CHEMISTRY COMMUNITY

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Thank you! That helped a lot :)

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Hi can someone explain to me the difference between the average rate of a reaction and the rate laws? when should I use each equation?

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If you're not part of the solution,

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You're part of the precipitate.

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So, if we are using the reduction electrode potentials, we do not change the sign when we imput the voltages into the equation?

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okay, thanks, also, what is the difference between standard molar entropies and statistical entropies?

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But, I know it might not be asked on the exam, Im just wondering, how do we determine the number of arrangements? for example CO can be arranged as CO and OC, but it can also be vertically arranged with O on top and C in the bottom and vice versa. What about the z plane? and all of the other planes?

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Okay, I get that conceptually, but how do we calculate them? Do we measure them experimentally or?

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I am confused, what are standard molar entropies and what do we use them for?

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I understand W = number of arrangements ^number of atoms, but how do we determine the number of arrangements?

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Also, take in mind that if T is increasing, there will be a change in P or V to make up for it, given that PV = nRT.

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Use Cv when the volume is constant and Cp when the pressure is constant.

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I believe the term "ideal" is used to describe gases, not systems. Ideal gases are those in which the forces of attraction between the molecules are negligible, and the molecules occupy a very small fraction of the space (taken to be as zero). You must know a gas is ideal before getting in...

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Sorry! Yes, absolutely, I meant Irreversible expansion.

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When in doubt, it is always best to convert the temperature to Kelvin by adding 273.15.

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It depends in the situation. If the volume is constant, ΔV = 0 so w = 0. If the pressure is constant, w = -P(ext)ΔV. If you have an isothermal reversible expansion (both pressure and volume change by infinitely small amount), w = -nRTln(V2/V1). I hope that helps?

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Yes! absolutely. If the system expands fast, and the energy lost by work is replaced by heat, you can have an isothermal reversible expansion. Take in mind that, reversible expansion will do more work overall however (the area under the curve is larger).

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There are two different equations. The first one, ΔH = mCΔT is found using the specific heat capacity of the substance, and m stands for the mass of the substance in grams. The second one, ΔH = nCΔT is found using the molar heat capacity of the substance, and n stands for the number of mol of the su...

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This was helpful, thanks!

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I dont understand why enthalpy is defined as ΔH = ΔU + PΔV. Can someone please explain where this equation came from to me?

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Bond enthalpies refer to the energy required to break a specific bond. The values given for diatomic molecules are absolute values, while the values given for any other bond enthalpy are averages. The enthalpy of formation of a given substance represents the heat released or absorbed when one mol of...

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If you are referring to the equation q= nCmΔT, the molar heat capacity of the substance will tell you how many joules are necessary to increase the temperature of one mol of the substance by 1 degree Celsius or Kelvin. By substituting each value into this equation, you will get a ΔH in joules per mo...

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The internal energy of the system will not change, because no work or heat can be applied to the system, so there is no point in finding delta u. Delta U for this case will always equal 0.

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In relation to this question, why do more complex molecules tend to have a higher specific/molar heat capacity? What are other factors that affect how high is the heat capacity of a substance?

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I don't understand why the final answer is negative. Can someone explain it to me? thanks!

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Remember that the standard enthalpy of formation of any substance is the change in heat that takes place when one mol of such substance is formed from its constituent elements in their standard state. O2 (g) is formed from O2(g), so, to form one mol of O2 (g), one mole of O-O bonds need to be broken...

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Absolutely! If you have a molecule in which a double bond can exist in two different positions, the enthalpy of both bonds is affected by resonance. The bond enthalpy of each bond should be about 1.5 times the enthalpy of the single bond.

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A reaction enthalpy refers to the total heat emitted or absorbed by any chemical reaction at a constant pressure. The enthalpy of formation of a substance X refers to the change in heat that takes place when one mol of X is formed by its constituent elements in their standard states. In other words,...

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how do we know which of the four locations we should go to?

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Lone pairs count as an area of electron density in such way that, when hybrid orbitals are formed, each lone pain occupies one of these new orbitals. In H2O, the lone pairs each occupy one sp3 orbital. The two other sp3 orbitals form covalent bonds with the two hydrogens. This results in four sp3 or...

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Be careful not to mix up this constant with Ryderberg's constant. The use of the same letter for their abbreviation often leads to confusion.

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ICE tables allow you to find the equilibrium concentrations of any equilibrium reaction, using only the initial concentration of the reactants. They also help you to find Ka and Kb for weak acids and bases, which will allow you to determine their relative strengths.

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Dr Lavelle, Thank you for coming to class in a good mood everyday. Thank you for your patience and for the effort you put in giving us all possible tools for us to succeed in your class. Your explanations are simple and straightforward, you make difficult chemistry easy to understand. See you next q...

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A ligand is a molecule with a lone pair of electrons. It forms coordinate (dative) bonds with transition metal cations. If it only has one lone pair, it is called "monodentate", if it has more than one lone pair and can form more than one coordinate bond, it is called "polydentate&quo...

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Given that pi bonds form above and bellow the internuclear axis, they hold the atoms in place, making it impossible for them to rotate.

I also wanted to add that single bonds are sigma bonds, and triple and double bonds are pi bonds.

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Chelating complexes are, in oder words, polydentate ligands. The lone pairs that will form the coordinate bonds must be at the right distance from one another so that they can both bond to the TM cation. The Ideal distance is two atoms in between the lone pairs for linear complexes. However, in the ...

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EDTA is a hexadentate ligand, so it forms six coordinate bonds with Fe(III). Would that make the structure of the complex octahedral even when the six bonds formed are with the same ligand? Would the coordination number still be 6 even if iron is binding to one ligand?

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When I first read the textbook I was a bit confused as well with regards to what those equations meant and how they related to hybrid orbitals. After reading it a few times, I think the textbook uses those equations better explain how they derive a hybridized molecule. The signs of each of the orbi...

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Water has four regions of electron density, so it should have 4 sp^3 orbitals. Can oxygen's lone pairs of electrons occupy two sp^3 orbitals, or do they make oxygen have a different type of hybridization? Is there a different rule for hybridization of central atoms with lone pairs?

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In the textbook, hybrid orbitals are described as a linear mix of atomic orbitals, as given by the following formulas
h1 =s +px +py +pz, h2= s -px -py +pz, h3= s -px +py -pz, but I don't understand what the formulas tell us, can someone explain them to me? Thank you!

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Is there any way to find out what the magnitude of a dipole moment is?

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The general trend for electronegativity is that it decreases down the group and increases across the period. The elements in the p block (except the noble gasses) tend to have high values of electronegativity because they want to gain electrons to become isoelectronic with a noble gas. On the other ...

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Hi! I dont understand why is it more favorable for electrons in the same orbital to have oposite spins. Does it lower the orbital's potential energy?

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Hello! I was wondering what type of questions we might get in which we will have to use this equation? Also, should we know how to apply this formula for next week's test?

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Hi! I have a question, does the wave function work as a visual representation of what atomic orbitals look like? In other words, do atomic orbitals look like their respective wave functions?

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Cr and Cu are exceptions because they are more 'stable' with a 4s^1 configuration, this makes me wonder, is there any way we can measure or investigate stability experimentally?

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Taking in mind that at n= infinity the potential energy of the electron is zero, the potential energy of the electron might be more negative as we approach the nucleus because the electron requires more energy to be released.

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In order to find E we need v, and in order to find v we need E for E=hv. So, how are either E or v experimentally determined?

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