CHEMISTRY COMMUNITY

CalvinTNguyen2D

For each different order, the rate constant will have its own units. If you can determine the units that the constant has, you can deduce the reaction order.

CalvinTNguyen2D

q=mcdeltaT should be used to solve these problems. Remember to take into account phase shifts as well, as they take up a significant portion of the heat energy needed to heat up a substance.

CalvinTNguyen2D

I loved Chemical Equilibrium! I thought it was pretty straightforward and for some reason I found it fun to imagine how equations would shift around depending on the reactant/product concentrations.

CalvinTNguyen2D

In a zero order reaction, the rate of the reaction does NOT depend of the concentration of the reactant; the rate remains constant throughout the entire reaction.

CalvinTNguyen2D

There was an e-mail that just got sent saying it would be 3 and a half hours from 11:15 AM to 2:45 PM.

CalvinTNguyen2D

All reactions will have some sort of activation energy. What determines if a reaction is exothermic or endothermic is the final value of the amount of energy still within the system.

CalvinTNguyen2D

To cancel out the electrons, multiply the half-reactions to get equal amounts of electrons on both sides and then add the reactions together.

CalvinTNguyen2D

By using these two equations, we can set both of them equal to each other, and manipulate them to derive the Van't Hoff Equation.

CalvinTNguyen2D

Yes, Zero-Order Reactions depend solely on the rate constant, and do not involve any other factors.

CalvinTNguyen2D

Molecularity is number of particles as a reactant that participate in a reaction.
One - unimolecular
Two - bimolecular
Three - termolecular

CalvinTNguyen2D

K values are used when the reaction is currently in equilibrium. However, if the reaction is not in equilibrium, the value Q is used instead.

CalvinTNguyen2D

Yes. The electrolysis supplies the external energy that can be used to drive a non spontaneous reaction.

CalvinTNguyen2D

When E is positive, the reaction will be spontaneous. However, when E is negative, the reaction will be nonspontaneous.

CalvinTNguyen2D

OH- and H+ are used to balance basic and acidic reactions in half reactions, respectively.

CalvinTNguyen2D

You will almost always be using Kelvin in equations and calculations; in terms of the gas constant, it is measured in Kelvin rather than Celsius.

CalvinTNguyen2D

Gibbs free energy allows us to determine if an equation is spontaneous or not.

CalvinTNguyen2D

Work, as viewed through the lenses of chemistry, is positive when it is being done ON the system. Therefore, work is negative when the system itself is doing work on the surroundings.

CalvinTNguyen2D

Test 2 will include the second page of Thermodynamics and the entirety of electrochemistry!

CalvinTNguyen2D

With these initial concentrations and the Kc value, you are able to determine which way the reaction shifts by calculating Q. Form there, compare Q to Kc to determine the reaction direction.

CalvinTNguyen2D

Because inert gases are not technically a part of the equation, they have no effect on the reaction equilibrium.

CalvinTNguyen2D

To better understand the process of a redox reaction, it is recommended to split the reaction into an oxidation and reduction reaction. This lets us identify which species is oxidized and reduced, and also allows us to balance the redox reaction via the electrons.

CalvinTNguyen2D

Species that gain electrons are considered reduced, while species that lose electrons are oxidized.

CalvinTNguyen2D

Isobaric means constant pressure. Isochoric means constant volume. Isothermal means constant temperature.

CalvinTNguyen2D

The value of K in a reverse reaction is the inverse of the forward reaction. If the value of K in a forward reaction is K, then the equilibrium constant in the reverse reaction is 1/K.

CalvinTNguyen2D

Can someone explain 2 D? For some reason I'm not getting the right answer for the reaction quotient :( For 2D, remember that NH4HS(s) is not included in the reaction quotient, since it is a solid! The equation should just be Q = [H2S][NH3]! Make sure to convert the mols into MOLAR by dividing the m...

CalvinTNguyen2D

In adiabatic processes, heat is not transferred in or out of a system. Therefore, q is equal to 0, allowing us to determine w (work) from inference and deductions.

CalvinTNguyen2D

Closed systems will block the transfer of matter in and out of the system, but still permits the transfer of energy inside and outside of the system.

CalvinTNguyen2D

The midterm will cover Outlines 1 to the first page of Outline 4!

