CHEMISTRY COMMUNITY

Anna Chen 1K

I agree the only difference is that Ecell does not require standard conditions like Excel.

Anna Chen 1K

We should be given results back by the end of this week. It should come pretty soon since it was taken online.

Anna Chen 1K

I agree, you will get a C- if you get at least 250 points.

Anna Chen 1K

Yes, I agree that it will be soon since the final was taken online.

Anna Chen 1K

I think each person will get the grade they deserve.

Anna Chen 1K

If cell potential is not given, the oxidation half-reaction should be on the left/anode, while the reduction half-reaction should be on the right/cathode. You should look at how electrons are transferred to verify though.

Anna Chen 1K

You add platnium, or another solid metal conductor, whenever there is no solid on either side of the cell diagram.

Anna Chen 1K

Yes, it should be evenly distributed. However, there is a possibility specific topics will be emphasized like in the midterm.

Anna Chen 1K

Yes, test 1 will probably be handed back in discussion.

Anna Chen 1K

I believe leaving all 100 posts is fine, too.

Anna Chen 1K

The degree symbol indicates the reaction is at standard conditions (298 K, 1 atm)

Anna Chen 1K

Generally, yes, the cathode is usually on the right and the anode is usually on the left. However, if you want to make sure, the cathode is always the reduction while the anode is always the oxidation. You determine which solution is reduced and oxidized by looking at the transfer of electrons in th...

Anna Chen 1K

A salt bridge prevents ion buildup and helps the electrons transfer from the anode to cathode.

Anna Chen 1K

K is used when the situation concerns the reaction at equilibrium; Q is used when the situation concerns the reaction at any point besides equilibrium

Anna Chen 1K

the second page of thermochemistry and all of electrochemistry

Anna Chen 1K

There are two half reactions in a redox reaction. Oxidation is the half reaction involving a loss of electrons; reduction is the half reaction involving a gain of electrons.

Anna Chen 1K

positive standard reduction potential --> spontaneous reduction

Anna Chen 1K · Re: chemistry community posts The weekly posts are due Sunday 11:59 PM.

The weekly posts are due Sunday 11:59 PM.

Anna Chen 1K

If it is an acidic solution, you add H+; if it is a basic solution, you add OH-.

Anna Chen 1K

Half reactions are the two reactions involved in a redox reaction, oxidation and reduction. Oxidation is the reaction involving a loss of electrons; reduction is the reaction involving a gain of electrons.

Anna Chen 1K

Delta S - regular delta S, usually concerns the system of the reaction
Delta S (surroundings) - usually equals negative delta S (system)
Delta S (total) - equals delta (system) + delta (surroundings)

Anna Chen 1K

Half reactions just show the transfer of electrons in oxidation and reduction. Two half reactions, or an oxidation coupled with a reduction, equals the full reaction.

Anna Chen 1K

Electrochemistry is the study of electricity and how it relates to chemical reactions. In electrochemistry, electricity can be generated by movements of electrons from one element to another in redox reactions.

Anna Chen 1K

You can use the equation ΔS° = ΣS°(products) - ΣS°(reactants) to solve for entropy of a reaction since entropy is a state function.

Anna Chen 1K

An isochroric process is one where volume stays the same.

Anna Chen 1K

A redox reaction is a reaction where both reduction and oxidation occur, also known as two half reactions. Oxidation involves the loss of electrons, whereas reduction involves gaining electrons.

Anna Chen 1K

S(gas) >> S(liquids) > S(solids)

Anna Chen 1K

q is heat while rev refers to a reversible reaction so q rev is used for calculating heat for a reversible reaction.

Anna Chen 1K

Based on past Lavelle midterms and finals, it will most likely be around 8 free response questions with each question having multiple parts to it.

Anna Chen 1K

The midterm will cover up to outline 4: Focus 4F-J. This means 5G.3, 5G.4, and 5J.3, are not on the exam.

Anna Chen 1K

The midterm will cover up to Focus 4F-J.

