CHEMISTRY COMMUNITY

Alicia Gibbons 1B

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

Alicia Gibbons 1B

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

Alicia Gibbons 1B

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

Alicia Gibbons 1B

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.

Alicia Gibbons 1B

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...

Alicia Gibbons 1B

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

Alicia Gibbons 1B

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.

Alicia Gibbons 1B

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

Alicia Gibbons 1B

The first region of electron density will be in the s hybridization orbital since it fills up first just like with regular atomic orbitals

Alicia Gibbons 1B

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.

Alicia Gibbons 1B

Also note that the repulsion of lone pair electrons is stronger than the repulsion of bonding electrons.

Alicia Gibbons 1B

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...

Alicia Gibbons 1B

BF3 has a Lewis Structure where the central atom (B) does not have a full octet.

Alicia Gibbons 1B

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 ...

Alicia Gibbons 1B

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.

Alicia Gibbons 1B

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.

Alicia Gibbons 1B

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.

Alicia Gibbons 1B

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 ...

Alicia Gibbons 1B

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).

Alicia Gibbons 1B

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...

Alicia Gibbons 1B

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...

Alicia Gibbons 1B

"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.

Alicia Gibbons 1B

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.

Alicia Gibbons 1B

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!

Alicia Gibbons 1B

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, ...

Alicia Gibbons 1B

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.

Alicia Gibbons 1B

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.

Alicia Gibbons 1B

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.

Alicia Gibbons 1B

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?

Alicia Gibbons 1B

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...

Alicia Gibbons 1B

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 ...

CHEMISTRY COMMUNITY

Search found 31 matches

Re: Negative pH?

Re: Ka Calculations

Re: Ka Constant

Re: Dipole Moments

Re: Polar Bonds

Re: MO theory

Re: hybridization vs VSEPR notation

Re: Hybridized Orbitals

Re: Labeling Compounds

Re: Bonding

Re: Bond Strength

Re: Molecular Shape

Re: Resonance Hybrids

Re: Electronegativity

Re: Calculating Bond Lengths

Re: H Element

Re: Stable

Re: Calculation of bond length

Re: Ground vs Excited State

Re: orbitals and wave functions

Re: Ionization Energies

Re: Question on Midterm

Re: H bar

Re: Homework Problem

Re: E.23

Re: Test 1

Re: Units

Re: Naming Compounds

Formula Sheet?

Sig Figs: Addition and Subtraction

Re: HW F11