CHEMISTRY COMMUNITY

Jamie Lee 1F

You should end up with the same result, i guess we just always try to pick out the easiest choice What makes it the easiest choice, like how do you know Sometimes some concentrations are easier to work with than others. For example, say trial 2 is just double trial 1 while the third trial is some r...

Jamie Lee 1F

Brian J Cheng 1I wrote:As Naneeta says, they're uncommon. Dr. Lavelle specifically told us to focus on 0, 1, and 2 order reactions (zero order, unimolecular, and bimolecular). Zero order == nonmolecular?

I think a zero order reaction would just have no molecularity at all.

Jamie Lee 1F

The problem will usually tell you if it is a fast or slow mechanism:) also hi hailey

Jamie Lee 1F

Adsorption is when gas or solution binds to the surface of a catalyst at active sites, versus absorption which is when solution is basically soaked into a structure.

Jamie Lee 1F

You are usually given these values. If it's not explicitly stated which is which, then the positive one is usually the cathode and the negative is the anode.

Jamie Lee 1F

n is the number of electrons being transferred in the redox equation.

Jamie Lee 1F

A reducing agent is what is "doing" the reducing in the reaction and ends up being the oxidized element. On the other hand, the oxidizing agent is what "does" the oxidizing and ends up as the reduced element.

Jamie Lee 1F

Intermediates are produced in a step, then are consumed in a later step. It's kind of like when you are balancing redox reactions and cancel out the electrons from both reactions.

Jamie Lee 1F

I usually try to check over my answers, but since I usually never catch mistakes just by looking at my work, I redo the problems I really need to check. I then compare my original work and my later work and make sure it was correct. Also, just double checking your steps as you go is helpful.

Jamie Lee 1F

Is part D supposed to say $Cl_{2}(g)\rightarrow HClO(aq) + Cl^{-}(g)$ instead? The textbook says $Cl_{2}(g)$ is both a reactant and a product.

Jamie Lee 1F

Eº is E at standard conditions.

Jamie Lee 1F

Cobalt is a solid transition metal.

Jamie Lee 1F

Electrons are transferred, so there has to be another to accept or donate that singular one.

Jamie Lee 1F

When Joules and moles are used in the equation, use 8.314 J·K-1·mol-1.
If liters*atm per moles are used, use 0.0821 L·atm·K-1·mol-1.

Jamie Lee 1F

Cu is the anode since it is losing electrons, and M is the cathode since it is gaining electrons. (I remember this by Red Cat and An Ox: Reduction-Cathode, Anode-Oxidation :)).

Eº=Eº(cathode)-Eº(anode), so you would plug in the voltages to solve for Eº(cathode).

Jamie Lee 1F

When standard reduction potential is positive, it is spontaneous.

Jamie Lee 1F

I think you are referring to R, or the gas constant.
When Joules and moles are used in the equation, use 8.314 J·K-1·mol-1.
If liters*atm per moles are used, use 0.0821 L·atm·K-1·mol-1.

Jamie Lee 1F

Oxidation numbers are the "act" of electrons moving, while formal charge is what the atom "wants" to do with its electrons.

Jamie Lee 1F

Reactions at equilibrium usually have a º symbol. So, ∆Gº=-nFEº would be at equilibrium.

Jamie Lee 1F

Kristina Rizo 2K wrote:What is the numeric value for the faraday constant? I didn't write it down during lecture.

96,485 C·mol-1

Jamie Lee 1F

Voltage is the potential difference between two electrodes and measures the chemical potential for a redox reaction to occur.

Jamie Lee 1F

When the system does work, it should be negative since energy is leaving the system. If work is done on the system, energy increases so it would be positive.

Jamie Lee 1F

N refers to the number of electrons being transferred.

Jamie Lee 1F

N signifies the number of electrons are transferred.

Jamie Lee 1F

Adding an inert gas does not change the equilibrium constant.

Jamie Lee 1F

Enthalpy is the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume (H = U + PV)

Jamie Lee 1F

Warm water evaporates rapidly and since this is an endothermic process, it cools the water and allows it to freeze more readily.

Jamie Lee 1F

How is change in entropy calculated? What are its units? It really depends on the reaction-- whether it is reversible or irreversible, and what kind of transfer is occurring (between two reservoirs, from/to a heat reservoir, etc..). However if given the entropy value of the final and initial states...

Jamie Lee 1F

He was trying to draw a puffer jacket! Insulation prevents a system from transferring energy or matter with its surroundings. Some examples of an isolated system are a bomb calorimeter and a thermos container.

Jamie Lee 1F

GFolk_1D wrote:Are deltaH and q interchangeable?

