CHEMISTRY COMMUNITY

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the units for rate will always be M/s while rate constant can be M/w (0 order), 1/s (first order), or 1/Ms (second order)

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it helps if you look at the graph for the reaction profile. a catalyst would lower the activation energy for the whole graph so the new forward pathway and new reverse pathway look the same and both are at a lower Ea than before.

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for (g) zeroth order, the half life against [A] can be written as function t = [A]/2k where 1/2k would be the slope between the two variables. I think we are assuming that [A] would be essentially the initial concentration for (h) second order, the half life against [A] can be written as function t ...

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this method would be useful in the situation where the slow step rate law (which we assume to determine the overall rate law) includes an intermediate. Since we do not want intermediates in the overall rate law, we can use the pre-equilibrium approach to substitute out the intermediate

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the answer should be ClO- + I- --> IO- + Cl-
what answer are you referring to?

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I think the problem should be
reaction of chlorine in water:
Cl2(g) --> HClO(aq) + 2Cl-

because that is the only way Cl can be reduced and oxidized

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i'm pretty sure you would have to calculate Ecell in order to know

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the balanced reduction reaction is missing a 6e- on the left side in order to balance the charges. so the oxidation reaction is multiplied by 3 so that the 2e- can balance with the 6e- from the reduction

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usually the compartment with the lower concentration is the anode. This is because the lower concentration compartment would want more ions and in order to get more ions, it would have to donate electrons and oxidize the metal (Ni(s) --> Ni2+)

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To find the cell potential using Nernst Equation, you will need to first find the standard cell potential for that system by writing out the half reactions of the anode and cathode and calculating from the appendix of standard reduction potentials. You will also need the value of reaction quotient Q...

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P4 ---> PH3 balance P: P4 ---> 4PH3 balance H: 12H2O + P4 ---> 4PH3 + 12OH- balance charge: 12 H2O + P4 + 12e- ---> 4PH3 + 12OH- the H2O and OH- are added at the same time to balance H. because the left side needed 12 H, you can add 12 H2O and 12 OH- on the opposite side to balance the H.

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Can someone explain the steps to take in writing the half reactions for cell diagram Pt(s)|O2(g)|H+(aq)||OH-(aq)|O2(g)|Pt(s) ?
What do you do when the two substances in anode or cathode are not the same? How do you go about this?

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this redox reaction in acidic solution is Cl2 --> HClO + Cl2 where Cl2 is reducing and oxidizing agent. Is the reaction suppose to be Cl2 --> HClO + Cl- ?

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I believe it is Focus 5G.3, 5G.4, 5J.3 so problems 5G: 13, 15, 17, 19, 21; 5J: 11, 13, 15; and 5.55, 5.61

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in redox reactions, we usually always assume that Oxygen will have an oxidation number of 2-. using this information, you can then calculate the oxidation numbers of other elements in the same compound. for example Cr2O7(2-) has 7 oxygens which means 14 negative charges. since the overall charge is ...

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The way i think of it is that the drug has a pKa of 10.89 and the "solution" it's in is pH 1.7 which is more acidic that the drug itself. because of that the drug will less likely give off protons and will act more like a base in the acidic surroundings.

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yes exactly, because NH4Cl is in a solution, it will dissociate into NH4+ and Cl- and NH4+ acts as an acid

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in the question, it states that the reaction is exothermic so if the temperature increases, the reverse reaction would be favored and K will decrease.

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if the change in gibbs free energy is positive, it does not necessarily mean that delta H (enthalpy) is positive or negative because it also takes into account temperature and entropy. a reaction is endothermic if delta H is positive and exothermic if delta H is negative.

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if Gibbs free energy of the products is greater than that of the reactants, then for the forward reaction, there is an increase in free energy and delta G would be positive, implying that this forward reaction is unspontaneous

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hm i calculated the entropy change for each step too but when i added it together it was pretty close to 0. I think it should still be the same result (change in S = 0) so maybe it was just a small calculation error.

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i think constant temperature does not necessarily mean that internal energy is 0, for example, phase changes have an input of heat (q) but still stay at constant temperatures.

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how do you calculate the enthalpy at constant volume?

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two questions
does an isothermal reaction necessarily mean it is reversible?
and separately, does an isolated system necessarily mean the volume is constant?

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is an isolated system neccessarily q=0 and w=0?

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for the entropy change of a phase change, we use the fact that q(reversible)/T is the same as (change in enthalpy)/T. Why can we assume that q(reversible) = change in enthalpy of phase change? I thought that q at constant P = change in enthalpy but reversible reactions do not have a constant pressur...

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In the lecture, Professor Lavelle mentioned a graph to visually look at irreversible and reversible pathways. I think he mentioned that temperature is constant along the reversible and temperature changes along the irreversible. Why is this the case?

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you can assume they are equal when the pressure is constant. im not completely sure why but i think by definition, enthalpy is the change in heat at constant pressure

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using the standard enthalpy of formation for NO, and knowing that the standard enthalpy of formation for O2 is 0, you can first find the standard enthalpy of formation of NO2 by also taking into account the enthalpy change of the reaction. using this new found NO2 standard enthalpy of formation, you...

