CHEMISTRY COMMUNITY

Alen Huang 2G

I think the salt bridge contains spectator ions that would cancel out the charges on each side of the galvanic cell in order to allow electron flow to occur.

Alen Huang 2G

I believe you would use the equation delta G = -nFE naught. You can always use E = E naught - RT/NF lnQ to find E naught given E

Alen Huang 2G

In an acidic solution add H+ to balance the equation and in a basic solution add OH- to balance the equation.

Alen Huang 2G

I use the acronym OIL RIG, oxidizing loses electrons, reducing gains electrons

Alen Huang 2G

The oxidizing agent is the one that is oxidizing another species (so oxidizing agent is reduced) and the reducing agent is the one that is reducing another species (so reducing agent is oxidized)

Alen Huang 2G

If Q is greater than K then the reverse direction is favored and if Q is less than K then the forward direction is favored.

Alen Huang 2G

At equilibrum delta g is 0 while delta g naught is delta g under standard conditions so i don't think it will change.

Alen Huang 2G

I think inert conductor just means some metal to enable electron flow and the metal doesn't affect the reaction.

Alen Huang 2G

Why is it that when delta S total is positive that the reaction will be spontaneous?

Alen Huang 2G

Why is it that for a reversible process the delta S total is equal to 0?

Alen Huang 2G

I believe you just have to pay attention to the units you are given and match the correct R value so that your units cancel out.

Alen Huang 2G

I usually just add 273 to my celsius to get kelvin

Alen Huang 2G

Sorry I am a little overwhelmed by all the equations we have in this topic, can someone list out the equations and under what conditions can we use them?

Alen Huang 2G

I believe reversible expansions are isothermal because as the system is doing work, heat is gained by the system and the change in internal energy is zero

Alen Huang 2G

Degeneracy is the number of possible states something can exist in while entropy is a measure of disorder

Alen Huang 2G

If you take a look at the units you are given in the problem you should find an R constant that matches those units.

Alen Huang 2G

If a system is doing work it is negative because it takes energy and if work is being done on a system it is positive because it is gaining energy

Alen Huang 2G

Delta U can be 0, an example of it would be an isolated system.

Alen Huang 2G

I believe pressure can be added to a closed system by compressing it like with a piston.

Alen Huang 2G

Delta U is the change in internal energy which is just the heat added/removed from the system plus the work done on/by the system.

Alen Huang 2G

If an inert gas is added why do the equilibrium partial pressures not change?

Alen Huang 2G

To convert back to ka or kb from pka/pkb you just take 10^-(pka/pkb)

Alen Huang 2G

You need to use moles/liter since there is squaring involved sometimes, the values will be different if you don't use moles/liter

Alen Huang 2G

Can you determine bond enthalpy values from the standard enthalpy of formation values?

Alen Huang 2G

You can assume x is insignificant if the ka or kb value is below 10^-4, but make sure you use the 5% rule to make sure!

Alen Huang 2G

When pH is smaller than pKa it means the surrounding solution is a stronger acid than the pKa solution and therefore the surrounding solution will donate protons to the pKa solution making the HA concentration increase and thus the solution is neutral.

Alen Huang 2G

Start by comparing the pH and the pKa, since pH is lower it means that the surrounding solution is more acidic than the HA acid and so the surrounding solution will donate protons to the A- in the solution which will increase the concentration of HA in the solution making it neutral.

Alen Huang 2G

Ka1 is the ka value for the first deprotonation and ka2 is the ka value for the second deprotonation. If ka2 is significantly less than ka1 then we can say that second deprotonation doesn't really occur and is negligible.

Alen Huang 2G

To decide which one to use you would need to look at the units for the values that you calculated/given and use the constant that matches those units.

Alen Huang 2G

Yes! Endothermic reactions will always have a positive enthalpy change and exothermic reactions will always have a negative enthalpy change.

Alen Huang 2G

Autoprotolysis is the proton transfer between 2 identical molecules. One as an acid and the other as a base.

Alen Huang 2G

You would need to setup an ICE table and you should end up with a quadratic equation and solve for x. Since x is the concentration of H3O+ produced you can take -log(x) to get pH

Alen Huang 2G

I believe the strength of the acid and base play a part and the stronger acid/base would have a greater effect. If they're both strong then the solution would be neutral.

Alen Huang 2G

A larger Ka would indicate a stronger acid while a larger Kb would indicate a stronger base.

Alen Huang 2G

P=pressure, v= volume, n= number of moles, R= gas constant, T=temperature

Alen Huang 2G

At equilibrium, the rates of the forward reaction and the reverse reaction are the same. That is the definition of equilibrium.