At constant pressure, qp = deltaH. Otherwise, they are not interchangeable.

Jamie Lee 1F

q refers to heat transfer, while H refers to change in enthalpy (the total potential energy of a system).

Jamie Lee 1F

Standard reaction enthalpy is the heat given off or absorbed during reaction, while standard enthalpy of formation is the enthalpy change between the elements in their standard state (reactants) and the compound (product).

Jamie Lee 1F

A gas is ideal if the molecules do not attract or repel each other, but collide elastically and randomly. Also, ideal gas molecules should take up no volume.

Jamie Lee 1F

Standard enthalpy of formation equals 0 whenever the element is in its standard state, since they are not formed.

Jamie Lee 1F

A state function is a property of a system that depends on only the current state, irregardless of what path was taken to get there. Some examples include temperature, pressure, and volume. Enthalpy is considered a state function because it depends on the initial and final states, not the path betwe...

Jamie Lee 1F

Heat capacity is strongly influenced by external factors such as weight, while specific heat measures a substances ability to heat a mole of substance by 1 degree C; since there is a universal weight that is used, the only factors taken into account are the type of substance it is, making it an inte...

Jamie Lee 1F

In order to get Qc, you have to us [products]/[reactants. However, in this problem, you have to change mmol to mol, and put that value of moles over 0.5 L to find M, or Molarity. Once you use these conversions, [SO3]^2/[SO2]^2[O2] should give you Qc=6.9.

Jamie Lee 1F

No, in calculation you should get the same thing since 1 times anything is still that value. Just make sure to keep sig. figs. in mind.

Jamie Lee 1F

Amphoteric means a substance can act as both and acid and a base, while amphiprotic means a substance can both donate and accept protons.

Jamie Lee 1F

I don't think there is an explanation besides the fact that keeping standard conditions makes consistent the results.
The standard state temperature is 298 K.
All gases are at 1 atm pressure and all solutions are at 1M concentration.

Jamie Lee 1F

You can think of heat as either a reactant or a product. When heat is being released, the reaction is exothermic, and heat is product. Conversely, when heat is being absorbed, a reaction is endothermic, and heat is a reactant.

Jamie Lee 1F

The problem should state 2HD ⇌ H2 + D2, I think you misplaced a reactant on the product side :)

So with this, there would be no change since there is an equal amount of moles of gas on either side.

Jamie Lee 1F

Liquids and solids don't necessarily dissolve in solvent, which is a main component of "concentration", which is then the focus of equilibrium calculations.

Jamie Lee 1F

If K is less that 10^-3, then x is negligible.

Jamie Lee 1F

41 is two sig figs, so your answer should also be two sig figs, so 1.7 x 10^3!

Jamie Lee 1F

I think a rule of thumb in all calculations is to leave the rounding for the end for accuracy.

Jamie Lee 1F

Kc is defined by molar concentrations, while Kp is defined by partial pressures of gases. You typically use brackets for K and Kc, and parentheses for Kp.

Jamie Lee 1F

No, solid and liquid concentrations usually do not change during reaction since nothing is dissolving, whereas gaseous and aqueous solutions do.

Jamie Lee 1F

Their concentrations usually do not change during reaction, whereas gaseous and aqueous solutions do. In order for concentration to change, something must dissolve in something else; liquids and solids don't dissolve and therefore aren't taken into account in equilibrium calculations.

Jamie Lee 1F

A reaction tends to favor whatever side needs more or less "substance" to reach equilibrium. If the amount of product decreases, the reaction will favor the product side as to balance the reactants and products again.

Jamie Lee 1F

Aqueous solutions dissociate and have a very strong effect on concentration, whereas liquids and solids do not. Since k quantifies the rate of chemical reactions, solids and liquids usually are not taken into account because their concentrations are not strong enough.

Jamie Lee 1F

I think you really just need to know the 6 strong bases and know those are the ones that completely dissociate. The rest wouldn't completely dissociate, and it is likely that you would be given values for calculations to determine how strong or weak an acid is. Hopefully that made sense! Would thos...

Jamie Lee 1F

I think you really just need to know the 6 strong bases and know those are the ones that completely dissociate. The rest wouldn't completely dissociate, and it is likely that you would be given values for calculations to determine how strong or weak an acid is. Hopefully that made sense!

Jamie Lee 1F

Intermolecular forces exist between surrounding molecules while intramolecular forces are within molecules and hold atoms together.

Jamie Lee 1F

If a weak acid was very highly concentrated, as compared to a strong acid at a very low concentration, the pH of the weak acid could be the same or even higher than that of a strong acid.

Jamie Lee 1F

Adding on to that, we have been using Bronsted more due to conjugate acid and base pairs which don't exist by the Lewis definition.

