Search found 31 matches
- Mon Dec 03, 2018 2:19 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Negative pH?
- Replies: 5
- Views: 512
Re: Negative pH?
Since Dr Lavelle said that the regular range of pH is 0-14, that suggests that negative pH or pH greater than 14 would be possible, just unlikely
- Mon Dec 03, 2018 2:18 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Ka Calculations
- Replies: 3
- Views: 332
Re: Ka Calculations
I don't think that we will be asked to calculate Ka/Kb, but keep in mind that they represent the ratio of concentrations of products to reactants. A stronger acid/base will have a greater Ka/Kb
- Mon Dec 03, 2018 2:16 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: Ka Constant
- Replies: 4
- Views: 734
Re: Ka Constant
Two qualitative things that would be useful to know include
1) Ka and Kb deal with the ratio of concentrations
2) Products sit on top of reactants, meaning a stronger acid/base, which dissociates more easily, will have a greater Ka/Kb
1) Ka and Kb deal with the ratio of concentrations
2) Products sit on top of reactants, meaning a stronger acid/base, which dissociates more easily, will have a greater Ka/Kb
- Mon Nov 26, 2018 1:20 pm
- Forum: Dipole Moments
- Topic: Dipole Moments
- Replies: 2
- Views: 291
Re: Dipole Moments
More than one type of bond creates dipole moments. Hydrogen bonding, ionic bonding, and polar covalent bonding would create permanent dipole moments. London dispersion forces would create temporary dipole moments.
- Mon Nov 26, 2018 1:16 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: Polar Bonds
- Replies: 3
- Views: 1596
Re: Polar Bonds
Consider SiF4. Si-F bond would be ionic (and polar, and have dipoles) because the electronegativity difference is greater than 2. However, since SiF4 is tetrahedral, this same force is exerted in four directions opposite to each other. The vectors would thus cancel out and the molecule would be nonp...
- Mon Nov 26, 2018 1:12 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: MO theory
- Replies: 2
- Views: 320
Re: MO theory
Not sure how much this would help, but:
with regions of electron density:
two: sp // three: sp2 // four: sp3 // five: sp3d // six: sp3d2
with bonding orbitals:
single bond: 1 sigma
double: 1 sigma 1 pi
triple: 1 sigma 2 pi
with regions of electron density:
two: sp // three: sp2 // four: sp3 // five: sp3d // six: sp3d2
with bonding orbitals:
single bond: 1 sigma
double: 1 sigma 1 pi
triple: 1 sigma 2 pi
- Mon Nov 19, 2018 4:51 pm
- Forum: Hybridization
- Topic: hybridization vs VSEPR notation
- Replies: 3
- Views: 331
Re: hybridization vs VSEPR notation
VSEPR will show us the regions of electron density in a molecule and also the shape that those regions create. Looking at those regions of electron density, we can determine the hybridization orbitals of the molecule.
- Mon Nov 19, 2018 4:48 pm
- Forum: Hybridization
- Topic: Hybridized Orbitals
- Replies: 4
- Views: 365
Re: Hybridized Orbitals
Consider structures where the central atom has more than four areas of electron density. Looking at VSEPR models, these include octahedral, square pyramid, trigonal bipyramidal, etc. They will need to include d in their hybridization orbitals
- Mon Nov 19, 2018 4:45 pm
- Forum: Hybridization
- Topic: Labeling Compounds
- Replies: 4
- Views: 318
Re: Labeling Compounds
The first region of electron density will be in the s hybridization orbital since it fills up first just like with regular atomic orbitals
- Mon Nov 12, 2018 3:59 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bonding
- Replies: 2
- Views: 356
Re: Bonding
When thinking about bonds, think about Coloumb's Law: kQq/r^2=F, where F is force. k is a constant, Q is the charge of one atom, q the charge of the other, and r the radius between them. So, as charge increases or radius decreases (atom gets smaller), force will increase.
- Mon Nov 12, 2018 3:56 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bond Strength
- Replies: 2
- Views: 369
Re: Bond Strength
Also note that the repulsion of lone pair electrons is stronger than the repulsion of bonding electrons.
- Mon Nov 12, 2018 3:55 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Shape
- Replies: 6
- Views: 768
Re: Molecular Shape
Keep in mind that dashed lines are intermolecular interactions. Intermolecular interactions can have huge effects: consider hydrogen bonding in water that gives it surface tension. But, intermolecular interactions can also have tiny effects: van der waals forces only occur sporadically and are broke...
- Wed Nov 07, 2018 3:49 pm
- Forum: Resonance Structures
- Topic: Resonance Hybrids
- Replies: 3
- Views: 377
Re: Resonance Hybrids
BF3 has a Lewis Structure where the central atom (B) does not have a full octet.
- Wed Nov 07, 2018 3:46 pm
- Forum: Electronegativity
- Topic: Electronegativity
- Replies: 5
- Views: 545
Re: Electronegativity
When the electronegativity difference is high, the bonding compound will have an ionic bond. Ionic bonded compounds are polar and that influences their behavior with other molecules. Consider H2O which is polar. When ionic compounds (eg NaCl) interact with H2O, they break apart because the negative ...
- Wed Nov 07, 2018 3:42 pm
- Forum: Bond Lengths & Energies
- Topic: Calculating Bond Lengths
- Replies: 4
- Views: 492
Re: Calculating Bond Lengths
There are tables which give you the length of different bonds and differentiate between single, double, and triple bonds. When you have both a single and double bond, you would find the mean length. Same for other combinations.
- Sat Nov 03, 2018 3:11 pm
- Forum: Lewis Structures
- Topic: H Element
- Replies: 2
- Views: 246
Re: H Element
The same is true for He. Since these both are in the 1s (1s1 and 1s2) orbital, so they are not able to form more than one bond since they do not have a p orbital. Keep in mind though that He is a noble gas and unlikely to react.
