CHEMISTRY COMMUNITY

Cynthia Rodas 4H

Hydrogen bonds are stronger than dipole-dipole. The strength for intermolecular forces arranged from lowest to highest is London forces, dipole-dipole, H-bonding, and ion-dipole.

Cynthia Rodas 4H

The suffix -ate is added to the metal when the complex is anionic. So if the overall charge of the complex is negative like it was in Part C, the name of cobalt became cobaltate.

Cynthia Rodas 4H

The elements outside of the bracket affect the oxidation number because in order for the coordination compound to be neutral, the charges of the elements within the bracket and outside of the bracket must cancel each other out.

Cynthia Rodas 4H

Whenever a complex is anionic, meaning that it has an overall negative charge, the ending of the metal will be -ate.

Cynthia Rodas 4H

The prefixes -bis, -tris, and -tetrakis are added when the ligand already has a Greek prefix or if the complex is polydentate.

Cynthia Rodas 4H

A chelating ligand is when a ligand has more than one bond with the metal atom.

Cynthia Rodas 4H

Lewis acids are electron acceptors and Bronsted acids are proton donors. Lewis bases are electron donors and Bronsted bases are proton acceptors.

Cynthia Rodas 4H

BF3 is a Lewis acid because Boron has an empty p-orbital. This means that it can accept an electron pair, which by definition is a Lewis acid. The new bond would be formed with the Boron.

Cynthia Rodas 4H

As far as I know, the Final will be cumulative. However, there will be more of an emphasis on the topics after the midterm. Just make sure you know how to do everything mentioned on the outlines.

Cynthia Rodas 4H

Debora Fernandez Clemente_ 4H wrote:How do you calculate the oxidation number of the metal in a complex?

To calculate the oxidation number of the metal in a complex, you would use the equation:

(# metal atoms)(oxidation number of the metal)+ $\sum$ (# each ligand)(charge of each ligand)= charge of ion

Cynthia Rodas 4H

Ligands are Lewise bases (electron donors) that are attracted to the central atom since it is a Lewis acid and transition metal. So the ligand can be either an ion or compound.

Cynthia Rodas 4H

Melting points are determined based on their intermolecular forces. The more intermolecular forces it has, the more energy it would take to break bonds, resulting in a higher boiling and melting point.

Cynthia Rodas 4H

Technically, sigma and pi bonds do affect bond length and bond angles. However, the change is minimal so it therefore doesn't have much influence on the molecular shape. Furthermore, the VSEPR model counts single, double, and triple bonds as one region.

Cynthia Rodas 4H

Single bonds are all sigma bonds.
Double bonds are all sigma and pi bonds.
Triple bonds are all sigma and 2 pi bonds.

Cynthia Rodas 4H

Electronegativity is basically how much an atom attracts electrons. So if there is a high electronegativity difference, it means that there is a strong bond and that the bond length will be shorter.

Cynthia Rodas 4H

Bond angles get smaller with more lone pairs at the central atom due to lone pair repulsion. Lone pairs want to be far away from the other elements so it will repel the other bonds away from it, causing a decrease in bond angle.

Cynthia Rodas 4H

The periodic trend for electronegativity is that electronegativity decreases as you go down the periodic table and electronegativity increases as you go from left to right of the periodic table (excluding noble gases). With that being said, although Ba and Be are the same distance from Br in terms o...

Cynthia Rodas 4H

An expanded octet can occur if the atomic number of the central atom is 11 or more. This is because elements of the third principal energy level and above have a d-oribital that it can fill.

Cynthia Rodas 4H

You would use formal charges to determine which way to write a Lewis structure that is most stable. However, Lewis structures are 2-D and only portray which atoms are bonded together rather than in which position (such as horizontally or vertically). In order to determine it's molecular shape, you w...

Cynthia Rodas 4H

My TA said that Test 2 would consist of all the material we covered after Topic 2D. In regards of memorizing, I would highly recommend memorizing the different molecular shapes and bond angles since I highly doubt that they would provide us with that kind of information.

