CHEMISTRY COMMUNITY

Martina

Rate constant is affected by temperature and activation energy in the equation. Catalysts lower the activation energy and speed up the reaction.

Martina

Intermediates will first be formed as a product and then used up as a reactant while catalyst will first be used as a reactant and then show up a product.

Martina

You can also look at units of the rate constant if it is given and be able to tell what the order is.

Martina

Yes you can use either equation with the log or the ln because the conversion between them is part of the equation, so you should get the same answer.

Martina

It is the slowest step of the reaction, since the other steps are much faster, it determines the rate of the overall reaction.

Martina

In a concentration cells both the anode and cathode side contain the same species, but with different concentrations. Also the E naught of the cell is zero.

Martina

If you already flip the value for the oxidation part of the reaction, then you just have to add them, or you can subtract the cathode from the anode for both reduction values. Either way it is the same, but it can get confusing.

Martina

Delta G gives the best case scenario, so it shows the maximum amount of work that could be done. I do not think there are any exceptions.

Martina

You only add a solid (usually Pt) to whichever side, if any, does not already have one. If the reaction for each side already contains a solid, do not add one.

Martina

The rate is high as the reaction begins because there are more reactants, as the concentration of reactants decreases, the rate decreases.

Martina

You have to balance the reduction and oxidation half reactions and then see how many electrons are added in order to balance the charges. The number of electrons is the n value.

Martina

You have to balance the oxidation and reduction half reactions, and see how many electrons you have to add in order to balance it. That number is n.

Martina

You add H20 to balance the oxygens in both types of reaction. Use H+ to balance the hydrogens in an acidic solution and OH- to balance hydrogens in a basic solution.

Martina

I think that is correct, and you use commas to separate different species that have the same phase.

Martina

H2O is a solvent so it is not important to include in the cell diagram because it is assumed that you have an abundance of it.

Martina

Yes, because for something to be a reducing agent it has to give away an electron to another species, which ends up reducing it, and vice for oxidizing agents.

Martina

This delta G is based off of knowing the delta H and delta S.

Martina

It is usually given in the problem or the equation unless it is something obvious like oxygen gas.

Martina

Platinum can be used to transfer electrons if there is no other conducting solid.

Martina

Potential difference is the energy in volts needed to change an electrical charge.

Martina

Test 2 includes the end of outline 4 and all of outline 5 (Electrochemistry) which I think will be covered during week 8.

Martina

You would have to balance the charges of all the molecules in the equation and see which ones lose electrons making the oxidized and which ones gain electrons making them reduced.

Martina

You have to check the known charges of the ions and make sure that they balance out for the entire equation.

Martina

Ions have a different number of electrons and protons, so they will have a charge depending on that difference.

Martina

This equation can be used to calculate the equilibrium constant when the temperature and delta G are known. This helps to compare K at different temperatures.

Martina

This equation lets you solve for K at different temperatures, so it can show you the change in the equilibrium constant between T1 and T2.

Martina

This equation lets you solve for K if you have delta G and the temperature. It can also be used to calculate K at a different temperature if delta H is known by setting delta G equal to delta H minus T delta S.

Martina

If delta G is zero then that means the reaction is at equilibrium. So Q must be equal to the equilibrium constant K.

Martina

It makes it easier to understand which atoms are losing electrons and which are gaining electrons in the reaction.

Martina

Sudden expansion represents irreversible reactions while a gradual expansion represents a reversible expansion because of the small gradual expansion that allows for the most work to happen.

Martina

Monoatomic particles have a heat capacity of 3/2 R. For liner molecules it is 5/2 R because there are more possible positions for the molecule.

Martina

The change in temperature would be when there is no heat or pressure.

Martina

You can use either, both are correct it just depends on what is given.

Martina

Cv is 3/2 R and is used under constant volume and Cp is 5/2 R and is used under constant pressure.

Martina

It only matters if it is a bomb calorimeters instead of a regular calorimeter.

Martina

You have to make sure all of the products and reactants cancel out by flipping some of the equations and changing the sign. Then you can add all the enthalpies.

Martina

Forming bonds is exothermic because it releases energy, while breaking bonds requires an input of energy so it is endothermic.

Martina

Most of them are on the constants sheet and are given during the test.

Martina

This is true when the pressure is constant.

Martina

H stands for enthalpy and U is for internal energy.

Martina

Enthalpy is a state function, meaning that only the beginning and endpoints matter, not the path taken or the intermediate values. For this reason enthalpy is additive.

Martina

The energy is being used to change the state of matter for that period of time instead of to increase the temperature.

Martina

Enthalpy is additive because only the end value matters, not the actual pathway taken, no those values can be added.

Martina

I think we might get them back in discussions next, but it might be later.

Martina

I think that it is, unless you know whether the reaction releases energy or requires it.

Martina

You use it to convert between pressure and concentration since concentration is (n/V).

Martina

Yes you can use it find find pressure if you have the molarity (n/V) or vice versa.

Martina

Exothermic reactions release energy, so energy is basically one of the products. Endothermic reactions require energy so energy is a reactant. So when you increase energy it favors the other side.

Martina

I think you needs to understand how the protons or electron pairs are transferred, but you do not actually have to draw it.

Martina

Temperature is the only thing that affects the equilibrium constant, so it changes the value of k.