Jamie Lee 1F

A chelate is a complex that has one or more ligands bonded to it that forms a ring around the central metal atom.

Jamie Lee 1F

You're basically just being asked to write the equation of the dissociation of the acid in water. So you would show the "removal" or dissociation of a proton.

Jamie Lee 1F

Any acid that has a bonded oxygen and a hydrogen. HNO3, H2SO4, and H3PO4 are some examples of oxyacids.

Jamie Lee 1F

For 6B.5 part d, I first found M2 using M1V1=M2V2, and set M2 as my concentration of OH- ions. Then, I used -log([OH-]) to find pOH, which should give you 3.15. You would then subtract that from 14 because pH+pOH=14, and you should get 10.85.

Jamie Lee 1F

A polar bond forms when one atom has a greater attraction for electrons than do the other atoms, this pull of electrons is called electronegativity. So, the greater the electronegativity, the greater the polarity of the molecule. In water, for example, oxygen has a greater pull on electrons than the...

Jamie Lee 1F

There are some questions in 6B that ask you to find pH. For example, you can go from the given concentration of an acid to pH by using -log([H3O+]=pH. You could also be given an M1V1=M2V2 type question like 6.B #5.d. The last question form I can think of is being asked to find pOH, and converting th...

Jamie Lee 1F

Electron geometry considers all electron dense regions, while molecular shapes only consider the present atoms. For example, in NH3, there are 3 bonded atoms, and 1 lone pair. There are 4 electron dense regions, so the electron geometry would be tetrahedral. However, there are only 3 bonded atoms af...

Jamie Lee 1F

Also, sigma bonds are always found in bonding, they are the first bonds to form, so any single bond will only be a sigma bond. Any bond added after that (double or triple bond) will be a pi bond.

Jamie Lee 1F

Technically they are the same thing so I don't think it matters, you would most likely get a problem correct with either name. Lavelle used bent in his lecture though.

Jamie Lee 1F

Usually Carbons are attached to each other, and Hydrogens are attached to carbons, so you end up with a long chain of Carbons with single bonded Hydrogens, or whatever atom you're given, to fulfill octet rules.

Jamie Lee 1F

Each single bond a central atom has attaches to it is a sigma bond, every additional bond added to the initial single bond (double or triple bond) is a pi bond. So in the case of SF6, S has 6 single bonded F's, so it has 6 sigma bonds and no pi bonds. NO3- on the other hand has 2 single bonds and 1 ...

Jamie Lee 1F

For number #2, X I understand why the pairs (CH3CH2CH2CH3 & CH(CH)3, H2S & H2O, KI & KCl) are stronger than each other, but how do you know that H2S and H2O have stronger interactions than the hydrocarbons, and that KI and KCl have stronger interactions than the others?

Jamie Lee 1F

The trigonal planar notation would look like AX3, which means there are three bonding atoms and no lone pairs. Trigonal pyramidal would look like AX3E, which means there are three bonding atoms and one lone pair, or 4 electron dense regions.

Jamie Lee 1F

You would use de Broglie whenever you're dealing with a particle that is not light, and has mass.

Jamie Lee 1F

The lone pairs repel the bonded molecules more, thus pushing them together and lessening the bond angles.

Jamie Lee 1F

I'm pretty sure you would either use the electronegativity chart, or look a the molecule itself. If the molecule is asymmetrical, it will be polar, but if it is symmetrical then it will be nonpolar.

Jamie Lee 1F

You would use the rule, "like dissolves like", and the fact that water is a polar molecule. The more electronegative a molecule is, the more polar it is, so as polarity increases the more likely a molecule is to dissolve in water.

Jamie Lee 1F

Could someone please explain 8b please? I used the photoelectric effect equation relating kinetic energy, energy of the photon, and the work function, but for some reason I'm not getting the correct answer. What answer did you get? I'm having the same trouble and wondering if maybe we made the same...

Jamie Lee 1F

Can someone explain to me the concepts behind 10a? I am confused on why it is Aluminum. Thanks Aluminum is larger than Silicon because the effective nuclear charge is stronger in Silicon, which means that the electrons are pulled more strongly towards the nucleus mostly because there are more of th...

Jamie Lee 1F

Could someone please explain 8b please? I used the photoelectric effect equation relating kinetic energy, energy of the photon, and the work function, but for some reason I'm not getting the correct answer.

Jamie Lee 1F

For Dino Nuggets 6a, what equation do we need to use ? ive been trying to use different one (because theres a lot for E) and that molar mass is messing me up. I used de Broglie's since light isn't involved. Also, make sure you convert the molar mass to mass using Avogadro's... that also might be me...