Cynthia Rodas 4H

Electron affinity refers to the amount of energy released when an electron is added to an atom. Electronegativity, on the other hand, refers to how much an atom attracts electrons. So an easier way to think of it is electron affinity is how much they want electrons whereas electronegativity is how m...

Cynthia Rodas 4H

Ionization energy refers to the minimum amount of energy needed to remove an electron whereas electron affinity is the amount of energy released when an electron is added.

Cynthia Rodas 4H

Are the cations usually Lewis acids and the anions usually Lewis bases? Yes! So Lewis acids are electron pair acceptors and Lewis bases are electron pair donors. Ions with a positive charge signifiy that it can accept a pair of nonbonding electrons. Ions with a negative charge signify that it can d...

Cynthia Rodas 4H

My TA said that we would be getting our midterm grades by Wednesday on 11/13.

Cynthia Rodas 4H

It is possible, however the differentiating factor between the two types of bonds comes down to their physical and chemical properties. For example, covalent bonds are typically between two nonmetals whereas ionic bonds are typically between a metal and a nonmetal. You could also observe their diffe...

Cynthia Rodas 4H

Ionic bonds are usually between a metal and a nonmetal. Covalent bonds, on the otherhand, are typically between two nonmetals. Another way to differentiate is by looking at the electronegativity difference. If the electronegativity difference is greater than 2, then it is an ionic bond. If the elect...

Cynthia Rodas 4H

In order to find the amount of power produced in watts, you would use the equation: E = \frac{hc}{\lambda } This equation is used to help you find the energy per photon. From here, you would plug in Planck's constant (6.62608 x 10-34 J.s), the speed of light (2.998 x 108 m/s), and the given waveleng...

Cynthia Rodas 4H

Part a: So in order to convert the answer from meters to nanometers, you would try to cancel out the meters in order to get nm by itself. For example: (4.22 * 10^{-7} m) * (\frac{1 nm}{10^{-9} m}) This would leave the result as 422 nm. Part b: This follows the same concept as Part a,...

Cynthia Rodas 4H

Yes! Great start so far. From here, you would try to get \frac{1}{n_{2}^{2}} by itself by moving all other values to the other side to get: \frac{-2.922 * 10^{15}}{3.29 * 10^{15}} + 1 = \frac{1}{n_{2}^{2}} From here, you would solve the left side which is approximately: 0.11185 = \frac{1}{n_{2}^{2}}...

Cynthia Rodas 4H

I don't believe this concept will be on the test. Just focus on the learning objectives that Lavelle listed in each outline. After looking at the last test, I'm pretty sure he would test us on problems that are similar to the homework problems.

Cynthia Rodas 4H

Ionic bonds consist of ions in a ratio that result in electrical neutrality. They consist of a metal (cation) and a nonmetal (anion). Metals are cations since they give electrons, whereas nonmetals are anions because they gain electrons. On the other hand, covalent bonds consist of electrically neut...

Cynthia Rodas 4H

To calculate the energy of a photon, you would use E = hv. However, some problems might require you to use E = hc/lambda instead.

Cynthia Rodas 4H

Since the problem is asking you to find the amount of power produced in watts, you would use the equation: E = \frac{hc}{\lambda } This would help you find the energy per photon. So then, you plug in Planck's constant (6.62608 x 10 -34 J.s), the speed of light (2.998 x 10 8 m/s) and the given wavele...

Cynthia Rodas 4H

You can use the octet rule, but I personally like to look at bonding preferences, such as how hydrogen has one bond, oxygen has two bonds, nitrogen has three bonds, and carbon has four bonds.

Cynthia Rodas 4H

Covalent bonds can only be formed by nonmetals, and metals are more likely to form ionic bonds. Remember that metals often times become cations because it is easier for them to give up electrons. Non metals have high ionization energy. Nonmetals can also form ionic bonds, right? An ionic bond is ty...

Cynthia Rodas 4H

This problem in particular requires the use of two equations: c= (wavelength)(frequency) E = h v E represents the energy of a photon h represents Planck's constant (6.626 x 10[/sup]-34[/sup] J * s) v represents the frequency of radiation Since the first and third parts of the problem provide you wit...

