Search found 30 matches

Thu Dec 06, 2018 7:18 pm
Forum: Bronsted Acids & Bases
Topic: How to tell if it is an acid or base?
Replies: 4
Views: 253

Re: How to tell if it is an acid or base?

Acids also tend to have the form HA where A is an element and bases tend to have the form BOH where B is an element.
Thu Dec 06, 2018 7:14 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: H30+ and H+
Replies: 4
Views: 201

H30+ and H+

For the Ka formula, why is H30+ and H+ the same thing?
Thu Dec 06, 2018 7:06 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strength of an acid/base
Replies: 2
Views: 182

Re: Strength of an acid/base

You can determine the strength of an acid or base by finding the pKb and pKa of that base or acid. The smaller the pKb, the stronger the base. The larger the pKa, the stronger the corresponding conjugate base.
Also, the weaker the bond, the stronger the acid. Hope this helps!
Sat Dec 01, 2018 11:52 pm
Forum: Naming
Topic: Aqua
Replies: 2
Views: 110

Re: Aqua

Dr. Lavelle mentioned that it is better to write it so that it is OH2 to show that the lone pairs on the oxygen is the one binding to the central atom. If it was written like H20 then it would make it seem like the H is interacting with the central atom which isn’t true. This is why we switch the or...
Sat Dec 01, 2018 11:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone pairs
Replies: 4
Views: 245

Re: Lone pairs

For repulsion strength, lone-lone pair has the highest repulsion strength, then it is lone-bonding pair and the weakest is bonding-bonding pair. Therefore, the lone pair electron forces the bonding electron closer together. This causes the angle to be slightly smaller than expected.
Sat Dec 01, 2018 11:38 pm
Forum: Hybridization
Topic: 2SP^3 vs. SP^3
Replies: 6
Views: 255

Re: 2SP^3 vs. SP^3

Just adding on, elements such as Carbon would have hybridization 2sp^2 and sp^2. Hydrogen would be 1s. Like mentioned above, the one with the 2 in front is just more specific and it allows you to figure out which element is being hybridized.
Sun Nov 25, 2018 9:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar vs Nonpolar
Replies: 5
Views: 168

Re: Polar vs Nonpolar

Draw a Lewis Structure and examine the shape of the molecule. If the bonds are symmetrical and their polarities cancel each other out, then the molecule is non polar. If the bonds are asymmetrical and thus the more electronegative element is on one end and the electropositive element is on the other...
Sun Nov 25, 2018 9:31 pm
Forum: Hybridization
Topic: promoted hybridization
Replies: 4
Views: 183

Re: promoted hybridization

Electron promotion is when an electron absorbs a photon to jump from a low energy level to a higher energy orbital. This is important because when bonds are formed, energy is released and then the system becomes more stable. Thus, atoms provide energy to promote an electron and this would make it in...
Sun Nov 25, 2018 9:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test
Replies: 5
Views: 274

Re: Test

I think it would just be hybridization and VSEPR models since that’s all we really covered after the midterm!
Fri Nov 16, 2018 12:06 am
Forum: Sigma & Pi Bonds
Topic: Differences in energy
Replies: 5
Views: 255

Re: Differences in energy

Hi, sigma bonds are stronger than pi bonds. This means that the sigma bond will have higher energy because the s orbital overlaps over a greater area than the p orbital.
Thu Nov 15, 2018 11:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion Strength
Replies: 5
Views: 203

Re: Repulsion Strength

The bonding electron is further from the central atom than a lone pair which is close to the nucleus (which is positively charged). Therefore, the VSEPR theory says that repulsion by the lone pair is greater than the repulsion by the bonding pair.
Thu Nov 15, 2018 11:44 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle of Sulfite Ion
Replies: 2
Views: 129

Bond Angle of Sulfite Ion

In lecture Dr. Lavelle mentioned that although sulfite has 4 electron pairs arranged tetrahedrally the O-S-O bond angles are 106 degrees and not the expected 109.5 degrees. Can someone please explain why?
Sun Nov 11, 2018 11:26 pm
Forum: Lewis Structures
Topic: Poly-atomic Ions
Replies: 2
Views: 186

Re: Poly-atomic Ions

It depends! If it’s a negative charge, you generally want to make sure that the most electronegative element will take this charge. You generally don’t want your central atom to take the charge, but if you really have to I think it’s better for it to take a positive charge than a negative formal cha...
Sun Nov 11, 2018 11:24 pm
Forum: Bond Lengths & Energies
Topic: Bond Lengths
Replies: 4
Views: 230

Re: Bond Lengths

You can know bond lengths through dissociation energies. The strength of a bond is measured by its dissociation energy which is the energy required to break the bond. Stronger bonds are shorter bonds and weaker bonds are longer bonds. This is because larger atoms have larger bond lengths (more dista...
Sun Nov 11, 2018 11:21 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability
Replies: 4
Views: 229

Re: Polarizability

More electrons means that these electrons will repel each other more, increasing the radius, increasing distortion and thus increasing polarizability!
Sun Nov 04, 2018 1:31 am
Forum: Formal Charge and Oxidation Numbers
Topic: shortcut for FC
Replies: 6
Views: 322

Re: shortcut for FC

My TA told me that every bond (line) is counted as one and every lone pair is counted as two. So you would basically just count the number of lines and the number of dots and subtract it from the number of valence electrons!
Sun Nov 04, 2018 1:29 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Post Module #41
Replies: 1
Views: 350

