CHEMISTRY COMMUNITY

Jasmin Tran 1J

I don't believe that it matters since it is in the same state on the correct side of the reaction, but it is more conventional because you would be writing them in the order that it appears in the reaction. Electrode written to the left of the salt bridge in cell notation is always the anode, and th...

Jasmin Tran 1J

The cations (positive ions) flow toward the cathode to replace the cations that are being picked up at the electrode. The anions (negative ions) flow toward the anode to balance the positive charge of the cations that are released from the electrode. So, both flow so that the net charge is maintaine...

Jasmin Tran 1J

Part a doesn't have platinum on the oxidation side because liquid mercury (Hg) can also be used as an electrode.

Jasmin Tran 1J

For more explanation, you should go to https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Kinetics/Experimental_Methods/Methods_of_Determining_Reaction_Order and scroll down to Example 4, where the site goes through the strategies and solutions to finding reaction order and rate con...

Jasmin Tran 1J

So, the reaction mechanism describes the sequence of elementary reactions that must occur to go from reactants to products. Reaction intermediates are formed in one step and then consumed in a later step of the reaction mechanism (can be used in faster steps that are not shown), which kinetic inform...

Jasmin Tran 1J

A reaction rate can have a negative partial order with respect to a substance. For example, the conversion of ozone (O3) to oxygen follows the rate equation (rate = k[O3]^2/[O2]) in an excess of oxygen. This corresponds to second order in ozone and order (-1) with respect to oxygen. When a partial o...

Jasmin Tran 1J

You can also see a Rate Law Summary in Table 15.2 in the book, and it shows a comparison of all three rate laws to see how they are related.

Jasmin Tran 1J

This is an intermediate reaction of another reaction, but it is still second order:
O + H2O → 2 OH
A common product of combustion is water, and reacts with all the loose oxygen atoms produced in other reactions to form hydroxides.

Jasmin Tran 1J

Differential rate laws express the rate of reaction as a function of a change in the concentration of one or more reactants over a particular period of time while integrated rate laws express the reaction rate as a function of the initial concentration and an actual concentration of one or more reac...

Jasmin Tran 1J

A galvanic cell IS an electrochemical cell in which a spontaneous chemical reaction is used to generate an electric current. The formal definition of an electrochemical cell is a device in which an electric current is either produced by a spontaneous chemical reaction or used to bring about a nonspo...

Jasmin Tran 1J

I believe that you want to compare them when they are all in the same oxidation state, and for this part, they are all in the 2+ state.

Jasmin Tran 1J

Yeah, same as the two above - I believe it came from the solution since OH- is needed for the reaction

Jasmin Tran 1J

For further explanation: E(cell) = electrical potential of the cell E(cell) = electrical potential of the cell under standard conditions R = universal gas constant T = temperature in kelvin n = the number of electrons transferred in the reaction (from balanced equation) F = Faraday’s constant (96,50...

Jasmin Tran 1J

H+ is also used to calculate the pH of the system, which can also be asked for in a problem. So H+ (can also be H3O+, the hydronium ion), is used instead of H2 because H2 is a neutral molecule.

Jasmin Tran 1J

Yes exactly what Julian said above! Most of the time you’ll just assume acidic conditions, but it is usually explicitly stated. Just make sure that you use H2O to balance both conditions when adding OH- or H+ and you’ll be fine!

Jasmin Tran 1J

So the Nernst Equation is derived from the Gibbs free energy equation under standard conditions. E°(total) = E°(reduction)−E°(oxidation) can be related to ΔG° = -nFE, where n = the number of electrons transferred in the reaction (from balanced chemical equation), F = the Faraday constant (96,500 C/m...

Jasmin Tran 1J

So in a salt bridge, cations flow toward the cathode to replace the cations that are being picked up at the electrode; anions flow toward the anode to balance the positive charge of the cations that are released from the electrode.

Jasmin Tran 1J

I think we should know how to use it if it comes up just to be safe, but I don't believe that we will have to memorize it. I checked the outline on his website as well, and the equation (3/2)RT is not on there either.

Jasmin Tran 1J

We assume that it is 1 mol of gas because that is a characteristic of ideal behavior.

Jasmin Tran 1J

According to the original definition, Gibbs defines “available energy” as “the greatest amount of mechanical work which can be obtained from a given quantity of a certain substance in a given initial state, without increasing its total volume or allowing heat to pass to or from external bodies, exce...

Jasmin Tran 1J

All exergonic reactions occur spontaneously, meaning that no outside energy is required for them to start. Another common example of an exergonic reaction is mixing sodium and chlorine to make table salt.

Jasmin Tran 1J

An endergonic reaction (aka a nonspontaneous reaction) is one in which the standard change in free energy is positive and energy (in the form of work, heat, etc) is absorbed.

Jasmin Tran 1J

I think that this question has 6 s/f in the answer because it is using exact values from the appendix. In this case, s/f doesn’t really matter because they are giving you the values - you don’t have to calculate them yourself.

Jasmin Tran 1J

Water is usually shown in its liquid state because the combustion reactions produce steam, which then condenses to become liquid water/release heat.

Jasmin Tran 1J

The process of rusting is a slow oxidation of Fe by oxygen, producing iron oxide by forming new bonds. The formation of bonds releases heat, making it an exothermic reaction.

Jasmin Tran 1J

You can use the equation multiple ways for a calorimeter problem, but the most used way by calculating heat, Q. You use the equation Q = m * c * delta(T), where m is the mass of water, c represents the heat capacity of water, or 4.184 joules per gram per degree Celsius, J/gC, and delta(T) represents...

