Search found 31 matches

by Sarah Brecher 1I
Mon Jun 11, 2018 8:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework 4.7
Replies: 3
Views: 191

Re: Homework 4.7

Why wouldn't the angles be less than 120 degrees? Why is it 109.5?
by Sarah Brecher 1I
Thu Jun 07, 2018 3:29 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted vs Lewis acids
Replies: 3
Views: 320

Re: Bronsted vs Lewis acids

The definition of a Lewis acid is an electron pair acceptor. The definition of a Bronsted acid is a proton donor. On page 609 of the textbook, it says that "a Bronsted acid is a supplier of one particular Lewis acid, a proton". This makes sense since the Bronsted acid donates the electron ...
by Sarah Brecher 1I
Wed Jun 06, 2018 10:55 pm
Forum: Bronsted Acids & Bases
Topic: J11c
Replies: 4
Views: 274

Re: J11c

Chem_Mod wrote:Ca 2+ is a spectator ion; this should simplify things. The acid is the HI that gives off the proton and CaO is the proton acceptor, making it the base.


What is a spectator ion in relation to acids and bases? How would you identify one?
by Sarah Brecher 1I
Wed Jun 06, 2018 10:44 pm
Forum: Bronsted Acids & Bases
Topic: How to identify a Bronsted acid or base
Replies: 11
Views: 704

Re: How to identify a Bronsted acid or base

How can you tell if it is a Bronsted acid or base without the reaction though? For example, on J1, you are asked to identify if it is a Bronsted acid or base just by the compound. How would you do this?
by Sarah Brecher 1I
Sun Jun 03, 2018 5:58 pm
Forum: Hybridization
Topic: σ vs π bond tips thread
Replies: 5
Views: 177

Re: σ vs π bond tips thread

It's also helpful to know that pi bonds will always be parallel p-orbitals overlapping and you can only have up to 2 pi bonds, which is why only up to triple bonds exist (1 sigma bond, 2 pi bonds).
by Sarah Brecher 1I
Sun Jun 03, 2018 5:47 pm
Forum: Hybridization
Topic: homework problem 4.35 part c
Replies: 2
Views: 108

Re: homework problem 4.35 part c

The above Lewis structure is correct because you have 28 electrons. Each F atom takes a full octet with a single bond in order to minimize formal charge. You can add the remaining 4 electrons on the central atom, Br because it is past row 3 and can take an expanded octet.
by Sarah Brecher 1I
Wed May 30, 2018 6:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: HW 4.9
Replies: 10
Views: 550

Re: HW 4.9

I thought it was trigonal bipyramidal because there are 5 regions of electron density. What is the difference between trigonal bipyramidal and T-shaped then?
by Sarah Brecher 1I
Thu May 24, 2018 1:51 pm
Forum: Lewis Structures
Topic: 3.45
Replies: 2
Views: 127

Re: 3.45

I'm a little bit confused on how you drew your original Lewis structure but the way I drew it was you start with N in the middle since it is the least electronegative atom with it connected to Cl and the 2 O's. As you mentioned, you have a single bond connected to Cl with a full octet surrounded it....
by Sarah Brecher 1I
Wed May 23, 2018 11:27 am
Forum: Lewis Structures
Topic: Radical HW 3.59
Replies: 6
Views: 282

Re: Radical HW 3.59

I don't really understand how you all are finding radicals. For example question 3.55 asks us to identify which of the following are radicals: NO2-, CH3, OH, CH2O. How do you know which are radicals? A radical means that you have an unpaired valence electron which means that you would have an odd n...
by Sarah Brecher 1I
Tue May 22, 2018 10:15 pm
Forum: Lewis Structures
Topic: Radical HW 3.59
Replies: 6
Views: 282

Radical HW 3.59

For 3.59 part a, the question asks for the Lewis structure of ClO. I know this will be a radical because it has 13 electrons but I put the single electron on the O so that the formal charges would be at 0. But, the solution manual has it on Cl and therefore the Cl would have a formal charge of +1 an...
by Sarah Brecher 1I
Wed May 16, 2018 11:52 am
Forum: Resonance Structures
Topic: Radicals
Replies: 13
Views: 638