Anna Chen 1K

Spontaneous, or favorable, reactions favor the formation of products over reactants and have a negative value in delta G. A reaction's overall entropy, or disorder, also increases.

Anna Chen 1K

It is negligible for solids and liquids because they maintain a constant volume.

Anna Chen 1K

Force is (pressure x area). You can derive this from the equation, P = F/A.

Anna Chen 1K

This is referring to q.

Anna Chen 1K

I also received mine back during Week 4's discussion section.

Anna Chen 1K

Partial pressure is the pressure of one gas but pressure is the pressure of the whole system. All the partial pressures added together equals pressure.

Anna Chen 1K

The value for the gas constant depends on the units used in the specific question.

Anna Chen 1K

You should only use it for calculating the moles of gases.

Anna Chen 1K

The R constant is the gas constant. Its value is determined by the units in the specific problem.

Anna Chen 1K

Yes, it is Week 6.

Anna Chen 1K

Yes H2O is not included in the ICE tables along with solids and liquids.

Anna Chen 1K

Solids and liquids equal 1 so they are neglected when calculating K.

Anna Chen 1K

Use PV=nRT to convert moles to pressure. Moles is represented by n and pressure is represented by P.

Anna Chen 1K

K is used when a reaction is at equilibrium while Q is used when a reaction is at any point.

Anna Chen 1K

I agree that PV=nRT proves that pressure and volume have an inverse relationship.

Anna Chen 1K

If a reaction shifts to the right, then the forward reaction is favored and more products will be produced.
If a reaction shifts to the left, then the reverse reaction is favored and more reactants will be produced.

Anna Chen 1K

It will definitely consist of Outline 1 and possibly outline 2 considering tests will begin week 3.

Anna Chen 1K

Kc is defined by molar concentrations while Kp is defined by the partial pressures of the gasses.

Anna Chen 1K

Q determines which direction a reaction will proceed at any time during the reaction. If Q < K at some time during the reaction, then there are more reactants than products and the forward reaction is favored. If Q > K at some time during the reaction, then there are more products than reactants and...

Anna Chen 1K

K is the equilibrium constant.
Kc is defined by molar concentrations while Kp is defined by the partial pressures of the gasses.

Anna Chen 1K

Yes, all molecules have LDF. Dipole-induced dipole occurs between an ion and non-polar molecule.

Anna Chen 1K

De Brogile's equation says that any moving particle with momentum, p, has wavelike properties with wavelength, λ. (λ=h/p --> λ=h/mv)

Anna Chen 1K

The ending of a metal's name always changes to -ate when it the compound is anionic, or has a negative charge.

Anna Chen 1K

Yes, hydrogen bonds are stronger than dipole-dipole bonds.

Anna Chen 1K

A hydrogen bond is any bond between H and F, O, or N. You can count the hydrogen bonding sites for these.

Anna Chen 1K

Hydrogen bondings occurs when H bonds to either F, O, or N.

Anna Chen 1K

I also got the same equations!

Anna Chen 1K

I suggest attending the review sessions and doing the practice problems.

Anna Chen 1K

I agree that both are correct the preferred way is to write it beginning with d.

Anna Chen 1K

Yes, I believe we will be given the formula first.

Anna Chen 1K

You should plan to study consistently from this point until the day of the final. You should attend the upcoming review sessions and workshops, review notes, and do the practice problems.

Anna Chen 1K

There is a different shape when referring to each central atom.

Anna Chen 1K

I agree that the strength of an acid is usually determined by its pH or H+.

Anna Chen 1K

We should visualize sigma bonds as the head-to-head overlap of two sp2 orbitals and pi bonds as the side-to-side overlap of two 2p orbitals.

Anna Chen 1K

Hybridization happens when an atom bonds using electrons from both the s and p orbitals, creating an imbalance in the energy levels of the electrons. To equalize these energy levels, the s and p orbitals involved between the two atoms are combined to create hybrid orbitals.

Anna Chen 1K

Either definition should be fine.

Anna Chen 1K

Yes, I agree that the symmetry of a lewis structure can sometimes help in determining polarity, but the most accurate way would be to evaluate electronegativity differences.

