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: 365
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: 220
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: 253
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: 245
Naming Acids
Are we expected to know the chemical formulas of acids from their names. ex) phosphoric acid is H3PO4
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: 183
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: 1278
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: 249
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: 264
Re: What to consider for hybridization?
Yes, for hybridization you just need to draw the lewis structure and count the bonds/lone pairs.
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: 3014
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: 323
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: 906
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: 991
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: 552
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: 2240
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: 153
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: 288
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: 147
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: 799
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: 631
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: 654
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: 651
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: 441
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: 1117
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: 262
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)
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: 173
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: 185
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: 141
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: 172
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: 174
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: 92
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: 152
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: 459
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: 692
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: 249
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: 663
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: 240
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: 196
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: 176
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: 225
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: 368
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
- Topic: Radiation Type
- Replies: 5
- Views: 195
Radiation Type
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: 201
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: 145
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: 173
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: 1176
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: 1176
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: 7681
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: 322
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)
(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
- Topic: Confused about sig figs
- Replies: 2
- Views: 209
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: 253
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: 289
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: 286
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.