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i think it is deltaG = standard G + RTlnQ

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why is the Cp of constant pressure 5/2 times the ideal gas constant? and why is Cv of constant volume 3/2 of the ideal gas constant? like why do we know that

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you can check if your approximation was valid by calculating the percent deprotonation and seeing if it is less than 5%

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it was week 3 in young hall 3034

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Ka is the acid dissociation constant and Kb is the base dissociation constant.

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an exothermic reaction will release heat which will raise the temperature of the surroundings and an endothermic reaction will therefore do the opposite

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yes i believe it is the same delta H used in gibbs free energy.

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when you add H2O to the reaction 6CO2 + 6 H2O (l) <--> C6H12O6 + 6O2, since it is a liquid, it technically doesn't affect the reaction so there will be no shift. but would it change the concentrations of the other molecules if they were (aq) instead of (g)?

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when we're considering sigfigs, should we include the equilibrium constant sig figs as well even though it is a constant?

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when calculating the H+ concentration of a polyprotic acid (ex: H2SO4) would you calculate the H+ concentration of each separate reaction and then add it together or would you treat as one system and write the second equation based on the results of the first one?

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I know that when K is less than 10^-3 it is considered to be insignificant to the initial concentration but how would you determine whether Ka2 is negligible compared to Ka1?

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I think it would be the equilibrium concentration since the final concentration of H3O+ is used to calculate pH

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because the autoprotolysis reaction is when H2O donates a proton to another H2O molecule. To form H3O+ requires H2O to lose a proton and become OH-

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Do you mean (1.0x10^-14)/3.1? Because I'm not sure where you got the 3.2x10^-14

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for part b, you want to use the concentration of the original solution (answer to part aii) which is the concentration of OH- of the original solution. Using this information, you can use the OH- concentration to find the mols of OH- in that 200mL solution. using the mols of OH-, you can convert it ...

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In order to find the original solution's concentration of OH-, use the diluted concentration that you found in part ai) and find how many mols of OH- are really in the diluted solution. Then use this number of mols of OH- and divide it by 5.00mL to find the original concentration. This works because...

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you can think of liquids as solvents like H2O. molecules of a solvent can technically react but the vast majority of the solvent will stay a solvent which means there is no significant change in concentration. since there is not significant change, including the concentration of liquid would just ca...

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for 5.35, there is a graph with compounds A, B, and C and you are asked to write a balanced equation for the reaction. How would you know the stoichiometric coefficients of A, B, C? Thanks!

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In equilibrium, forward and reverse reactions are always occurring. There is always reactants changing into products and products changing into reactants. Equilibrium just says that these forward and reverse reactions are at the same rate!

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yes you would have to convert mass to moles and then convert to mol/L

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I did exactly what you did but I got 0.000416? Maybe just a calculation error because it should work

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because F is so electronegative, it pulls electrons harder and the bond between H and F is stronger and so HF doesn't lose protons (H+) as easily.

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Because Cl- is a stable ion. When HCl dissociates, Cl- is a stable anion and a really weak conjugate base to the strong acid.

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for CO3(2-) our TA mentioned that it is polydentate and can be either monodentate or bidentate because of the resonance structure but I'm still confused about how exactly it can be both. can someone explain a little more about how you can tell

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most amphoteric oxides align with the metalloid diagonal. For example c and d are amphoteric because As and Bi are metalloids

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hi how do we know how many sigfigs to use with calculated pH

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what do we need to know about the structure and biological function of vitamin b12?

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is there anything else we need to know about cisplatin other than the fact that it binds with DNA to block DNA replication. does anyone know the more details to this biological example

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yes for example in NH3, there are 3 bonds and one pair of lone electrons. This means NH3 will have 4 hybridized sp3 orbitals. one of the sp3 orbitals will have two paired electrons (which represent the lone pair) and the other 3 sp3 hybrid orbitals will have one unpaired electron in each (representi...

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if you think about it like sp2 is 33% s and 66% p and sp3 is 25% s and 75% p, then it makes more sense than an increase in s character means a decrease in p orbitals and the bond angles increase since there are less regions of electron density

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hydroxide would be OH

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what do we look for to determine if a dipole dipole is stronger than another dipole dipole force

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I understand why CHI3 has strong dipole dipole forces because Iodide is large and has more electrons making it more polarizable. Why does CHF3 not make hydrogen bonds even though it has lone pairs on F that can bond with H from another CHF3 molecule?

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when the s character of a hybrid increases, the bond angle also increases inbetween the orbitals but why?

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In Dr. Lavelle's lecture he mentioned that AX4E is a seesaw because the lone pair will be on the equatorial plane and affect the two axial atoms and be more stable since the other option is having an axial lone pair that affects all three atoms on the equatorial plane. My question is wouldn't the eq...