CalvinTNguyen2D

The problem asks for us to convert 0 degrees C ice into 45 degrees water. However, to do this, we need to melt the ice into water, which requires us to use the enthalpy of formation and a phase shift calculation. After that, we can calculate the energy required to heat 0 degrees water to 45 degrees ...

CalvinTNguyen2D

Vaporization requires significantly more energy to completely break the hydrogen bonds between the H2O molecules, rather than just slightly mobilising the water molecules by melting it from solid to liquid.

CalvinTNguyen2D

There are multiple different ways an equilibrium can shift- if reactants are added to a reaction, the reaction will naturally want to balance itself to fit the reaction constant and thus will create more products. The same applies vice-versa.

CalvinTNguyen2D

HF is actually not a strong acid, since fluoride is so electronegative that it does not want to dissociate in water. As a result, it does not have 100% ionization.

CalvinTNguyen2D

When Q is greater than K, the reaction will shift to the left. When Q is lower than K, the reaction will shift to the right.

CalvinTNguyen2D

Polar bears are unable to swim in water- they dissolve when they jump in.

CalvinTNguyen2D

Identifying different types of systems allows you to understand how the flow of energy is moving and determine how to calculate reaction energy; for example, it is extremely difficult to determine the heat lost or gained in an open calorimetry system.

CalvinTNguyen2D

Using bond enthalpies is going to be the least accurate, since bond enthalpies are found from an average of multiple different molecules.

CalvinTNguyen2D

Because the molecules of water are held together by hydrogen bonding, it takes a large amount of energy to break those bonds and change its phase; this energy is reflected in the gas phase with its high kinetic energy

CalvinTNguyen2D

Hess' Law states that the total enthalpy change of a reaction is the sum of all the individual changes within the reaction!

CalvinTNguyen2D

In an exothermic reaction, because the heat is technically treated as a "product", increasing the temperature would cause the reaction to shift towards the left.

CalvinTNguyen2D

The Midterm is on Feb 12th on Wednesday!

CalvinTNguyen2D

According to my TA, we should know:
1. Chemical equilibrium constant
2. ICE table
3. Le Chatelier’s Principle
4. Ideal Gas Law
5. Equilibrium for weak acid, base, pH calculation, quadratic equations.
6. Manipulations of Kc

Hope this helps!

CalvinTNguyen2D

In order to balance the equilibrium, as the partial pressure of CO is decreased, the partial pressure of CO2 must decrease as well and will shift to the left.

CalvinTNguyen2D

Solids and liquids do not affect the equilibrium in any significant way, and are not measured in concentrations; as a result, they are left out in K value calculations.

CalvinTNguyen2D

Ideal gas law is used to convert individual concentrations into partial pressures, and vise-versa. It's useful for expressing K in either Kc (concentration) or Kp (partial pressure).

CalvinTNguyen2D

I'm not 100% sure I understand the question, but relating to chemical equilibrium, Exothermic reactions will have heat as a "product" as they release heat during their reaction, while Endothermic reactions will have heat as a "reactant" as it absorbs heat during the reaction. Thi...

CalvinTNguyen2D

K is a constant that is calculated during equilibrium, but Q is the reactant quotient that is not calculated during equilibrium. Q is a good indicator of which way a reactant will be favored; if its less than K, then the reaction is favored forwards, and vice-versa.

CalvinTNguyen2D

K does not have any units associated with it, since it's just a ratio of different molecules and species.

CalvinTNguyen2D

K is calculated when the reaction is at equilibrium, but Q is not. Q is a great indicator to figure out which way the reaction is favored.

CalvinTNguyen2D

Kp is only used for gases, while Kc is used for concentrations. If needed, you can convert individual species from concentration to atm through PV=nRT

CalvinTNguyen2D

Hey! Here's some things that worked for me last quarter; Doing every single hw problem on the syllabus. They're all fantastic review of concepts and things that will be on the test, and some problems will be the exact same on these tests, midterms, and finals. Visiting chem community and browsing th...

CalvinTNguyen2D

It’s best to use the table they have in the textbook! For c, each Cl has one bonding site, so that would be 2. Each (en) has two bonding sites, and since there are 2, there would be 4 (en) bonding sites in total. All in all, that would be 6! For d, (edta) has a total of sic potential bonding sites, ...

CalvinTNguyen2D

I’m pretty certain we’ll need calculators, since it’ll be based on some topics we covered on the midterm as well.

