CHEMISTRY COMMUNITY

Janice Kim 3I

Torsional strain is caused by unfavorable electrostatic interaction. When molecules are eclipsed (as when the carbon atoms are in a planar geometry), the regions of electron density from the eclipsed atoms are closer together, thus leading to higher energy and less stability of the molecule. Steric ...

Janice Kim 3I

Dear Dr. Lavelle, Thank you so much for truly devoting yourself to giving your students the best academic experience we could possibly have! You exude such genuine passion for chemistry and it has positively influenced my learning experience. It is definitely refreshing to learn from a professor who...

Janice Kim 3I

Technically, every molecule can be named with IUPAC naming. However, naming becomes complicated without the use of common naming for instances such as multiple substituents on a substituent. This is why you should know and become familiar with the common names and what they would like like in line s...

Janice Kim 3I

Hey! When numbering multiple constituents, always aim for the lowest sum total. If there is equal numbering between constituents (for example 2,3 or 3,2) then apply the lowest number to the first alphabetical constituent, not including the prefixes.

Janice Kim 3I

Just look at whether there are electron deficiency or electron surplus. Molecules/Elements that have many electrons are most likely negatively charged (Nucleophiles). Electrophiles are electron deficient and are attracted to positive charges. The "obvious" comes from whether the molecule/e...

Janice Kim 3I

The reaction rate units is usually in the form mol L^-1 s^-1 (the time unit can vary - s, min, hr, etc). The rate constant depends on the order of the reaction. For example, if first order, the rate constant will be s^-1. You can find this by dividing the units of the reaction rate by the unit of th...

Janice Kim 3I

B is a product so the concentration of B increasing means that more product is being formed. Since .018 M of B is formed, using stoichiometric calculations, 0.018M B(1 mol A/3 mol B) = .006M A is lost because reactant concentration lessens as products are formed and product concentration is increase...

Janice Kim 3I

When there is no solid available for either anode or cathode. A solid is needed as the electrode for the reaction to occur.

Janice Kim 3I

OIL RIG is a simple pneumonic device I use to remember the difference between Oxidation and Reduction. Oxidation Is Losing (OIL) and Reduction is Gaining (RIG). Oxidation loses electrons, and so the charge of an element increases. Reduction gains electrons, and this brings in more negative value, de...

Janice Kim 3I

Just think about voltage as a set measurement for certain reactions. For instance, 2 Ag+ (aq) + 2 e- ------> 2 Ag (s) will have a certain voltage value. It does not matter how much of the reactants or products there are. It is a set measurement independent of the amount.

Janice Kim 3I

If the pressure is not constant, you are calculating the work for a reversible pathway. If you are in isothermal conditions (temp is constant) and you have a system that is being compressed with changing volume, the work expression would be -nrtln(V2/V1), where V2 is the final volume and V1 is the i...

Janice Kim 3I

Yes, the reversible pathway calculates the maximum value for work. However, most reactions, including biological reactions, use the irreversible pathway because it is more efficient and quicker.

Janice Kim 3I

This reaction is exothermic, meaning that the products are at a lower energy state than the reactants are. Usually, molecules will want to achieve the lowest energy state possible, and in this reaction, exactly that is happening. This reaction was favorable because it happened by itself, making it a...

Janice Kim 3I

Free expansion is saying that the particles, let's say from a reaction, is diffusing outwards freely. There is no work involved because these particles do not need to exert any energy (do work) to freely expand.

Janice Kim 3I

If pressure is held constant, q will have a subscript p (qp), making it interchangeable with delta H.

Janice Kim 3I

To give an example, we used kj/mol for the standard enthalpy of formation of ethanol for the example (page 17 of the course reader) because the definition of the standard enthalpy of formation has to do with 1 mol of the product that was formed from the reactants. The same goes for the second exampl...

Janice Kim 3I

Writing out the two steps for polyprotic acids is usually very helpful in visualizing what cancels out and what is added together. However, if you are just finding the K value for the overall equation, you can just multiply the individual Ka or Kb values.

Janice Kim 3I

Identifying a ligand as polydentate has two criteria. 1) The ligand must have at least 2 atoms that have lone pairs. This can be found through simply drawing the Lewis structure. 2) The atoms must be in the correct geometry to bind to the Transition metal cation in more than one place at the same ti...

Janice Kim 3I

Molecular Orbital Theory gives us more understanding of molecules we may not be able to know just through Lewis structures. It mainly gives us context on bond strength and magnetic properties. We can figure out the bond order through MO theory, and the higher the bond order, the stronger the bond. W...

Janice Kim 3I

The greater the bond order, the greater the stability of the molecule. For example, O2+ has a bond order of 2.5. When drawing out the Lewis structure for O2+, the 2 indicates a double bond and the .5 indicates a resonance structure. Double bonds are shorter, and thus stronger. If the bond order was ...