Martina

These are just logarithmic versions of Ka and Kb, their relationship is that they add up to 14.

Martina

I don't think you could calculate that without being given the temperature.

Martina

Gibbs free energy can help determine whether a reaction release or requires energy. I think this will be important later in the class but not much for this unit.

Martina

Pressure and volume have an inverse relationship. When a gas is condenses into a smaller space the pressure increases, and when the gas has more space the pressure decreases.

Martina

You do use units for concentration, but not the equilibrium constant because the units of products over reactants cancel out.

Martina

An ICE table has three rows in which you list the Initial molar concentration, Change in molar concentration, and Equilibrium molar concentration for all of the products and reactants. It can be used to determine the concentration of the equilibrium mixture.

Martina

I think all of these abbreviations are okay for the final.

Martina

You use these prefixes any time it is polydentate, so you would use it for oxalato, en, dien, and edta.

Martina

If the complex is negative you have to add -ate to the end of the metal. The only exception is iron and copper, which change to ferrate and cuprate.

Martina

I think you need to memorize all of the ones given on the list in his website.

Martina

Polydentate just means that it bonds at more than one site, hexadentate says the actual number of bonds it can make. Both are correct though.

Martina

Four myoglobin create a hemoglobin, and each myoglobin can carry one oxygen. So total 4 can be carried by a hemoglobin.

Martina

Any hydrogen attached to a F, O , or N , and any lone pairs on those atoms can make hydrogen bonds.

Martina

The chlorines are on the same side and bind to DNA twice, which stops cell division.

Martina

A sigma bond is a bond between two orbitals (s and s, s and p, etc) where they overlap end to end and can rotate.

Martina

I am not sure but I don't think we need to know bond order.

Martina

I don't think molecular orbital theory or bond order will be on it.

Martina

What is the difference between diamagnetism and paramagnetism?

Martina

I think that's all. You just need to memorize the hybrid orbitals.

Martina

Hybridization of two orbitals changes the shape because they combine to share electrons and become a different shape.

Martina

If it asks for the shape, then you have to say see-saw. If it asks for the electron geometry as well then it is trigonal bipyramid.

Martina

A bent molecule has a lone pair which pushes the other atoms away from it, causing a bent shape.

Martina

A sigma bond means that the orbitals overlap end to end. Sigma bonds also allow for rotation.

Martina

If the molecule has symmetry then the dipole moments likely will cancel out and make the overall molecule nonpolar.

Martina

Single electrons can still form a bond.

Martina

You just have to label one as a sigma bond and one a pi bond if its a double bond. If it is triple then one sigma and two pi.

Martina

Polarizability increases with size and negative charge. So larger anions have the highest polarizability.

Martina

Lone pairs are usually located in a place where they form fewer bond angles with other atoms. So in the See Saw shape they are located on the equatorial plane where they only interact with 2 bonds.

Martina

Suggest, giving reasons, which substance in each of the following pairs is likely to have the higher normal melting point
(Lewis structures may help your arguments): (a) HCl or NaCl

Why is the melting point of NaCl higher that HCL?

Martina

Yes, the lone pair repels the other bonds, causing the bond angle between them to be slightly less than what is expected.

Martina

Yes, a radical with a single electron is still considered a domain for the electron geometry.

Martina

What is an instantaneous dipole and how do you identify it?

Martina

They are the strongest intermolecular bonds but no stronger than ionic or covalent bonds.

Martina

A molecule has a dipole moment if it has a partial negative a positive charge due to uneven sharing or electrons.

Martina

It is harder to break the bonds in a more polarizable atom and covert it to a liquid or gas.

Martina

Polarizability increases toward Francium (like atomic radius) while polarizing power increases toward Fluorine (like elecronegativity)

Martina

Do you have to calculate formal charges for every lewis structure you draw, or only if it is specified in the question.

Martina

You can use the solid and dashed lines or you can draw all of the possible lewis structures and explain that the resonance is a hybrid of all of them.

Martina

I think you can usually tell it is a radical if there is an odd number of valence electrons.

Martina

Another way to think about it is FC= valence electrons - (number of lone pair electrons + number of bonds)

Martina

How much of polarizability do we need to know for the midterm? Thanks!

Martina

How do you determine if there is a dipole moment, and what exactly causes it?

Martina

It also helps to know that exceptions are in the third period because they can fill their d orbital with electrons as well.

Martina

Atoms like P, S, and Cl also can be an exception because they can accommodate more than 8 valence electrons.

Martina

Ionization energy is always positive because you need energy to remove the electron. Second ionization energy is higher because the charge difference between the positive nucleus and the electrons is greater, so it is even more difficult to remove another electron.

Martina

The resonance structure is a blend of the different possible lewis structures of a molecule. The bond lengths of the resonance structure will all be the same and will be somewhere between the lengths of all the possible bonds.

Martina

Parallel electrons have the same spin and will have the same sign for the spin magnetic quantum number while paired electrons have opposite spins so one will have a negative spin magnetic QN will the other will be positive.

Martina

Why is the electron configuration for Chromium [Ar] 3d5 4s1? Can someone please explain the exceptions to electron configuration rules?

Martina

Yes I think you need to know them for the s, p, d, and f orbitals.

Martina

What is the difference between an atom having a positive spin quantum number versus a negative one?

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