## Search found 54 matches

Wed Dec 04, 2019 10:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape vs. Molecular Geometry
Replies: 4
Views: 120

### Re: Molecular Shape vs. Molecular Geometry

Geometry would be the parent shapes: linear, trig planar, tetrahedral, trigonal pyramidal, octahedral. The shape would be like bent, see-saw, etc.
Wed Dec 04, 2019 10:50 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: ammine versus amine
Replies: 1
Views: 38

### Re: ammine versus amine

I believe you would use 'ammine' when referring to a ligand and 'amine' when referring to a functional group.
Wed Dec 04, 2019 9:24 am
Forum: Bronsted Acids & Bases
Topic: Neutralizations
Replies: 3
Views: 68

### Re: Neutralizations

I read online that bases like amines do not produce water when reacted with acid, but bases like hydroxides, oxides, and carbonates do (this would explain why ammonia and phosphoric acid would produce only a salt).
Tue Dec 03, 2019 9:19 pm
Forum: Lewis Acids & Bases
Topic: Naming Acids
Replies: 3
Views: 49

### Naming Acids

Are we expected to know the chemical formulas of acids from their names. ex) phosphoric acid is H3PO4
Tue Dec 03, 2019 9:13 pm
Forum: Naming
Topic: Formulas
Replies: 3
Views: 66

### Re: Formulas

I think so. It is on the ligand worksheet Lavelle emailed to the class.
Sun Dec 01, 2019 11:20 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Ionization of weak/strong acids and bases in water
Replies: 2
Views: 46

### Re: Ionization of weak/strong acids and bases in water

I think you have to know the strength first and from there you can determine whether the compound is 100% ionized (strong) or not 100% ionized (weak). But you wouldn't be able to go the other way around unless say you were given the chemical equation.
Sat Nov 30, 2019 11:49 pm
Forum: Student Social/Study Group
Topic: Preparing for the final
Replies: 25
Views: 416

### Re: Preparing for the final

I found the step-up sessions extremely helpful. The UA's go through worksheets that they have adapted specifically from Lavelle's old midterms/finals, so they better prepare you for his tests.
Sat Nov 30, 2019 11:37 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Shapes
Replies: 3
Views: 62

### Re: Shapes

I don't believe we have to differentiate between the two, so either answer would be correct.
Sat Nov 30, 2019 11:24 pm
Forum: Hybridization
Topic: What to consider for hybridization?
Replies: 3
Views: 67

### Re: What to consider for hybridization?

Yes, for hybridization you just need to draw the lewis structure and count the bonds/lone pairs.
Sat Nov 30, 2019 11:16 pm
Forum: Naming
Topic: Naming
Replies: 4
Views: 48

### Re: Naming

I think you just have to memorize the names. There is a list on page 723/724 in the textbook.
Sun Nov 24, 2019 2:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent Shape
Replies: 31
Views: 928

### Re: Bent Shape

1 (AX2E) or 2 (AX2E2)
Sat Nov 23, 2019 1:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 7
Views: 104

### Re: Polarity

I would draw the lewis structure to determine the shape of the molecule and identify as symmetrical or non symmetrical. With symmetrical shapes, the dipoles can each other out cancel out (tetrahedral is a special case where all four attached atoms must be the same in order to be able to cancel).
Fri Nov 22, 2019 3:51 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Studying
Replies: 14
Views: 321

### Re: Final Studying

I plan to go through all of the problems I was confused on or did wrong on the homework, midterm, and tests.
Fri Nov 22, 2019 3:43 pm
Forum: Student Social/Study Group
Topic: Any tips on how to catch up in this class?
Replies: 16
Views: 320

### Re: Any tips on how to catch up in this class?

The Covel workshops really help since the UA's go over the material from the lecture and answer questions. Some post their worksheets on chem community so you practice the past material too.
Thu Nov 21, 2019 3:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle of O2
Replies: 3
Views: 44

### Re: Bond Angle of O2

Doesn't O2 have a bond angle of 180?
Thu Nov 21, 2019 3:08 pm
Forum: Electronegativity
Topic: Determining Polarity
Replies: 4
Views: 469

