CHEMISTRY COMMUNITY

Jake Gordon 1A

Also I think Graphite a non metal can conduct electricity

Jake Gordon 1A

comma separates species in the same states

you have to add a conductor if there is no conducting metal or mercury Hg liquid or graphite I believe

Jake Gordon 1A

I remember that the three plots vs time that we are working with are [A], 1/[A], and ln[A] but what does it mean if we get a straight line for each individual graph?

Jake Gordon 1A

All of the above answers look good, but for this class, my TA said that we only need to add it if there is no conducting metal in the equation the only exception is Hg liquid

Jake Gordon 1A

I agree, I think the calculated k only applies at the given temperature. If you increase temperature the molecules have more Kinetic energy and this will alter the probability that they run into each other with proper orientation and sufficent energy and therefore k must be a different value to have...

Jake Gordon 1A

In a concentration cell the solutions and electrodes are the same material. In class the example was Ag + solution and Ag electrodes. This contrasts from the galvanic cells we saw before with different solutions and metals for example Zn and Cu. In the concentration cell the electrons will flow from...

Jake Gordon 1A

I think it says the reaction rate's change dependence on a change in concentration. In other words a 0 order would not rely on concentration change to change the rate and a third order would have a relatively high change in rate if the concentration is altered.

Jake Gordon 1A

Is E for a reaction that has not started the equivalent of E knot for a standard battery?

In other words. If E knot is the max voltage for a standard battery is E for a reaction that has not started the max voltage for a non standard cell?

Jake Gordon 1A

n is the number of moles (stoichiometric coefficent) for the electrons transferred in the balanced redox reaction

Jake Gordon 1A

I forget, why did Professor Lavelle switch from ln to log base 10 for the nernst equation.

Jake Gordon 1A

I think one way is that it is filled with cations and anions and the loss of electrons of the anode solution makes it positive pulling the anions out and the cathode solution gains electrons and become more negative and will draw out the cations out of the compartments of the salt bridge. I know the...

Jake Gordon 1A

oxidation state of any pure element is 0 ex Cu a charged monoatomic ion is just equal to the charge ex Cl- is -1 and Ag+ is +1 diatomic ions must add up to the total charge ex HCO3- H is +1 C is +4 and 3 oxygens O is -2 each for a total of -1 group one is +1 group 2 is +2 carbon is usually +- 4 oxyg...

Jake Gordon 1A

The compound or element that gets reduced is the oxidizing agent and the compound or element that gets reduced is the oxidizing agent.

Jake Gordon 1A

Free expansion irreversible refers to typically isothermal expansion against a vacuum. Delta U, q, and w will all be 0 however a change in entropy will be equal to the entropy change for reversible isothermal expansion using the same values

Jake Gordon 1A

It can help determine whether a reaction is thermodynamically favorable and if so, at what temperatures, also, delta G is the energy available to do work. If delta G decreases then heat is released and the energy can be used to do work I think this will come in to play in the future weeks

Jake Gordon 1A

extensive properties matter how much of the substance there is intensive properties are the same for a substance regardless of quantity heat capacity is the energy needed to raise the temperature of a substance 1 degree celcius (extensive) specific heat capacity is the energy needed to raise one gra...

Jake Gordon 1A

As another way to look at it, there are 4 types of energies in compounds: vibrational energy(how much the atoms or molecules vibrate), translational energy(energy from heat), rotational energy(how free the molecule is to rotate in space), and positional energy(the location of each atom in relation t...

Jake Gordon 1A

The units for the small constant given above are atm L per mol K and the other constant is J per mol K, since the mol K in the denominator is consistent, it depends on whether you are using pressure and volume( atm and L) or energy (J or kJ) in the overall mathematic expression.

Jake Gordon 1A

The delta T is essentially 0 because of the heat resevoir. When we talk about isothermal reversible expansion, isothermal refers to a constant "same" temperature even though as stated above their is a slight change in temp that is quickly replaced by the surroundings.

Jake Gordon 1A

Open systems can have mass and heat change with the surroundings. For an engine I think they are talking about fuel and air entering the body of the system and exhaust being released.

Jake Gordon 1A

Enthalpy is a thermodynamical change. The difference is that enthalpy is in relation to a set point therefore it is expressed as the change in heat whereas thermodynamics is just the overarching term for transfer of heat in science. Enthalpy is the heat of a system and delta H is the change in this ...

Jake Gordon 1A

I think his main idea was that every time the atmospheric pressure pushing down on the system is decreased by a tiny amount, there will be work done by the system. If we do this multiple times, we can get an accurate representation of how much work the system is doing in the long term. I think his p...