Re: Radicals

If you are asked to do a Lewis structure of a molecule with a radical, one of the biggest things to consider is the formal charge. Even though you have an odd number of electrons, it is still possible for some molecules to do a Lewis structure without any formal charges and you should make sure to w...
by Sarah Brecher 1I
Wed May 16, 2018 11:49 am
Forum: Ionic & Covalent Bonds
Topic: Percentage Ionic Character
Replies: 4
Views: 187

Re: Percentage Ionic Character

Will we be given the electronegativity of the elements so that we can determine if it is an ionic / covalent bond?
by Sarah Brecher 1I
Tue May 15, 2018 4:08 pm
Forum: Lewis Structures
Topic: Central atom
Replies: 7
Views: 243

Central atom

On homework question 3.33 part b, they asked for the lewis structure of COCl2. Which atom goes in the middle and how do you know this?
by Sarah Brecher 1I
Thu May 10, 2018 5:11 pm
Forum: Photoelectric Effect
Topic: Intensity of Photon
Replies: 8
Views: 348

Re: Intensity of Photon

The reason why increasing the intensity didn't work was because the threshold energy wasn't reached. In order to reach threshold energy, you would need to increase frequency or decrease wavelength, since they are inversely proportional. After the photoelectric effect, they realized that this wasn't ...
by Sarah Brecher 1I
Tue May 08, 2018 10:27 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty calculation
Replies: 1
Views: 127

Re: Uncertainty calculation

Uncertainty in position is the Δx in the Heisenberg uncertainty equation which is ΔxΔp > h/4π. Δp is momentum, which also can be written as m*v. Therefore, you would rewrite the equation as ΔxmΔv > h/4π and then rewrite it so that Δx is isolated (since that is what you are solving for). You are give...
by Sarah Brecher 1I
Tue May 08, 2018 12:14 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Unicorn Practice Midterm #8
Replies: 3
Views: 304

Re: Unicorn Practice Midterm #8

If the question was asking "can you blame the Heisenberg Uncertainty Principle?" what would the answer be? Yes or no?

I know that if the uncertainty is really small then you can't blame the uncertainty principle but how small is too small?
by Sarah Brecher 1I
Fri May 04, 2018 12:26 am
Forum: Trends in The Periodic Table
Topic: Electron affinity
Replies: 4
Views: 178

Re: Electron affinity

I believe that a full octet is the exception because once the shell is filled, the atom is stable and therefore there is no need for an electron to be added to the shell. For example, if you were asked which has a higher electron affinity between elements Ne and Cl, Cl would have the higher electron...
by Sarah Brecher 1I
Thu May 03, 2018 10:31 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Quantum Number
Replies: 2
Views: 178

Re: Magnetic Quantum Number

I don't think we would be expected to find out the exact value of m(l). Instead, we would be asked to find the range, which is explained above. This range tells us how many orbitals there are. For example, if we are given l=2, we know that is a d orbital and have the values {-2,-1,0,1,2} which is 5 ...
by Sarah Brecher 1I
Thu May 03, 2018 10:26 pm
Forum: Quantum Numbers and The H-Atom
Topic: Clarification on Spin Quantum Number
Replies: 4
Views: 180

Re: Clarification on Spin Quantum Number

Spin quantum number is characterized by m(s) and the numbers +1/2 or -1/2. +1/2 is spin up and -1/2 is spin down but my TA said today that we won't need able to figure out which spin up or down it will be (nor will it really matter) without giving an extra bit of information that will be provided la...
by Sarah Brecher 1I
Thu Apr 26, 2018 9:35 pm
Forum: Photoelectric Effect
Topic: homework 1.25 part b
Replies: 3
Views: 109

Re: homework 1.25 part b

In order to solve problems and get the correct answer, you need to make sure you start with the correct units. Since they're asking for energy, you would need to be in atoms. Mg isn't the correct unit and therefore you would need to convert from mg to g to mol to atoms using dimensional analysis.
by Sarah Brecher 1I
Thu Apr 26, 2018 9:25 pm
Forum: Properties of Light
Topic: Rydberg Formula for Atomic Hydrogen [ENDORSED]
Replies: 4
Views: 272

Re: Rydberg Formula for Atomic Hydrogen [ENDORSED]

While the test will give you the E(n) = -(hR)/n^2, a faster equation that I was given in discussion that is very helpful is:

v (frequency) = R [(1/nf^2) - (1/ni^2)]
by Sarah Brecher 1I
Tue Apr 24, 2018 3:14 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post Module #29 [ENDORSED]
Replies: 3
Views: 210

