CHEMISTRY COMMUNITY

Shivangi_2J

I belive it’s just one of them is more specific to 25 degrees Celsius (the second one)

Shivangi_2J

Delta h is the heat transferred at constant pressure

Shivangi_2J

I think because a catalyst speeds up the forward and back reaction to the same extent, adding a catalyst does not affect the relative rates of the two reactions

Shivangi_2J

under what conditions is delta U = 3/2 nRT ?

Shivangi_2J

do we need to know the steady state approach for the final?

Shivangi_2J

okay, I get now that the rate constants are different but the rates are the same...but doesn't the rate constant correspond to the rate of the reaction (larger rate constant --> faster rate of reaction)?

Shivangi_2J

I'm confused about how the forward and reverse rates of a reaction compare We know K = k1/k1prime aka K = forward rate constant/reverse rate constant So if K is large, the forward rate constant is larger which means the forward rate faster. BUT at equilibrium aren't the forward and reverse rates sup...

Shivangi_2J

oh got it, thank you!

Shivangi_2J

is the pre-equilibrium approach only valid when there a fast step followed by a slow step (fast, slow)? Are there any other cases in which we would use the pre-equilibrium approach?

Shivangi_2J

given the half-life, how do we calculate the time needed for a certain amount of the reactant's concentration to decrease using the half-life equation for example : (problem 15.35) The half-life for the second-order reaction of a substance A is 50.5 s when [A] 0 = 0.84 mol/L. Calculate the time need...

Shivangi_2J

Sarah Zhao 4C wrote:You can't multiply it by four but you can square it by four!
Break down the math:
1/2 x 4 = 2
vs
(1/2)^4 = 1/16

This doesn't give you the correct answer :( I think it's because, as someone said above, the half-life of a second-order reaction depends on how much reactant is left

Shivangi_2J

did you get the correct answer ( k = 2.85 x 10^12 L⁴mol^-4s^-1 ) when you did all your calculations in mmol and just converted to mol at the end?? because every time I do that I get the wrong answer (I keep getting k = 2.85 x 10^3

Shivangi_2J

the book's answer is in moles so you would have to divide your answer of k = 2.85 by 10^3 to get from mmol to mol. BUT that is still giving me the wrong answer because then I get k = 2.85 x 10^3 L⁴*mol^-4*s^-1, which still doesn't match the book's answer :(

Shivangi_2J

are rate of formation and the unique rate the same thing?

Shivangi_2J

when is deltaG equal to zero
and when is deltaG standard equal to zero

Shivangi_2J

when writing cell diagrams in which both species at the anode or cathode are aqueous solutions, does the order in which we write the aqueous solutions matter? For example in the reduction reaction Ce4+ + e- --> Ce3+ does: [anode] || Ce4+, Ce3+ | Pt mean somethingdifferent than: [anode] || Ce3+, Ce3+...

Shivangi_2J

when writing cell diagrams in which both species at the anode or cathode are aqueous solutions, does the order in which we write the aqueous solutions matter? For example in the reduction reaction Ce4+ + e- --> Ce3+ does: [anode] || Ce4+, Ce3+ | Pt mean somethingdifferent than: [anode] || Ce3+, Ce3+...

Shivangi_2J

on electrochem worksheet #8d, does it matter if on the cell diagram NO is listed first or NO3 is listed first? Or can the order of these two be reversed and the diagram still denotes the same reaction

Shivangi_2J

under what conditions is delta S total or delta S of the universe equal to 0?

Shivangi_2J

For question 6 on worksheet 4, how exactly are we supposed to determine which volume we use to find the pressure for the work component of the internal energy change? To my understanding, the pressure was calculated using PV = nRT, with V = 998L, n = 31.9 mol, R = 0.08206 L * atm / mol * K, T = 311...

Shivangi_2J

will all of outline 4 be on the midterm? (including Gibbs Free Energy and the little part of Chapter 11 that is listed on the 6th edition outline) Or are will it be only up to section 9.11 in the sixth edition?