Jake Gordon 1A

The equilibrium will shift to the side of the equation where there are less moles of gas if the pressure is increased by decreasing volume. If an inert gas is pumped in, the reaction will neither favor forward nor backward. The reason the pressure change moves the equation to one side is because Con...

Jake Gordon 1A

It depends if the reaction is endothermic or exothermic. If it is endothermic and heat is added, the reaction will move in the forward direction. If the reaction is exothermic it will do the reverse. Also, these reactions have reverse reactions. If one way is endothermic the other way will be exothe...

Jake Gordon 1A

I agree with the person above, also Cl by itself doesn't affect pH. The only time it could be part of a dissociation that changes pH would be something like HClO, but even this is because of the hydrogen not the chlorine. For NH4Cl we are focused on NH4 + dissociating into H3O+ and NH3 the Cl doesn'...

Jake Gordon 1A

Aq means that the substance is dissolved in water, this can still be used for Kc and Qc but since it is aqueous it can not be used in Kp or Qp

Just a reminder that Liquids (pure water) and solids are omitted from all K and Q calculations

Jake Gordon 1A

Well, it depends how the volume has been changed. Lets say that the volume is halved, this doubles pressure because they are inversely related. for N2+ 3H2 ==> 2NH3 If the partial pressures at equilibrium are all .1, the K value is 100 When the volume halves, the concentration doubles because C=numb...

Jake Gordon 1A

This would mean that the reaction is already at equilibrium and the concentrations of the products and the reactants are unchanging even though movement in each direction may still occur. At this point Q would not even exist and we would call it K. It's just a notation technicality but at a given te...

Jake Gordon 1A

I agree with the students that brackets is the most proper way to indicate concentration. Also it can be useful to use parenthesis after the numbers have been substituted in in order to avoid confusion. An example would be [O3]^2 / [O2]^3 when the numbers are inputted (.1)^2 / (.2)^3 It is not neces...

Jake Gordon 1A

I agree that the p or c denotes what unit is being used and that liquids and solids must be omitted, but I believe you can use partial pressure or concentration for gases. Using the ideal gas law, we can convert partial pressure to concentration by calculating concentration=P over R times T since th...

Jake Gordon 1A

Spontaneous can also be described as thermodynamically favorable, as stated above this occurs without external interference. If I remember correctly spontaneous conditions are exothermic and have positive change in entropy.

Jake Gordon 1A

Cisplatin is the example from class. It must be cis because that means the two chlorine atoms are on the same side and they can each be replaced with water and will bond to a N with a lone pair on a guanine base. At a region of two close Guanine bases both chlorines can be replaced with water and wi...

Jake Gordon 1A

Bond length is shortest for a triple bond, middle for a double bond, and longest for a single bond. For single bonds, the example HF,HCl,HBr,HI helps further explain bond length. As you move down the halogen family there are more electrons and a larger atomic radius causing more distance between the...

Jake Gordon 1A

In the ring shaped structure there are not enough hydrogens to give those two carbons another atom attachment. Therefore there are only 2 regions of electron density around those two carbons (electron density doesn't care if it's a single double or triple bond) with only 2 electron density regions t...

Jake Gordon 1A

Any time you have a pi bond (double or triple bond) you will need one of the p orbitals to remain unhybridized. For carbon the configuration is 1s2 2s2 2p2 for 3 regions of electron density we will make an 2sp2 hybridization. This uses the s orbital and 2 p orbitals leaving one p orbital. 2s and 2p ...

Jake Gordon 1A

I don't think it's typically necessary. I think the book did so to drill home the point that in one structure 2 carbons are single bonded and 2 are double bonded and then it is flipped in the second. I know they also number carbons when drawing glucose so it might be more common in larger, repetitiv...

Jake Gordon 1A

I believe Be is linear between the carbons and each carbon has 3 hydrogens in a tetrahedral arrangement. The formal charge should work out to be 0. Tetrahedral has a bond angle of 109.5 and linear is 180

HHH-C-Be-C-HHH

Jake Gordon 1A

Bond order is simply just the stability of a bond and is quantified as the number of bonds between two atoms. EX. F-F bond order = 1 O=O bond order = 2 N=-N bond order = 3 For average bond order would be all bond orders in one structure added up divided by the # of bonding regions Ex NO3- (resonance...

Jake Gordon 1A

I would say that the ball and stick model is a simplified version of molecules used to display the geometry in 3d space. The shape of the molecule and therefore the arrangement of the atoms around the central atom will change according to the VSEPR theory to create the maximum distance for electron ...

Jake Gordon 1A

No, as far as we have been taught, bond angles are contingent on the molecular geometry. Whether or not one of the bonds is a single, double, triple, or resonance blend, it will still count only as one X atom stemming from the central A atom. BF3 and SO3 have the same bond angles 120 due to trigonal...

