CHEMISTRY COMMUNITY

jvera4b

No, hydrogen bonding is a type of intermolecular force not a type of acid base reaction.

jvera4b

Using the Lewis Structure then you can determine which is the central atom (or the one being asked for in the question) and look at the number bonds. The first bond will always be a sigma bond, a double bond has a sigma and pi, and a triple bond will be one sigma and two pi.

jvera4b

Nothing for positive only if the ion is an anion (negatively charged).

jvera4b

Yes, lewis acid accepts protons and lewis base is the one that gives. A Bronstead acid donates a H+ while a base will a accept the H+.

jvera4b

Ka is only given for weak acids because they don’t dissociate completely so just assume complete dissociation for strong acids.

jvera4b

Lectures are not bruincasted and slides are also not uploaded, but if you want to review past topics Dr. Lavelle does have the Audio-Visual Focus-Topics on the class website.

jvera4b

Study your lecture notes since in past finals an example from lecture was asked about. I would also recommend going to review sessions whenever you can since there is a lot of material that we must review.

jvera4b

Liliana Aguas 3G wrote:What day of lecture notes was this topic mostly covered?

I believe November 20.

jvera4b

Acids and bases are covered in Fundamentals J and Chapter 6.

jvera4b

You find the chrage of cobalt by first calculating what the total charge of the hexaammine is (0 since NH3 is neutral) and then the total charge of the complex ion (3+) in this problem that would mean that the charge of cobalt is 3+ hence the answer being hexaammine cobalt(III).

jvera4b

(Bronstead) acids are proton donors while (brontead) bases are proton acceptors.

jvera4b

Yes the first bind is always a sigma bind while all other bonds formed will be pi bonds.

jvera4b

A strong acid completely ionizes in a solution, producing more protons in the solution.

jvera4b

A ligand is a molecule which is attached to a central metal. Ligands make up the coordination sphere.

jvera4b

The first bond made is always a sigma bond while any other bonds made will be pi. (A double bond consists of one sigma and one pi bond. A triple bond consists of one sigma and two pi bonds)

jvera4b

Does anyone know if the HW for both weeks is due on week 10 for all discussions or only those after Wednesday?

jvera4b

The electron pairs are in the "trigonal planar" part of the molecule because that forms the shape with the least amount of repulsion.

jvera4b

You can identify the type of intermolecular forces by looking at the dipole moments of the molecules.

jvera4b

The terms are interchangeable since they mean the same thing, just know what they are and you should be fine.

jvera4b

A bent molecule will have a lone pair, or two in the case of AX₂E₂, on the central atom as opposed to a linear which has no lone pairs around the central atom.

jvera4b

Yes, hydrogen bonding a type of dipole-dipole interaction.

jvera4b

Yes, so that, if asked, you can make comparisons between the angles of different shapes.

jvera4b

I don't think so, the only topics Dr. Lavelle said would be on the test from Monday's lecture are sigma and pi bonds.

jvera4b

Since electron's are constantly moving, there is potential for a temporary dipole to be present (the electrons would happen to be more towards one side).

jvera4b

Have we gone over sigma and pi bonds yet? Do we have any more information about what exact material will be tested? Lavelle said he would discuss sigma and pi bonds on Monday. ... so are sigma and pi bonds going to be on the test? I think the TAs said they were trying to have the tests done by Sund...

jvera4b

When drawing Lewis structure you should focus on the formal charges that make the molecule the most stable. Since Lewis structures are two-dimensional models the placement of atoms around the central atom isn't the most important aspect when drawing them.

jvera4b

The geometry of a molecule only looks at the number of electron dense areas. However, when looking at the shape you take into account how the lone pairs around the central atom will affect the overall three-dimensional shape because they cause elctron repulsion.

jvera4b

They have to sum up to the overall formal charge. Each atom's formal charge may vary but they all have to add up to the same overall charge.

jvera4b

Yes, the exam will cover the material of all the quarter.

jvera4b

Between ion-dipole and h-bonding which is the stronger molecular force? I thought it was ion-dipole because there is a full formal charge however I am not sure if this reasoning is correct.

jvera4b

An induced-dipole occurs when a temporary dipole occurs causing/inducing a dipole in a nonpolar molecule. On the other hand, a permanent dipole occurs when a polar molecule is always more elctronegative than the other molecule.

jvera4b

Lone pairs still affect molecular geometery because they still cause repulsion amongst electrons of other atoms.

jvera4b

E is the energy of the photon and the work function is the threshold energy, the energy needed to remove an electron.

jvera4b

E=hv would be used if the frequency is given or you can find it by manipulating c=(lambda)v, E=pc would be used when the momentum cana be found such as when the velocity or momentum is given.

