CHEMISTRY COMMUNITY

Aliya Jain 2B

I think this means that is a concentration cell. In this case you would use the nernst equation, but e standard is 0.

Aliya Jain 2B

Yeah im pretty sure youd be given both K values or enough information would be given to calculate one

Aliya Jain 2B

if the water is aqueous, i think it would be included

Aliya Jain 2B

have you tried log(5.839) / log(2.5)?

Aliya Jain 2B

when solving for strong acids/bases, the concentration of the acid is always equal to the concentration of hydroxide or hydronium because they dissociate completely. When solving for weak strong acids or bases, you must always put them in water and use an ice table to calculate the concentration of ...

Aliya Jain 2B

that is equal to ln(2) which is part of the formula to find the half life of a reaction

Aliya Jain 2B

calculate the mols of N2O5 present, and multiply it by the reaction rate.

Aliya Jain 2B

I'm pretty sure we can associate something that is first order with being unimolecular!

Aliya Jain 2B

I think that if something is unimolecular, the order of the reaction would be one. similarly, if something is bimolecular, the order of the reaction would be two.

Aliya Jain 2B

Integrate similarly to first order reaction, but now integrate -d[A]/[A]^2 which turns out to be 1/[A].

Aliya Jain 2B

Yeah! A concentration cell has the same ion on both sides, but different concentrations. I'm not sure how it can be compared to a galvanic cell though, sorry.

Aliya Jain 2B

i think its the orders of all the reactants added together!

Aliya Jain 2B

I think it asking whether the water has a larger reduction potential or the metal ion. Hope this helps :D

Aliya Jain 2B

I understand how to look at the table to find out whether the reduction potentials are a larger positive number for the metal ion or water, but I am a little confused on where to go after that. If the cathode has a really large negative reduction potential(which we don't want), doesn't that mean tha...

Aliya Jain 2B

They're the same thing, I think!

Aliya Jain 2B

What is a salt bridge used for? I’m kinda confused about their role in galvanic cells

Aliya Jain 2B

The Van't Hoff Equation can be used to calculate the k at a different temperature if change in enthalpy is known and is constant.

Aliya Jain 2B

We use platinum because we need solid to channel and donate the electrons. Platinum is a good electric conductor.

Aliya Jain 2B

If you need more H you would add hydronium (H+) to the solution.

Aliya Jain 2B

You balance the oxygens by using water, and balance the charges by adding hydroxide.

Aliya Jain 2B

The single line is for difference in phases, whereas the commas represent them in the same solution.

Aliya Jain 2B

I think a question will explicitly tell you if the system is open

Aliya Jain 2B

I think its because cl2 is used as both the oxidizing and reducing agent

Aliya Jain 2B

Since open systems are permeable to energy and matter, im pretty sure all thermodynamic equations can be applied

Aliya Jain 2B

I think so, because entropy is a state function so the pathway does not matter

Aliya Jain 2B

Im pretty sure that if there is a free expansion, work equals zero because the system does not have to counteract a compressive force

Aliya Jain 2B

lead has a significantly higher amount of particles( protons, neutrons, and electrons) than carbon which means it has a higher degeneracy, and thus a higher entropy.

Aliya Jain 2B

Yes, i think the equation shows the proportional relationship between possible microstates and entropy. I would use the equation of the question mentioned a quantity of particles and possible energy states

Aliya Jain 2B

I think it was when PD TV HUGS

Aliya Jain 2B

I think it's because we're looking for delta H per mole of C6H6. In that case, you take the delta H of the reaction and divide it by the coefficient of the reactant or product.

Aliya Jain 2B

I think we assume this because it says the reaction takes place in a single vessel, so there wouldnt be any changes in volume

Aliya Jain 2B

I think ionic bonds are breaking, but I think the dissolving of salts is a physical change

Aliya Jain 2B

I think the integral just shows how the work formula is derived, so I dont think we would need to know it for the midterm.

Aliya Jain 2B

Since C= q/delta T, you can divide 3.50 kJ by 7.32 K and get C=0.478 kJ/K. From there you can multiply that number with the change of temperature(2.47 kJ) of the calorimeter to find q of the calorimeter. The q of the reaction is the negative value of the q of the calorimeter

Aliya Jain 2B

I think a microstate is the way in we can arrange the energy of a system and as the amount of atoms in the system increases, the amount of possible microstates also increases. Knowing this value helps calculate entropy.

Aliya Jain 2B

degeneracy is the number of ways of achieving a given state. The equation to calculate this number is W= 2^n, which is why if there are 3 atoms, there are 8 possible microstates.

Aliya Jain 2B

Joules i think

Aliya Jain 2B

I they're found experimentally, so in a problem, they should usually be given

Aliya Jain 2B

I dont think so, because heat is always required during those phase changes

Aliya Jain 2B

what is the relationship between the Ka and how strong an acid is?

Aliya Jain 2B

im a little confused on how to convert pKa to Kb? I think theres multiple ways, but what's the easiest way to do it?