### Re: Determining Polarity

With a tetrahedral shape, the molecule cannot be nonpolar unless all four attached atoms are the same (CH4). Thus, it will be polar.
Sat Nov 16, 2019 7:15 pm
Forum: Dipole Moments
Topic: 2E. 25a
Replies: 2
Views: 39

### 2E. 25a

Why is CH2CL2 polar when the shape is symmetrical and there are two dipoles pointing towards Cl. Shouldn't they cancel?
Sat Nov 16, 2019 11:33 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: Test 2
Replies: 5
Views: 54

### Re: Test 2

Content that wasn't on the midterm to Monday's lecture (11/18). I think material such as chemical bonds/forces, VSEPR (shapes, angles) and some sigma/pi bond stuff.
Sat Nov 16, 2019 11:30 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 vs. Electronegativity
Replies: 3
Views: 33

### Re: Polarizability vs. Electronegativity

Polarizability is a measure of how easily an atom's electron cloud can be distorted (so larger atoms will have higher polarizability). Electronegativity refers to the atom's ability to attract electrons (top right of the periodic table has the highest electronegativities). Thus, I don't think that t...
Thu Nov 14, 2019 2:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.11
Replies: 4
Views: 137

### Re: 2E.11

in IF4, the central atom only has 4 bonding regions (square planar). With an octahedral, the central atom has 6 bonding regions.
Thu Nov 14, 2019 2:45 pm
Forum: Dipole Moments
Topic: Polarity
Replies: 12
Views: 161

### Re: Polarity

You have to consider shape and the dipole moments. For example, if a molecule had two polar bonds both pointing towards the central atom and the shape was linear, the dipole moments would cancel (vectors) and the molecule would be non-polar. However, if you had water (where the shape is a tetrahedra...
Thu Nov 14, 2019 2:39 pm
Forum: Bond Lengths & Energies
Topic: Quiz for Next week dashes/wedges
Replies: 11
Views: 185

### Re: Quiz for Next week dashes/wedges

^ Lavelle said that we would just have to write the shape and possibly describe it, but we would never have to draw wedges/dashes.
Thu Nov 07, 2019 8:37 pm
Forum: Electronegativity
Topic: ionic character
Replies: 9
Views: 273

### Re: ionic character

yes, a larger difference in electronegativity would indicate more ionic character, while a smaller difference indicates more covalent character.
Thu Nov 07, 2019 8:33 pm
Forum: Ionic & Covalent Bonds
Topic: polarizing power
Replies: 7
Views: 105

### Re: polarizing power

Yes, the smaller the atomic radius, the more polarizing power the atom has. The larger the atomic radius, the more polarizable the atom is because it is more easily distorted.
Thu Nov 07, 2019 8:30 pm
Forum: Lewis Structures
Topic: Oxygen
Replies: 8
Views: 124

### Re: Oxygen

Oxygen also has 4 electrons in the 2p orbital, yet it would rather have a half-full shell. Thus, it would be easier to remove the 4th electron.
Thu Nov 07, 2019 4:40 pm
Forum: Ionic & Covalent Bonds
Topic: Mini Dino Nuggets 2b
Replies: 6
Views: 109

### Re: Mini Dino Nuggets 2b

C and Br both have electronegativities on the lower side, while F has the highest electronegativity in the periodic table.
C(low) - Br (low) < C (low) - F (high)
Thu Nov 07, 2019 4:34 pm
Forum: Lewis Structures
Topic: Lewis Dot Structures
Replies: 4
Views: 60

### Re: Lewis Dot Structures

I think the dots should be paired since they represent electrons (which must also be paired).
Sun Nov 03, 2019 8:24 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: 12 on workshop worksheet
Replies: 1
Views: 89

### 12 on workshop worksheet

Which of the following ranks the following bonds from most polar to least polar? a) Mg-O > Cl-O > C-O > O-O b) Cl-O > Mg-O > C-O > O-O c) Cl-O > O-O > Mg-O > C-O d) Mg-O > C-O > B-O > O-O The correct answer was d, but don't Boron and oxygen have a greater electronegativity difference than C-O, makin...
Sat Nov 02, 2019 12:44 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: manipulating equations
Replies: 3
Views: 68