Shivangi_2J

when calculating the heat released by a gas at constant pressure or volume, can we always assume it is an ideal gas unless specifically stated otherwise? (so then we can use Cp = (5/2)R and Cv = (3/2)R)

Shivangi_2J

I don’t think this factors into our calculations, it seems more like a conceptual thing to understand about different systems

Shivangi_2J

Delta H is the change in enthalpy and delta U is the change in internal energy. Enthalpy is different from internal energy in that it is the amount of heat released or absorbed at a constant pressure. So enthalpy is a way of measuring a systems internal energy at a constant pressure. Delta H = delta...

Shivangi_2J

An open system can exchange both matter and energy with the surroundings. Examples of open systems are automobile engines and the human body. A closed system has a fixed amount of matter, but it can exchange energy with the surroundings. An example of a closed system is a cold pack used for treating...

Shivangi_2J

In a weak acid or base whose K is smaller than 10^-3, the amount of substance that dissociates is so small compared to the initial molarity that there isn't really a substantial difference between the initial and the initial minus the amount dissociated for example, we are saying because the amount ...

Shivangi_2J

Weak acids and bases do not fully dissociate as strong acids and bases do. Percentage protonation/deprotonation tells us how much of the acid or base has dissociated. Percentage protonation tells you the percent of a base that has dissociated. In other words, its the percent of the base that has acc...

Shivangi_2J

The concentration of solids and liquids essentially remains constant throughout the reaction so we don't include them in K or Q expressions.

Shivangi_2J

Catalysts only speed up the time it takes for the reaction to reach equilibrium, but it does not change the equilibrium position and it does not change K.

Shivangi_2J

no, solids and liquids are not included in Q for the same reasons they aren't included in K (their concentration does not change or changes so little it is insignificant). Ultimately, Q and K are both calculated in the exact same way, only the numbers themselves are different because in the case of ...

Shivangi_2J

what does it mean to say a reaction is spontaneous?

Shivangi_2J

Michelle Ramirez_4A wrote:Can someone explain why hemogrlobin is tetradentrate but cisplatin is monodentrate?

hemoglobin and cisplatin are not ligands, so they aren't any kind of "dentate." We only describe ligands as being bidentate, tridentate, etc.

Shivangi_2J

do lone pairs directly cause a dipole moment? or do they only affect the shape of the molecule which can affect the dipole moment?

Shivangi_2J

does the lewis structure of ClO2- have doubles bonds or only single bonds? because to minimize formal charge, there should be one double bond between one Cl and the O, but I've heard Cl doesn't form double bonds??

Shivangi_2J

also, the Lewis definition encompasses more compounds/is more general than the Bronsted and Arrhenius definitions

Shivangi_2J

the book also shows them written in reverse so I'm assuming that is the "correct" way to write them and that we'd have to write them like that on the test too

Shivangi_2J

I'm not sure to what extent we need to know it, but the syllabus outline says we need to know the biological significance of coordination compounds and the final covers the whole syllabus

Shivangi_2J

For all of the other VSEPR models, replacing an atom with a lone pair is done by taking away from the equatorial plane. But with the octahedral shape, an axial bond is replaced to form square pyramidal. Why is that so?

Shivangi_2J

H, He, Li, Be, and B can have less than an octet (an incomplete octet)
and any element in period 3 or below can have more than an octet (expanded octet) because they can use the empty d orbital, as mentioned above.

Shivangi_2J

When an electron is promoted it is relocated to a higher energy orbital. Although it takes energy to promote electron, it eventually results in bonding and a more stable molecule. (this is why promotion will only take place if the overall change is towards lower energy). Promotion happens in carbon ...

Shivangi_2J

you have to determine the shape of the molecule and look at whether or not the molecule has one side of the molecule that has a negative/positive dipole. A polar bond between two atoms creates a dipole moment in which one atom has a slightly more positive/negative charge. Depending on how these pola...