Alen Huang 2G

If pressure is increased the system would want to decrease the total pressure so it would shift towards the side with less moles since that would decrease the pressure.

Alen Huang 2G

0.5 is Liters since concentration is calculated using moles/liters and we were given that the container is 500 mL

Alen Huang 2G

Can someone remind me what the ideal gas assumptions are? Like how do they deviate from the real world gases.

Alen Huang 2G

Inert gases don't affect the chemical reaction and don't react with anything and therefore the concentrations remain the same. As for how it increases the pressure it's because there is now a new gas in the container so the pressure would increase even though it doesn't interact at all.

Alen Huang 2G

The ions of strong acids/bases would be their conjugate acid/base which is a weak acid/base and we know that weak acid/base will not interact much with water when compared to strong acid/bases.

Alen Huang 2G

How do we know that Al 3+ forms a complex with water and that it'll react with more water to form hydronium ions?

Alen Huang 2G

All 3 of the lone pairs would occupy the equatorial position and cancel each other out so the 2 bonded atoms will be in the axial position and thus linear

Alen Huang 2G

I don't believe so, since trans- would suggest that the two atoms are on opposite sides and if they're on opposite sides they can't bind to the same atom since one would be facing away from the transition metal atom

Alen Huang 2G

How do you know when hybridization is required instead of using normal orbitals? Or are all bonds hybridized?

Alen Huang 2G

Water is a liquid because its a solvent, whereas the solutes dissolved would be aqueous

Alen Huang 2G

Try Hexamminecobalt(III) Chloride.

I think u only need 1 a for hexammine and also you spelt cobalt wrong.

Alen Huang 2G

Why do resonance structures form a more stable molecule?

Alen Huang 2G

Bond length and stability of anion are the two things Dr. Lavelle mentioned.

Alen Huang 2G

The answer is just octahedral, I believe the other shapes that have a coordination number of 6 are just not very common

Alen Huang 2G

Yes double bonds count as 2 bonds in this case

Alen Huang 2G

Will we ever have to make ring structures as lewis structures like the example on sapling hw?

Alen Huang 2G

In the lecture today Dr. Lavelle said that the ideal geometry for ligands is atom with lone pair, spacer, spacer, atom with lone pair. I was wondering if 2 spacers are necessary for the ligand to be big enough to bind to a transition metal or is one spacer enough but just not ideal. What about ligan...

Alen Huang 2G

Do all molecules bond using hybrid orbitals? Are there cases where a molecule doesn't need to use hybrid orbitals to bond?

Alen Huang 2G

CHI3 has more electrons thus higher dispersion forces so its intermolecular forces are stronger than the intermolecular forces in CHF3 since both molecules have dipoles the only difference in their intermolecular forces is the strength of the dispersion forces. Stronger forces mean more energy is re...

Alen Huang 2G

It will have a dipole moment if the bond is polar and do not cancel out. CHCl3 is has polar bonds but is not symmetrical since H has lower electronegativity than Cl, Cl is going to have a slightly negative charge while H will have a slightly positive charge thus creating a dipole moment. CCl4 is sym...

Alen Huang 2G

Dipole refers to the charges on a molecule, for there to be a negative side there must also be a positive side

Alen Huang 2G

Can d orbitals not form sigma/pi bonds? What about the atoms with expanded octets that have valence electrons in the d orbital, how do those electrons bond?

Alen Huang 2G

Do hybrid orbitals like the sp3 example have shapes like regions of electron density like s orbitals or p orbitals?

Alen Huang 2G

In this case, Br has the higher electronegativity so to create a bigger difference we need the smallest electronegativity and as you said electronegativity increases going up the periodic table so Ba has a smaller electronegativity than Be

Alen Huang 2G

Can someone summarize the trend for increasing ionic/covalent characters.

Alen Huang 2G

Polarizability is how easily the electrons can be distorted while polarizing power is how strong it can distort another electron cloud. Think about polarizing power as a magnet and the thing that is being polarized as something that's attracted to a magnet like nails. The smaller the radius and grea...

Alen Huang 2G

Bonding pairs are more stable and don't interact as much as lone pairs do so lone pair repulsions are greater than bonding pair repulsions.

Alen Huang 2G

Yes I believe so! The symmetry of the structure is important in determining whether the whole molecule is polar or not because two polar bonds can cancel each other out if they are opposite of each other and create a nonpolar molecule overall.

Alen Huang 2G

I think for the lecture examples they are all ionic bonds since their electronegativity difference is above 2 if I'm not mistaken but F- would have a higher electronegativity than I-. I- forms a weaker bond because its size is bigger than F-, the outer electron is not held as tightly and would be at...