Jamie Lee 1F

Can someone explain how to do #5 from this problem set? First, you want to find your initial molarity since it isn't given to you. You would use the first set of information to do so. You would have one flask with 5.00 grams of KMnO4 (which you would convert to moles). To find the molarity of this ...

Jamie Lee 1F

Isopropyl alcohol, used in rubbing alcohol, is a compound containing only C, H, and O. What is the empirical formula of isopropyl alcohol if you find that 0.255 g of the compound gives 0.561 g of CO2 and 0.306 g of H2O when burned completely in excess oxygen? Can someone please help get started on ...

Jamie Lee 1F

I agree^. I also tend to use scientific notation when numbers become larger than the hundreds. Once in the thousands, I usually use scientific notation to keep myself from losing track of 0's. It definitely needs to be used to satisfy sig fig requirements sometimes.

Jamie Lee 1F

The total mass of the relative parts of the compound will have to add up to 1 or 100%, since you're given all components of the compound. The percentages should always add up to 100.

Jamie Lee 1F

Any electron configuration can be written in shorthand, so you can write ground-state or excited-state configurations using shorthand. Thank you! This helps, what are the differences between ground-state and excited-state configurations? In ground-state, atoms have the least possible amount of ener...

Jamie Lee 1F

Lattice energy is the energy given off when oppositely charged ions in the gas phase come together to form a solid.

Jamie Lee 1F

Any electron configuration can be written in shorthand, so you can write ground-state or excited-state configurations using shorthand.

Jamie Lee 1F

There are several elements that are anomalies when it comes to electron configuration, such as Copper, Silver, Gold, Palladium, Chromium, and Molybdenum. These elements designate more electrons to their d-subshells from the s-subshells for more stability. Unfortunately, you just have to know which o...

Jamie Lee 1F

I think question 2A15 is asking what is the likely charge formed by the given elements, rather than what elements it would form ions with based on its charge. The answer is +3 because Ga is "willing" to give away 3 electrons. Hopefully I'm understanding your question correctly!

Jamie Lee 1F

The more protons that are located in the nucleus, the stronger the pull is for the electrons, so the electrons are "geographically" much closer to the center of the atom.

Jamie Lee 1F

In high school, I learned to think of electron affinity as the "love an atom or molecule has for an electron". Usually, elements with electron shells that are almost filled tend to have greater electron affinities, or, they want to fill their shells more readily than other elements. For ex...

Jamie Lee 1F

If the protons and electrons are moving at the same velocity, it would mean that the protons have a shorter wavelength. However, if they are moving at the same momentum it would mean they have the same wavelength.

Jamie Lee 1F

Electrons that have the same value of n (principle quantum number) are in the same shell. Period 2 (for example) elements are all in the same shell. Electrons with the same l value (orbital shape) are in the same sub-shell. These would be the s-block, p-block, d-block, and f-blocks. An orbital is ma...

Jamie Lee 1F

He could have used any element, not just Neon, as an example. Neon is a noble gas and has a full electron shell so it is stable without any charge. I think it was just easiest to show that the listed ions are isoelectronic with Neon because it is already stable. But you could say the same for Cl- an...

Jamie Lee 1F

Yes, speed of light (c) is a constant and will always be 2.998 x 10^8.

Jamie Lee 1F

Lambda is the Greek letter used for wavelength, and "v" is frequency.

Jamie Lee 1F

Yes, you use E=hv to find the energy of a singular photon.

Jamie Lee 1F

R is the symbol for the Rydberg constant, which is 3.28984*10^15 Hz.

Jamie Lee 1F

Yes, when an atom absorbs energy, its electrons jump to higher energy levels, and jump back down again. Each jump releases a certain amount of energy that corresponds to a specific wavelength of light. Since each element has its own emission spectrum, you can use the wavelengths of light to compare ...

Jamie Lee 1F

You first have to find both grams and moles of each given atom- C, H, and N. Then, find the mass of O by subtracting the total mass of C, H, and N from the given amount of grams of caffeine (0.376 g). You convert that mass to moles. Divide all of the molar amounts by the smallest and find the empiri...

Jamie Lee 1F

According to the Arrhenius definitions, acids "release" their H+ ions in water so they are considered aqueous.

Jamie Lee 1F

Usually you would only use the values given in the problem to decide how many sig figs to use. There are usually way less than eight sig figs on given values so it shouldn't matter in your answer anyways.

Jamie Lee 1F

I liked the dartboard example that Dr. Lavelle used- in that higher accuracy would mean that the darts would hit the bullseye, and higher precision would mean that darts would hit the same spot (regardless of position) again and again.

Search found 106 matches