### Re: manipulating equations

I don't think it is necessary to show every step because most of the time it is just a matter of dividing/multiplying/adding variables (mental math).
Sat Nov 02, 2019 12:33 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: General Question about Orbital... Filling..?
Replies: 5
Views: 63

### Re: General Question about Orbital... Filling..?

In all of the problems I have seen, the electron configurations have been written in order of increasing energy ([Ar] 3d2 4s2]). I would just write it like that in case, but I don't think it's technically wrong.
Sat Nov 02, 2019 12:29 am
Forum: Lewis Structures
Topic: Compound Names
Replies: 3
Views: 53

### Re: Compound Names

My TA said that we will most likely be given all the formulas because we did not cover nomenclature in the course. However, for molecular compounds you generally put the name of the first element, then second with the correct prefix (depends on number). For example, carbon monoxide would be CO and s...
Fri Nov 01, 2019 10:43 pm
Forum: Electronegativity
Topic: Electronegativity in Lewis Structure
Replies: 2
Views: 41

### Re: Electronegativity in Lewis Structure

Yes I think that is the general guideline, but there are exceptions so you have to check the formal charges of your final structure.
Fri Nov 01, 2019 10:40 pm
Forum: Trends in The Periodic Table
Topic: Studying techniques
Replies: 3
Views: 58

### Re: Studying techniques

I find it helpful to kind of know the reasoning behind the trends (more electron shells means larger radius as you go down a column, more protons means smaller radius as you go down a row, etc)
Fri Oct 25, 2019 11:28 am
Forum: Ionic & Covalent Bonds
Topic: Bond length
Replies: 11
Views: 122

### Re: Bond length

I think he meant that resonance structures do not exist in real life and they just predict that a compound is more stable than expected (if you were to go to a lab and actually test it). In real life where quantum mechanics is considered, the bond length is an average of the 2 lengths. Resonance is ...
Fri Oct 25, 2019 11:13 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Writing e- Configurations
Replies: 15
Views: 226

### Re: Writing e- Configurations

I think you can always do the shortcut with the noble gases, as some of the full electron configurations can get pretty long. But if the element were Cl-, you couldn't just put [Ar] and would have to start with [Ne]....
Fri Oct 25, 2019 12:57 am
Forum: Properties of Light
Topic: photoelectric effect
Replies: 4
Views: 90

### Re: photoelectric effect

When light acts as a particle (as in the photoelectric effect), increasing intensity means increasing the # of photons.
Thu Oct 24, 2019 1:01 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: What's the difference between subshell vs orbitals?
Replies: 8
Views: 164

### Re: What's the difference between subshell vs orbitals?

subshells are the l value and tell you the shape (spdf), while orbitals are the ml value and tell you the orientation (xyz)
Thu Oct 24, 2019 12:56 am
Forum: Ionic & Covalent Bonds
Topic: How are lewis structures filled?
Replies: 6
Views: 62

### Re: How are lewis structures filled?

I don't think the order of the sides necessarily matters but generally 1 electron should be put on each first, then the 2nd can be distributed.
Sat Oct 19, 2019 10:37 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals vs. Shells
Replies: 5
Views: 76

### Re: Orbitals vs. Shells

Shells are the n value, subshells are the l value, and orbitals are the ml value (s,p,d)
Sat Oct 19, 2019 8:41 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework Problem 1A #3
Replies: 3
Views: 77

### Re: Homework Problem 1A #3

the "extent of the change" means the slope of the wave. Then, as frequency decreases, amplitude decreases (the waves get farther apart) and the extent of the change decreases.
Sat Oct 19, 2019 8:34 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg
Replies: 4
Views: 33

### Re: Heisenberg

I agree with the person above. There are uncertainties in the momentum and velocity of a particle since it can take multiple paths (the actual one cannot be determined accurately).
Thu Oct 17, 2019 3:12 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisengberg Uncertainty Equation Meaning
Replies: 7
Views: 114