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How do we know if the H attached to the C in CH2Cl2 will be opposite to each other or opposite to a Cl atom? Does it matter which one you choose or is one better than the other?

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how do you know what number is in front of the hybridization numbers and when the question will ask for it versus just the hybrid orbital? for example the 2 in 2sp

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for hybridization we would usually look at the number of regions of electron density around the central atom and since C would have two regions of electron density (since a triple bond is considered one region) the hybridization would be sp

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He didn't talk about it in lecture but I think the T shape is when you have a central atom with 3 bonds and two lone pairs for example ClF3

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I don't think it's not completely necessary but it does help you categorize the different VSEPR shapes into number of bond electrons and lone electrons.

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Pi bonds are formed by having a flat bond above or below the sigma bond, this pi bond is only stable in one orientation and if there is any rotation then this bond breaks

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well i think for intermolecular forces we look at size because the larger atom means a bigger electron density which results in an easily distortable electron cloud. This leads to stronger dipole moments and stronger intermolecular forces. But for electronegativity, i think it plays more of a role i...

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I think it does? Because the OH at the end has lone pairs and hydrogens will form H bonds with it right

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from most polar to least polar, the answer is MG-O, C-O, B-O, O-O but im confused on why C-O is considered more polar than B-O?

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for chloric acid (HClO3) how would we know that the hydrogen is attached to the oxygen rather than the central atom chlorine in lewis structures?

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use the equation (uncertainty of momentum)(uncertainty of position) >= h/4pi
your uncertainty in position would be (5m)*2 = 10 m
the uncertainty of momentum can also be written as
uncertainty of momentum = mass * uncertainty of velocity

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no because Nitrogen in that case would have exceeded the octet rule

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can someone explain why the lewis structure of so3 would have one double bond and two single bonds rather than just three double bonds? why is one better than the other?

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how can we tell which molecules will have a greater dipole-dipole or London force? aka what factors contribute to the strength of dipole-dipole interactions?

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for part C (which has higher melting point: CHI3 vs CHF3) wouldn't CHF3 have a higher melting point because of its possible hydrogen bonds?

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how can one tell if a molecule will have certain intermolecular interactions (specifically how can you tell if it has dipole-dipole attractions)

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Br shares electrons with 3 F and has two lone pairs of its own because it exceeds the octet rule

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does anyone know if this week's homework is on the quantum stuff still or the chemical bonds or both

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You can also think of it like once you remove the first electron, there are less total electrons which means less electron electron repulsion so the positive nuclear charge pulls harder on the remaining electrons

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i think diffraction patterns are a result of waves interacting with each other

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the v in c= λv represents the frequency not velocity

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the photoelectric experiments basically told us that energy is related to frequency so E = hv shows us this relationship. the work function and kinetic energy were parts of the photoelectric effect but they do not show us the relationship between E and frequency

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because increasing the intensity is equivalent to increasing the number of photons but it doesn't change the energy each photon has. the energy each photon contains is what ejects the electron

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+1/2 is spin up and +1/2 is spin down

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well i think n is the shell number which is equivalent to how many energy levels an atom has so 6D would have n = 6 . since it is a d orbital, l = 2 i believe

l = 0; s orbital
l = 1; p orbital
l = 2; d orbital

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we only want the possible variance of the velocity. it does seem like it should be twice the number to cover the range but it's just suppose to be the +/- value, not sure why

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haha okay well then the indeterminacy would be just the ± 5.00 because that's what the measured amount is varied by? idk. i see what your saying but i think this is just how it is

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+1/2 refers to spin up and -1/2 refers to spin down because an electron can either be spin up or spin down. don't know how it would be determined tho

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do you mean the indeterminacy of velocity instead of the change in velocity?

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if you derived En(final) - En(initial) it would do the same thing as the Rydberg equation since En = -hR/n^2. so technically you can do either and still get the same result!

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I think you only use it for the wavelength of particles with momentum. if you wanted to solve the wavelength of light, this equation would require you to know the momentum. the wavelength of light can be found by using c = wavelength*frequency instead.

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I think the answer was the more precisely the position is determined, the less precisely the momentum is known and vise versa bc they are inversely related to each other

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3.607 x 10^-19 J would be the threshold energy, the energy required to remove an electron use the known formulas E = hv and c=wavelength*v and rearrange them so it looks like E = hc/wavelength ---> wavelength = hc/E you can then get the wavelength with planks constant, speed of light constant, and t...

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You can use the formula

frequency = -R((1/(n1^2)) - (1/(n2^2))

where R is rydberg's constant, n1 would be 2 and n2 would be 1 for that electron transition

and then you can use that frequency to find the wavelength

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Use the molar mass of magnesium sulfate heptahydrate to find the mols of the compound and multiply by 11 (11 oxygen mols per mol of magnesium sulfate heptahydrate) and then multiply by avogadro's constant to get the number of oxygen atoms in the sample!

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The Na is left out of the net ionic equation (Cu^2+ + 2OH- --> Cu(OH)2) but the hydroxide part of the molecule is what is included in the product.

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