CalvinTNguyen2D

The more stable an acid’s structure is, the stronger it usually is because of how it will run to full completion rather than the reaction being partially completed. The more electronegative atoms attached or the more resonance structures, the more stable these acids are.

CalvinTNguyen2D

I think it’d be good to review the general structure and the different things he notes about it; for hemoglobin I remember Prof. Lavelle talked quite a bit about oxygen and iron within hemoglobin.

CalvinTNguyen2D

For transition metals, the oxidation number is an important part of the naming process with a Roman numeral indicating the oxidation state being placed after the transition metal.

CalvinTNguyen2D

Ligands should be named in alphabetical order, but ignore the prefixes when you’re arranging them!

CalvinTNguyen2D

Cisplatin’s ligands are able to bind to the nucleotides of DNA on two sites, while transplatin can only do so on one site.

CalvinTNguyen2D

I already had my test handed back, so you should get it by your discussion date or it’ll be posted online!

CalvinTNguyen2D

Hybridization cam be found relatively straightforward by drawing out the lewis structures for each molecule!

CalvinTNguyen2D

It’ll more than likely be a mix of the two, with an emphasis on calculations and some conceptual understanding as well.

CalvinTNguyen2D

There is a chance for a slight curve, but it’s not large enough for us to bank on it.

CalvinTNguyen2D

Elements that are in the third period and lower are able to draw upon their other subshells and thus can break the octet "rule". There are also other elements that break it by not fully filling their shells to 8 as well!

CalvinTNguyen2D

This equation is only to find the wavelength for objects with mass, velocity, and thus momentum! It will NOT work for electromagnetic radiation, so be sure to not confuse it with c = (frequency)(wavelength).

CalvinTNguyen2D

I've found it really useful to know micro, nano, pico, Angstroms, kilo, milli, and centi off the top of my head, but the exam provides the conversions if you forget as well!

CalvinTNguyen2D

They're somewhat related, but they're not the same!
Ionization energy is the amount of energy required to remove an electron from the atom, while electronegativity is how much an atom attracts electrons towards it!

CalvinTNguyen2D

There's no set formula for VSEPR, but the general format for for the structures is AXnEn (A is the central atom, X is any atom around the central atom, and E is the electron lone pairs surrounding the electron).

CalvinTNguyen2D

The angular momentum is l, n is the principle quantum number, m(l) is the magnetic quantum number, and m(s) is the electron spin number.

CalvinTNguyen2D

De Broglie's equation can be used for any particle or object with a mass and velocity (momentum)!

CalvinTNguyen2D

The longest wavelength correlates with the same amount of energy of the work function. Just set Ep and the Work Function equal to one another and solve for the wavelength!

CalvinTNguyen2D

Electronegativity will increase moving up the periodic table, and also increase going from left to right each period!

CalvinTNguyen2D

Atomic radius will increase as you go down the periodic table, and will also increase as you move from right to left each period!

CalvinTNguyen2D

The magnetic quantum number describes the specific orbital within the shell and the shell shape. It correlates with the orbital quantum number, ranging from -l to +l. This image might be useful to help visualise what's being described by the number. I hope this helps! https://upload.wikimedia.org/wi...

CalvinTNguyen2D

The Aufbau principle is that electrons need to first occupy the lower energy levels before filling higher energy ones- it literally means "build-up" in German! Hund's rule says that the orbitals need to have one electron first before they can be paired up with another electron.

CalvinTNguyen2D

Polarizing power is related to the charge over the size of the ion; Lithium would have the most polarizing power, as it as the smallest radius out of all the cations listed.

CalvinTNguyen2D

Electrons will have a faster velocity than the protons. Because the wavelengths are the same, and electrons are significantly smaller than protons, the electrons' velocity will be faster than the protons'.

CalvinTNguyen2D

s^-1, or one cycle per second!

CalvinTNguyen2D

Just to add on, other elements like sulfur, silicon, and chlorine can have expanded octets!

CalvinTNguyen2D

It'll depend mostly on the equation that you need to use, but generally we use grams for molar conversions and kilograms for calculations involving spectrography.

CalvinTNguyen2D

Your answer should have the same amount of sig figs as the lowest sig fig number given in the problem!

CalvinTNguyen2D

There'd be only 3 sig figs! We don't consider the power in the scientific notion, only the 7.00. Going by that, there would be 3, one before the decimal, and one after.