### Re: Heisengberg Uncertainty Equation Meaning

The equation means that there is uncertainty in the momentum and position of a particle, so it basically measures this uncertainty. The questions will probably ask things like "What is the minimum uncertainty in its position?" or "What is the minimum uncertainty in the speed?"
Thu Oct 17, 2019 1:43 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Replies: 5
Views: 57

Are we expected to memorize which frequencies/wavelength correspond to the type of radiation (microwaves, gamma, etc.)?
Thu Oct 10, 2019 3:49 pm
Forum: Properties of Light
Topic: High Intensity
Replies: 5
Views: 70

### Re: High Intensity

When light acts as a particle, higher intensity means higher number of photons. When light acts like a wave, higher intensity means higher kinetic energy.
Thu Oct 10, 2019 3:44 pm
Forum: Empirical & Molecular Formulas
Topic: F.21
Replies: 2
Views: 87

### Re: F.21

You can convert to grams, but the solution manual kept the mg because they converted to mmol. As long as you keep the units consistent (gram to mole or mg to mmol) you should get the same answer.
Thu Oct 10, 2019 3:38 pm
Forum: Photoelectric Effect
Topic: threshold energy
Replies: 4
Views: 62

### Re: threshold energy

the amount of energy required to remove an electron from the metal surface. ex) if the energy of the photon is less than the threshold energy, no electrons will be ejected
Thu Oct 10, 2019 3:33 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Reactions
Replies: 20
Views: 553

### Re: Balancing Chemical Reactions

My TA suggested starting with the elements that occur the least and (if applicable) leaving elements that stand alone like oxygen for last.
Thu Oct 10, 2019 3:33 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Reactions
Replies: 20
Views: 553

### Re: Balancing Chemical Reactions

My TA suggested starting with the elements that occur the least and (if applicable) leaving elements that stand alone like oxygen for last.
Thu Oct 10, 2019 3:30 pm
Forum: Empirical & Molecular Formulas
Topic: Converting from grams to percentage
Replies: 11
Views: 510

### Re: Converting from grams to percentage

When you are given the grams of each element in the problem, I don't think it is necessary to find the %mass composition because you can just convert to moles right away and find the mole ratio (goal). I believe you only need to use the 100 gram sample when the problem gives the % composition only (...
Thu Oct 03, 2019 3:37 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Fundamental E
Replies: 2
Views: 109

### Re: Fundamental E

I think you have to use molar ratios for this question because the number of atoms of H and O do not add up to the number of water molecules. There are 2 moles of Hydrogen and 1 mole of O for every 1 mole of H2O, so i think you do:
(3.14 mol H2O) x (2 mol H/1 mol H2O) x (6.022 x 10*23 atoms/1 mol H)
Thu Oct 03, 2019 3:17 pm
Forum: Significant Figures
Replies: 2
Views: 82

### Re: Confused about sig figs

I think it should be the first (6.63 x 10*5) since the definition of scientific notation is a number between 1-10 (excluding 10) is multiplied by a power of 10.
Thu Oct 03, 2019 3:12 pm
Forum: Balancing Chemical Reactions
Topic: Fundamentals H21
Replies: 2
Views: 99

### Re: Fundamentals H21

I think it gives the chemical formula in the question (CH4N2O). so the reactants would be: C10H15N and oxygen gas and the products would be carbon dioxide, water, and CH4N2O
Thu Oct 03, 2019 2:51 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Fundamentals E25
Replies: 5
Views: 88

### Re: Fundamentals E25

In this question, I think formula units basically means the number of molecules (which you can find by multiplying the number of moles of KNO3 given by Avogadro's number).
Thu Oct 03, 2019 2:45 pm
Forum: Empirical & Molecular Formulas
Topic: Faster way to find molecular formula?
Replies: 3
Views: 80

### Re: Faster way to find molecular formula?

I don't think there is a faster way because you need the empirical formula to know the ratios of each element in the compound. The molecular formula is like a multiple of the empirical.