Aliya Jain 2B

I think since it's polyprotic, when the first H+ ion breaks off, it does so completely, which refers to the "very large Ka". When the second H+ ion breaks off, you use an ice table, but must recognize that there is already an initial concentration of hydronium from when the first H+ ion br...

Aliya Jain 2B

Yes I believe it's the change in reactant concentration, so you would take into account coefficients.

Aliya Jain 2B

HI is a strong acid so it breaks apart completely, meaning that the concentration of the acid is the same as the concentration of the hydronium ions. From there, you can convert to pH, subtract the pH from 14 to find the pOH, and convert back into hydroxide concentration.

Aliya Jain 2B

Find the initial concentration of the weak acid or base in each of the following aqueous solutions: (a) a solution of HClO with pH 5 4.60; (b) a solution of hydrazine, NH2NH2, with pH 5 10.20. Your K expression should read ([H30+][CLO-])/[HCLO]. Since you are given pH, you can find [H30+] using 10^-...

Aliya Jain 2B

5J.1 reads "Consider the equilibrium CO(g) + H2O(g) --> CO2(g) + H2(g). (a) If the partial pressure of CO2 is increased, what happens to the partial pressure of H2? (b) If the partial pressure of CO is decreased, what happens to the partial pressure of CO2? (c) If the concentration of CO is inc...

Aliya Jain 2B

k>1 does indicate that products are slightly more favored than reactants however I think k>10^3 guarantees favoritism.

Aliya Jain 2B

I think that decreasing the concentration of products will decrease the reaction quotient while increasing the concentration pf products will increase the reaction quotient

Aliya Jain 2B

Yes, both partial pressure and concentration can be used in ice tables

Aliya Jain 2B

The quick way is just knowing that when pressure is increasing, then the reaction will go towards the direction with less moles and when the pressure is decreasing, the reaction will go towards the direction with more moles. The longer way is realizing that when pressure is changing, the actual volu...

Aliya Jain 2B

What exactly does le chatelier's principle apply to? Is it just concentration of reactants/products, temperature, and pressure/volume or are there more factors that can be applied?

Aliya Jain 2B

dien is tridenate im pretty sure, and i think carbonate and nitrito might be ambidentate

Aliya Jain 2B

I think those are good, but maybe also sulfato? I'm not really sure if sulfato is considered bidentate though

Aliya Jain 2B

I thought that carbonate was bidentate due to its 2 oxygens with -1 formal charge, but I have seen in a lot of places that it is monodentate bc it has 120 degree bond angles.

Aliya Jain 2B

I think polydentates do affect shape of coordination compounds because they offer more than one binding site. For example, since en has two binding sites, it will increase the coordination compound by 2

Aliya Jain 2B

is sulfato bidentate since two oxygens have a -1 formal charge which can act as binding spots?

Aliya Jain 2B

A Lewis acid is an electron-pair acceptor and a Lewis base is an electron-pair donor.

Aliya Jain 2B

This is why acids with longer bonds are stronger, while acids with shorter bonds are acids. Strong acids with weak/long bonds can dissociate completely while weak acids with short/strong bonds cannot.

Aliya Jain 2B

An example of a strong acid is HI, which has long/weak bonds and can dissociate completely. An example of a weak acid is HF, which has short/strong bonds and does not dissociate completely.

Aliya Jain 2B

For each molecule, look at what the products of dissociation are because they will indicate whether they are acids or bases. For example, NH4Br will dissociate into NH4+ + Br-. NH4+ is able to give up a proton so the solution will be acidic.

Aliya Jain 2B

An oxoacid contains oxygen, contains at least one other element, and has at least one hydrogen atom bonded to the oxygen.
The oxoacids more readily lose a H+ if the resulting anion can be stabilized by electron withdrawing atoms.

Aliya Jain 2B

You just subtract 1 from the amount of bonding regions!

Aliya Jain 2B

viewtopic.php?p=2547&sid=0d36d6a0a83ae99de2b5592ede5e800f#p2547
Dr. Lavelle answered this question a couple years ago!

Aliya Jain 2B

The oxidation number of an atom is the charge that atom would have if the compound was composed of ions.

Aliya Jain 2B

For example, Ni (I) would represent the +1 oxidation number of nickel while Ni (II) represents the +2 oxidation number

Aliya Jain 2B

Then you can find the pOH by subtracting the pH you calculated from 14.

Aliya Jain 2B

Different atoms often have differences in electronegativity which causes them to be polar even if their geometry is symmetrical.

Aliya Jain 2B

Also, I think since the hydrogen atom is less electronegative than chlorine atom, there is a net dipole moment in the compound.

Aliya Jain 2B

You can also look at molecular geometry. Sometimes certain structures indicate polarity. For example since h2o has a bent structure, it is also a polar molecule.

Aliya Jain 2B

You can also use molecular geometry to find polarity. For example, lone pairs on oxygen in h2o cause there to be bent geometry, which thus indicates that the molecule is polar.