Alen Huang 2G

I'm assuming the question would hint at finding the most likely lewis structure for this molecule, also its just a good idea to check the formal charge just to make sure you drew the structure correctly.

Alen Huang 2G

Using the lowest ionization energy atom as the central atom is just a guideline, I'm assuming N was used as the central atom due to the symmetry the polyatomic ion would have

Alen Huang 2G

As opposed to just having the s and p orbital, the d orbital adds enough space for 10 more electrons to be shared.

Alen Huang 2G

A nodal plane is just where theres a zero probability of finding an electron, if you think about the wave function the place where theres a node is on that nodal plane

Alen Huang 2G

energy level 2 can contain the subshells s and p and s subshell contains 1 orbital while p subshell contains 3 orbitals so 4 orbitals in total

Alen Huang 2G

5 d orbitals means that there are 5 states the electron in the d subshell can be in, each orbital can contain 2 electrons so 10 electrons in d subshell

Alen Huang 2G

A subshell would be like 2p and orbital would be the state that the electron is in such as 2px

Alen Huang 2G

If you gain an electron the repulsion between electrons get stronger and moves them further away from the nucleus and increasing the ionic radius

Alen Huang 2G

Nevermind I found it

Alen Huang 2G

I can't find problem 1.E.27

Alen Huang 2G

Are the textbook problems listed in the review referring to Topic 1E Exercise or Focus 1 Exercise, and where can I find the answers to them?

Alen Huang 2G

ml doesn't only range from -1 to 1, when l is 2 ml ranges from -2 to 2 cause when l = 2 we're talking about the d subshell which has 5 orbitals and -2 to 2 each represent one of those orbitals

Alen Huang 2G

^ I agree with everything except the last one, it is talking about the 6p subshell but the ml number gives one of the orbitals which can only fit 2 electrons so the answer is 2.

Alen Huang 2G

^ I believe you would always be given the mass or at least be given other information that could assist you in calculating the mass

Alen Huang 2G

Lyman series involves electrons jumping down to the first energy level and this is usually UV light while Balmer series involves electrons jumping down to the second energy level and this is usually light in the visible region.

Alen Huang 2G

How come electrons fill up orbitals with an up spin instead of completely filling that orbital with an up and down spin before moving on? So like why do the last 2 electrons in a carbon atom occupy the 2px state and the 2py state instead of 2 electrons in the 2px state.

Alen Huang 2G

How come during the lecture Rydberg's constant shows as 3.29 x 10^15 s^-1 but when I look it up it shows up as 1.09 x 10^7 m^-1?

Alen Huang 2G

Electrons are only ejected when the incoming energy is greater than the work function but electrons can be excited with any amount of energy, given that it is enough to jump at least one energy level, before that.

Alen Huang 2G

Lyman series is just any electron jumping down to the first energy level while Balmer series is any electron jumping down to the second energy level, I believe there are other series names for the higher energy levels as well.

Alen Huang 2G

Electron transition just means the electron is changing energy levels whether that is jumping up an energy level or dropping down.

Alen Huang 2G

Lyman series just means that the electron jumps from any energy level that is higher than 1 down to the first energy level while Balmer series is just any energy level higher than 2 down to the second energy level. I believe there are other series names for the higher energy levels.

Alen Huang 2G

Imagine you have a lamp and a piece of paper, to increase intensity you would move the piece of paper closer towards the light source which means that the light will be less spread out and more protons will hit the paper.

Alen Huang 2G

It can be really helpful on questions like these if you just write out the units. For example, (2.92 grams)(?) = ? moles, you know that you need to convert grams to moles which means u need mole per gram, which is just the molar mass.

() being multiplication.

Alen Huang 2G

Something that helps a lot when doing problems like these is to make sure to write down what you're given and what you're trying to find. For example, you're given the mass of the products and you need to find the mass of the reactant in order to determine empirical formula.

Alen Huang 2G

I would first figure out the number of moles of substance X in that 10 mL. Since we know the molarity and the volume, n = M(L). Next we need to figure out the molarity after doubling 90 times, M = n/L, 2^90 is the same thing as doubling volume 90 times. Then you multiple the molarity by 10 mL or 0.0...

Alen Huang 2G

I believe you always need to balance it, hydrocarbons can undergo combustion and there are many different molecular formulas which means the number of moles of carbon and hydrogen will be different with each combustion example. So it is important to always balance the formula first.

Alen Huang 2G

If the answer to a question is supposed to have 4 significant figures and the answer that I put only has 3 will that be considered wrong? Also, can I ever round without considering sig figs? If not, when do I need to consider sig figs on exams?

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