Post Module #41

The question is: For the hydrogen atom which statement is true? A. The transition from n = 5 to n = 3 involves greater energy than one from n = 4 to n = 2. B. The transition from n = 4 to n = 2 emits radiation of longer wavelength than the transition from n = 5 to n = 1. C. All transitions from stat...
Fri Nov 02, 2018 2:31 am
Forum: Lewis Structures
Topic: 6th Edition 3.65
Replies: 1
Views: 92

6th Edition 3.65

Can someone explain to me why Xe and O share a double bond? Why does Oxygen just not get another lone pair of electrons? Why is it double bonded with Xe?
Sat Oct 27, 2018 9:39 pm
Forum: Trends in The Periodic Table
Topic: P-block elements
Replies: 3
Views: 273

P-block elements

I was just wondering how you would know what p-block element gains its electrons and what p-block element loses its electrons. Does it just depend on the element?
Sat Oct 27, 2018 9:30 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Degeneracy
Replies: 6
Views: 286

Re: Degeneracy

Also, when an atom only contains a single electron (like a Hydrogen atom), if it has the same principle quantum number (n), then it is degenerate. For example, a 2s and a 2p orbital would be degenerate.
Wed Oct 24, 2018 9:22 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Post Module Assessment #42
Replies: 2
Views: 176

Post Module Assessment #42

Hi, I am having trouble figuring out how to solve this problem. 42. An excited hydrogen atom emits light with a frequency of 1.14 x 1014 Hz to reach the energy level n = 4. In what principle quantum level did the electron begin? I’m using E = hv since we are given frequency and solved for E at n = 4...
Wed Oct 17, 2018 3:00 am
Forum: Photoelectric Effect
Topic: Module Question 29 (Part B)
Replies: 4
Views: 233

Re: Module Question 29 (Part B)

The energy needed to remove an electron from one sodium atom is simply the work function converted to the right units(J/atom) You would have to multiply 150.6 kg/mol by 1000 to get 150.6*10^3 J/mol. Then you would divide that number by Avagadro's constant to get the answer 2.5*10^-19 J/atom. Why wo...
Wed Oct 17, 2018 2:54 am
Forum: Photoelectric Effect
Topic: Post Module Assessment #25
Replies: 2
Views: 175

Post Module Assessment #25

Photoelectric experiments gave rise to a new equation relating the energy of light to its frequency. Select the right equation. A. λv = c B. Ek = mv2/2 C. mv2/2 = hv - φ D. E = hv E. None of the above I put C as my answer, but this was incorrect. Can someone tell me the correct answer and why that i...
Wed Oct 17, 2018 2:51 am
Forum: Photoelectric Effect
Topic: Photoelectric Effect Post Module Questions
Replies: 2
Views: 182

Re: Photoelectric Effect Post Module Questions

I put wave to photon model as well. Can someone please explain in more detail why particle is a better choice than photon because I thought this experiment was measuring the amount of energy of each photon.
Sat Oct 13, 2018 10:50 pm
Forum: Properties of Light
Topic: Units for a Joule [ENDORSED]
Replies: 3
Views: 134

Units for a Joule[ENDORSED]

Can someone please explain why the units for a Joule are 1 kg*m^2/s^2 :) I’m just a bit confused as to where this is coming from.
Sat Oct 13, 2018 10:42 pm
Forum: SI Units, Unit Conversions
Topic: mol vs. mmol
Replies: 12
Views: 885

Re: mol vs. mmol

An easy way to remember conversions is The Great King Henry Died By Drinking Chocolate Milk. Tera, Giga, Kilo, Hecto, Deca, Base, Deci, Centi, Milli. You can see that because milli is three away from the base to the right, a mmol is 10^-3 mol.
Tue Oct 09, 2018 3:22 am
Forum: Molarity, Solutions, Dilutions
Topic: Edition 6, G5 Question
Replies: 1
Views: 119

Edition 6, G5 Question

Hi, I was doing the homework for this week and for the question G5, we are required to know that sodium carbonate is Na2CO3. In the solutions manual though, for part b, this suddenly changes to Na2CO2. I was wondering if you guys think this is a typo or if this was intentional. Thanks!!
Wed Oct 03, 2018 9:30 pm
Forum: SI Units, Unit Conversions
Topic: Formula Units??
Replies: 3
Views: 232

Re: Formula Units??

You would use Avogadro’s number because 1 mol of an atom, molecule or formula unit contains 6.022 x 10^23 atoms! Hope this helps :)
Wed Oct 03, 2018 9:22 pm
Forum: SI Units, Unit Conversions
Topic: Homework Question Edition 6 E1
Replies: 4
Views: 240

Homework Question Edition 6 E1

For question E1, you have to find how long the fibers extend, given that you string together 1.00 mol Ag atoms, each of a radius of 144pm. For my answer I got 8.67 x 10^13 m. The solution manual gives us the final answer in kilometers. I was just wondering why the answer is given in kilometers and n...
Wed Oct 03, 2018 9:17 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Hydrogen Molar Mass HW E9
Replies: 5
Views: 620

Hydrogen Molar Mass HW E9

I’m doing question E9 from Edition 6 and it asks me to calculate the molar mass of MgSo4 7H20. I used 1.00g/mol for the molar mass of hydrogen and got 246.37g/mol for the total molar mass of the salt. The solution manual says the answer is 246.48 g/mol for the total molar mass of the salt. You can g...