Shivangi_2J

What is the hybridization of the central atom in a molecule with trigonal pyramidal shape?

Shivangi_2J

does the central atom of a molecule with a tetrahedral shape always have sp3 hybridization?

Shivangi_2J

the shorter the bond, the stronger it is. And triple bonds are shorter than double bonds which are shorter than single bonds. (triple < double < single) And anything more than a single bond has at least one pi bond. (for example, a triple bond is 1 sigma and 2 pi bonds) So I guess you could say the ...

Shivangi_2J

only the lone pairs around the central atom affect the shape of the molecule (For example the lone pairs of chlorine on CCL4 would not affect the molecules shape)

Shivangi_2J

electron repulsion affects the overall shape of the molecule because it determines how far the bonds around the central atom are from each other. Lone pairs of electrons have stronger repulsion strength than bonding pairs .

Shivangi_2J

I think organic compounds are generally rod-shaped. Also, the way the formula is written generally gives you an idea of whether it is rod/sphere shaped. For example, in Lavelle's lecture, he mentioned the examples C4H10 and CH3CH2CH2CH3. These both have the same number of each atom but the latter is...

Shivangi_2J

the graphical representations are the probability distributions

Shivangi_2J

I believe it's representative of how strongly attracted two atoms are. it's affected by "r" (the distance between the atoms) because as the distance between them increases, they are less attracted to each other. And as the distance decreases, aka they are closer, they are more strongly att...

Shivangi_2J

you put one dot on the element that has the radical

Shivangi_2J

the negative formal charge usually is on the element that is most electronegative

Shivangi_2J

electronegativity is value that is calculated using the measured values of electron affinity and ionization energy. and electron affinity is the energy released when an electron is added to an atom and ionization energy is the energy required to remove an electron from an atom in its gaseous state T...

Shivangi_2J

electronegativity is value that is calculated using the measured values of electron affinity and ionization energy. and electron affinity is the energy released when an electron is added to an atom and ionization energy is the energy required to remove an electron from an atom in its gaseous state T...

Shivangi_2J

ohhh got it. thanks!

Shivangi_2J

Right thanks, but I meant in terms of writing the quantum numbers... wouldn't these two atoms have the same quantum numbers (n = 4, l = 0)

or do we write copper as : n= 3, l = 2, ml = +2

Shivangi_2J

I'm confused about how we would write the quantum numbers for something like Copper (Cu) whose electron configuration is [Ar] 3d^10 4s^1
How would we differentiate this quantum number from that of Potassium (K) whose electron configuration is [Ar] 4s^1

Shivangi_2J

an excited electron will be in a higher energy level than it "should"/would normally be in

Shivangi_2J

not every orbital has a p(), the magnetic quantum number tells you the orientation in a subshell (s,p,d,f). for p it is Px Py Pz. for d it is Dyz, Dxz, Dxy,
Dx^2-y^2, Dz^2

Shivangi_2J

yeah pretty much. Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers

Shivangi_2J

Can someone give me some examples of extensive and intensive properties that aren't in the notes?

Shivangi_2J

when the frequency of the wave decreases, the wavelength is longer so waves broaden (spread out) and the extent of the change (aka the slope of the wave) decreases

Shivangi_2J

One Hz is equivalent to one cycle per second

Shivangi_2J

The law of conservation of mass states that matter is neither created or destroyed (with the sole exception of nuclear reactions). So as long as we are dealing with chemical reactions, the mass on the reactants side before the reaction must be the same as the mass on the products side after the reac...

Shivangi_2J

I remember coming across this in the online module and the answer given as correct was: no, it is highly unlikely that 2 reactants are both present in limiting molar amounts.

Shivangi_2J

Instead of calculating each possible theoretical yield, you can also just calculate the moles of each given substance and compare it to the number of moles in the balanced equation. The substance with the smallest ratio of [moles you have/coefficient in the balanced chemical equation] is the limitin...

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