Aliya Jain 2B

I think that the hydrogen atom is less electronegative than the chlorine atom so, there is a net dipole moment in the compound. Also, the arrangement of the bonded pairs is asymmetric,

Aliya Jain 2B

Also, expanded octets can occur in all elements starting period 3 and below!

Aliya Jain 2B

Also, electronegativity refers to the ability of an atom in a molecule to attract shared electrons. Ionization energy does not refer to molecules, only unbonded atoms.

Aliya Jain 2B

We probably need to the know the general trend of electronegativity, which is proportional to ionization energy

Aliya Jain 2B

Since oxygen has the second highest electronegativity, it attracts electrons more strongly than hydrogen, thus causing an unequal sharing of electrons between the two atoms

Aliya Jain 2B

Formal charge should be considered after the octet rule is observed in most cases!

Aliya Jain 2B

Boron has too few of electrons to provide an octet for every atom.

Aliya Jain 2B

longer bonds are easier to break, so they are weaker. Shorter bonds are harder to break, so they are stronger.

Aliya Jain 2B

Since longer bonds are weaker and easier to break, they are more likely to be involved in a reaction. Stronger bonds are shorter, harder to break, and less reactive.

Aliya Jain 2B

Also, when you're deciding whether to use single, double, or triple bonds, make sure that the elements in the first or second period are observing the octet rule!

Aliya Jain 2B

Yes, the best structures have elements with 0 formal charge. If not, the most electronegative element should carry the negative formal charge.

Aliya Jain 2B

I'm pretty sure both the ionization energy and the electron affinity of an atom decrease as you go down a Group and increase as you go across a period. But there are some exceptions to these patterns.

Aliya Jain 2B

I'm pretty sure the electron configuration of neon is 1s22s2p6, so I think there are actually two electrons in the 1S sub-shell.

Aliya Jain 2B

Does this also include electron affinity and IE?

Aliya Jain 2B

"Place the following ions in order of increasing ionic radius: S^2-, Cl^-, P^3-." Since all of these ions have the same amount of electrons, are we supposed to take into account core charge?

Aliya Jain 2B

Another example is that nitrogen's electron affinity is lower than carbon's and that Neon's is not only lower than fluorine's, but is actually lower than lithium's.These exceptions are also due to electron configurations!

Aliya Jain 2B

The Schrodinger equation is used to find the allowed energy levels of quantum mechanical systems

Aliya Jain 2B

"The g-ray photons emitted by the nuclear decay of a technetium-99 atom used in radiopharmaceuticals have an energy of 140.511 keV. Calculate the wavelength of these g-rays" What is the unit keV?

Aliya Jain 2B

Im pretty sure it's used a lot because you can also isolate frequency in λv=C and subsitute it back into E=hv to find wavelength.

Aliya Jain 2B

The principal quantum number for the lower energy level involved is the same for each absorption line in a series. For example, Paschen series are the series of lines in the spectrum of the hydrogen atom which corresponds to transitions between the state with principal quantum number n = 3 and succe...

Aliya Jain 2B

1B.21 reads "A baseball must weigh between 5.00 and 5.25 ounces (1 ounce 5 28.3 g). What is the wavelength of a 5.15-ounce baseball thrown at 92 mph?" I understand the basic premise of the question, but I'm kind of confused about the conversations? Can someone explain the initial steps

Aliya Jain 2B

"A lamp rated at 32 W (1 W 5 1 J?s21) emits violet light of wavelength 420 nm. How many photons of violet light can the lamp generate in 2.0 s? How many moles of photons are emitted in that time interval?" Can someone explain the initial step to figure this question out?

Aliya Jain 2B

I'm not sure if this is what you mean, but the symbol ∝ is used for variables that are directly proportional to each other!

Aliya Jain 2B

Constructive interference happens when two waves meet so that their crests line up together, which results in a wave with a higher amplitude. In destructive interference, the crest of one wave meets the trough of another, resulting in a lower total amplitude. The Khan academy video about this is rea...

Aliya Jain 2B

For this question, I was able to use process of elimination, but I'm still pretty confused on the relationship between the frequency of electromagnetic radiation and the slope of the electric field. Does anyone know why they're related?

Aliya Jain 2B

Question 1A.11 asks: In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series. What is common to the lines within a series that makes grouping them together logical? Does anyone know how to approach this question? I'm a little confused on the conce...

Aliya Jain 2B

Avogadro's number should be used if a problem asks for formula units, atoms, or molecules. To convert something to molecules or formula units, multiple moles by Avogadro's number. An example of this would be problem E.9 parts a and b.

Aliya Jain 2B

Since phosphorus and chlorine are covalently bonded together, they make a covalent compound. Simple covalent compounds are generally named by using prefixes to indicate how many atoms of each element are shown in the formula. Also, the ending of the last (most negative) element is changed to -ide. T...

Aliya Jain 2B

Avogadro's number was given to me on formula sheets in my high school chemistry class, so I think it could be on there, but it might be safer to just memorize it.

Aliya Jain 2B

I'm pretty sure they're all right. Any zeros between two significant digits are significant. Also, a final zero or trailing zeros in the decimal portion only are significant.

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