CHEMISTRY COMMUNITY

Jason_John_2F

catalyst will lower the activation energy of reverse

Jason_John_2F

a catalyst lowers activation energy in reverse

Jason_John_2F

catalysts are not consumed

Jason_John_2F

J/mol

Jason_John_2F

yes sapling explains that the rate of [A] is negative but the overall reaction should be expressed as positive

Jason_John_2F

This problem requires the Nernst equation

Jason_John_2F

E is zero when concentrations are the same.

Jason_John_2F

The equation with log assumes 25 Celsius

Jason_John_2F

the second one is used at 25celsisu

Jason_John_2F

k at equilibrium, q otherwise

Jason_John_2F

the E cell needs to be positive in order to do work and will stop working when it reaches 0

Jason_John_2F

the coefficient isn't used to calculate oxidation number but you have to keep in mind the coefficient for the overall charge of the equation

Jason_John_2F

solution of zinc on the left and copper on the right.

Jason_John_2F

the salt bridge helps balance the charges.

Jason_John_2F

you know from the minus sign at the end of MnO4- that overall the oxidation numbers should add up to -1 and since we know that O is -2 (*4=-8)we can tell that Mn is +7 since -8+7=-1 And since Mn2+ is has a charge of +2<+7 it decreases

Jason_John_2F

the rev is for reversible

Jason_John_2F

this is Boltzmann constant k =1.38064852 × 10-23 m2 kg s-2 K-1 on the equation sheet

Jason_John_2F

both are used depending on the problem but J/kis used commonly

Jason_John_2F

kb is Boltzmann constant which is on the equation sheet and is k= 1.38064852 × 10-23 m2 kg s-2 K-1 (says k but is the same)

Jason_John_2F

i think there is no difference

Jason_John_2F

to add on reversible expansions generally require more work

Jason_John_2F

reversible expansions require more work than irreversible

Jason_John_2F

positive means the work is done on the system and negative means by the system

Jason_John_2F

work is negative when the system is doing work because the energy is lost to the surrounding and work is positive when work is being done on the system because the system is gaining energy

Jason_John_2F

the difference between the two is that molar heat capacity is in terms of 1 mol and specific heat capacity is in terms of 1 grams

Jason_John_2F

i agree with the previous replies the mCΔT equations assumes constant pressure

Jason_John_2F

the conversion is K= 273 +C so if c goes up by say 5, the K will only increase by 5

Jason_John_2F

I think that we will be focussing mostly on heat in thermochemistry

Jason_John_2F

this means that heat given off by the reaction is = - heat absorbed by the solution or in other words there will be no loss of energy to the surroundings

Jason_John_2F

extensive properties are things that depend on the amount such as mass or volume which is why specific heat capacity which changes based on the amount of the substance is extensive

Jason_John_2F

i agree that steam coming from something like boiling water probably doesn't feel as hot when mixed in with the cool air around it but when steam is coming out of a tight space like the steam coming out of a rice cooker it is very hot

Jason_John_2F

i think the terms refer to the same thing in this class

Jason_John_2F

i agree, when stronger bonds are being broken they require more energy and when stronger bonds are being formed they release more energy

Jason_John_2F

yes you are correct the heat added goes to breaking bonds rather than temperature

Jason_John_2F

q is energy transfer while h(enthalpy) is total heat content or state of the system

Jason_John_2F

i think k needs to be under 10^-4

Jason_John_2F

leave out the h20 because it will not have much of an effect on calculations

Jason_John_2F

you can do it faster if you know that it is strong but doing an icebox every time will work regardless

Jason_John_2F

i think you can use mmol/ liter as long as you know the units that will come out but I think it benefits you to just use mol/liter to keep everything organized

Jason_John_2F

the process is the same as for calculating the concentration

Jason_John_2F

ideal gasses are just theoretical for simplicity and calculations as they don't have interparticle interactions

Jason_John_2F

apply the x to the final concentrations of both the product and reactants, the one that doesn't make either negative is the correct x

Jason_John_2F

apply the x to the final concentrations of both the product and reactants, the one that doesn't make either negative is the correct x

Jason_John_2F

we can change the n/v into concentration because the definition of molarity is just moles/liters so they are substitutable

Jason_John_2F

gas constant is given on the equation sheet as 8.3145 J mol^-1K^-1

Jason_John_2F

kp is used if it is calculated using partial pressure while kc is used if it is calculated using concentration

Jason_John_2F

yes the anion will have more than 1 hydrogen

Jason_John_2F

yep polyprotic just means they can accept or donate more than 1 h+

Jason_John_2F

acids are polyprotic when they donate more than 1 h+ :H2SO4, H2CO3, H3PO4

Jason_John_2F

hf is a weak acid due to its size the bond length is short and therefore stronger making it dissociate less in water

Jason_John_2F

also their conjugate base all accept more than 1 h+

Jason_John_2F

acids are stronger when they can easily dissociate in water and since br has a longer and weaker bond then it makes the stronger acid

Jason_John_2F

pka is the negative log of ka the acid dissociation constant, the lower the pka the stronger the acid

Jason_John_2F

en is the abbreviation for the ligand Ethylenediamine

Jason_John_2F

name the ligands first in alphabetical order then the metal

Jason_John_2F

strong acids need to dissociate easily in their solution so they will have weaker bonds than weak acids

