to do those at the end). Make sure you count each element on each side of the equation to ensure that both sides match.
by sarahsalama2E
Thu Oct 10, 2019 12:10 am
Forum: Molarity, Solutions, Dilutions
Topic: L37
Replies: 3
Views: 82

Re: L37

This is a dilution problem, which means that we need to use the equations M1V1=M2V2. For part a, we need to do 16 M (X L)= 1 L (.50 M)--> this gives us the amount of L that we need to use from the 16 M solution. which is 31 mL. You would then dilute this amount with water, until you reach the 1 L ma...
by sarahsalama2E
Thu Oct 10, 2019 12:00 am
Forum: Quantum Numbers and The H-Atom
Topic: Frequency
Replies: 15
Views: 145

Re: Frequency

Frequency and Energy are directly proportional to one another. This is because E= hv therefore the change in Energy must also be directly proportional. A higher frequency means a higher energy. This is why UV light has high frequency and high energy.
by sarahsalama2E
Wed Oct 09, 2019 11:57 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Molar Mass
Replies: 7
Views: 85

Re: Molar Mass

keyword: molecules

because molecules is mentioned, we can use avogadros number which is 6.023 x 10^23 to convert to molar mass. Using dimensional analysis we can cancel out the molecules when we multiple the given grams by avogadros number--> this gives us the molar mass of the sample.
by sarahsalama2E
Wed Oct 09, 2019 11:52 pm
Forum: Properties of Light
Topic: Atomic Spectra
Replies: 7
Views: 67

Re: Atomic Spectra

Correct, the UV region has the highest transition for electrons, which is from n=1 --> n=2. you can remember that this has the biggest difference, because the UV region also has the higher frequency and energy (frequency and energy are directly related, aka proportional. The Visible and Infared regi...
by sarahsalama2E
Wed Oct 09, 2019 11:47 pm
Forum: Limiting Reactant Calculations
Topic: Determining an empirical formula by combustion analysis
Replies: 2
Views: 63

Re: Determining an empirical formula by combustion analysis

So first, given the values of .306 g of water and .815 g of CO2, you would need to convert these values into moles--making sure that you are using mol:mol ratio for the specific element (either C or H) when doing these calculations. Ex: .815 g CO2 x 1 mol/44.01 g CO2 x 1 mol c/1 mol co2--> .01855 mo...
by sarahsalama2E
Wed Oct 02, 2019 4:07 pm
Forum: Limiting Reactant Calculations
Topic: M.9
Replies: 5
Views: 89

Re: M.9

So the net ionic equation is essentially the chemical reaction with only the things that are participating in the reaction. Things that are not found on BOTH the reactants and products side of the reaction are called spectators and are NOT involved in the net ionic equation. Essentially, when making...
by sarahsalama2E
Wed Oct 02, 2019 4:03 pm
Forum: Properties of Light
Topic: Intensity VS Frequency
Replies: 3
Views: 63

Re: Intensity VS Frequency

a shorter wavelength has a higher frequency (meaning that the amount of oscillations per time period is higher) a longer wavelength has a lower frequency (meaning that the amount of of oscillations per time period is lower) For example: blue light frequency is 6.4 x 10^ 14 Hz while red light frequen...
by sarahsalama2E
Wed Oct 02, 2019 3:50 pm
Forum: SI Units, Unit Conversions
Topic: rounding of the elements. [ENDORSED]
Replies: 6
Views: 70

Re: rounding of the elements. [ENDORSED]

Personally, I use the entire values that I get from my calculator in each step of the problem until I get to the final step, then when I get there I round/determine the correct number of sig figs that I need at the end. I do it this way just to make sure I am exact as possible, or as much as I can be.
by sarahsalama2E
Wed Oct 02, 2019 3:45 pm
Forum: Properties of Light
Topic: Angstrom Unit [ENDORSED]
Replies: 2
Views: 48

Re: Angstrom Unit [ENDORSED]

sure, in chemistry bond lengths are typically 10^-10 m. 10^-10m is not really a convenient number but because it used so often in relation to bond lengths. An angstrom is 10^-10m. This makes it easier to refer to this value, rather than saying 10^-10m every time we can just say one angstrom. This is...
by sarahsalama2E
Sat Sep 28, 2019 11:19 am
Forum: Significant Figures
Topic: How does Significant Figures work? [ENDORSED]
Replies: 12
Views: 141

Re: How does Significant Figures work? [ENDORSED]

just wanted to add a quick comment--when doing lets say a dilution problem for example, and the given concentration is .0458 M, you should also always present your answer to the same number of sig figs that are used in the question?
by sarahsalama2E
Sat Sep 28, 2019 11:16 am
Forum: Molarity, Solutions, Dilutions
Topic: Homework Problem G.21 [ENDORSED]
Replies: 2
Views: 63

Re: Homework Problem G.21 [ENDORSED]

concentration is moles/liters so this means that we need to find the number of moles in KCl, K2S, and K3PO4--respectively. To find the number of moles, we first need to determine the molar masses of each compound. molar mass of KCl: 74.55 g/mol molar mass of K2S: 110.26 g/mol molar mass of K3PO4: 21...
by sarahsalama2E
Fri Sep 27, 2019 1:40 pm
Forum: Empirical & Molecular Formulas
Topic: Fundamentals L.39:
Replies: 3
Views: 133

Re: Fundamentals L.39:

so we know that the equation for tin reacting with the oxygen to form an oxide is the following: Sn + O2 --> SnO2 (the 2's are subscripts) 28.35g (total product mass which is the crucible and the oxide) - 26.45 g (which is the tin sample and crucible mass) = 1.9 g which must be the mass of the react...

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