Cynthia Rodas 4H

Victoria Otuya 4F wrote:Is hz the same as s-1?

Hz is one cycle per second (1/s) and it is the same as s^-1. It just becomes s^-1 since it is read in the numerator rather than the denominator.

Cynthia Rodas 4H

I think the best way to approach this problem is to reason through each choice to see why each one does or doesn't happen. So for example: (a) The speed of radiation doesn't decrease as the frequency of electromagnetic radiation decreases since it is a constant (c= 2.998 x 10 8 m/s). (b) The wavelen...

Cynthia Rodas 4H

The equation we will be using to solve this problem is: \nu = R (\frac{1}{n_{1}^{2}}- \frac{1}{n_{2}^{2}}) So the problem states that the spectral line 102.6 nm is in the ultraviolet spectrum of atomic hydrogen. We already know that the Lyman series is the set of lines in the ultraviolet reg...

Cynthia Rodas 4H

c = \lambda \nu The standard units are: c= Speed of Light in meters per second (m/s) \lambda = wavelength in meters (m) \nu = frequency in Hertz (Hz or 1/s) However, the wavelength can be in other length units if the problem states otherwise. In that case, you would have to use dimensional analysis.

Cynthia Rodas 4H

Parts (a) and (b) use the equation m= n * M.
m- mass of the sample
n- amount in moles
M- molar mass

Part (c) uses the equation n = N/N_A
n- amount in moles
N- number of objects
N_A- Avogadro's constant

Cynthia Rodas 4H

Combustion refers to a chemical reaction that includes burning in air. The most basic set-up is usually:
$CH_{4} +2O_{2}\rightarrow CO_{2} + 2H_{2}$ O
The main point is that the products will always include CO₂ and H₂O. It's just a matter of balancing the equation based on what is given to you.

Cynthia Rodas 4H

The law of conservation of mass states that atoms are neither created or destroyed. Therefore, if a chemical reaction occurs, then the chemical formula will result in the reactants and/or products being multiplied by factors that result in the same number of atoms.

Cynthia Rodas 4H

The actual yield will most of the time be less than the theoretical yield because of competing reactions, measurement errors, and/or limiting reactants. The theoretical yield is the maximum quantity of product that can be obtained from a chemical reaction.

Cynthia Rodas 4H

If you want more practice problems aside from the ones Lavelle assigned, I would highly recommend participating in the Step-Up Program and Workshops. Some clubs also provide their own Peer Learning Groups for certain subjects. Khan Academy is also a great resource to use.

Cynthia Rodas 4H

Empirical formulas show the relative number of atoms a molecule has. The ratio can then be used to determine the molecular formula, which is the actual number of atoms in a molecule. However, there are some cases in which the empirical formula is also the molecular formula.

Cynthia Rodas 4H

Hey, I was just curious. What does Avogadro's number actually represent? Thank you guys. :) Avogadro’s number is referring to the pure number “6.0221 x 10^23,” which is unitless. On the other hand, Avogadro’s constant is a constant with units, 6.0221 x 10^23 mol^-1, which represents the number of o...

Cynthia Rodas 4H

When balancing equations how do you determine what to balance first? My TA recommended that we start with balancing the elements that appear the least in a chemical equation. For example: C_{4}H_{10} + O_{2} \rightarrow CO_{2} + H_{2}O You would start with either the Carbons or Hydrogens since they...

Cynthia Rodas 4H

I would recommend using the exact values provided by the periodic table and then use the significant figure rules at the end of the calculation to round off properly.

Cynthia Rodas 4H

I just looked over Dr. Lavelle’s worksheet regarding significant figures. According to Lavelle, one of the rules for rounding off is to wait until the end of a calculation. For calculations using multiplication and division, your answer should have the same number of significant figures as the value...

Cynthia Rodas 4H

Thank you so much for sharing your experience as a medical student! It is truly inspiring to hear about all the things you have accomplished over the past three years. I am also pursuing a career in medicine. However, I am a first-generation student and I have no family members or friends who are in...

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