Janice Kim 3I

Hybridized orbitals allow atoms to have enough orbitals to bond with unpaired electrons. For example, the s and p orbitals will combine to form a new shape that allows the atom to bond with electrons. Carbon only has two unpaired electrons, but with the hybridized orbital sp^3, Carbon is able to hav...

Janice Kim 3I

I usually draw out the lewis structure and determine from there. If the central atom of the lewis structure has all bonding pairs (ex. linear, trigonal planar, tetrahedral, etc.) and all atoms that are bonded to the central atom are the same, the molecule is non-polar because the equal and opposite ...

Janice Kim 3I

It's better to understand that usually when the atom, more specifically the central atom, has an expanded octet, we need to utilize a hybridization beyond sp3. For example, XeF4 has an expanded octet and a hybridization sp^3d^2 because it has 6 electron density regions. Molecules such as XeF4 are pr...

Janice Kim 3I

If the electronegativities are given, the calculated difference in electronegativity for the molecule can determine whether the molecule is ionic or covalent. However, if the numbers are not given, the trends for electronegativity or polarizability based on the size of the atoms and charges(if it is...

Janice Kim 3I

It is safe to assume that whenever you see a single bond, it is a sigma bond because sigma bonds overlap two orbitals end to end, creating one single bond. There is only one overlap, and within this overlap is the single area of electron density. This one overlap gives you a single bond.

Janice Kim 3I

Px, Py, Pz are the different orbitals that are within the p subshell. Each one is a different orientation and each is linked to a different number for the magnetic quantum number m_l. For example, let's say n = 2. Then l = 0, 1. For l = 1 (the p orbital), m_l = -1, 0, 1. These three numbers correspo...

Janice Kim 3I

Resonance is when there are delocalized electrons within a molecule. This means that the bonding of the atoms within the molecule cannot be expressed with exactly one Lewis structure. For example, in NO3-, N has one double bond with one O in structural format. In actuality, the delocalized electrons...

Janice Kim 3I

The work function and the threshold energy both refer to the energy required to eject an electron from the metal surface. In the formula, E(photon)=E(energy remove electron) = E(excess), the E(energy remove electron) is the amount of work that needs to be put in the system in order to eject the elec...

Janice Kim 3I

When you execute the DeBroglie equation with the mass of something like a baseball or car, the resulting wavelength is so extremely small that it is physically impossible to detect. All matter has wavelike properties, but we can only notice these wavelike properties for very small objects with high ...

Janice Kim 3I

The speed of light is what we can compare to in terms of velocity. The answer cannot be reasonable if the speed is greater than the actual speed of light. It is similar to the concept of comparison when we are calculating the uncertainty in velocity. If the uncertainty is greater than the speed of l...

Janice Kim 3I

Even though we cannot literally see that something like a car would have wavelike properties, all matter has wavelike properties. However, we can only notice or detect these wavelike properties in extremely small moving objects such as electrons.

Janice Kim 3I

The shorter the wavelength, the higher the frequency. Shorter wavelengths mean increased energy for each photon in a beam of light. In order to reach the threshold of energy to eject electrons from the metal, the photons must have enough energy. If the photons in a beam of light do not have enough e...

Janice Kim 3I

I took AP Chem in my junior year and I have a couple of review books and notes that I brought with me that actually really supplemented my learning while watching the modules and taking the pre/post assessments. I recommend that you refresh your memory with notes or even specific youtube videos. Wat...

CHEMISTRY COMMUNITY

Search found 33 matches

Re: Difference Between torsional strain, steric strain, and bond angle strain

Re: Saying Thank You to Dr. Lavelle

Re: How much of Common naming do we need to know for Quiz 3?

Re: Numbering

Re: Electrophile Vs. Nucleophile

Re: Units for Reaction Rate and the Rate Constant

Re: 15.29

Re: Galvanic Cells

Re: Oxidation [ENDORSED]

Re: Intensive Property

Re: question on U=q+w equation

Re: Amount of work done

Re: "Favorable" chemical reaction

Re: Irreversible process

Re: relationship between delta H and q [ENDORSED]

Re: Units of Reaction Enthalpies

Re: Writing Reaction Equation for Polyprotic Acids/Bases

Re: Identifying Polydentates? [ENDORSED]

Re: What is MO theory for? [ENDORSED]

Re: Bond Order

Re: Hybridization

Re: Polar and Non-polar bond

Re: Hybridization Beyond sp3

Re: Electronegativity in Quiz 2 [ENDORSED]

Re: VSEPR Diagram

Re: Px, Py, Pz [ENDORSED]

Re: Resonance [ENDORSED]

Re: Work Function and Threshold Energy [ENDORSED]

Re: Conceptual Question on DeBroglie

Re: Post Module Question [ENDORSED]

Re: Wavelike Properties? [ENDORSED]

Re: Photons

Re: Rusty on High School Chem [ENDORSED]