CalvinTNguyen2D

Yes, the midterm is going to cover everything we've learned up to now. It'd be good to go over all of our homework to review for it!

CalvinTNguyen2D

Molarity refers to the amount of moles of solute over the liters of the solvent. For example, 3 moles of NaCl in a single liter of water would be a 3M solution of NaCl.

CalvinTNguyen2D

To find the molecular formula, you'll need both the molecular mass and the mass of the empirical formula. Simply divide the molecular mass by the empirical mass, and you'll get the ratio you need to multiply the empirical formula by to find the molecular formula!

CalvinTNguyen2D

Accuracy reflects how close your measured values are to the true value, while precision reflects how close together your measurements were! Precision doesn't necessarily have to be close to the true value, just closely grouped together.

CalvinTNguyen2D

If there's no specification, I tend to round to 4 sig figs to keep it relatively precise and accurate; if there are sig figs listed or given in the problem, then just follow those standard conventions!

CalvinTNguyen2D

It's always best to start with the more rare elements first when balancing, then steadily make your way to the more common ones like Oxygen or Hydrogen! It's also very handy to keep a registrar of sorts to keep track of the different element you have!

CalvinTNguyen2D

Round to your sig figs at the very end of calculating; if you do it at the very beginning, your calculations will steadily grow more and more inaccurate because of all the rounding errors that compounded on each other. I like to keep really high amounts of precision with my early calculations so I c...

CalvinTNguyen2D

It definitely can get tedious, but I start with the least common or rarest element within the equation. Once you get these balanced, you usually won't have to go back and rebalance them in the future. Definitely leave Oxygen and Hydrogen for last- they can be really annoying to balance because of ho...

CalvinTNguyen2D

At this level of chemistry, a lot of the nomenclature will be provided to you in the question. I think as we go further in 14B, we'll need to start learning the actual names, formulas, and groups of molecules we see in questions.

CalvinTNguyen2D

On the macro scale, or on the scale where we usually view the world, the water flowing out of the bucket looks like it's flowing as a single continuous substance. However, when you zoom into the actual water, you'll see that the water as a whole is actual comprised of individual water molecules. Lik...

CalvinTNguyen2D

I didn't realise we'd just get 10 points for taking the test, but my TA definitely said they'd give out partial credit whenever possible. It's definitely a good idea to just write down as much work as possible so they can award you for what you have.

CalvinTNguyen2D

My TA said that we shouldn't worry too much about sig figs! They might be graded lightly, if at all, but we should still know the basic rules behind them just in case.

CalvinTNguyen2D

Could anybody help explain the differences between Classical Mechanics and Quantum Mechanics? I was a little bit confused by how the lecture example of water pouring out of a bucket could be modeled by both types of mechanics. Thanks!

CalvinTNguyen2D

Empirical formulas are useful to quickly determine the ratios of atoms in proportion to one another. Larger hydrocarbons, such as heptane (C6H14), can be reduced to a simpler ratio of C3H7. It's also widely used to represent ionic compounds (for example, CaCl2 or NaCl).

CalvinTNguyen2D

I think it should be fine to write in pencil! I've seen some people using one or the other, so it's probably up to personal preference- you should still talk to your TA just to confirm if he or she has any preference.

CalvinTNguyen2D

I do mine in pencil- I tend to make quite a few stray marks or errors in my work, so I like to be able to erase anything so I won't get lost in my train of thought!

CalvinTNguyen2D

It's also good to distinguish specifically between Avogadro's number and Avogadro's constant! Avogadro's number is just the number 6.0221x10^23, and does not include any units. Avogadro's constant is Avogadro's number INCLUDING the units, measuring the amount of atoms, particles, molecules, or formu...

CalvinTNguyen2D

For the problem, the main issue is to find the unknown metal in the metal hydroxide, M(OH)2. We already know the molar mass of the entire metal oxide is 74.10, so in order to find the molar mass of M, we need to subtract the masses of the two Hydroxide groups molar mass M = 74.10 g/mol - 34.02 g/mol...

CalvinTNguyen2D

Thanks! Also in regards to E.21B, the solutions manual rounded the moles of HF to 1.30x10-3 mol, but there were four sig figs in the problem (25.92 mg). Does anyone know why they would round the number to 3 sig figs instead?

CalvinTNguyen2D

I'm using binder paper as well. Does anybody know if we need headers indicating our discussion or lecture at the top?

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