Anna Chen 1K

N, O, or F can form a hydrogen bond with H.

Anna Chen 1K

Bond length is determined by the bond order, or the number of bonded electrons. This has to be derived from experiments.

Anna Chen 1K

(a) Of the three forms, 1 and 2 are polar. (b) The largest dipole moment occurs in 1.

Anna Chen 1K

(a) Of the three forms, 1 and 2 are polar. (b) The largest dipole moment occurs in 1.

Anna Chen 1K

(a) sp^3 (b) sp^3d^2 (c) sp^3d (d) sp^3

Anna Chen 1K

When a liquid has high viscosity, it means there is a lot of friction between the adjacent layers of a liquid. This will make the liquid flow slowly.

Anna Chen 1K

Not really, you should pay attention to the kind of bonds in a compounds in a lewis structure. If there are more than one kind, it should have resonance structures.

Anna Chen 1K

An oxidation number is the charge that atom would have if it was made up of ions.

Anna Chen 1K

F, O, N can form a hydrogen bond with H.

Anna Chen 1K

Sigma bonds are formed by end-to-end overlapping of atomic orbitals; pi bonds are formed when the lobe of one atomic orbital overlaps another.

Anna Chen 1K

When n = 12, l = 0-11 (12 values).

Anna Chen 1K

Yes, you can use the double arrows to draw a lewis structure's resonance structures.

Anna Chen 1K

Electronegativity is the tendency of an atom to attract a bonding pair of electrons.

Anna Chen 1K

You should only round to a whole number when the decimal is extremely close to a whole number. For example, 1.96 to 1.99 can be rounded to 2. However, 1.6 or 1.8 should be multiplied to a whole number.

Anna Chen 1K

The 4s orbitals have a lower energy than the 3d orbitals, so the 4s orbitals are filled first. However, Lavelle has said to write 3d first.

Anna Chen 1K

First, add the negative charge to the total number of electrons in order to know how many electrons to represent in the Lewis structure. Second, you can draw brackets around the Lewis structure and write the negative charge besides the top right corner.

Anna Chen 1K

No it technically does both because diagonally down is basically straight down and to the left.

Anna Chen 1K

The resonance structure with the lowest formal change is the most stable.

Anna Chen 1K

You should be familiar with atomic radius, ionization energy, electron affinity, and electronegativity.

Anna Chen 1K

You should understand the trends of ionization energy. It increases going across a period and up a group.

Anna Chen 1K

The same equation sheet used for test 1 will be used for future tests/midterms/finals.

Anna Chen 1K

This is a set mass which will also be given as a constant on the test.

Anna Chen 1K

The order of filling orbitals is: 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^10, 4p^6, and so on.

Anna Chen 1K

The standard unit for wavelength is meters (m) but it can be converted from nanometers, centimeters, etc.

Anna Chen 1K

The answer is c) The extent of the change in the electrical field at a given point decreases. The electrical field corresponds to the amplitude; as the frequency decreases the waves broaden and the extent of the change decreases.

Anna Chen 1K

Yes, the speed of light is always going to be 2.998 x 10^8 m/s. It is always going to be a constant too. Sometimes, it is rounded to 3.00 x 10^8 m/s; however, using 2.998 x 10^8 m/s is recommended for accuracy.

Anna Chen 1K

Yes, Lavelle said week 3 homework can be on the quantum unit.

Anna Chen 1K

You should follow the standard sig fig rules for multiplication/division and addition/subtraction. For addition/subtraction, the number of sig figs should match the smallest amount of decimals in a given value. For multiplication/division, the number of sig figs should match the smallest amount of s...

Anna Chen 1K

Yes, we will consider the speed of light as a constant that can be expressed as 3.00 x 10^8 m/s^-1.

Anna Chen 1K

I also support the above post that our 5 posts are due at Sunday 11:19 PM.

Anna Chen 1K

To find the amount of excess reactant remaining, subtract the mass of excess reagent consumed from the mass of excess reagent given.

Anna Chen 1K

You should convert to moles and liters, as those are the standard units.

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