CHEMISTRY COMMUNITY

Astrid Lunde 1I

It is a first order rate law so use lnA = -kt + lnA

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K has no units because it is a ration.

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You can also look at K's units to find which order it is. M/S is 0th order. 1/S is 1st order. 1/SM is 2nd order.

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Anything with a o means that it is standard. So $\Delta G$ o is standard and $\Delta G$ is regular.

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∆G° = ∆H° - T∆S°and ∆G° = - RT ln K and G=-nFE are essential, but are also on your equation sheet.

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It should specify if it is Basic or Acidic. Acidic meaning balance with H+ and Basic meaning balance with OH-.

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Look at the oxidation numbers of the different elements.

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Add H2O fist to balance the oxygen and then the H+ to balance the hydrogen.

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The anode is on the left and the cathode is on the right. Make sure you put lines in between the solid, gas and aq.

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I would use Pt(s) as it is more common.

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The comas are used in a cell diagram to separate two of the same states in a half reaction.

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Find the change in oxidation number for an atom. If the oxidation number decreases from reactants to products then it is reduction. If the oxidation number increases from reactants to products then it is oxidized.

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anode is the left and cathode is the right. Also remember aq us closest to the center of the cell diagram than gas and lastly solid.

Astrid Lunde 1I

k is the constant rate so it has no units.

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Cathode is were reduction occurs and anode is were oxidation occurs.

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It helps you separate what is being reduced and what is being oxidized in the reaction. After balancing the reduction and oxidation separately we can then add them together to make the overall balanced redox reaction. This would be a lot more difficult to do if we did not separate them first.

Astrid Lunde 1I

CNourian2H wrote:how do the terms anode and cathode relate to oxidation and reduction. He used the latter pair of terms to define anode and cathode, but can someone explain this further?

Cathode is the reduction reaction and the anode is the oxidation reaction.

Astrid Lunde 1I

It is usually written in that order, but I would always double check to see where the oxidation and reduction reactions are placed in correspondence to the left and the right of the galvanic cell.

Astrid Lunde 1I

Does anyone know what Lavelle's office hours are like? Is it going over general HW problems and information, or do we need to ask him questions and bring our own HW problems in? It's similar to the TA office hours where you are able to ask questions. When I went it was mostly questions regarding th...

Astrid Lunde 1I

To write the half reactions you need find out what is being oxidized and reduced which you do by finding the oxidation number for each species present.

Astrid Lunde 1I

U is equal to 0 because it is an isolated system so there is no energy energy leaving or going into the system.

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Question 8 was problem 4I.9 on our homework problems, that is what my TA said.

Astrid Lunde 1I

In that case I would use P1V1=P2V2. PV=nRT is usually used when you have three values and the constant and only need to solve for the last value.

Astrid Lunde 1I

Cv is constant volume and Cp is constant pressure.

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delta S is the total between delta S of the surroundings and the system.

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w is when work is being done one the system. -w is when the system is doing work.

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There are many review sessions for the midterm. The one on Sunday should cover everything with practice problems.

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Closed system can exchange heat while an isolated system has no effect from the surroundings.

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Isolated systems do not interact with the environment around it. A closed system can transfer energy.

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It is so tightly sealed that the volume can not change and there is no effect from the outside system.

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Because they are state functions the enthalpies should be added.

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There are really no other differences other then what you said qv occurs under constant volume and qp under constant pressure.

Astrid Lunde 1I

Kp is when you deal with partial pressure so it is used for gasses. Use Kc when you see aq.

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Catalyst speeds up the reaction.

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The gas constant is given on the formula sheet, make sure you chose the one with the units that apply to the equation.

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Acids donate protons and bases accept protons.

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They both work, check what units are given in the problem and use the same units.

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If the K value is less than 10^-3 then you can approximate and there is not need for the quadratic formula.

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Yes, scientific calculators are permitted, however graphing calculators are not.

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It is on chemical equilibrium as well as acids and bases

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The N2 bonds are broken which requires heat making it an endothermic reaction.

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We can approximate if x is less then 1.0 x 10^-4.

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Yes, you multiply the mole fraction with the total pressure to get the partial pressure.

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K represents the ratio of products to reactants so P/R.

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They are two different units, but they do the same thing:measure pressure. As long as you are constant with what unit you use for a single problem you should be ok.

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Yes the solids and liquids have no effect on the calculation.

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The units in the question should help you find out when to use Kc and Kp. Kc is in M and Kp is in Bar.

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Yes it will still be the same, but Kc is in terms of Moles and Kp is in terms of Bars.

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Yes you can solve Q the same way as you would solve K.

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When K is a large value > 10^3 then there are more products at equilibrium. When K is a small value <10^-3 then there are more reactants.

Astrid Lunde 1I

Acid rain is when CO2 reacts in the atmosphere which results in acid rain. This rain, like stated in the name, is Acidic. When there is an excessive amount of CO2 in the air there will be a lot of acid rain. This contributes to the greenhouse effect and global warming.

Astrid Lunde 1I

Ligands are ions or molecules that are attached to the central atom, they are lewis acids.

Astrid Lunde 1I

Hydrogen bonding occurs when the hydrogen bonds with N,O or F

Astrid Lunde 1I

One thing to know that Dr. Lavelle mentioned in class is that if a pKa value is given it is highly likely that that acid is a weak acid. Strong acids strongly favor the products and, thus, have an astronomically large pKa. Does that mean strong acids have a high conc of H+? Yes, the pKa is so large...

