CHEMISTRY COMMUNITY

Elias Omar 1G

Porous disks, or salt bridges, help maintain neutrality in the cell by completing the circuit formed. Electrons flow from anode to cathode, so to keep the cell neutral ions in the salt bridge flow back to the anode.

Elias Omar 1G

Yes they do. A salt bridge is essentially the same thing as a porous disk if that is confusing.

Elias Omar 1G

The reducing agent is being oxidized, or losing an electron, thus causing the reduction, or lowering in charge. The oxidizing agent is being reduced, because it is lowering charge by gaining an electron.

Elias Omar 1G

Since you have to do the lower number of sig figs, the answer would have one digit.

Elias Omar 1G

Yes it is. ICE tables show the concentrations of the reactants and products.

Elias Omar 1G

I still don't understand: Why do liquids and solids (pure substances) not affect the value of K or Q?

Elias Omar 1G

Q is the reaction quotient, meaning it only depends on the concentrations and not the state that the reactants and products are in.

Elias Omar 1G

Gibbs free energy calculates the maximum amount of work that can be done. If G is negative it means work is being done, not work is needed to be done, and in a spontaneous reaction work is done, not needed.

Elias Omar 1G

The porous disk is indicated by the two lines: ||

Elias Omar 1G

For the electrochemical Gibbs free energy equation n represents the number of moles of electrons in the equation.

Elias Omar 1G

Put the inert conductor in the cell diagram with a phase boundary just as if it were another part of the cell.

Elias Omar 1G

All metals are electropositive. All non-metals are electronegative. Salts are ionic compounds that form when electropositive metals and electronegative non-metals bond in a neutralization reaction. In water salts are pulled apart into their negative and positive ions, allowing electctrons to flow ma...

Elias Omar 1G

Test 2 covers everything before the Nernst equation. So yes it will have redox reactions.

Elias Omar 1G

Standard free energy is calculated under standard-state conditions (everything at 1 atm, 20 degrees celcius etc.) These values are experimentally determined. The substances are "pure" in that it should be just them, and that standard free energy is calculated at whatever state they're in a...

Elias Omar 1G

Gibbs Free Energy is what really determines spontaneity: If ∆G is negative then the reaction is spontaneous. If it's positive the reaction is non-spontaneous. Here's how to relate entropy and enthalpy to spontaneity: ∆G positive, ∆ H negative - Spontaneous at all temperatures ∆G positive, ∆H positiv...

Elias Omar 1G

You get more work done in a process that releases heat slowly, since less heat is lost to the surroundings. Reversible processes are infinitely slow, and therefore do the maximum amount of work.

Elias Omar 1G

Yes it can to convert.

Elias Omar 1G

The larger the volume the more ways there are to arrange the molecules, therefore entropy increases as volume increases.

Elias Omar 1G

deltanRT is used when the pressure isn't constant. PnRT is used for constant pressure.

Elias Omar 1G

Specific heats are calculated through experimentation. So we should be given any specific heat we need.

Elias Omar 1G

In class the isothermal examples were all irreversible. Reversible reactions are always do the maximum work because they are done more slowly (infinitely slow) and less heat is lost to the surroundings.

Elias Omar 1G

It should be made very clear whether or not you are looking for heat capacity or specific heat capacity. If units of mass are given at any point in a problem then you are probably looking for specific heat capacity.

Elias Omar 1G

Just like with chemical equilibrium thermal equilibrium is dynamic. This means a that heat is going into the surroundings and the system, and thermal equilibrium is released after the rate at which heat exchange is occuring is equal.

Elias Omar 1G

Bond Enthalpies: Generally you do not want to use this method as it is unreliable. I'm actually not totally sure when you'd use this method. Hess's Law: Remember Hess's Law is about adding enthalpies. You'll use this in problems involving the enthalpies of multiple reactions. Standard Enthalpies: Yo...

Elias Omar 1G

Specific heat capacity looks at the energy change, not at temperature change. If the temperature changes by 1 degrees on either scale, the change in energy is the same per unit of mass (whatever that is). This was confusing to me at first in lecture, but what you need to pay attention to more is the...

Elias Omar 1G

The first kind that was gone over in lecture (two styrofoam cups) was a constant pressure calorimeter. The bomb calorimeter is one in which the volume is kept constant. It's called a bomb calorimeter because they are more prone to explosions as the pressure changes, but not the volume, leading to hi...

Elias Omar 1G

Because of the way bonds work (dipole moments, random movement of shared electrons etc.) there is no single enthalpy for pretty much any non diatomic bond. bond enthalpies are calculated by taking the average of many different bonds of a particular kind.

Elias Omar 1G

K is the constant for the equation at equilibrium . This is what you want the Q, which is the reaction quotient, to be. The reaction quotient determines the direction of the reaction, more product or more reactants. Q is experimentally determined for a particular stage of the reaction, and when it m...

Elias Omar 1G

I think unfortunately a gas being inert has to be experimentally determined. As a general rule noble gases are usually inert if present, but to truly know requires experimentation.