Jasmin Tran 1J

Yes! The TA's or Lavelle will usually specify which chapters they want hw problems from, but since we have only done Chapter 8 so far, that is the chapter that they expect problems from.

Jasmin Tran 1J

Just remember to convert to the correct units whenever it is asked for in a problem and you'll be fine!

Jasmin Tran 1J

For more clarification, Hess's Law essentially states that the energy of a chemical reaction is the same regardless of the number of steps needed/reaction mechanism.

Jasmin Tran 1J

Just to add on, heat AND work are both path functions.

Jasmin Tran 1J

I believe so! Last quarter my TA for this class accepted it in both pen and pencil, but it would probably be best to ask and make sure

Jasmin Tran 1J

NH4(NH2CO2) is a solid, so it is not included in the equilibrium calculation. Solids and pure liquids do not go into the K expression.

Jasmin Tran 1J

Monodentate means that it is bonded at one spot, bidentate meaning two spots, and polydentate meaning many (unspecified). We make this distinction so that we know how many spots a ligand can bind at. An example of polydentate is the hexadentate EDTA.

Jasmin Tran 1J

Delocalization occurs when the e- can move around, which will result in resonance structures. This is only seen when a pi-bond (or bonds) is (are) present. A pi bond is present when two sets of electron orbitals involved in the bond overlap, and is always accompanied by one sigma bond (sigma bond fo...

Jasmin Tran 1J

The reason why you cannot use the number of mols for NH4(NH2CO2) to find the number of mols for NH3 is because, in this case, NH4(NH2CO2) is a reactant and NH3 and CO2 are the products. For this problem (and others), you would have to use one product to find another in order to yield the correct ans...

Jasmin Tran 1J

It's false because the value of the eq constant isn't affected by the amounts of reactants or products as long as the temp stays constant

Jasmin Tran 1J

Roman numerals represent the oxidation state of the metal because some metals have more than one oxidation state. Ex. Iron (II) which is 2+ and Iron (III) which is 3+.

Jasmin Tran 1J

Also, be sure to know how to convert between the two types of units; a conversion constant is usually given as well.

Jasmin Tran 1J

I was on another site and it said that anionic ligand names as prefixes were changed from -ide to -ate, -ite to -ido, -ato, and ito.. Neutral and cationic ligands are usually unchanged, with a few exceptions.

Jasmin Tran 1J

Pi bonds are basically 2 orbitals that overlap side by side. They also do not allow bound atoms to rotate and have e- density on each side of the internuclear axis.

Jasmin Tran 1J

Also, an example of a polar molecule would be water, H2O. The O is slightly more negative than the H, giving it a bent shape. An example of a nonpolar molecule would be carbon dioxide, CO2. It is a straight molecule with the C forming double bonds in the middle, so the charges are equally distributed.

Jasmin Tran 1J

Also in the midterm review today, the UAs basically said that an atom of P, S, Cl or another nonmetal in Period 3 and subsequent periods can have more than 8 electrons in it's valence shell because they have more orbitals available to them (ex. the d subshell). Hope this clarifies a bit more!

Jasmin Tran 1J

For further explanation for the whole question, (a, Carbon) shows 2 electrons in one p orbital when there are empty p orbitals, so it is in an excited state because ground state electrons want to be in separate orbitals. For (b, Nitrogen), one electron has opposite spin compared to the other two, bu...

Jasmin Tran 1J

In response to your questions about d and f, I don't think we would have to know the exact ones since there are so many and since they are also harder to draw than the p orbital

Jasmin Tran 1J

This is also because silver is one of the special exceptions to the configuration rule where one electron from the s subshell will go to the d subshell in order to have a full d shell

Jasmin Tran 1J

The H term also stands for Hamiltonian, which is the total energy of the system (kinetic plus potential energy). Hope this helps to clarify a bit more!

Jasmin Tran 1J

In other words, the two exceptions are for a half-filled d5 and full d10 subshells because they have lower energy. Like Angelica said, this is to make the atom more stable. These exceptions pull one electron from the s subshell (which is the subshell that holds valence electrons in this case) and pu...

Jasmin Tran 1J

Also, make sure the variable is h and not "h bar" (the h with a cross on the top), because h bar refers to the uncertainty principle and has a different value than h, which is Planck's constant.

Jasmin Tran 1J

What I've been doing to prepare for tests is by watching and going through his online modules after lectures for further understanding and to to test myself on the problems that he gives. I found that doing so helped a lot for the first test, so I imagine that it would be similar to this one. Hope t...

Jasmin Tran 1J

Yes exactly what the two above said, and it's easier to remember since c=2.99*10^8, so the the product of the frequency and wavelength of a beam will always be c or close to c, with the appropriate sig figs.

Jasmin Tran 1J

For further clarification, the d orbital starts with 3d and goes to 3d^10. The d orbital specifically starts with the transition metals because those orbitals are what give them their properties. The order for electron configurations would go 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^10, 4p^6, and so on.

Jasmin Tran 1J

Like the posters above, I normally convert after or as I'm doing the problem. Say I'm starting with 5.5 kg of Al, I would convert to g or whatever units the question is asking for first so that I don't get confused at the end. Plus, it makes the work neater if you have it with dimensional analysis.

Jasmin Tran 1J

Aluminum only has one ion, so it would be Al3+, so if it were paired with oxygen it would be Al2O3, so the charge of 2Al would be 6+ and the charge of 3O would be 6- (since the charge of O is 2-) in order to be balanced.

Jasmin Tran 1J

Exactly what the post above said, but this is for further explanation. The O2 in SnO2 implies that there are two oxygen atoms, each with a -2 charge, so together they form a -4 charge. Tin (IV) has a 4+ charge, making it the right name for the oxide.

Hope this made it clearer!

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