- Sat Nov 03, 2018 3:06 pm
- Forum: Lewis Structures
- Topic: Stable
- Replies: 2
- Views: 305
Re: Stable
When formal charge is 0, the structure is most stable (when it is not an ion.) When it is an ion, formal charge should add to the charge. For example, an ion with -1 charge should have a formal charge of -1.
- Sat Nov 03, 2018 3:05 pm
- Forum: Lewis Structures
- Topic: Calculation of bond length
- Replies: 3
- Views: 336
Re: Calculation of bond length
When a molecule has a single bond and double bond that connect the same element to another element like in NO3-, in reality the double bond won't be shorter than the single bond. Instead, both bonds will have a length somewhere between the length of a double bond and a single bond. Determining this ...
- Thu Oct 25, 2018 11:04 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Ground vs Excited State
- Replies: 3
- Views: 398
Re: Ground vs Excited State
In addition, ground state is the "neutral" state of the atom. An example of an excited state is when an electron absorbs a quantum of energy and is artificially raised to a different orbital (as we've been talking about in class).
- Thu Oct 25, 2018 10:54 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: orbitals and wave functions
- Replies: 2
- Views: 298
Re: orbitals and wave functions
The first model of the atom that is still used today in basic chemistry is the Bohr model, which looks very similar to the sun (nucleus) with planets (electrons) orbiting around it. However, experiments have shown that electrons behave as waves (double slit experiment etc) so it doesn't make sense t...
- Thu Oct 25, 2018 10:41 am
- Forum: Trends in The Periodic Table
- Topic: Ionization Energies
- Replies: 3
- Views: 323
Re: Ionization Energies
You're referring to Group 4, which consists of transition metals. Transition metals form cations, although with varying charges. They would lose electrons - not gain electrons, but for most transition metal elements, the number of electrons lost would vary. I believe the other poster is talking abou...
- Wed Oct 17, 2018 4:15 pm
- Forum: Einstein Equation
- Topic: Question on Midterm
- Replies: 7
- Views: 901
Re: Question on Midterm
"Known" values don't have sig figs (or so I was taught), so any constant given to you isn't going to determine the sig figs in your work. The point of using the long version of the constant is to ensure accurate calculations.
- Wed Oct 17, 2018 4:11 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: H bar
- Replies: 5
- Views: 532
Re: H bar
What do you mean? H bar is a constant that equals h/2pi. I think it's written this way so it can theoretically be simplified using the values of delta p and delta x.
- Wed Oct 17, 2018 4:06 pm
- Forum: Properties of Light
- Topic: Homework Problem
- Replies: 2
- Views: 243
Re: Homework Problem
There's part of the problem that it feels like you're missing, and that's that 102.6nm is ultraviolet radiation, which corresponds to the Lyman Series. The Lyman Series also corresponds to the energy level n=1. Treat the unknown n like a variable and solve for it!
- Tue Oct 09, 2018 10:41 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: E.23
- Replies: 2
- Views: 616
Re: E.23
I'll help you through part a! Calculate the amount in moles of Cu2+ ions in 3.00g CuBr2. First, we must go from grams of the molecule to moles of the molecule by dividing by the molar mass. 3.00 g CuBr2 x (1 mol CuBr2/223.35g/mol CuBr2)= 1.34 x 10^2 mol CuBr2 Now you have the moles of the molecule, ...
- Tue Oct 09, 2018 10:35 pm
- Forum: Balancing Chemical Reactions
- Topic: Test 1
- Replies: 6
- Views: 2745
Re: Test 1
I would say definitely err on showing too much work. That way, your TA will be able to follow your work and award partial credit. Some TAs require you to use pen, so if that's the case for you, definitely make clear what work you want to be graded.
- Tue Oct 09, 2018 10:31 pm
- Forum: SI Units, Unit Conversions
- Topic: Units
- Replies: 8
- Views: 592
Re: Units
Even if you don't have to use units throughout your work, including them can definitely help. Carrying units throughout will let you see what cancels out and will let you know what units your final answer should be.
- Sat Oct 06, 2018 6:20 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Naming Compounds
- Replies: 3
- Views: 216
Re: Naming Compounds
When a formula has ---hydrate, the prefix represents the amount of H2O molecules present. So heptahydrate would be 7 H2O, trihydrate would be 3 H2O, and so forth. These are connected to the chemical formula with a dot.
- Sat Oct 06, 2018 2:14 pm
- Forum: SI Units, Unit Conversions
- Topic: Formula Sheet?
- Replies: 6
- Views: 533
Formula Sheet?
In AP Chemistry, we were given formula sheets that contained formulas of importance and their units, sometimes in different forms. Does anyone have insight into whether we will be given similar sheets on our tests/quizzes here?
- Sat Oct 06, 2018 2:10 pm
- Forum: Significant Figures
- Topic: Sig Figs: Addition and Subtraction
- Replies: 3
- Views: 483
Sig Figs: Addition and Subtraction
Hi, I was reading about using sig figs when adding and subtracting and I got confused. Addition and Subtraction In mathematical operations involving significant figures, the answer is reported in such a way that it reflects the reliability of the least precise operation. Let's state that another way...
- Sat Oct 06, 2018 12:53 pm
- Forum: Empirical & Molecular Formulas
- Topic: HW F11
- Replies: 4
- Views: 444
Re: HW F11
When polyatomic ions are involved in reactions, they stay together. For example, carbonate as a reactant will become carbonate as a product. That's something you should know when calculating reactions, since the charge of the polyatomic ion will determine the needed amount of whatever's attached to ...