Elias Omar 1G

No it isn't. Adding more reactants will still lead to a stabilization of the reaction in which there is a dynamic equilibrium, with both products and reactants. That's simply the way these reactions are.

Elias Omar 1G

The acidity in DNA comes from the phosphate groups that are found in it. The acidity from this is countered slightly by the bases in the nucleotides, but since those bases are weak bases DNA is overall acidic.

Elias Omar 1G

Yes. Technically there is an electronegativity difference, and due to the shape (pyramidal), and chlorine being more electronegative, there is a dipole towards the chlorine.

Elias Omar 1G

The type of hyrbrid orbital is named after the number of p orbitals that are needed for the central atom to have the right amount of bonds. An sp3 hybrid orbital is 1 s orbital and the three p orbitals of the same energy level (sp2 would be one s orbital and 2 p orbitals). because the central atom b...

Elias Omar 1G

If you mean by how many sites the ligand bonds at then yes you should know that bonding at one, two, three, and six sites are monodentate, bidentate, teidentate and hexodentate respectively. Other terms we saw in the lecture refer to names of specific molecules.

Elias Omar 1G

Calculating exact bond lengths probably relies on information we won't learn in Chem 14A, so you will not need to know exact bond lengths. All you really need to know is which ones are longer (single bonds) and which are shorter (triple bonds) and how valence structures have bond length in between t...

Elias Omar 1G

Lewis acids accept electrons, so a weaker bond means that it is easier for that hydrogen bond to be broken. Iodine is larger than the other atoms and therefore the bond between it and hydrogen is weaker, making it a stronger electron acceptor, or a stronger acid.

Elias Omar 1G

The most important thing to remember is that the electrons are repelling each other and wan to be as far from each other as three dimensions will allow them to be. So whatever number of atoms you have just arrange them so that they are the largest angle apart from each other as possible. As for the ...

Elias Omar 1G

Ionization energy tells how likely an atom is to share an electron, and the atom most likely to share electrons is the one that is going to form the most bonds in a compound.

Elias Omar 1G

If I'm understanding your question right, your asking what's the greatest number of atoms a central atom that's part of an expanded octet, where there are more than 8 valence electrons, can have. Most importantly, expanded octets have enough electrons to keep all atoms at the lowest possible energy ...

Elias Omar 1G

NO3 2- has resonance, meaning that the double bond in it can be between any of the three oxygens and the nitrogen atom. It has been experimentally determined for the N-O bonds in NO3 for example that they are all 124 pm, in between the single bond length of 140 pm and the double bond length of 120 p...

Elias Omar 1G

What this is referring to is how the number of valence electrons an atom has determines how many bonds it can make. Because covalent bonds are the sharing of valence electrons, the number of valence electrons an atom already has determines the number of bonds it can make to achieve an octet. For exa...

Elias Omar 1G

I'm not exactly sure what you're asking, but I think the answer to your question is that sometimes the molecule itself is an ion, and so after adding up the charges of the atom's themselves, you have to subtract or add electrons based on the charge (i.e. if its a 2+ molecule you have to remove 2 ele...

Elias Omar 1G

According to my TA, and I think professor Lavelle as well, all you need to know is that the Balmer series is the series of spectra produced when the electron's final resting place is in the second energy level (n=2), while in the Lyman series the electron's final resting place is the first energy le...

Elias Omar 1G

This is really a much more advanced topic that we don't need to know. But electron spin does ultimately affect the spectra produced. The spin's magnetic moment affects how the atom interacts with magnetic fields.

Elias Omar 1G

In order to find the energy per photon, you just need to know the frequency of the radiation. You only need to use E=h*v. This formula gives you the energy per photon. The answer you should get is around 19.88*10^-19 (E= h(*6.626*10^-34) * v(3.00*10^15). Or E=1.99*10^-18.

Elias Omar 1G

According to my TA and what I remember from Lavelle, we will only need to know what quantum numbers each orbital is represented by. We will not need to draw any and we don't even need to know the orientation (only that a particular quantum number means a particular orientation). Really just focus on...

Elias Omar 1G

Technically we don't. I don't think we're gonna have questions on the scientists and their experiments like in high school. However from experience I can tell you that understanding the experiments can help a lot with understanding concepts.

Elias Omar 1G

In a way yes. the photons that don't have enough energy to remove an electron end up heating up the surface of the metal.

Elias Omar 1G

Atomic spectra shows the frequencies of electromagnetic radiation that a particular atom has the ability to emit as an electron changes energy levels. The photoelectric effect has nothing to do with the types of EM radiation, rather it deals with the energy it takes to remove an electron from the at...

Elias Omar 1G

The reason these elements are diatomic is because they don't have enough electrons to fill up their valence shells. Thus, they cannot exist as a single atom.

Elias Omar 1G

What you need to do is determine what the metal, M, is by using the molar mass given. Then you need to find the molar mass of MS2, the metal and the sulfide bonded.

Elias Omar 1G

While is may be better to limit your significant figures in intermediate steps to the number originally given, I personally try to include as much of the actual numbers as possible. The final answer must have the proper number of significant figures, however it also needs to be as accurate as possib...

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