jvera4b

A resonance structure would be possible ways to draw the Lewis structure of a molecule which has resonance, multiple bonds can be drawn in different locations, the actual structure would be a blend of all the different structures.

jvera4b

Atomic radius increases down a group and decreases across a period(from left to right). Electronegativity decreases down a group and increases across a period (left to right).

jvera4b

No, resonance structures only occur when bonds can be moved to multiple locations.

jvera4b

Shorter bonds are stronger than longer bonds since short bonds involve more elctrons, this which causes the nuclei to be more attracted. Conversely, longer bonds don't make nuclei as strongly attracted and therefore result in them being easily broken.

jvera4b

Resonance structures are possible ways that the Lewis structure can be drawn (when there are multiple way to arrange electrons but the arrangement of the atoms doesn't change). A better representation of the structure would be a resonance hybrid/ an average of all the possible structures.

jvera4b

When you draw a lewis structure you have to pay special attention to the valence electrons in each atom; they help determine if there are single/double/triple bonds. There is normally a center atom, and that is normally the atom that has the lowest ionization energy. For bonds (when the molecule is...

jvera4b

A lone pair would be the dots that aren't bonded but are still surrounding the element (those which don't have a line connecting to another element). The L in the formal charge equation would be the number of lone electrons for the element you are calculating it for.

jvera4b

You know you can draw a chemical structure in several ways you can see multiple bonds in different locations, this is known as resonance. Resonance structures are indicator for more stable structures.

jvera4b

A bond represents that two electrons are being shared by the elements. Two bonds would mean that there are four electrons shared by the elements.

jvera4b

In the syllabus it lists that the topics in the Chemical Bonds unit are: (ionic and covalent bonds; Lewis structures of inorganic, organic, and biological compounds; resonance structures; formal charge; Lewis acids and bases; coordinate covalent bonds; octet rule exceptions; ionic versus covalent b...

jvera4b

I believe Lavelle mentioned this odd configuration along with one other one that I am forgetting right now. He said that these two configurations are anomalies that we just have to memorize without much further explanation. Some areas of chemistry (and science in general) are proven experimentally ...

jvera4b

Can we do problems from both sections or must they be exclusively from one?

jvera4b

An octet would be an atom that has 8 valence electrons, noble gases all have octets. The octet rule refers to elements wanting to bond in order to reach eight valence elctrons and stability, the exceptions are H, He, Li, and Be.

jvera4b

The central atom is the one with the lowest ionization energy(decrese down a group and increase across a period).

jvera4b

Resonance doesn't mean that the molecule has different structures, rather that the Lewis structure for it can be arranged in various ways (not just three).

jvera4b

Unless otherwise specified by the question, you can just write 1s^2 2s^2 2p^3.

jvera4b

The thrid quantum number tells us the specific orbital in a subshell, such as whether the electron can be foud in px py or pz.

jvera4b

All equations and constants are given in the equation sheet, however derivations of equations are not given so its safer (and better) to know what each variable corresponds to in case a question on the exam requires it and to gain a better understanding of the concepts.

jvera4b

Elements like neon meet the octet rule meaning they have eight electron in its valence shell. The octet rule states that all elements want to have eight electrons in their valence shell, so neon and other elements like it aren't as likely to bond with other elements.

jvera4b

Yes, according to my TA we will get the equation sheet from the first test for every test.

jvera4b

The speed of light is a constant (2.998 x 10^8) as others have mentioned 3.0 x 10^8 is sometimes used, however it would be better if you used 2.998 x 10^8 so that your sig figs at the end are correct.

jvera4b

The molarity is given by amount of solute molecules (moles) divided by the volume of the solution (liters), the molar amount of solute would therefore be the numerator.

jvera4b

By definition a limiting reactant is the reactant that will be completely consumed. There will be more of one than the other causing the reaction to stop there. Whatever is left of the reactants would be labeled as excess reactants. If the reactants are equal then they will not limit each other, rat...

jvera4b

You can multiply the number of kilograms by 1000 grams since that is the conversion number not in scientific notation (1kg=1000g).

jvera4b

Just try to estimate what would number multiplied by .16 is close to 1. To my understanding, you simply have to be really close to a whole number. In this example, 2.16 * 6 = 12.96 which is close to 13. However, if the factor you use gives you (in the example lets say 3) a result (6.48) that is not ...

jvera4b

You can find atoms, molecules, and formula units using Avogadro’s constant because scientists have determined 6.022x10^23 of atoms/particles/ molecules is equal to 1 mol. You can use the substance’s molar mass to calculate what is being asked for. For example if you were given to find the mass of an...

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