Jake Gordon 1A

Building off of the previous answer, the dipole moment in water is so strong that the hydrogen of one water molecule and the oxygen of another can form a hydrogen bond. These hydrogen bonds allow water to have its special properties such as capillary action, high surface tension, and ability to be a...

Jake Gordon 1A

Dipoles are regions of partial negative and partial positive within a molecule. They are determined by differences in electronegativity. Unless the two atoms interacting are identical there will be a small dipole but the difference in electronegativity calculation will tell whether the element is po...

Jake Gordon 1A

As stated above they are also called dispersion LDF VDW and others. They occur in all molecules and are the weakest Inter molecular force They occur because at any given moment there is a possibility that the electron density is higher on one side of the molecule than another and this creates a tiny...

Jake Gordon 1A

Equations using the speed of light are only applicable to electromagnetic radiation (photons) they lack rest mass and therefore do not work for the debroglie relation

On the other hand, everything with rest mass can not be related by using the speed of light and the debroglie relation must be used

Jake Gordon 1A

I believe 10^-18 m is the shortest observable with current technology

Jake Gordon 1A

To the best of my understanding Bond length has to be determined experimentally and can vary depending on which atoms are interacting In terms of decreasing strength it would be triple bond, double bond, single bond In terms of decreasing length it would be single bond, double bond, triple bond In r...

Jake Gordon 1A

The second ionization energy occurs after one electron has been removed. Assuming the element is neutral at first, taking away an electron will make a cation and leave the same number of positive protons with one less negative electron. Electrostatic attraction increases the pull of the electrons to...

Jake Gordon 1A

Due to electrostatic repulsion the positive cations will repel each other and this is the least likely to occur on a molecular level.

Jake Gordon 1A

The central atom is the least electronegative(lowest ionization energy also works), h is not central, c is almost always central if present Once the central atom is selected arrange the remaining elements around symmetrically making sure to be mindful of number of electrons, formal charge, and reson...

Jake Gordon 1A

The "l" quantum number distinguishes the sub shell (0=s 1=p 2=d 3=f) Each sub shell has a set number of orbitals which I like to think about visually but they also increase by two each sub shell s has 1 p has 3 d has 5 f has 7 and these are all denoted by the 3rd quantum number which range...

Jake Gordon 1A

The 2d and 4g subshells can not exist for the following reasons The d sub shell requires the angular momentum quantum number to be two. The highest value this number can be is the energy level (2 in this case) minus one. Therefore 2d is impossible 4g can not exist for the same reason: g requires the...

Jake Gordon 1A

h bar is equivalent to h/2pi so...hbar/2 is equivalent to h over 4pi which is what the right side of the Heisenberg equation requires.

Jake Gordon 1A

In chemistry, h is typically used to denote Planck's constant. It is a very small value equivalent to 6.626 times 10 to the -34 th power m^2 kg/s.

Jake Gordon 1A

An angstrom(Å) is a non- SI unit equal to 10 to the -10th meters. This is a valuable unit because it is around the value of wavelengths of light and interatomic distances (ex. diameter of a hydrogen atom).

Jake Gordon 1A

The Rydberg constant (3.29 times 10 to the 15th hz) is used in the equation that can give the energy of a hydrogen electron. E equals -h times R over n squared where n is the energy level. Remember this equation only works for Hydrogen atoms.

Jake Gordon 1A

Gamma rays have the most energy because their frequency is highest. Frequency and energy are directly proportional. Higher frequency means higher energy. Wavelength and Frequency are inversely proportional (this also makes sense if you draw it out, longer distance between crests means less space for...

Jake Gordon 1A

This is extremely difficult because our eyes and brains are not innately made to understand properties at the quantum level. The dual nature of light is what you are referring to. This means that light behaves as a particle and a wave. The wave is typically easier to comprehend as the crests and tro...

Jake Gordon 1A

Wavelength is the distance from one crest of the wave to the next. If you think of it like a sinusoid graph, it is like 1 period. The frequency is how often this period occurs. The more often a wave occurs the more energy it has. Wavelength and frequency are inversely proportional. In addition, freq...

Jake Gordon 1A

To the best of my knowledge unless it is an ion(charged particle), the net charge on each individual compound will be 0. These numbers will be pre-set based on the given compounds. The only thing that needs to be altered is the coefficients. For example H20 will always be H20 you can't change the ch...

Jake Gordon 1A

I was taught to visualize the United States If the decimal is present in this number start on the pacific side P. If it is absent, start on the Atlantic side A. Then from the first non zero digit underline all other digits in that direction. These are the significant figures. When adding and subtrac...

Jake Gordon 1A

To convert, you must first convert to Celsius.
Fahrenheit to Celsius is (F-32) multiplied by 5/9
Celcius to Kelvin is C plus 273.15

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