Atomic Spectra Post Module #29 [ENDORSED]

The question states: In 1.0 s, a 60 W bulb emits 11 J of energy in the form of infrared radiation (heat) of wavelength 1850 nm. What is the energy per photon of light emitted? How many photons of infrared radiation does the lamp generate in 1.0 s? I figured out the energy per photon of light emitted...
by Sarah Brecher 1I
Tue Apr 17, 2018 9:13 pm
Forum: Properties of Light
Topic: 1.23
Replies: 3
Views: 111

Re: 1.23

Before you convert to joules, you also would need to convert from keV to eV before you do the joule conversion. This value is your energy (E) value. Because you are solving for wavelength, use the equation E = (h*c)/ lambda and solve for lambda (wavelength).
by Sarah Brecher 1I
Mon Apr 16, 2018 9:02 pm
Forum: Properties of Light
Topic: 1.13 (b)
Replies: 6
Views: 221

Re: 1.13 (b)

The table is in nanometers so your values should match the table once you convert from meters to nanometers.
by Sarah Brecher 1I
Mon Apr 16, 2018 6:08 pm
Forum: Properties of Light
Topic: still don't uderrsatnd what a photon is [ENDORSED]
Replies: 20
Views: 411

Re: still don't uderrsatnd what a photon is [ENDORSED]

When you are changing energy levels (n), the difference in energy is given off as a photon when you are moving from a high energy electron to a lower energy level. This represents the principle of conversation of energy.
by Sarah Brecher 1I
Fri Apr 13, 2018 6:01 pm
Forum: Empirical & Molecular Formulas
Topic: Finding the molecular formula [ENDORSED]
Replies: 5
Views: 202

Re: Finding the molecular formula [ENDORSED]

Additionally, sometimes the empirical formula is the same as the molecular formula. All you need to do is calculate the molar mass of the empirical formula and compare with the given molar mass stated in the question. If the two numbers are the same, then your molecular formula is your empirical for...
by Sarah Brecher 1I
Fri Apr 13, 2018 5:57 pm
Forum: Balancing Chemical Reactions
Topic: H.15 adding solid, liquid, gas or aqueous to balanced equations [ENDORSED]
Replies: 3
Views: 208

Re: H.15 adding solid, liquid, gas or aqueous to balanced equations [ENDORSED]

Are we going to be required to add l, s, aq, or g at the end of these compounds? And how do they help us solve a problem?
by Sarah Brecher 1I
Thu Apr 12, 2018 12:27 am
Forum: Molarity, Solutions, Dilutions
Topic: When to use MiVi=MfVf
Replies: 8
Views: 645

Re: When to use MiVi=MfVf

So it depends on what you're given. If you're given 2 different molarities and 1 volume and are asking for the other volume, use this equation. It also works if you're given 2 different volumes and 1 molarity and asked to find the molarity. You would use the equation M= moles/volume when you're only...
by Sarah Brecher 1I
Wed Apr 11, 2018 9:31 pm
Forum: Limiting Reactant Calculations
Topic: M.11
Replies: 8
Views: 339

Re: M.11

How do you know that O2 is the limiting reactant for part a? After solving, I know that P4 is the limiting reactant for the first equation so do you use the leftover amount of O2 to find the limiting reactant for the second equation? Or do you use the 5.77 g O2 from the beginning to find the limitin...
by Sarah Brecher 1I
Wed Apr 11, 2018 8:51 pm
Forum: Limiting Reactant Calculations
Topic: M9
Replies: 2
Views: 114

M9

The question is: Copper nitrate reacts with sodium hydroxide to produce a precipitate of light blue copper hydroxide. In order to do this problem, I understand I need to find the balanced equation. When looking up the formula for those compounds, I get Cu(NO3)2 for copper nitrate, NaOH for sodium hy...
by Sarah Brecher 1I
Tue Apr 10, 2018 9:04 pm
Forum: Molarity, Solutions, Dilutions
Topic: G.5 Part A) Molarity [ENDORSED]
Replies: 9
Views: 360

Re: G.5 Part A) Molarity [ENDORSED]

Also, why wouldn't you use the volume of 250 mL given in the first sentence of the question and use the equation M(initial)V(initial)=M(final)V(final)?

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