Astrid Lunde 1I

know how to draw the lewis structure. Hemoglobin transports oxygen thought the bloodstream because the oxygens are weakly attached, bonds to 4 oxygens. Myoglobin stores oxygen in muscles because the single oxygen is strongly attached.

Astrid Lunde 1I

For Lavell's class I think we should stick to using VSEPR theory to determine the shape of a molecule as he taught in lecture.

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You should name the bonds individually and draw the sigma next to the first bond and the pi next to the second and/or third bond, depending on the number of bonds.

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The roman numeral tells us the charge on the metal ion.

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It can only from one bond because it only has one electron, which is in the 1s orbital so it can only be hybridized in the 1s orbital.

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Check the net dipoles of the molecule. If you see lone pairs the molecule will always be polar.

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No, it is the same compound.

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Look at the lewis structure and the bonds formed between the atoms. single bond is 1 sigma bond, double bond is 1 sigma and 1 pi bond, triple bond is 1 sigma and 2 pi bonds. So the fist bond is always sigma and anything after is a pi bond.

Astrid Lunde 1I

A ligan is a ion or a molecule bonding to a metal atom.

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The naming of the molecule should be in alphabetical order.

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Yes, it would be less because the lone pairs push on the other bonds.

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The electron geometry is octahedral and the molecular geometry is square planar.

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You add the number of lone pars of the atom to the number of atoms the atom is bonded to.

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805097738 wrote:can someone explain what bond order is?

Bond order is measure of the number of electrons involved in bonds between atoms in the molecule. The higher the bond order means the stronger the chemical bond.

Astrid Lunde 1I

It is octahedral because there are 6 bonding pars and 2 lone pairs. Square planar is when there are 4 bonding pairs and two lone pairs.

Astrid Lunde 1I

The are asking for the ClO2 cation so there are 18 electrons. The shape is trigonal planar and the bond angle is 120 degrees.

Astrid Lunde 1I

TeCl4 is See-saw shaped so the bond angles have to be 120 and 90.

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No, not every atom has to have a formal charge of 0 but they all have to add up to 0 to make the formal charge of the molecule 0.

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The bond lengths are all the same because the actual structure is a mix of all the resonance structures.

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Yes, the optimal structure would be the middle atom having a 0 charge.

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APatel_4A wrote:How do we know what the central atom should be?

It is the least electronegative atom

Astrid Lunde 1I

They have to add up to the same formal charge.

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505106414 wrote:Is it okay to break the octet rule in order to minimize formal charge?

No unless the atom itself is able to break the octet rule.

Astrid Lunde 1I

It means the electron is exited

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The elements in group 3 can break the octet rule.

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To find the valence electron from the periodic table look at the group number.

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They are found in ionic bonds as-well.

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Some atoms are more stable with expanded valence shells like phosphorus when it bonds with Chlorine.

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It means each atom has to have an octet.

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An ionic bond is the transfer of electrons from a metal to a non metal atom.
A covalent bond is the sharing of electrons of non metals.

Astrid Lunde 1I

There are a few exceptions, but generally yes they need to follow the octet rule.

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They should all be given, however I assume we would have to know simple molecules like water.

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To find the number of valence electrons look at the group number, however this does not work for d block elements.

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Electronegativity decreases down a group and increases across a period.

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In his lecture today, Lavelle emphasized that the plane the electron is found in is arbitrary and different textbooks associate different l values with different x,y, and z planes. So, because he said this we can assign the x,y,z variables to the values we have correct? That confused me as well. I ...

Astrid Lunde 1I

As you go down the group the number of electrons increases for each atom. You then get more shells and the valence electrons in the outermost shell get farther away from the nucleus.

Astrid Lunde 1I

No, I think as long as you list them you should be fine.

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I think this is related to the model that was shown during the lecture today. Depending on the $m_l{}$ number we can use the table to find out if it is x, y, or z.

Astrid Lunde 1I

Is it only possible for an electron to have a +1/2 or -1/2 spin?

Astrid Lunde 1I

Location on the electromagnetic spectrum doesn't exactly determine which series a line belongs to. Each line represents energy released by the movement of a hydrogen electron from one energy level to a lower energy level. Each energy level is represented by what's called the principal quantum numbe...

Astrid Lunde 1I

Im pretty sure you would use the equation $\bigtriangleup E = E_f{} - E_I{}$
Correct me if I'm wrong.

Astrid Lunde 1I

I think professor mentioned in class that the perfect black body that can absorb all frequencies of light does not currently exist. Cuz if we can still see it, it must has reflected some sort of frequencies which are able to be detected by our eyes, or it will just be invisible. Plz correct me if I...

Astrid Lunde 1I

A photon is just the name for a quantum of light, right?

Astrid Lunde 1I

Joseph Saba wrote:I believe since we use the equation c = w*f, then 3e8= 98.6e6x. to solve for x (wavelength) then divide by the frequency. I got 3.05 meters.

Are c and w*f constant values in the equation you used?

Astrid Lunde 1I

Percent yield means the actual yield divided by the theoretical yield. You want the percent yield to be as close to 100% as possible to get the maximum amount of yield form the product you created.

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You can use the term Metabolism which is a general term for biological processes.
Or you can use the term Oxidation which means the compound reacts with oxygen.

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