Jason_John_2F

The [Fe(CN)6]-4 has a coordination number of 6 because it is octahedral shape with the Fe at the center meaning it has 6 bonds connecting to the central atom

Jason_John_2F

you are correct the charge goes outside the bracket

Jason_John_2F

Lavelle said he goes through all the sapling problems so I would assume that if it is on the sapling we need to know it

Jason_John_2F

double bonds count as 2 when finding coordination number

Jason_John_2F

A ligand is a lewis base or something that donates a lone pair in order to form a coordinate covalent bond with the center metal atom of a complex. The ligands themselves are not the central atom of the complex

Jason_John_2F

as said above sea saw shape is similar to trigonal bipyramidal except one atom is replaced with a lone pair making it 4 atoms and 1 lone pair

Jason_John_2F

lone pairs do count as their own region of electron density

Jason_John_2F

if the molecule has only 4 regions of electron densities around it it will be tetrahedral but if it has 6 regions of electron density (2 lone pairs) then it will be square planar

Jason_John_2F

i agree drawing your the molecular geometry using the dashed lines and wedges helps

Jason_John_2F

when the cl molecules are on opposite sides of the molecule the dipoles will cancel out which makes the molecule polar

Jason_John_2F

it is II because it is lined up so that the white and green atoms are closest to each other and therefore have the highest attraction

Jason_John_2F

the hydrogen bond acceptor does not need to be attached to a hydrogen

Jason_John_2F

it should say so2 not h2s

Jason_John_2F

s is below o on the periodic table meaning that the atomic radius is larger and therefore the bond length is larger

Jason_John_2F

bonds become weaker the longer they are

Jason_John_2F

i agree each atom in a molecule has its own formal charge

Jason_John_2F

formal charges are used to determine which lewis structure is most stable

Jason_John_2F

resonance structures are used because one lewis structure is not always good enough to represent a molecule

Jason_John_2F

oxidation number is the charge of specific atoms that make up the compound which shows how many electrons each atom has gained or lossed when forming bonds

Jason_John_2F

it is preferable to have more formal charges of zero because it means that the structure is more stable

Jason_John_2F

for what we are learning i think it is safe to keep l at 0-3

Jason_John_2F

since electrons are not found in the plane, they help create an outline to the shape of the orbital by showing where the electrons are allowed.

Jason_John_2F

basically the d subshell has 4 orbitals which follow the clover shape on the dxy, dxz, dyz , and dx^2-y^2 and 1 orbital on the dz^2 which looks like 2 lobes with a ring

Jason_John_2F

psi squared is proportional to the probability of finding a particle given by psi at a point and time

Jason_John_2F

nitrogen is more stable due to its half filled orbital meaning that oxygen wants to give away its electron to become more stable due to electron electron repulsion which is why its ionization energy is lower

Jason_John_2F

Brandon Le 3C wrote:What would we plug into for mass if we are only given the length of the E.coli bacterium (1.7 μm)?

if you are referring to the equation Ek = 1/2 mv^2 then we would use the mass of an electron 9.11x10^-31 kg

Jason_John_2F

You want to rearrange the equation to isolate the v which can be done simply by multiplying both sides by v and dividing both sides by λ to get v=h/mλ

Jason_John_2F

can confirm that wavelength less than 10^-15 m cannot be observed

Jason_John_2F

The equation E=pc shows how momentum p and energy E are related where c is the speed of light.

Jason_John_2F

Yes, put simply, De Broglie Equation is used on things with mass while Speed of Light is used on photons which are massless.

Jason_John_2F

h is planck's constant which is always 6.62607015×10−34 js and v is the frequency which is how often a wave passes a given point per second.

Jason_John_2F

E=hv and c=λv Basically if you need to find E but only have λ you can use λ to solve for v by rearranging the equation c=λv to c/λ=v then plugging that value of v into E=hv. If you want to make it quicker you can just replace the v with c/λ to get the equation you asked about.

Jason_John_2F

when determining mass protons and neutrons are almost the same and the weight of electrons is basically negligible

Jason_John_2F

I prefer to put the answer in nanometers since it just easier to read rather rather than reading it in meters way past the decimal.

Jason_John_2F

I believe that we will be given the constants and equations on the test however I think you will generally memorize them as you are learning and doing problems with them.

Jason_John_2F

Everything in the equation is a gas so you just need to find how many more moles were produced from the reactants(30) to the products(36). To do this we take the difference which is 36-30=6

Jason_John_2F

If you have the perfect ratio of reactants which matches the balanced equation then there will be no left over reactants and either reactant can be used to find the amount of product since they will both give you the same answer.

Jason_John_2F

When you are diluting with the equation m1v1 = m2v2 you can also use units like milliliters to solve the problem as long as you use it on both sides. If you are trying to solve for volume then putting in milliliters just gives you the answer in milliliters.

Jason_John_2F

For converting the moles to millimoles my hs chem teacher taught us to use King Henry Died Monday Drinking Chocolate Milk which makes the acronym KHDMDCM which also stands for kilo hecto deca (moles in this case but can be substituted for any unit) deci centi milli. Each movement right is a multipli...

Jason_John_2F

Follow-up question, I completely agree that in order to maintain accuracy we should wait until the final step to round. Let's say you were doing a multi-step problem with lots of calculations, would you agree that after each set of calculations it would be best to round to the correct number of sig...

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