CHEMISTRY COMMUNITY

Katie Sy 1L

expansion joints on bridges and overpasses. for example, a bridge deck gets longer in the heat of summer and contracts in the cold of winter

Katie Sy 1L

it relates the change in the equilibrium constant, Keq, of a chemical reaction to the change in temperature, T, given the standard enthalpy change, ΔH, for the process.

Katie Sy 1L

it's a spontaneous reaction because ice will melt by itself, not needing any external heat to be added to the system, which is why deltaG is negative

Katie Sy 1L

i think just kinetics since that's what we covered this week in class

Katie Sy 1L

attending study sessions are super helpful. and if you find a specific topic difficult, i recommend searching it on youtube and watching a video where they do practice problems

Katie Sy 1L

i would assume so since these type of questions were asked on the homework

Katie Sy 1L

liquids can be listed. make sure to separate them from the other phases in the diagram

Katie Sy 1L

you can't predict it based on just temperature. you would need enthalpy or entropy or both

Katie Sy 1L

you want to flip one of the half reactions so the electrons from each half reaction are able to cancel out. when you flip a half reaction, the sign of that cell potential will switch

Katie Sy 1L

we don't need to memorize any, they'll be given to us

Katie Sy 1L

Higher volume leads to greater entropy because the larger the volume the more ways there are to distribute the molecules in that volume; the more ways there are to distribute the molecules (energy), the higher the entropy The entropy of a system decreases with an increase in pressure. This is due to...

Katie Sy 1L

I'm not sure but I think it just means reaction

Katie Sy 1L

it doesn't matter what the units are as long as you keep them consistent for each molecule in the equilibrium equation

Katie Sy 1L

no you don't need to do it twice. just be consistent in either using the volumes or pressures

Katie Sy 1L

materials with more atoms per unit volume will generally have higher heat capacities on a per-mass basis and larger molecules will have a larger heat capacity on a per-mole basis

Katie Sy 1L

to find the energy density in kJ/L, divide the amount of energy with the mass of one mole of TNT(227.14 g/mol) and then multiply it by the density of TNT (1.65 g/cm^3)

Katie Sy 1L

in the solution manual, it shows the answers in Joules/moles

Katie Sy 1L

you want to find Ccal so take 22.5 kj and divide that by the difference in temperature. your answer will be in kJ/C

Katie Sy 1L

find the value of work by using the equation w=-Pressure * change in the volume. then to get deltaU, take q (given in the problem) and add it with work

Katie Sy 1L

An extensive property depends on the amount of matter while an intensive property depends on what the type of matter is. an example of an extensive property would be volume while an intensive property would be hardness

Katie Sy 1L

yes because bonds are being made, causing energy to be released into the surrounding

Katie Sy 1L

i don't think we'll need to know how to derive it but just know the relationship. but it's pretty simple to derive it so i would know it to just help you out later on

Katie Sy 1L

i don't think there is one but just make sure to know the relationship between pka with ka and pkb with kb and you can use an ICE box to find the concentration to find the ka or kb values

Katie Sy 1L

it is 10^-14 only when water is at a constant 25 degrees C

Katie Sy 1L

yes because of the 2 hydroxide ions

Katie Sy 1L

you only include gases and not solids or liquids because solids/liquids concentrations are constant throughout the reaction

Katie Sy 1L

for ICE charts, use concentration values

Katie Sy 1L

If they're not gas, you can use the value of 1 as a replacer

Katie Sy 1L

Lavelle has a link on his website that addresses any textbook mistakes, trying checking there

Katie Sy 1L

Kp is for partial pressures, so only involves gases

Katie Sy 1L

positive refers to an input of energy vs negative would be a release of energy

Katie Sy 1L

lyndon's review session on tuesday should also have some good final practice

Katie Sy 1L

Sulfur, phosphorus, silicon, and chlorine are some common ones and boron and aluminum can form compounds in which they have six valence electrons

Katie Sy 1L

carbon's three bonding regions means there is one s orbital and 2 p orbitals (sp2)

Katie Sy 1L

i believe so and possibly some past topics may be included but i'm not sure about that

Katie Sy 1L

yeah it will be 180 degrees if it's linear

Katie Sy 1L

yeah i believe so

Katie Sy 1L

Yes I believe we will need to recognize and name shapes

Katie Sy 1L

in addition to knowing the shapes, also know the angles associated with them

Katie Sy 1L

they're inversely related so a molecule with a greater electronegativity will have a lower polarizability

Katie Sy 1L

i tried to focus on doing problems based on the lectures we've had the past week

Katie Sy 1L

we're going to learn shape soon and then the placement will matter, but based on what we've learned so far, we don't have to have a certain placement

Katie Sy 1L

i don't think it's required unless specified. but i always do because i find it to be super helpful to figure out the most stable form of a molecule

Katie Sy 1L

formal charge being 0 is more important because don't forget about elements that have octet exceptions

Katie Sy 1L

you will know whether you'll need to add a double or triple bond depending if it changes the formal charge closer to 0. this means the atom will be more stable

Katie Sy 1L

yes the overall formal charge of the atom will equal the total of the formal charge of each element in the atom

Katie Sy 1L

This is the closest noble gas, using this allows for the electron configuration to be shorter in length to write

Katie Sy 1L

The book is using the Heisenberg equation that is h with a dash over 2pi so that's why it's being multiplied by 2. I believe so?

Katie Sy 1L

Yup! It's 4f because n=4 and l=3 which refers to the f block

Katie Sy 1L

It's because you want to complete the 4d orbital before moving onto the 5s orbital. A full 4d orbital contains 10 electrons.

Katie Sy 1L

Actual Yield is the value the problem should give you. It's the amount actually produced in the experiment. Theoretical yield is the amount you should expect to produce while using information from the balanced equation and the starting amount of the reactant.

Katie Sy 1L

I believe we don't need to know how to name compounds on the first test. However, we will eventually need to know them. I think the best way to learn them is just memorize them, make flashcards on quizlet. My TA said eventually, after doing a lot of practice problems,we'll start memorizing the names...

Katie Sy 1L

Spectral Line Diagrams are mainly used to identify molecules or atoms from their exact, unique placement of their particular spectral line. It's another way to analyze frequencies in addition to the electromagnetic spectrum.

Katie Sy 1L

I tend to just use the whole number listed on the periodic table to make sure my answers are exact as possible, but if it's a super long number, I usually stop after 3 decimal places

Katie Sy 1L

The "t" refers to the unit. In this case, it means metric ton (aka 1000 kg)

Katie Sy 1L

I tend to use exact calculations throughout the problems ensuring there are no rounding errors by the end. Once I get my answer, then I take significant figures into consideration. I find this provides the most accurate answer.

Katie Sy 1L

Yes these two notations mean the same thing. I believe it is a personal preference for which version to use. In some cases, it might be easier to type one out than the other. The negative 1 in the numerator means it will move to the denominator.

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